Device of acquisition of a depth image of a scene
A device of acquisition of a depth image of a scene by detection of a reflected light signal. The device includes a stack of a first sensor and of a second sensor. The first sensor includes first depth photosites configured to acquire at least one first sample of charges photogenerated during first time periods. The second sensor includes second depth photosites arranged opposite the first photosites, the second photosites being configured to acquire at least one second sample of charges photogenerated during second time periods offset with respect to the first time periods by a first constant phase shift. The first sensor or the second sensor further includes third photosites configured to acquire at least one third sample during third time periods offset with respect to the first time periods by a second constant phase shift.
1. Device of acquisition of a depth image of a scene by detection of a reflected light signal corresponding to the reflection on the scene of a periodically amplitude-modulated incident light signal in near infrared, the device comprising a stack of a first sensor and of a second sensor, the first sensor comprising first depth photosites configured to acquire at least one first sample of charges photogenerated by detection of the light signal reflected during first time periods, the second sensor comprising second depth photosites arranged opposite the first depth photosites, the second depth photosites being configured to acquire at least one second sample of charges photogenerated by detection of the light signal reflected during second time periods offset with respect to the first time periods by a first constant phase shift, the first sensor or the second sensor further comprising third depth photosites configured to acquire at least one third sample by detection of the light signal reflected during third time periods offset with respect to the first time periods by a second constant phase shift different from the first phase shift.
2. Device according to claim 1 , further comprising means for compensating for the difference in quantities of received photons between the first and second sensors.
3. Device according to claim 1 , wherein the first sensor is formed inside and on top of a first semiconductor substrate and wherein the second sensor is formed inside and on top of a second semiconductor substrate.
4. Device according to claim 3 , wherein the first and second semiconductor substrates are made of different materials.
5. Device according to claim 3 , wherein the thicknesses of the first and second semiconductor substrates are different.
6. Device according to claim 1 , wherein the lateral dimensions of the first depth photosites are different from the lateral dimensions of the second depth photosites.
7. Device according to claim 1 , wherein the first and third depth photosites are confounded.
8. Device according to claim 1 , wherein the first and third depth photosites are distinct.
9. Device according to claim 1 , wherein the first sensor or the second sensor comprises fourth depth photosites configured to acquire at least one fourth sample by detection of the light signal reflected during fourth time periods offset with respect to the first time periods by a third constant phase shift different from the first and second phase shifts.
10. Device according to claim 9 , wherein the second and fourth depth photosites are confounded.
11. Device according to claim 9 , wherein the second and fourth depth photosites are distinct.
12. Device according to claim 1 , wherein the second time periods are longer than the first time periods.
13. Device according to claim 1 , wherein each first and second depth photosite comprises a photodiode and at least one transistor connected to the photodiode.
14. Device according to claim 1 , wherein the first sensor further comprises a plurality of 2D image pixels, the second sensor comprising no 2D image pixel.
15. System of acquisition of a depth image comprising the acquisition device according to claim 1 , a light source configured to emit the periodically amplitude-modulated incident light signal in near infrared, and a processor configured to determine, from the first, second, and third samples, a phase shift between the incident light signal and the reflected light signal.
16. System according to claim 15 , wherein the first sensor or the second sensor comprises fourth depth photosites configured to acquire at least one fourth sample by detection of the light signal reflected during fourth time periods offset with respect to the first time periods by a third constant phase shift different from the first and second phase shifts; and wherein the processor is configured to determine, from the first, second, third, and fourth samples, a phase shift between the incident light signal and the reflected light signal.
17. System according to claim 15 , further comprising means for compensating for the difference in quantities of received photons between the first and second sensors.
18. System according to claim 15 , wherein the processor is configured to compensate by digital processing for the difference in quantities of received photons between the first and second sensors.
19. System according to claim 15 , comprising first amplifiers of the analog signals delivered by the first depth photosites with a first amplification gain and second amplifiers of the analog signals delivered by the second depth photosites with a second amplification gain different from the first amplification gain.