JPH04335758A - Picture reader - Google Patents

Abstract

PURPOSE:To obtain a picture signal in time series from one common signal line when picture readers are arranged on a same board. CONSTITUTION:An output control circuit 7 outputs a control signal by using a scanning input signal, a scanning output signal and a clock pulse to control an impedance conversion circuit 8 and a switching element 9. Thus, plural picture readers are arranged on a same board, a picture signal without distortion in time series from one common signal line is obtained and current consumption is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device that converts optical image information into electrical signals, and more particularly to a multi-chip line sensor in which photoelectric conversion elements are integrated and arranged in a straight line.

0002

2. Description of the Related Art Conventionally, an image reading apparatus as shown in FIG. 2 has been known. The signal from the photoelectric conversion element 1n is output to the common signal line via the switching element 2n. The plurality of switching elements 2n are sequentially scanned by the scanning circuit 3, and the output signals are impedance-converted by the impedance conversion circuit 8 and output from the image signal output terminal 33 in time series. As shown in FIG. 3, there is an image reading device that achieves this by using a CCD in a scanning circuit to reduce the size of the image reading device.

0003

[Problems to be Solved by the Invention] However, in the conventional line sensor, as shown in FIG. 3, even if the image reading device 47 is small, it uses a lens 46 to capture the reflected light from the irradiated document 45 onto the line sensor. In order to form an image and convert it into an image signal, a distance is required from the original to the line sensor, and electronic devices such as facsimiles cannot be miniaturized. Note that 48 is a substrate, and 49 is a common image signal output terminal. Also,
As shown in FIG. 4, a method is also used to miniaturize electronic equipment by using a SELFOC lens as a 1:1 imaging optical system and arranging image reading devices with a wide original width. However, in this method, as shown in FIG. 4, when a plurality of image reading devices 47 are arranged on a substrate 48 and image signal output terminals 49 are connected in common, image signals are obtained in a time-series manner. As shown in FIG. 5, all the impedance conversion circuits included in each chip are output to the same terminal, which has the disadvantage that the obtained image signal is distorted. Also, an image reading device 47 is mounted on the board 48.
It is also conceivable to provide image signal output terminals for each.
External signal processing becomes complicated. Note that 39 is a select signal input terminal, and 40 is an image signal input terminal. SUMMARY OF THE INVENTION In order to solve these conventional drawbacks, the present invention aims to make it possible to obtain undistorted image signals in time series even when a plurality of image reading devices are arranged.

0004

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an output control circuit in an image reading device that operates by inputting a scanning input signal, a scanning output signal, and a clock pulse. The impedance conversion circuit and the switching element are controlled by the control signal outputted from the output control circuit, so that even if a plurality of image reading devices are arranged, distortion-free image signals can be obtained in time series.

[0005]

[Operation] In the image reading device configured as above,
Even if multiple units are arranged on the same board and the image signal output terminals are connected in common, the device that outputs the image signal is limited by the output control circuit, so it is difficult to output an image signal without distortion from one image output terminal. Obtainable. Further, by controlling the impedance conversion circuit using the output control signal, low current consumption can also be achieved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. In FIG. 1, a block diagram of an image reading device using the present invention, a signal from a photoelectric conversion element 1n is connected to a common signal line 34 via a switching element 2n. The plurality of switching elements 2n are sequentially scanned by the scanning circuit 3. Scanning circuit 3 uses clock pulse CK
is input, and the scanning input signal SI is input, thereby generating a scanning pulse so as to sequentially turn on the plurality of switching elements 21 . . . 2n. After driving the final stage switching element 2n, the scanning output signal forming circuit 5
A scanning output signal SO is outputted from the scanning output signal SO. When a plurality of multi-chip line sensors are arranged, this scanning output signal SO becomes the scanning input signal SI of the next line sensor. The output control circuit 7 outputs the select signal SEL in response to the signal SI, the signal SO, and the clock pulse CK, and drives the impedance conversion circuit 8 that converts the impedance of the signal on the common signal line and the switching element 9 that reads the impedance-converted signal to the outside. . A timing chart of this image reading device is shown in FIG. Scanning circuit 3
operates at the falling edge of the clock pulse CK, and the i-th switching element 2i (i=1 to n) is driven by the low level of the i-th signal CK after the signal SI is input to the scanning circuit, and The image signal of the photoelectric conversion element 1i is read out to the outside.

FIG. 7 shows an embodiment of the output control circuit 7. In FIG. 7, a NOR circuit is used, but a NAND circuit may also be used. Also, without inputting the CK signal,
It is also possible to configure an output control circuit. FIG. 8 shows an embodiment of the impedance conversion circuit 8. When the select signal SEL is at a low level, the transistor 41 operates, and the signal input to the input terminal 40 undergoes impedance conversion and is output from the output terminal 42. Select signal S
When EL is at a high level, the transistor 41 does not operate, the output terminal 42 is in a high impedance state, and the output terminal is insulated from the input terminal 40. Further, since the transistor 41 does not operate, no current is consumed.

The switching element 9 shown in FIG. 9 is also driven by the select signal SEL. Select signal is Lo
At W level, it is in a conductive state, and at High level, it is non-conductive. These operations cause the switching element 9 to
There is no problem even if it is a MOS transistor. In this way, the impedance conversion circuit 8 and the switching element 9
operates only when the select signal SEL shown in FIG. 6 is High, so even if a plurality of image reading devices of the present invention are arranged, only one device outputs an image signal. In addition, the impedance conversion circuit is
Since no current is consumed, current consumption is low. Although a configuration that does not use an impedance conversion circuit is also possible, the present invention is an effective means in that case as well.

In FIG. 1, the switching elements are NMOS for convenience.
Although I used a transistor, a CMOS configuration may also be used. Further, for convenience, the scanning circuit is operated at the falling edge of CK, but it may be operated at the rising edge of CK, and in that case, other circuits can be changed accordingly.

0010

[Effects of the Invention] The present invention provides an output control circuit using a scanning input signal, a scanning output signal, and a clock pulse.
By controlling the image signal output period, even if multiple image reading devices are arranged on the same board, the image signal output terminal can be shared, which facilitates signal processing and allows images to be driven with low current consumption. This has the effect of providing a reading device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an image reading device of the present invention.

FIG. 2 is a block diagram of a conventional image reading device.

FIG. 3 is a perspective view of an embodiment of a document reading system using a conventional image reading device.

FIG. 4 is a perspective view of another embodiment of a conventional document reading system.

FIG. 5 is a circuit diagram showing circuits connected to the common signal line of the system of FIG. 4;

FIG. 6 is a timing chart of the image reading device of the present invention.

FIG. 7 is a circuit diagram showing one embodiment of the output control circuit 7. FIG.

8 is a circuit diagram showing one embodiment of the impedance conversion circuit 8. FIG.

9 is a circuit diagram showing one embodiment of the switching element 9. FIG.

[Explanation of symbols]

11 - 1n photoelectric conversion element 21 - 2n switching element A 3 scanning circuit 4 scanning input signal forming circuit 5
Scanning output signal formation circuit 6 Scanning clock pulse formation circuit 7 Output control circuit 8 Impedance conversion circuit 9
Switching element B 30 Scanning input signal input terminal 31
Scanning clock pulse input terminal 32 Scanning output signal output terminal 33 Image signal output terminal 34 Common signal line 35 Control output signal input terminal 36
Control clock pulse input terminal 37 Control input signal input terminal 38 Select signal output terminal 39 Select signal input terminal 40
Image signal input terminal 41 Transistor 42 Impedance conversion circuit output terminal 43
Switching element input terminal 44
Switching element output terminal 45 Original 46 Lens 47 Conventional image reading device 48
Board 49 Common image signal output terminal 50
selfoc lens

Claims (1)

[Claims] 1. A scanning circuit that sequentially drives the switching elements, a plurality of photoelectric conversion elements integrated and arranged in a straight line, switching elements connected to each of the photoelectric conversion elements to read out signals from the photoelectric conversion elements, and a scanning circuit that sequentially drives the switching elements. and a scanning input signal forming circuit for driving the scanning circuit, a scanning output signal forming circuit, and a scanning clock signal forming circuit for the scanning input signal, the scanning output signal, and the scanning circuit. an output control circuit, a switching element switched by the output control circuit, and an impedance conversion circuit, one terminal of the plurality of switching elements is connected to the photoelectric conversion element, and the other terminal is connected to the photoelectric conversion element. All terminals are common and connected to the input terminal of the impedance conversion circuit, the output terminal of the impedance conversion circuit is connected to one terminal of the switching element, and the other terminal of the switching element is connected to the input terminal of the impedance conversion circuit, and the other terminal of the switching element is connected to the input terminal of the impedance conversion circuit. An image reading device characterized in that the image reading device is an output terminal, and outputs an image signal only during a period in which the switching element and the buffer circuit are controlled by the output control circuit.