# US 8,570,405 B2 · Determining light level variation in compressive imaging by injecting calibration patterns into pattern sequence > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,570,405 B2 - Document ID: US8570405B2 - Status: Granted - Kind: B2 - Application number: 13/193,553 - Filed: 2011-07-28 - Published: 2012-02-16 - Granted: 2013-10-29 - Earliest claimed: 2010-08-11 - Assignees: InView Technology Corporation - Applicants: Kevin F. Kelly; Richard G. Baraniuk; Leonore McMackin; Robert F. Bridge; Sujoy Chatterjee; Donna E. Hewitt; Tyler H. Weston - Inventors: Kevin F. Kelly; Richard G. Baraniuk; Leonore McMackin; Robert F. Bridge; Sujoy Chatterjee; Donna E. Hewitt; Tyler H. Weston - Web page: https://patentgrep.com/patent/US8570405B2 ## CPC - H04N 23/75: by influencing optical camera components - G02B 26/0833: {the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD (G02B26/0825 takes precedence; micromechanical devices in general B81B)} - H04N 23/71: Circuitry for evaluating the brightness variation - H04N 23/74: by influencing the scene brightness using illuminating means - H04N 25/00: Circuitry of solid-state image sensors [SSIS]; Control thereof - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract An imaging system and method that captures compressive sensing (CS) measurements of a received light stream, and also obtains samples of background light level (BGLL). The BGLL samples may be used to compensate the CS measurements for variations in the BGLL. The system includes: a light modulator to spatially modulate the received light stream with spatial patterns, and a lens to concentrate the modulated light stream onto a light detector. The samples of BGLL may be obtained in various ways: (a) injecting calibration patterns among the spatial patterns; (b) measuring complementary light reflected by digital micromirrors onto a secondary output path; (c) separating and measuring a portion of light from the optical input path; (d) low-pass filtering the CS measurements; and (e) employing a light power meter with its own separate input path. Also, the CS measurements may be high-pass filtered to attenuate background light variation. ## Claims ### Claim 1 A system for operating on a stream of light, the system comprising: a light modulation unit configured to modulate the light stream with a series of spatial patterns in order to produce a modulated light stream, wherein the light modulation unit includes a plurality of light modulating elements configured to modulate corresponding portions of the light stream, wherein each of the spatial patterns specifies an amount of modulation for each of the light modulating elements, wherein the series of spatial patterns includes first patterns and calibration patterns; a light sensing device configured to receive the modulated light stream and to generate a sequence of samples representing intensity of the modulated light stream as a function of time; and a processing unit configured to separate the sequence of samples into a first subsequence of samples that correspond to the first patterns and a second subsequence of samples that correspond to the calibration patterns, wherein the second subsequence of samples represents variation in background light level. ### Claim 2 (depends on 1) The system of claim 1, further comprising: a first optical subsystem configured to receive the light stream and to focus the received light stream onto the light modulation unit. ### Claim 3 (depends on 1) The system of claim 1, wherein the processing unit is configured to store the first subsequence and second subsequence of samples in a memory, wherein the first subsequence and second subsequence are usable to construct an image or a video sequence. ### Claim 4 (depends on 1) The system of claim 1, wherein the samples of the second subsequence are used to compensate the samples of the first subsequence for the variation in the background light level, wherein the compensated samples are usable to construct an image or a video sequence. ### Claim 5 (depends on 4) The system of claim 4, wherein the processing unit is configured to perform said compensation of the samples of the first subsequence using the samples of the second subsequence. ### Claim 6 (depends on 4) The system of claim 4, wherein the processing unit is configured to transmit the compensated samples to a receiver through a communication channel, wherein the receiver is configured to construct the image or the video sequence based on the compensated samples. ### Claim 7 (depends on 1) The system of claim 1, wherein the plurality of light modulating elements are mirrors whose orientations are independently controllable. ### Claim 8 (depends on 1) The system of claim 1, wherein the plurality of light modulating elements are elements whose transmittances are independently controllable. ### Claim 9 (depends on 1) The system of claim 1, further comprising: a second optical subsystem configured to direct the modulated light stream onto a light sensing surface of the light sensing device. ### Claim 10 (depends on 1) The system of claim 1, wherein the modulation amounts specified by the spatial patterns are binary values. ### Claim 11 (depends on 1) The system of claim 1, wherein the light sensing device includes one or more photodiodes. ### Claim 12 (depends on 1) The system of claim 1, wherein the plurality of light modulating elements are arranged in a two-dimensional array. ### Claim 13 (depends on 1) The system of claim 1, wherein the first patterns are pseudo-random patterns. ### Claim 14 (depends on 1) The system of claim 1, wherein the calibration patterns are included in the series of patterns in a periodic fashion. ### Claim 15 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, wherein the series of spatial patterns includes first patterns and calibration patterns; generating a sequence of samples representing intensity of the modulated light stream as a function of time; and separating the sequence of samples into a first subsequence of samples that correspond to the first patterns and a second subsequence of samples that correspond to the calibration patterns, wherein the second subsequence of samples represents variation in background light level. ### Claim 16 (depends on 15) The method of claim 15, further comprising: storing the first subsequence of samples and the second subsequence of samples in a memory, wherein the first subsequence and the second subsequence of samples are usable to construct an image or a video sequence. ### Claim 17 (depends on 15) The method of claim 15, further comprising: compensating the first subsequence of samples for the variation of background light level using the second subsequence of samples. ### Claim 18 (depends on 17) The method of claim 17, further comprising: constructing an image or a video sequence based on the compensated samples. ### Claim 19 (depends on 17) The method of claim 17, further comprising: transmitting the compensated samples to a receiver through a communication channel. ### Claim 20 (depends on 15) The method of claim 15, wherein the first patterns are pseudo-random patterns. ### Claim 21 (depends on 15) The method of claim 15, wherein each of the calibration patterns is a constant pattern specifying that all the light modulating elements assume a maximal transfer state. ### Claim 22 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, wherein the series of spatial patterns includes first patterns and calibration patterns; receive a sequence of samples from a first light sensing device, wherein the sequence of samples represents intensity of the modulated light stream as a function of time; and separate the sequence of samples into a first subsequence of samples corresponding to the first patterns and a second subsequence of samples corresponding to the calibration patterns, wherein the second subsequence of samples represents variation of background light level. ### Claim 23 A system for operating on light from an environment, 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 spatial patterns, wherein each of the patterns of the series specifies an orientation state for each of the mirrors, wherein the series of patterns includes first patterns and calibration patterns; 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 sequence of samples representing a cumulative intensity of the light portions reflected onto the sensing path as a function of time; and a processing unit configured to separate the sequence of samples into a first subsequence of samples that correspond to the first patterns and a second subsequence of samples that correspond to the calibration patterns, wherein the second subsequence of samples represents variation in background light level. ### Claim 24 (depends on 23) The system of claim 23, further comprising: a first optical subsystem configured to receive the light from the environment and to focus the received light onto the plurality of mirrors. ### Claim 25 (depends on 24) The system of claim 24, further comprising: a TIR prism pair positioned between the first optical subsystem and the plurality of mirrors. ### Claim 26 (depends on 23) The system of claim 23, further comprising: a second optical subsystem configured to receive the light portions reflected onto the sensing path by mirrors in the first orientation state, and to direct the received light portions onto a light sensing surface of the light sensing device. ### Claim 27 A method comprising: controlling a plurality of mirrors, wherein the mirrors are configured to reflect corresponding portions of a received beam of light, wherein each of the mirrors is configured to controllably switch between two orientation states, wherein said controlling the mirrors includes driving the mirrors through a series of spatial patterns, wherein each of the spatial patterns specifies an orientation state for each of the mirrors, wherein the series of spatial patterns includes first patterns and calibration patterns; receiving a sequence of samples from a first light sensing device, wherein the sequence of samples represents cumulative intensity of light portions reflected by mirrors in a first of the two orientation states as a function of time; separating the sequence of samples into a first subsequence of samples corresponding to the first patterns and a second subsequence of samples corresponding to the calibration patterns, wherein the second subsequence of samples represents variation of background light level in the environment. ### Claim 28 (depends on 27) The method of claim 27, wherein each of the calibration patterns is a pattern specifying that all the mirrors be in the first orientation state.