An optical difference detector includes a first APD and a second APD, a first voltage application unit that applies a first bias voltage to the first APD and a second voltage application unit that applies a second bias voltage to the second APD, a differential amplifier that is connected in parallel to the first APD and the second APD and amplifies a difference between a first signal current output from the first APD and a second signal current output from the second APD, and a feedback control unit that controls the second bias voltage so that a low frequency component of a first monitoring current in the first APD and a low frequency component of a second monitoring current in the second APD are equal.

Disclosed is a bio illuminance measuring apparatus including a circadian lambda filter passing external light along according to a circadian rhythm sensitivity curve, a visual lambda filter passing the external light along according to a visual sensitivity curve, a photo sensing portion sensing and converting the external light, which has passed through the circadian lambda filter, into a circadian wavelength signal and sensing and converting the external light, which has passed through the visual lambda filter, into a visual wavelength signal, and an illuminance calculating portion which calculates a ratio between the circadian wavelength signal and the visual wavelength signal, calculates a circadian action factor by applying the ratio between the circadian wavelength signal and the visual wavelength signal to a circadian action function which varies according to the visual wavelength signal, and calculates a bio illuminance value of the external light on the basis of the circadian action factor.

A vehicle window with an anisotropic light sensor, has a first glass layer and a second glass layer, wherein an arrangement of light-sensitive elements is arranged, substantially parallel to the first glass layer, between the first glass layer and the second glass layer, wherein the pane furthermore has an aperture such that light can shine through the second glass layer and the aperture onto at least one of the light-sensitive elements, wherein, depending on the direction of incident light, the sensor provides a signal that is indicative of the direction, wherein the arrangement of light-sensitive elements has a camera chip and wherein the arrangement of light-sensitive elements is arranged on a flexible film.

Structures for a photonics chip, testing methods for a photonics chip, and methods of forming a structure for a photonics chip. A photonics chip includes a first waveguide, a second waveguide, an optical tap coupling the first waveguide to the second waveguide, and a photodetector coupled to the second waveguide. A laser is attached to the photonics chip. The laser is configured to generate laser light directed by the first waveguide to the optical tap.

Certain aspects pertain to a cloud detector comprising a first detector module directed to a first region of the sky and a second detector module directed to a second region of the sky. Each detector module has a tube enclosing one or more sensing elements. The one or more sensing elements of the first detector module are configured to take weather condition readings from the first region of the sky. The one or more sensing elements of the second detector module are configured to take weather condition readings from the second region of the sky. In one aspect, the cloud detector is configured to detect cloud cover based on these weather condition readings. In some cases, the one or more sensing elements comprise an infrared radiation detector (e.g., thermopile) for measuring infrared radiation intensity and a photosensor element for measuring sunlight intensity.

A computer numerically controlled machine may include a source of electromagnetic energy. A beam of electromagnetic energy from the source may be delivered to a destination such as, for example, a material positioned in a working area of the computer numerically controlled machine. The beam of electromagnetic energy may be susceptible to interferences while traveling from the source to the destination. The computer numerically controlled machine may include a beam detector configured detect an interference of the beam by measuring a power of the beam of electromagnetic energy at a location between the source and the destination. An interference of the beam may be detected if the power of the beam is less than a threshold value. A controller at the computer numerically controlled machine may perform one or more actions in response to the beam detector detecting the interference of the beam of electromagnetic energy.

A system and method with AC coupling that reserves photodiode bandwidth in a biased configuration, allows optimal transimpedance amplifier performance, retains DC signal measurement capability, and does not introduce noise into the balanced detection signal.

A computer numerically controlled machine may include a source of electromagnetic energy. A beam of electromagnetic energy from the source may be delivered to a destination such as, for example, a material positioned in a working area of the computer numerically controlled machine. The beam of electromagnetic energy may be susceptible to interferences while traveling from the source to the destination. The computer numerically controlled machine may include a beam detector configured detect an interference of the beam by measuring a power of the beam of electromagnetic energy at a location between the source and the destination. An interference of the beam may be detected if the power of the beam is less than a threshold value. A controller at the computer numerically controlled machine may perform one or more actions in response to the beam detector detecting the interference of the beam of electromagnetic energy.

Provided are an apparatus and method for measuring quantum efficiency of a detector using a single pulse laser. Quantum efficiency of the measurement target detector may be measured from 420 nm to 1600 nm having uncertainty of 2% to 4% (K=2) by comparing the reference detector and the measurement target detector significantly different in sensitivity using a single laser pulse as a spectral light source. Also, it is possible to directly compare the two detectors with a significant difference in sensitivity through a very simple setup that causes a portion of a laser pulse output from a light source part to be absorbed by the reference detector and the laser pulse reflected from the reference detector to be irradiated to the measurement target detector.

A sensing system comprising a measurement sensor configured to detect electromagnetic radiation and a reference sensor configured to detect a source of measurement uncertainty. The sensing system further comprises a shield configured to reduce an interaction between the electromagnetic radiation and the reference sensor.