JPH056386B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical reading device that optically reads information with high precision.

(Constitution of Conventional Example and its Problems) Examples of conventional optical reading devices include a silicon vidicon, a MOS target vidicon, and the like. Since the access function for sequential readout is performed by deflecting the electron beam, these have the advantage of being easy to read and can achieve high resolution. However, since they are not all solid-state, they have drawbacks such as miniaturization and low power consumption. be.

On the other hand, as an all-solid-state optical reader, CCD
Examples include image sensors and MOS image sensors. It consists of a photodiode array for light detection and a scanning circuit for sequential reading. CCD
The scanning circuit of the image sensor is CCD and MOS
The scanning circuit of the image sensor is a MOS shift register. All of these are based on MOS integrated circuit technology, and operation occurs at the Si-SiO ₂ interface. Since it is a light-receiving element, it must be packaged with a transparent material, and an element with a large light-receiving area also requires a large package size. It is difficult to completely encapsulate MOS devices that are sensitive to surface conditions at low cost using the limited materials mentioned above. In particular, it is difficult to seal a long and large reading element in a contact type reading system.

(Objective of the Invention) The present invention is characterized by the fact that the above-mentioned conventional CCD image sensor and MOS image sensor are manufactured using a MOS-IC process, so they need to be made of materials that are sensitive to surface conditions, are susceptible to static electricity, and have high performance. Eliminating drawbacks such as the difficulty of making phototransistors,
Providing an optical reading device (image sensor) that can form a sensor part and a scanning part on the same chip with a simple circuit by using a bipolar IC process, and can read with high reliability, high speed, and high accuracy. The purpose is to

(Structure of the Invention) The optical reading device of the present invention includes a pixel consisting of a phototransistor (photodiode array) for photodetection, and each stage detects the conduction state of the thyristor and reads the gate electrode of the thyristor of the next stage. It consists of a shift register consisting of a coupling transistor that transmits the conduction state, a driving transistor attached to each stage of thyristors that turns on and off depending on the conduction state of the thyristor, and a light-shielding film that shields the entire thyristor array from light. Features. Because of the above configuration, this image sensor can be manufactured using bipolar integrated circuit technology. Thyristor is 1
Each stage has a signal holding function, and each stage can constitute a shift register, so the number of elements in the scanning section can be extremely reduced.

(Description of Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of an image sensor in one embodiment of the present invention. In Figure 1, 1 ₁ , 1
₂ , 1 ₃ and 1 ₄ are phototransistors, which are provided in a desired number at regular intervals on the Si chip. 2 ₁ ,
2 ₂ , 2 ₃ , and 2 ₄ are thyristors, and together with the coupling transistors 3 ₁ , 3 ₂ , 3 ₃ , and 3 ₄ between the stages, they function as a shift register. 4 ₁ , 4 ₂ , 4 ₃ , and 4 ₄ are coupling transistors for detecting the conduction state of the thyristors and setting the phototransistors connected to their respective collectors to the reading state. 5 is an input coupling transistor that transmits the input of the start signal to the gate of the first stage thyristor. A thyristor 6 is connected at the last stage and, together with the transistor 7, functions to facilitate continuous connection between the image sensor chips. 8 ₁ , 8 ₂ , 8 ₃ , 8 ₄ , and 8 ₅ are load resistors connected to the anodes of the thyristors. Resistance 9 ₁ ,
9 ₂ , 9 ₃ , 9 ₄ , 9 ₅ are resistors 10 ₁ , 10 ₂ , 10 ₃ ,
Together with 10 ₄ and 10 ₅ , it functions to adjust the trigger sensitivity of the thyristor. The cathodes of the thyristors in the same stage, the emitters of the interstage coupling transistors, and the emitters of the coupling transistors with the phototransistor are connected in common, and the common connection points of the odd-numbered stages and the common connection points of the even-numbered stages are connected to the shift clock φ and Connecting. The collectors of each phototransistor are commonly connected to form an output terminal 11. 12 is an output load resistance. The operation of the image sensor of this embodiment configured as described above will be described below.

The thyristor is of N-gate type and is triggered by applying a negative voltage to the gate electrode compared to the anode. First, when an H level pulse is input to the SI terminal, the collector current of transistor 5 flows, and the gate electrode of thyristor ₂₁ goes to L level (active).In this state, when the cathode of the thyristor goes to L level, this thyristor becomes conductive, and the conductive state is maintained even after the gate voltage becomes H level (inactive).
In this state, the transistor 4 ₁ is connected to the phototransistor by a common base-emitter connection.
also becomes conductive, allowing current to flow through the phototransistor 1 ₁ and outputting the photoelectric conversion signal to the output terminal 11 . Similarly, the coupling transistor 3 ₁ with the next stage
The second stage thyristor is in a conductive state and the second stage thyristor is at the L level, but since the cathode (connected to) of the second stage thyristor ₂₂ is at the H level, the thyristor ₂₂ maintains the non-conducting state. Next clock state (φ=H,
When φ=L), the gate of thyristor 2 ₂ is at L level, so when the cathode voltage of thyristor 2 ₂ transitions to L level (=L), the second stage thyristor becomes conductive. As a result, the photoelectric conversion signal of the phototransistor 1 ₂ is read as described above. Also, in this clock state, the state of the first stage thyristor changes from conductive to non-conductive. In this way, the conduction states of the thyristors are sequentially shifted from left to right. Along with this, the photoelectric conversion signals of the phototransistors are sequentially output from the left phototransistor to the right output line in FIG. In the circuit shown in Figure 1, the signal is V _cc
(for example, 5V) is the zero point, and its polarity is negative. If it is difficult to use a signal whose zero point is _Vcc , the image sensor power source may be a negative voltage source. Although the polarity is negative, a signal whose zero point is 0 voltage can be obtained.

FIG. 2 is a timing diagram of various drive pulses and read output signals of the image sensor.
The period of the start pulse is the integration time of the phototransistor in charge accumulation mode.

This image sensor can be easily manufactured using a standard bipolar IC process (epitaxial planar method). A single thyristor can constitute one stage of a shift register, and furthermore, a coupling transistor between stages can be formed in the same isolation region as the thyristor. Therefore, the scanning circuit for reading can be formed on an extremely small area, and the light receiving area of the phototransistor can be increased to the limit determined by the resolution. In addition, since the collectors of all phototransistors are connected in common, they can be formed in the same isolation region, making bipolar IC
The disadvantages associated with element isolation can be minimized.

FIG. 3 is a circuit diagram of an image sensor according to a second embodiment of the present invention. In Figure 3, 13
₁ , ₁₃₂ , ₁₃₃ , and ₁₃₄ are phototransistors, which are provided in a desired number at regular intervals on the Si chip. 14 ₁ , 14 ₂ , 14 ₃ , 14 ₄ are thyristors, and coupling transistors 15 ₁ , 15 between each stage
It functions as a shift register together with ₂ , 15 ₃ and 15 ₄ . 16 load resistors on each anode of each thyristor
₁ , 16 ₂ , 16 ₃ , 16 ₄ and switch PNP transistors 17 ₁ , 17 ₂ , 17 ₃ , 17 ₄ are connected. This switching transistor has its collector connected to the phototransistor and serves to place the phototransistor in a reading or integrating state depending on the conduction or non-conduction state of the thyristor. 1
8 inputs the start signal to the first stage thyristor 14
1 is an input coupling transistor that transmits to the gate of ₁ . 19 is a thyristor connected to the final stage,
Together with transistor 20, it functions to facilitate continuous connection between image sensor chips. Resistor 21 ₁ ,
21 ₂ , 21 ₃ , 21 ₄ , 21 ₅ are resistors 22 ₁ , 22 ₂ ,
Together with 22 ₃ , 22 ₄ , and 22 ₅ , it functions to adjust the trigger sensitivity of the thyristor. The cathodes of the thyristors in the same stage and the emitters of the interstage coupling transistors are connected in common, and the common connection points of the odd-numbered stages and the common connection points of the even-numbered stages are connected to shift clocks φ and φ, respectively. The emitters of each phototransistor are commonly connected to form an output terminal 23. 24 is an output load resistance.

Since the operation of this embodiment is basically the same as that of the first embodiment, a detailed explanation of the operation will be omitted. A newly installed PNP transistor detects whether the thyristor is conductive or non-conductive, and when the thyristor is conductive, the phototransistor is placed in the reading state, and when it is non-conductive, the phototransistor is placed in the integrating state. In this way, by providing a buffer switch using a PNP transistor, a large amplitude output signal can be obtained. Another feature of this embodiment is that a signal based on the ground level can be obtained.

FIG. 4 is a schematic diagram of the arrangement of elements on the image sensor chip. 25 is a phototransistor array, 26 is an array having thyristors and coupling transistors as units, and 27 is a pad for connecting between chips. Moreover, 28 is a film for light shielding, and is for preventing malfunction due to light irradiation to the thyristor.

In the above embodiment, a phototransistor was used as a sensor for detecting light, but any element that receives light and generates a current can be used for this purpose. For example, a photodiode, a light conductive film, etc. can also be used.

(Effects of the Invention) As is clear from the above description, the present invention provides a sensor array consisting of a phototransistor array (or photodiode) for photodetection, a thyristor array for sequentially accessing the sensor array, and a thyristor array for sequentially accessing the sensor array. It consists of a coupling transistor array that provides a shift function, a coupling transistor array that transmits the conduction state of each thyristor array to the phototransistor array (or photodiode) for photodetection, and the like.

By using a thyristor array, the present invention can significantly reduce the number of elements required for the scanning section, making it possible to manufacture a high-density, multi-bit image sensor despite the use of a bipolar process.

In addition, since it is a bipolar IC process, it is more reliable than a MOS or CCD image sensor that uses a surface region, and can easily form a high-precision phototransistor.

In addition, bipolar ICs generally consume more power than MOS-ICs, but in the scanning function required for image sensors, only one bit of all thyristors is in a conductive state during reading. Since only the thyristor consumes power and the other thyristors that are in the OFF state do not consume power, it is characterized by extremely low power consumption.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an image sensor according to an embodiment of the present invention, FIG. 2 is a timing diagram of various drive pulses and read output signals, and FIG. 3 is a circuit diagram of an image sensor according to a second embodiment of the present invention. FIG. 4 is a schematic diagram of the arrangement of elements on an image sensor chip. 1 ₁ , 1 ₂ , 1 ₃ , 1 ₄ , 13 ₁ , 13 ₂ , 13 ₃ , 1
3 ₄ ... Phototransistor, 2 ₁ , 2 ₂ , 2 ₃ , 2 ₄ ,
14 ₁ , 14 ₂ , 14 ₃ , 14 ₄ ...thyristor, 3 ₁ ,
3 ₂ , 3 ₃ , 3 ₄ , 4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ , 15 ₁ , 1
5 ₂ , 15 ₃ , 15 ₄ ...coupling transistor, 5, 1
8... Input coupling transistor, 6, 19... Final stage thyristor, 7, 20... Final stage coupling transistor, 8 ₁ , 8 2 , 8 ₃ , 8 ₄ , 8 ₅ , _{16 1} , 16 ₂ , 1
6 ₃ , 16 ₄ ...Load resistance, 9 ₁ , 9 ₂ , 9 ₃ , 9 ₄ , 9
₅ , 10 ₁ , 10 ₂ , 10 ₃ , 10 ₄ , 10 ₅ , 21 ₁ ,
21 ₂ , 21 ₃ , 21 ₄ , 21 ₅ , 22 ₁ , 22 ₂ , 2
2 ₃ , 22 ₄ , 22 ₅ ...gate resistance, 11, 23...
Video signal output terminal, 12, 24...output load resistance,
17 ₁ , 17 ₂ , 17 ₃ , 17 ₄ ... PNP transistor for switch, 25 ... Photo transistor array,
26...Array of thyristor and coupled transistor,
27... Pad for connection between chips, 28... Light shielding film.

Claims (1)

[Claims] 1. A pixel consisting of a phototransistor or a photodiode array for photodetection, and a coupling transistor in which each stage detects the conduction state between thyristors and transmits the conduction state to the gate electrode of the thyristor in the next stage. It consists of a shift register, a driving transistor attached to each stage of thyristor that turns on and off depending on the conduction state of the thyristor, and a light-shielding film to shield the entire thyristor from light, according to the scanning signal generated by the shift register. By sequentially turning on the driving transistors and causing the driving transistors to flow a charging current to one electrode of the phototransistor or photodiode, an image signal is output from the line commonly connected to the other side of the phototransistors. Features an optical reading device. 2 Connect the base electrode and emitter electrode to the P-type gate electrode and cathode electrode of each thyristor, respectively, and connect the collector electrode to the N-type gate electrode and cathode electrode of the next stage thyristor.
A coupling NPN transistor connected to a shaped gate electrode, a base electrode and an emitter electrode connected to the base electrode and an emitter electrode of the coupling NPN transistor, respectively, and a collector electrode connected to the emitter of a phototransistor or the cathode of a photodiode. The optical reading device according to claim 1, characterized in that the optical reading device is made of an NPN transistor. 3 A coupling NPN transistor whose base electrode and emitter electrode are connected to the P-type gate electrode and cathode electrode of each thyristor, respectively, and whose collector electrode is connected to the N-type gate electrode of the next stage thyristor;
A load resistor was connected between the anode electrode of the thyristor and the positive power supply, the emitter electrode was connected to the positive electrode, the base electrode was connected to the anode electrode, and the collector electrode was connected to the collector electrode of the phototransistor or the anode electrode of the photodiode. Drive PNP
The optical reading device according to claim 1, characterized in that it is made of a transistor.