JPH02121580A - Image sensor - Google Patents

Abstract

PURPOSE:To simultaneously read the video signals out of the picture elements of the same row and to send these signals to each column independently of each other and with no mutual mixture by using a low input impedance circuit which gives a sequential access to a common collector and at the same time suppresses the potential fluctuation of the output line of each column. CONSTITUTION:An output terminal 4 acquires the video signals from the picture elements of a 1st column, and an output terminal 5 acquires the video outputs from the picture elements of a 2nd column respectively. Then an output terminal 6 acquires the video signals from the picture element of a 3rd column, and an output terminal 7 acquires the video outputs from the picture elements of the n-th column. Each of these output terminals sends the video signals to the circuit of the next stage via a low input impedance circuit 8. In other words, the video signals are taken out while the potential fluctuation of each output terminal is suppressed. In such a constitution, the video signals of the picture elements sharing a common access terminal can be read out of other terminals of each picture element at one time and independently of each other just by selecting a certain row, that is, giving an access to a certain common access terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image sensor that makes it possible to read video information faithfully at high resolution and at high speed.

2. Description of the Related Art In general, in an image sensor, only one pixel's video signal is read out in - times of access.

Therefore, in order to read out video information at high speed, it is not possible to obtain the outputs of a plurality of pixels in one access. The reason why only one pixel is read in − times of access is −
Between pixels that share an access terminal in terms of S, signal carriers based on independently incident light can maintain their independence because their values are averaged.

- Photodiodes are often used as pixels in boat fishing, and this also applies to this case.

Problems to be Solved by the Invention If a photodiode, which is normally used as a pixel, is used, and one terminal is shared and used as an access terminal, and each of the other terminals is made an independent output terminal, the potential due to photoexcited carriers can be reduced. Since the changes are averaged among the pixels that share the access terminal, it is virtually impossible to read out multiple pixels at the same time faithfully to the original and with high resolution in - times of access.

Means for Solving the Problem Phototransistors are used as pixels arranged in a matrix, and the emitters and vines of the pixels belonging to the same example are connected in common to form an output line, and the collectors of the pixels belonging to the same row are connected in common. share a different type of semiconductor isolation region with the substrate, and by sequentially accessing the common collector and via a low input impedance circuit that suppresses fluctuations in the potential of the output line of each column, the same row The video signals from the pixels can be independently read out to the output lines of each column without being mixed with each other, and thus the video signals can be read out at high speed.

Effect of the Invention With the above-described configuration, the present invention makes it possible to simultaneously and independently read out the video signals of each pixel sharing the common access terminal from other terminals of each pixel by simply accessing the common access terminal. It is.

EXAMPLE Hereinafter, an image sensor according to an example of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of the configuration of an image sensor for implementing the present invention. 1 is a scanning circuit that selects a row from which to read out a video signal; 2 is an access switch column that switches the common line of the row selected by the scanning circuit; 3 is a phototransistor in pixel units, which is a matrix of m rows and n columns. arranged in a shape.

4 is an output terminal for obtaining video signals from pixels belonging to the first column, 5 is an output terminal for obtaining video output from pixels belonging to the second column, and 6 is an output terminal for obtaining video signals from pixels belonging to the third column. , 7 are output terminals for obtaining video output from pixels belonging to the n-th column. Each output terminal sends out a video signal to the next stage circuit via the low input impedance circuit 8. In other words, it means extracting the video signal while suppressing fluctuations in the potential of each output terminal. By simply selecting a row with such a configuration, that is, by accessing one of the common access terminals (consisting of the collector in Figure 1), the video signals of each pixel sharing that access terminal can be transferred to each pixel and other pixels. It is possible to simultaneously and independently read data from the terminals (consisting of emitters in FIG. 1). That is, a video signal of n pixels can be obtained by - times of access.

First, it will be explained that each output terminal must be received by a low input impedance circuit and fluctuations in the potential thereof must be suppressed, and that it is effective to use a phototransistor as a pixel. If the potential of any one output terminal fluctuates, it is obvious that the other output terminal potentials will also fluctuate, since capacitive coupling naturally exists between the respective output terminals. That is, high resolution simultaneous reading of video signals from each output terminal is not possible. Therefore, in order to suppress fluctuations in the potential of each output terminal, receiving each output terminal with a low input impedance circuit is essential for faithfully reading video information by simultaneously reading video signals from each output terminal. . However, suppressing fluctuations in each output terminal potential means that each output terminal potential remains fixed, and the access terminal potentials are the same between pixels that share an access terminal. In the case of photodiodes, the potentials at both ends of these pixels are exactly the same, and the video information of each pixel that shares these access terminals is averaged.
Therefore, if a phototransistor is used as a pixel, the presence of a base layer prevents averaging of video information between pixels that share an access terminal. As can be seen from the above, it is extremely important to suppress fluctuations in the potential of each output terminal and to use phototransistors as pixels in order to faithfully read out video information simultaneously and independently from the output terminals of each column in - times of access. It is valid.

Figure 2 shows a redrawn version of Figure 1. 9 is a collector region, 10 is a base region, and 1) is an emitter region.

Other rectangular regions existing in the collector region indicate regions with different impurity concentrations in the collector. other 1 to 8
are the same as those with the same number in FIG.

FIG. 3 shows a cross-sectional view of the semiconductor region along the dashed line A-A'' in FIG. 2. 10.1) is the base region and emitter region, as in FIG. 2.

12, 13, 15, and 17 are all included in the collector area.

Reference numeral 12 denotes a high concentration impurity diffusion region necessary for making ohmic contact with the collector region, and is formed at the same time as forming the emitter region 1). 14 is a substrate of a semiconductor of a different type from the collector region; 16 is a semiconductor region of the same type as the substrate; a region for separating each collector island; 17 is a collector of a low-temperature impurity region; Photoelectric conversion is performed in the vicinity of the region and the base region. Reference numeral 15 is a highly doped impurity diffusion region made of the same type of semiconductor as 17, and is provided to reduce the parasitic pnp transistor effect and to maintain the collector potential regardless of location. Reference numeral 13 is also a high concentration impurity diffusion region of the same type of semiconductor as 17, and is provided to reduce the parasitic pnp transistor effect and to improve conductivity from the ohmic contact SR region on the surface of the collector to 15.

However, this region acts as a barrier to carriers generated by photoelectric conversion between pixels that share the collector, and prevents the generated carriers from mixing between adjacent pixels. Therefore, in a sensor having a pixel structure that shares a collector, the region 13 is essential for performing high-resolution and faithful image reading.

As described above, with the configuration explained using FIGS. 1, 2, and 3, it is possible to realize an image sensor that reads out video information faithfully and simultaneously from a plurality of output terminals for each step of the scanning circuit.

FIG. 4 shows another embodiment in which the number of columns is three. 1, 2.3 are equivalent to the same numbers in FIG. 18.19.2o is the video output terminal from the pixels belonging to the first, second, and third columns, and it goes without saying that the output is received by the low input impedance circuit shown at 8 in Figure 1. do not have. Here, the light of different wavelength range for each column is 'I
By arranging a filter that causes zA, a color linear image sensor that reads document information and the like can be realized.

The filter may be striped. Naturally, this sensor mechanically scans the document relative to the document in a direction perpendicular to the columns, that is, in the sub-scanning direction, and reads the document information. Therefore, pixels having high sensitivity to light in a certain wavelength range are densely arranged in a straight line, so that there is no unread document. This is an image of the configuration in this example, considering that in a sensor in which pixels with three types of filters are arranged alternately in a row, two-thirds of the area of the document is covered without each pixel obtaining color information. It is clear that the sensor is effective and can suppress cracks and color misalignment when printing out document information. Furthermore, it goes without saying that video signals can be obtained at a rate three times the scanning frequency. In other words, according to this embodiment, it is possible to realize a color image sensor that can use a simple stripe filter and that can read color information of a document faithfully and quickly.

FIG. 5 shows another embodiment of a color image sensor.

1.2.3 are equivalent to those with the same numbers in FIG. 1
8.19.20.21 is the 1st row, 2nd row, 3rd row, 4th row
These are video output terminals from pixels belonging to a column, and each terminal is received by a low input impedance circuit shown as 8 in FIG. Although a color linear image sensor can be realized by arranging stripe filters that transmit light in different wavelength ranges in each column, only the fourth pixel column is blocked from light. After doing this, the switching noise is reduced by taking the difference between the video signal output of the pixels in the fourth column and the video signal outputs of the pixels in the first, second, and third columns. ! - It is possible to configure a completely different color image sensor.

FIG. 6 shows an embodiment of an image sensor using a bipolar transistor complementary to a phototransistor and a charging potential limiting diode as an access switch. 1.3
are the same as those indicated by the same numbers in FIG. 26.27
are video signal output terminals from pixel columns belonging to the (n−1)th column and the nth column. While the phototransistor is npn type, the transistor 22 used as an access switch is pn type.
It is p-type. 24 is a voltage source for charging the phototransistor through the access switch 22 during access. 25 is a terminal for taking the cathode potential of the lowest stage of the diode array 23, and may be grounded. 23
consists of three diodes connected in series, and if the potential of each video signal output terminal is set to ground potential, the charging potential to the phototransistor is limited to three times the forward drop potential of the diode. However, the number of directly connected diodes may be any number and is not limited to three.

However, the setting must be made so that the pnp transistor 22 does not become saturated, that is, the collector potential of the pnp transistor 22 does not exceed the Hess potential. This is because when access is completed and the base potential of the pnp transistor 220 becomes high, a false output appears at the read timing of the pixel in the next stage. By using such an access switch to sequentially read out each row according to the output of the scanning circuit, it is extremely easy to create an image sensor that reads out video information faithfully and simultaneously from multiple output terminals for each step of the scanning circuit. realizable.

FIG. 7 shows an embodiment using another access switch. ■, 3.26.27 are the same as those shown with the same numbers in FIG. 28 is an enhancement type MOS F E
The access switch may be an n-channel type or a p-channel type, or it may be a transmission gate switch configured in the form of a pair of both types. 2
Reference numeral 9 denotes a voltage source for charging the phototransistor through the access switch 28 during access.

By using such an access switch to sequentially read out each row according to the output of the scanning circuit, an image sensor that can read out video information faithfully and simultaneously from multiple output terminals for each step of the scanning circuit can be realized extremely easily. can. Furthermore, if a scanning circuit using the same <MO3I transistor is used as a scanning circuit, an image sensor satisfying the above performance can be easily realized simply by forming a phototransistor in a normal MO3 or CMOS process.

FIG. 8 shows an embodiment in which a decoder circuit formed of bipolar transistors is used as a scanning circuit. (For the decoder type scanning circuit, see Japanese Patent Application No. 58-200294). 3.22.23.24.26.27 are the same as those shown with the same numbers in FIG. 30, 31, and 32 each consist of a pair of complementary signals, and by the combination of these three pairs of signals, one of the rows of the pixel column consisting of eight rows in the figure is accessed.

However, if the terminal 33 is not set to H" at this time, this 8
None of the rows are selected. This 33 is a segment selection signal input terminal, and by connecting a large number of image sensors configured as shown in this figure in series, a long image sensor with an expanded number of rows can be obtained. In an image sensor consisting of a single chip having a plurality of segments having the configuration shown in this figure, a circuit for sequentially selecting terminals corresponding to 33 of each segment may be formed in the same chip. This decoder scanning circuit is capable of accessing 8 rows with a 3-bit input, but basically means a decoder-type scanning circuit that can access 2 to the nth power of rows with an n-bit input.

Such a decoder type scanning circuit is basically capable of random access as well as serial access like a shift register. Further, since no current flows through the transistors in the path of the accessed row, current consumption can be reduced. I)n+)) of the access switch of the selected row
The base of the run risk is pulled down and this pnp transistor is turned on to charge the pixels in the selected row and read out the video information. With this configuration, by sequentially reading out each row according to the output of the scanning circuit that can be randomly accessed, it is extremely easy to read out the video information of any row faithfully and simultaneously from multiple output terminals for each step of the scanning circuit. Sensors can be realized.

FIG. 9 shows an embodiment of an image sensor using a thyristor shift register as a scanning circuit.

(For thyristor scanning circuits, please refer to Japanese Patent Application No. 61-138.
567). 3.22.23.26.27 is the 8th
It is the same as that shown with the same number in the figure. 37 and 38 are terminals that apply a predetermined power supply voltage. 34 is a serial in terminal, and 35 and 36 are complementary clock input terminals. 39.40 is the output of the thyristor scanning circuit.
This is a complementary signal input terminal for converting a fubinote output to a full bit output. By sequentially turning on the 22 transistors, each row is sequentially accessed. By sequentially reading out each row using a circuit with such a configuration, it is possible to realize an image sensor that can read out video information faithfully and simultaneously from multiple output terminals for each step of the scanning circuit, using only a bipolar process. can.

FIG. 10 shows another embodiment of an image sensor using a thyristor shift register as a scanning circuit.

3.22.23.26.27.34.35.36.37
．． 38 is the same as that shown with the same number in FIG. 41
is also a terminal that applies a predetermined voltage. This type of thyristor scanning circuit output is a full bit output. By sequentially turning on the 22 transistors, each row is sequentially accessed. By sequentially reading out each row using a circuit with this configuration, it is possible to create an image sensor that can read out image information faithfully and simultaneously from multiple output terminals for each step of the scanning circuit, using only bipolar processes. realizable.

As described above, in an image sensor consisting of a light receiving section in which pixels made of phototransistors are arranged in a matrix, a scanning circuit that accesses each row of the matrix sequentially, and an access switch, the emitters of pixels belonging to the same column are common. The collectors of pixels that are connected to form an output line and that belong to the same row share a semiconductor isolation region of a different type with the substrate, and by sequentially accessing the common collector, By passing through a low input impedance circuit that suppresses fluctuations, it is possible to easily realize an image sensor that can read out video signals from pixels in the same row to the above output lines of each column without mixing them with each other at the same time. In addition, in the diagrams used for the above explanation, in addition to changing the polarity of the power supply, etc., the phototransistor that is the pixel is inserted, and the Ibora transistor is changed to a pnp type if it is an npn type, and to an npn type if it is a pnp type. You may change its type.

It goes without saying that the video signal output terminals 18, 19, 20, 21, 26, and 27 in each figure from Fig. 4 to Fig. 10 are received by the low input impedance circuit 8 shown in Fig. 1 and Fig. 2. Nor.

Effects of the Invention As is clear from the above explanation, the present invention provides an image sensor that can simultaneously read out video signals from pixels in the same row to the outputs of each column without losing the independence of the amount of potential change. can be easily realized, the function as a video information input device can be dramatically improved, and the industrial effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the configuration of an image sensor according to the present invention;
Fig. 2 is a block diagram of the configuration of an image sensor showing a plan view of the pixel structure, Fig. 3 is a cross-sectional view of the semiconductor region of the pixel, Fig. 4 is a block diagram of the configuration of an image sensor with a pixel array consisting of three columns, and Fig. 5 is a block diagram of an image sensor with a four-column pixel array, Figure 6 is a diagram of an image sensor that uses a bipolar transistor and a charging voltage limiting diode as an access switch, and Figure 7 is a block diagram of an image sensor that uses a MOS FET as an access switch. Figure 8 is a configuration diagram of an image sensor using a decoder circuit as a scanning circuit, Figure 9 is a configuration diagram of an image sensor using a thyristor shift register as a scanning circuit, and Figure 10 is a configuration diagram of an image sensor using a thyristor shift register as a scanning circuit. FIG. 3 is a configuration diagram of another image sensor using a register as a scanning circuit. 1...Scanning circuit, 2...Access switch row, 3...Phototransistor, 4, 5,
6,7,18゜19,20.21.26.27...
...Video signal output terminal, 8...Low input impedance circuit, 9...Collector area, 10...
...Base region, 1) ...Emitter region, 2
2...Transistor serving as an access switch,
23... Charging voltage limiting diode string, 28...
...MOS FET circuit that serves as an access switch. Name of agent Patent attorney Shigetaka Awano 1 person = - 4,56,7- θ Run 1 Circuit act! Susui, 7,000 rows of phototransistor M coins, 1 child low input input, 1 9 sozuro road? --- Koshi 7 Yu Kazukawa (IQ
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9 Xiu Ward 1 Map &! 3 Ward Map Funeral Map Diagram 10

Claims (8)

[Claims] (1) In an image sensor consisting of a light receiving section in which pixels are arranged in a matrix, a scanning circuit that sequentially accesses each row of the matrix, and an access switch, each of the pixels consists of a phototransistor, and the pixels belonging to the same column are the emitters are wired together to form an output line,
In addition, the collectors of pixels belonging to the same row share a semiconductor isolation region of a different type with the substrate, and by sequentially accessing the common collector, low input impedance is achieved by suppressing fluctuations in the potential of the output line of each column. An image sensor characterized in that video signals from pixels in the same row are simultaneously read out to the output lines of each column through a circuit without being mixed with each other. (2) The image sensor according to claim 1, wherein the access switch comprises a bipolar transistor complementary to the phytotransistor and a charging voltage limiting diode. (3) Claim (1) characterized in that the number of columns is three, and each column is configured to read light in a different wavelength range.
The image sensor described. (4) The number of columns is 4, one of which is shielded from light and used for differential output with the output signals from the other three columns, and the remaining three columns have different wavelength ranges for each column. The image sensor according to claim 1, wherein the image sensor reads the light of the image sensor. (5) The image sensor according to claim (1), wherein the access switch is composed of a MOS transistor. (6) The image sensor according to claim (1), wherein the scanning circuit that accesses each row is comprised of a decoder circuit formed of bipolar transistors. (7) The image sensor according to claim (1), wherein the access-through scanning circuit for each row is comprised of a thyristor scanning circuit. (8) The image sensor according to claim (1), wherein the scanning circuit that accesses each row is comprised of a MOS transistor.