Low-level light detector and low-level light imaging apparatus

Abstract

A low-level light detector includes an avalanche photodiode (APD) to which is applied a bias voltage adjusted to produce a multiplication factor of not more than 30, and a capacitor for accumulating carriers produced by light in the APD and multiplied using the APD characteristics, the capacitor being connected to the avalanche photodiode. The detector detects the intensity of light impinging on the avalanche photodiode by periodically reading the capacitor voltage and obtaining time-based differences in the voltage, or by resetting the capacitor voltage to a predetermined voltage each time the capacitor voltage is read.

1 . A low-level light imaging apparatus, comprising: 
 avalanche photodiodes with a bias voltage adjusted to produce a multiplication factor of up to 30, said avalanche photodiodes being arranged in a one-dimensional array or a two-dimensional array;    biasing means of the avalanche photodiode;    outputting means of a capacitor voltage change; and    control means of the biasing and outputting means,    wherein the low-level light imaging apparatus detects an intensity of light impinging on an avalanche photodiode by reading amounts of carriers produced and multiplied in each avalanche photodiode.    
     
     
         2 . A low-level light imaging apparatus, comprising: 
 avalanche photodiodes with a bias voltage adjusted to produce a multiplication factor of up to  30 , said avalanche photodiodes being arranged in a one-dimensional array or a two-dimensional array;    a capacitor connected to each avalanche photodiode for accumulating carriers produced and multiplied in each avalanche photodiode;    biasing means of the avalanche photodiode;    reading means of a capacitor voltage change; and    control means of the biasing and outputting means,    wherein the low-level light imaging apparatus detects an intensity of light impinging on an avalanche photodiode by reading capacitor voltage.    
     
     
         3 . A low-level light imaging apparatus, comprising: 
 avalanche photodiodes with a bias voltage adjusted to produce a multiplication factor of up to 30, said avalanche photodiodes being arranged in a one-dimensional array or a two-dimensional array;    a capacitor connected to each avalanche photodiode for accumulating carriers produced and multiplied in each avalanche photodiode;    biasing means of the avalanche photodiode;    outputting means of a capacitor voltage change; and    control means of the biasing and outputting means,    wherein the low-level light imaging apparatus detects an intensity of light impinging on an avalanche photodiode by resetting capacitor voltage to a predetermined voltage each time it reads the capacitor voltage, and by reading the capacitor voltage.