Title: Camera system, camera and lens apparatus
Abstract: A camera system which controls the driving of a focus lens through overlap control with a high degree of accuracy, is disclosed. The camera system comprises a lens apparatus with an image-taking optical system and a camera on which the lens apparatus is mountable. The camera system comprises a focus detection unit detecting a focusing state of the image-taking optical system, a driving unit driving the focus lens unit, and a controller controlling the driving speed of the focus lens unit and controls the focus detection unit to perform a focus detection operation at least once while the focus lens unit is moved. The controller sets the driving speed of the focus lens unit at the time of at least a final focus detection operation while it is moved toward an in-focus position, to a speed decelerated from the driving speed before the final focus detection operation.
Patent Number: 6,892,028 Issued on 05/10/2005 to Kashiwaba, et al.
| Inventors:
|
Kashiwaba; Seiichi (Tochigi, JP);
Kawai; Toru (Kanagawa, JP);
Ishikawa; Masanori (Tokyo, JP);
Sato; Shigeki (Tochigi, JP)
|
| Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
938142 |
| Filed:
|
September 10, 2004 |
Foreign Application Priority Data
| Sep 20, 2002[JP] | 2002-276283 |
| Current U.S. Class: |
396/135; 348/345 |
| Intern'l Class: |
G03B 013/36 |
| Field of Search: |
396/133,135,136
348/345,357
|
References Cited [Referenced By]
U.S. Patent Documents
| 4764787 | Aug., 1988 | Hamada et al.
| |
| 4977457 | Dec., 1990 | Tamekuni et al.
| |
| 5444510 | Aug., 1995 | Okano et al.
| |
| Foreign Patent Documents |
| 04-010051 | Jan., 1992 | JP.
| |
Primary Examiner: Perkey; W. B.
Attorney, Agent or Firm: Morgan & Finnegan, LLP
Parent Case Text
This application is a continuation of U.S. application Ser. No. 10/664,752 filed
Sep. 18, 2003.
Claims
1. A camera system comprising a lens apparatus with an image-taking optical system
including a focus lens unit and a camera on which the lens apparatus is mountable,
the camera system comprising:
a focus detection unit which detects a focusing state of the image-taking optical
system; and
a controller which controls the driving speed of the focus lens unit and controls
the focus detection unit to perform a focus detection operation at least once while
the focus lens unit is moved,
wherein the controller drives the focus lens unit at a first speed and a second
speed lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller determines a position where deceleration of the focus lens unit
from the second speed is started based on the result of the final focus detection
operation.
2. A camera system comprising a lens apparatus with an image-taking optical system
including a focus lens unit and a camera on which the lens apparatus is mountable,
the camera system comprising:
a focus detection unit which detects a focusing state of the image-taking optical
system; and
a controller which controls the driving speed of the focus lens unit and controls
the focus detection unit to perform a focus detection operation at least once while
the focus lens unit is moved,
wherein the controller drives the focus lens unit at a first speed and a second
speed lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller obtains a remaining amount of movement to the in-focus position
based on the result of the final focus detection and drives the focus lens unit
according to the remaining amount of movement.
3. A camera system comprising a lens apparatus with an image-taking optical system
including a focus lens unit and a camera on which the lens apparatus is mountable,
the camera system comprising:
a focus detection unit which detects a focusing state of the image-taking optical
system; and
a controller which controls the driving speed of the focus lens unit and controls
the focus detection unit to perform a focus detection operation at least once while
the focus lens unit is moved,
wherein the controller drives the focus lens unit at a first speed and a second
speed lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller determines timing of deceleration from the first speed to the
second speed based on the first speed and the second speed.
4. A camera on which a lens apparatus is mountable, the lens apparatus comprising
an image-taking optical system which includes a focus lens unit, the camera comprising:
a communication unit which communicates with the lens apparatus;
a focus detection unit which detects a focusing state of the image-taking optical
system;
a controller which controls the driving speed of the focus lens unit by communications
with the lens apparatus via the communication unit and controls the focus detection
unit to perform a focus detection operation at least once while the focus lens
unit is moved; and
a photometric unit which measures brightness of an object,
wherein the controller drives the focus lens unit at a first speed and a second
speed lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller determines a position where deceleration of the focus lens unit
from the second speed is started based on the result of the final focus detection
operation.
5. A camera on which a lens apparatus is mountable, the lens apparatus comprising
an image-taking optical system which includes a focus lens unit, the camera comprising:
a communication unit which communicates with the lens apparatus;
a focus detection unit which detects a focusing state of the image-taking optical
system;
a controller which controls the driving speed of the focus lens unit by communications
with the lens apparatus via the communication unit and controls the focus detection
unit to perform a focus detection operation at least once while the focus lens
unit, is moved; and
a photometric unit which measures brightness of an object,
wherein the controller drives the focus lens unit at a first speed and a second
speed lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller obtains a remaining amount of movement to the in-focus position
based on the result of the final focus detection and drives the focus lens unit
according to the remaining amount of movement.
6. A camera on which a lens apparatus is mountable, the lens apparatus comprising
an image-taking optical system which includes a focus lens unit, the camera comprising:
a communication unit which communicates with the lens apparatus;
a focus detection unit which detects a focusing state of the image-taking optical
system;
a controller which controls the driving speed of the focus lens unit by communications
with the lens apparatus via the communication unit and controls the focus detection
unit to perform a focus detection operation at least once while the focus lens
unit is moved; and
a photometric unit which measures brightness of an object,
wherein the controller drives the focus lens unit at a first speed and a second
speed lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller determines timing of deceleration from the first speed to the
second speed based on the first speed and the second speed.
7. A camera comprising:
an image-taking optical system which includes a focus lens unit;
a focus detection unit which detects a focusing state of the image-taking optical
system;
a controller which controls the driving speed of the focus lens unit and controls
the focus detection unit to perform a focus detection operation at least once while
the focus lens unit is moved; and
a photometric unit which measures brightness of an object,
wherein the controller drives the focus lens unit at a first speed and a second
speed lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller determines a position where deceleration of the focus lens unit
from the second speed is started based on the result of the final focus detection
operation.
8. A camera comprising:
an image-taking optical system which includes a focus lens unit;
a focus detection unit which detects a focusing state of the image-taking optical
system;
a controller which controls the driving speed of the focus lens unit and controls
the focus detection unit to perform a focus detection operation at least once while
the focus lens unit is moved; and
a photometric unit which measures brightness of an object,
wherein the controller drives the focus lens unit at a first speed and a second
speed lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller obtains a remaining amount of movement to the in-focus position
based on the result of the final focus detection and drives the focus lens unit
according to the remaining amount of movement.
9. A camera comprising:
an image-taking optical system which includes a focus lens unit;
a focus detection unit which detects a focusing state of the image-taking optical
system;
a controller which controls the driving speed of the focus lens unit and controls
the focus detection unit to perform a focus detection operation at least once while
the focus lens unit is moved; and
a photometric unit which measures brightness of an object,
wherein the controller drives the focus lens unit at a first speed and a second
speed lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller determines timing of deceleration from the first speed to the
second speed based on the first speed and the second speed.
10. A lens apparatus which is mountable to a camera, comprising:
an image-taking optical system including a focus lens unit;
a controller which controls the driving speed of the focus lens unit; and
a memory which stores information on an amount of movement of a focal point of
the image-taking optical system with respect to an amount of movement of the focus
lens unit,
wherein the camera controls a focus detection unit to detect a focusing state
of the image-taking optical system at least once while the focus lens unit is moved,
the controller drives the focus lens unit at a first speed and a second speed
lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller determines a position where deceleration of the focus lens unit
from the second speed is started based on the result of the final focus detection
operation.
11. A lens apparatus which is mountable to a camera, comprising:
an image-taking optical system including a focus lens unit;
a controller which controls the driving speed of the focus lens unit; and
a memory which stores information on an amount of movement of a focal point of
the image-taking optical system with respect to an amount of movement of the focus
lens unit,
wherein the camera controls a focus detection unit to detect a focusing state
of the image-taking optical system at least once while the focus lens unit is moved,
the controller drives the focus lens unit at a first speed and a second speed
lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller obtains a remaining amount of movement to the in-focus position
based on the result of the final focus detection and drives the focus lens unit
according to the remaining amount of movement.
12. A lens apparatus which is mountable to a camera, comprising:
an image-taking optical system including a focus lens unit;
a controller which controls the driving speed of the focus lens unit; and
a memory which stores information on an amount of movement of a focal point of
the image-taking optical system with respect to an amount of movement of the focus
lens unit,
wherein the camera controls a focus detection unit to detect a focusing state
of the image-taking optical system at least once while the focus lens unit is moved,
the controller drives the focus lens unit at a first speed and a second speed
lower than the first speed while the focus lens unit is moved toward an in-focus
position,
the focus detection unit performs a final focus detection operation out of at
least one focus detection operation while the focus lens unit is driven at the
second speed, before the focus lens unit reaches the in-focus position, and
the controller determines timing of deceleration from the first speed to the
second speed based on the first speed and the second speed.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lens apparatus, camera system and camera provided
with an autofocusing function.
2. Description of the Related Art
There are many camera systems provided with an autofocusing (AF) function which
detects a focusing state of an image-taking optical system using a focus detection
sensor and moves a focus lens to an in-focus position using an actuator according
to the detected signal. There are also a variety of autofocusing systems.
For example, a camera system which performs an AF operation based on a TTL phase
difference detection system disclosed in Japanese Patent Publication No. H4 (1992)-10051,
repeatedly performs focus detections not only before starting the driving of the
focus lens but also during the driving of the focus lens, so-called overlap control,
in order to shorten the time required to reach an in-focus state and moves the
focus lens to the in-focus position while correcting the amount of driving of the
focus lens based on the result.
However, with the trend toward implementation of an image-pickup element
with a multitude of pixels and a smaller in size in a digital camera system in
recent years, there is a growing demand for an AF function with a higher degree
of accuracy and the above described AF has problems as shown below.
For example, in a system which corrects an amount of driving of the focus lens
while carrying out overlap control, what determines the accuracy of stopping at
an in-focus position finally is the final focus detection operation and correction
of the amount of driving of the focus lens which are carried out immediately before
the driving of the focus lens is completed. As the position of the focus lens at
this time becomes closer to the in-focus position, it is possible to reduce errors
in focus detection due to influences of aberration variations, etc., and calculation
errors in the amount of driving due to variations in focus sensitivity (amount
of movement of a focal point with respect to a unit amount of movement of the lens)
and thereby improve the accuracy.
According to the AF system disclosed in the above described Publication,
the focus detection operation during the driving of the focus lens is carried out
at constant intervals, and therefore the position of the focus lens when the focus
detection operation is carried out immediately before the driving is completed
changes according to the amount of driving of the focus lens based on the initial
focus detection operation, resulting in a problem that the accuracy of focus detection
and accuracy of calculations of the amount of driving of the lens are not stable.
Furthermore, in a recent camera system capable of faster driving of
the focus lens in order to reduce the focusing time, there are problems such as
deterioration of focus detection accuracy due to an image flow on a focus detection
sensor caused by the driving of the focus lens and deterioration of accuracy of
focus detection and accuracy of calculations of the mount of driving where the
focus detection operation immediately before the driving is completed is considerably
far from the in-focus position.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a camera system, camera and
lens apparatus capable of controlling the driving of a focus lens in an AF function
which carries out overlap control to an in-focus position with a high degree of accuracy.
In order to attain the above described object, one aspect of the camera system
of the present invention includes a camera system comprising a lens apparatus with
an image-taking optical system including a focus lens unit and a camera on which
the lens apparatus is mountable. The camera system comprises a focus detection
unit which detects a focusing state of the image-taking optical system, a driving
unit which drives the focus lens unit, and a controller which controls the driving
speed of the focus lens unit through the driving unit and controls the focus detection
unit to perform a focus detection operation at least once while the focus lens
unit is moved. The controller sets the driving speed of the focus lens unit at
the time of at least a final focus detection operation by the focus detection unit
while the focus lens is moved toward an in-focus position, to a speed decelerated
from the driving speed before the final focus detection operation.
One aspect of the camera of the present invention on which a lens apparatus is
mountable, the lens apparatus comprising an image-taking optical system which includes
a focus lens unit. The camera comprises a communication unit which communicates
with the lens apparatus, a focus detection unit which detects a focusing state
of the image-taking optical system, a driving unit which drives the focus lens
unit, and a controller which controls the driving speed of the focus lens unit
through the driving unit and through communications with the lens apparatus through
the communication unit and controls the focus detection unit to perform a focus
detection operation at least once while the focus lens unit is moved. The controller
sets the driving speed of the focus lens unit at the time of at least the final
focus detection operation by the focus detection unit while the focus lens unit
is moved toward an in-focus position, to a speed decelerated from the driving speed
before the final focus detection operation.
One aspect of the camera of the present invention comprises an image-taking optical
system including a focus lens unit, a focus detection unit which detects the focusing
state of the image-taking optical system, a driving unit which drives the focus
lens unit, and a controller which controls the driving speed of the focus lens
unit through the driving unit and controls the focus detection unit to perform
a focus detection operation at least once while the focus lens unit is moved. The
controller sets the driving speed of the focus lens unit at the time of at least
the final focus detection operation by the focus detection unit while the focus
lens is moved toward in-focus position, to a speed decelerated from the driving
speed before the final focus detection operation.
One aspect of the lens apparatus of the present invention which is mountable
to a camera detecting at least once the focusing state of the image-taking optical
system through a focus detection unit while the focus lens unit is moved. The lens
apparatus comprises an image-taking optical system including the focus lens unit,
a driving unit which drives the focus lens unit, and a controller which controls
the driving speed of the focus lens unit through the driving unit. The controller
sets the driving speed of the focus lens unit at the time of at least the final
focus detection operation by the focus detection unit while the focus lens unit
moves to an in-focus position, to a speed decelerated from the driving speed before
the final focus detection operation.
A detailed configuration of the camera system, camera and lens apparatus of the
invention, the above and other objects and features of the invention will be apparent
from the embodiments, described below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a camera system according to Embodiment 1;
FIG. 2 is a flow chart showing an AF operation of the camera system according
to Embodiment 1;
FIG. 3 is a flow chart showing an AF operation of the camera system according
to Embodiment 1;
FIG. 4 is a flow chart showing an AF operation of the camera system according
to Embodiment 1;
FIG. 5 illustrates an operation of the camera system according to Embodiment
1 showing a relationship between its overlap control and lens speed; and
FIG. 6 is a block diagram of a camera according to Embodiment 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference now to the drawings, embodiments of the present invention will
be explained below.
(Embodiment 1)
FIG. 1 shows a structure of a lens interchangeable type camera system according
to Embodiment 1. In FIG. 1, reference numeral
1 denotes a camera (digital
still camera),
2 denotes an image-taking lens (lens apparatus) which is
attached to the camera
1. In FIG. 1, dotted lines express mechanical connections
and solid lines express electrical connections.
First, the structure of the image-taking lens
2 will be explained.
Reference numeral
7 denotes a motor which is the power source to generate
a driving force for the focus lens
3 which moves for focusing,
6
denotes a decelerator which decelerates the output of the motor
7 and increases
torque,
5 denotes a focusing unit including a cam cylinder, etc., which
converts the output from the decelerator
7 to a driving force in the direction
of the optical axis of the focus lens
3.
Reference numeral
10 denotes a lens controller which controls all
units in the image-taking lens
2, which consists of a microcomputer. Reference
numeral
11 denotes an EEPROM which is an electrically erasable storage element
and stores various historical data and various data about the image-taking lens
2 obtained through communications with the lens controller
10.
Reference numeral
4 denotes a driver circuit which gives driving
power from the lens controller
10 to the motor
7,
9 denotes
an encoder unit which outputs a signal (pulse signal) according to the movement
of the focus lens
3 which is driven by the motor
7 through the decelerator
6 and focusing unit
5. This encoder unit
9 may also detect
an amount of rotation of the motor
7.
Reference numeral
12 denotes a lens contact unit as a communication
unit with a contact for the lens controller
10 to communicate with the camera
1.
Then, the structure of the camera
1 will be explained. Reference numeral
15 denotes a camera controller which performs overall control of the camera
1 and camera system, which consists of a microcomputer.
Reference numeral
13 denotes a focus detection unit which detects
an amount of focal shift with respect to an object of the image-taking optical
system in the image-taking lens
1 in response to a command from the camera
controller
15. Based on the detection result from this focus detection unit
13, the camera controller
15 and lens controller
10, that
is, camera system controlling means perform processing and control related to AF operation.
Reference numeral
14 denotes a photometric unit which measures brightness
of an object according to a command from the camera controller
15 and
16
denotes a camera contact unit as a communication unit for the controller
15
to communicate with the lens controller
10. When the image-taking lens
2
is mounted in the camera
1, the camera contact unit
16 has electrical
contact with the lens contact unit
12, the communication between the camera
controller
15 and lens controller
10 is enabled and allowing power
supplied from the camera
1 side to the lens
2 side is enabled.
Reference numeral
17 denotes an image-pickup element made up of
a CCD or CMOS sensor, etc., which photoelectrically converts an image of an object
formed by the image-taking optical system of the image-taking lens
2 and
outputs an image signal. The image signal output from the image-pickup element
17 is subjected to image processing by an image processing circuit (not
shown) and recorded in a recording medium (not shown) (semiconductor memory, magnetic
disk, optical disk, etc.).
Then, the autofocusing operation of the camera system of this embodiment will
be explained using the flow charts shown in FIGS. 2 to
4. For ease of understanding
of explanation here, the operations of the camera controller
1 and lens
controller
10 are shown in a series of flow charts, but the camera controller
1 and the lens controller
10 have different operation programs.
In step (denoted as "S" in the figure)
101, when the camera controller
15 receives an ON signal from an image taking preparation switch (not shown)
provided in the camera
1, the camera controller
15 starts an AF operation
in response thereto.
First, in step
102, the camera controller
15 sends a command
to the lens controller
10 requesting data of focus sensitivity (amount of
movement of the focus with respect to a unit amount of movement of the focus lens
3) FS. In response to this command, the lens controller
10 reads
the value of the focus sensitivity FS corresponding to the current position of
the focus lens
3 detected by a lens position detector (not shown) from the
data stored in the EEPROM
11 and sends the value of the focus sensitivity
FS to the camera controller
15.
In step
103, the camera controller
15 sends a command to the photometric
unit
14 to perform a photometric operation. Furthermore, the camera controller
15 sends a command to the lens controller
10 requesting optical data
necessary to calculate an exposure time of the image-pickup element
17 stored
in the EEPROM
11. In response to this command, the lens controller
10
sends the optical data to the camera controller
15. The camera controller
15 calculates an exposure control value during the exposure of the image-pickup
element
17 and lens movement speed limit values V
1 and V
2
used for the driving of the focus lens
3 based on the photometric result,
the focus sensitivity FS, and optical data received from the lens
2.
The lens movement speed limit value V
1 is a maximum speed as the lens
speed and at least one focus detection is performed for overlap control during
constant-speed driving at this maximum speed. On the other hand, the lens movement
speed limit value V
2 is a lens speed when the speed is kept constant after
it is decelerated from the maximum speed and at least the final focus detection
is performed for overlap control during this constant-speed driving after deceleration.
When the encoder unit
9 outputs a pulse signal according to the rotation
of the motor
7, the rotation speed of the motor
7 is handled as the
moving speed of the focus lens
3 in this embodiment.
Then, in step
104, the camera controller
15 sends the calculated
lens speed limit values V
1 and V
2 to the lens controller
10.
Then, in step
105, the lens controller
10 sends information relating
to the information processing capacity such as an operating frequency of the lens
controller
10 to the camera controller
15.
Then, in step
106, the camera controller
15 calculates lens driving
restriction coefficients K
1, K
2 and D
2 based on the output
of the photometric unit
14 and the information processing capacity of the
lens controller
10 sent from the lens controller
10 and sends them
to the lens controller
10. The lens driving restriction coefficients K
1
and K
2 are deceleration ratios for decelerating the lens speed and the lens
driving restriction coefficient D
2 indicates a lens driving distance to
make the lens speed constant for the final focus detection of overlap control.
Then, in step
107, the camera controller
15 sends a command to
the focus detection unit
13 to start a focus detection operation. Then,
the camera controller
15 sends a command to the lens controller
10
requesting the optical data necessary to calculate an amount of movement of the
focus lens
3 (or amount of driving of the motor
7) which is stored
in the EEPROM
11. The lens controller
10 sends the above described
optical data to the camera controller
15 according to this command.
The camera controller
15 calculates an amount of movement D of the focus
lens
3 necessary to achieve focusing on the object based on the output of
the focus detection unit
13 and the optical data sent from the lens controller
10.
Then, in step
108, the camera controller
15 sends the calculated
amount of movement D to the lens controller
10. Then, in step
109,
the lens controller
10 supplies power to the motor
7 through the
driver circuit
4 based on the transmitted amount of movement D and moves
the focus lens
3.
Here, in step
110, the lens controller
10 compares the calculated
amount of movement D with a minimum value D
1 (=K
2·V
2)
with which it is possible to perform acceleration control of the focus lens
3.
When the calculated amount of movement D is greater than D
1, the process
progresses to step
111 and when it is smaller, the process progresses on
to step
135.
In step
111, the lens controller
10 decides whether the output
from
the encoder unit
9 has changed or not (whether the focus lens
3 is
driving or not) and when the lens controller
10 confirms a change of the
output, the process progresses to step
112.
In step
112, the lens controller
10 calculates a moving speed V
of the focus lens
3 based on the cycle of the pulse signal output from the
encoder unit
9.
Then, in step
113, the lens controller
10 subtracts 1 from the
amount of movement of the focus lens
3 and regards this value as D.
Then, in step
114, the lens controller
10 compares the calculated
amount of movement D with the value of K
1·(V
1-V
2)+D
2+K
2·V
2.
When the calculated amount of movement D is greater than D
1,the process
progresses to step
115 and when it is smaller than D
1, the process
progresses to step
123.
In step
115, the lens controller
10 compares the moving speed V
with the moving speed limit value V
1. When the moving speed V is smaller
than V
1, the process progresses to step
140 where the lens controller
10 increases the motor speed by a predetermined amount and the process back
to step
111. When the moving speed V is greater than V
1, the process
progresses to step
116.
Then, in step
116, the camera controller
15 decides whether it
is possible to perform a focus detection operation judging from the communication
with the lens controller
10 and the situation of the reset operation, etc.,
of the focus detection unit
13 or not and if the focus detection operation
is possible, the process progresses to step
117 and if not possible, the
process progresses to step
120.
In step
117, the camera controller
15 sends a command to the lens
controller
10 requesting the data of the focus sensitivity FS. In response
to this command, the lens controller
10 reads the value of the focus sensitivity
FS corresponding to the current position of the focus lens
3 from the data
stored in the EEPROM
11 and sends the value of the focus sensitivity FS
to the camera controller
15.
Then, in step
118, the camera controller
15 sends a command to
the focus detection unit
13 to carry out a focus detection operation. Then,
the camera controller
15 sends a command to the lens controller
10
requesting the optical data stored in the EEPROM
11. In response to this
command, the lens controller
10 sends the optical data stored in the EEPROM
11 to the camera controller
15.
The camera controller
15 calculates an amount of movement D of the focus
lens
3 based on the output of the focus detection unit
13, the value
of the focus sensitivity FS sent from the lens controller
10 in step
117
and step
118 and the optical data.
Then, in step
119, the camera controller
15 sends the calculated
amount of movement D to the lens controller
10.
Then, in step
120, the lens controller
10 decides whether the
output of the encoder unit
9 has changed or not and when the lens controller
10 confirms some change of the output, the process progresses to step
121.
In step
121, the lens controller
10 subtracts 1 from the calculated
amount of movement D of the focus lens
3 and regards this value as a new D.
Then, in step
122, the lens controller
10 compares the calculated
amount of movement D with K
1·(V
1-V
2)+D
2+K
2·V
2.
When the amount of movement D is greater than D
1, the process progresses
to step
116. When the amount of movement D is smaller than D
1, the
process progresses to step
123 and decreases the motor speed by a predetermined amount.
In step
124, the lens controller
10 detects whether the output
of
the encoder unit
9 has changed or not and when it confirms some change of
the output, the process progresses to step
125. In step
125, the
lens controller
10 calculates the moving speed V of the focus lens
3
based on the cycle of the pulse signal output from the encoder unit
9.
Then, in step
126, the lens controller
10 subtracts 1 from the
amount of movement D of the focus lens
3 and regards this value as a new
D. In step
127, the lens controller
10 compares the moving speed
V with the moving speed restriction V
2 and when the moving speed V is smaller
than V
2, the process progresses to step
128 and when it is greater,
the process progresses to step
123.
In step
128, the camera controller
15 sends a command to the lens
controller
10 requesting the data of the focus sensitivity FS. In response
to this command, the lens controller
10 reads the value of the focus sensitivity
FS corresponding to the current position of the focus lens
3 from the data
stored in the EEPROM
11 and sends the value of the focus sensitivity FS
to the camera controller
15.
In step
129, the camera controller
15 sends a command to the focus
detection unit
13 to perform a focus detection operation. Then, the camera
controller
15 sends a command to the lens controller
10 requesting
it to send the optical data stored in the EEPROM
11. In response to this
command, the lens controller
10 sends the optical data stored in the EEPROM
11 to the camera controller
15.
The camera controller
15 calculates the amount of movement D of the focus
lens
3 based on the output of the focus detection unit
13, the value
of the focus sensitivity FS sent from the lens controller
10 in step
128
and step
129 and optical data.
Then, in step
130, the camera controller
15 sends the calculated
amount of movement D to the lens controller
10.
Then, in step
131, the lens controller
10 decides whether the
output of the encoder unit
9 has changed or not and when some change of
the output is confirmed, the process progresses to step
131.
In step
132, the lens controller
10 subtracts 1 from the calculated
amount of movement D of the focus lens
3 and regards this value as a new D.
Then, in step
133, the lens controller
10 compares the calculated
amount of movement D with K
2·V
2. When the amount of movement
D is greater than K
2·V
2, the process progresses to step
131.
When the amount of movement D is smaller than K
2·V
2, the process
progresses to step
134 and decreases the motor speed by a predetermined amount.
In step
135, the lens controller
10 detects whether the output
of
the encoder unit
9 has changed or not, and when some change of the output
is confirmed, the process progresses to step
136. In step
136, the
lens controller
10 calculates the moving speed V of the focus lens
3
based on the cycle of the pulse signal output from the encoder unit
9.
Then, in step
136, the lens controller
10 subtracts 1 from the
amount of movement D of the focus lens
3 and regards this value as a new
D. Then, in step
137, the lens controller
10 decides whether the
amount of movement D has become 0 or not and when it is 0, the lens controller
10 moves on to step
138 and when the amount of movement D is not
0, the process progresses to step
134.
In step
138, the lens controller
10 terminates the driving of the
focus lens
3 and stops the power supply to the motor
7. Then, the
lens controller
10 sends information on the termination of the driving of
the focus lens
3 to the camera controller
15 and terminates the AF operation.
FIG. 5 shows the relationship between the position and speed of the focus lens
3 during AF control in a graph according to the above described flow chart.
The horizontal axis shows the position of the focus lens
3 and the vertical
axis shows the moving speed of the focus lens
3. Furthermore, ; on the graph
shows points at which a focus detection operation is performed.
First, when the start of an AF operation is indicated at position (
1),
the initial focus detection operation F
1 is performed, driving control of
the focus lens
3 is started based on the amount of movement D until an in-focus
position calculated based on the result (steps
101 to
109). Then,
the speed of the focus lens
3 (lens speed) is accelerated to V
1 (steps
111 to
115). Here, the amount of movement D is a value containing
errors with respect to the amount of movement A up to the true in-focus position.
When the lens speed reaches V
1, the lens speed is controlled so that
the lens is driven at the constant speed V
1 and a focus detection operation
is repeated as many times as possible in this constant speed driving state (three
times F
2 to F
4 in FIG. 5) and the driving of the lens is controlled
while updating (correcting) the remaining amount of movement D up to the in-focus
position (steps
116 to
122).
Then, after the remaining amount of movement D up to the in-focus position
becomes K
1·(V
1-V
2)+D
2+K
2·V
2,
the lens speed is decelerated down to V
2 and the final focus detection operation
F
5 is carried out in a constant speed driving state at the lens speed V
2
(steps
128 to
133). The final remaining amount of movement D up to
the in-focus position is calculated based on the detection result at this time
and the point at which deceleration is started toward the stop position is determined.
Then, after the remaining amount of movement D becomes K
2·V
2,
the lens speed is decelerated and when the remaining amount of movement D becomes
0, the driving of the lens is completed (steps
134 to
139).
The above described flow chart applies to a case where the amount of lens movement
D calculated first is an amount of movement allowing the lens speed to be accelerated
to V
1, but a flow chart applicable to the case where the amount of lens
movement D is smaller than that, unable to accelerate the lens speed to V
1
will be omitted. However, such an operation can be as follows, for example:
When the start of an AF operation is indicated at the lens position (
2),
an initial focus detection operation F
1′ is carried out and the driving
control of the focus lens
3 is started based on the amount of movement D
up to the in-focus position calculated based on the result. Then, the lens speed
is accelerated. Here, the amount of movement D is a value containing errors with
respect to the amount of movement B up to the true in-focus position.
Deceleration is performed after the lens speed V
3 is reached
at which the remaining amount of movement D up to the in-focus position becomes
K
1·(V
3-V
2)+D
2+K
2·V
2 until the
lens speed reaches V
2 and a final focus detection operation F
2′
is carried out in a constant speed driving state at the lens speed V
2. Then,
based on the detection result at this time, the final remaining amount of movement
D up to the in-focus position is calculated and the point at which deceleration
toward a stop position is started is determined.
Then, after the remaining amount of movement D becomes K
2·V
2,
the lens speed is decelerated and when the remaining amount of movement D becomes
0, the driving of the lens is terminated.
First, according to the camera system of Embodiment 1, through a focus detection
operation which is carried out repeatedly during the driving of the focus lens
3 and operations for correcting the amount of driving of the focus lens
3, the final focus detection operation for determining the accuracy of final
stoppage at the in-focus position, which is carried out immediately before the
driving is completed, and the operation for correcting the amount of driving of
the focus lens
3 are carried out after the moving speed of the focus lens
3 is decelerated down to a predetermined speed at predetermined timing,
and in this way it is possible to reduce the amount of movement of the focus lens
3 necessary for stop control and bring the position of the focus lens
3
at this time closer to the in-focus position compared to the conventional system.
Thus, it is possible to reduce focus detection errors due to influences of aberration
variations, etc., up to the in-focus position and errors in calculating the amount
of driving due to variations of focus sensitivity, etc., and exclude image flows
on the focus detection sensor caused by the movement of the focus lens
3
which may cause deterioration of the focus detection accuracy as much as possible
to improve the focusing accuracy.
Second, the speed of the focus lens
3 is decelerated down to a predetermined
speed based on at least brightness of the object and the value of focus sensitivity,
and it is thereby possible to keep the image flow on the focus detection sensor
within a light storage time substantially constant even when the image-taking conditions
are changed and always keep the focusing accuracy stable.
Third, by decelerating the focus lens
3 at a predetermined timing based
on the current moving speed and a constant speed after deceleration, it is possible
to provide a minimum necessary predetermined speed area according to the time required
for deceleration and ensure stable focusing accuracy through a short-time operation.
Fourth, by correcting the deceleration timing of the focus lens
3
according to at least the information processing capacity of the lens controller
10, it is possible to perform a focus detection operation and an operation
of correcting the amount of driving of the focus lens
3 in a predetermined
speed area reliably irrespective of the operating condition and always make the
focusing accuracy stable.
In this embodiment, the motor
7 and decelerator
6 are provided
inside
the image-taking lens
2, but these can also be provided on the camera side.
Furthermore, this embodiment has described the case where the camera
controller
15 and lens controller
10 are each assigned a portion
of the processing related to speed control of the focus lens based on the detection
result of the focus detection unit
13, but it is also possible to assign
the whole processing related to speed control to either the camera controller or
lens controller.
(Embodiment 2)
Above described Embodiment 1 has described the camera system allowing the mounting
of the image-taking lens in the camera, but the present invention is also applicable
to a lens-integral type camera.
FIG. 6 shows a lens-integral type camera of Embodiment 2 of the present invention.
In this camera
1′, the same components as those in Embodiment 1 are
assigned the same reference numerals as those in Embodiment 1.
In this case, the functions of the lens controller of Embodiment 1 are included
in the camera controller
15 and the camera controller
15 performs
overall control including the overlap control explained in Embodiment 1.
While preferred embodiments have been described, it is to be understood that
modification and variation of the present invention may be made without departing
from scope of the following claims.
*
