DAZZLE RESILIENT VIDEO CAMERA OR VIDEO CAMERA MODULE

Abstract

Video camera or video camera module, comprising an RGB image sensor, a computer processor adapted to perform pre-processing followed by video compression, and a dazzle detector, characterised in responding to dazzle in one colour channel by reducing values in that colour channel prior to compressing the video data. This has the advantage that in the event of laser dazzle that is specific to a colour channel, the compressed video data generated will retain more detail from the other colour channels compared to a conventional camera.

Claims

1. Video camera or video camera module, having a field of view, comprising: An RGB, bayer filter, single chip image sensor, arranged to generate raw video data; A computer processor adapted to perform image processing on the raw RGB video data, comprising at least one pre-processing step, followed by post processing compression to provide compressed video data; A detector adapted to determine an excess of light in at least one RGB colour channel compared to the other RGB colour channel(s), that is consistent with laser dazzle from at least one type of laser, in at least part of the field of view of the video camera or video camera module, and to output to the computer processor a determination of at least one specified RGB colour channel as being subject to such excess of light, wherein the determination is either based on video data from the RGB sensor, or based on data from a light spectrum sensor or laser detector; Characterised in that: The computer processor is adapted to respond to the determination of an excess of light in at least one specified RGB colour channel by reducing values of the specified RGB colour channel(s) as at least part of the at least one pre-processing step in advance of the post processing compression.

2. Video camera or video camera module of claim 1 wherein the detector is adapted to determine an excess of light in one RGB colour channel compared to the other two, and adapted to determine an excess of light in two RGB colour channels compared to the other one.

3. Video camera or video camera module of claim 1 wherein the detector is adapted to determine the excess of light based on video data from the RGB sensor.

4. Video camera or video camera module of claim 1 wherein in reducing values of the specified RGB colour channel(s) as part of the at least one pre-processing step, the computer processor is adapted to reduce the values by at least 50% of their original values on average (mean) across at least part of the field of view of the video camera or video camera module.

5. Video camera or video camera module of claim 1 wherein in reducing values of the specified RGB colour channel(s) as part of the at least one pre-processing step, the computer processor is adapted to reduce each value by at least 75% of their original value, across at least part of the field of view of the video camera.

6. Video camera or video camera module of claim 1 wherein in reducing values of the specified RGB colour channel(s) as part of the at least one pre-processing step, the computer processor is adapted to apply a high frequency band pass filter to the specified RGB colour channels, across at least part of the field of view of the video camera or video camera module.

7. Video camera or video camera module of claim 1 wherein the bayer pattern provides an optical density of at least OD4.

8. Video camera or video camera module of claim 1 wherein: The detector is adapted to identify a part of the field of view of the camera in which there is an excess of light in at least on one RGB colour channel compared to the other RGB colour channel(s), that is consistent with laser dazzle from at least one type of laser, and to output to the computer processor an indication of the part of the field of view, and; In reducing values of the specified RGB colour channel(s) as part of the at least one pre-processing step the computer processor is adapted to reduce values of the specified RGB colour channel(s) preferentially in the indicated part of the field of view.

9. Video camera or video camera module of claim 1 wherein the computer processor is adapted to determine high spatial frequency variations in pixel values in at least one of the non-dazzled colour channel(s) and to add them to the dazzled channel whilst overall reducing the average values of the dazzled channel(s).

Description

[0023] A detailed embodiment of the invention will now be described by way of example, and with reference to the figures in which:

[0024] FIG. 1 shows an image of a frame of video data resulting from raw data being compressed and shown in greyscale, in which laser dazzle due to a blue laser is evident;

[0025] FIG. 2 shows an image of a frame of video data of the same scene, resulting from raw data being compressed, the blue channel being removed (zeroed out), and then being converted to greyscale;

[0026] FIG. 3 shows an image of a frame of video data of the same scene, resulting the blue channel of raw data being removed (zeroed out), the resulting video data being compressed, then being converted to greyscale; and

[0027] FIG. 4 shows a block diagram of an embodiment of the invention.

[0028] Turning to FIGS. 1, 2 and 3, three images are shown which are frames of video data collected of the same scene in which objects are visible but a blue laser is causing laser dazzle which causes reduction in image quality compared to if no laser was present. The only reason that the three figures are shown in greyscale is that this is a requirement of illustrations in patent applications.

[0029] In FIG. 1 the raw data has simply been compressed in a conventional way, the reduction in image quality is extreme.

[0030] In FIG. 2 the blue channel has been removed (zeroed out) after compressed video data was collected from the video camera module. Despite removal of the most strongly dazzled colour channel, the image exhibits strong reduction in image quality.

[0031] In FIG. 3, in the software environment, with the blue channel zeroed out, a conventional compression algorithm was applied. As can be seen the image quality is higher in FIG. 3 compared to FIG. 2.

[0032] Turning to FIG. 4, an embodiment of the present invention is illustrated. Three main possibilities are illustrated: [0033] 1. All the features including detector 5, being comprised in a video camera module 2; [0034] 2. All the features including detector 5′ (dashed line) being comprised in a video camera 1 (dashed line); or [0035] 3. A video camera 1 which receives dazzle detection information from an external dazzle detector 5″.

[0036] FIG. 4 shows a video camera module 2 comprising an image sensor 3 and a computer processor 4. The image sensor is behind a lens (not labelled) which directs light onto the image sensor 3.

[0037] Additionally a detector 5, 5′ or 5″ is shown in three possible locations in a box with dashed outline. If the detector is outside the video camera module 2 it may be part of a wider video camera 1 (shown with dashed outline) as detector 5′, or alternatively the detector might be outside of the video camera 1 as a separate unit, detector 5″.

[0038] Finally, whilst the pre-processing and compression are preferably performed by computer processor 4 within the video camera module 2, some or all processes may be performed by optional additional computer processor 6 (shown with dashed outline). Generally there may be multiple computer processors chips 4, 6 which to the extent that they share the pre-processing operations and/or post processing compression are to be considered as jointly providing the computer processor.

[0039] The video camera module or video camera operates as follows. Under normal conditions (in conditions which do not indicate that dazzle is present) the camera/module operates conventionally, and the raw data from the image sensor is compressed to provide compressed video data. In the case of laser dazzle that is specific to one or two of the RGB colour channels the video camera/module operates in an anti-dazzle mode. Detection of laser dazzle is possible in many ways although generally conditions indicating the presence of laser dazzle are detected, as opposed to detecting with certainty that the dazzle is caused by a laser.

[0040] Upon detection of dazzle in one or two RGB channels (and whilst this continues to be detected), the camera operates in anti-dazzle mode. This involves decreasing the image (pixel) values in the dazzled channel(s), prior to compressing the video data. This is preferably done within the video camera module.

[0041] The amount and method of decreasing the values in the dazzled channel(s) is up to the user, but typically a reduction of at least 50%, typically at least 75% is desirable across the field of view, and almost always would be at least a 10% reduction. A reduction of at least 90% is desirable in the close vicinity of the centre of the laser dazzle spot, however, since this needs to be done in real time and preferably on the camera module video chip, it may not be feasible to do anything other than a flat percentage reduction across the field of view.

[0042] One simple approach to reducing the values in the dazzled channel, is to reduce them all to either zero or to any other notional value (such as for example the mean or median value in the non-dazzled channels), across the field of view. Whilst this changes the colour of the picture, which is not desirable, it maximizes the clarity with which details visible in the other channels will be expressed in the compressed video data. An additional or alternative option is to reduce the values overall (i.e. on average across the frame) whilst preserving high spatial frequency variations, i.e. by applying a spatial band pass filter.

[0043] A more advanced and advantageous approach would be for the computer processor to be adapted to determine the spatial variation in the pixels in the dazzled channel and apply an optionally weighted reduction, whereby the amount that the dazzled channels values are reduced is advantageously higher in areas where a local average of the dazzled channel values is higher, and lower in areas where a local average of the dazzled channel values is lower. In the case of reducing the pixels values to below a certain threshold (for example to below 10% their initial value), it is advantageous to estimate their pixel value based upon the neighbouring non-dazzled channels. The advantage is that this improves the spatial resolution and promotes the visibility in non-dazzled channels, which can result in a clearer image.

[0044] Accordingly when there is no laser dazzle the camera operates optimally, and when dazzle is present in one or two colour channels, the camera performs better than a conventional camera.

[0045] More generally, there is provided a video camera or video camera module, comprising an RGB image sensor, a computer processor adapted to perform pre-processing followed by video compression, and a dazzle detector, characterised in responding to dazzle in one colour channel by reducing values in that colour channel prior to compressing the video data. This has the advantage that in the event of laser dazzle that is specific to a colour channel, the compressed video data generated will retain more detail from the other colour channels compared to a conventional camera.

[0046] Further embodiments are set out in the claims.