JPS59141867A - Original reading device - Google Patents

Abstract

PURPOSE:To accelerate the working speed of an original reader by connecting in common every plural units of output electrodes of switching elements provided in accordance with each photoelectric conversion output and delivering the output via an amplifier. CONSTITUTION:Switching elements 5a-5l like MOSFETs, etc. are provided in accordance with photoelectric converters 1a-1l of an original reader. The output electrodes of some adjacent ones of elements 5a-5l are connected in common and then divided into plural blocks. The outputs 9A-9C of these divided blocks are supplied to amplifiers 20A-20C respectively and then amplified. Then the outputs of amplifiers 20A-20C are supplied to an amplifier 12 via a signal line 8 to be amplified again and then extracted through a terminal 15. Thus the number of switching elements whose output electrodes are connected in common is reduced, and therefore the capacities of the signal lines 9A-9C are reduced. This can shorten the signal reading time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a document reading device used in facsimiles, etc., and in particular to a document reading device using a MOS photodiode array or CC
The present invention relates to a contact type document reading device that has been recently developed in contrast to an IC type document reading device such as a D image sensor.

In general, a contact type document reading device is constructed by forming a plurality of photoelectric conversion elements on an insulating substrate, and providing a circuit for switching and scanning the elements on the same substrate or externally. In addition, the length of the photoelectric conversion element array is the same size as the original, and since the original is read in one-to-one imaging using an optical system such as an optical fiber array or lens array, the imaging optical path length is This makes it possible to shorten the length of the document reading device (1), thereby achieving significant miniaturization of the document reading device.

Figure 1 shows an equivalent circuit (a) of a conventional contact type document reading device.
The schematic structure is shown in the same figure (b), (A-A in the figure)
'A cross-sectional view is shown in (C).

In the figure (a), numeral 1 is a photoelectric conversion element formed of a photoconductive thin film, and isometrically constituted by a photodiode PD and a capacitor CD. 5 is a MOS transistor for switching the photoelectric conversion element, 6 is M
OS) shift register for scanning transistor 5;
8 is a signal line, 10 is an Iasumi source, and 12 is an amplifier.

At \1, the photoelectric conversion element 1 is divided into upper and lower parts of the photoconductive thin film 3 by conductive thin films. It is made on the substrate 11 by sandwiching the electrode 2 and a continuous electrode made of a transparent conductive thin film 4. The switching circuit 7 is obtained by integrating the transistor 5 and the shift register 6 on a semiconductor substrate, and is mounted on the substrate 11 and connected to the photoelectric conversion element by wire bonding or the like.

Reading of a document image in such a document reading device is performed as follows.

Before entering the read cycle, shift register 6,
MO8) The transistors 5 are sequentially turned on, and the photodetector l is charged by the bias power supply 10.

Next, when a reading cycle begins, the charge stored in the capacitor CD is discharged by the photodiode PD according to the amount of light incident on the light receiving element 1. Next, the shift register 6 turns on the transistors 5 (MO8) sequentially to recharge the capacitor CD, and transmits the charging current to the signal line 8.
The optical information is further amplified by an amplifier 12 to read out the optical information. That is, a current for recharging flows in the portions that are discharged due to exposure to light, and no charging current flows unless discharge occurs in the black portions.

In this manner, the original can be read using the light receiving element section.

By the way, in the conventional document reading device as described above, all the photoelectric conversion elements 1 in the document reading device are commonly connected to one signal line 8 via separate MOS transistors 5. , the capacitance of the signal line was extremely large. Therefore, the time constant of the readout circuit formed by the signal line 8 and the amplifier 12 becomes large, making it difficult to read out signals through short-time switching, which is a major hindrance to increasing the readout speed. .

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an FC document reading device that can perform high-speed document reading by reducing the capacitance of the readout signal line.

That is, the present invention divides a plurality of switching elements such as MOS transistors, which are provided in one-to-one correspondence with the photoelectric conversion elements VC so as to switch each photoelectric conversion output from the photoelectric conversion elements, into a plurality of blocks. In order to connect the output electrodes of the switching elements in common for each block, and to amplify the switching output of the plurality of photoelectric conversion outputs obtained through the common connection line, one for each block. The device is equipped with an amplifier, the output terminals of the amplifiers are commonly connected, and each photoelectric conversion output is obtained through the commonly connected signal line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A document reading device according to the present invention will be described in detail below with reference to embodiments shown in the accompanying drawings.

FIG. 2 shows an embodiment of the document reading device according to the present invention. In addition, in FIG. 2, elements or circuits that have the same functions as the elements or circuits shown in FIG. 1 are shown with the same or corresponding numbers and symbols, and duplicate explanations will be omitted. .

In FIG. 2, 1a to 11 are equivalent circuits of photoelectric conversion elements, and 53 to 51 are connected to these in one-to-one correspondence.
is a switching element composed of, for example, a MOS transistor. These switch elements 5a to 51 share several adjacent output electrodes (four in this example) to form one block, and each gate electrode of these switch elements is connected to a differential output line of the shift register 6. Each is connected separately and performs a switching operation based on a switching pulse given from the shift register 6.

Further, the switching outputs from the switching elements 53 to 51 are input to separate amplifiers 20A to 20C for each group (N groups) and are appropriately amplified. The switching outputs amplified by these amplifiers 20A to 20C are input to the amplifier 12 via the signal line 8, where they are amplified again and then output as the final output to the terminal 1.
5 is output.

Now, in this embodiment, each photoelectric conversion element corresponds to a plurality of photoelectric conversion elements in a one-to-l ratio, and each of the signal lines 98 to 9C is divided into N blocks of 4 each. The switching output is obtained through the . Therefore, the capacitance of each of the signal lines 98 to 9C becomes ]/N compared to the conventional case where all switching outputs are read out by one signal line. As a result, the time constant when reading a signal is isometrically reduced to 1/N, and the rise time until the signal reaches a predetermined level can be reduced to approximately 1/N.

Furthermore, in the present invention, since each switching output obtained for each block is appropriately amplified by the amplifiers 20A to 20C, each signal obtained on the signal line 8 has a predetermined level that distinguishes the presence or absence of the signal. The rise time required to reach this point can be further shortened.

In addition, in this example, a normal I as a switch element is used.
Although a MO8I-transistor based on C was used, a thin film transistor formed integrally with a photoelectric conversion element may also be used as the switch element.

As described above, according to the document reading device according to the present invention, high-speed document reading can be performed.

[Brief explanation of drawings]

FIG. 1(a) is an equivalent circuit diagram of a conventional document reading device.
FIG. 1(b) is a plan view of the configuration of the document reading device shown in FIG. 1(a);
FIG. 1(C) is a sectional view taken along the line A-A' in FIGS.

Claims (1)

[Claims] A plurality of lower layer electrodes are provided on a substrate, and a photoconductor and a transparent conductive upper layer electrode are sequentially provided on the substrate to form a plurality of photoelectric conversion elements, and the respective electric conversion outputs of the photoelectric conversion elements are sequentially switched to generate a signal. In the document reading device configured to output data to a line, the signal line is divided into a plurality of signal lines, and each of the divided signal lines is provided with an amplifier whose output terminal is commonly connected. Document reading device.