Laser Ranging And Lidar APD Photoreceivers

The GD series of laser-ranging photoreceivers—which integrates  high-performance InGaAs avalanche photodiodes  (APDs), custom-designed CMOS application-specific integrated  circuits (ASICs), high-voltage APD bias circuits, and programmable  processing circuits—provides flexible system integration and reliable  performance, all in a small TO-8 package.  To accommodate new applications and changing operating  conditions, an embedded microcontroller allows quick configuration  of the photoreceiver and optimization of performance as a function  of ambient temperature—without using thermoelectric cooling.  Factory-calibrated settings automatically configure the detector for  one of several modes programmed into the memory of each  photoreceiver. For each operating temperature, these modes  include: constant gain, optimal sensitivity, optimal noise equivalent  input (NEI), and constant responsivity.  To achieve the desired pulse-detection probability and false-alarm  rate (FAR), the threshold voltage of the detector can be manually  adjusted. To reduce false alarms caused by scattering, the threshold  can be adjusted as a function of laser flight time using the timevariable threshold (TVT).  The photoreceiver outputs a differential digital signal for both the rising  edge and the falling edge of a pulse. This allows time-over-threshold  (TOT) correction to be used where range-walk errors would otherwise  result from variations in pulse amplitude. The analog output allows  signals to be digitized and pulse processing to be performed.  A range of APD diameters and immersion lens options are available.