Various embodiments disclosed herein describe a divided-aperture infrared spectral imaging (DAISI) system that is adapted to acquire multiple IR images of a scene with a single-shot (also referred to as a snapshot). The plurality of acquired images having different wavelength compositions that are obtained generally simultaneously. The system includes at least two optical channels that are spatially and spectrally different from one another. Each of the at least two optical channels are configured to transfer IR radiation incident on the optical system towards an optical FPA unit comprising at least two detector arrays disposed in the focal plane of two corresponding focusing lenses. The system further comprises at least one temperature reference source or surface that is used to dynamically calibrate the two detector arrays and compensate for a temperature difference between the two detector arrays.

Various embodiments disclosed herein describe a divided-aperture infrared spectral imaging (DAISI) system that is adapted to acquire multiple IR images of a scene with a single-shot (also referred to as a snapshot). The plurality of acquired images having different wavelength compositions that are obtained generally simultaneously. The system includes at least two optical channels that are spatially and spectrally different from one another. Each of the at least two optical channels are configured to transfer IR radiation incident on the optical system towards an optical FPA unit comprising at least two detector arrays disposed in the focal plane of two corresponding focusing lenses. The system further comprises at least one temperature reference source or surface that is used to dynamically calibrate the two detector arrays and compensate for a temperature difference between the two detector arrays.

An electromagnetic wave detection apparatus (10) includes a detector (18), a switching unit (16), and a controller (14). The detector (18) detects electromagnetic waves. The switching unit (16) includes a plurality of switching elements (19). The switching elements (19) are capable of switching between a first state and a second state. In the first state, the switching elements (19) propagate incident electromagnetic waves in a first direction (d1). In the second state, the switching elements (19) propagate incident electromagnetic waves in a second direction (d2). The controller (14) can control switching to the first state and the second state for each switching element (19). The controller (14) switches only a particular switching element (19), among the plurality of switching elements (19), to the first state.

Various embodiments disclosed herein describe a divided-aperture infrared spectral imaging (DAISI) system that is adapted to acquire multiple IR images of a scene with a single-shot (also referred to as a snapshot). The plurality of acquired images having different wavelength compositions that are obtained generally simultaneously. The system includes at least two optical channels that are spatially and spectrally different from one another. Each of the at least two optical channels are configured to transfer IR radiation incident on the optical system towards an optical FPA unit comprising at least two detector arrays disposed in the focal plane of two corresponding focusing lenses. The system further comprises at least one temperature reference source or surface that is used to dynamically calibrate the two detector arrays and compensate for a temperature difference between the two detector arrays.

Various embodiments disclosed herein describe a divided-aperture infrared spectral imaging (DAISI) system that is adapted to acquire multiple IR images of a scene with a single-shot (also referred to as a snapshot). The plurality of acquired images having different wavelength compositions that are obtained generally simultaneously. The system includes at least two optical channels that are spatially and spectrally different from one another. Each of the at least two optical channels are configured to transfer IR radiation incident on the optical system towards an optical FPA unit comprising at least two detector arrays disposed in the focal plane of two corresponding focusing lenses. The system further comprises at least one temperature reference source or surface that is used to dynamically calibrate the two detector arrays and compensate for a temperature difference between the two detector arrays.

Methods and apparatus to count people are disclosed. Example people counting apparatus disclosed herein include a difference calculator to calculate a degree of similarity between a first characteristic dataset and a second characteristic dataset representative of face detections in images. Disclosed example people counting apparatus also include a limiter to store the first characteristic dataset and the second characteristic dataset in a plurality of characteristic datasets associated when the degree of similarity does not satisfy a threshold, and to store the first characteristic dataset in the plurality of characteristic datasets and discard the second characteristic dataset when the degree of similarity satisfies the threshold to limit a number of stored characteristic datasets. Disclosed example people counting apparatus further include a comparator to compare the plurality of characteristic datasets to each other to determine a number of unique faces in an environment during a first period of time.

Methods and apparatus to count people are disclosed. Example people counting apparatus disclosed herein include a difference calculator to calculate a degree of similarity between a first characteristic dataset and a second characteristic dataset representative of face detections in images. Disclosed example people counting apparatus also include a limiter to store the first characteristic dataset and the second characteristic dataset in a plurality of characteristic datasets associated when the degree of similarity does not satisfy a threshold, and to store the first characteristic dataset in the plurality of characteristic datasets and discard the second characteristic dataset when the degree of similarity satisfies the threshold to limit a number of stored characteristic datasets. Disclosed example people counting apparatus further include a comparator to compare the plurality of characteristic datasets to each other to determine a number of unique faces in an environment during a first period of time.

Methods and apparatus to count people are disclosed. Example people counting apparatus disclosed herein include a difference calculator to calculate a degree of similarity between a first characteristic dataset and a second characteristic dataset representative of face detections in images. Disclosed example people counting apparatus also include a limiter to store the first characteristic dataset and the second characteristic dataset in a plurality of characteristic datasets associated when the degree of similarity does not satisfy a threshold, and to store the first characteristic dataset in the plurality of characteristic datasets and discard the second characteristic dataset when the degree of similarity satisfies the threshold to limit a number of stored characteristic datasets. Disclosed example people counting apparatus further include a comparator to compare the plurality of characteristic datasets to each other to determine a number of unique faces in an environment during a first period of time.

Methods and apparatus to count people are disclosed. Example people counting apparatus disclosed herein include a difference calculator to calculate a degree of similarity between a first characteristic dataset and a second characteristic dataset representative of face detections in images. Disclosed example people counting apparatus also include a limiter to store the first characteristic dataset and the second characteristic dataset in a plurality of characteristic datasets associated when the degree of similarity does not satisfy a threshold, and to store the first characteristic dataset in the plurality of characteristic datasets and discard the second characteristic dataset when the degree of similarity satisfies the threshold to limit a number of stored characteristic datasets. Disclosed example people counting apparatus further include a comparator to compare the plurality of characteristic datasets to each other to determine a number of unique faces in an environment during a first period of time.

A light sensing circuit includes a photomultiplier in electrical communication with an array of capacitors or resistors. Each capacitor or resistor in the array having an associated switch and having a capacitance or resistance different from every other capacitor or resistor in the array. Each switch has an open state and a closed state, thus enabling each capacitor or resistor to be placed in electrical communication with the photomultiplier or be isolated from the photomultiplier. The switchable array may be in electrical communication with an analog to digital converter (ADC) or a transimpedance amplifier (TIA). The switchable array allows the ADC or TIA to be sensitive to low value signals and operate at a large dynamic range and operate at a fast rate.