JPH0132499B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a density pattern recognition device that recognizes density patterns on a document surface. Generally, when setting an original and making a copy, one looks at the shading of the original and sets the density dial appropriately. The current situation was that people ended up making unnecessary copies because they were too dark or too light. Therefore, a technique has been proposed that automatically recognizes the density of a document without relying on the human eye. For example, in JP-A-54-103352 and JP-A-55-138754, an original is illuminated with a lamp, and the reflected light image is guided to a photoelectric conversion element to obtain an electrical signal corresponding to the density of the original image. describes a technique for recognizing an image pattern (density pattern) of a document by converting this electrical signal from analog to digital and processing it with a microcomputer. However, in this technology, if a lamp to which AC voltage is applied is used as a lamp to illuminate the original, the amount of light from the lamp increases or decreases in response to the AC cycle of the voltage applied to the lamp.
The illuminance on the document surface changes in proportion to this, and even if the light is reflected from the same point on the document surface, the electrical signal from the photoelectric conversion element changes depending on the time. If document density detection is performed independently of the voltage applied to the lamp in this way, accurate document density detection cannot be performed. Furthermore, Japanese Patent Laid-Open No. 53-129625 discloses that the light reflected from the original is converted into an electrical signal by a light receiving circuit, and the peak value of this electrical signal is detected by a peak detection circuit. A technique is described in which a threshold level is set based on this difference, and the density of the original is detected by taking the difference between this level and the output signal of a light receiving circuit. However, even with this technology, if a lamp to which AC voltage is applied is used as a lamp to illuminate the document, the amount of light from the lamp increases or decreases in response to the AC cycle of the voltage applied to the lamp, so the illuminance on the document surface increases or decreases in proportion to this. changes, and the output signal of the light receiving circuit changes. Therefore, the whitest part and the blackest part of the document detected by the peak detection circuit change due to the influence of the AC voltage applied to the lamp, making it impossible to accurately detect the density of the document. SUMMARY OF THE INVENTION An object of the present invention is to provide a density pattern recognition device that can improve the above-mentioned drawbacks and accurately detect the density of a document. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a density pattern recognition device that detects a document pattern and the potential of an electrostatic latent image formed on a photoreceptor according to an embodiment of the present invention. The fiber lens array 2 converts the light into a photoelectric conversion element 3 such as a photodiode.
image on top. This light is converted into an electrical signal and is switched by the switching circuit 4, so that the AC voltage of the AC power supply reaches its maximum positive and negative values every half cycle, and is extracted at each point where the illuminance of the document is maximum. It will be done. The output signal of this switching circuit 4 is input to a peak hold circuit 5, and the peak value at this time is held. This peak value is converted into a digital signal by the A/D converter 6 and processed by the microcomputer 7. Further, the potential of the electrostatic latent image formed on the photoreceptor 8 is detected by a surface potential sensor (electrostatic field chopper type) 9,
The signal is converted into a digital signal by the A/D converter 10 and processed by the microcomputer 7. The outputs O ₅ , O ₆ , O ₇ of the microcomputer 7 are generated by detecting the size and external dimensions of the document detected by the photoelectric conversion element 3, and the outputs O ₁ to O ₄ are outputs based on the density of the document. It is generated by detecting the pattern with the photoelectric conversion element 3. Further, an A/D converter 6 and a microcomputer 7 are used to calculate the density ratio of the document surface. Furthermore, in the case of output O ₄ , the power supplied to the fixing device is controlled. output
O ₉ erases with light to ensure that no potential is applied to areas other than the original in order to uniformize the deterioration of the photoreceptor when the original is of a different size than the original, or in the case of reduction/magnification. This is done by recognizing the document size. FIG. 2 shows a schematic diagram of the configuration of the density pattern recognition apparatus of the embodiment shown in FIG. halogen lamp 1
4, fiber lens array 15, detection fiber lens array 16, photoelectric conversion element 17, charging corona power source 18, charger 19, surface potential sensor 2
0 is set. Further, 21 is a photoconductor, 22 is a developing device, 23 is a cleaning device for the photoconductor 21, 24 is a paper feed table, 25 is a registration roller, 26
27 is a transfer corona generator, 27 is a static elimination corona generator,
28 is a fixing roller, 29 is a paper discharge tray, and 30 is a transfer paper. Next, the operation of this device will be explained. First, when a scan command is issued from the microcomputer 7, the halogen lamp 14 lights up and the charger 1
9 charges the surface of the photoreceptor 21. Here, the photoreceptor 21 stops, and when the scanning device 13 moves in the direction of arrow A, the fiber lens array 15 places the original 11 on the charged photoreceptor 21.
An image is formed and exposed. At this time, the light irradiated by the halogen lamp 14 is reflected on the surface of the document and is formed into an image on the surface of the photoreceptor 21 through the fiber lens array 15, but a portion passes through the detection fiber lens array 16 and is converted into photoelectric material. The light is guided to the element 17, and the density pattern is detected. Photoreceptor 2
When charging and exposure on the photoreceptor 1 are completed, the photoreceptor 21 rotates and the exposed portion is sent to the developing device 22, where toner is attached to the charged portion on the photoreceptor and visualized. The toner image visualized on the photoconductor 21 is offset onto the transfer paper 30 by a transfer section consisting of a transfer corona generator 26 and a static elimination corona generator 27, fixed by a fixing roller 28, and then transferred to a paper discharge table. Sent on 29. In the above embodiment, the density pattern is detected using the reflected light from the original 11, but it is also possible to detect the density pattern using the toner image visualized on the photoreceptor 21 before transfer at the position indicated by arrow B. It is possible. Also arrow C
At the position, the density pattern can be detected from the image of the toner transferred to the transfer paper. This B, C
If a density pattern is detected at the position, the post-process is only fixing, so power supply to the fixing section can be controlled. In addition, in the case of continuous copying,
It can be used to control the second and subsequent images. Further, the output from the surface potential sensor 20 is converted into a digital signal by an A/D converter and input to the microcomputer 7. This surface potential sensor 20
The surface potentials of the dark and light parts of the photoreceptor 21 are detected, and the degree of fatigue of the photoreceptor 21 is calculated by the microcomputer 7 by referring to the data on the number of copies. To improve copy quality, the surface potential is set to 700V,
Increase the voltage to 750V and then 800V. That is, this is because the potential of the light portion corresponding to the background portion of the original 11 on which light is irradiated onto the photoreceptor changes by about 50 to 150 V with fatigue, and the corona output of the charger 19 is adjusted to 5.5 V depending on this value. Increase KV, 6.0KV, 6.5KV. As a result, the degree of fatigue of the photoreceptor is improved and proper copies can be obtained. In the above description of the embodiment, the detection fiber lens array 16 is used to detect the density pattern of the original 11, but instead of this detection fiber lens array 16, the detection fiber lens array 16 as shown in FIG. A plurality of fibers 31 are provided in the fiber 31.
The photoelectric conversion element 1 is connected via the fiber connector 32.
It may be connected to 7. Note that as the photoelectric conversion element 17, a CCD, a photodiode array, a phototransistor array, or the like is used. Further, as shown in FIG. 4, the end surface 33 of the fiber 31 facing the original is processed into a lens shape to facilitate light condensation. FIG. 5 shows a schematic configuration of a density pattern detection section using an area CCD as the photoelectric conversion element 17, where 11 is a document, 7 is a microcomputer, 34 is an area CCD, and 35 is a buffer. The Elijah CCD34 that is currently on the market at a low price is 100
×100 elements, that is, 10,000 points, can be recognized. Scanning is performed by timing pulses output from the output terminal OUT of the microcomputer 7, and the output from the area CCD 34 is sent via the buffer 35 to the serial import Si of the microcomputer 7.
is input. Therefore, since the video pulse from the area CCD 34 passes through the buffer 35,
The black part is "1", the white part is "0",
The data is input to a register connected to the serial import Si and processed according to instructions from the microcomputer 7. Note that the black-white ratio can be calculated by counting the number of "1" portions, ie, black portions, among the video pulses from the area CCD 34. Also, line (one-dimensional) instead of Elijah CCD
CCD may also be used. In this case, the CCD or document moves to scan. By using a 1710-bit line CCD in a horizontal row of A4 transfer paper, you can recognize each character, and if you do not use a lens,
It is possible to create a CCD that is as long as the original size. FIG. 6 shows a perspective view of a practical density pattern detection unit according to an embodiment of the present invention, in which reflected light from an original is irradiated onto a photodiode 36 through a detection fiber lens array 16 and a fiber 31. . In this embodiment, the density of the document pattern is detected by guiding the light from the detection fiber lens array 16 through the fiber 31 onto the photodiode 36.
As long as the axes of the detection fiber lens array 16 and the detection fiber lens array 16 can be aligned, the image may be directly formed on the photodiode. Furthermore, if photodiodes are configured in an array as a monolithic IC,
The greater the number of bits, the more advantageous it becomes. Next, the principle of the document scanning method of the present invention will be explained. First, divide the document 11, hold the divided sampling data for each small area, hold the maximum value of that column, and change that value to A/
D conversion is performed and processed by the microcomputer 7, but if the processing is performed by A/D conversion for each small area, as the scanning speed becomes faster or the number of detection areas increases, the processing of the A/D converter 6 becomes more difficult. The processing speed of the microcomputer 7 cannot keep up. Therefore, when scanning starts, the microcomputer 7 only performs switching according to the timing, and the peak hold circuit 5 stores the maximum value of the data output from the photodiode. For example, if there are 16 channels, the microcomputer 7 performs A/D conversion of these 16 channels and processes the data, ensuring reliable data even if the number of detections increases or the scanning speed increases. can be accessed. FIG. 7 shows an explanatory diagram of the document scanning method according to the embodiment of the present invention, in which measurement channels of X ₁ to _{X 8} are determined in the horizontal direction of the document, and measurements of Y ₁ to Yn are determined in the vertical direction. When the detection fiber lens array 16 mounted on the scan device ₁₃ shown in FIG. In this example, the sampling signal is sent from the microcomputer and the peak value is held, so 1
Eight pieces of data are obtained by one scan. FIG. 8 shows an example of data held by the peak hold circuit, in which only each peak value from measurement points Y ₁ to Yn is held. In this case, the peak value can be held by the microcomputer 7. That is, it is sufficient to A/D convert the analog data for each measurement point, compare the previous data with the newly fetched data, and leave only the larger value. FIG. 9 shows a circuit diagram of a switching circuit according to an embodiment of the present invention, in which 37 is a photodiode, 38 is a compensation photodiode for temperature compensation and canceling noise during switching,
39 and 40 are resistors, 41 and 42 are EFT transistors, and 43 and 44 are capacitors. Next, the operation of this circuit will be explained. First, from the microcomputer 7 to the EFT transistor 41,
42 switching signals are sent as timing signals. Here, since an AC lamp is used as the light source, that is, the exposure lamp 14 is driven by the AC voltage of the AC power supply, the light illuminance is
The light increases and decreases every half cycle of the AC, and when this light is detected by a photocell and observed with an oscilloscope, it appears to be pulsating, and it appears to be pulsating at 50Hz or 60Hz.
You can obtain illuminance with ripples in the Hz voltage waveform.
Therefore, when this illuminance is input to the zero cross microcomputer 7, an internal count is activated,
At maximum illuminance, that is, at 50Hz, the pulse interval is 5msec as shown in Figure 10 (at 60Hz, the pulse interval is 8.3msec).
Therefore, the above-mentioned switching signal is output at about 4.15 msec). This Rocross pulse serves as a start pulse for triggering an AC load, program-based phase control during power control, AC modulation, etc. By configuring the switching circuit as described above, a constant light intensity can always be obtained. In other words, the signal from the photodiode 37 is transmitted to the exposure lamp 1.
It will be output only when the light illuminance of No. 4 reaches the maximum illuminance, and this output signal will be output from the exposure lamp No. 1.
It is no longer affected by the pulsation of the applied voltage in step 4. FIG. 11 shows a peak hold circuit according to an embodiment of the present invention, where 45 and 46 are operational amplifiers;
47, 48, 49 are diodes, 50, 51 are resistors, 52 is a capacitor, 53 is an analog switch, and 54 is an input terminal. Next, the operation of this peak hold circuit will be explained. First, the peak voltage input from the input terminal 54
V _N is charged into a capacitor 52 via an operational amplifier 45 and diodes 47 and 48, thereby holding the peak value. In this circuit, a feedback loop is formed by operational amplifiers 45 and 46, and the forward drop of diodes 47 and 48 can be ignored.
Since the capacitor 52 is charged by the operational amplifier 45, high-speed charging is possible. Also, offset voltage and drift are small, and input leakage is low.
Accuracy is increased using a FET operational amplifier.
Also, the diode 48 and the resistor 51 are the diode 47
This is effective in keeping the voltage across the diode 48 at approximately zero when the diode 47 is off, and eliminating leakage from the diode 47. Therefore, the leakage current is determined mostly by the input bias current of the capacitor 52 and the operational amplifier 46. The diode 49 connects the output of the operational amplifier 45 to V _IN -V _D (however, V _IN is the output of the operational amplifier 45).
5 input voltage, V _D is the voltage across diode 49)
The diode 47 is clamped to a deep bias to prevent the speed from decreasing. When the peak value is detected by this circuit, it is processed by the microcomputer 7, turns on the microcomputer 53 in preparation for the next cycle, and discharges the charge in the capacitor 52 through the resistor 51. FIG. 12 shows a circuit diagram of a copying machine according to an embodiment of the present invention, in which an A/D converter 6 guides the pattern of a document 1 through a fiber lens array 2 and converts it into a photoelectric conversion element consisting of a photodiode array. 3 performs photoelectric conversion, the switching circuit 4 switches the signal, the peak value is held in the peak hold circuit 5, the A/D converter 6 converts the signal into a digital signal, and the signal is decomposed into a 4-bit density pattern. 55 uses Intel's 8051 CPU,
MPU with built-in I/O, 4K bytes of ROM, RAM, and 256 bytes of internal counter (16 bits x 2)
It is. 56 is a memory I/O element containing a 2K byte mask ROM and a 16-bit I/O.
A/D converters 6 and 57 are manufactured by Ricoh Co., Ltd.
ADCRP201 is used, and this element has a resolution of 4 bits and has 8 channels built-in. The A/D converters 6 and 57 are accessed by individual instructions from the MPU 55. 58 is a speech synthesis chip made by NS, 59 is NS
This is a speech ROM made by the company, and each time a one-phrase voice response is sent, port P ₂ - ₁ of the MPU 55 is sent.
Make them aware through. In addition, 60 is a filter, 6
1 is an amplifier, and 62 is a speaker. The timing clock pulse synchronized with the photoreceptor has a linear velocity of 300 mm and a pulse interval of 5 msec.
A clock pulse for advancing the timing is input to _the port To of the MPU 55, and a signal for starting the timing is input to the port _R2-0 by reading a mark attached to one end of the photoreceptor with a photo sensor or the like. Also, the MPU55 can test ports T ₀ and T ₁ with 2-byte instructions, that is,
Depending on whether ports T ₀ and T ₁ are 1 or 0, the command of JT ₀ , JT ₂ or JNT ₀ , JNT ₁ can jump to a specific address and start executing a specific program. Also, port _T1 has AC voltage.
The zero-crossing pulse that detected the AC zero-crossing point is input. This performs a zero-crossing of the AC load and is programmed to connect _{the high} -speed
The SSR 63 is energized to control the power of the heater 64.
Also, start this zero cross pulse and MPU
The internal counter of No. 55 is driven and the phase angle of the phase control is programmed. The A/D converter 57 is connected to terminals such as a temperature sensor, human body sensors 1 and 2, jam detection, toner detection, cartridge (scanner) home position detection, cassette set, paper sensor, etc., and converts analog signals into digital signals. converted and processed. Regarding the temperature sensor and power supply detection, as described above, analog change values are converted into digital values and processed. Although not shown, the output from the surface potential sensor that detects the surface potential of the photoconductor is also input to the A/D conversion channel, and the surface potential of the dark and light areas is detected, and the fatigue level of the photoconductor is determined. Calculated by referring to data on the number of copies. In order to increase the printing capacity of this photoconductor and improve the quality of copies, the surface potential of the photoconductor was increased.
The voltage is increased to 700V, 750V, and 800V, because the potential of the background portion of the original, that is, the light portion where light is irradiated onto the photoreceptor, changes by about 50 to 150V with fatigue. This value determines the corona output.
Increase to 5.5KV, 6.0KV, 6.5KV. Next, the function of the A/D converter 6 will be explained. This A/D converter for copiers (model RP2P01) is connected to Intel's 8049 and the same series' 1-chip computer (NEC's μCOM43), and is capable of executing special instructions (MOV, ANL, ORL) specific to the computer.
can be used to read the A/D converter and conversion results. The A/D converter 6 has one 4-bit input/output port and a comparison type A/D converter, and a plurality of A/D converters can be connected to a one-chip computer. Figure 13 shows the A/D converter 6 and Intel
8049 is a diagram showing an example of connection with the computer 65, and Table 1 summarizes the instructions used.

【table】

【table】

[Table] In Table 1, the register is a 4-bit register provided inside the A/D converter 6, and conversion result registers 0 to 7 are analog signals input from analog input channels CH0 to CH7, respectively. The digital value resulting from A/D conversion is stored. The status register is a 4-bit register 66 that indicates or specifies the status of the A/D converter 6, as shown in FIG. Also, “conversion result register 0 (1, 2, 3) or 4 (5, 6, 7)
"Read" means that the instruction RDO (RD1, RO2, RD3)
When input from MPU65, A/D converter 6
This means that the output signal of the conversion result register specified by the second bit of the status register 66 is set as the content of the conversion result register. Furthermore, the contents of either the status register or the conversion result register are input by specifying the third bit of the status register, but "reading the status register"
means to output the contents of the status register 66. Next, the basic operation of this circuit will be explained. first,
When the power is turned on, input/output ports _P20 to _P23 are set to input mode by a built-in power-on clear circuit. Further, the status register, conversion result register, and reference voltage are set to zero. Figure 14 shows the basic operation of the A/D converter (RP2P01). In this A/D converter, all commands are sent to input/output ports P ₂₀ to _{P 23} at the falling edge of PROG.
The internal instruction is read into the register through (1
4 (see Figure 1). (1) RD0 to RD3 instructions After a short time after the instruction is read, conversion result registers 0 to 3, 4 to 7 are stored while PR0G is at a low level.
and RD0, the contents of the status register 66 is the port as shown in FIG.
It continues to be output to P ₂ to P ₂ (see FIG. 14, 2).
The selection is made by two or three bits of the status register 66. On the computer 65 side, the values of ports _P20 - _P23 are read after an appropriate time and PROG is returned to a high level. (2) RER instruction A short time after the instruction is read, the status register 66 and conversion result register are reset to 0, and the process ends when PROG returns to high level (see Figure 14). (3) SRS, REF command After the command is read, the computer 65 side sends the status 66 set data (see Figure 15) and reference voltage switching data (see Figure 2) to ports _P20 to _P23 . . data is port
While PROG is at a low level, it is taken into the status register (reference voltage switching register) (14th
(see Figure 2) and ends when port PROG returns to high level. The reference voltage becomes active when successive approximation is performed. (4) A/D Conversion Instruction (4-1) ADT Instruction The ADT instruction is an instruction to stop the A/D conversion operation being executed by the instructions AD0 to AD7. A short time after this instruction is read, the A/D conversion that has been executed periodically stops (the first
(See Figure 4). The contents of each of the conversion result registers 0 to 7 change depending on the analog input signal during the A/D conversion operation, but the contents are retained when the A/D conversion operation is stopped. After a suitable period of time, return port PROG to high level. This command is canceled by commands from ports AD0 to AD7. (4-2) AD0 to AD7 instructions When an instruction is read, the 0 bit of the status register is set to 1, and the 2 bits of the status register are set to 0 for AD0 to AD3.
Set to 1 for AD4 to AD7. Selected after port PROG returns to high level
A/D conversion of the AD input channel is started. When the A/D conversion is completed, the result is stored in the conversion result register, and the 0 bit of the status register is automatically reset to 0 (see FIG. 14, 5). Thereafter, A/D conversion is performed for the automatically selected next channel, and A/D conversion is subsequently performed periodically. However, if another command is executed during A/D conversion, A/D conversion will be temporarily stopped while port PROG is at a low level, and when port PROG becomes high level, A/D conversion for that channel will be restarted. Run from the beginning. The A/D conversion of this embodiment employs a successive approximation type, and FIG. 19 shows its principle, and FIG. 20 shows waveform diagrams of various parts. First, the D/A converter 68 is driven by the output of the successive approximation register 69, which is a combination of a shift register and a control gate, and the output is compared with the analog input by the comparator 67. 69's
Set the MSB (most significant bit) to “1” and compare the voltage at 1/2 of the full case with the analog input. As a result, if the input exceeds the comparison value, the second bit of the successive approximation register 69 is set to “1”.
, and if it is not exceeded, the successive approximation register 6
Reset the first bit of 9 and perform the next comparison. The conversion time is (number of bits + 1) x clock time, so a high speed conversion can be achieved. As explained above, according to the present invention, in a density pattern recognition device having a document scanning mechanism,
A light source driven by an AC power source illuminates the original, and a fiber lens array is used to guide the light beam reflected from the original to a photoelectric conversion element consisting of a photodiode, phototransistor, CCD, etc., and detects the density pattern on the original surface. a switching circuit that switches the output of the photoelectric conversion element; a peak hold circuit that holds the peak value of the output of the switching circuit; and A that converts the output of the peak hold circuit from analog to digital. A/D converter, a microcomputer that recognizes the density pattern of the document from the output of the A/D converter, a zero cross pulse synchronized with the AC power supply is input to the microcomputer to start an internal counter, and the AC power supply is activated. means for triggering the switching circuit at a point where the ripple component of alternating current is maximum with respect to the frequency of Since the present invention comprises a means for transmitting a peak value to the peak hold circuit and holding the peak value, the density of the original can be detected at a constant illuminance, and the density of the original can be detected accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a density pattern recognition device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of the pattern recognition device of FIG. 1, and FIG. 3 is a side view of a density pattern detection section. FIG. 4 is a partial sectional view of the fiber lens, FIG. 5 is a schematic diagram of the density pattern detection section, FIG. 6 is a perspective view of the density pattern detection section, and FIG. 7 is an embodiment of the present invention. FIG. 8 is a diagram showing an example of data held by the peak hold circuit. FIG. 9 is a circuit diagram of the switching circuit according to the embodiment of the present invention.
0 is a waveform diagram of the light illuminance detected by the circuit of FIG. 9, FIG. 11 is a circuit diagram of a peak hold circuit according to an embodiment of the present invention, and FIG. The circuit diagram, Fig. 13, is a diagram showing an example of the connection between the A/D converter and the computer, and Fig. 14 is,
An explanatory diagram of the basic operation of the A/D converter, FIG.
Diagram showing the output signal of the status register, 1st
FIG. 6 is a principle diagram of the successive approximation type A/D conversion system, and FIG. 17 is a waveform diagram of each part. 1, 11... Manuscript, 2, 15... Fiber array, 3, 17... Photoelectric conversion element, 4... Stitching circuit, 5... Peak hold circuit,
6, 10...A/D converter, 7...Microcomputer, 8...Photoreceptor, 9,20...Surface potential sensor, 12...Original table, 13...Scan device, 14...Halogen for exposure Lamp, 16... Fiber lens array for detection, 18... Charging corona power supply, 19... Charger, 21... Photoreceptor, 2
2...Developing device, 23...Cleaning device, 2
4... Force paper stand, 25... Registration roller, 26...
... Transfer corona generator, 27 ... Static elimination corona generation, 28 ... Fixing roller, 29 ... Paper discharge table, 30
...Transfer paper.

Claims (1)

[Claims] 1 In a density pattern recognition device having a document scanning mechanism, a document is illuminated by a light source driven by an AC power supply, and a fiber lens array is used to convert the light beam reflected from the document into a photoelectric conversion device consisting of a photodiode, phototransistor, CCD, etc. a density pattern detection means that guides the photoelectric conversion element to the photoelectric conversion element and detects the density pattern on the document surface; a switching circuit that switches the output of the photoelectric conversion element; a peak hold circuit that holds the peak value of the output of the switching circuit; an A/D converter that converts the output of the peak hold circuit from analog to digital; a microcomputer that recognizes the density pattern of the document from the output of the A/D converter; means for inputting data into a computer to start an internal counter and triggering the switching circuit at a point where the ripple component of the alternating current is maximum with respect to the frequency of the alternating current power supply; and detection points divided in the scanning direction of the document surface. A density pattern recognition device comprising: means for detecting the detected value according to the timing of the microcomputer, and transmitting the detected value to the peak hold circuit to hold the peak value.