Vehicular imaging system with selective infrared filtering and supplemental illumination

An imaging system for use in an exterior or interior of a vehicle comprises a camera having an image sensor with an associated optical path and viewing area and an infrared filter associated with the image sensor for automatically selectively attenuating infrared radiation according to light conditions of the viewing area. The imaging system can further comprise a selectively acutable supplemental illumination system comprising at least one light source for providing supplemental illumination to the viewing area of the camera.

FIELD OF THE INVENTION

The invention relates generally to vehicular imaging systems. In one of its aspects, the invention relates to a vehicular imaging system with selective infrared filtering. In another of its aspects, the invention relates to a vehicle imaging system and a supplemental illumination system. In yet another of its aspects, the invention relates to a vehicle imaging system with selective infrared filtering and supplemental illumination.

DESCRIPTION OF THE RELATED ART

In the automotive industry, there is an ongoing effort to improve the overall safety of vehicles during operation and to develop technology to prevent accidents from occurring. Numerous collisions, whether involving only one vehicle or between two or more vehicles, can be caused by the driver's inadequate view of the rear environment of the automobile while backing up, parallel parking, changing lanes, etc. The driver might not have the rear and side view mirrors properly oriented, and even if the mirrors are in the correct positions, there are often umbral regions or “blind spots,” such as on the side of the vehicle, behind the rear corners of the vehicle, or the area directly behind the vehicle and near the ground, that are not within the driver's field of view. As a result, the driver might not be able to see other vehicles, humans, animals, or inanimate objects that lie in the direction of travel of the automobile. One solution to this problem is to strategically position a digital video camera on the vehicle and provide a small display in the cabin for the driver. Such cameras can also be used to observe a trailer located at the rear of the vehicle and to view and monitor children inside the vehicle.

Vehicular digital cameras comprise image sensors, such as a charge coupled device (CCD) or a complimentary metal oxide semiconductor (CMOS), comprising a collection of light-sensitive diodes that convert photons or light into a voltage or current, which are ultimately converted into an image. Each pixel on the sensor has an associated exposure or integration time, which corresponds to the duration that the pixels are exposed to light and can range from microseconds to seconds depending on the sensor and configuration. An exposure register internal to the sensor represents these integration times by an integer value (1.255 for 8-bit systems). The corresponding voltage(s) or current(s) from the sensor are amplified before being converted to a digital representation. In the amplifier, each pixel(s) voltage or current equivalent is subjected to a multiplier, increasing its value, which is also referred to as gain. The amount of gain applied is determined by an Automatic Gain Control (AGC) algorithm to ultimately produce a high-quality, useful image. The gain changes according to the light conditions and is a function of the exposure. For example, in low light conditions, if the exposure reaches 255 and the image is still dark, then the gain is increased to effectively brighten the pixels to produce an image that can be discerned by the viewer. If the gain doubles, the exposure is reduced to one-half of its previous value. Because the gain is applied to the all of the pixels, including the noise, the gain is preferably low, such as 1, but in some low light conditions, as provided in the above example, the gain must be increased to produce a visible image. Hence, the AGC applies and modifies the gain by compromising between the image fidelity and useful images.

Imaging sensors require sufficient light to capture clear, high-quality images. The CCD cameras do not require as much light as CMOS cameras, but the CCD cameras are inadequately sized for preferred placement in or on the vehicle and are often too expensive for vehicular applications. The CMOS cameras are generally smaller in size than the CCD technology cameras and are relatively less costly to manufacture. However, one disadvantage of a CMOS image sensor is its low light sensitivity. Generally, CMOS sensors are less effective in poor or low light situations and, therefore, require greater illumination to produce an image with acceptable clarity. Further, standard rear lighting systems, such as tail lamps, light bars for illuminating the license plate, and center high mounted stop lamps (CHMSL), do not provide sufficient illumination for CMOS and other low-cost cameras over the complete targeted area.

Another problem with image sensors results from exposure to infrared (IR) radiation during high light conditions. IR radiation, which is present in sunlight and in certain types of artificial light, is typically undesirable for imaging in normal daylight conditions because it tends to wash out the colors and renders the images unclear. To thwart this effect, cameras can include a filter that attenuates near-IR and IR radiation to thereby prevent transmission thereof to the image sensor. However, when ambient light levels are low, such as during the night or on cloudy days, IR radiation actually improves image quality; therefore, transmission of IR radiation to the image sensor under these conditions is highly desirable. CMOS and CCD image sensors are very efficient in the IR and near-IR wavelengths and produce higher quality images in low light conditions when they are exposed to IR radiation.

SUMMARY OF THE INVENTION

In one aspect, an imaging system for use in an exterior or interior of a vehicle comprises a camera having an image sensor with an associated optical path and an infrared filter associated with the image sensor for attenuating infrared radiation. The infrared filter is movable from a first position, wherein the infrared filter is disposed in the optical path of the image sensor for preventing transmission of the infrared radiation to the image sensor, and a second position, wherein the infrared filter is spaced from the optical path of the image sensor and does not prevent transmission of the infrared radiation to the image sensor.

The infrared filter can move as a result of an output of the camera, wherein the output is indicative of light conditions in a viewing area of the camera. The output can be a gain determined by an Automatic Gain Control, a value representative of a gain determined by an Automatic Gain Control, an exposure, or a white balance. When the output is less than a first threshold, the infrared filter is in the first position, and when the output is greater than a second threshold, the infrared filter is in the second position. The second threshold is greater than the first threshold, and the second threshold can be twice the first threshold.

The infrared filter can automatically move between the first position and the second position as a result of light conditions in a viewing area of the camera. The imaging system can further comprise a solenoid that moves the infrared filter between the first position and the second position. Alternatively, the infrared filter can be manually moved between the first position and the second position.

The camera can further comprise an infrared filter holder for mounting the infrared filter to the camera. The infrared filter holder can pivot relative to the image sensor to move the infrared filter between the first position and the second position. The image sensor comprises a focal length, and the infrared filter preferably has a thickness that does not substantially change the focal length of the image sensor as the infrared filter moves between the first position and the second position.

The imaging system can further comprise a supplemental illumination system comprising at least one light source for providing supplemental illumination to a viewing area of the camera. The at least one light source can comprise a light emitting diode. The light emitting diode can be an infrared light emitting diode, a white light emitting diode, or a colored light emitting diode. The camera and the supplemental illumination system can form a unitary module.

The vehicle can comprise a license plate lightbar, and the supplemental illumination system can be mounted to the lightbar. The vehicle can comprise a center high mount stop lamp, and the supplemental illumination system can be mounted to the center high mount stop lamp. The vehicle can comprise at least one tail lamp, and the supplemental illumination system can be mounted to the at least one tail lamp. The at least one light source can be directed rearwardly of the vehicle.

The supplemental illumination system can be selectively actuable when the imaging system is activated. The supplemental illumination system can be selectively actuable when the infrared filter is automatically positioned in one of the first position and the second position in accordance with light conditions in a viewing area of the camera.

The image sensor is preferably a complimentary metal oxide semiconductor. The infrared radiation can comprise wavelengths between about 700 nm and 1 mm, and the infrared radiation can comprise near-infrared radiation.

In another aspect, an imaging system for use in an exterior or interior of a vehicle comprises a camera having an image sensor with an associated optical path and viewing area and an infrared filter positioned in the optical path of the image sensor for selectively attenuating infrared radiation, and the attenuation of the infrared radiation by the infrared filter is a function of ultraviolet radiation in the viewing area. The infrared filter can attenuate the infrared radiation when intensity of the ultraviolet radiation in the viewing area is above a predetermined value and can transmit the infrared radiation when the intensity of the ultraviolet radiation in the viewing area is below a predetermined value.

The infrared filter can comprises a photochromic coating. The photochromic coating can comprise tungsten hexacarbonyl. The photochromic coating can be disposed on the image sensor. The camera can further comprise a glass element in front of the image sensor, and the photochromic coating can be disposed on the glass element. The camera can further comprise a second glass element laminated to the glass element, and the photochromic coating can be disposed on the second glass element. The camera can further comprise a camera lens, and the photochromic coating can be disposed on the camera lens. The camera lens can comprise several lens elements, and the photochromic coating can be disposed between adjacent lens elements. The camera lens can comprise an outermost lens element, and the photochromic coating can be disposed on the outermost lens element. The imaging system can further comprise a housing for the camera, and the photochromic coating can be applied to the housing. The housing can comprises a housing lens, and the photochromic coating can be applied to the housing lens. The imaging system can further comprise a glass piece mounted to the housing, and the photochromic coating can be applied to the glass piece.

In yet another aspect, an imaging system for use in an exterior or interior of a vehicle comprises a camera having an image sensor with an associated optical path and viewing area and an infrared filter associated with the image sensor for selectively attenuating infrared radiation, and the infrared filter is automatically responsive to light conditions in the viewing area such that the infrared filter prevents the image sensor from being exposed to infrared radiation when light conditions in the viewing area correspond to daylight conditions and does not prevent the image sensor from being exposed to infrared radiation when the light conditions in the viewing area correspond to low light conditions.

The infrared filter can be permanently disposed in the optical path. The attenuation of the infrared radiation by the infrared filter can be a function of ultraviolet radiation in the viewing area. The infrared filter can attenuate the infrared radiation when intensity of the ultraviolet radiation in the viewing area is above a predetermined value characteristic of daylight conditions and can transmit the infrared radiation when the intensity of the ultraviolet radiation in the viewing area is below a predetermined value characteristic of low light conditions.

The infrared filter can be movable from a first position, wherein the infrared filter is disposed in the optical path of the image sensor for preventing transmission of the infrared radiation to the image sensor, and a second position, wherein the infrared filter is spaced from the optical path of the image sensor and does not prevent transmission of the infrared radiation to the image sensor. The infrared filter can move as a result of an output of the camera, wherein the output is indicative of light conditions in a viewing area of the camera. The output can be a gain determined by an Automatic Gain Control or a value representative of a gain determined by an Automatic Gain Control. When the output is less than a first threshold, the infrared filter is in the first position, and when the output is greater than a second threshold, the infrared filter is in the second position. The second threshold is greater than the first threshold, and the second threshold can be twice the first threshold.

The imaging system can further comprise a supplemental illumination system comprising at least one light source for providing supplemental illumination to the viewing area of the camera. The at least one light source can comprise a light emitting diode. The supplemental illumination system can be selectively actuable when the imaging system is activated.

DETAILED DESCRIPTION OF THE INVENTION

The invention addresses the problems of the prior art by providing a vehicular imaging system with an infrared (IR) filter located in the optical path of a image sensor and movable out of the optical path of the image sensor. Preferably, the IR filter is automatically moved relative the optical path of the image sensor. For example, the IR filter can be moved in response to a image sensor output that is indicative of the lighting conditions in the image sensor environment, such as a gain applied to pixels of the image. Alternatively, the IR filter is a photochromic IR filter and is transparent to infrared radiation in the absence of ultraviolet (UV) light, such as during the night or cloudy days. When exposed to UV rays, as in direct sunlight, the photochromic IR filter undergoes a chemical change and, as a result, absorbs and thereby filters IR radiation. The degree to which IR radiation is filtered can vary with the intensity of the UV rays. Because IR radiation is essential when ambient light levels are low and undesired during normal daylight conditions, the movable IR filter and the photochromic IR filter automatically ensure optimal lighting conditions for the image sensor.

To alleviate the lighting problems associated with using complimentary metal oxide semiconductor (CMOS) cameras or other similar cameras for vehicle imaging systems, the invention provides a supplemental illumination system to illuminate the camera viewing area. Although CMOS cameras are shown and discussed herein as a preferred embodiment, it will be understood that a charge coupled device (CCD) camera, CMOS camera, or any other camera or other suitable imaging device can be employed without departing from the scope of this invention.

As seen inFIG. 1, a vehicle10, e.g., a minivan shown in the exemplary embodiment ofFIG. 1, having side doors12and a rear door14with a rear window15is equipped with rear lighting components, for example a lightbar16, tail lamps18, and a center high mount stop lamp (CHMSL)20. The lightbar16is a generally elongated member mounted near the center of the rear door14and provides illumination, typically with incandescent light bulbs, to a license plate, a door handle, or other items disposed beneath the lightbar16. The tail lamps18are located on the rear of the vehicle10and are horizontally spaced from the rear door14. In general, the tail lamps18provide a visual indication of the motion of the vehicle10to pedestrians and other vehicles. For example, the tail lamps18can comprise a back-up lamp22, a brake lamp24, or a turn signal lamp26. Back-up lamps22are typically white, brake lamps24are required to be red, and turn signal lamps26can be red or amber. Now required by law to be present on all passenger cars and light trucks, the CHMSL20is effectively a brake light mounted on the vertical centerline of the vehicle10and no lower than three inches below the rear window15. The CHMSL20can be a standalone lamp or can be integrated into a horizontally extending vehicle body member28, as inFIG. 1.

The vehicle10is further equipped with a camera and supplemental illumination module30, which includes an imaging system and a supplemental illumination system and will be described in detail hereinafter, mounted by example to the rear surface of the vehicle10, such as to the lightbar16. The module30is in communication with a display32, preferably located in the interior of the vehicle10near the driver. When activated, the camera and supplemental illumination module30distributes light to nearby regions, as shown inFIGS. 2 and 3. For example, the module30can illuminate an area34immediately behind the vehicle10and having a width approximately equal to that of the vehicle10. The area34can extend to a predetermined distance, such as 12 feet or more, for example, behind the vehicle10, such as when the imaging system described herein is used in a back-up imaging function. With the presence of supplemental illumination, CMOS and other cameras having limited low light sensitivity can capture visible video images, which can be communicated to the display32and viewed by the driver in real time.

The camera and supplemental illumination module30can alternatively be located elsewhere on the vehicle10. For example, the module30can be positioned in the CHMSL20, as depicted inFIGS. 4 and 5. In this case, the CHMSL20is mounted above the rear window15, which provides a different, smaller viewing angle for the camera and supplemental illumination module30. With some cameras and imaging devices, a smaller viewing angle can relate to a reduction in visual distortion of the corresponding images provided on the display32. Similar to when the module30is mounted in the lightbar16, the camera and supplemental illumination module30supplies light to nearby regions, for example the area34covering approximately the width of the vehicle10and 12 feet behind the vehicle10. Alternatively, the module30can be positioned in any portion of the tail lamps18, for example in the back-up lamp22as shown inFIGS. 6 and 7. Again, when activated, the camera and supplemental illumination module30supplies light to nearby regions, such as the area34immediately behind the vehicle10and covering approximately the width of the vehicle10. The area34can extend to a predetermined distance, such as 12 feet, for example, behind the vehicle10, such as when the imaging system described herein is used in a back-up imaging function. The approximate relative size shown for the illumination areas34inFIGS. 2-7are only exemplary and other sizes and general shapes of areas can be illuminated, depending on the requirements of the imaging system of the camera and supplemental illumination module30. Other potential locations for mounting the camera and supplemental illumination module30include an external mirror, a door handle, a spoiler, or other decorative vehicular trim items.

As stated above, the camera and supplemental illumination module30comprises an imaging system and a supplemental illumination system. As depicted inFIGS. 8-12, the imaging system comprises a camera36, preferably a CMOS camera, and the supplemental illumination system comprises at least one light source38. When two light sources38are utilized, it is preferred that the camera36is positioned between the light sources38. The camera36and the light source38are mounted in an upper housing40and a lower housing42. The upper housing40or, alternatively, the lower housing42is in communication with an electrical connection50that can provide power to the camera36and the light source38and can provide communication between the module30, its control circuit, and the display32and/or between the module30and control circuits for the lightbar16, the tail lamps18, the CHMSL20, or other rear lighting components. The lower housing42comprises a bezel44and a lens46, and a light wall47to reflect light outward through the preferably clear lens46, to separate the light source42from the camera36, and to maintain the camera36at an angle. Additionally, a seal, such as a gasket48, extends along the periphery between the upper and lower housings40and42to prevent ingress of moisture, dust, debris, or any other material detrimental to the performance of the camera and supplemental illumination module30.

The lower housing42or, alternatively, the upper housing40further comprises means for mounting the module30to the lightbar16, tail lamps18, CHMSL20, or other suitable vehicle component. For example, in the case where the module30is mounted to a lightbar16, as shown inFIGS. 8-9, the lower housing42can comprise grooves52, one formed on each side thereof, that receive flanges54disposed on the sides of a module cavity56formed by the lightbar16and sized to receive the module30.

Referring particularly toFIG. 12, the camera36comprises an image sensor80mounted to a printed circuit board82, which is in communication with the electrical connection50. Preferably, the image sensor80includes at least one glass element84laminated thereto to protect the image sensor80from contamination. The camera36further comprises a camera lens86positioned in front of the image sensor80. The camera lens86is made of at least one and optionally several concave and/or convex glass and/or plastic elements. These shaped elements, as known to one skilled in the lens art, determine the optical properties of the camera lens86and can be engineered to optimize characteristics of the lens, such as field of view and percent distortion. A lens holder88houses the printed circuit board82, the image sensor80, and the camera lens86in a compact configuration.

The image sensor80can comprise any suitable sensor for acquiring and converting image data. Preferably, the image sensor80is a complimentary metal oxide semiconductor (CMOS) sensor, which can be manufactured with conventional semiconductor fabrication processes and equipment. Cameras having CMOS image sensors are generally smaller than other comparative cameras, but they typically have low light sensitivity. Another example of an image sensor80is a charge-coupled device (CCD) sensor, which is more expensive than a CMOS sensor but is a high-quality sensor in terms of fidelity and light sensitivity. Although a CMOS camera is shown and discussed herein as a preferred embodiment, it will be understood that any other camera, including a CCD camera, or other suitable imaging device can be employed without departing from the scope of this invention.

As discussed in the background of the invention, IR radiation, which is present in sunlight and in certain types of artificial light, is typically undesirable for imaging in normal daylight conditions because it tends to wash out colors and renders the images unclear. Conversely, when ambient light levels are low, such as during the night or on cloudy days, supplemental lighting in the near-IR or IR range is particularly effective in illuminating the camera viewing area with a wavelength that the sensor technology is very efficient with. To this end, the vehicular imaging system comprises an IR filter disposed in an optical path of the image sensor80.

The IR filter is preferably photochromic so that the amount of IR radiation it attenuates alters according to the intensity of ultraviolet (UV) radiation in its vicinity. When the UV ray intensity is below a predetermined value, or when UV rays are substantially absent, the IR filter transmits IR radiation, thereby exposing the image sensor80to IR illumination, such as illumination from supplementary IR light sources. On the other hand, when the UV ray intensity exceeds the predetermined value, such as in normal daylight conditions, the IR filter transmits visible light and significantly attenuates the IR radiation to thereby prevent the IR rays from negatively affecting the images acquired by the image sensor80. Further, the degree to which IR radiation is filtered can vary with the intensity of the UV rays; as UV radiation increases, IR radiation attenuation increases. Because of its photochromic behavior, the IR filter automatically activates when needed and does not require manual manipulation by a user.

The IR radiation attenuated by the active IR filter can lie within a suitable range of the electromagnetic (EM) spectrum. In general, the IR range in the EM spectrum is the wavelengths between red light and microwaves. The attenuated IR radiation can include near-IR radiation, which is a portion of the EM spectrum near red wavelengths. An exemplary range of IR filtration is wavelengths between about 700 nm and 1 mm.

The IR filter comprises a photochromic material and is preferably applied to the camera and supplemental illumination module30and any components thereof in the form of a coating. The coating comprises at least one layer having a thickness, variable or uniform, that effects the desired filtering characteristics. An exemplary IR filter material is disclosed in U.S. Pat. No. 4,069,168, which is incorporated herein by reference in its entirety. This material includes tungsten hexacarbonyl, which acts as a photochromic agent and an infrared absorber. The tungsten hexacarbonyl is incorporated in liquid allyl glycol carbonates and polymerizates thereof. Other materials exhibiting photochromic IR filtering characteristics can be utilized without departing from the scope of the invention. The exemplary material cited above is not intended to limit the invention in any manner. The IR filter coating can be applied to vehicular imaging system in any suitable manner and with any appropriate coating process.

The IR filter coating can be applied to several locations in and on the camera and supplemental illumination module30. The number of IR filter coatings and the quantity thereof can vary according to desired optical properties. The IR filter coating can be incorporated into the camera36and/or the lower housing42. Exemplary locations include, but are not limited to, directly on the image sensor80(i.e. between the image sensor80and the glass element84) or on the glass element84. Alternatively, a second piece of glass (not shown) can be laminated to the glass element84, and the IR filter coating can be applied to the second piece of glass. Further, the IR filter coating can be disposed on an element of the camera lens86. For example, the IR filter coating can be applied to the outermost element of the camera lens86, where it would ensure a good photochromic response and be sufficiently exposed to a light source. When the camera lens86comprises more than one element, the IR filter coating can be deposited on the surface of any element and between adjacent elements. The IR filter coating can optionally be applied to an inner or outer surface of the lens46in the lower housing42. Alternatively, the entire lower housing42can be made of a clear plastic material, and the IR filter coating can be deposited thereon. Optionally, the camera and supplemental illumination module30can comprise a separate glass piece90, as shown inFIG. 5, that is mounted to the lower housing42and serves as a substrate for the IR filter coating.

The light source38is preferably a small, low power device, such as a light emitting diode (LED). Furthermore, the LEDs for supplying illumination for the camera36are preferably white so that the image on the display32is a true representation of the viewing area of the camera36. Additionally, the white light sources38can be multi-functional and also serve to illuminate the region near the license plate when mounted in the lightbar16, as a back-up lamp when mounted in the tail lamps18, or as a task and/or security light to illuminate the adjacent vehicle environment. Alternatively, the LEDs can be infrared LEDs for use in low light conditions, and it is within the scope of the invention to employ another suitable source of illumination, such as organic LEDs (OLEDs) or incandescent or fluorescent light bulbs.

When the camera and supplemental illumination module30contains more than one light source38, a portion of the light sources38can be colored for other functionalities. For example, if the module30is mounted in the tail lamps18, the light source28can be red or amber and act as a brake light or a turn signal lamp. Additionally, a red light source28mounted in the CHMSL20can operate as a brake light. Provided that the lens46is clear, various combinations of colored light sources38can be assembled to create multi-functional camera and supplemental illumination modules30. For example, with a transparent and/or translucent light lens/filter/diffuser46, a plurality of red light emitting diodes can be provided for brake lamp functions, and a plurality of white light emitting diodes can be provided for both the back-up function as well as the supplemental illumination function for the imaging system described by example herein.

To assemble the camera and supplemental illumination module30, the camera36and the light source38are positioned in the upper housing40and are operably coupled with the electrical connection50. Next, the upper housing40is mounted to the lower housing42(preferably in a sealed watertight manner), and the assembled module30is then mounted to the desired location in the vehicle10. For example, when the module30is part of the lightbar16, the module30is positioned adjacent to the module cavity56in the lightbar16, the grooves52are aligned with the flanges54, and the module is slid onto the flanges54and into the module cavity56.

An alternative embodiment is shown inFIG. 13, where like objects are identified with like reference numerals. These figures illustrate a supplemental illumination module58that is identical to the camera and supplemental illumination module30except that the supplemental illumination module58does not contain the camera36. The supplemental illumination module58can contain any number of light sources38and can be mounted in any of the locations described herein for the camera and supplemental illumination module30.

Similarly, another alternative embodiment of the invention is shown inFIG. 14, where like objects are identified with like reference numerals. In this case, the module is a camera module60that is identical to the camera and supplemental illumination module30but does not comprise the light sources38. The camera module60likewise can be positioned in any of the locations described above for the camera and supplemental illumination module30. The camera module60can be sized to be mounted in locations that perhaps are not capable of housing an entire camera and supplemental illumination module30.

Another alternative embodiment is illustrated inFIGS. 15-18, where like objects are identified with the same reference numeral bearing a prime symbol (′). The embodiment shown inFIGS. 15-18is a camera module60′ comprising a camera36′ and an IR filter70in the form of a movable element that can be selectively removed from the optical path of the camera36′ during low light conditions. The IR filter70is preferably a very thin element or a coating applied to a very thin element so that the focal length of the camera36does not substantially change as the IR filter70moves out of the optical path. As in the first embodiment, the IR radiation attenuated by the IR filter70can lie within a suitable range of the electromagnetic (EM) spectrum. In general, the IR range in the EM spectrum is the wavelengths between red light and microwaves. The attenuated IR radiation can include near-IR radiation, which is a portion of the EM spectrum near red wavelengths. An exemplary range of IR filtration is wavelengths between about 700 nm and 1 mm.

The camera36is mounted within a front housing40′ and a rear housing42′, and, as in the previous embodiments, the front housing40′ or, alternatively, the rear housing42′ is in communication with an electrical connection (not shown) that can provide power to the camera36′ and communication between the camera module60′, its control circuit, and the display32and/or between the camera module60′ and control circuits for the lightbar16, the tail lamps18, the CHMSL20, or other rear lighting components. A seal, such as a gasket48′, extends along the periphery between the front and rear housings40′ and42′ to prevent ingress of moisture, dust, debris, or any other material detrimental to the performance of the camera36.

The camera36′ comprises an image sensor80′ mounted to a printed circuit board82′, which is in communication with the electrical connection. The camera36′ further comprises a camera lens86′ positioned in front of the image sensor80′. The camera lens86′ is made of at least one and optionally several concave and/or convex glass and/or plastic elements. These shaped elements, as known to one skilled in the lens art, determine the optical properties of the camera lens86′ and can be engineered to optimize characteristics of the camera lens86′, such as field of view and percent distortion. A lens holder88′ supports the camera lens86′ and mounts the camera lens86′ to the rear housing42′. The lens holder88′ defines a center aperture89axially aligned with the camera lens86′ and the with the image sensor80′. The optical path of the image sensor80′ extends from the image sensor80′, through the center aperture89of the lens holder88′, through the camera lens86′, and through the front housing40′ to the environment external of the camera module60′, as indicated by an arrow inFIG. 18.

The camera module60′ further comprises an IR filter holder72with a terminal frame74sized to receive the IR filter70. The frame74is disposed at the end of a support arm76having a pivot point in the form of a cylindrical boss78. As shown inFIGS. 15-17, the IR filter holder72can pivot about the boss78and relative to the lens holder88′ and to the printed circuit board82′ to move the IR filter70between a first position, as seen inFIG. 15, wherein the IR filter70is aligned with the center aperture89and in the optical path of the image sensor80′ to prevent transmission of IR wavelengths to the image sensor80′, and a second position, as shown inFIG. 16, wherein the IR filter70is spaced from the center aperture89and, thus, removed from the optical path of the image sensor80′ so that the image sensor80′ can receive IR radiation.

The camera module60′ includes a mechanism for automatically inducing the movement of the IR filter holder72. In this embodiment, the mechanism is a solenoid92mounted to the rear housing42′ and in operative communication with the boss78. Preferably, the solenoid92is in a non-powered state when the IR filter70is in the first position during daylight and bright conditions to reduce color washout that can result from IR radiation. Because the solenoid92defaults to the first position in the non-powered state, the IR filter70is in a safe state wherein the IR radiation is attenuated. The solenoid92activates during low light conditions, such as in the evening or at night, to move the IR filter holder72and, thus, the IR filter70to the second position so that the image sensor80′ is exposed to IR radiation for producing high quality, visible images. When daylight and bright conditions reemerge, the solenoid92returns the IR filter70to the first position. It will be apparent to one skilled in the imaging system art that mechanisms other than the solenoid92can be used to move the IR filter70between the first and second positions.

The solenoid92is controlled by a Microchip microprocessor that utilizes an algorithm employing an output of the camera36′ to determine when the IR filter70should be positioned in the optical path of the image sensor80′ or removed from the optical path of the image sensor80′ to optimize image quality. The output of the camera36′ that is used by the algorithm is indicative of the light conditions in the vicinity of the camera module60′. The output can be a numerical value or an ordinal indicator, a direct output of the image sensor80′, or an output that has been manipulated or produced by a processor or similar device in communication with the image sensor80′. The algorithm compares the output indicative of the light conditions to one or more predetermined threshold values and uses the relationship between the output and the one or more predetermined threshold values to control the activation of the solenoid92. For example, if the output reaches the one or more predetermined threshold values, which indicates that the light conditions have substantially changed, the microprocessor activates the solenoid92to either move the IR filter70from the first position to the second position or to return the IR filter70to the first position. Conversely, if the output indicates that the light conditions have not changed substantially, i.e., the output has not reached the one or more predetermine values, then the microprocessor does not activate the solenoid92, and, therefore, the IR filter70does not move from its current position.

Preferably, two threshold values are used to determine the conditions under which the solenoid92is activated to move the IR filter70. As schematically illustrated inFIG. 19, a first or daylight threshold value corresponds to the output value below which the IR filter is preferably positioned in the optical path of the image sensor80′ (if the output value is inversely proportional to the light conditions) or, alternatively, removed from the optical path of the image sensor80′ (if the output value is directly proportional to the light conditions). A second or low light threshold value corresponds to the output value above which the IR filter is preferably removed from the optical path of the image sensor80′ (if the output value is inversely proportional to the light conditions) or, alternatively, positioned in the optical path of the image sensor80′ (if the output value is directly proportional to the light conditions). The schematic illustration ofFIG. 19and the description that follows assumes that the output value is inversely proportional to the light conditions. The terms “daylight threshold value” and “low light threshold value” are utilized herein for explanatory purposes and are not meant to limit the invention in any manner. The “daylight threshold value” does not necessarily correspond to light conditions during a time period corresponding to daytime. Rather, “daylight” can refer to any light conditions that are similar to the light conditions present during typical daylight hours, and “daylight” can be produced with both natural and artificial lighting. In other words, “daylight” corresponds to the light conditions wherein the camera36′ requires the IR filter70to be in the first position in order to produce useable images. Similarly, “low light” corresponds to the light conditions wherein the camera36requires the IR filter70to be in the second position to produce useable images.

Utilizing the two threshold values creates a hysteresis between the daylight threshold value and the low light threshold value to prevent unnecessary rapid movement of the IR filter holder72and subsequent burnout of the solenoid92when the output is near the daylight threshold value or the low light threshold value. As the output increases from below the daylight threshold value and surpasses the daylight threshold value, the solenoid92does not activate until the output equals the low light threshold value. Conversely, as the output decreases from above the low light threshold value and falls below the low light threshold value, the solenoid does not move the IR filter holder72until the output equals the daylight threshold value.

The algorithm that incorporates the hysteresis described above is shown schematically in the flow chart ofFIG. 20. The algorithm begins by reading or polling the output in step102and then compares the output to the daylight threshold value in step104. If the output is equal to or less than the daylight threshold value, then the microprocessor determines in step106that the IR filter70must be in the optical path of the image sensor80′ and activates the solenoid92to move the IR filter70to the first position if it is not already in the first position. Conversely, if the output is not equal to or less than the daylight threshold value, then the microprocessor compares the output to the low light threshold value in step108. If the output is equal to or greater than the low light threshold value, then the microprocessor determines in step110that the IR filter70must be out of the optical path of the image sensor80′ and activates the solenoid92to move the IR filter70to the second position if it is not already in the second position. However, if the output is not greater than or equal to the low light threshold value, then the output resides within the hysteresis, and the position of the IR filter70is not changed. After steps106,110, or, if the output resides in the hysteresis, step108, the algorithm proceeds to step112, which is a delay of a predetermined duration ranging from zero to a desired maximum value. After the delay, the algorithm returns to step102and repeats. When the delay equals zero, the algorithm continuously repeats without a pause between each execution of the algorithm. Preferably, the delay is equal to approximately 300 ms.

Preferably, the output utilized in the algorithm is a gain (or a value derived from the gain) that is applied to the pixels as the signal from the image sensor80′ passes through an amplifier before being displayed as an image. The gain is a multiplying factor that essentially increases the brightness of the pixels to improve the image. As described in the background of the invention, the gain is a function of exposure and is determined by an Automatic Gain Control (AGC) algorithm. In general, the gain is inversely proportional to the light conditions and, thus, the gain increases in low light conditions. Hence, when the gain is equal to or less than the daylight threshold value, the light conditions are categorized as daylight or bright light, and the IR filter70must be in the first position. Conversely, when the gain is equal to or greater than the low light threshold value, the light conditions are characterized as low light, and the IR filter70must be in the second position. If the gain is between the daylight threshold value and the low light threshold value, then the gain is in the hysteresis. It will be apparent to one skilled in the imaging system art that outputs other than the gain can be used by the algorithm. Exemplary outputs include other camera settings or parameters, such as the exposure/integration time and a white balance.

The particular values for the daylight and low light threshold values are empirically determined and are selected to optimize image quality. When the output value is the gain, the daylight threshold value is preferably equal to or less than 2, and the low light threshold value is preferably greater than 1. For example, the daylight threshold value can be 1 or 2, while exemplary values for the low light threshold value are 2, 4, 8, or 16.

The algorithm can employ pixel metrics that are taken from the whole image or from particular regions of interest (ROI) within a field of view (FOV) of the image sensor80. Further, the algorithm can use multiple numbers of ROIs and different ROIs for pixel analysis that is based on the camera settings or parameters, including, but not limited to, gain, exposure, and white balance. Additionally, the pixels can be filtered within the ROI before deriving an average, and the filter can be linear, such as a simple average, or non-linear, such as a median. The image can also be pre-processed, such as by employing edge detection to determine a contrast ratio. The pixel metrics can include, but are not limited to, mean, median, correlation, minimum, maximum, standard deviation, and variance. Furthermore, the pixel metrics can be used independently or processed together in various combinations.

Each of the above embodiments of the invention can be employed alone or in various combinations thereof to engineer a vehicle imaging environment having ideal IR filtration and supplemental illumination. The camera and supplemental illumination module30can be utilized alone or, optionally, with any number of supplemental illumination modules58. Alternatively, the camera module60or60′ may be desired for certain applications where it can be used alone or, optionally, can be accompanied by one or more supplemental illumination modules58. Furthermore, the vehicle10can be equipped with more than one camera36, which can be in the form of more than one camera module60or60′, more than one camera and supplemental illumination module30, or combinations of the two types of modules60or60′ and30. When more than one module30,58,60, or60′ is employed, regardless of type, the modules30,58,60, or60′ can all be mounted in the same location or can be mounted in different locations. For example, the camera and supplemental illumination module30can be mounted in the lightbar16while the supplemental illumination modules58can be mounted in the tail lamps18. In short, any combination of the modules30,58,60, and60′ can be mounted in any suitable location on the vehicle10.

Referring now toFIG. 21, the operation of the vehicle equipped with at least one of the modules30,58,60, and60′ initiates when a driver of the vehicle10performs a function that involves the assistance of the imaging system and/or the supplemental illumination system, such as when attempting to parallel park without sufficient view of the umbral regions behind the vehicle10, towing a trailer behind the vehicle10, or monitoring the interior of the vehicle10behind the driver. The imaging system of the module30,60, or60′ is activated in step120such as by manual actuation by the vehicle driver from within the interior of the vehicle10and/or by automatic actuation such as by placement of the vehicle transmission into a reverse gear, thus indicating a condition where the vehicular imaging system would be used. Alternatively, the module30,60, or60′ can be equipped with sensors to detect objects within certain distance of the vehicle, and the module30,60, or60′ can be automatically activated when objects are within a predetermined distance of the vehicle10, i.e., another predetermined condition where the imaging system is designed to be used.

Once the module30,60, or60′ activates, the imaging system in step122runs the algorithm shown schematically inFIG. 20and described above to either maintain the IR filter70in the first position, to move the IR filter70to the second position, or to maintain the IR filter70in the second position, depending on the light conditions and the output indicative of the light conditions. As described above, the algorithm runs in a loop to update the position of the IR filter70based on any changes in the light conditions. Alternatively, if the IR filter is a photochromic IR filter, then IR filter automatically adjusts its IR attenuation according to the intensity of UV radiation in the vicinity of the IR filter. During normal daylight conditions when the UV radiation intensity is above the predetermined value, the photochromic IR filter transmits the visible light and attenuates the IR radiation such that the video images are clear and not affected by the IR radiation. During low light conditions when the UV radiation intensity is below the predetermined value, such as during the night or cloudy days, the photochromic IR filter transmits the IR radiation that illuminates the field of view of the image sensor80and increases the quality and visibility of the video images.

Next, the supplemental illumination system of the module30or58can be activated in step124such that the light source38illuminates the area34so that the camera36can capture visible video images of the desired regions. Alternatively, the imaging system can be utilized without the supplemental illumination system if the supplemental illumination is not necessary for the camera36to capture visible images. In some instances, the light conditions are bright enough such that the supplemental illumination is not needed, or the vehicle10produces adequate lighting for the imaging system. If the supplemental illumination system is utilized, then it is preferably activated after step122so that the supplemental illumination system does not interfere with activation of the IR filter70. Optionally, the supplemental illumination system can be adapted so that it cannot be activated until the algorithm for determining the position of the IR filter70has initiated or until the imaging system has been activated.

After the IR filter70is properly positioned and the supplemental illumination system is optionally activated, video images are communicated to the display32near the driver in step126to assist the driver in parking, towing a trailer, monitoring the interior of the vehicle10, and the like. After the driver no longer requires the assistance of the vehicular imaging system, the module30,58,60, or60′ is deactivated manually and/or automatically.

As an alternative to the photochromic IR filter coating or to the IR filter70that moves relative to the optical path of the image sensor80as a result of the output from the camera36, the IR filter can comprise a separate element, such as a thin glass or plastic element that is manually inserted into or removed from the optical path of the image sensor80or automatically moved relative to the optical path as a result of another parameter independent of the camera36, such as light sensors mounted to the module or to the vehicle10and in communication with the module. The IR filter can assume any form suitable for placement in the optical path of the image sensor80. Additionally, any of the components of the camera36that are in the optical path of the image sensor80can have an IR filter integral therewith or embedded therein to eliminate the need for a separate coating or IR filter element. Further, it is within the scope of the invention for the IR filter to be located along the optical path of a image sensor disposed in another type of module or housing other than those described above.

The modules30,58,60, and60′ according to the current invention offer several advantages. The modules provide a cost-effective solution to the low light sensitivity of CMOS and other similar cameras. Not only are the components inexpensive, but also the modules are relatively simple to manufacture and assemble. With a lower system cost, it is more likely that imaging systems and the safety-related benefits associated therewith will be incorporated into vehicles. Additionally, because the modules comprise a tight gasket seal and are snug fit into the lightbar or other vehicle components, they are extremely robust and resist potentially degrading environmental conditions. Furthermore, the modules are designed to be easily integrated with existing vehicle components; therefore, they do not detract from the aesthetic appearance of the vehicle and do not interfere with existing standard lighting systems.

The imaging system according to the invention can produce clean and visible video images in both daylight and low light conditions. Because the photochromic IR filter alters its IR attenuation according to the intensity of the UV radiation in its vicinity, the image sensor is automatically exposed to amount of IR radiation suitable for the lighting conditions in its field of view. Similarly, the IR filter that moves relative to the optical path of the image sensor as a result of an output of the camera automatically adjusts to the light conditions and to changes in the light conditions. Further, the hysteresis that is incorporated into the algorithm for moving the IR filter protects the mechanism for moving the IR filter and improves the performance of the imaging system.