JPH0262158A - Led array control circuit - Google Patents

Abstract

PURPOSE:To contrive the miniaturization of the title circuit and the reduction in weight by operating an LED array simultaneously for light emitting and light receiving. CONSTITUTION:LEDs constituting an LED array 10 are distributed for the light emitting and the light receiving, and for example, by lighting up every other light emitting LED, the original is lit up. Next, to receive the reflected light, by using a shift register 7, and successively conducting an input switch group 9, a photoelectric current from the LED connected to the input switch group 9 is outputted to a switch common terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an LED array control circuit, and in particular to an LV and D array used in a device having 4R printing and reading functions, typified by a facsimile machine. The present invention relates to an LED array control circuit that switches a light source for optical printing to a reading sensor of a reading device.

(Prior art) As a conventional LEI) array control circuit, the
- There is something disclosed in specification No. 216L19,
Figure 4 shows its configuration.

First, to explain the printing operation using the conventional circuit, first, the cathode side of the LED array is grounded by the switch SW, and a forward voltage is applied to the LED array. Next, by setting the select signal to a low level, the negative input terminals of the switching gates 101-1 to 101n are set to a high level.
One input terminal of the switching gates 102-1 to 102-n becomes low level. Since a data signal is input to the other input terminal of the switching gate 101-1, this data signal is output as is and input to one input terminal of the OR gate 103-1. Further, since the other input terminal of the switching gate 102-1 is at a low level, the switching gate 102-1
-1 output is low level, and this output OR gate 1
It is input to the other input terminal of 03-1. Here, OR
It can be seen that the output of gate 103-1 is the same as the data signal. The output of the OR gate 103-1, ie, the data signal, is input to the D terminal of the D-type flip-flop 104-1. Thereafter, by setting the latch signal to high level, the data signal manually input from the I)Q terminal is held in the D-type flip-flop 104-1, and by setting the latch signal to low level, the data signal held by the O terminal is held by the D-type flip-flop 104-1. is output from. This output data signal is transmitted to the switching gate 10.
Manual input is applied to one input terminal of 1-2. Thereafter, the data is shifted by the number of stages of the shift register in the same manner. Serial data signals are converted into parallel data signals in each flip-flop that makes up the shift register, and information on whether to light up each LED connected to it is stored, and the period when strobe 8 is active is stored. A current flows through the LED array to emit light, exposing a photosensitive drum (not shown).

Next, to explain the reading operation by the conventional circuit, first, a reverse voltage is applied to the LED array by the switch SW. Next, in order to obtain optical signals hitting the LEDs 105-1 to 105-n, a select signal is set to a high level, and the switching gates 102-1 to 102-n are activated. Then, the intensity of the optical signal hitting the LED 105-I N105-n is converted to low level or high level by the Schmitt trigger circuit S11, and the switching gates 102-1 to 1
D of D type flip-flops 104-1-104-n through OR gates +02-n and +03-1~10:]-n
Manual power is applied to the terminal. After that, by setting the latch signal to high level, the strength of the optical signal can be changed to the D-type flip-flop 1.
04-I N104-n. After that, by setting the select signal to low level, the switching gate 101
-1 to 101-n, synchronize with the clock signal,
Data from the document to be read held in each type flip-flop is outputted from the shift data out terminal.

(Problems to be Solved by the Invention) However, in the above conventional LED array control circuit,
When using an LED array as a light receiving element, the photoelectrically converted signal from the LED array is binarized using a Schmitt trigger circuit, so it is necessary to deal with misrecognition, gradation, and colorization of documents due to variations in the characteristics of the LED array. I can't get it.

Further, the control circuit 75 has a redundant light emitting section and a light receiving section, and the gate circuit for controlling it is complicated.

The present invention is intended to solve these problems, and it is an object of the present invention to provide an LED array control circuit that can realize a head in which high-performance light emitting and reading functions are integrated at low cost.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides an LED array formed by arranging a plurality of LEDs, which serves as a light source for the photoelectric device 1 and as a reading sensor that optically reads the object to be read. In an optical printing and optical reading device that uses a holding means for temporarily holding the print data shifted by the number of shift stages and supplying it to each LED;
A switching means for switching the direction of applying bias voltage to each LED according to whether it is for light emission or light reception, and each LIED for light reception.
The apparatus is characterized in that it is equipped with a reading means for obtaining reading information of the reading object by voltage converting and A/D converting the photocurrent from the apparatus.

(Function) According to the present invention having the above-described configuration, when data synchronized with the basic clock is manually inputted to the data input terminal during light emission operation, the data is shifted between shift registers, and the data is shifted by the number of stages of the shift registers. By inputting a latch signal at the shifted point and moving the data in the shift register to the holding means, the serially input print data is converted to one line of parallel data, and the forward voltage is reduced during the period when the strobe signal is active. is applied, the LED emits light and exposes the photosensitive drum.

In addition, during the light receiving operation, the LEDs constituting the LED array are divided into light emitting and light receiving, and, for example, every other odd-numbered light emitting LED is turned on by the application control means to apply light to the document. give Next, in order to receive the reflected light from the original with, for example, an even-numbered light-receiving LED, a shift register is used to sequentially turn on the manual switches, and the L is connected to the turned on manual switch.
The photocurrent from ED is output to the switch common terminal. This current is converted to voltage and amplified. This voltage is A
By performing the /D conversion, it is possible to obtain a digital signal that is read information corresponding to the shading of the object to be read in the original to be read.

Therefore, the present invention can solve the above-mentioned problems, and realizes a compact, low-cost, high-performance exposure light source and a reading sensor-integrated head that do not require lighting means such as fluorescent lights or LED lamps that were conventionally required for document reading. It is possible to provide an LED array control circuit that can perform

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 3 is a circuit diagram showing the operating principle of the present invention. In the same figure, a plurality of LEDs are arranged in a straight line.
D7 L' i1.0(7) i, ED 10-i~1
0-n alternately, e.g. LEDIO-1, LEDIO-
:] , -LEDIO-(n-1) f (light-emitting toshi,
LEDIO-2, LIEDIO-4, ...LEDlo
-n is controlled for light reception. During the reading operation, light from the light emitting device 1 and HD passes through the focusing lens 11 and illuminates the original 12, and this light is reflected on the original 12, and then the focusing lens!
(2) and is collected into the LIED for light reception. The intensity of this light corresponds to the current flowing through the LED array 10, so by measuring this current it is possible to know the darkness of the document.

During printing, a photosensitive drum is placed at the position of the document 12, and LEDIO-1 to LEDIO-(n-1
) to expose the photosensitive drum.

The LED array IO is given a potential in advance so as to be reverse biased, and when emitting light, this reverse bias is canceled out and a potential is given that is sufficient to cause a forward current to flow. When operating as a light receiving sensor, use it in a reverse bias state.

Next, referring to FIG. 1 and FIG. 2 which is a time chart showing the operation of this embodiment, the operation of this embodiment based on the operating principle of the present invention shown in FIG. 3 described above will be explained.

In FIG. 1, 1 is a shift register for print data;
2 is a latch circuit for data retention, 3 is a group of AND gates that control the light emission time of the LED array 1O, which will be described later, and 4 is O
R gate group, 5 is an output transistor group for driving LED,
6 is a group of current limiting resistors, 7 is a shift register for switching input channels, 8 is a group of AND gates for inhibiting manual switching, 9 is a group of input switches, and IO is an LED array. Note that the cathode side of the LED array 10 is connected to vn so that a reverse bias is applied, and the power supply common terminals v1. is l/+,
) Vn+V(+Vce). Here, V" is the voltage drop in the forward direction 7 of the LED, and vce is the collector-emitter saturation voltage of the output transistor 5 for driving the LED.

First, to explain the light emitting (printing) operation, continuous serial data is shifted between shift registers 1 by inputting data 1 synchronized with a clock. Second
As shown in the figure, when the number of stages of the shift register is reached, a latch signal is inputted so that the data for the line to be printed is held in the latch circuit 2. This output is connected to one input terminal of the AND gate group 3 for light emission time control, and makes the output transistor group 5 for driving the LED conductive only during the period when the strobe signal connected to the other input terminal is at a high level. Then, via the current limiting resistor group 6, the LED array 10 has a voltage exceeding the bias potential vn.
Since a sufficient potential is applied to light up D, the LED lights up according to the contents of the latch circuit 2.

Next, to explain the light receiving operation, first, by setting the LED lighting signal to high level, the output of OR gate group 4 becomes high level regardless of the state of latch circuit 2.
The output transistor 5 for driving the ED is made conductive and all the LEDs of the LED array 10 are lit. By setting the input switch inhibit signal to high level, the shift register 7
The manual switch group 9 can be opened and closed depending on the state. Next, data 2 is set to high level for a period corresponding to one stage of the shift register 7 synchronized with the clock signal, and kept at low level for the other period, so that one piece of data is shifted between the shift registers in synchronization with the clock signal. I'll go.

Then, by sequentially opening and closing the manual switch group 9, the second
As shown in the figure, the light from the LED for light emission is irradiated onto the original to be read, and the light and shade of the original to be read reflected from the original to be read becomes the intensity of the light and becomes an input to the LED for light reception. The intensity of the light results in changes in the current of the LED, and current signals corresponding to the shading of the original are sequentially output to the switch common terminal. The current signal is A/D converted through a current-voltage conversion circuit, an amplifier circuit, etc.

(Effects of the Invention) As described in detail above, according to the present invention, by operating the LED array for light emission and light reception at the same time, a small and low-cost facsimile machine that does not require any other lighting means; Alternatively, it can be used as a printer/image scanner device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a time chart showing the operation of this embodiment, and FIG. 3 is a configuration diagram showing the operating principle of the present invention. FIG. 4 is a circuit diagram showing a conventional LED array control circuit. 1.7--shift register, 2--latch circuit, 3, 8--AND gate group, 4--OR gate group, 5--output transistor group, 6--current limiting resistor group, 9 ...Input switch group, 1O-LED array.

Claims (1)

[Scope of Claim] An optical printing and optical reading device that uses an LED array formed by arranging a plurality of LEDs as a light source for optical printing and as a reading sensor for optically reading a reading target, comprising: A shift register is provided corresponding to the LED and shifts the print data by the number of the LEDs in synchronization with a basic clock, and a shift register is provided corresponding to the LED and temporarily stores the print data shifted by the shift register by the number of stages of the shift. a holding means for holding and supplying the LEDs to each of the LEDs, dividing the LEDs into light-emitting and light-receiving ones, applying a reverse bias voltage to each of the light-emitting and light-receiving LEDs, and applying the reverse bias voltage to the light-emitting LEDs; an applying means for applying a voltage sufficient to cancel the bias voltage and cause a forward current to flow; and voltage conversion and A/
1. An LED array control circuit comprising: a reading means for performing D conversion to obtain reading information of a reading target.