JPH0918729A - Color printer - Google Patents

Abstract

PURPOSE: To read a test pattern of each color in an excellent way with a light receiving element by setting all light emitting elements to be a stable state at high temperature to prevent fluctuation in the luminance even when the luminance is fluctuated due to a temperature change after start of lighting. CONSTITUTION: When a pattern print means prints out a yellow pattern, a magenta pattern and a cyan pattern as test patterns 67-78 onto an achromatic medium 9 moved sequentially, a sensor control means controls a lighting timing of 1st to 3rd light emitting elements 56-58 of a color sensor 7. Then only the 1st light emitting element 56 is lighted for the yellow pattern, only the 2nd light emitting element 57 is lighted for the magenta pattern, and only the 3rd light emitting element 58 is lighted for the cyan pattern, and the light receiving element reads each of the test patterns 67-78. The 1st to 3rd light emitting elements 56-58 are lighted at a point of time before the test patterns 67-78 reaches the position of the color sensor 7 to be made stable at a high temperature to prevent luminance fluctuation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color printer which detects a print density of a test pattern of three primary colors by a color sensor.

[0002]

2. Description of the Related Art A conventional color printer forms a full-color image by sequentially transferring a plurality of monochromatic color toners onto printing paper by electrophotography.

However, in such a color printer,
The print density and gradation of a specific color toner may be deteriorated due to changes over time of the color toner and the photosensitive drum.
In this case, since the color balance of the color image to be printed out is also deteriorated, the print quality is extremely deteriorated.

Therefore, in a conventional digital color copying machine including a color printer as a part, a multi-tone test pattern is printed by using yellow toner, magenta toner, cyan toner and black toner, and these test patterns are printed. Are illuminated with infrared light and read by a photo sensor, and the print densities of the color toners are individually corrected based on the output signal of the photo sensor.

Similarly, Japanese Patent Application Laid-Open No. 59-163968 and Japanese Patent Application Laid-Open No.
The color copying machine disclosed in Japanese Patent Laid-Open No. 60-189362 illuminates a multi-tone test pattern of color toner with a light emitting diode, reads it with a photo sensor, and corrects printing characteristics based on the output signal.

[0006]

In the color copying machine described above, a multi-tone test pattern printed with color toner is read by a photosensor and the print density is corrected according to the read density.

However, since the color toner hardly absorbs infrared rays or monochromatic light other than complementary colors, even when a multi-tone test pattern of each color is illuminated with infrared rays or monochromatic light, the change in print density of the test pattern is reflected. It is difficult to read as a change in light intensity.

In order to solve the above-mentioned problems, the present applicant has proposed, as Japanese Patent Application No. 7-118106, three light emitting elements whose wavelengths respectively correspond to the three primary colors and one light emitting element whose sensitivity is located over the entire three primary colors. We filed an application to read the test pattern of each color with a color sensor having a light receiving element. in this case,
Although the three light-emitting elements will emit light in synchronization with the corresponding color test pattern, the light-emitting elements change their emission brightness immediately after lighting due to temperature rise, and it was found that the test pattern detection results fluctuate. did.

[0009]

According to the first aspect of the present invention,
In a color printer that forms a full-color image by sequentially transferring at least yellow toner, magenta toner, and cyan toner onto a printing paper by an electrophotographic method, yellow toner, magenta toner, and cyan are used as test patterns on a moving achromatic medium. A pattern printing unit that forms a yellow pattern, a magenta pattern, and a cyan pattern with toner is provided, and the peak of the emission wavelength is 4
The first light emitting device located at 00 ~ 500 (nm) and the second light emitting device located at the emission wavelength peak at 500 ~ 600 (nm) and the second light emitting device located at the emission wavelength peak at 600 ~ 700 (nm) A color sensor having three light emitting elements and one light receiving element having a sensitivity of 400 to 700 (nm) is provided, and the color sensor is arranged at a position facing a sequentially moving test pattern in order.
Provided is a sensor control unit for individually controlling the light emission timing of each of the first to third light emitting elements of this color sensor,
The sensor control means turns on all of the first to third light emitting elements before the test pattern reaches the position of the color sensor, and the second and third light emission for the yellow pattern. Turn off the element, turn off the first and third light emitting elements for the magenta pattern,
For the cyan pattern, the first and second light emitting elements are turned off.

According to a second aspect of the present invention, in a color printer that sequentially transfers at least yellow toner, magenta toner, and cyan toner onto printing paper by electrophotography to form a full-color image, an achromatic medium that moves sequentially. Is equipped with a pattern printing means for forming a yellow pattern, a magenta pattern and a cyan pattern with a yellow toner, a magenta toner and a cyan toner as a test pattern, and the first emission having a peak emission wavelength of 400 to 500 (nm) is provided. Element and emission wavelength peak is 500 to 600
The second light emitting element located at (nm) and the peak of the emission wavelength are
The third light emitting element located at 600 to 700 (nm) and 400 to 700 (n
m) is provided with a color sensor having one light-receiving element having sensitivity, and the color sensor is arranged at a position facing a sequentially moving test pattern in order. A sensor control unit for individually controlling each light emission timing is provided, and this sensor control unit turns on only the first light emitting element for a yellow pattern and the second light emitting element for a magenta pattern. Only the third light emitting element is turned on for the cyan pattern, and the first light emitting element is turned on even before the test pattern reaches the position of the color sensor.

According to the third aspect of the present invention, the first or second aspect is provided.
In the invention described above, the sensor control means turns on the first light emitting element at a time before the test pattern reaches the position of the color sensor and at a time when the color sensor faces the gap between the test patterns.

According to the invention of claim 4, claim 1 or 2
In the invention described above, the sensor control unit turns on all of the first to third light emitting elements before the test pattern reaches the position of the color sensor.

According to the invention of claim 5, claim 1 or 2
In the invention described above, the sensor control means turns on all of the first to third light emitting elements at a time before the test pattern reaches the position of the color sensor and at a time when the color sensor faces a gap between the test patterns. Let

According to the invention of claim 6, claim 1 or 2
In the invention described above, the sensor control means turns on at least the first light emitting element at a time point after the test pattern has passed the position of the color sensor, and turns on after a predetermined time set in this state. Turn off the light emitting element.

[0015]

According to the present invention, when the pattern printing means forms the yellow pattern, the magenta pattern and the cyan pattern with the yellow toner, the magenta toner and the cyan toner as the test pattern on the achromatic medium which moves sequentially, the sensor The control means controls the light emission timings of the first to third light emitting elements of the color sensor so that only the first light emitting element is turned on for the yellow pattern and the second light emitting element is turned on for the magenta pattern. Only the third light emitting element is turned on for the cyan pattern, and the light receiving element reads each of these test patterns. The first to third light emitting elements are turned on before the test pattern reaches the position of the color sensor and are stabilized at a high temperature, so that the brightness variation due to the temperature change is prevented.

According to the second aspect of the invention, when the pattern printing means forms the yellow pattern, the magenta pattern and the cyan pattern with the yellow toner, the magenta toner and the cyan toner as the test pattern on the achromatic medium which moves sequentially, the sensor The first light emitting element is turned on for the yellow pattern and the second light emitting element is turned on for the magenta pattern by controlling the light emission timing of the first to third light emitting elements of the color sensor by the control means. , The third light emitting element is turned on for the cyan pattern, and the light receiving element reads each of these test patterns.

Since the first light emitting element is turned on before the test pattern reaches the position of the color sensor,
Even when the first to third light emitting elements are LEDs, the variation in the brightness of the first light emitting element is prevented. In other words, the blue LED that realizes the first light emitting element is the green LED that realizes the second light emitting element and the red LED that realizes the third light emitting element.
Since the brightness is lower, if the amount of current is increased in order to secure the required brightness, the brightness variation due to the temperature change becomes large. However, if the light is turned on before the test pattern reaches the position of the color sensor, the temperature is stabilized at a high temperature, and the fluctuation of the luminance is also prevented.

According to another aspect of the invention, the sensor control means turns on the first light emitting element at a time before the test pattern reaches the position of the color sensor and at a time when the color sensor faces the gap between the test patterns. Therefore, even when the first to third light emitting elements are LEDs, the variation in the brightness of the first light emitting element can be prevented better.

According to another aspect of the invention, the sensor control means turns on all of the first to third light emitting elements before the test pattern reaches the position of the color sensor. Even if the light emitting elements of the above are formed of LEDs, the variation in the brightness of all the light emitting elements is prevented.

In a fifth aspect of the present invention, the sensor control means emits the first to third light emission before the test pattern reaches the position of the color sensor and at the time when the color sensor faces the gap between the test patterns. Since all of the light emitting elements are turned on, even if the first to third light emitting elements are LEDs, the luminance variation of all the light emitting elements can be prevented better.

According to the invention of claim 6, the sensor control means turns on at least the first light emitting element at a time after the test pattern has passed the position of the color sensor. The temperature of the light emitting element is prevented from decreasing by the start, and the light emitting element that has been turned on is turned off after a predetermined time set in this state, so when the next work is started for a long time, The light emitting element is turned off.

[0022]

An embodiment of the present invention will be described below with reference to the drawings. Note that the directions such as front and rear and up and down in this embodiment are shown for convenience in order to simplify the description,
This does not limit the actual installation or use direction of the device.

First, as shown in FIG. 2, the color copying machine 1 which is the color printer of this embodiment has a main body control section 2, and the main body control section 2 includes an operation section 3 and a scanner section. 4, an image processing unit 5, a printer unit 6, a color sensor 7, etc. are connected. The scanner unit 4 and the image processing unit 5 are also connected to each other, and the printer unit 6 is connected to the image processing unit 5.

The structure of the printer unit 6 will be described below. First, as shown in FIG. 1, an endless transfer belt 9 that attracts and sequentially conveys a printing paper 8 is stretched by a pair of guide rollers 10 as an achromatic medium in a circulatory manner. First to fourth printing stations 11 to 1 are provided at positions facing the stretched transfer belt 9.
4 are arranged in order. These printing stations 11 to 14 have a structure in which a charging charger 17, a laser scanner 18, a developing device 19 and the like are arranged opposite to each other on the peripheral surface of the photosensitive drum 16 facing the transfer charger 15 via the transfer belt 9. And the laser scanner 18 is
The correction optical system 22 is arranged in the scanning optical path of the polygon mirror 21 arranged so as to face the laser light source 20.
Developing devices 1 of the first to fourth printing stations 11 to 14
Each of 9 contains a yellow toner, a magenta toner, a cyan toner, and a black toner (not shown) as color toners.

In addition, the laser driver 2 is provided in the laser scanner 18 of each of the first to fourth printing stations 11-14.
3 is connected to the polygon mirror 21 as shown in FIG.
A motor driver 25 is connected to the drive motor 24,
A video controller 26 is connected to these drivers 23 and 25. The charging charger 17, the transfer charger 15, a belt charger 27 for removing electricity from the transfer belt 9, a developing charger 28 for charging toner stored in the developing device 19, a toner replenisher 29, and a fixing device (not shown) Each of the heaters 30 has a high-voltage power supply 31 to 3
4, the driver circuit 35 and the control unit 36 are connected,
The fixing device is also provided with a thermistor 37.

Further, the photosensitive drum 16, the transfer belt 9, the developing device 19, the fixing device, the paper feeding device 38,
Each of the registration rollers (not shown) and the like has a drive motor 3
9 to 44 are connected, and the drive motors 39 to 42, which are DC (Direct Current) motors, are connected to a microcomputer 45 of the main body control unit 2 via a driver circuit 46, and the drive motors, which are pulse motors, are connected. The motors 43 and 44 are connected to a driver circuit 47 of the main body control unit 2. Further, the video control unit 26, the high-voltage power supplies 31 to 34, the driver circuit 35, the control unit 36, the thermistor 37, and the like of the printer unit 6 described above are also connected to the microcomputer 45 of the main body control unit 2. Have been.

Next, the structure of the main body control unit 2 will be described below.

First, in the microcomputer 45,
A paper discharge sensor 48, a paper end sensor 49, a registration sensor 50, a cassette size sensor 51, toner sensors 52 to 55, etc. are connected. The paper discharge sensor 48 detects the discharge of the printing paper 8 out of the machine, and the paper end sensor 49 detects the presence or absence of the printing paper 8 stored in a paper feeding cassette (not shown). To do. The registration sensor 50 detects a sheet feeding state to a registration roller, and the cassette size sensor 51 detects a size of a sheet feeding cassette. The toner sensors 52 to 55
Detects the presence or absence of color toner stored in the developing device 19. The microcomputer 45 includes a CPU (C
RAM (Random Access Mem)
ory), ROM (Read Only Memory), I / F (Interface)
And the necessary programs are formed as software instruments or firmware.

The structure of the color sensor 7 will be described below.

As shown in FIG. 1, the color sensor 7 is arranged at a position facing a side portion near the end of the transfer belt 9 of the printer unit 6, and as shown in FIG.
B-LED (Blue-Light Emitting) which is the first light emitting element
Diode) 56, G-LED (Green
-Light Emitting Diode) 57, the third light emitting element R
An LED (Red-Light Emitting Diode) 58 and one phototransistor 59 which is a light receiving element are included.

As shown in FIG. 6, the B-LED 56 is
Since the emission wavelength peak is located at about 460 (nm), it is located in the region of 400 to 500 (nm), and the emission is blue. Since the peak of the emission wavelength of the G-LED 57 is located at about 530 (nm), this is 500 to 600 (n).
m), and its emission is green. The R-LED 58 has an emission wavelength peak of about 600.
(nm), it will be located in the region of 600-700 (nm) and its emission is red. For this reason,
The LEDs 56 to 58 have different emission wavelength peaks as the three primary colors of light. Further, since the phototransistor 59 is sensitive to 400 to 700 (nm) at the light receiving wavelength, it is sensitive to the entire emission wavelength of the LEDs 56 to 58.

Then, as shown in FIG.
The transistor arrays 60 are individually connected to the cathodes 6 to 58.
Is connected to the output port of the microcomputer 45 of the main body control unit 2. A resistor 79 is connected to the anode of the B-LED 56, and the G-LED 56
Variable resistors 80 and 81 are connected to the anodes of 57 and the R-LED 58, respectively. Therefore, the G
Since the power applied to the LED 57 and the R-LED 58 can be changed by the amount of current, the G-LE
The light emission intensity of D57 and the R-LED 58 can be varied. Further, the phototransistor 59 includes:
A resistor 61 for converting the output signal from a current amount to a voltage value
And an amplifier 62 for amplifying an output signal. The amplifier 62 is connected to an A / D (Analog / Digital) input terminal of the microcomputer 45 of the main body control unit 2.

As shown in FIG. 3, the image processing unit 5 includes a γ conversion unit 63, a masking processing unit 64, a UCR processing unit 65, a multilevel conversion processing unit 66, a buffer memory (not shown), and the like. The γ conversion unit 63 is connected to the scanner unit 4, and the multi-value conversion processing unit 66 is connected to the printer unit 6. The operation unit 3
Is formed by a keyboard (not shown) for inputting various data such as copy conditions, and a display (not shown) for displaying and outputting various data such as operation guidance.

As will be described later in detail, the color copying machine 1 of this embodiment has a print mode and an adjustment mode set as operation modes. In the print mode, a color image is printed on the printing paper 8 with a plurality of color toners. In the adjustment mode, the print density of the color toner is detected and adjusted. In order to execute such an adjustment mode, the color copying machine 1 of this embodiment has a pattern printing unit, a reading control unit,
It has a sensor control means and a density correction means.

First, the pattern printing means reads image data of a test pattern from a memory (not shown) connected to a backup power source by the main body control unit 2, and causes the printer unit 6 to read the color sensor 7.
The patch images 67 to 78 are printed as test patterns on the side edge portions of the transfer belt 9 which are read by.

These patch images 67 to 78 are formed as a multi-tone test pattern for each color by forming a rectangular image in order of high density, medium density and low density with each color toner. Is. Specifically, a high density Y (Yellow) 67 which is a yellow pattern, a medium density Y68, a low density Y69, and a high density M (Magent which is a magenta pattern).
a) 70, medium density M71, low density M72, cyan pattern high density C (Cyanide) 73, medium density C74, low density C75, black pattern high density K (Black) 7
6, consisting of medium concentration K77 and low concentration K78.

Further, the reading control means controls the respective parts by the microcomputer 45 of the main body control part 2 to read the output signal of the phototransistor 59 in correspondence with the moving positions of the patch images 67 to 78. .

Further, the sensor control means, when the color sensor 7 reads the patch images 67 to 78, the LED 56 by the transistor array 60.
The driving of .about.58 is controlled by the microcomputer 45. As a result, the yellow patch image 6
7-69, the B-LED 56 is turned on. For the magenta patch images 70-72, the G-LED 56 is turned on.
The LED 57 is turned on, and the cyan patch images 73 to
75, the R-LED 58 is turned on, and for the patch images 76 to 78 of black, the G-LE
D57 is turned on.

Further, the sensor control means has a time before the patch images 67 to 78 reach the position of the color sensor 7 and a time when the color sensor 7 faces the gap between the patch images 67 to 78. , The patch image 6
After the time when 7 to 78 have passed the position of the color sensor 7, all of the LEDs 56 to 58 are turned on, and a predetermined time has passed since the patch images 67 to 78 passed the position of the color sensor 7. When exceeding, the LE that is emitting light
Turn off all of D56 to D58.

Then, the density correcting means individually corrects the print density of the color toner by the printer section 6 based on the output signal of the phototransistor 59 of the color sensor 7 which has read the patch images 67 to 78.

The sensor control means outputs the output intensity of the phototransistor 59 when the black intermediate density patch image 77 is illuminated by the B-LED 56.
The amount of current applied to the G-LED 57 and the R-LED 58 is set so that the output intensity of the phototransistor 59 when illuminated by the G-LED 57 and the R-LED 58 is the same.

The setting of the amount of current can be realized by adjusting the variable resistors 80 and 81 connected to the G-LED 57 and the R-LED 58, for example. More specifically, the B-LED 56 is the G-
Since the physical properties of the LED 57 and the R-LED 58 are lower than that of the LED 57 and the R-LED 58, the drive current of the B-LED 56 is relatively increased as compared with the drive current of the G-LED 57 and the R-LED 58.

In the amplifier 62 connected to the phototransistor 59 of the color sensor 7, the maximum output intensity when the color sensor 7 reads the patch images 67 to 78 is a voltage slightly lower than the power supply voltage. The amplification level is set so that

More specifically, the power supply voltage is 15 (V), and the output voltage of the color sensor 7 is 1.0 even when the high-density patch images 67, 70, 73, 76 of each color are read. It is about (V). Therefore, the output voltage of the amplifier 62 when the color sensor 7 reads the patch images 67 to 78 is 14 (= 15-1) at maximum.
The amplification degree of the amplifier 62 is set to 14 times so as to be (V). As a result of setting the amplification degree of the amplifier 62 in this way, the output voltage of the amplifier 62 when the color sensor 7 reads the low-density patch images 69, 72, 75, 78 is about 5 (V). Is.

With such a configuration, in the color copying machine 1 of the present embodiment, when the print mode is set as the operation mode, the scanner unit 4 reads a color image of a document (not shown) and RGB (Red) , Green, Blue) image data is generated, and the RGB image data is processed by the image processing unit 5.
Is converted into YMCK (Yellow, Magenta, Cyanide, Black) image data, and the printer unit 6 prints a color image on the printing paper 8 by electrophotography based on the YMCK image data. At this time, the main body control unit 2 controls the above-described scanner unit 4, image processing unit 5, and printer unit 6 based on the setting data input from the operation unit 3.

More specifically, when the color image of the original is copied onto the printing paper 8 as described above, the original is set on the scanner unit 4 and a predetermined input operation is performed on the operation unit 3.
Then, the main body control unit 2 drives and controls the scanner unit 4 in accordance with the copy conditions input to the operation unit 3, so that the scanner unit 4 reads the color image of the original and performs image processing on the 8-bit RGB image data. Output to section 5. At this time, the image processing unit 5 outputs a horizontal synchronizing signal S-LSYNC, an image clock S-STROBE, and a vertical synchronizing signal FGATE to the scanner unit 4 under the control of the main body control unit 2 to synchronize with these signal outputs. Then, the scanner unit 4 outputs the image data to the image processing unit 5.

Next, as shown in FIG. 4, the image processing unit 5 to which the image data is input responds to the image processing mode designating signal transmitted from the main body control unit 2 by γ conversion, masking processing and UCR. By sequentially executing image processing such as processing and multi-valued processing by pulse width modulation, the input RGB 8-bit image data is converted into YMCK 1-bit image data, and this image data is controlled by the main body. According to the control of the section 2, the horizontal synchronization signal P-LSYNC and the image clock P-ST
Output to the printer unit 6 together with ROBE. At this time, in order to output image data corresponding to the interval of the printer unit 6,
The image processing unit 5 temporarily stores the output image data in a buffer memory. When the user performs an input operation to execute the editing process on the operation unit 3 as desired, the image processing unit 5 controls the image processing unit 5 to perform the scaling process, the trimming, the color It also performs editing processing such as conversion and mirroring.

Next, the image data is the horizontal synchronization signal P-LSY.
The printer unit 6 output together with the NC and the image clock P-STROBE outputs the laser light from the first to fourth printing stations 11 to 14 according to the image data in synchronization with the horizontal synchronization signal P-LSYNC and the image clock P-STROBE. 20 is driven to emit light to form an electrostatic latent image on the circumferential surface of the photosensitive drum 16 that rotates sequentially.
At the first to fourth printing stations 11 to 14, the electrostatic latent image on the photosensitive drum 16 is developed with yellow toner, magenta toner, cyan toner and black toner, and the printing paper 8 conveyed sequentially by the transfer belt 9. Are sequentially transferred with the voltage applied to the transfer charger 15. This printing paper 8
Is printed with a single color image of yellow toner, magenta toner, cyan toner and black toner. The printing paper 8 on which the color image has been formed by the overprinting is heat-pressed by a fixing device and then discharged outside the machine. I do.

As described above, the color copying machine 1 of the present embodiment prints out a high-quality color image on the printing paper 8 in the printing mode. However, due to the change with time of the color toner or the photosensitive drum 16, the specific color toner is changed. Print density and gradation may deteriorate. Therefore, in order to eliminate such a situation, for example, the adjustment mode is executed as the operation mode at the time of executing the initial setting, the end process, the detection of a fixed cycle, the maintenance work, and the like. It

In this adjustment mode, the patch images 67 to 78 in which the print densities of the color toners sequentially change.
Is printed on the transfer belt 9, and these patch images 67 to 7 are printed.
8 is read as a multi-tone test pattern by the color sensor 7, and the printing density of the color toner by the printer unit 6 is individually corrected based on the output signal of the color sensor 7.

More specifically, when the print density of the color toner is tested as described above, the image data of the patch images 67 to 78 stored in advance in the memory (not shown) of the main body control unit 2 as a test pattern. Is read. Then, as shown in FIG. 1, a plurality of patch images 67 to 78 are sequentially printed by the first to fourth printing stations 11 to 14 of the printer unit 6 on the side edge portions of the transfer belt 9 which are sequentially circulated. Therefore, these patch images 67 to 78 sequentially reach the position of the color sensor 7 as the transfer belt 9 circulates.

However, as will be described below with reference to the flowchart of FIG.
Before reaching 8, all the LEDs 56 to 58 are turned on, and when the yellow patch images 67 to 69 first reach the position of the color sensor 7, the G-LE is reached at this point.
The D57 and R-LED58 are turned off, and the B-LED56
Only lights up. The yellow patch images 67 to 69 illuminated by the B-LED 56 are read by the phototransistor 59 of the color sensor 7, and when these patch images 67 to 69 pass the position of the color sensor 7, the yellow and magenta images are separated. Patch image 69,
G-LED 57 and R-LED 58 at the position of the gap 70.
And are turned on again, so at this point all LEDs 5
6 to 58 are lit.

Similarly, the following process is performed on the magenta patch image 70.
To 72, lights other than the G-LED 57 are turned off, cyan patch images 73 to 75 are turned off except the R-LED 58, and black patch images 76 to 78 are turned off except the G-LED 57. To be done. That is, all the LEDs 56 to 58 are turned on in the gap between the patch images 72 and 73 of magenta and cyan and the gap between the patch images 75 and 76 of cyan and black.

Even when the black patch image 78 passes, all the LEDs 56 to 58 are turned on,
This is turned off when both the end of the adjustment mode and the elapse of the predetermined time are confirmed. When the adjustment mode is continued without ending, or when the adjustment mode is restarted before the elapse of a predetermined time, the printing of the above-described patch images 67 to 78 is performed while all the LEDs 56 to 58 remain lit. And detection are repeated.

That is, before starting the adjustment mode, the LED 5
Since the temperature of 6 to 58 is prevented from lowering, the adjustment mode is always started well. Moreover, even in such a state, all the LEDs 56 to 58 are extinguished after a predetermined time elapses, so that when the adjustment mode is restarted for a long time, unnecessary power consumption is prevented and consumption of the LEDs 56 to 58 is reduced. To be done.

Further, since the color copying machine 1 of the present embodiment controls the turning on and off of the LEDs 56 to 58 as described above, the main body control section 2 controls the driver circuit 46 of the drive motor 40 for the transfer belt 9. The reference clock synchronized with the operation is counted, and the LED lights at the timing corresponding to this count value.
Drive 56-58. Similarly, since the phototransistor 59 reads the patch images 67 to 78 illuminated by the LEDs 56 to 58, the main body control unit 2 causes the phototransistor at the timing when the center of the patch images 67 to 78 arrives at the reading position of the color sensor 7. The output signal of 59 is read.

At this time, the phototransistor 59 of the color sensor 7 has the patch images 67 to 78 as shown in FIG.
Since a light amount that is inversely proportional to the density of the light is received and a current that is proportional to this light amount is output, this current amount is converted into a voltage value by the resistor 61 and then amplified by the amplifier 62 of the main body control unit 2 to be supplied to the microcomputer 45. Is output to.

The microcomputer 45 detects the change amount of the print density of the color toner as the γ value based on the output signal of the color sensor 7 and compares it with a preset reference value. As a result of this comparison, when the γ value is lower than the reference value, the setting of the γ conversion unit 63 is changed so that the change amount of the output data is increased with respect to the change amount of the input data, and the output voltage of the charger 17 is changed. increase.

That is, in the color copying machine 1 of the present embodiment, even if the print density or gradation of a specific color toner is lowered due to the change of the color toner or the photosensitive drum 16 with time, this is changed by each color toner. Since they can be corrected individually, the color balance of the printed image can be maintained well. Note that the print density and gradation of a specific color toner may increase due to such overcorrection and other factors. Therefore, when the γ value of the patch images 67 to 78 is higher than the reference value, , The setting of the γ conversion unit 63 is changed so that the change amount of the output data decreases with respect to the change amount of the input data, and the output voltage of the charger 17 is decreased.

In the color copying machine 1 of this embodiment,
As described above, the patch images 67 to 78, which are printed in multi-gradation with color toner, are illuminated by the LEDs 56 to 58 of the color sensor 7 with the light emission of complementary colors. The print density of 78 can be read with high accuracy, and the print density of the color toner by the printer unit 6 can be satisfactorily corrected.

Further, the LEDs 56 to 5 of the color sensor 7
8, the luminance fluctuates immediately after lighting due to temperature rise,
In the color copying machine 1 of this embodiment, patch images 67 to 78 are provided.
Since all the LEDs 56 to 58 are turned on before reaching the position of the color sensor 7, the LEDs 56 to 58 are turned on.
Up to 58 can illuminate the patch images 67 to 78 in a state in which the emission brightness is stable and does not fluctuate at high temperatures. Therefore, the phototransistor 59 of the color sensor 7 can detect the print densities of the patch images 67 to 78 with high accuracy, and the color copying machine 1 of the present embodiment satisfactorily corrects the print density of the printer unit 6. can do.

Moreover, since all the LEDs 56 to 58 are turned on even at the positions of the gaps between the patch images 67 to 78, the light emission brightness of these LEDs 56 to 58 can be stabilized extremely well. In addition, in the color copying machine 1 of the present embodiment, in order to simplify the processing, all the LEDs 56 to 58 are turned on only in the gaps of the portions of the patch images 67 to 78 where the color changes, but the present invention is the above. The embodiment is not limited to this, and the LEDs 56 to 58 may be turned on at the positions of the gaps of the patch images 67 to 78.

Further, even when the black patch image 78 has passed, all the LEDs 56 to 58 are turned on. Therefore, even when the processing operation in the adjustment mode is restarted, the patch images 67 to 78 are applied by the color sensor 7 from the beginning. It can be read well. In addition, when the adjustment mode is ended, when it is confirmed that the predetermined time has been exceeded, all the LEDs are turned off.
Since the lights 56 to 58 are turned off, the LEDs 56 to 58 are not left as they are.

Further, in the color copying machine 1 of this embodiment,
Although it has been illustrated that all the LEDs 56 to 58 are turned on to stabilize all the light emission luminances as described above, the present invention is not limited to the above embodiment, and the processing operation as described above is performed by the B-LED 56. It is also possible to execute only for. That is, the B-LED 56 is characteristically the G-LED.
Since the luminance is lower than that of the 57 or the R-LED 58, it is necessary to increase the amount of current in order to secure the required luminance. However, in this case, the luminance variation due to the temperature change of the B-LED 56 is G-.
It is larger than the LED 57 and the R-LED 58. As described above, when the brightness variation of the G-LED 57 or the R-LED 58 does not become a problem, and when only the brightness variation of the B-LED 58 becomes a problem, as described above, before the patch images 67 to 78 arrive or at the gap position. , B-LED 58 is preferably turned on.

For example, in the prototype of the color copying machine 1, the yellow patch images 67 to 69 are detected up to thirty times at five-second intervals while the B-LED 58 is continuously lit and the temperature is saturated. The B-LED 58 is appropriately turned on at five-second intervals after being turned off, and the yellow patch image 67 is displayed.
As shown in FIG. 8, when the B-LED 58 is temperature-saturated, the fluctuation of the detected concentration is slight, but the detected concentration does not change with time unless the B-LED 58 is temperature-saturated. It was confirmed that it will decrease.

Since black corresponds to a mixed color of yellow, magenta and cyan, this is the LED 56-58.
Any of the above can illuminate well. That is, in the color copying machine 1 of the present embodiment, the black toner patch images 76 to 78 are illuminated by the G-LED 57, but this may be illuminated by the B-LED 56 or the R-LED 58.

Further, the color copying machine 1 of the present embodiment is G-
Since the amount of current applied to the LED 57 and the R-LED 58 is properly set, the output intensity of the light receiving element when the black intermediate density patch image 77 is illuminated by the B-LED 56, and the G-LED 57 or R. -LED58
The output intensity of the light receiving element when illuminated by is the same. Therefore, since the output signals of the LEDs 56 to 58 are at the same level, the amplification degree of the amplifier 62 that amplifies the output signals is L.
It is not necessary to switch each of the EDs 56 to 58, and it is possible to use the region where the characteristics of the amplifier 62 are linear.

It should be noted that in the present embodiment, the patch image 77 of black intermediate density used for the output adjustment of the LEDs 56 to 58.
Shows a large change in the print density. Therefore, if the output intensity of the LEDs 56 to 58 is adjusted based on the patch image 77, this adjustment can be performed with high accuracy. However, if the output adjustment accuracy of the LEDs 56 to 58 has a margin, for example, the output intensity of the phototransistor 59 and G- when the transfer belt 9 is illuminated by the B-LED 56.
G so that the output intensity of the phototransistor 59 when illuminated by the LED 57 or the R-LED 58 becomes the same.
It is also possible to set the power applied to the LED 57 and the R-LED 58. In this case, the outputs of the LEDs 56 to 58 can be adjusted without printing the patch image 77, so that this work can be performed easily and quickly.

Further, in the color copying machine 1 of the present embodiment, since the amplification degree of the amplifier 62 is properly set,
The output intensity when the color sensor 7 reads the patch images 67 to 78 is set to a voltage slightly lower than the power supply voltage. Therefore, the output voltage of the color sensor 7 is amplified at the optimum ratio for detecting the densities of the patch images 67 to 78, and the print densities of the patch images 67 to 78 are detected with high accuracy. This will be described in detail below.

First, since the output signal of the color sensor 7 is weak, if it is transmitted to the separated microcomputer 45 without being amplified, noise is mixed and the density detection accuracy of the patch images 67 to 78 deteriorates. For this reason,
In the color copying machine 1 of the present embodiment, an amplifier 62 is arranged in the vicinity of the color sensor 7 and the output signal of the color sensor 7 is amplified and then transmitted to the microcomputer 45.

The output voltage of the color sensor 7 is maximum even when the patch images 67, 70, 73 and 76 are read.
About 1 (V), but when reading the transfer belt 9
It will be 3 (V). When the output voltage of the amplifier 62 reaches the power supply voltage, it saturates and loses linearity. For example, when the power supply voltage is 15 (V), the transfer belt 9
If the output voltage when reading
It is necessary to make the amplification degree of 5 times or less. However, if only the output voltage when the patch images 67 to 78 are read is required, the amplification degree of the amplifier 62 may be 15 times or less, and can be set to 14 times, for example.

In this case, the output voltage when the transfer belt 9 is read is saturated, but necessary patch images 67 to 78 are obtained.
Since the output voltage when reading is detected with a large amplification factor of 14 times, the accuracy of density detection of the patch images 67 to 78 is improved.

In the color copying machine 1 of the present embodiment, the patch images 67 to 78 are sequentially printed in a line on the side edge of the transfer belt 9, but the present invention is limited to the above embodiment. It is also possible to print the patch images 67 to 78 as described above on the printing paper 8 instead of the above. It is also possible to arrange the color sensor 7 on the peripheral surface of the photosensitive drum 16 in each of the printing stations 11 to 14 and read the patch images 67 to 78 on the peripheral surface of the photosensitive drum 16. Further, in a color printer (not shown) in which a developing device for each color and one transfer drum are arranged around one large-diameter photosensitive drum, a color sensor may be arranged around the photosensitive drum and the transfer drum. It is possible.

[0074]

According to the first aspect of the present invention, there is provided pattern printing means for forming a yellow pattern, a magenta pattern and a cyan pattern by using a yellow toner, a magenta toner and a cyan toner as a test pattern on an achromatic medium which moves sequentially. The emission wavelength peak is 400 to 500 (n
m) and the peak of the emission wavelength
A second light emitting element located at 500 to 600 (nm), a third light emitting element having an emission wavelength peak at 600 to 700 (nm), and one light receiving element having sensitivity at 400 to 700 (nm) And a color sensor having a color sensor, the color sensor is arranged at a position facing a sequentially moving test pattern in order, and the light emission timing of each of the first to third light emitting elements of the color sensor is individually controlled. This sensor control means turns on all of the first to third light emitting elements before the test pattern reaches the position of the color sensor, and the second and third light emission for the yellow pattern. By turning off the elements, turning off the first and third light emitting elements for the magenta pattern, and turning off the first and second light emitting elements for the cyan pattern,
For example, even if the first to third light emitting elements are LEDs and the brightness changes due to temperature change from the start of lighting, it is possible to stabilize all the light emitting elements at high temperature and prevent the brightness from changing. The test pattern of each color can be satisfactorily read by the light receiving element of.

In a second aspect of the present invention, pattern printing means for forming a yellow pattern, a magenta pattern and a cyan pattern by using yellow toner, magenta toner and cyan toner as a test pattern is provided on an achromatic medium that moves in sequence, The emission wavelength peak is 400 to 500 (n
m) and the peak of the emission wavelength is 50
The second light-emitting element located at 0 to 600 (nm) and the third light-emitting element whose emission wavelength peak is located at 600 to 700 (nm) and 400
A color sensor having one light-receiving element with a sensitivity of up to 700 (nm) is provided, and the color sensor is arranged at a position facing the sequentially moving test pattern in order. A sensor control unit for individually controlling the light emission timing of each element is provided, and this sensor control unit turns on the first light emitting element for the yellow pattern and turns on the second light emitting element for the magenta pattern. By turning on the light, the third light emitting element is turned on for the cyan pattern, and the first light emitting element is turned on even before the test pattern reaches the position of the color sensor. Even if the brightness of the first light emitting element fluctuates from that of the second and third light emitting elements, the first light emitting element is stabilized at a high temperature to prevent the fluctuation of the luminance. It is possible, it is possible to read the respective color test patterns to better by one of the light receiving element.

According to the third aspect of the invention, the sensor control means turns on the first light emitting element at a time before the test pattern reaches the position of the color sensor and at a time when the color sensor faces the gap between the test patterns. By letting
The first light emitting element can be more stably stabilized at a high temperature and the fluctuation of the luminance can be prevented.

According to the fourth aspect of the invention, the sensor control means turns on all of the first to third light emitting elements before the test pattern reaches the position of the color sensor, so that all the light emitting elements are turned on. Can be stabilized at a high temperature to prevent fluctuations in brightness.

In the invention according to claim 5, the sensor control means emits the first to third light emission before the test pattern reaches the position of the color sensor and at the time when the color sensor faces the gap between the test patterns. By turning on all of the elements, it is possible to better stabilize all the light emitting elements at high temperature and prevent fluctuations in luminance.

According to the sixth aspect of the invention, the sensor control means restarts the next work in a short time by turning on at least the first light emitting element after the test pattern has passed the position of the color sensor. In this case, it is possible to prevent the temperature of the light emitting element from decreasing and the startup to fluctuate, and by turning off the light emitting element that has been turned on after a predetermined time set in this state until the next work is restarted. The light emitting element is not turned on unnecessarily for a long time.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an internal structure of a color copying machine which is an embodiment of a color printer of the present invention.

FIG. 2 is a block diagram showing a circuit structure of a color copying machine.

FIG. 3 is a block diagram showing a circuit structure of an image processing unit of a color copying machine.

FIG. 4 is a block diagram showing a circuit structure of an image processing unit.

FIG. 5 is a block diagram showing a circuit structure of a color sensor.

FIG. 6 is a characteristic diagram showing an output voltage ratio of a color sensor.

FIG. 7 is a flowchart showing a processing operation for reading a patch image printed by the color copying machine as a test pattern.

FIG. 8 is a characteristic diagram showing an output variation of a color sensor.

[Explanation of symbols]

 1 Color Printer 7 Color Sensor 8 Printing Paper 9 Medium 56 First Light-Emitting Element 57 Second Light-Emitting Element 58 Third Light-Emitting Element 59 Light-Receiving Element 67-78 Test Pattern

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 1/028 B41J 3/00 D 1/04 H04N 1/04 D 1/46 1/46 Z

Claims (6)

[Claims] 1. A color printer for forming a full-color image by sequentially transferring at least yellow toner, magenta toner, and cyan toner onto printing paper by electrophotography, and yellow toner as a test pattern on an achromatic medium that moves sequentially. A pattern printing unit for forming a yellow pattern, a magenta pattern, and a cyan pattern with a magenta toner, a cyan toner, and a cyan toner is provided, and the peak of the emission wavelength is the first light emitting element located at 400 to 500 (nm) and the peak of the emission wavelength. The second light-emitting element with a wavelength of 500-600 (nm), the third light-emitting element with a peak emission wavelength of 600-700 (nm), and a single light-receiving element with a sensitivity of 400-700 (nm) Is provided, and the color sensor is arranged at a position facing a test pattern that moves sequentially in order. Sensor control means for individually controlling the light emission timing of each of the first to third light emitting elements of the first to third light emitting elements, the sensor control means is provided from the first to third time points before the test pattern reaches the position of the color sensor. All the third light emitting elements are turned on, the second and third light emitting elements are turned off for the yellow pattern, and the first and third light emitting elements are turned off for the magenta pattern,
A color printer characterized by turning off the first and second light emitting elements for a cyan pattern. 2. A color printer for forming a full-color image by sequentially transferring at least yellow toner, magenta toner, and cyan toner onto a printing paper by an electrophotographic method, and yellow toner as a test pattern on an achromatic medium that moves sequentially. A pattern printing unit for forming a yellow pattern, a magenta pattern, and a cyan pattern with a magenta toner, a cyan toner, and a cyan toner is provided, and the peak of the emission wavelength is the first light emitting element located at 400 to 500 (nm) and the peak of the emission wavelength. The second light-emitting element with a wavelength of 500-600 (nm), the third light-emitting element with a peak emission wavelength of 600-700 (nm), and a single light-receiving element with a sensitivity of 400-700 (nm) Is provided, and the color sensor is arranged at a position facing a test pattern that moves sequentially in order. The sensor control means for individually controlling the light emission timing of each of the first to third light emitting elements is provided, and this sensor control means turns on only the first light emitting element for the yellow pattern, and the magenta pattern For, to turn on only the second light emitting element, for the cyan pattern, to turn on only the third light emitting element,
The color printer, wherein the first light emitting element is turned on even before the test pattern reaches the position of the color sensor. 3. The sensor control means turns on the first light emitting element at a time before the test pattern reaches the position of the color sensor and at a time when the color sensor faces the gap between the test patterns. The color printer according to claim 1 or 2. 4. The color according to claim 1, wherein the sensor control means turns on all of the first to third light emitting elements before the test pattern reaches the position of the color sensor. Printer. 5. The sensor control means turns on all of the first to third light emitting elements at a time before the test pattern reaches the position of the color sensor and at a time when the color sensor faces a gap between the test patterns. The color printer according to claim 1 or 2, wherein 6. The sensor control means turns on at least the first light emitting element at a time point after the test pattern passes the position of the color sensor, and turns on after a predetermined time set in this state. The color printer according to claim 1, wherein the light emitting element is turned off.