JP2000068942A - Optical communication circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in reliability of transmission/reception due to deterioration or dirt with respect to a light emitting element and a light receiving element in the optical communication circuit. SOLUTION: In the optical communication circuit where communication between a circuit section of a CPU 200 and a circuit section of a CPU 210 is conducted by receiving a light emitted from a light emitting element 303 (313) of the one circuit section at a light receiving element 304 (314) of the other circuit section, the reliability in transmission/reception is maintained by adjusting at least any of a drive current of the light emitting element 303 (313), a drive frequency of the light emitting element 303 (313), a photoelectric conversion gain of the light receiving element 304 (314), a threshold level for waveform shaping of an output signal of the light receiving element 304 (314), and a sampling frequency of the signal after waveform shaping.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical communication circuit. The optical communication circuit of the present invention can maintain the reliability of data transmission / reception even in an environment where dirt easily adheres to a light emitting element or a light receiving element or an environment where characteristics are easily deteriorated, such as in an image forming apparatus. Can be.

[0002]

2. Description of the Related Art A plurality of substrates are mounted on an image forming apparatus such as a copying machine. These may be connected by optical communication using a light emitting element and a light receiving element for the purpose of reducing the influence of noise of electromagnetic waves or eliminating the work of routing a cable in a narrow space. Also, the image forming apparatus and the optional apparatus may be similarly connected by optical communication for the purpose of, for example, saving the trouble of cable connection.

[0003] Japanese Patent Application Laid-Open No. 4-114553,
In the optical communication system of the image forming apparatus, monitoring and resetting of transmission / reception by a communication command are performed, and in the case of a temporary transmission error, the master CPU is automatically controlled. A technique for restoring is disclosed. JP-A-4-44109,
Japanese Patent Laying-Open No. 4-44110 discloses an electric device that detects whether communication by optical communication means is possible by providing a pair of light receiving and emitting elements. JP 6
Japanese Patent Application Laid-Open No. 0-18937 discloses a photodetection circuit that enables reading of information by following a determination level in accordance with a change in output of a photoelectric conversion element due to a change in characteristics or adhesion of dirt.

[0004]

FIG. 5 shows an example of a conventional optical communication system. The LED emits light in response to the LED drive signal, and the amount of emitted light is fixed by the current limiting resistor R1. Light emitted from the LED is received by the photodiode and converted into a photocurrent. This photocurrent is converted into a voltage signal by an operational amplifier. The current-voltage conversion efficiency is set to a fixed value by the resistor R2.
The analog voltage signal output from the operational amplifier is shaped by a comparator. The comparator threshold is
The value is fixed by the resistors R3 and R4.

FIG. 8 shows a drive signal of the light emitting element of FIG. 5, a voltage signal after photoelectric conversion on the light receiving side, an output signal of the comparator, and a sampling pulse. FIG. (B) shows the case where there is dirt or deterioration.

As shown in the figure, a voltage signal after photoelectric conversion with respect to a driving signal of a light emitting element has a transmission delay due to a light emitting characteristic of the light emitting element and a response characteristic of the light receiving element, and has a rising and falling. Has a slope. Therefore, the output of the comparator obtained by binarizing this voltage signal with a predetermined threshold value has a high / low ratio corresponding to the high / low ratio of the drive signal of the light emitting element.
The row ratio is slightly different. The output of this comparator is
It is converted into a digital signal by sampling.

If there is no dirt or deterioration in the light emitting element and the light receiving element, the digital signal obtained by the above processing is equivalent to the original signal as shown in FIG. However, if the light emitting element or light receiving element is dirty or deteriorated,
As a result of the deterioration of the light emission characteristics of the light emitting element and the response characteristics of the light receiving element, the transmission delay time, rising slope, falling slope, and peak value change as shown in FIG. The low ratio is the high / low of the light emitting element drive signal.
As a result, the original signal cannot be decoded from the digital signal after the sampling process. The present invention aims to solve this problem.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a light emitting device (eg, LED), a light emitting device, a driving frequency of the light emitting device, a photocurrent / voltage signal conversion gain and a waveform of a light receiving device (eg, photodiode). The above-mentioned problem is solved by changing at least one of a threshold for shaping and a sampling interval.

According to the first aspect of the present invention, communication between the first circuit section and the second circuit section is performed by receiving light emitted from the light emitting element of the first circuit section by the light receiving element of the second circuit section. With the second
In the optical communication circuit which is performed by receiving light emitted from the light emitting element of the first circuit unit by the light receiving element of the first circuit unit, the light emitting state of the light emitting element of the second circuit unit is indicated from the first circuit unit. And the result received by the light receiving element of the first circuit unit
Wherein the light emitting element of the first circuit part is instructed to emit light by the circuit part of the first circuit part, and the parameters of the optical communication circuit are adjusted based on the result of light reception by the light receiving element of the second circuit part. It is a communication circuit.

According to a second aspect of the present invention, in the first aspect, the parameters of the optical communication circuit include a driving current of the light emitting element, a driving frequency of the light emitting element, a photoelectric conversion gain of the light receiving element, and a waveform of an output signal of the light receiving element. An optical communication circuit characterized by one or more parameters selected from a shaping threshold and a sampling frequency of a signal after waveform shaping.

According to a third aspect of the present invention, the communication between the first circuit unit and the second circuit unit is performed by receiving light emitted from the light emitting element of one circuit unit by the light receiving element of the other circuit unit. In the optical communication circuit to be performed, at least one of a driving current of the light emitting element, a driving frequency of the light emitting element, a photoelectric conversion gain of the light receiving element, a threshold for shaping the waveform of the output signal of the light receiving element, and a sampling frequency of the signal after the waveform shaping. An optical communication circuit characterized by maintaining reliability of transmission and reception by adjusting one of the two.

For example, when the waveform of the voltage signal after photoelectric conversion is degraded as shown by the broken line in FIG. 9A, the light amount of the light emitting element is increased or the gain of photoelectric conversion is improved. As shown by the solid line in the figure, the rising slope, the falling slope, and the peak value can be improved. As a result, the high / low ratio of the comparator output can be made closer to the high / low ratio of the driving signal of the light emitting element. it can. Further, by changing the threshold value of the comparator, the output can be made closer to the drive signal of the light emitting element.

Also, as shown in FIG. 9B, by changing the driving frequency of the light emitting element or changing the sampling period, a high-determining period of the waveform of the voltage signal after photoelectric conversion can be secured. Therefore, waveform shaping and sampling can be performed, and decoding can be performed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below based on the case where the present invention is applied to communication between the main body of a copying machine and an operation panel.

1. FIG. 1 shows the overall mechanism of the copying machine. The machine body 1 is placed on the paper feeding unit 21, and a self-service document conveying device 51 is provided on the machine body 1. A photosensitive drum 2 is provided at a substantially central portion in the body 1. The photosensitive drum 2 is driven to rotate in the direction of the arrow, and the eraser lamp 3 and the charger 4 make the image forming area into a uniformly charged state. The image of the document positioned on the platen glass 6 on the upper surface of the machine body 1 is exposed to the charged surface by the exposure optical system 5 to form an electrostatic latent image corresponding to the document image. The electrostatic latent image on the photosensitive drum 1 is developed by developing units 7 and 8
And developed into a visible image. Photosensitive drum 1
The upper visible image is transferred by the transfer charger 9 onto the supplied transfer sheet at the transfer section facing the transfer charger 9.

To the transfer section, a transfer sheet manually fed from a manual paper feed port 22 provided in the machine body 1 and a sheet fed from any of the paper feed cassettes 23 to 25 mounted on the paper feed unit 21 are fed. The transfer sheet is fed, and the image is transferred as described above. After the transfer sheet after the transfer is separated from the photosensitive drum 1, the transfer sheet is sent to a fixing device 11 by a suction-type conveyance belt 10 and is subjected to a fixing process. After fixing,
The transfer sheet is discharged to a discharge tray 12 outside the machine body 1.

A manual feed table 22 is provided in the manual feed port 22.
And guides the manually fed transfer sheet as needed. Each of the paper feed cassettes 23 to 25 includes a paper feed port 27 to 27 provided on the entire peripheral wall of the paper feed unit 21.
29, which is detachably set on the sheet feed rollers 30 to
By selectively driving the transfer sheet 32, a predetermined one of the transfer sheets in the sheet feed cassettes 23 to 25 set in the sheet feed ports 27 to 29 can be fed.

The manual feed table 26 and the paper feed cassettes 23 to
The transfer sheet fed from the feed rollers 25 to 25
The paper is conveyed toward the transfer unit by 2. The conveyed transfer sheet is sent to the timing roller 45 waiting at a stop, and the skew is prevented by the alignment of the leading edge. Is adjusted so that the leading end of the visible image formed on the photosensitive drum 1 and the leading end of the transfer sheet coincide with each other.

The self-contained document feeder 51 is provided so as to be opened and opened on the platen glass 6.
The self-service document feeder 51 is electrically connected to the body 1,
When the switch (not shown) detects that the body 1 is closed at the predetermined position, the control of the machine 1 and the self-service document feeder 51 are linked to each other, and the operation mode of the machine 1 is switched to the automatic document feed mode. .

In the automatic document feed mode, when the start key 52 provided on the automatic document feeder 51 is operated, the automatic document feeder 5 remains in the standby state with the machine body 1 in a standby state.
1 starts to operate, and the document tray 5 of the document feeding portion 55
The document set in 3 is sent out between the platen glass 6 of the transport section 56 and the transport belt 57 thereon, and transported to a predetermined exposure position on the platen glass 6 by the transport belt 57 and stopped. At this time, the automatic document feeder 5
1 issues a start signal to the machine 1 to start the copying operation. When the final exposure scan for the document at the exposure position is completed, a signal to that effect is issued from the machine body 1 to the self-service document conveyance device 51, and the automatic document conveyance device 51 transfers the document to the discharge tray 54 by the conveyance belt 57. To be discharged.

The exposure optical system 5 is of a mirror-scan type, and the copy magnification can be changed by moving the projection lens 61 in the optical axis direction. A first slider 64 having an illumination light source 62 and a first mirror 63 has V / m (V = m
While the scanning operation is performed at the speed of the peripheral speed of the photosensitive drum (m: copy magnification), the second slider 67 having the second and third mirrors 65 and 66 is moved at a speed of V / 2m.
Thereby, the optical path length corresponding to each magnification during scanning is kept constant.

The machine 1 has, as modes for selecting a transfer sheet at the time of copying, a paper automatic selection mode (APS mode) for automatically selecting the size of the transfer sheet, and a manual mode for the operator to set the size of the transfer sheet. . In the APS mode, the copy magnification is fixed, the optimal transfer sheet size is determined based on the size of the document to be exposed and the fixed magnification, the corresponding paper feed port is automatically selected, and the selected paper feed port is selected. In this mode, the transfer sheet is fed from the mouth. The manual mode is a mode in which a copy work is performed by arbitrarily selecting a copy magnification and a transfer sheet size. A
In order to detect the size of the original in the PS mode, the original can be detected in the vicinity of the original insertion opening of the conveyance section 56 of the automatic original conveyance device 51 regardless of the size and orientation of the inserted original. A document length sensor 72 that detects the size of the document in the transport direction, that is, the document length,
A document width sensor 73 is provided which takes two states of detection / non-detection depending on the width of the document to be inserted. It is configured to identify size and orientation. Note that the document size detection mechanism is not limited to the above configuration, and various known configurations may be employed.

The paper feed unit 21 has a paper feed cassette 23 set in each of the paper feed ports 27 to 29 in order to provide a copy of a transfer sheet of a size automatically selected in each of the above modes or manually selected. Sensors 75 to 77 for detecting the presence or absence of transfer sheets in the cassettes 25 to 25, sensors 78 to 80 for detecting the remaining amount of transfer sheets stored in the set paper feed cassettes 23 to 25, and transfer sheets stored therein Are provided. Further, when paper is fed from the paper feed cassettes 24 to 26 set in the paper feed ports 27 to 29, paper feed sensors 84 to 86 for detecting this are also provided. Meanwhile, Aircraft 1
The manual paper feed port 22 is provided with a manual feed sensor 87 for detecting that a transfer sheet has been manually fed, and a manual paper feed sensor 88 for detecting that a manual transfer sheet has been fed. Immediately before the timing roller 45, a sensor 89 for detecting a transfer sheet fed from the paper feed ports 27 to 29 or the manual feed port 22 is provided. The timing at which the timing roller 45 is turned on is controlled. In addition,
A main motor 91 that drives a mechanism in the body 1 is provided in the body 1. Also, the paper feeding unit 21 includes
A paper feed motor 92 for driving a mechanism in the paper feed unit 21 is provided.

2. control panel. The body 1 is provided with an operation panel 101 as shown in FIG. In the figure, 102 is a print key for starting copying, 103 to 112 are numeric keys for entering numbers from 0 to 9, 113 is a clear / stop key used for clearing the number of copies, stopping the copying operation, etc., and 114 is a clear / stop key. A
A mode selection key for selecting a PS mode / AMS mode / manual mode, 115 and 116 are up / down keys for a copy magnification, and 117 is an LCD display for displaying various messages. Is displayed. Each of the above keys, the display contents of the display unit 117, the airframe 1,
Input and output in the paper feeding unit 21 are controlled by a control circuit shown in FIG.

The CPU 2 for controlling the operation panel 101
10 and a CPU for controlling the machine body 1 and the paper feeding unit 21
200 is connected by the optical communication of the present invention.

3. Copier control circuit. FIG. 3 shows a control circuit of the copying machine. CPU 200 (master CPU) for controlling the copying machine main body (body 1 and paper feed unit 21), and CPU 210 for controlling operation panel 101
Optical communication is performed with the (slave CPU). CP
U200 controls a system necessary for a series of copying operations such as a paper transport system, an image forming system, a document exposure system, and a document detection system. CPU 210 is an LED
102-116, LED 211, LCD circuit 214-2
15 is controlled.

The CPU 200 performs input processing from a sensor or the like in the copying machine main body, controls output to a load or the like, and accesses the communication circuit 201 according to a software program stored in the ROM 204. Control RAM 205
Has a backup battery 206 and can hold data. The CPU 210 performs control according to a software program stored in the ROM 212.

4. Circuit for optical space communication. The LED 303 emits light according to the data transmitted from the CPU 200 of the main body to the communication circuit 201 and modulated. This light is received by the photodiode 304 on the operation panel side, demodulated by the communication circuit 216,
210. Thereby, the CPU 2 on the main body side
From 00, data is sent to the CPU 210 on the operation panel side.

Similarly, the LED 313 emits light in accordance with the data transmitted from the CPU 210 on the operation panel side to the communication circuit 216 and modulated. This light is received by the photodiode 314 on the main body side, demodulated by the communication circuit 201, and taken into the CPU 200. As a result, the CPU 210 on the operation panel side switches to the CPU 2 on the main body side.
Data is sent to 00.

FIG. 4 is a block diagram showing a portion (optical communication circuits 201 and 216, LEDs 303 and 313, and photodiodes 30 and 313 of FIG. 3) involved in optical communication between the main body and the operation panel in FIG.
4 and 314, and CPUs 200 and 210).

The parallel data from the CPU 200 (body side) is converted into serial data by the converter 301, and the LED driver 302 drives the LED 303 according to the serial data to emit light. This light is received by the photodiode 304 (operation panel side), converted into an electric signal, amplified by the amplifier 305, and
After being demodulated into digital serial data at 06, the data is converted to parallel data by the converter 307 and
Input to 0.

Similarly, the parallel data from the CPU 210 (on the operation panel side) is converted into serial data by the converter 311, and the LED driver 312 drives the LED 313 to emit light according to the serial data. This light is received by a photodiode 314 (main body side), converted into an electric signal, amplified by an amplifier 315, demodulated into digital serial data by a demodulator 316, and then converted into parallel data by a converter 317. Being C
It is input to PU200.

The CPU 200 (or 210) adjusts the drive current of the LED 303 (or 313), adjusts the emission frequency of the LED 303 (or 313), adjusts the gain of the amplifier 315 (or 305), and shapes the waveform according to the procedures described later. Adjustment of the threshold value and adjustment of the sampling frequency of the demodulator 316 (or 306) reduce errors in transmission and reception of optical space communication inside the copying machine.

Here, a mechanism for adjusting the gain and the like of the amplifier will be described. FIG. 6 shows an example of the internal configuration of the amplifiers 305 and 315. The photodiode 304 (or 31)
The signal output from 4) is converted into a voltage signal by the operational amplifier 352 and the like, and is input to the operational amplifier 353 in the next stage. This signal is amplified by the operational amplifier 353 and the gain adjustment circuit 354 at a predetermined gain determined according to the gain adjustment signal from the CPU 210 (or 200).
In the illustrated example, the gain is adjusted by the analog switch SW.
This is performed by changing the condition of the negative feedback using 1, SW2 and SW3. The signal output from the operational amplifier 353 is
The digital signal is converted by the comparator 355. At the time of this conversion, the comparator 355 inputs the analog threshold value adjustment signal obtained by D / A conversion of the digital threshold value adjustment signal from the CPU 210 (or the CPU 200) by the D / A converter 356 as a Ref signal, thereby obtaining the threshold value. To adjust.

Next, a mechanism for adjusting the sampling frequency of the demodulator will be described. FIG. 7 shows demodulators 306 and 3
16 shows an example of the internal configuration of the H.16. Amplifier 305 (or 31
The output from 5) is sampled by the sampling circuit 360. The sampling clock is generated by the oscillator 364 and the programmable counter 362 based on an instruction value from the CPU 210 (or 200). When the start bit is recognized by the sampling circuit 360, a latch signal for capturing data is generated by the counter 363 based on the sampling clock and sent to the flip-flop 361. As a result, the data is captured by the flip-flop 361, and the output from the amplifier 305 (or 315) is converted into serial data having a predetermined data length.

5. Adjustment procedure. Next, in order to maintain the reliability of the transmission and reception of the optical communication circuit by the CPU 200 and the CPU 210, the parameters of the optical communication (the driving current of the light emitting element, the gain of the receiving side, the light emitting frequency)
Will be described with reference to a flowchart.

5-1. Main routine. 10A is a flowchart of a main routine of the CPU 200, FIG. 10B is a flowchart of a main routine of the CPU 210, FIG. 10C is a flowchart of a communication confirmation operation procedure in the main routine of the CPU 200, and FIG.
It is a flowchart of the communication confirmation operation procedure in the main routine of U210.

As shown in FIG. 10A, when the power of the copying machine is turned on, the CPU 200 performs initial settings for clearing the RAM, setting the standard copying mode, and the like (S11). A communication confirmation operation procedure is executed (S13). Then, the internal timer starts (S2
1), a process for accepting input of various sensors and communication data (S23), a process for executing a series of operations from a start to an end of a copy operation (S25), and a process for processing and outputting control signals and display signals. The process (S27) is repeatedly executed for each time managed by the internal timer (S29).

As shown in FIG. 10B, when the power of the copying machine is turned on, the CPU 210 performs initial settings for clearing the RAM, setting the standard copying mode, and the like (S51). A communication confirmation operation procedure is executed (S53). Thereafter, the internal timer is started (S6
1), a process of accepting input of various keys and communication data on the operation panel (S63), a process of processing data from the main body, turning on / off an LED, and processing and outputting a display signal of an LCD (S67). Is repeatedly executed for each time managed by the internal timer (S69).

As shown in FIGS. 10C and 10D, the CP
The communication check operation procedure between the U200 and the CPU 210 includes static setting (S31, S71) and dynamic setting (S33, S73). Static setting (S3
In (1, S71), the drive current of the LEDs 303 and 313 and the reception gain of the photodiodes 314 and 304 are set. In the dynamic setting (S33, S73),
The light emission frequency of the LEDs 303 and 313 is set.

5-2. Static setting (Fig. 11-1
4). Each of the master side and the slave side waits for a predetermined time to elapse (S101, S301). This is because each adjustment operation on the master side and the slave side is started simultaneously. Also,
On each of the master side and the slave side, the light receiving side amplifier 30
5 and 315 are set to predetermined values (S102, S
302). This is for accurately measuring a predetermined pattern in the processing of steps S103 to S109 and steps S303 to S308 described below.

Steps S103 to S109 and step S
Steps 303 to S308 are steps for the master side to perform the adjustment operation. First, the LED 303 is turned on for a predetermined time.
Light is emitted in a predetermined pattern with a predetermined drive current, and an optical signal is sent to the slave side (S103, communication (1)). This light signal is a signal for instructing the slave to emit the LED 313 with a predetermined current for a predetermined time.
The light emission pattern of this signal is predetermined.

The slave sends the above instruction in step S
The process waits in a loop of 303, S306, and S307. The count cycle for standby is defined by the number of reference clock pulses. During the standby, if the above-mentioned instruction is not detected even after the elapse of a predetermined time (S307: NO), an error process is performed (S308).

When the above instruction is detected on the slave side (S303: YES), the drive current value indicated by
The LED 313 is caused to emit light for the designated time (S30
4, communication (2)). In step S305, it is determined whether or not the detected signal pattern corresponds to a predetermined final pattern.
5: NO), returning to step S303 and repeating the above processing. If the detected signal pattern is the predetermined final pattern (S305: YES), the process proceeds to step S309.

After giving the above-mentioned instruction in step S103, the master waits for communication (2) from the slave in a loop of steps S104, S107 and S108. The count cycle for standby is defined by the number of reference clock pulses. If the communication (2) from the slave side is not detected even after the lapse of a predetermined time during the standby, (S
108: NO), an error process is performed (S109).

When communication (2) from the slave is detected on the master side (S104: YES), the output level (analog voltage value) of the amplifier 315 at the time of communication (2) is read and stored in the RAM 205. Yes (S10
5). That is, the output level of the master-side amplifier corresponding to light emission for a predetermined time by driving with the predetermined current value instructed to the slave side is stored in the RAM 205. Step S10
In step 6, it is determined whether or not the instruction to the slave in step 103 has reached a predetermined number of times. If the number has not reached the predetermined number of times (S106: NO), the process returns to step S103 to repeat the above processing. That is, even if one communication fails, an error is not immediately made. The ratio between the predetermined value in step S108 and the specified number of times in step S106 is the allowable error rate. Note that statistical processing such as taking an average value may be performed. The same applies to the following similar processing. On the other hand, if the instruction to the slave side has reached the predetermined number of times (S106: YES), the process proceeds to step S110.

In step S110, the gain of the amplifier 315 on the master side is set to a predetermined value. Similarly, in step S309, the gain of the slave-side amplifier 305 is set to a predetermined value.

Steps S310 to S316 and steps S111 to S116 are steps for the slave side to perform an adjustment operation. First, the LED 313 is caused to emit light in a predetermined pattern at a predetermined drive current for a predetermined time, and an optical signal is sent to the master side (S310, communication (3)). This light signal is a signal for instructing the master to emit the LED 303 with a predetermined current for a predetermined time. The light emission pattern of this signal is predetermined.

The master sends the above instruction in step S
It waits in a loop of 111, S114, and S115. If there is no such instruction for more than a predetermined time (S11
5: NO), an error process is performed (S116).

When the above instruction is detected on the master side (S111: YES), the LED 303 is caused to emit light at the instructed current value for the instructed time (S112, communication (4)). In step S113, it is determined whether or not the detected signal pattern corresponds to a predetermined final pattern. If it is not the predetermined final pattern (S113: N
O), returning to step S111, and repeating the above processing. If the detected signal pattern is the last pattern (S113: YES), the process proceeds to step S117.

After giving the above-mentioned instruction in step S310, the slave waits for communication (4) from the master in a loop of steps S311, S314, and S315. If the communication (4) from the slave side is not detected for more than the predetermined time (S315: NO), error processing is performed (S316).

When the communication (4) from the master is detected on the slave side (S311: YES), the output level (analog voltage value) of the amplifier 305 at the time of the communication (4) is read and stored in the RAM 217. Yes (S31
2). That is, the output level of the slave-side amplifier corresponding to the light emission for a predetermined time by the driving with the predetermined current value instructed to the master side is stored in the RAM 217. Step S31
In 3, it is determined whether or not the instruction at step 310 to the master has reached a predetermined specified number of times. If the number has not reached (S313: NO), the process returns to step S310 and repeats the above processing. On the other hand, if the instruction to the slave side has reached the predetermined number of times (S313: YES), step S3
Proceed to 17.

In step S117, the gain of the amplifier 315 on the master side and the drive current value of the LED 313 on the slave side are determined based on the results described above. Further, the determined drive current value of the LED 313 on the slave side is instructed to the slave side (S117, communication (5)).

The slave waits for the communication (5) instruction in a loop of steps S317, S320 and S321. If there is no such instruction for a predetermined time (S321: NO), error processing is performed (S32).
2). When the instruction of the communication (5) is detected on the slave side (S317: YES), the LED 313 is turned on.
Is set to the instructed value (S31).
8).

In step S319, the gain of the amplifier 305 on the slave side and the drive current value of the LED 303 on the master side are determined based on the result described above. Further, the determined drive current value of the LED 303 on the master side is instructed to the master side (S319, communication (6)).

The master waits for the communication (6) instruction in a loop of steps S118, S120 and S121. If there is no such instruction for more than a predetermined time (S121: NO), error processing is performed (S12).
2). Further, when the master side detects the above communication (6) instruction (S118: YES), the LED 303
Is set to the specified value (S11).
9).

5-3. Dynamic setting (Figs. 15 to 1)
8). Each of the master side and the slave side confirms the LED drive current value and the amplifier gain setting determined by the static setting described above (S201, S401).

Steps S202 to S208 and steps S402 to S407 are steps for the master side to perform an adjustment operation. First, the LED 303 is caused to emit light in a predetermined pattern at the determined drive current value and at the minimum frequency, and an optical signal is sent to the slave side (S202, communication (7)). This optical signal is sent to the slave
313 is a signal instructing to emit light at a predetermined frequency. The light emission pattern of this signal is predetermined.

The slave sends the above instruction in step S
It waits in a loop of 402, S405 and S406. If there is no such instruction for more than a predetermined time (S40)
6: NO), and perform error processing (S407).

When the above instruction is detected on the slave side (S402: YES), the LED 313 is made to emit light at the instructed frequency for a predetermined time (S403, communication (8)). In step S404, it is determined whether or not the detected signal pattern corresponds to a predetermined final pattern. If the detected signal pattern is not the final pattern (S404: NO), the process returns to step S402, and the above processing is repeated. If the detected signal pattern is the last pattern (S404:
YES), and proceed to step S408.

After giving the above-mentioned instruction in step S202, the master waits for communication (8) from the slave in a loop of steps S203, S206 and S207. If the communication (8) from the slave side is not detected for more than the predetermined time (S207: NO), error processing is performed (S208).

When communication (8) from the slave side is detected on the master side (S203: YES), the peak hold value of the output level (analog voltage value) of the amplifier 315 at the time of the communication (8) is read. RAM2
05 (S204). That is, the peak hold value of the output level of the master side amplifier 315 corresponding to the light emission by the driving at the predetermined frequency instructed to the slave side is set to R.
Store it in AM 205. The gain of the amplifier 315 is
This is a value determined by the static setting. In step S205, it is determined whether or not the instruction in step 202 to the slave side has reached a predetermined specified number. If not, (S205: NO), the process returns to step S202, and the above-described processing is repeated. If the instruction to the slave has reached the predetermined number of times (S205: YES), step S
Go to 209.

Steps S408 to S414 and S209 to S214 are steps for the slave side to perform the adjustment operation. First, the LED 313 is caused to emit light in a predetermined pattern at the determined driving current value at the minimum frequency, and an optical signal is sent to the master side (S408, communication (9)). This optical signal is sent to the master
A signal for instructing 303 to emit light at a predetermined frequency. The light emission pattern of this signal is predetermined.

The master sends the above instruction in step S
The process waits in a loop of 209, S212, and S213. If there is no such instruction for more than a predetermined time (S21
3: NO), error processing is performed (S214).

When the above instruction is detected on the master side (S209: YES), the LED 303 is caused to emit light at the instructed frequency for a predetermined time (S210, communication (1
0)). In step S211, it is determined whether the detected signal pattern corresponds to a predetermined final pattern,
If it is not the final pattern (S211: NO), the process returns to step S209, and the above processing is repeated. If the detected signal pattern is the last pattern (S211: YE
S), and proceed to step S215.

On the slave side, after performing the above-mentioned instruction in step S408, communication (10) from the master side is performed.
It waits in a loop of steps S409, S412, and S413. If the communication (10) from the master side is not detected for more than the predetermined time (S413: NO), error processing is performed (S414).

When communication (10) from the master is detected on the slave side (S409: YES), the peak hold value of the output level (analog voltage value) of the amplifier 305 at the time of the communication (10) is read. And its value in RAM
217 (S410). That is, the peak hold value of the output level of the slave side amplifier 305 corresponding to the light emission by the drive at the predetermined frequency instructed to the master side is stored in the RAM 217. Note that the gain of the amplifier 305 is a value determined by static setting. In step S411, it is determined whether or not the instruction in step 408 to the slave has reached a predetermined number of times. If the number has not reached (S411: NO), the process returns to step S408, and the above processing is repeated. When the instruction to the slave side has reached the predetermined number of times (S411: YES), the process proceeds to step S415.

In step S215, the light emission frequency of the LED 313 on the slave side is determined based on the result described above. In addition, the determined emission frequency of the LED 313 on the slave side is instructed to the slave side (S215, communication (1
1)).

The slave waits for the above communication (11) instruction in a loop of steps S415, S416 and S417. If the above-mentioned instruction has not been given for a predetermined time (S417: NO), error processing is performed (S41).
8). When the instruction of the above communication (11) is detected on the slave side (S415: YES), the LED 31
3 is set to the designated value (S41).
9).

In step S420, the light emission frequency of the LED 303 on the master side is determined based on the result described above. Further, the determined emission frequency of the LED 303 on the master side is instructed to the master side (S420, communication (1
2)).

The master waits for the above communication (12) instruction in a loop of steps S216, S217 and S218. If the above-mentioned instruction has not been given for a predetermined time (S218: NO), error processing is performed (S21).
9). When the above-mentioned communication (12) instruction is detected on the master side (S216: YES), the LED 30
3 is set to the designated value (S22).
0).

As described above, in the optical communication circuit of the present apparatus, the master side and the slave side instruct the light emitting elements of the other party to emit light, respectively, and detect the light emitting state by their own light receiving elements, and based on the results, Thus, the parameters of the optical communication are adjusted.

6. Another example. The above example is a case where the optical communication circuit of the present invention is applied to communication between the copying machine main body and the operation panel. However, the present invention is not limited to between the copying machine main body and the operation panel, and a plurality of substrates are provided in the apparatus. It is applicable when it is provided. For example, in the case of an image forming apparatus, a main CPU and a scanning CP
U, CPU for image processing, CPU for electrophotography laser drive, etc., and also communication between the main body and optional devices such as a document feeder, sorter, finisher, paper feed tray, etc. The same applies.

[0074]

According to the present invention, the light emission amount of the light emitting element (eg, LED), the driving frequency of the light emitting element, the gain of the photocurrent / voltage signal conversion of the light receiving element (eg, photodiode), and the waveform shaping are performed. At least one of threshold, sampling interval
Therefore, it is possible to prevent a decrease in the reliability of transmission / reception due to deterioration or contamination of the light emitting element or the light receiving element.

[Brief description of the drawings]

FIG. 1 is a central sectional view schematically showing a mechanism of a copying machine according to an embodiment.

FIG. 2 is an explanatory view showing a part of an operation panel of the copying machine shown in FIG. 1;

FIG. 3 is a circuit diagram showing a configuration of a control circuit of the copying machine shown in FIG. 1;

FIG. 4 is a block diagram showing a communication circuit in FIG. 3 and its periphery;

FIG. 5 is a circuit diagram showing an optical communication circuit.

FIG. 6 is a circuit diagram showing a configuration example of amplifiers 305 and 315 in FIG. 4;

7 is a circuit diagram showing a configuration example of demodulators 306 and 316 in FIG.

FIG. 8 shows a drive signal of a light emitting element, a waveform after voltage conversion of a photocurrent, a waveform after waveform shaping, and a sampling pulse;
(A) shows the case where there is no deterioration or the like, and (b) shows the case where there is.

FIG. 9 shows a drive signal of a light emitting element, a waveform after voltage conversion of a photocurrent, a waveform after waveform shaping, and a sampling pulse;
(A) When the influence of deterioration or the like is eliminated by increasing the light quantity of the light emitting element, improving the gain on the light receiving side, and changing the threshold, (b) when the influence of the deterioration or the like is eliminated by changing the driving frequency of the light emitting element Is shown.

FIG. 10 shows processing of CPU 200 and CPU 210;
(A) is a main routine of the CPU 200, and (b) is a CP.
The main routine of U210, (c) shows the communication confirmation operation procedure of (a), and (d) shows the communication confirmation operation procedure of (b).

FIG. 11 is a flowchart showing a part of the static setting process of FIG. 10 (c).

FIG. 12 is a flowchart showing the rest of the static setting process of FIG. 10 (c).

FIG. 13 is a flowchart showing a part of the static setting process of FIG. 10 (d).

FIG. 14 is a flowchart showing the rest of the static setting process of FIG.

FIG. 15 is a flowchart showing a part of the dynamic setting process of FIG. 10 (c).

FIG. 16 is a flowchart showing the rest of the dynamic setting process of FIG. 10 (c).

FIG. 17 is a flowchart showing a part of the dynamic setting process of FIG.

FIG. 18 is a flowchart showing the remaining part of the dynamic setting process of FIG.

[Explanation of symbols]

305 Amplifier (slave (operation panel) side) 315 Amplifier (master (main body) side) 303 Light emitting element (LED; master (main body) side) 313 Light emitting element (LED; slave; operation panel)
Side) 304 Light receiving element (photodiode; slave (operation panel) side) 314 Light receiving element (photodiode; master (main body) side)

Claims (3)

[Claims] 1. A communication between a first circuit unit and a second circuit unit, wherein light emitted from a light emitting element of the first circuit unit is received by a light receiving element of a second circuit unit, In an optical communication circuit in which light emitted from a light emitting element of a circuit section is received by a light receiving element of a first circuit section, a light emitting state of a light emitting element of a second circuit section is designated from the first circuit section. The light received by the light receiving element of the first circuit unit and the first circuit unit
An optical communication circuit, wherein a parameter of the optical communication circuit is adjusted based on a result of instructing a light emitting state of the light emitting element of the circuit section and receiving light by the light receiving element of the second circuit section. 2. The optical communication circuit according to claim 1, wherein the parameters of the optical communication circuit include a driving current of the light emitting element, a driving frequency of the light emitting element,
Photoelectric conversion gain of the light receiving element, a threshold for shaping the waveform of the output signal of the light receiving element, a sampling frequency of the signal after the waveform shaping,
An optical communication circuit characterized by one or more parameters selected from the group consisting of: 3. An optical communication circuit for performing communication between a first circuit unit and a second circuit unit by receiving light emitted from a light emitting element of one circuit unit by a light receiving element of the other circuit unit. And adjusting at least one of a driving current of the light emitting element, a driving frequency of the light emitting element, a photoelectric conversion gain of the light receiving element, a threshold for shaping a waveform of an output signal of the light receiving element, and a sampling frequency of the signal after the waveform shaping. An optical communication circuit characterized by maintaining transmission / reception reliability.