Adaptive illumination for a time-of-flight camera on a vehicle
Disclosed are devices, systems and methods for capturing an image. In one aspect an electronic camera apparatus includes an image sensor with a plurality of pixel regions. The apparatus further includes an exposure controller. The exposure controller determines, for each of the plurality of pixel regions, a corresponding exposure duration and a corresponding exposure start time. Each pixel region begins to integrate incident light starting at the corresponding exposure start time and continues to integrate light for the corresponding exposure duration. In some example embodiments, at least two of the corresponding exposure durations or at least two of the corresponding exposure start times are different in the image.
1. A method, comprising:
for each of a plurality of pixel regions of an image sensor,
associating the pixel region with at least one of a plurality of objects;
determining an exposure duration based on light intensity received at the pixel region; and
determining a start time for exposure of the pixel region based on the exposure duration and a distance between the at least one object and the image sensor; and
obtaining an image of the plurality of objects by gating exposures of the plurality of pixel regions based on their respective start times and exposure durations,
wherein the start time of the pixel region associated with at least one object corresponds to a time of flight of light from a light source to the at least one object and back from the at least one object to the image sensor.
2. The method of claim 1 , wherein:
the plurality of objects comprise a first object and a second object; the plurality of pixel regions comprise a first pixel region;
associating each of the plurality of pixel regions with at least one of a plurality of objects comprises associating the first pixel region with the first object and the second object; and
determining a start time for exposure of each of the plurality of pixel regions comprises:
for the first pixel region,
determining a first start time using a first distance between the first object and the image sensor; and
determining a second start time using a second distance between the second object and the image sensor, wherein the first distance is different from the second distance.
3. The method of claim 2 , further comprising:
obtaining the image including the first object and the second object by gating the first pixel region using a gating circuit associated with the first pixel region such that the gating circuit begins exposure of the first pixel region at the first start time, continues the exposure for a first exposure duration, begins exposure of the first pixel region again at the second start time, and continues the exposure for a second exposure duration.
4. The method of claim 1 , further comprising:
activating the light source to illuminate the at least one object.
5. The method of claim 1 , wherein, for a current image, the exposure duration of one of the plurality of pixel regions is determined using one or more images obtained before the current image.
6. The method of claim 1 , further comprising: determining a distance between each of the plurality of objects and the image sensor using at least one of a distance sensor or a high-definition map.
7. A non-transitory computer readable storage medium encoded with executable instructions for operating an image sensor that, when executed by at least one processor, cause the at least one processor to perform operations, comprising:
for each of a plurality of pixel regions of the image sensor,
associating the pixel region with at least one of a plurality of objects;
determining an exposure duration based on light intensity received at the pixel region; and
determining an exposure start time for the pixel region based on the exposure duration and a distance between the at least one object and the image sensor; and
obtaining an image of the plurality of objects by gating exposures of the plurality of pixel regions based on their respective start times and exposure durations,
wherein the exposure start time determined for a pixel region associated with an object corresponds to a time of flight of light from a light source to the object and back from the object to the image sensor.
8. The non-transitory computer readable storage medium of claim 7 , wherein gating exposures of the plurality of pixel regions comprises causing a gating circuit to expose each of the plurality of pixel regions by beginning exposure of the pixel region at the start time determined for the pixel region and continuing the exposure for the exposure duration determined for the pixel region.
9. The non-transitory computer readable storage medium of claim 7 , wherein gating exposures of the plurality of pixel regions comprises causing a gating circuit to expose the pixel region by beginning an exposure of the pixel region at the start time determined for the pixel region and ending the exposure at an exposure end time.
10. The non-transitory computer readable storage medium of claim 7 , wherein the executable instructions cause the at least one processor to perform operations, comprising:
associating a first pixel region of the plurality of pixel regions with a first object and a second object of the plurality of objects;
determining a first exposure start time using a first distance between the first object and the image sensor; and
determining a second exposure start time using a second distance between the second object and the image sensor, wherein the first distance is different from the second distance.
11. The non-transitory computer readable storage medium of claim 10 , wherein the executable instructions cause the at least one processor to perform operations, comprising:
obtaining the image comprising the first object and the second object by gating the first pixel region using a gating circuit associated with the first pixel region such that the gating circuit begins exposure of the first pixel region at the first exposure start time, continuing the exposure for a first exposure duration, beginning exposure of the first pixel region again at the second exposure start time, and continuing the exposure for a second exposure duration.
12. The non-transitory computer readable storage medium of claim 7 , wherein the operations further comprise: activating the light source to illuminate a scene including one or more of the plurality of objects.
13. An electronic camera apparatus, comprising:
an image sensor with a plurality of pixel regions;
an exposure controller configured to determine, for each pixel region in the plurality of pixel regions, an exposure start time and an exposure duration of the pixel region; and
a plurality of gating circuits, wherein each gating circuit is configured to gate a pixel region in the plurality of pixel regions to begin exposure of the pixel region at an exposure start time, and continue the exposure for an exposure duration or end the exposure at an exposure end time,
wherein each pixel region is configured to begin collecting incoming light starting at a corresponding exposure start time and continue collecting the incoming light during the corresponding exposure,
wherein the exposure start time for a pixel region in the plurality of pixel regions that is associated with at least one object corresponds to a time of flight of light from a light source to the at least one object and back from the at least one object to the image sensor, and
wherein the exposure duration for a pixel region in the plurality of pixel regions is determined based on light intensity received at the pixel region.
14. The apparatus of claim 13 , wherein, for a first pixel region in the plurality of pixel regions, the exposure controller is configured to determine a first exposure start time using a first distance between the image sensor and a first object imaged by the first pixel region and determine a second exposure start time using a second distance between the image sensor and a second object imaged by the first pixel region, wherein the first distance is different from the second distance.
15. The apparatus of claim 14 , wherein a gating circuit in the plurality of gating circuits is configured to begin exposure of the first pixel region at the first exposure start time, continue the exposure for a first exposure duration, begin exposure of the first pixel region again at the second exposure start time, and continue the exposure for a second exposure duration to obtain a single image of the first object and the second object using the image sensor.
16. The apparatus of claim 13 , wherein, for an object imaged in a single image by several pixel regions in the plurality of pixel regions, at least two pixel regions in the several pixel regions have exposure start times that are different.
17. The apparatus of claim 13 , further comprising a shutter for each of the plurality of pixel regions configured to open at the exposure start time of the pixel region and remain open for the exposure duration of the pixel region.