JPS6359629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an image sensor device that optically reads information at high speed and with high accuracy by making full use of IC circuit technology.

Conventional Structure and Problems Conventional optical reading elements include silicon vidicon, MOS target vidicon, and the like. Since the access function for sequential readout of these is performed by deflecting the electron beam,
Although it has the advantage of being easy to perform with high resolution, it cannot be made entirely solid-state, so it has problems with miniaturization, low power consumption, etc. On the other hand, all-solid-state chemical reading elements include various image sensors such as photodiode arrays or matrices, phototransistor arrays or matrices, photoconductor arrays or matrices, CCD arrays or matrices, and the like. In this case, in order to read the information sequentially, a function (scanning circuit) is required to access each sensor in each array or matrix.
If the sensor section and the scanning section are mounted as separate parts, the wiring between them would be complicated in high-resolution elements, so the sensor section and the scanning section are integrated and formed on a silicon chip. Examples of this type include MOS image sensors,
There are CCD image sensors, etc. These devices consist of an optical sensor section and a scanning section based on MOS integrated circuit technology, and although they have high resolution, they have the drawback of relatively slow reading speed.

In addition, based on bipolar integrated circuit technology, the sensor section and scanning section are formed on the same chip, eliminating the drawbacks of the MOS image sensor and CCD image sensor, and enabling high-speed, high-precision reading. An image sensor etc. can be considered. As methods for scanning each sensor in this bipolar image sensor, there are methods using a shift register and methods using a gate circuit. The scanning method using a shift register is simple because the selection signal input to be accessed is only the clock signal input, but the number of elements increases, causing a decrease in yield. On the other hand, in the decoding method using a gate circuit, the selection signal input to be accessed is somewhat more complicated than in the scanning method using a shift register, but it has the advantage of significantly reducing the number of elements and improving yield. However, conventionally, this decoding method has the following drawbacks.

1 to 3 show specific configurations of conventional decoding systems. 1 is a sensor section in which phototransistors (or photodiodes) are arranged; 2 is a video signal output line of the sensor section 1; 3 is a load resistor;
4 is a ground (reference potential). 5, 6...12
is a multi-input AND circuit, and 13, 14, . . . , 18 are selection signal input lines. The binary code signals a to f of FIG. 2 are applied to each of the selection signal input lines 13 to 18, respectively, and each sensor of the sensor section 1 of FIG. 1 is sequentially selected. FIG. 3 depicts temporal changes in switching levels caused by the binary code signals shown in FIGS. 2a to 2f during access switching, in correspondence with FIG. 2. At time _t1 , the polarities of e and f in FIG. 2 are reversed, and at time _t2 , the polarities of c, d, e, and f are reversed. Similarly below
t ₃ has 2 inputs, t ₄ has 6 inputs, t ₅ has 2 inputs, t ₆
The number of inputs whose polarity is inverted varies depending on the time, such as 4 inputs at _t7 , 6 inputs at _t8, and so on. Note that switching noise, which is approximately proportional to the number of inputs whose polarity is reversed during access switching, is generated from the internal diodes that constitute each of AND circuits 5 to 12, but the number of signals whose polarity is reversed in this way is proportional to the number of inputs whose polarity is reversed. If the switching noise is different, the level of switching noise superimposed on the video signal will differ depending on the time, and variations will occur in the sensitivity of the video signal output. Note that in Figures 1, 2, and 3, the case where 8 phototransistors (or photodiodes) are arranged is explained, but if the number increases to 16, 32, 62, etc., the selection signal input As the number of lines increases to 8, 10, 12, etc., the number of inputs whose polarity is inverted during access switching further increases, and the variation in sensitivity becomes even larger.

Purpose of the Invention The present invention provides an image sensor in which the switching noise level is constant during any access switching when scanning each sensor using a decoding method, and the sensitivity of the video signal output is uniform without temporal variation. The purpose is to

Configuration of the Invention The image sensor device of the present invention sequentially accesses a plurality of photosensors using a gate circuit output to read out an optical signal in a charge accumulation mode, and also connects the gate circuit to a selection signal input that changes according to a Gray code. The present invention is characterized in that it is configured so that an optical signal output can be sequentially obtained in response to the received signals.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 4 to 8.

FIG. 4 is a configuration diagram of the image sensor of the present invention.
This is AND circuits 5 to 12 and selection signal input line 1
Only the connections 3 to 18 differ from FIG. 1.

a to f in FIG. 5 are selection signal input lines 13 to 18;
FIG. 6 is a switching level diagram for the selection signals a to f in FIG. 5. In addition, Fig. 6 shows the temporal change in the switching level that occurs during access switching as shown in Fig. 5.
It is drawn in correspondence with the figure.

_The selection signals shown in _FIG . Therefore, the level of switching noise is always constant. In other words, the sensitivity of the video signal output is uniform regardless of time.

In the above embodiment, the case where eight phototransistors are accessed is shown, but if the Gray code is used, even if the number increases, the uniformity of the sensitivity of the video signal output will not change.

7 and 8 show the specific configuration of FIG. 4. FIG. 19 is a counter circuit, 20 is a binary code to Gray code converter (hereinafter referred to as a converter), and 21 is an image sensor having the configuration shown in FIG.
When a clock pulse is applied to the counter input line 31, a selection signal is outputted to the counter output line 32 in the form of a binary code. This binary code selection signal is converted into a Gray code selection signal by the converter 20, and is applied to the selection signal line 33 of the image sensor 21. In this way, a video signal of uniform sensitivity can be obtained on the video signal output line 2 by simply supplying the clock pulse to the counter circuit 19.

FIG. 8 shows a block diagram of the converter 20 in the case of 4 bits. A Gray code output 36 is obtained by inputting the binary code input 34 to exclusive OR circuits 35a, 35b, and 35c.

In the above embodiment, the sensor section 1 of the image sensor 21 is a photodiode or a phototransistor, but the sensor section is not limited to a photodiode or a phototransistor, but may be an optical sensor that senses light and generates a current. Good to have.

Effects of the Invention As is clear from the following description, according to the image sensor device of the present invention, since each optical sensor is scanned by decoding using a gray code, switching noise at the time of access switching can be made uniform. This makes it possible to make the video output signal sensitivity uniform and reduce variations in sensitivity. In addition, by configuring the gate circuit that accesses each sensor using a counter, a binary code → Gray code converter, and an AND circuit, it can be accessed by simply supplying a clock signal to the counter circuit, making the configuration simple. It is.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional image sensor device.
2 is a waveform diagram of the main part of FIG. 1, FIG. 3 is a level diagram of switching noise generated during access switching in FIG. 1, and FIGS. 4 to 8 show an embodiment of the present invention. FIG. 4 is a configuration diagram of the image sensor device of the present invention, FIG. 5 is a waveform diagram of the main part of FIG. 4, FIG. 6 is a level diagram of switching noise generated during access switching in FIG. 4, and FIG. FIG. 5 is a block diagram of the signal waveform generation process, and FIG. 8 is a block diagram of the main part of FIG. 7. 1...Sensor section, 2...Video signal output line,
3...Load resistance, 5-12...AND circuit, 13
~18...Selection signal input line, 19...Counter circuit, 20...Binary code to Gray code converter, 21...Image sensor, 31...Counter input line, 32...Counter output line, 3
3... Selection signal line, 34... Binary code input, 35a, 35b, 35c... Exclusive OR circuit, 36... Gray code output.

Claims (1)

[Claims] 1. A plurality of optical sensors are sequentially accessed by gate circuit outputs to read optical signals in a charge accumulation mode, and the gate circuit is configured to receive a selection signal input that changes according to a Gray code. An image sensor device configured to sequentially output optical signals. 2. A counter circuit that outputs a selection signal that changes according to a binary code based on a clock signal, and a binary code → Gray code conversion that converts the gate circuit into a gray code selection signal. container and this binary
2. The image sensor device according to claim 1, further comprising an AND circuit which receives the output of the code→Gray code converter and sequentially accesses the output.