An example circuit includes a light detector and a biasing capacitor having (i) a first terminal that applies to the light detector an output voltage that can either bias or debias the light detector and (ii) a second terminal for controlling the output voltage. The circuit includes a first transistor connected to the second terminal of the biasing capacitor and configured to drive the output voltage to a first voltage level above a biasing threshold of the light detector and thereby biasing the light detector. The circuit includes a second transistor connected to the second terminal of the biasing capacitor and configured to drive the output voltage to a second voltage level below the biasing threshold of the light detector and thereby debiasing the light detector. The second voltage is a non-zero voltage that corresponds to a charge level of the biasing capacitor.

A light detection and measurement device comprises a silicon photomultiplier, at least one thermoelectric cooler thermally coupled to the silicon photomultiplier, a sealed enclosure surrounding the silicon photomultiplier and the at least one thermoelectric cooler, the enclosure including a substantially transparent window thermally coupled to the silicon photomultiplier, and a heat sinking device thermally coupled to the enclosure configured to remove waste heat. A method of cooling a silicon photomultiplier is also described.

An optical tomography imaging system includes a signal generator, at least one light emitter, at least one light receiver, a signal processor, and an image processor. The signal generator is configured to generate a periodic signal and a reference signal. The light emitter is configured to be activated by the periodic signal to generate an optical signal passing through an object under test. The light receiver is configured to receive and convert the optical signal passing through the object under test into an electrical signal. The signal processor is configured to generate a comparison signal according to the electrical signal and the reference signal. The image processor is configured to acquire a plurality of disassembled sine waves from the comparison signal and generate a reconstructed image according to the disassembled sine waves.

A system, apparatus and method of improved measurement of the SPF factor of sunscreen compositions. In one embodiment, a method of measuring the protection of a sunscreen composition includes exposing skin to a known intensity of light, measuring the amount of remitted light from the skin, applying sunscreen to the skin, exposing the skin to which the sunscreen has been applied the known intensity of emitted light of the spectrum of light from which the sunscreen is intended to protect the skin, measuring the amount of light remitted from the skin, and calculating a UltraViolet-A Protection Factor (UVA-PF) of the sunscreen by comparing the amount of light remitted from the skin with the sunscreen to the amount of light remitted from the skin without the sunscreen.

A flame detector that includes a spacer, a UV transparent window, and a UV sensing elements. The spacer has a spacer wall that extends along a first axis between a first spacer end and a second spacer end. The UV transparent window is disposed at the first spacer end. The spacer wall and the UV transparent window define a gas space. The UV sensing elements is disposed within the gas space.

Systems for detecting light (e.g., in a flow stream) are described. Light detection systems according to embodiments include a photodetector, an input modulator configured to modulate signal input into the photodetector and an output modulator configured to modulate signal output from the photodetector. Photodetector arrays having a plurality of light detection systems, e.g., as described, are also provided. Methods for matching output signals from two or more photodetectors (e.g., a plurality of photomultiplier tubes in a photodetector array) are also described. Flow cytometer systems and methods for detecting light from a sample in a flow stream are provided. Aspects further include kits having two or more of the subject light detection systems.

A system, apparatus and method of improved measurement of the SPF factor of sunscreen compositions. In one embodiment, a method of measuring the protection of a sunscreen composition includes exposing skin to a known intensity of light, measuring the amount of remitted light from the skin, applying sunscreen to the skin, exposing the skin to which the sunscreen has been applied the known intensity of emitted light of the spectrum of light from which the sunscreen is intended to protect the skin, measuring the amount of light remitted from the skin, and calculating a UltraViolet-A Protection Factor (UVA-PF) of the sunscreen by comparing the amount of light remitted from the skin with the sunscreen to the amount of light remitted from the skin without the sunscreen.

An optical tomography imaging system includes a signal generator, at least one light emitter, at least one light receiver, a signal processor, and an image processor. The signal generator is configured to generate a periodic signal and a reference signal. The light emitter is configured to be activated by the periodic signal to generate an optical signal passing through an object under test. The light receiver is configured to receive and convert the optical signal passing through the object under test into an electrical signal. The signal processor is configured to generate a comparison signal according to the electrical signal and the reference signal. The image processor is configured to acquire a plurality of disassembled sine waves from the comparison signal and generate a reconstructed image according to the disassembled sine waves.

An example circuit includes a light detector and a biasing capacitor having (i) a first terminal that applies to the light detector an output voltage that can either bias or debias the light detector and (ii) a second terminal for controlling the output voltage. The circuit includes a first transistor connected to the second terminal of the biasing capacitor and configured to drive the output voltage to a first voltage level above a biasing threshold of the light detector and thereby biasing the light detector. The circuit includes a second transistor connected to the second terminal of the biasing capacitor and configured to drive the output voltage to a second voltage level below the biasing threshold of the light detector and thereby debiasing the light detector. The second voltage is a non-zero voltage that corresponds to a charge level of the biasing capacitor.

A cytometer includes an avalanche photodiode, a switching power supply, a filter, and voltage adjustment circuitry. The switching power supply includes a feedback loop. The filter is electrically connected between the switching power supply and the avalanche photodiode. The voltage adjustment circuitry adjusts a voltage on the feedback loop based at least in part on a voltage measured between the filter and the avalanche photodiode.