JPS5926702Y2 - solid-state imaging device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for removing fixed pattern noise in a solid-state imaging device.

FIG. 1 shows the circuit configuration of a conventional solid-state imaging device.

Optical signal charges accumulated in a photodiode 1 formed by a Si substrate of one conductivity type and a diffusion region of an opposite conductivity type are transferred to an MO connected to a gate line 3 selected by a scanning circuit 2.
S) Vertical output line 5 via transistor (MO8T) 4
Move to.

The charges transferred to the terminal 5 are further outputted to the horizontal output line 8 via the MO8T7 selected by the scanning circuit 6, and the optical signal is read out from the terminal Out through the detection resistor 9 connected to the video voltage power supply 10.

FIG. 2 shows the voltage waveform at each point in the circuit of FIG. 1, where OYl is the output of scanning circuit 2, OX1 to
X3 is the output of the scanning circuit 6, and Out is the output waveform of the output line 8.

As shown in this figure, the Out terminal is connected to the optical signal (S,, S2...) of each picture element and the switch MO3T (
For example, spike noise caused by MO3T 7) is superimposed.

This variation in noise waveform causes fixed pattern noise.

FIG. 3 shows the circuit configuration of a solid-state imaging device according to the first embodiment of the present invention.

31 to 40 are the same as 1 to 10 in FIG. 1, respectively,
41 is a changeover switch, 42 is a delay element, and 43 is a differential amplifier.

FIG. 4 shows the voltage waveform at each point for the circuit configuration of FIG. 3.

Output pulses of the scanning circuit 36 (OXo, OX2...
) in one horizontal scanning pulse period as shown in the figure, the signal output line 38 (Out)
, an optical signal and noise (Sl+N1) are output at the first OX1 pulse timing, and only noise (N1) is output at the second OX1 pulse timing.

A switch 41 switches the signals that are sequentially output in this way.
If we temporally separate the optical signal into the noise (Si + N, ) component and the noise (Ni) component only, they are 0ut1.0u, respectively.
A waveform like t2 is obtained.

Also, the signal of 0ut1 is converted to 0ut1' by the delay element 42.
It is delayed to match the timing of 0ut2 as shown in FIG.

When the difference between the delayed Si+Nz and N1 is taken by the differential amplifier 43, only the signal component can be detected from the output 0ut3.

Therefore, this method can eliminate fixed pattern noise caused by variations in noise waveforms, which has been a problem in the prior art.

FIG. 5 is an embodiment of FIG. 2.

51 to 63 are the same as 31 to 43 in FIG.
It forms a buffer circuit for transmitting information to the gate of 57.

Fig. 6 shows the voltage waveform at each point in the circuit of Fig. 5, and even when the number of output pulses from the scanning circuit is one, the number of output pulses is changed to two by pulse GP. be.

FIG. 7 shows another embodiment.

71 to 73 are the same as 41 to 43 in FIG. 3, respectively, and 74 is a preamplifier.

FIG. 8 shows another embodiment.

81 to 84 are respectively the same as 71 to 74 in FIG. 7, and 85 is a sample and hold circuit.

FIG. 9 shows another embodiment.

91 to 95 are the same as 81 to 85 in FIG. 8, respectively, but are arranged differently.

[Brief explanation of drawings]

Figure 1 is a schematic circuit diagram of a conventional solid-state imaging device, and Figure 2 is a schematic diagram of a conventional solid-state imaging device.
FIG. 3 is a schematic circuit diagram showing the first embodiment of the solid-state imaging device of the present invention, and FIG. 4 is a pulse waveform in the device shown in FIG. 3. Figure 5 is a schematic circuit diagram showing the second embodiment of the solid-state imaging device of the present invention, and Figure 6 is a diagram showing the pulse waveform and voltage waveform at each location in the device shown in Figure 5. 7, 8, and 9 are conceptual diagrams showing other embodiments of the solid-state imaging device of the present invention. 31...Photodiode, 32...Vertical scanning circuit, 33...Gate line, 34...
・MO3) transistor for vertical switch, 35...
・Vertical signal line, 36...Horizontal scanning circuit, 37.
...MO3) transistor for horizontal switch, 38.
...Horizontal signal line.

Claims (1)

[Scope of utility model registration request] In a solid-state imaging device that connects a photodiode and a switch element and extracts a detection signal from the photodiode by opening and closing the switch element, a first pulse and a second pulse are continuously output within one horizontal scanning pulse period. A circuit to
The circuit comprises a circuit that calculates the difference between a first output signal obtained by making the switch element conductive with a first pulse and a second output signal obtained by making the switch element conductive with a second pulse. Characteristic solid-state imaging device.