Device for receiving light used in CCD image sensor or the like

Claim 1

A light receiving device comprising: a photodiode, having spectral-response characteristics that change depending on a reverse bias state, for both photoelectric conversion and electron charge accumulation, said photodiode being maintained in a floating state after said reverse bias is reset; a switching element for periodically providing a reverse bias resetting potential to said photodiode; a comparator for comparing a potential of said photodiode with a threshold potential corresponding to predetermined spectral-response characteristics; and a counter for counting a time duration from when said photodiode is reset by said switching element to when the potential of said photodiode exceeds said threshold potential, and outputting the time duration as a numerical value corresponding to a quantity of light incident on said light receiving device.

Claim 3

A method for driving a light receiving device having a comparator and a counter, in which a reverse bias reset potential is provided to a photodiode by periodically applying a reset potential to said photodiode and during a time period from immediately after a provision of a first reset potential to a time when a next reset potential is provided, said photodiode receives light and is maintained in a floating state and undergoes a reverse bias attenuation change operation responsive to quantities of received light, said method comprising steps of: providing a threshold potential to said comparator; inputting, to said comparator, an output potential of said photodiode; inputting an output of said comparator to said counter; counting a time duration from when said first reset potential is provided to when said output potential of said photodiode equals said threshold potential; and outputting said time duration as numerical value each time said reset potential is provided, said counting of the time duration being carried out by counting a number of pulses of a master clock inputted to a clock input terminal of said counter, and said potential of the photodiode and said threshold potential being compared non-destructively at a plurality of levels whereby spectral-response characteristics of the light incident on said light receiving device are obtained.

Claim 4

A method for driving a light receiving device having a comparator and a counter, in which a reverse bias reset potential is provided to a photodiode by periodically applying a reset potential to said photodiode and during a time period from immediately after a provision of a first reset potential to a time when a next reset potential is provided, said photodiode receives light and is maintained in a floating state and undergoes a reverse bias attenuation change operation responsive to quantities of received light, said method comprising steps of: providing a threshold potential to said comparator; inputting, to said comparator, an output potential of said photodiode; inputting an output of said comparator to said counter; counting a time duration from when said first reset potential is provided to when said output potential of said photodiode equals said threshold potential; and outputting said time duration as numerical value each time said reset potential is provided, said counting of the time duration being carried out by counting a number of pulses of a master clock inputted to a clock input terminal of said counter, and said potential of the photodiode and said threshold potential being compared non-destructively at a plurality of levels whereby spectral-response characteristics of the light incident on said light receiving device are obtained.