Abstract:
Light-emitting devices, such as LEDs, are tested using a photometric unit. The photometric unit, which may be an integrating sphere, can measure flux, color, or other properties of the devices. The photometric unit may have a single port or both an inlet and outlet. Light loss through the port, inlet, or outlet can be reduced or calibrated for. These testing systems can provide increased reliability, improved throughput, and/or improved measurement accuracy.
Abstract:
The stabilization of a light-emitting diode (LED) calibration standard includes a light-emitting diode (LED), or an array of LEDs; a cylindrical hood surrounding the LED; an interior baffle for keeping the light output of the LED, and ambient light from behind the LED, from escaping to the other side; a photodetector for receiving the light output of the LED and generating a signal proportional to luminous output; and a hood surrounding the photodetector. A variable current source receives the signal and stabilizes the LED light output by adjusting the operating current of the LED to maintain a constant light output from the LED.
Abstract:
The present disclosure provides methods and apparatus for testing light-emitting diodes (LEDs), for example, measuring the optical radiation of an LED. In a method, a pulse-width modulated signal is provided to the LED. One or more characteristics of the PWM signal are varied so as to provide a forward voltage, Vf, corresponding to a target junction temperature, Tj, of the LED. The optical radiation of the LED is measured when the LED obtains the target junction temperature.
Abstract:
An apparatus for the controlled deposition of particles onto a film or a substrate, including: a frame arranged to support a film or a substrate having first and second surfaces facing in first and second opposite directions, respectively; a nozzle arranged to emit a stream of particles charged with a first polarity toward the first surface; and an electrode: charged with a second polarity, opposite the first polarity, and located adjacent the second surface; and arranged to attract the stream of particles to a region of the first surface. A line orthogonal to the first surface passes through the region and the electrode.