Time of flight sensor with subframe compression and method
View Patent ↗A demodulation image sensor, such as used in time of flight (TOF) cameras, extracts all storage- and post-processing-related steps from the pixels to another array of storage and processing elements (proxels) on the chip. The pixel array has the task of photo-detection, first processing and intermediate storage to create subframes, while the array of storage and processing elements provides accumulation into frames. Particularly, sampled values of several subframes are summed in a compressed manner. Possible compression is to use exponential function.
1. A demodulation sensor, comprising:
a pixel array comprising pixels each of which produces at least two signals for subframes to synchronously demodulate modulated light from a light emitter;
a storage array comprising storage elements, each of the storage elements is operable to receive digital subframes; and
analog to digital converters between the pixel array and the storage array,
wherein the analog to digital converters are operable to convert the at least two signals into the digital subframes, and
wherein the storage elements are operable to compress the digital subframes and to accumulate the compressed digital subframes into full frames.
2. The demodulation sensor as claimed in claim 1 , wherein the storage elements perform exponential compression.
3. The demodulation sensor as claimed in claim 1 , further comprising a pixel readout controller for controlling readout of the signals from the pixel array.
4. The demodulation sensor as claimed in claim 1 , wherein each subframe comprises signals accumulated for different phase angles.
5. A demodulation method, comprising:
in a pixel array, producing at least two signals for each pixel for every subframe;
converting the at least two signals into digital subframes;
in a storage array comprising storage elements, receiving at each of the storage elements the digital subframes, compressing the digital subframes, and accumulating the compressed digital subframes into full frames,
wherein converting the at least two signals into digital subframes is performed by analog to digital converters between the pixel array and the storage array.
6. The method as claimed in claim 5 , wherein compressing the digital subframes comprises performing exponential compression of the digital subframes.
7. The method as claimed in claim 5 , further comprising controlling pixel readout of the signals from the pixel array.
8. The method as claimed in claim 5 , wherein each subframe comprises signals accumulated for different phase angles.
9. A time of flight camera, comprising:
a light emitter for generating intensity modulated light; and
a sensor including:
a pixel array comprising pixels that each produce at least two signals for subframes to synchronously demodulate the intensity modulated light from the light emitter,
a storage array comprising storage elements, each of the storage elements is operable to receive digital subframes; and
analog to digital converters between the pixel array and the storage array wherein the analog to digital converters are operable to convert the at least two signals into the digital subframes, and
wherein the storage elements are operable to compress the digital subframes and to accumulate the compressed digital subframes into full frames.
10. The time of flight camera as claimed in claim 9 , wherein the storage elements perform exponential compression.
11. The time of flight camera as claimed in claim 9 , further comprising a pixel readout controller for controlling the readout of the signals from the pixel array.
12. The time of flight camera as claimed in claim 9 , wherein each subframe comprises signals accumulated for different phase angles of the intensity modulated light.