Title: Multiple viewing angle cover having integral light pipe
Abstract: An electronic device using total internal reflection to guide light from a light source housed within the electronic device to the surface of the device. The electronic device has a cover secured to a protective housing to form a protective enclosure for the electronic device. The cover is adapted to use total internal reflection to guide light through the cover to a plurality of surface portion of the cover. A second surface portion of the cover is adapted to totally internally reflect a first portion of the light to the first surface portion.
Patent Number: 6,937,812 Issued on 08/30/2005 to Schladenhauffen, et al.
| Inventors:
|
Schladenhauffen; Mark S. (Westford, MA);
Manjunath; Hassan R. (Nashua, NH);
Delaney, III; Patrick J. (Sudbury, MA)
|
| Assignee:
|
Rockwell Automation Technologies, Inc. (Mayfield Heights, OH)
|
| Appl. No.:
|
881621 |
| Filed:
|
June 14, 2001 |
| Current U.S. Class: |
385/146; 385/92; 385/134 |
| Intern'l Class: |
G02B 006/42 |
| Field of Search: |
385/146,92-94,134,138
362/31
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Font; Frank G.
Assistant Examiner: Mooney; Michael P.
Attorney, Agent or Firm: Yoder; Patrick S., Walbrun; William B.
Claims
1. An electronic device, comprising:
a protective housing;
a light source disposed within the protective housing; and
a cover secured to the protective housing to form a protective enclosure for
the electronic device and to form a light guide for guiding a first portion of
light from the light source to a first surface portion of the cover, a second surface
portion of the cover being adapted to totally internally reflect the first portion
of the light to the first surface portion, wherein the first surface portion comprises
an inverted pyramid portion extending from a third surface portion of the cover.
2. The electronic device as recited in claim 1, wherein the cover is adapted
to refract the first portion of the light through the first surface portion of
the cover.
3. The electronic device as recited in claim 1, further comprising a plurality
of first surface portions extending from a third surface portion of the cover,
wherein each of the first surface portions extends a different distance from the
third surface portion.
4. The electronic device as recited in claim 1, wherein the cover is adapted
to refract a second portion of light from the light source through the second surface portion.
5. The electronic device as recited in claim 4, wherein the cover has a third
surface portion, the cover being adapted to totally internally reflect the first
and second portions of light to the second surface portion of the cover.
6. The electronic device as recited in claim 1, wherein the cover comprises a
molded polymeric material.
7. The electronic device as recited in claim 6, wherein the polymeric material
comprises Trogamid®.
8. An electronic device, comprising:
a protective housing;
a light source disposed within the protective housing; and
a cover secured to the protective housing to form a protective enclosure for
the electronic device and to form a light guide for guiding a first portion of
light from the light source to a first surface portion of the cover, a second surface
portion of the cover being adapted to totally internally reflect the first portion
of the light to the first surface portion, wherein the electronic device receives
power via a cable inserted into the protective housing, the cover having a guide
portion adapted to guide the cable to a desired position and to secure the cable
between the protective housing and the cover as the cover is secured to the protective
housing.
9. The electronic device as recited in claim 8, wherein the guide portion is
configured with a first serrated surface and a corresponding portion of the protective
housing is configured with a second serrated surface, the first and second serrated
surfaces being adapted for engagement when the cover is disposed on the protective housing.
10. The electronic device as recited in claim 1, wherein the first surface portion
is angled with respect to a direction of propagation of light through the cover.
11. The electronic device as recited in claim 1, wherein the first surface portion
comprises a plurality of surfaces angled with respect to a direction of propagation
of light through the cover, wherein light is refracted through the first surface
portion at a plurality of angles with respect to the direction of propagation of
light through the cover.
12. The electronic device as recited in claim 1, the cover further comprising
a light-receiving portion extending to a position adjacent to the light source.
13. The electronic device as recited in claim 4, wherein the third surface portion
has an angle of approximately 25 degrees with respect to an interior surface of
the cover.
14. The electronic device as recited in claim 1, wherein the light source is
a light emitting diode (LED).
15. The electronic device as recited in claim 1, wherein the cover comprises
a material having an index of refraction of approximately 1.566 at a wavelength
of 589.3 nm.
16. The electronic device as recited in claim 1, wherein the light source provides
light in a plurality of colors.
17. The electronic device as recited in claim 1, wherein the cover is adapted
to totally internally reflect light from the light source in a plurality of colors.
18. A protective cover for an enclosure, comprising:
a first surface region of the cover, the first surface region being oriented
on a first side of the enclosure;
a second surface region of the cover, the second surface region being oriented
on a second side of the enclosure; and
a first portion of the cover, the first portion being adapted to receive light
from a light source and totally internally reflect the light to the first surface
region and the second surface region, wherein a first portion of the light is totally
internally reflected at the first surface region to the second surface region through
the first portion of the cover.
19. The cover as recited in claim 18, wherein a second portion of the light is
refracted at the first surface.
20. The cover as recited in claim 18, wherein the first portion comprises an
angled member extending from a third surface region of the cover.
21. A protective cover for an enclosure, comprising:
a first surface region of the cover, the first surface region being oriented
on a first side of the enclosure;
a second surface region of the cover, the second surface region being oriented
on a second side of the enclosure, wherein the first side of the enclosure is transverse
to the second side of the enclosure; and
a first portion of the cover, the first portion being adapted to receive light
from a light source and to totally internally reflect the light to the first surface
region and the second surface region.
22. The cover as recited in claim 18, wherein the first side is opposite of the
second side.
23. A protective cover for an enclosure, comprising:
a first surface region of the cover, the first surface region being oriented
on a first side of the enclosure;
a second surface region of the cover, the second surface region being oriented
on a second side of the enclosure; and
a first portion of the cover, the first portion being adapted to receive light
from a light source and to totally internally reflect the light to the first surface
region and the second surface region, wherein the first surface region is adapted
to refract the light from the light source in a plurality of directions.
24. The cover as recited in claim 23, wherein the first surface region is adapted
with a plurality of angled surface faces.
25. The cover as recited in claim 18, wherein the first surface region comprises
a smooth strip portion of the first surface region.
26. The cover as recited in claim 18, wherein the first surface region comprises
an inverted pyramid portion extending from the first side of the enclosure.
27. The cover as recited in claim 18, further comprising a plurality of inverted
pyramid portions extending from the first side of the enclosure, wherein a first
inverted pyramid portion extends further from the first side of the enclosure than
a second inverted pyramid portion.
28. The cover as recited in claim 18, wherein the enclosure receives a cable,
the cover having a guide portion adapted to guide the cable to a desired position
within the enclosure and to secure the cable between cover and a portion of the enclosure.
29. The cover as recited in claim 28, wherein the guide portion is configured
with a first serrated surface and a corresponding portion of the protective housing
is configured with a second serrated surface, the first and second serrated surfaces
being adapted for engagement when the cover is disposed on the protective housing.
30. The cover as recited in claim 18, wherein the cover is adapted to totally
internally reflect a plurality of colors of light from the light source.
31. A cover for an electronic device, comprising:
a first portion adapted to cooperate with a protective housing to form a protective
enclosure for the electronic device, the first portion having first and second
exterior surface portions oriented at an angle to each other; and
a second portion adapted to extend from the first portion to a position adjacent
to a light source within the enclosure, wherein light from the light source is
internally reflected through the second portion to the first and second exterior
surfaces, and wherein a portion of the light from the light source is refracted
at the first and second exterior surfaces, and a portion of the light is totally
internally reflected at the first exterior surface portion.
32. The cover as recited in claim 31, wherein the portion of light that is totally
internally reflected at the first exterior surface is internally reflected to the
second exterior surface portion.
33. A cover for an electronic device, comprising:
a first portion adapted to cooperate with a protective housing to form a protective
enclosure for the electronic device, the first portion having first and second
exterior surface portions oriented at an angle to each other; and
a second portion adapted to extend from the first portion to a position adjacent
to a light source within the enclosure, wherein light from the light source is
internally reflected through the second portion to the first and second exterior
surfaces, further wherein the light from the light source is refracted at the first
and second exterior surfaces, one of the first and second exterior surface portions
being adapted to refract the light from the light source in a plurality of directions.
34. The cover as recited in claim 31, wherein one of the first and second exterior
surface portions is adapted to produce a plane of refracted light.
35. The cover as recited in claim 31, wherein the electronic device receives
a cable, the cover having a guide portion adapted to guide the cable to a desired
position and to secure the cable between the protective housing and the cover as
the cover is secured to the protective housing.
36. The cover as recited in claim 31, wherein the guide portion is configured
with a first serrated surface and a corresponding portion of the protective housing
is configured with a second serrated surface, the first and second serrated surfaces
being adapted for engagement when the cover is disposed on the protective housing.
37. A method of providing visual information from an electronic device, comprising
the acts of:
producing light from a light source housed within a protective enclosure of the
electronic device, the light providing data from the electronic device;
adapting the electronic device to guide the light from the light source to a
plurality of surface portions of the enclosure using total internal reflection
to guide the light through a portion of a cover of the enclosure and to refract
the light at the plurality of surface portions so that the light is visible from
a plurality of sides of the enclosure; and
providing each of a plurality of light sources housed within the electronic device
with a unique color.
38. The method as recited in claim 37, wherein adapting comprises refracting
light in a different pattern at each of the plurality of surface portions.
39. The method as recited in claim 37, wherein adapting comprises molding the cover.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of enclosures for electronic
devices. More particularly, the invention relates to a technique for optically
coupling the light produced by a light emitting source housed within an enclosure
to the exterior of the enclosure via a light pipe integrated into a cover of the
enclosure, the cover enabling a viewer to view the light from multiple viewing
angles around the enclosure.
2. Description of the Related Art
Many electronic devices are designed to produce a visual output. The visual
output may provide a myriad of information in a myriad of ways. For example, a
device may provide text and images on a computer monitor. Alternatively, a device's
visual output may be a light to indicate that the device is operating.
The type of visual output used may be dictated by a number of factors, such as
the information to be conveyed and the operating environment of the device. For
example, a production line may utilize one or more electronic sensors to provide
an operator with information regarding the status of production. An electronic
sensor may be placed anywhere along the production line. The electronic sensor
may be located at floor level, below floor level, or above floor level, depending
on the orientation of the production line. Typically, the visual output of a sensor
is visible from only one location from the workfloor.
Many electronic devices utilize a light emitting diode (LED) to convey information.
In some instances, an LED may be mounted on an exterior surface of an electronic
device. However, the LED is more susceptible to damage when mounted on the exterior
of an electronic device. Additionally, electrical wiring typically must be routed
to the LED to enable it to operate. In some instances, an LED, or LED's, may act
as nuisance sources of electro-optical/electro-magnetic noise. LED's also have
been mounted on circuit boards housed within a protective enclosure. The light
from an LED may be coupled through a window to the outside. Alternatively, a light
guide, such as a fiber optic cable, may be used to direct light from the LED to
the outside of the enclosure. The assembly of the device is complicated by the
need to route the light guide from the LED to a cover of the enclosure. Additionally,
in both of these configurations the viewing angle for viewing the light from the
LED is limited. In the former, a viewer is only able to see the light from the
LED when the viewer is positioned directly in the line of sight of the window and
the LED. In the latter, the process of reflecting the light internally through
the optical fiber results in the optical fiber effectively producing a unidirectional
beam of light. As a result, a viewer located directly across from the fiber optic
cable may be able to see the light from the LED but a viewer located on another
side of the device may not. In a production environment, where an operator may
be constantly changing positions, an electronic device having a visual output with
a limited viewing angle may be problematic to production. For example, a production
line may have a sensor to detect various operating conditions on the line. The
sensor may utilize one or more LED's to indicate these operating conditions to
an operator. If the operator cannot see the output of the LED's from the operator's
location, either the information will be lost or the operator will have to move
to a another location where the output of the LED can be seen.
There is a need, therefore, for an improved technique for optically coupling
the light from an LED housed within an enclosure to a viewer located on the outside
of the enclosure in a manner that will enable the light to be seen from multiple
viewing angles around the electronic device.
SUMMARY OF THE INVENTION
The present invention provides a technique for providing visual information from
an electronic device designed to respond to these needs. According to one aspect
of the technique, an electronic device housing a light source is featured. The
electronic device has a protective enclosure formed from a protective housing and
a cover secured to the protective housing. The cover forms a light guide for guiding
a first portion of light from the light source to a first surface portion of the
cover. A second surface portion of the cover is adapted to totally internally reflect
the first portion of the light to the first surface portion. The electronic device
may receive power via a cable inserted into the protective housing. The cover may
have a guide portion adapted to guide the cable to a desired position within the
housing and to secure the cable between the protective housing and the cover as
the cover is secured to the protective housing.
According to another aspect of the present invention, a protective cover
for an enclosure is featured. The protective cover has a first surface region and
a second surface region. The first surface region is oriented on a first side of
the enclosure and the second surface region is oriented on a second side of the
enclosure. A first portion of the cover is adapted to receive light from a light
source and to totally internally reflect the light to the first surface region
and the second surface region. The cover may have a guide portion adapted to guide
a power cable to a desired position within the housing and to secure the cable
between the protective housing and the cover as the cover is secured to the protective housing.
According to another aspect of the present invention, a method of providing
visual information from an electronic device is featured. The method produces light
from a light source housed within a protective enclosure of the electronic device.
The light from the light source provides data from the electronic device. The method
also adapts the electronic device to guide the light from the light source to a
plurality of surface portions of the enclosure. Total internal reflection is used
to guide the light through a portion of the cover of the enclosure. The method
also refracts the light at the plurality of surface portions so that the light
is visible from a plurality of sides of the enclosure.
According to another aspect of the present invention, a method of manufacturing
a cover for an electronic device is featured. The method identifies a moldable
material's critical angle for total internal reflection of light from a light source.
The light source is housed within the electronic device. The method also designs
a shape for the cover that uses total internal reflection to direct light from
the light source to a surface portion of the cover. The method also provides for
molding the cover to the designed shape.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other advantages of the invention will become apparent upon
reading the following detailed description and upon reference to the drawings in which:
FIG. 1 is a first perspective view of an electronic sensor having an enclosure
with a cover having integral light pipes to optically couple light from a plurality
of LED's housed within the enclosure to a surface portion of the cover, according
to an exemplary embodiment of the present invention;
FIG. 2 is a second perspective view of the electronic sensor of FIG. 1;
FIG. 3 is an exploded view of the components of the electronic sensor of FIG. 1;
FIG. 4 is a rear elevational view of a cover having integral light guides, according
to an exemplary embodiment of the present invention;
FIG. 5 is a rear perspective view of the cover of FIG. 4;
FIG. 6 is a cross-sectional view of the light guide portion of the cover, taken
generally along line 6-6 of FIG. 4;
FIG. 7 is a detailed view of a portion of the housing; and
FIG. 8 is an elevational view of the interior of a protective housing, according
to an exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
Turning now to the drawings, and referring first to FIGS. 1 and 2, an electronic
device, designated generally by the reference number
20, is illustrated.
In the illustrated embodiment, the electronic device
20 is an optical sensor.
However, the present invention is not limited to sensors. The electronic device
has a protective enclosure
22 that utilizes a housing
24 and a cover
26 to house and protect components of the electronic device
20. In
the illustrated embodiment, the cover
26 is securable to the housing
24.
The protective enclosure
22 has a generally cubic shape. However, in this
embodiment, the housing
24 is configured with a hollow extension
28
that extends outward from a flat surface
30 of the housing
24. In
this embodiment, the hollow extension
28 enables an optical emitter and
an optical receiver located within the housing
24 to have an unobstructed
view of a target.
In the illustrated embodiment, a circuit board (not shown) having a plurality
of light emitting diodes (LED's) (not shown) is housed within the housing
24
and cover
26. Alternatively, another device for emitting light may be used,
such as a light bulb or semiconductor laser. Each LED may provide light of a single
color or a plurality of colors. Furthermore, each of the plurality of LED's may
provide one or more different colors of light. Additionally, the light from the
LED's may be pulsed or continuous.
The cover
26 is adapted to form integral light guides for coupling the
light from the LED's. The light guides use internal reflection to guide the light
from the LED to the exterior of the enclosure
22. The cover
26 is
configured with a generally flat portion
32 that extends generally over
one side of the enclosure
22. In the illustrated embodiment, the cover
26
is comprised of a molded polymeric material, such as Trogamid®. Trogamid®
is a transparent nylon material that has an average transmittance of 90% over the
visible range of light, i.e., 350-680 nm. Generally, the surface of the cover
26
is formed with a relatively rough surface texture that makes the cover relatively
opaque. However, in the illustrated embodiment, the cover
26 has a plurality
of smooth strips
34 that are formed slightly recessed from the generally
flat portion of the cover
26 during the molding process. The smooth strips
34 are made smooth by polishing the appropriate portion of the mold that
forms the smooth strip. Each smooth strip
34 forms a portion of a light
guide for an LED. The smooth surface of each smooth strip
34 enables light
to be internally reflected at the surface of each smooth strip
34 in a precise
manner. Additionally, the smooth surface of each strip
34 enables a portion
of the light to be refracted through the surface without scattering. Thus, the
smooth strips
34 in the illustrated embodiment serve two purposes: internally
reflecting a portion of the light from an LED and refracting a portion of the light
from the LED.
In the illustrated embodiment, the cover
26 also is configured with a
plurality
of inverted pyramid portions
36 that are located on a second side of the
enclosure
22. In this embodiment, light from an LED is internally reflected
through the cover
26 to an inverted pyramid portion
36. In the exemplary
embodiment, the inverted pyramid portions
36 also are formed with a smooth
surface during the molding process. The shape of an inverted pyramid portion
36
causes light that has been internally reflected through the cover to be refracted
in many directions. This enables the light from an LED to be seen from multiple
sides of the enclosure
22, such as the front, back, left and right. The
inverted pyramid portions
36 may have different heights or may be otherwise
be configured differently to assist in identification. For example, the far left
pyramid
36 of FIG. 1 is taller than the other two pyramids
36. This
enables a viewer to have an unobstructed view of light from the far left pyramid
36. Additionally, the portion
38 of the light that is coupled to
the strips
34 is transmitted through the strips
34 and is visible
from one or more sides of the enclosure. In fact, the cover
26 could be
configured to transmit light in a myriad of configurations. For example, each LED
could be coupled to a second inverted pyramid portion in addition to, or instead
of, a smooth strip
34, or vice versa. In this configuration, an inverted
pyramid portion
36 may be disposed on opposite sides of the enclosure
22.
The cover
26 may be configured to transmit light from additional or different
sides of the enclosure
22.
Referring generally to FIG. 3, the electronic device
20 is assembled
from a plurality of components. A printed circuit (PC) board
42 is used
to couple the various electronic components of the device
20. A transmitter
44 and a sensor
46 are located on one side of the PC board
42.
Several LED's
48 are located on the other side of the PC board
42.
A window
50 and a lens
52 are secured to the hollow extension
28
portion of the housing
24. The window
50 prevents contaminants from
entering the interior of the enclosure
22 but is transparent to enable light
to enter and exit the enclosure
22. The lens
52 focuses the light
onto the optical sensors
46. An optical shield
54 is used to prevent
the sensors
46 from being contaminated with light from sources other than
light from the target area. In addition, the device
20 has an electronic
shield
56 to prevent interference from outside sources of electrical noise.
Power is supplied to the electronic components by a conductive cable
58.
The conductive cable
58 is secured within the device
20 by a clasp
60. The clasp
60 secures the cable
58 between the cover
26
and the housing
24 when the cover
26 is secured to the housing
24.
Also visible in this view are three generally triangular shaped portions
62
of the cover
26. Each triangular shaped portion
62 of the cover
26
is used to receive light from an LED
48 and internally reflect the light
to the strip portions
34 and to the inverted pyramid portions
36.
Referring generally to FIGS. 4 and 5, the cover
26 of the illustrated
embodiment is adapted to use total internal reflection to couple light from three
LED's
48. However, the cover
26 may be configured to couple light
from a greater or lesser number of LED's. The LED's may be used to convey different
pieces of information. For example, one of the LED's may indicate that the device
has power. Another LED may provide an indication whenever the sensor detects a
target object. Another LED may be used to indicate the sensitivity of the detector.
Different colors may be used for each LED. In the illustrated embodiment, the cover
26 has three generally triangular shaped portions
62 extending from
an interior surface
64 of the cover
26, one for each LED. However,
additional triangular shaped portions
62 may be associated with each LED
48. For example, a second triangular shaped portion
62 may be used
to couple light from an LED
48 to a second inverted pyramid portion
36.
The cover
26 has a lip
64 that extends from the interior surface
64 around the perimeter of the cover
26. The lip
64 is configured
for engagement with a corresponding groove in the housing
24. In this embodiment,
the cover
26 also has two openings
68 that align with two corresponding
openings in the housing
24. Two securing members, such as threaded fasteners,
are inserted through the openings
68 to secure the enclosure
22 to
a surface. The cover
26 may have an adjustment hole to enable a screwdriver,
or some other tool, to be inserted through the cover to adjust a potentiometer,
or some other adjustable component, within the device
20. In the illustrated
embodiment, the inverted pyramid portions
36 are located on a surface portion
70 of the cover
26. The surface portion
70 is disposed within
a recess in the housing
24 when the cover
26 is secured to the housing
24.
Referring generally to FIG. 6, generally, whenever a ray of light is incident
on the boundary separating two different optical media, part of the ray is reflected
back into the first media and the remainder is refracted as it enters the second
media. Refraction is the bending of light as it passes through the boundary between
two media. The directions taken by these rays can be described by two well-established
laws of nature. The first law states that the angle at which the incident ray strikes
the interface of two optical media, the angle of incidence, is exactly equal to
the angle the reflected ray makes with the interface, the angle of reflection.
The angles of incidence and reflection are commonly measured from a line perpendicular
to the interface, known as the normal. Furthermore, the incident ray and the reflected
ray lie in the same plane, the reflected ray lying on the opposite side of the
normal from the incident ray. The second law states that the sine of the angle
of incidence and the sine of the angle of refraction have a constant ratio for
all angles of incidence. This constant ratio also is equal to the ratio of the
indices of refraction of the two media. The index of refraction, or refractive
index, of any optical medium is defined as the ratio between the speed of light
in a vacuum and the speed of light in the medium. The refracted ray and the incident
ray also lie in the same plane, the refracted ray lying on the opposite side of
the normal from the incident ray. This relationship, known as Snell's law, can
be written as follows:
n1 sin θ
1=n2
sin θ
2
where: n
1 is the index of refraction of the first medium;
- θ1 is the angle of incidence;
- n2 is the index of refraction of the second medium; and
- θ2 is the angle of refraction.
However, there is an angle of incidence beyond which no light is refracted
through the boundary between the two media. This is known as the critical angle,
θ
C. The critical angle is defined as the smallest angle of incidence,
in the medium of greater index, for which light is totally reflected, i.e., no
light is refracted through the boundary. The equation for finding the critical
angle may be derived from Snell's law and can be written as follows:
where: n
1 is the index of refraction of the first medium;
- n2 is the index of refraction of the second medium; and
- θC is the critical angle.
In the illustrated embodiment, divergent light rays from an LED
48 are
incident on a first surface
72 of a triangular portion
62 of the
cover
26. In the illustrated embodiment, the first surface
72 is
adapted to collect light from the LED that might be reflected from a flat surface.
In the illustrated embodiment, the cover
26 has several surfaces that are
adapted to totally internally reflect light from each LED and direct the light
to a strip portion
34 and an inverted pyramid portion
36. In this
embodiment, the two media at each of the surfaces are air
74 and the material
of the cover
26. The portions of the mold used to form the various surfaces
are polished so that the surfaces of the cover
26 have a smooth polished
texture. This prevents the light incident on the surfaces from being scattered.
In the illustrated embodiment, a first ray
76 from the LED
48 is
incident on a second surface
78 of the triangular portion
62 of the
cover
26. A second ray
80 from the LED
48 is incident on a
third surface
82 of the triangular portion
62 of the cover
26.
A third ray
84 also is incident on the third surface
82. In the illustrated
embodiment, the third surface
82 is angled approximately 25 degrees in relation
to the flat portion
64 of the cover
26.
A line
86 represents the normal to each surface. The index of refraction
of air
74 is, approximately, 1. In the illustrated embodiment, the index
of refraction of the cover is approximately 1.566 at a wavelength of 589.3 mm.
The critical angle, θ
c, for a boundary between the air
74
and the cover
26 is approximately 39.7 degrees, as represented by angle
88. The first, second, and third rays are incident to the second and third
surfaces, respectively, at angles greater than the critical angle. Consequently,
the first, second, and third rays are totally internally reflected inside the cover
26 towards a fourth surface, the strip portion
34. The first, second,
and third rays also are incident to the strip portion
34, at angles greater
than the critical angle and are again totally internally reflected. The first ray
76 is incident to a fifth surface
90 and is again totally internally
reflected. The first ray
76 is then incident to a first face
92 of
the inverted pyramid portion
36. The first ray
76 is incident to
the first face
92 at an angle less than the critical angle and is refracted
through the first face
92. The second ray
80 is incident to a sixth
surface
94 and, again, is totally internally reflected. The second ray
80
is then incident to the first face
92 of the inverted pyramid portion
36
at an angle less than the critical angle and is refracted through the first face
92. The third ray
84 is incident to a second face
96 of the
inverted pyramid portion
36 at an angle less than the critical angle and
is refracted through the second face
96. In the illustrated embodiment,
the faces of the inverted pyramid are angled at an angle of approximately 45 degrees.
A fourth ray
98 and a fifth ray
100 from the LED
48 are
incident
on the strip portion
34 of the cover
26. The fourth ray
98
is incident to the strip portion
34 at an angle less than the critical angle
and is refracted through the strip portion
34. Thus, a portion of the light
from the LED
48 also is guided to and transmitted from the strip portion
34, as well as the inverted pyramid portion
36 of the cover
26.
The fifth ray
100 is incident to the strip portion
34 at an angle
greater than the critical angle and is totally internally reflected towards the
second face
96 of the inverted pyramid portion
36. The fifth ray
100 is incident to the second face
96 of the inverted pyramid portion
36 at an angle less than the critical angle and is refracted through the
second face
96. Please note that the actual number of light rays emanating
from the LED
48 is virtually infinite. Additionally, the number of different
paths the light rays may make through the cover
26 to the strip portion
34 and the inverted pyramid portions also is virtually infinite.
Referring generally to FIGS. 7 and 8, the housing
24 has a groove
102 configured to receive the lip
66 of the cover
26. The
housing also has a hole
104 for receiving a conductor cable
58. The
housing also has a receiving portion
106 for receiving the cable
58.
The receiving portion
106 is notched to guide the cable
58 into the
enclosure
22 for coupling to the PC board
42. The housing
24
also has a securing portion
108 configured to receive the clasp
60
of the cover
26 when the cover
26 is placed on the housing
24.
The securing portion
108 has a serrated surface
110 configured to
contact a serrated portion
112 of the clasp
60. The clasp
60
secures the cable
58 between the cover
26 and the housing
24
as the cover
26 is secured to the housing
24. Additionally, the clasp
60 directs the cable
58 to the desired position within the enclosure.
No additional pieces are needed to secure the cable within the enclosure.
The housing
24 also has two openings
114 that align with the opening
68 in the cover
26 for securing the enclosure
22 to an external
surface. A guide pin
116 is used to align with a guide hole (not shown)
in the PC board
42 to properly position the PC board
42. A plurality
of guide members
118 are used with the guide pin
116 to properly
align the PC board. In addition, the housing
24 has a first orifice
120
and a second orifice
122 therefore. The first orifice
120 enables
light, such as infrared light, to be transmitted from a light source within the
enclosure
22 to a target. The second orifice
122 enables light from
a target to be detected by a sensor
46 within the enclosure.
Referring to FIGS. 5 and 7, in the illustrated embodiment, a plurality
of securing clips
124 on the housing
24 are used to secure the cover
26 to the housing
24. The securing clips
124 are disposed
into openings
126 in corresponding securing member
128 on the cover
26. The clips
124 are flexible to allow elastic deformation of the
clips
124 during insertion of the clips
124 into the openings
126.
While the invention may be susceptible to various modifications and alternative
forms, specific embodiments have been shown in the drawings and have been described
in detail herein by way of example only. However, it should be understood that
the invention is not intended to be limited to the particular forms disclosed.
For example, the present technique may be used with many different types of electronic
devices, including many different types of sensors, such as magnetic sensors, proximity
sensors, etc. The invention is to cover all modifications, equivalents, and alternatives
falling within the spirit and scope of the invention as defined by the following
appended claims.
*
