Low-pass filtering of compressive imaging measurements to infer light level variation

A method for operating on a stream of light, the method comprising:

• modulating the light stream with a series of spatial patterns in order to produce a modulated light stream;
• generating a first sequence of samples representing intensity of the modulated light stream as a function of time;
• and
• applying a low-pass filter to the first sequence of samples to obtain a filtered sequence of samples, wherein the filtered sequence of samples represents variation in background light level.

A non-transitory computer-readable memory medium storing program instructions, wherein the program instructions, when executed by a computer system, cause the computer system to:

• supply a series of spatial patterns to a light modulation unit, wherein the light modulation unit is configured to modulate a received light stream with the series of spatial patterns to obtain a modulated light stream;
• receive a first sequence of samples from a light sensing device, wherein the first sequence of samples represents intensity of the modulated light stream as a function of time;
• and
• apply a low-pass filter to the first sequence of samples to obtain a filtered sequence of samples, wherein the filtered sequence of samples represents variation in background light level.

A system for operating on light, the system comprising:

• a plurality of mirrors, wherein each of the mirrors is configured to controllably switch between two orientation states, wherein each of the mirrors is configured to (a) reflect a corresponding portion of the light onto a sensing path when the mirror is in a first of the two orientation states and (b) reflect the corresponding portion of the light away from the sensing path when the mirror is in a second of the two orientation states;
• a control unit configured to drive the orientation states of the mirrors through a series of patterns, wherein each of the patterns of the series specifies an orientation state for each of the mirrors;
• a light sensing device configured to receive light portions reflected onto the sensing path by mirrors in the first orientation state and to generate a first sequence of samples representing a cumulative intensity of the light portions reflected onto the sensing path as a function of time;
• a processing unit configured to low-pass filter the first sequence of samples to obtain a filtered sequence of samples, wherein the filtered sequence of samples represents variation in background light level.