3D Sensing Defining Requirements for Electrical Test of Optical Devices

3D sensing augments a camera's object & facial recognition.

3D sensing is a depth sensing technology that augments camera capabilities for facial and object recognition in augmented reality, gaming, autonomous driving and a wide range of applications.

  • One way to sense 3D is using structured light. Coherent infrared light is transmitted onto an object with a structured pattern. The reflected light can be decoded to construct a 3D image.
  • Another way to sense 3D is to use Time of Flight (ToF). A light source transmits a series of infrared light and the photon phase difference to the light bounced off an object is used to sense the proximity of an object.




Diode-based optical devices enable 3D sensing.

Diode-based devices such as laser diodes, high brightness LEDs (HBLED), and photodiodes (PD) are key optical devices that enable 3D sensing.

  • Laser diodes are capable of outputting a narrow and coherent light beam. Two common types of laser diodes are edge emitter laser (EEL) and the fast-growing VCSEL (vertical cavity surface emitting laser). VCSEL combines the advantage of low cost manufacturability, optical efficiency, temperature stability, and large 2D arrays for increased power. EEL operates at a higher frequency that can travel hundreds of miles without loss in a fiber medium commonly for optical communication.
  • HBLEDs or LEDs disperse incoherent light in a wide pattern. They are the most efficient source of high quality white light, hence great for illumination. Efficiency droop, limited modulation capability, and resolution make them only suitable for some applications.
  • PDs detect and convert light into current. Very sensitive instruments for low PD current measurement are required to characterize the full range light intensity of the light source properly.


Keithley instruments perform electrical testing on diode-based devices.

Wavelength stability over the entire operating temperature of these devices is critical to maintaining precision and minimize noise in received signals. Electrical efficiency measurement through precision trigger and synchronization of pulse width and duty cycle further optimize the required intensity and resolution of illumination. These directly impact the heat dissipation, power consumption, and battery life of the end system.

Keithley has an extensive portfolio of instruments for electrical tests, including light intensity, forward voltage, lasing threshold current, quantum efficiency, dark current, the presence of “kink” or kink test, slope efficiency, thermistor resistance, temperature, capacitance, and the full spectrum of L-I-V pulse testing of laser diodes and HBLEDs.

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