Image processing system to control vehicle headlamps or other vehicle equipment Number:7,149,613 from the United States Patent and Trademark Office (PTO) owispatent

Title: Image processing system to control vehicle headlamps or other vehicle equipment

Abstract: An imaging system of the invention includes an image array sensor including a plurality of pixels. Each of the pixels generates a signal indicative of the amount of light received on the pixel. The imaging system further includes an analog to digital converter for quantizing the signals from the pixels into a digital value. The system further includes a memory including a plurality of allocated storage locations for storing the digital values from the analog to digital converter. The number of allocated storage locations in the memory is less than the number of pixels in the image array sensor. According to another embodiment, an imaging device includes an image sensor having a plurality of pixels arranged in an array; and a multi-layer interference filter disposed over said pixel array, said multi-layer interference filter being patterned so as to provide filters of different colors to neighboring pixels or groups of pixels.

Patent Number: 7,149,613 Issued on 12/12/2006 to Stam,   et al.

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Inventors:	Stam; Joseph S. (Holland, MI), Pierce; Mark W. (Grandville, MI), Ockerse; Harold C. (Holland, MI)
Assignee:	Gentex Corporation (Zeeland, MI)
Appl. No.:	11/081,036
Filed:	March 15, 2005

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Related U.S. Patent Documents

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	Application Number	Filing Date	Patent Number	Issue Date
	10639112	Aug., 2003	6868322
	09799310	Mar., 2001	6631316

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Current U.S. Class:	701/36 ; 250/208.1
Current International Class:	G06F 7/00 (20060101); H01L 27/00 (20060101)
Field of Search:	701/36,49 250/208.1 359/111

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Primary Examiner: Beaulieu; Y.
Attorney, Agent or Firm: Price, Heneveld, Cooper, Dewitt & Litton, LLP Shultz, Jr.; James E.

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Parent Case Text

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 10/639,112, filed Aug. 12, 2003, now U.S. Pat. No. 6,868,322 which is a continuation of U.S. patent application Ser. No. 09/799,310, filed Mar. 5, 2001, now U.S. Pat. No. 6,631,316, the entire disclosures of which are incorporated herein by reference.

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Claims

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What is claimed is:

1. An imaging system for a vehicle, comprising: at least one image array sensor and a control circuit, said control circuit is in communication with said at least one image array sensor via a bus, wherein the imaging system is configured for use in a vehicle system selected from the group comprising: a headlamp control, an electrochromic mirror control, an information display, a rain sensor, a collision avoidance system, an adaptive cruise control, a lane departure warning system and a climate control system.

2. An imaging system as in claim 1 wherein said bus is a serial interface.

3. An imaging system as in claim 2 wherein said serial interface is a three wire serial interface which communicates image exposure instruction from said control circuit to a timing and control circuit and communicates image data from said image array sensor to said control circuit.

4. An imaging system as in claim 1 wherein said bus is a parallel bus.

5. An imaging system as in claim 4 wherein said bus is configured to communicate image data with image control parameters on the same signal lines.

6. An imaging system as in claim 4 wherein said bus is configured to communicate image data on separate lines from image control parameters.

7. An imaging system as in claim 1 wherein said bus is selected from the group comprising: analog signals configured as a common NTSC video signal, a MOST bus, an IEEE-1394 bus, a CAN bus, and a bus that conforms to the AMI-C specification.

8. An imaging system as in claim 1 wherein said control circuit comprises a first microprocessor and a second microprocessor, wherein said at least one image sensor is in communication with said first microprocessor via a first bus and said first microprocessor is in communication with said second microprocessor via a second bus.

9. An imaging system as in claim 8 wherein said first bus is a parallel bus and said second bus is a serial bus.

10. An imaging system as in claim 1 wherein said control circuit is configured to analyze at least one image as a function of a digital filter.

11. An imaging system as in claim 1 comprising at least two vehicle systems configured to share at least one device selected from the group comprising: a power supply, a light sensor and a microcontroller.

12. An imaging system for a vehicle, comprising: a control circuit configured to analyze at least one image as a function of a digital filter, wherein the imaging system is configured for use in a vehicle system selected from the group comprising: a headlamp control, an electrochromic mirror control, an information display, a collision avoidance system, an adaptive cruise control, a lane departure warning system and a climate control system.

13. An imaging system as in claim 12 wherein said digital filter is a matrix of coefficients to multiply pixels in a region surrounding the current pixel in order to obtain information about the pixel.

14. An imaging system as in claim 12 wherein said digital filter is configured to quantify frequency components of at least one image.

15. An imaging system as in claim 12 further comprising at least one image array sensor, wherein said at least one image array sensor in communication with said control circuit over a bus.

16. An imaging system as in claim 15 wherein said bus is a serial interface.

17. An imaging system as in claim 16 wherein said serial interface is a three wire serial interface which communicates image exposure instruction from said control circuit to a timing and control circuit and communicates image data from said image array sensor to said control circuit.

18. An imaging system as in claim 15 wherein said bus is a parallel bus.

19. An imaging system as in claim 18 wherein said bus is configured to communicate image data with image control parameters on the same signal lines.

20. An imaging system as in claim 18 wherein said bus is configured to communicate image data on separate lines from image control parameters.

21. An imaging system as in claim 15 wherein said bus is selected from the group comprising: analog signals configured as a common NTSC video signal, a MOST bus, an IEEE-1394 bus, a CAN bus, and a bus that conforms to the AMI-C specification.

22. An imaging system as in claim 15 wherein said control circuit comprises a first microprocessor and a second microprocessor, wherein said at least one image sensor is in communication with said first microprocessor via a first bus and said first microprocessor is in communication with said second microprocessor via a second bus.

23. An imaging system as in claim 22 wherein said first bus is a parallel bus and said second bus is a serial bus.

24. An imaging system as in claim 12 comprising at least two vehicle systems configured to share at least one device selected from the group comprising: a power supply, a light sensor and a microcontroller.

25. An imaging system for a vehicle, comprising: at least one device selected from the group comprising: a power supply, a light sensor and a microcontroller, wherein the imaging system is configured for use in a vehicle system selected from the group comprising: a headlamp control, an electrochromic mirror control, an information display, a rain sensor, a collision avoidance system, an adaptive cruise control, a lane departure warning system and a climate control system, at least two of said vehicle systems are configured to share at least one device selected from the group comprising: a power supply, a light sensor and a microcontroller.

26. An imaging system as in claim 25 further comprising at least one image array sensor and a control circuit in communication with one another over a bus.

27. An imaging system as in claim 26 wherein said bus is a serial interface.

28. An imaging system as in claim 27 wherein said serial interface is a three wire serial interface which communicates image exposure instruction from said control circuit to a timing and control circuit and communicates image data from said image array sensor to said control circuit.

29. An imaging system as in claim 26 wherein said bus is a parallel bus.

30. An imaging system as in claim 29 wherein said bus is configured to communicate image data with image control parameters on the same signal lines.

31. An imaging system as in claim 29 wherein said bus is configured to communicate image data on separate lines from image control parameters.

32. An imaging system as in claim 26 wherein said bus is selected from the group comprising: analog signals configured as a common NTSC video signal, a MOST bus, an IEEE-1394 bus, a CAN bus, and a bus that conforms to the AMI-C specification.

33. An imaging system as in claim 26 wherein said control circuit comprises a first microprocessor and a second microprocessor, wherein said at least one image sensor is in communication with said first microprocessor via a first bus and said first microprocessor is in communication with said second microprocessor via a second bus.

34. An imaging system as in claim 33 wherein said first bus is a parallel bus and said second bus is a serial bus.

35. An imaging system as in claim 26 wherein said control circuit is configured to analyze at least one image as a function of a digital filter.

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Description

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BACKGROUND OF THE INVENTION

The present invention generally relates to image processing systems, and more particularly, to image processing systems used to control vehicle equipment, such as vehicle headlamps, windshield wipers, etc.

Recently, many vehicular control accessories utilizing image processing systems have been proposed. For example, U.S. Pat. No. 5,837,994 entitled "Control System to Automatically Dim Vehicle Head Lamps," commonly assigned with the present invention and hereby incorporated by reference, discloses a control system which utilizes an image sensor and a processor to detect the headlamps of other vehicles at night and automatically control the state of the high beam headlamps of a vehicle. Another example of an image processing system to control vehicle equipment is given in U.S. Pat. No. 5,923,027 entitled "Moisture Sensor and Windshield Fog Detector," also commonly assigned with the present invention and hereby incorporated by reference. This patent discloses an image processing system, which acquires images of a vehicle windshield in order to detect the presence of rain or fog.

In each of these systems, as well as several other disclosed automotive image processing systems (see, for example, U.S. Pat. Nos. 5,765,116, 5,675,489, and 5,660,454 and PCT Published Patent Application No. WO 00/53465), images are acquired by an image sensor and stored into a memory in their entirety for subsequent processing. While technically very convenient, the use of this amount of image memory presents problems when adapting the system for commercial use, especially in the highly cost-sensitive automotive market. Most low cost microcontrollers or digital signal processors (DSPs) suitable for these types of applications are equipped with only a few hundred bytes to a few kilobytes of random access memory (RAM) into which the images can be stored. The processing core of many microcontrollers is typically available with a variety of RAM configurations, with the price increasing as the amount of memory increases. Therefore, it is advantageous to use a microcontroller with the least amount of RAM possible. The use of a small amount of RAM in prior art systems limits the size of the image, which can be stored and thus greatly limits the resolution.

A common off-the-shelf image sensor may have 352.times.288 pixels, known as the CIF format. Storing an entire image from this sensor requires approximately 100 kilobytes of RAM--far more than is typically available on a low cost microcontroller. Some microcontrollers have the ability to increase the amount of RAM available by the addition of an external memory chip. These microcontrollers must have an external memory bus, increasing the pin count and thus the cost and complexity of the microcontroller and the circuit board to which it is attached. The cost of the external memory itself must also be considered, and despite rapid memory price declines, this cost is anticipated to remain significant for some time to come. Finally, if an image must be transferred to memory before it can be processed, the total time required to acquire and analyze an image will be greater than if the analysis could occur simultaneously with the acquisition.

What is needed is a low cost image processing system to control automotive equipment which is capable of analyzing images without first storing them to memory, thus reducing the total amount of memory required in the system.

SUMMARY OF THE PRESENT INVENTION

The present invention solves the problem of the prior art by providing an image processing system, which does not require a memory with enough storage locations to store the digital grayscale value of every pixel in the image. The system contains an image sensor array containing a plurality of pixels, each of which is configured to provide an output indicative of the amount of light received by the pixel over the exposure time. The system also provides an analog-to-digital (A/D) converter to quantize the signal from the pixel into a digital grayscale value. The system also provides a processor in communication with the image sensor and A/D converter to analyze the images acquired by the image processor and control vehicle equipment based upon the results of processing the images. Finally, the system contains a memory for storing the grayscale value of some of the pixels and for storing other data used by the processor. By providing an image processing system with less available memory than is needed to store all pixels, the cost and the complexity of the image processing system can be reduced.

According to one aspect of the present invention, the amount of memory required is reduced by acquiring and analyzing only a portion of the image at a given time. This may be accomplished by acquiring a single row of pixels at a time or by acquiring a subwindow of pixels, which is a subset of the window containing all the pixels.

In another aspect of the present invention, a digital image processing filter is implemented by only storing a most recent group of pixels and performing the filter algorithm on this group of pixels. The most recent group of pixels may be, for example, the last few rows of the image received. The system performs the filter algorithm on the last few acquired rows and discards the oldest row as a new row is acquired.

In another aspect of the invention, some of the pixel values received by the processor are discarded as they are received and only a subset of the values is stored in the memory. Pixels may be discarded at a uniform rate throughout the image or at a non-uniform rate. For example, pixels may be discarded at a high rate near the periphery of the image and at a low or zero rate near the center of the image to provide a greater resolution near the center of the image.

In another aspect of the invention, the values of adjacent pixels may be averaged with one another and a single value stored in memory representing the average of several adjacent pixels. The number of pixels averaged with each other may be uniform throughout the image or may be non-uniform. Many pixels may be averaged with each other near the periphery of the image and few or zero pixels may be averaged with each other near the center of the image to provide a greater resolution near the center of the image.

In another aspect of the invention, objects identified in the image may be extracted from the image and stored as the image is being acquired. For example, the present invention may be used to identify headlamps of oncoming vehicles in order to determine the high beam state of the headlamps of the controlled vehicle. The present invention can identify the presence of an oncoming headlamp in the image as it is being acquired and store various information about the headlamp in an object list.

In another aspect of the present invention, the image data may be compressed as it is being acquired. This compression is accomplished by many ways including reducing the number of quantization levels (bit depth) of a pixel value as it is being received. Reducing bit depth of the image may be performed either uniformly or non-uniformly across the image and by requantizing either linearly or non-linearly. This aspect of the present invention is particularly useful for reducing data rate when the camera is positioned away from the processor.

In another aspect of the present invention, image data is reduced by storing segments of connected pixels, which together make up an object of interest. For example, a string of connected pixels in one row of an image, all with grayscale values above a threshold, may be stored as one object. Rather than storing the grayscale values of each pixel, only the starting and ending pixels and the cumulative grayscale value of all the pixels are stored. In a color implementation, the average color of the segment may be stored. Finally, two dimensional groups of objects may also be stored. This aspect is particularly useful for greatly reducing the memory requirements and transmitting image data with the least possible overhead. The processing to reduce the image to a list of segments may be contained in the image sensor itself, in a companion processor (ASIC, microcontroller, DSP or the like) near the image sensor, or in the main processor.

In another aspect of the present invention a color image sensor is used to detect color information about an object in the scene. In this embodiment, multi-layer thin film interference filters are placed over each pixel in a checkerboard or mosaic pattern such that adjacent pixels are exposed to different spectral bands of light. The use of multi-layer thin film interference filters allows the implementation of a color imaging system in an automotive environment. Typical polymer color filters would be degraded by direct focusing of the sun onto the array which will occur when the vehicle is traveling or is parked such that the camera is in direct view of the sun.

To achieve these and other aspects and advantages, the imaging system of the present invention comprises an image array sensor including a plurality of pixels, each of the pixels is operable to generate a signal indicative of the amount of light received on the pixel; an analog to digital converter for quantizing the signals from the pixels into a digital value; and a memory including a plurality of allocated storage locations for storing the digital values from the analog to digital converter, wherein the number of storage locations in the allocated memory is less than the number of pixels in the image array sensor.

According to another embodiment of the present invention, a control system is provided to control the headlamps of a vehicle. The control system comprises: an image array sensor including a plurality of pixels, each of the pixels is operable to generate a signal indicative of the amount of light received on the pixel; an optical system configured to image the scene forward of the controlled vehicle onto the image array sensor; an analog to digital converter for quantizing the signals from the pixels into a digital value; and a control circuit for processing the image of the scene obtained from the imaging system and for controlling the brightness of the headlamps in response to objects detected in the processed scene. The control circuit including a memory including a plurality of allocated storage locations for storing the digital values from the analog to digital converter, wherein the number of allocated storage locations in the memory is less than the number of pixels in the image array sensor.

According to yet another embodiment of the present invention, a control system is provided to control the headlamps of a vehicle. The control system comprises: an image array sensor including a plurality of pixels, each of the pixels is operable to generate a signal indicative of the amount of light received on the pixel; an optical system configured to image the scene forward of the controlled vehicle onto the image array sensor; and a control circuit for processing the image of the scene obtained from the imaging system and for controlling the brightness of the headlamps in response to objects detected in the processed scene, wherein the control circuit generates a segment list identifying segments of adjacent ones of the pixels that generate a signal having a grayscale value above a threshold as the signals are received from the pixels.

According to another embodiment of the present invention, an inside rearview mirror assembly for a vehicle comprises: a mirror mount adapted to be mounted inside the vehicle in a location proximate to or on the front windshield of the vehicle; a mirror bezel coupled to the mirror mount; a mirror mounted in the mirror bezel; an imaging system mounted to the mirror mount and configured to image the scene forward of the vehicle; and a control circuit electrically coupled to the imaging system for processing the image of the scene obtained from the image array sensor and for performing predetermined function in response to objects detected in the processed scene, wherein at least a portion of the control circuit is mounted to the mirror mount.

According to still another embodiment of the present invention, an imaging system for a vehicle is provided that comprises: an image array sensor; an optical system configured to image the scene forward of the controlled vehicle onto the image array sensor; and a control circuit coupled to the image array sensor for processing the image of the scene obtained from the image array sensor to control the vehicle headlamps in response to objects detected in the processed scene, the control circuit further processes the scene obtained from the image array sensor to perform at least one of the following functions: (a) to generate a collision avoidance warning; (b) to control the speed of the vehicle; and (c) to generate a lane departure indication signal.

These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is an electrical circuit diagram in block form showing the image processing system 100 of the present invention;

FIG. 2 is a cross-sectional view of a rearview mirror assembly in which the image processing system of the present invention may be implemented;

FIG. 3 is a flow chart illustrating the image reading and processing portion of the first embodiment that develops the segment list;

FIGS. 4A and 4B are a flow chart illustrating the image reception and processing phase by which an object list is created in accordance with a first embodiment of the present invention; and

FIGS. 5A and 5B are a block diagram illustrating the flow of data in accordance with an image processing routine according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Referring to FIG. 1, the image processing system 100 of the present invention includes at least one image array sensor 101. The image array sensor may be of a variety of types such as a CMOS active pixel sensor, a Charge Coupled Device (CCD), or any other type of electronic image sensor capable of sensing light in the visible, UV, near-IR or far-IR spectral bands. The image sensor 101 contains an array of pixels 102 onto which an image of a scene is formed by a lens. The pixels are exposed to light over a predetermined exposure time after which a voltage signal is present on the pixel indicative of the amount of light received. This voltage is then quantized by the A/D converter 103 resulting in a digital grayscale value indicative of the amount of light received on the pixel. A/D converters for this purpose typically quantize the pixel signals into 256 levels or 8 bits. However, different bit depths are frequently used and applicable to the present invention. Timing and control circuitry 104 provides all the signaling and timing necessary to operate the image sensor and transmit grayscale values to processor 105. An example of timing and control circuitry suitable for the present invention is given in U.S. Pat. No. 5,990,469 entitled "Control Circuit for Image Array Sensors" to Bechtel et al., commonly assigned with the present invention and hereby incorporated by reference.

Images acquired by image sensor 101 are transmitted to the processor 105 over bus 107. The processor 105 may be of a variety of types such as a microcontroller, digital signal processor (DSP), field programmable gate array (FPGA), application specific integrated circuit (ASIC),