JPH0222591B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application With the advancement of automatic control equipment for information processing equipment such as computers, the importance of sensors as input devices has increased. The present invention relates to a line-shaped image sensor that makes full use of IC technology to detect information in color at high speed and high resolution.

Conventional configurations and their problems Conventional solid-state color line image sensors include CCD image sensors, MOS image sensors, amorphous silicon image sensors,
There is a CdS image sensor. CCD and MOS image sensors have a photodiode as a detection part and a scanning circuit formed on a silicon crystal substrate, and in order to distinguish colors, a three-color filter film is placed on the light-receiving surface of the photodiode in a certain pattern. attached in a pattern. In order to identify colors, it is necessary to detect three types of color signals (R, G, B) for one dot. In a CCD image sensor, for example, when reading each color at a resolution of 8 dots/mm, the sensors are arranged at a density of 24 dots/mm and output as a serial signal from one output terminal. In this case, the reading speed is 1/3 compared to monochrome reading. CCDs originally use a charge carrier, which is in a thermally non-equilibrium state, as a signal medium, so they have the disadvantage that they cannot be used at high temperatures.
The scanning speed of a MOS image sensor is limited by the clock frequency of the MOS shift register.
and has the disadvantage of large signal noise.

An amorphous silicon image sensor uses an amorphous silicon photodiode and an amorphous silicon thin film transistor or
It consists of a scanning circuit consisting of an IC, and three-color filters are attached in a regular pattern on the light-receiving surface of a photodiode for color identification. There are many issues that need to be resolved before it can be put into practical use, such as reading speed, yield, reliability, and connection to the drive circuit. Additionally, CdS image sensors have the disadvantage of slow response speed to light.

Compared to monochrome reading, color reading requires detection of three types of signals, and therefore requires three times the reading time. Considering the need for high-speed reading and the coexistence of monochrome and color reading, there is a need to achieve the same reading speed in color as in monochrome.

OBJECTS OF THE INVENTION An object of the present invention is to provide a color image sensor that enables high-speed reading and coexistence of monochrome reading and color reading by outputting color signals in parallel.

Configuration of the Invention The color image sensor of the present invention includes an array consisting of three rows of photodetecting elements each having a different detection wavelength and each of which is connected to three output lines so as to detect and output three types of color signals; a switching transistor group consisting of switching transistors connected so as to simultaneously access photodetecting elements for different color signals; and a decoding circuit for turning on and off each of the switching transistors; Parallel signals are output for each color signal from the output line of the book.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a circuit which receives an external input selection signal at an input selection signal terminal 1 and converts it into a multi-threshold logic signal with a complementary output 2. In FIG. The current from the constant current circuit 3 is applied to the transistors 4a or 4b, 5a or 5b, according to the comparison of the bit selection input signal with the logic reference voltage _Vth by the transistor pairs 4, 5, and 6 constituting the current switch circuit. 6a or 6b, and complementary voltages with different DC levels are generated by the respective current and resistor pairs 7, 8, and 9. For example, when an "H" level signal is input to the input terminal 1a of the bit selection input signal terminal 1, A of the complementary output 2 becomes "H" and A becomes "L". This logic amplitude is determined by the value of the resistor pair 7 and the current value of the constant current circuit 3. Since transistor pairs 4, 5, and 6 operate in a non-saturated state, high-speed operation is possible. In addition, 1
0 to 12 are transistors for setting the DC level, and 13
is a resistor string for voltage division. Although FIG. 1 shows the case of 3 bits, this can be expanded to a case of even larger number of bits by repeating the same procedure.

In FIG. 2, the aforementioned multi-threshold logic signal is received at the input terminal 14, a current from the current source 16 controlled by the block selection input signal 15 is passed through a desired branch path, and this current is sensed. 3 through 3 output switching transistors 28a, 28b to 31a, 31b that perform switching operation.
seed phototransistor arrays 32a-36b,
This circuit accesses 37a to 40b and 41a to 44b.

The transistor pairs 17, 18, . These transistor pairs also operate in a non-saturated mode, resulting in high speed operation. resistance 24
a, 24b, . . . 27a, 27b are load resistances necessary to detect which transistor is in a energized state among the transistor pairs 20 to 23. The PNP transistors 28a, 28b, .about.31a, 31b perform a switching operation of turning on or off depending on the presence or absence of the collector current of the transistor pairs 20, 21, .about.23. When using a lateral PNP transistor as a switching transistor, the method of connecting the base electrode to one end of the resistors 24a, 24b to 27a, 27b, the emitter electrode to the positive power supply, and the collector electrode to the collector electrode of the phototransistor, and the method of connecting the emitter and collector There is a method in which the collector electrode is connected to the positive power supply and the emitter electrode is connected to the collector electrode of the phototransistor by connecting them in reverse, but the reverse connection has less leakage to the output of the selection digital signal. The structure of a lateral PNP transistor is shown in FIG. 3, in which the electrodes are arranged in the order of emitter 48, collector 49, and base electrode 50 from the inside to the outside. Leakage of digital signal to output terminal
It occurs in the path from the base of the PNP transistor to the collector of the phototransistor. When the collector of a phototransistor is driven by the collector of a PNP transistor, the base electrode and collector of the PNP transistor are adjacent to each other, so the capacitive coupling between them is large, and the leakage of digital signals to the output terminal is large. However, when the collector of a phototransistor is driven by the emitter of a PNP transistor, the collector electrode (fixed to the positive power supply voltage) is interposed between the base electrode and the emitter electrode, so there is less leakage of digital signals to the output.

In FIG. 2, three lines of R, G, and B phototransistor arrays 32a to 36b, 37a to
In order to drive 40b, 41a to 44b, each switching PNP transistor has three drive terminals in connection with the phototransistor. The emitters of the three lines of phototransistors are connected in common and serve as color signal output terminals. 45, 46, and 47 are load resistances for each color signal. Next, the specific operation of the image sensor of the present invention will be explained. Block selection input terminal is “H”,
When the bit selection input signals A, B, and C are each at "L", the current from the current source flows only through the resistor 24a and does not flow through the other resistors. the result,
Only the base potential of the PNP transistor 28a decreases, and only this transistor becomes "ON".
From the three outputs, a phototransistor 32a,
A current of charge flows through the phototransistors 37a and 41a, and the phototransistors become in a reading state, and the reading signals are output from each output line in the form of extraordinary outputs for each color signal. No current flows through the other phototransistors, and they are in a floating state, resulting in an integration period (non-access period). By applying respective input signals to the bit selection input terminal and the block selection input terminal, it is possible to sequentially scan at high speed.

If the logic amplitude of the input terminal 14 is 0.5V, it is sufficient to drive the current switching circuit, and the logic amplitude is small.
The access time delay due to parasitic capacitance can be minimized, and the current switching transistor operates in a non-saturated state.
High-speed reading becomes possible. Furthermore, since each color signal is output as a parallel signal, it can be read at the same speed as monochrome reading.

FIG. 4 is a block diagram of an image sensor driving circuit according to the present invention. After counting up or down to the number of bits of the image sensor using a flip-flop, oscillator, and counter, and converting the desired low-order bits of the counter (corresponding to the number of bits of the bit selection input signal) to Gray code,
It is applied to the bit selection input signal terminal 1 of the image sensor. This is applied as a shift clock to the shift register at a desired clock interval (corresponding to the number of bits in one block), and the output signal of the shift register is applied to the block selection input signal terminal 15 of the image sensor. This drive circuit provides sequential read signals.

FIG. 5 schematically shows each functional section arranged on the image sensor chip according to the present invention. The light-receiving windows of the three-column phototransistor array 51 are provided with R, R and R, respectively.
G and B color filters are attached. 52 to 54 are output terminals for each color signal, 55 to 58 are block selection signal input terminals, 59 to 63 are bit selection signal input terminals, and 64 and 65 are a power supply input terminal and a ground terminal, respectively.

In the explanation of the circuit and its operation, in order to make the explanation easier to understand, we have explained the case where the bit selection input signal is 3 bits and the block selection input signal is 1 bit, and 8 bits are read for each color. Due to the increase in the number of bits and the number of bits of the block selection input signal, the number of
It is possible to increase the number of read bits to several thousand bits. Furthermore, although the above explanation has been made regarding the phototransistor, by connecting the cathode of the photodiode to the output terminal of the switching transistor and the anode to the color signal output terminal instead of the phototransistor, the photodiode can also be used as a sensing element. It can be used similarly. As shown in FIG. 5, bipolar integrated circuit technology allows the necessary elements to be integrated on a silicon chip, thereby achieving high speed, high reliability, and low cost.

Effects of the Invention As is clear from the above description, the color image sensor of the present invention has high speed and high resolution.

Furthermore, since the digital circuit in the scanning section is constructed using ECL (emitter coupling logic) and the color signals are output as parallel signals, high-speed reading is possible. Furthermore, all functions can be formed on a silicon chip using conventional bipolar integrated circuit technology, resulting in high resolution and high reliability. Therefore, the present invention can be used as an input device for information processing equipment.
Furthermore, it is useful as a sensor for automatic control equipment,
Its industrial effects are significant.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the multi-threshold signal generation circuit in the color image sensor of the present invention, FIG. 2 is a diagram showing the configuration of the current switching circuit in the same sensor, and FIG. 3 is a diagram showing the horizontal configuration of the same sensor.
A plan view of the PNP transistor, FIG. 4 is a block diagram of the entire sensor including the drive circuit, and FIG. 5 is a schematic diagram of the chip of the image sensor. 1... Selection signal input terminal, 2... Multi-threshold signal output terminal, 3... Constant current circuit, 4,
5, 6... Current switch transistor pair, 7,
8, 9... Resistor pair, 10, 11, 12... Transistor pair for DC level generation, 13... Resistor string for voltage division, 14... Input terminal, 15... Block signal input terminal, 16... Control current Source, 17, 18~
23... Current switching transistor pair, 24a,
24b to 27a, 27b...Load resistance, 28a,
28b to 31a, 31b...Switch transistor, 32a, 32b to 44a, 44b...Photo transistor, 45, 46, 47...Load resistor, 48...Emitter electrode, 49...Collector electrode, 50...Base electrode , 51... Photo transistor array, 52, 53, 54... Video output terminal, 55-58... Block selection signal input terminal,
59-63...Bit selection signal input terminal, 64...
...Ground terminal, 65...Positive power supply terminal.

Claims (1)

[Scope of Claims] 1. An array consisting of three rows of photodetecting elements each having a different detection wavelength and each connected to three output lines so as to detect and output three types of color signals;
a switching transistor group consisting of switching transistors connected so as to simultaneously access photodetecting elements for different color signals; and a decoding circuit for turning on and off each of the switching transistors; A color image sensor characterized by outputting parallel signals for each color signal from a book output line. 2. The color image sensor according to claim 1, wherein the decoding circuit uses a circuit that decodes a binary signal encoded with a Gray code. 3 The decoding circuit consists of a circuit that converts a bit selection input signal encoded in Gray code into a multithreshold logic signal of complementary voltages with different DC levels, and a current source activated by the block selection input signal. and a circuit that receives the multi-threshold logic signal and causes the current to flow through the branch path selected by the selection input signal using a current switching circuit in which the current from the current source is connected in cascade. Characteristic claim 1
Color image sensor described in section. 4. The color image sensor according to claim 1, wherein the switching transistor is a horizontal PNP transistor. 5. The color image sensor according to claim 1, wherein the photodetecting element is constructed using a phototransistor. 6. The color image sensor according to claim 1, wherein the photodetecting element is constructed using a photodiode.