Dynamic calibration of optical properties of a dimming element

An imager assembly including calibration functionality and a housing. An imager is disposed inside the housing. The imager includes a lens assembly. An electro-optic element is disposed on a wall of the housing and operable between a substantially clear condition and a substantially darkened condition. A light source directs light at the electro-optic element which redirects the light toward the lens assembly.

TECHNOLOGICAL FIELD

The present invention generally relates to imager assemblies and utilizing dynamic calibration assemblies to adjust optical properties of captured images.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, an imager assembly comprises a housing and an imager disposed inside the housing. The imager includes a lens assembly. An electro-optic element is disposed on a wall of the housing and is operable between a substantially clear condition and a substantially darkened condition. A light source directs light at the electro-optic element which redirects the light toward the lens assembly.

In another aspect of the present disclosure, a method of calibrating an imager assembly comprises positioning an imager to take images through an electro-optic element. The imager is synchronized with a light source such that every Nth frame is used as a calibration frame. The light source is activated during the calibration frame. An image is stored during activation of the light source and properties are compared with a baseline profile to determine color and intensity shift of the electro-optic element.

In yet another aspect of the present disclosure, a method of calibrating an imager assembly comprises positioning an imager to take images through an electro-optic element. The imager is aligned with the electro-optic element such that a dimming region and a calibration region are defined within a field of view of the imager. A color and intensity shift of the image is compared at the calibration region with a color and intensity shift of the image taken through the electro-optic element.

In yet another aspect of the present disclosure, an imager assembly comprises a housing and a primary imager disposed inside the housing. The primary imager includes a lens assembly. An electro-optic element is disposed adjacent to the lens assembly within the housing and is operable between a substantially clear condition and a substantially darkened condition. A calibration imager is disposed within the housing and is configured to collect image data from a calibration light source, wherein a portion of the electro-optic element is disposed between the calibration imager and the calibration light source.

In yet another aspect of the present invention, a method of calibrating an imager assembly comprises positioning a primary imager to take images through an electro-optic element. A calibration imager is positioned to take images of image data provided by a calibration light source through an electro-optic element. Properties of the image are compared with a baseline profile to determine color and intensity shift of the electro-optic element.

DETAILED DESCRIPTION

Referring toFIGS. 1-2, the reference numeral10generally designates an imager assembly that includes a housing12and an imager14disposed inside the housing12. The imager14includes a lens assembly16. An electro-optic element18is disposed on a wall20of the housing12and is operable between a generally clear condition and a generally darkened condition. A light source22directs light23at the electro-optic element18, and the electro-optic element18redirects the light toward the lens assembly16.

The housing12may be constructed from a variety of materials including metals and plastics, and may be disposed inside or outside of a vehicle24. As illustrated, the imager assembly constructions set forth herein may be disposed in a satellite antenna housing, behind a vehicle body panel, etc., and are not limited to the specific configurations illustrated herein. Although the imager assembly10includes a field of view26that is directed rearwardly, the field of view26could extend in any direction relative to the vehicle. In the illustrated embodiment, the wall20of the housing12includes an at least partially transmissive and partially reflective portion, which in the illustrated embodiment includes the electro-optic element18. The electro-optic element18includes first and second substrates34,36. The first substrate34defines a first surface38and a second surface40. The second substrate36defines a third surface42and a fourth surface44. An electro-optic medium46is disposed between the first substrate34, the second substrate36, and seals48are disposed about the dimming element. The third surface42and/or the fourth surface44may include a transflective coating to allow external light to pass into the housing12, but reflect internal light from the light source22. However, in some instances, the transflective coating may be on the first surface38or second surface40.

With reference again toFIG. 2, the light source22is disposed below the imager14and the lens assembly16. However, it will be understood that the light source22may be disposed at other areas within the housing12. Regardless, the light source22is generally configured to direct the light23at the electro-optic element18, which redirects the light toward the lens assembly16. The imager assembly10is generally configured such that the imager14is synchronized with the light source22, such that every Nth frame taken by the imager14is used as a calibration frame by a controller50and is not displayed to the user. The light source22is pulsed on during the calibration frame and image data is captured by the imager14. The controller50then compares a color of the image to a baseline image profile to determine if there has been any color or intensity shift of the electro-optic element18. An algorithm configured to compensate for color and intensity shift runs within a processor of the controller50that is in electrical communication with the imager14. The processor subsequently modifies the image data before being displayed to a user on a display module52. The display module may be positioned anywhere including inside the vehicle24at a rearview device54or dash56, or outside of the vehicle24.

With reference again toFIGS. 1-2, it will be understood that the Nth frame may be as frequent as every other frame taken by the imager14, but could also be as infrequent as every 30 seconds a frame is used for calibration. In addition, it is also contemplated that the sampling rate could be based on the voltage differential measured at the electro-optic element18. As the voltage differential increases, the sampling rate may increase as the electro-optic element18may be darkening or becoming more clear. In addition, it is generally contemplated that the sampling rate may be based on the time of day (dusk and dawn), the time of year, or the state of use of the vehicle (whether the vehicle is in drive, reverse, park, etc.).

A method of using calibration functionality of the imager assembly10includes positioning the imager14to take images through the electro-optic element18. The imager14is then synchronized with the light source22, such that every Nth frame is used as a calibration frame. The light source22is activated during each calibration frame. Image data is captured by the imager14and stored in memory during activation of the light source22, and properties of the image are compared with a baseline image profile to determine color and intensity shift of the electro-optic element18. As noted above, a transflective coating may be applied to one of the first, second, third, and fourth surfaces38,40,42,44of the first and second substrates34,36of the electro-optic element18to allow external light to pass into the housing12, but reflect internal light that is provided by the light source22. In addition, it is also contemplated that a reflective polarizer may be positioned adjacent to the electro-optic element18to allow light to pass into the housing12, but minimize light from leaving the housing12.

With reference now toFIGS. 3-7, in an alternate construction, an imager assembly100is illustrated that includes another manner of calibration. This configuration uses many of the same features as the previously described construction. It will be understood that like features include like references numerals across the various embodiments set forth in this disclosure. The imager assembly100also includes a lens assembly101and an electro-optic element102. The electro-optic element102includes a calibration region104, and a dimming region106separated by a seal107. The electro-optic medium46at the dimming region106and at the calibration region104may be constructed from the same or different materials. It is contemplated that the seal107may be generally clear in some applications. The calibration region104does not dim and is generally clear. In this instance, an imager108is positioned to capture image data through an electro-optic element102. The electro-optic element102may be positioned inside the housing12(FIG. 7) or may be positioned at an opening defined by the housing12(FIG. 3). Regardless, the imager108is aligned with the electro-optic element102, such that the dimming region106and the calibration region104define an area110that is aligned with the field of view26of the imager108. The calibration region104will likely be a small portion of the overall area110of the electro-optic element102. Depending on the application, the calibration region104may be on a top, bottom, or side of the electro-optic element102. In addition, the calibration region104may be positioned such that the calibration region104will not be visible on the display module52disposed within the vehicle24that provides image data to the user. The controller112compares a color and intensity shift of the image at the calibration region with a color and intensity shift of the image taken at the dimming region106of the electro-optic element102. The controller112may be positioned on a circuit board114. An algorithm is subsequently activated to modify the image based on the comparison of the calibration region104with the dimming region106. The modified image is then displayed on the display module52to a user.

With reference again toFIGS. 3-7, it will be understood that color and intensity shift properties of the dimming region106and the calibration region104may be stored in non-volatile memory of the imager108. This data may be recalled by the controller112that evaluates the color and intensity shift of the dimming region106and the calibration region104at a later time. The seal107may be disposed between the calibration region104and the dimming region106. In addition, a dead zone area120may be identified between the calibration region104and the dimming region106. Image data that is captured at the dead zone area120may be discarded by the controller112and not utilized in evaluating any color or intensity shift. In addition, the controller112in this construction may include real-time content aware identification of the suitability of pixels for use in calibration. Stated differently, the controller112may run an algorithm that measures for similarities and/or differences in the calibration and dimming regions104,106and these similarities and differences may be used for calibration of the dimming region106.

With reference now toFIG. 8, yet another configuration set forth in this disclosure includes an imager assembly200with calibration functionality. The imager assembly200includes a housing202, and a primary imager204disposed within the housing202. The primary imager204includes a lens assembly206and an electro-optic element208that is disposed adjacent to the lens assembly206. The electro-optic element208may include a structure similar to that of the electro-optic element18disclosed above and illustrated inFIG. 2. The electro-optic element208and the lens assembly206are disposed within the housing202behind a cover glass209. The electro-optic element208includes features similar to those set forth in relation to the electro-optic element18. The lens assembly206is disposed between the primary imager204and the electro-optic element208. The electro-optic element208is operable between a generally clear condition and a generally darkened or dim condition. A calibration imager210is also disposed within the housing202and is configured to collect image data from a calibration light source212. A portion of the electro-optic element208is disposed between the calibration imager210and the calibration light source212. In this instance, a periodic or continual calibration of the image data occurs based on image data collected by the calibration imager210. While the user is able to see image data collected by the primary imager204through the electro-optic element208, the image data is modified based on an algorithm that functions to modify the image before being displayed to a user based on image data collected by the calibration imager210. For example, in the event the primary imager204is being used in very bright, ambient conditions, the electro-optic element208will dim. As the electro-optic element208dims, the calibration light source212directs light through the electro-optic element208at the calibration imager210. If the color and intensity of the electro-optic element208shifts as noted by the calibration imager210, modifications can be made by the image data collected by the primary imager204before being displayed to the user.

With reference again toFIG. 8, the lens assembly206is shown between the primary imager204and the electro-optic element208. However, the electro-optic element208could also be positioned between the primary imager204and the lens assembly206. This construction for the imager assembly200would work similarly to the illustration ofFIG. 8, but image data would be adjusted based on light first passing through the lens assembly206, then the electro-optic element208before being captured by the primary imager204.

One method of calibrating the imager assembly201using the imager assembly200includes positioning the primary imager204to take images through the electro-optic element208. The calibration imager210also takes images of image data that is provided by the calibration light source212through the electro-optic element208. Properties of the image data are then compared with a baseline image profile to determine color and intensity shift of the electro-optic element208. The calibration functionality of the imager assembly200may utilize a separate calibration region220(between the calibration imager210and the calibration light source212) on the electro-optic element208to provide a reference for correction. The calibration region220is analyzed by a separate imaging device (the calibration imager210) altogether. An optical isolator222extends across the housing202and is interrupted by the electro-optic element208. The optical isolator222is configured to isolate the primary imager204, the lens assembly206, and a primary portion of the electro-optic element208from optical overlap with the calibration imager210and the calibration light source212. The purpose of the optical isolation is to prevent light from the calibration light source212from reaching the primary imager204and also to prevent external light from reaching the calibration imager210.

With reference now toFIGS. 9-11, an example of corrected images can be observed. Specifically, a baseline image is shown inFIG. 9. After the electro-optic element is dimmed, a color and intensity shift occurs as a result of the image data being collected through the electro-optic element (FIG. 10). After compensation, which is governed by an algorithm within a processor of the controller disposed within the imager assembly or elsewhere within the system, the image can be displayed to the user (FIG. 11).

The color correction applied in these techniques is configured to allow the presence of a dimming element as part of an imager stack-up without negatively affecting image quality. One application of this technique is to allow the dimming element to act as a gain factor in the imaging device to allow more flexibility and exposure control settings. Consequently, this can be used to improve dynamic range capabilities and allow for greater ability to mitigate the effect of time varying light sources on the imager.