Mechanisms for Conserving Power in a Compressive Imaging System
A system and method for conserving power in compressive imaging. An optical subsystem separates an incident light stream into a primary light stream and a secondary light stream. The primary light stream is modulated with a sequence of spatial patterns by a light modulator. The modulated light stream is sensed by a first light sensing device. The secondary light stream is sensed by a second light sensing device. The signal(s) produced by the second light sensing device may be monitored to determine when to turn on power to the light modulator. Thus, the light modulator may remain off when not needed. In an alternative implementation, a light sensing device is used to sense the light reflected from the light modulator in its power-off state. The signal(s) produced by that light sensing device may be monitored to determine when to turn on power to the light modulator.
1 . A system comprising:
an optical subsystem configured to receive an incident light stream and to separate the incident light stream into a first light stream and a second light stream;
a light modulation unit including a plurality of light reflecting elements whose orientations are independently controllable, wherein each of the light reflecting elements is configured to controllably switch between two active orientation states when the light modulation unit is powered on, wherein the light modulation unit, when it is powered on, is configured to modulate the first light stream with a time sequence of spatial patterns to obtain a modulated light stream;
a first light sensing device configured to receive the modulated light stream and to generate a first data stream in response to the modulated light stream when the light modulation unit is powered on;
a second light sensing device configured to receive the second light stream and to generate a second data stream in response to the second light stream at least when the light modulation unit is powered off;
a control unit configured to:
monitor the second data stream when the light modulation unit is powered off in order to detect a light variation event in the second data stream, wherein the light variation event indicates a variation of light in the second light stream; and
turn on power to the light modulation unit in response to determining that a trigger condition is satisfied, wherein the trigger condition includes detection of the light variation event.
2 . The system of claim 1 , wherein the control unit is configured to:
inject a sequence of measurement patterns into the time sequence of spatial patterns after turning on power to the light modulation unit; and
execute a reconstruction algorithm on a subset of the first data stream corresponding to the sequence of measurement patterns in order to obtain an image or image sequence.
3 . The system of claim 1 , further comprising a transmitter, wherein the control unit is configured to:
inject a sequence of measurement patterns into the time sequence of spatial patterns after turning on power to the light modulation unit; and
direct the transmitter to transmit a subset of the first data stream onto a transmission channel, wherein the subset of the first data stream corresponds to the sequence of measurement patterns.
4 . The system of claim 1 , wherein the second light sensing device includes a light sensing element and an analog-to-digital converter (ADC), wherein the light sensing element is configured to generate an analog electrical signal representing intensity of the second light stream as a function of time, wherein the ADC is configured to capture a sequence of samples of the analog electrical signal, wherein the second data stream includes the sequence of samples.
5 . The system of claim 1 , wherein the second light sensing device includes a plurality of light sensing elements, each configured to receive a corresponding spatial portion of the second light stream, wherein, for each of the light sensing elements, the second light sensing device is configured to capture a corresponding sequence of samples representing intensity over time of the corresponding spatial portion of the second light stream, wherein the second data stream includes the sequences of samples.
6 . The system of claim 1 , wherein the second light sensing device includes a plurality of light sensing elements, each configured to receive a corresponding spectral portion of the second light stream, wherein, for each of the light sensing elements, the second light sensing device is configured to capture a corresponding sequence of intensity samples representing intensity over time of the corresponding spectral portion of the second light stream, wherein the second data stream includes the sequences of samples.
7 . The system of claim 1 , wherein the second light sensing device includes a motion sensor configured to generate the second data stream in response to the second light stream.
8 . The method of claim 1 , wherein the control unit is configured to continue to monitor the second data stream after the light modulation unit is powered on, and to turn off power to the light modulation unit in response to an expiration of a predetermined amount of time in which no light variation is detected in the continued monitoring of the second data stream.
9 . The system of claim 1 , wherein the first light sensing device includes a plurality of light sensing elements, each configured to receive a corresponding spatial portion of the modulated light stream, wherein, for each of the light sensing elements, the first light sensing device is configured to capture a corresponding sequence of intensity samples representing intensity over time of the corresponding spatial portion of the modulated light stream, wherein the first data stream includes the sequences of intensity samples.
10 . The system of claim 9 , wherein the control unit is further configured to monitor the first data stream after turning on power to the light modulation unit in order to detect object movement within a field of view corresponding to the incident light stream.
11 . The method of claim 10 , wherein the control unit, in response to detecting object movement within the field of view, is configured to execute a reconstruction algorithm, wherein the reconstruction algorithm is configured to compute an image or image sequence based on at least a subset of the first data stream.
12 . The method of claim 10 , further comprising a transmitter, wherein the control unit, in response detecting object movement within the field of view, is configured to direct the transmitter to transmit at least a subset of the first data stream onto a communication channel.
13 . The method of claim 10 , wherein the control unit is configured to turn off power to the light modulation unit in response to an expiration of a predetermined amount of time in which no object movement is detected in the monitoring of the first data stream.
14 . The system of claim 1 , wherein the control unit is further configured to monitor the first data stream after turning on power to the light modulation unit in order to detect a signal within the incident light stream and having significant energy within a signal class of interest.
15 . The system of claim 14 , wherein the control unit, in response to detecting said signal having significant energy within the signal class of interest, is configured to execute a reconstruction algorithm, wherein the reconstruction algorithm is configured to compute an image or image sequence based on at least a subset of the first data stream.
16 . The system of claim 14 , further comprising a transmitter, wherein the control unit, in response to detecting said signal having significant energy within the signal class of interest, is configured to direct the transmitter to transmit at least a subset of the first data stream onto a communication channel.
17 . The system of claim 1 , wherein the first light sensing device includes a plurality of light sensing elements, each configured to receive a corresponding spectral portion of the modulated light stream, wherein, for each of the light sensing elements, the first light sensing device is configured to capture a corresponding sequence of intensity samples representing intensity over time of the corresponding spectral portion of the modulated light stream, wherein the first data stream includes the sequences of intensity samples,
18 . The system of claim 17 , wherein the control unit is further configured to monitor the first data stream in order to detect a spectral signature of interest in the modulated light stream.
19 . The system of claim 18 , wherein the control unit is configured to execute a reconstruction algorithm in response to detecting the spectral signature of interest, wherein the reconstruction algorithm is configured to compute an image or image sequence or multispectral image based on at least a subset of the first data stream.
20 . The system of claim 18 , further comprising a transmitter, wherein the control unit, in response to detecting the spectral signature of interest, is configured to direct the transmitter to transmit at least a subset of the first data stream onto a communication channel.
21 . The system of claim 1 , wherein, after turning on power to the light modulation unit, the control unit is configured to search for a region within the field of view that contains a bright object by:
injecting a sequence of search patterns into the sequence of spatial patterns; and
selecting a next search pattern to be injected into the sequence of spatial patterns based on a portion of the first data stream that corresponds to one or more previous ones of the search patterns that have already been injected into the sequence of spatial patterns.
22 . A method comprising:
separating an incident light stream into at least a first light stream and a second light stream;
supplying the first light stream to a light modulation unit, wherein the light modulation unit is configured to modulate the first light stream with a time sequence of spatial patterns when it is powered on, wherein said modulating the first light stream produces a modulated light stream;
generating a first data stream in response to the modulated light stream when the light modulation unit is powered on;
generating a second data stream in response to the second light stream at least when the light modulation unit is powered off;
monitoring the second data stream when the light modulation unit is powered off in order to detect a light variation event in the second data stream, wherein the light variation event indicates a variation of light in the second light stream; and
turning on power to the light modulation unit in response to determining that a trigger condition is satisfied, wherein the trigger condition includes detection of the light variation event in the second data stream.
23 . The method of claim 22 , further comprising:
performing a set of operations after turning on power to the light modulation unit, wherein the set of operations includes:
injecting a sequence of measurement patterns into the time sequence of spatial patterns; and
executing a reconstruction algorithm on a subset of the first data stream corresponding to the sequence of measurement patterns in order to obtain an image or image sequence.
24 . The method of claim 22 , further comprising:
performing a set of operations after turning on power to the light modulation unit, wherein the set of operations includes:
injecting a sequence of measurement patterns into the time sequence of spatial patterns; and
directing a transmitter to transmit a subset of the first data stream onto a transmission channel, wherein the subset of the first data stream corresponds to the sequence of measurement patterns.
25 . The method of claim 22 , wherein said generating the second data stream includes converting the second light stream into an analog electrical signal and capturing a sequence of samples of the analog electrical signal, wherein the second data stream includes the sequence of samples.
26 . The method of claim 22 , wherein said generating the second data stream includes converting spatial portions of the second light stream into respective sequences of samples, wherein the second data stream includes the sequences of samples.
27 . The method of claim 22 , wherein said generating the second data stream includes converting spectral portions of the second light stream into respective sequences of samples, wherein the second data stream includes the sequences of samples.
28 . The method of claim 22 , wherein said generating the second data stream is performed by a motion sensor.
29 . The method of claim 28 , wherein the motion sensor includes a passive infrared sensor.
30 . The method of claim 22 , wherein said generating the first data stream comprises converting spatial portions of the modulated light stream into respective sequences of intensity samples, wherein the first data stream includes the sequences of intensity samples.
31 . The system of claim 30 , further comprising:
monitoring the first data stream after turning on power to the light modulation unit in order to detect object movement within a field of view corresponding to the incident light stream.
32 . The method of claim 31 , further comprising:
in response detecting object movement within the field of view, executing a reconstruction algorithm in order to compute an image or image sequence based on at least a subset of the first data stream.
33 . The method of claim 31 , further comprising:
in response detecting object movement within the field of view, directing a transmitter to transmit at least a subset of the first data stream onto a communication channel.
34 . The method of claim 31 , further comprising:
turning off power to the light modulation unit in response to an expiration of a predetermined amount of time in which no object movement is detected in the monitoring of the first data stream.
35 . The method of claim 22 , further comprising:
monitoring the first data stream after turning on power to the light modulation unit in order to detect a signal within the incident light stream having significant energy within a signal class of interest.
36 . The method of claim 35 , further comprising:
in response to detecting said signal having significant energy within the signal class of interest, executing a reconstruction algorithm, wherein the reconstruction algorithm computes an image or image sequence based on at least a subset of the first data stream.
37 . The method of claim 35 , further comprising:
in response to detecting said signal having significant energy within the signal class of interest, directing a transmitter to transmit at least a subset of the first data stream onto a communication channel.
38 . The method of claim 22 , wherein said generating the first data stream includes converting spectral portions of the modulated light stream into respective sequences of intensity samples, wherein the first data stream includes the sequences of intensity samples.
39 . The method of claim 38 , further comprising:
monitoring the first data stream in order to detect a spectral signature of interest in the modulated light stream.
40 . The method of claim 39 , further comprising:
in response to detecting the spectral signature of interest, executing a reconstruction algorithm, wherein the reconstruction algorithm computes an image or image sequence based on at least a subset of the first data stream.
41 . The method of claim 39 , further comprising:
in response to detecting the spectral signature of interest, directing a transmitter to transmit at least a subset of the first data stream onto a communication channel.
42 . The method of claim 22 , further comprising:
searching for a bright object within a field of view of the incident light field after turning on power to the light modulation unit, wherein said searching includes:
injecting a sequence of search patterns into the sequence of spatial patterns; and
selecting a next search pattern to be injected into the sequence of spatial patterns based on a portion of the first data stream that corresponds to one or more previous search patterns that have already been injected into the sequence of spatial patterns.
43 . A system comprising:
a light modulation unit including a plurality of light reflecting elements whose orientations are independently controllable, wherein each of the light reflecting elements is configured to assume a neutral orientation state when the light modulation unit is powered off, wherein each of the light reflecting elements is configured to controllably switch between two active orientation states when the light modulation unit is powered on, wherein the light reflecting elements are configured to modulate an incident light stream with a time sequence of spatial patterns when the light modulation unit is powered on, wherein the modulation produces a modulated light stream, wherein the light reflecting elements are configured to reflect the incident light stream from the neutral orientation state when the light modulation unit is powered off to produce a neutral-state light stream;
a first light sensing device configured to receive the modulated light stream when the light modulation unit is powered on, and to generate a first data stream in response to the modulated light stream;
a second light sensing device configured to receive the neutral-state light stream when the light modulation unit is powered off, and to generate a second data stream in response to the neutral-state light stream;
a control unit configured to:
monitor the second data stream when the light modulation unit is powered off in order to detect a light variation event in the second data stream, wherein the light variation event indicates a variation of light in the neutral-state light stream; and
turn on power to the light modulation unit in response to determining that a trigger condition is satisfied, wherein the trigger condition includes detection of the light variation event in the second data stream.
44 . The system of claim 43 , wherein, after turning on power to the light modulation unit, the control unit is configured to:
inject a sequence of measurement patterns into the time sequence of spatial patterns; and
execute a reconstruction algorithm on a subset of the first data stream corresponding to the sequence of measurement patterns in order to obtain an image or image sequence.
45 . The system of claim 43 , further comprising a transmitter, wherein, after turning on power to the light modulation unit, the control unit is configured to:
inject a sequence of measurement patterns into the time sequence of spatial patterns; and
direct the transmitter to transmit a subset of the first data stream onto a transmission channel, wherein the subset of the first data stream corresponds to the sequence of measurement patterns.
46 . The system of claim 43 , wherein the first light sensing device is actively cooled, wherein the second light sensing device is not actively cooled.
47 . The system of claim 43 , wherein the plurality of light reflecting elements are arranged on a plane, wherein the light modulation unit is configured so that an angle of incidence of the incident light stream on the plane is not equal to zero.
48 . The system of claim 43 , wherein the control unit is configured to monitor the first data stream after turning on power to the light modulation unit in order to detect a signal in the incident light stream having sufficient energy within a signal class of interest.
49 . The system of claim 48 , wherein the control unit is configured to execute a reconstruction algorithm in response to detecting said signal having significant energy within the signal class of interest, wherein the reconstruction algorithm is configured to compute an image or image sequence based on at least a subset of the first data stream.
50 . The system of claim 48 , further comprising a transmitter, wherein the control unit is configured to direct the transmitter to transmit at least a subset of the first data stream onto a communication channel in response to detecting said signal having significant energy within the signal class of interest.
51 . The system of claim 43 , wherein the control unit is configured to monitor the second data stream after turning on power to the light modulation unit in order to detect a signal in the incident light stream having sufficient energy within a signal class of interest.
52 . The system of claim 43 , wherein the second light sensing device includes a light sensing element and an analog-to-digital converter (ADC), wherein the light sensing element is configured to generate an analog electrical signal representing intensity of the neutral-state light stream as a function of time, wherein the ADC is configured to capture a sequence of samples of the analog electrical signal, wherein the second data stream includes the sequence of samples.
53 . The system of claim 43 , wherein the second light sensing device includes a plurality of light sensing elements, each configured to receive a corresponding spatial portion of the neutral-state light stream, wherein, for each of the light sensing elements, the second light sensing device is configured to capture a corresponding sequence of samples representing intensity over time of the corresponding spatial portion of the neutral-state light stream, wherein the second data stream includes the sequences of samples captured by the light sensing elements.
54 . The system of claim 43 , wherein the second light sensing device includes a plurality of light sensing elements, each configured to receive a corresponding spectral portion of the neutral-state light stream, wherein, for each of the light sensing elements, the second light sensing device is configured to capture a corresponding sequence of intensity samples representing intensity of the corresponding spectral portion of the neutral-state light stream, wherein the second data stream includes the sequences of samples captured by the light sensing elements.
55 . The system of claim 43 , wherein the second light sensing device includes a motion sensor configured to generate the second data stream in response to the neutral-state light stream.
56 . The system of claim 43 , further comprising an optical subsystem and a motion sensor, wherein the optical subsystem is configured to receive an input light stream and separate the input light stream into two output streams including the incident light stream and a secondary light stream, wherein the motion sensor is configured to receive the secondary light stream and generate a sequence of samples in response to the secondary light stream, wherein the control unit is configured to monitor the sequence of samples, wherein the trigger condition also includes detection of a disturbance in the sequence of samples.
57 . A method comprising:
supplying an incident light stream to a light modulation unit, wherein the light modulation unit includes a plurality of light reflecting elements whose orientations are independently controllable, wherein each of the plurality of light reflecting elements take a neutral orientation state when the light modulation unit is powered off;
when the light modulation unit is powered off, reflecting the incident light stream from the plurality of light reflecting elements to obtain a neutral-state light stream, wherein the incident light stream is reflected from the light reflecting elements in the neutral orientation state;
generating a neutral-state data stream in response to the neutral-state light stream when the light modulation unit is powered off;
monitoring the neutral-state data stream when the light modulation unit is powered off in order to detect a light variation event in the neutral-state data stream, wherein the light variation event indicates a variation of light in the neutral-state light stream;
turning on power to the light modulation unit in response to determining that a trigger condition is satisfied, wherein the trigger condition includes said detection of the light variation event in the neutral-state data stream;
after turning on power to the light modulation unit, modulating the incident light stream with a time sequence of spatial patterns to obtain a modulated light stream; and
generating an on-state data stream in response to the modulated light stream.
58 . The method of claim 57 , further comprising:
executing a reconstruction algorithm on at least a subset of the on-state data stream to obtain an image or image sequence.
59 . The method of claim 57 , further comprising:
transmitting at least a subset of the on-state data stream onto a transmission channel.
60 . The method of claim 57 , further comprising:
after turning on power to the light modulation unit, monitoring the on-state data stream in order to detect a signal in the incident light stream having sufficient energy within a signal class of interest.
61 . The method of claim 60 , further comprising:
in response to detecting said signal having significant energy within the signal class of interest, executing a reconstruction algorithm, wherein the reconstruction algorithm is configured to compute an image or image sequence based on at least a subset of the on-state data stream.
62 . The method of claim 60 , further comprising:
in response to detecting said signal having significant energy within the signal class of interest, directing a transmitter to transmit at least a subset of the on-state data stream onto a communication channel.
63 . The method of claim 57 , wherein said generating the neutral-state data stream includes converting the neutral-state light stream into an analog electrical signal and capturing a sequence of samples of the analog electrical signal.
64 . The method of claim 57 , wherein said generating the neutral-state data stream includes converting spatial portions of the neutral-state light stream into respective sequences of intensity samples, wherein the neutral-state data stream includes the sequences of intensity samples.
65 . The method of claim 57 , wherein said generating the neutral-state data stream includes converting spectral portions of the neutral-state light stream into respective sequences of intensity samples, wherein the neutral-state data stream includes the sequences of samples.
66 . The method of claim 57 , wherein said generating the neutral-state data stream is performed by a motion sensor.
67 . The method of claim 57 , further comprising:
separating an input light stream into two output streams including the incident light stream and a secondary light stream;
converting the secondary light stream into a sequence of samples using a motion sensor; and
monitoring the sequence of samples to detect a disturbance in the sequence of samples, wherein the trigger condition also includes detection of the disturbance.
68 . A system comprising:
a light modulation unit configured to receive a first light stream from a first optical input path, wherein the light modulation unit includes a plurality of light reflecting elements whose orientations are independently controllable, wherein each of the light reflecting elements is configured to controllably switch between two active orientation states when the light modulation unit is powered on, wherein the light modulation unit, when it is powered on, is configured to modulate the first light stream with a time sequence of spatial patterns to obtain a modulated light stream;
a first light sensing device configured to receive the modulated light stream and to generate a first data stream in response to the modulated light stream when the light modulation unit is powered on;
a motion sensor configured to receive a second light stream from a second optical input path, and to generate a second data stream in response to the second light stream at least when the light modulation unit is powered off, wherein the first and second optical input paths are independent optical paths;
a control unit configured to:
monitor the second data stream when the light modulation unit is powered off in order to detect a disturbance in the second data stream, wherein the disturbance indicates object motion in the field of view of the second light stream; and
turn on power to the light modulation unit in response to detection of the disturbance.
69 . The system of claim 68 , wherein the motion sensor includes a passive infrared sensor.