JPH04298155A - Image sensor - Google Patents

Abstract

PURPOSE:To obtain an output signal Vout with simple configuration without noise by superimposing a signal inverted with noise based on a clock signal CLK onto an output line 4 to cancel the noise with the inverted signal. CONSTITUTION:The self-scanning type image sensor comprising plural photoelectric conversion elements 1, an output line 4 through which a photoelectric conversion signal from the photoelectric conversion element 1 is outputted, a switching element 2 connecting each photoelectric conversion element 1 to the output line selectively, and a scanning circuit 3 receiving a clock signal CLK to drive sequentially each switching element 2 is provided with a noise cancellation wire line 7 having a prescribed capacitance Cs with the output line 4 and the noise canceling wire line 7 is provided with an inverting signal generating circuit 8 outputting a inverted signal CKs of the clock signal CLK.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an image sensor.
In particular, the present invention relates to an image sensor having means for removing noise in an output signal.

0002

[Prior Art and Problems Therewith] As shown in FIG. 5, a conventional image sensor includes a photoelectric conversion element 51 consisting of a photodiode and a storage capacitor, a switching element 52 consisting of a switching transistor for switching this photoelectric conversion element 51, A scanning circuit 53 that sequentially drives each switching transistor using a start signal and a clock signal input from the outside, an output line 54 that outputs a signal from the photoelectric conversion element 51, and a bias power supply that applies a reverse bias voltage to the photoelectric conversion element 51. 55, the switching element 5 is
2 are sequentially driven, and the charges accumulated in the photoelectric conversion element 51 portion are sequentially read.

FIG. 6 shows the operation sequence in the above circuit.
Shown below. In FIG. 6, (a) is the sensor driving clock signal CLK, (b) is the crosstalk Vn from the clock signal CLK to the output line 54, and (c) is the output line 5.
4. Photoelectric conversion signal Vp when there is no crosstalk on
(d) is a composite waveform of (b) and (c) above. That is, in this type of image sensor, it is ideal that the photoelectric conversion signal as shown in FIG. 6(c) appears as it is on the output line 54, but in a circuit as shown in FIG. Noise as shown in FIG. 6(b) is generated from the clock signal CLK to the output line 54 via the capacitance Ch between the clock signal CLK and the line 54. Such noise rides on the photoelectric conversion signal shown in FIG. 6(c), resulting in a signal as shown in FIG. 6(d) as an output signal.

[0004] Normally, the photoelectric conversion output signal of an image sensor is an extremely small signal of several mV, so noise from the scanning circuit 53 crosstalks to the output line 54 of the sensor, significantly reducing the S/N ratio. was. Generally, if noise countermeasures are not taken, the crosstalk Vn is ten times or more larger than the photoelectric conversion signal Vp, and the sensor cannot be used as an image sensor.

In order to solve such problems, for example, in Japanese Patent Laid-Open No. 51-96220, as shown in FIG. 7, a start signal Es and clock signals φ1 and φ2 are input to perform photoelectric conversion according to optical information. A self-scanning photoelectric conversion element 71 that outputs a signal V1, and a dummy element 72 that inputs only clock signals φ1 and φ2 and outputs a signal V2 that is the same as noise.
At the same time, the photoelectric conversion signal V1 and the signal V2, which is the same as the noise, are input to the differential amplifier circuit 73, and the difference between the photoelectric conversion signal V1 and the signal V2, which is the same as the noise, is calculated. It has been proposed to remove the noise caused by

However, in this conventional image sensor, a dummy element 72 and a differential amplifier circuit 73 must be provided for each light-receiving element 71 or for each plurality of light-receiving elements 71, making the manufacturing process complicated and reducing the manufacturing yield. There was a problem with the decline.

[0007]

[Object of the Invention] The present invention was devised in view of the above-mentioned problems, and by removing noise without forming dummy elements, the manufacturing process is simplified and the manufacturing yield is reduced. The purpose is to provide an image sensor that does not

[0008]

[Structure of the Invention] According to the present invention, a plurality of photoelectric conversion elements,
An output line that outputs a photoelectric conversion signal from this photoelectric conversion element, a switching element that selectively connects each photoelectric conversion element to the output line, and a scanning circuit that receives a clock signal for sequentially driving each switching element. In a self-scanning image sensor consisting of a noise canceling wiring line having a certain capacitance between the output line and the noise canceling wiring line, an inverted signal that outputs a signal obtained by inverting the clock signal to the noise canceling wiring line. An image sensor is provided which is characterized in that it is provided with a generating circuit, thereby achieving the above object.

[0009]

[Operation] By configuring as described above, a signal that is inverted from the noise based on the clock signal can be placed on the output line, and by canceling out the noise and this inverted signal, a noise-free output signal can be easily generated. It can be obtained by configuration.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a diagram showing the electrical circuit configuration of an image sensor according to the present invention, in which 1 is a photoelectric conversion element consisting of a photodiode and accumulated charge, and 2 is a switching element consisting of a switching transistor that switches the photoelectric conversion element 1. , 3 is a start signal ST input from the outside.
and each switching element 2 by the clock signal CLK.
4 is an output line for outputting a signal from the photoelectric conversion element 1 , and 5 is a bias power supply for applying a reverse bias voltage to the photoelectric conversion element 1 .

In the image sensor of the present invention, similarly to the conventional example, the switching element 2 is sequentially driven by the scanning circuit 3 to which the clock signal CLK and the start signal ST are input, and the accumulated charge in the photoelectric conversion element 1 is removed. The data is read sequentially from output line 4.

A certain capacitance Cs is connected between the output line 4 and the input line of the clock signal CLK.
A noise-cancelling wiring line 7 electrically connected to the noise-cancelling wiring line 7 is provided, and an inverted signal generating circuit 8 that outputs a signal obtained by inverting the clock signal CLK is connected to this noise-cancelling wiring line 7. This inverted signal generation circuit 8 may be formed by externally attaching a general-purpose IC chip composed of an inverter or the like.

FIG. 2 shows the operation sequence of the above circuit. In the figure, (a) is the clock signal C for driving the sensor.
LK, (b) is the crosstalk Vn from the clock signal CLK to the output line 4, (c) is the photoelectric conversion signal Vp when there is no crosstalk to the output line 4, (d) is the inverted signal generation circuit 8 (e) is the crosstalk Vs from the inverted signal generation circuit 8 on the output line 4, (f) is the output signal of the output line 4 which is a combination of (b), (c), and (d) above. It is Vout.

Output signal C from the inverted signal generating circuit 8
Ks is a signal obtained by completely inverting the clock signal CLK input to the scanning circuit 3 (see FIG. 2(d)), and the output signal CKs from the inverted signal generating circuit 8 passes through the capacitor Cs to the output line 4. and crosstalk noise V
The noise Vs is completely inverse to n (see FIG. 2(e)). That is, the capacitance of the capacitor Cs should be set so that the noise level of the crosstalk Vn from the clock signal CLK to the output line 4 and the crosstalk Vs from the inverted signal generation circuit 8 to the output line 4 are equal. Bye.

In this way, the noise on the output line 4 is canceled by the crosstalk Vn from the clock signal CLK to the output line 4 and the crosstalk Vs from the inverted signal generation circuit 8 to the output line 4. As a result, a sensor output with a good S/N ratio can be obtained (see FIG. 2(f)).

FIG. 3 is a diagram showing another embodiment of the output portion of the inverted signal generating circuit 8. In FIG. In this embodiment, the output signal of the inverted signal generating circuit 8 is divided by a fixed resistor 9 and a variable resistor 10, and the amplitude of the output signal CKs of the inverted signal generating circuit 8 is finely adjusted by varying the resistance value of the variable resistor 10. I'm trying to make it possible.

FIG. 4 shows the structure of the noise canceling wiring line 7 portion. FIG. 3(a) is a plan view, and FIG. 1(b) is a sectional view. An output line 4 made of aluminum or the like, an insulating film 12 made of a silicon oxide film or a silicon nitride film, and a noise canceling wiring line 7 made of aluminum or the like are sequentially laminated on a substrate 11 made of glass or the like. Therefore, the capacitance Cs at the insulating film 12 portion
is formed.

[0018]

As described above, according to the image sensor of the present invention, a wiring line having a certain capacitance is provided between the output line and a signal obtained by inverting a clock signal is output to this wiring line. Since an inverted signal generation circuit is provided, a signal that is inverted from the noise based on the clock signal can be placed on the output line, which cancels out the noise and this inverted signal, making it possible to easily create a noise-free output signal. This makes it possible to provide an image sensor that can be obtained using

[0019]

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the image sensor of the present invention.

[Figure 2] Operation time sequence in Figure 1

FIG. 3 is a block diagram showing another embodiment of the present invention.

[Figure 4]
A diagram showing main parts of the structure of the image sensor of the present invention

[Figure 5]
Circuit diagram showing a conventional image sensor

[Figure 6] Operation time sequence in Figure 5

[Figure 7] Block diagram showing another conventional image sensor

[
Figure 8: Operation time sequence in Figure 7

[Explanation of symbols]

1. Photoelectric conversion element 2. Switching element 3. Scanning circuit 4. Output line 7. Wiring line for noise cancellation 8. Inverted signal generation circuit CLK, clock signal

Claims (2)

[Claims] 1. A plurality of photoelectric conversion elements, an output line for outputting a photoelectric conversion signal from the photoelectric conversion elements, a switching element for selectively connecting each photoelectric conversion element to the output line, and sequentially driving each switching element. In a self-scanning image sensor consisting of a scanning circuit to which a clock signal is input, a noise-cancelling wiring line having a certain capacitance is provided between the output line and the noise-cancelling wiring line. An image sensor comprising an inverted signal generation circuit that outputs a signal obtained by inverting a clock signal. 2. The image sensor according to claim 1, wherein a fixed resistor and a variable resistor are provided at the output section of the inverted signal generation circuit, and a signal obtained by inverting the clock signal is output from between the fixed resistor and the variable resistor. An image sensor characterized by being provided with an output adjustment circuit.