JPH03293863A - Sensor signal reader - Google Patents

Abstract

PURPOSE:To eliminate the influence of a temperature change by providing a read timing signal generating circuit which supplies a clamp pulse, which clamps the output of a sensor at a reference voltage in the output signal period of non-irradiation of light, to a clamping circuit. CONSTITUTION:A CCD sensor 1 is driven by a driving pulse phiM supplied from a read timing signal generating circuit 5 and generates a signal, and an output signal V0 is outputted in an effective picture element part where a photosensor 2 as a photodetector is irradiated with light, but a dark output VT due to the sensor temperature is outputted in an ineffective picture element part where it is not irradiated with light. The output signal of the CCD sensor 1 is amplified by an amplifier 3 and is clamped by a clamp pulse phiNC supplied from the read timing signal generating circuit 5 in a clamp generating circuit 4. That is, the voltage of the output signal period when the sensor 1 does not sense is clamped as the reference voltage. Thus, a dark output component VT dependent upon the temperature change is eliminated to obtain the signal which is not affected by the temperature change and proportional to only the extent of sensing like the quantity of irradiated light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sensor signal reading device, particularly to reading a sensor signal used in an image scanner or the like with little error.

[Prior art] Fig. 3 shows a CC camera used in image scanners, etc.
D sensor (1) is shown. This CCD sensor (1)
is equipped with a plurality of photosensors (2) arranged in parallel, which operate as light-receiving elements.

The output of this CCD sensor (1) is amplified by an amplifier (3) as shown in FIG.
At , the light is converted into a signal from which a signal proportional to the amount of light received by the photosensor (2) can be extracted. Therefore, the read timing signal generation circuit (5) supplies the drive pulse φM to the CCD sensor (1) and the clamp pulse φ to the clamp circuit (4). supply.

In such a conventional device, the CCD sensor (1) driven by the drive pulse φM generates the signal shown in FIG. 5(a).

That is, when light hits the CCD sensor (1) and the photosensor (2), which is a light receiving element, a signal (2) proportional to the intensity of the light is generated.

occurs.

This signal V. is amplified by the amplifier (3) and generated by the read timing generation circuit (5) as shown in FIG. 5(b).
The clamp pulse φC shown in FIG.
A signal V is converted into a signal clamped to a reference voltage va during the non-output period T1 of the sensor (1), and is proportional to the amount of light received by the photosensor (2) with reference to the voltage during the non-output period T1. is converted into a signal that can be extracted, that is, the signal shown in FIG. 5(c).

[Problem to be solved by the invention] However, the output signal Vo of the CCD sensor (1) is
The output when there is no amount of light received (dark output) should be zero, but in reality there is a temperature dependence as shown in FIG.

Therefore, when the output is as shown in Figure 6(a) when receiving light, the characteristics should be as shown in Figure 6(b) when the amount of received light is small, but due to the presence of dark power, the characteristics are as shown in Figure 6(c). Even if an error voltage VT shown in is generated and clamped to the reference voltage V for each -pixel, the output of the CCD sensor (1) will contain the error voltage v1. Therefore, in particular, the CCD sensor (
When used in the state of 1) where the amount of received light is small, the error voltage V caused by the temperature described above is equal to the sensor output V. cannot be ignored.

The present invention was made to solve the above problem, and an object of the present invention is to provide a sensor signal reading device in which the output of a sensor is not affected by temperature.

[Means for Solving the Problems] A sensor signal reading device according to the present invention has a reading timing signal generation circuit that sets the voltage during the output signal period in which the sensor is not sensitive to the reference voltage of the clamp circuit.

[Function] According to the device according to the present invention, by clamping the voltage during the unresponsive output signal period of the sensor as a reference voltage, the dark output which changes depending on the sensor temperature is clamped as a reference, and the sensor output signal is Superimposed temperature changes can be removed, thus eliminating errors.

[Example] Next, the present invention will be explained in more detail with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram of a sensor signal reading device according to an embodiment of the present invention. In the figure, the output of a CCD sensor (1) is led to a clamp circuit (4) via an amplifier (3). According to this invention, in particular, the read timing signal generation circuit (5) is configured to include a CCD sensor (1).
), a clamp pulse φNC whose reference voltage is the voltage value during the signal output period of the invalid pixel portion is supplied to the clamp generation circuit (4).

In the sensor signal reading device configured in this way,
The CCD sensor (1) is driven by a drive pulse φM supplied from a read timing signal generation circuit (5) and generates the signal shown in FIG. 2(a).

As is clear from this sensor output signal, the effective pixel portion where the foot sensor (2), which is the light receiving element of the CCD sensor (1), is irradiated with light outputs the output signal Vo, but the invalid pixel portion where the light is not irradiated outputs the output signal Vo. In the section, a dark output VT resulting from the sensor temperature is output. This dark output VT has temperature dependence as shown in FIG. 7, and the dark output v1 changes with temperature change.

Further, the output signal of the effective pixel section is also the same as the dark output Vr when no light is irradiated, and the output signal is the effective pixel section output signal V. will also have temperature dependence.

The output signal of the CCD sensor (1) is amplified by the amplifier (3) and then sent to the read timing signal generation circuit (5).
It is clamped by a clamp pulse φNC shown in FIG. 2(b) supplied by.

This clamp pulse φNC is intended to use the voltage value during the signal output period of the invalid pixel area, which is not irradiated with light, as a reference voltage, and is clamped to the reference voltage ■ by the clamp pulse φNC generated during the signal output period T2 of the invalid pixel area. And the second
The signal is converted into the signal shown in Figure (C).

Therefore, the output signal is the dark output V, which changes depending on the temperature.
Since the voltage is based on the voltage, the output signal of the effective pixel part is Vo-vT, and the output signal of the invalid pixel part is Vl-
■, −〇.

Therefore, the dark output component V1 that depends on temperature changes is removed, and a signal that is not affected by temperature changes and is proportional only to a sensitive amount such as the amount of light irradiation can be obtained.

Effects of the Invention As explained above, this invention has a structure that includes a read timing signal generation circuit that supplies the clamp circuit with a clamp pulse that makes the output of the sensor during the output signal period when no light is irradiated to the reference circumferential pressure. The output signal of the sensor is converted to a signal based on the town output that depends on temperature changes,
It is possible to read the sensor signal with the temperature change layer removed.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of a sensor signal reading device according to the present invention, FIGS. 2(a, ) to (C) are explanatory diagrams of sensor output signals according to the present invention, FIG. The figure is a block diagram of a conventional device, and Figure 5 (a
) to (c) are conventional signal explanatory diagrams, and Fig. 6 (a) to (
c) is an explanatory diagram of a conventional signal error, and FIG. 7 is a diagram of dark output temperature characteristics of a CCD sensor. In the figure, (1) is a CCD sensor, (2) is a photo sensor,
(3) is an amplifier, (4) is a clamp circuit, and (5) is a read timing signal generation circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] A sensor that detects light; a clamp circuit that compares the output of this sensor with a reference voltage and generates a signal indicating the amount of sensitivity of the sensor from the difference; and a clamp circuit that instructs the sensor to read at a predetermined timing, and A sensor signal reading device comprising: a reading timing signal generation circuit that instructs to use a value during a signal output period in which the sensor is not detecting light as a reference voltage.