JPH09149254A - Image forming device and color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly precisely correct influence owing to the temperature change and the secular change of an optical sensor and the fluctuation of a measuring distance by setting a test pattern image to be a stripe-like test pattern image vertical to a travel direction. SOLUTION: In the test pattern images of respective colors, stripe-like 11YD-11KL vertical to the travel direction of a transfer belt 8 are arranged in a line in the travel direction on the transfer belt 8. The transfer belt 8 is rotated in the direction of an arrow with a motor, and the density of the stripe- like test pattern pictures 11YD-11KL on the transfer belt 8 is optically read by a color density sensor 12 when the stripe-like test pattern pictures 11YD-11KL on the transfer belt 8 pass below the color density sensor 12. At that, time, a host transistor receives the reflection light of luminous quantity proportional to the density of the stripe-like test pattern images 11YD-11KL, outputs current proportional to the light quantity and converts it into a voltage change. Thus the signal is converted into the digital signal and is processed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet and dry type color image forming apparatus such as an analog color copying machine, a digital color copying machine, a color printer and a color facsimile.
The present invention also relates to wet and dry image forming apparatuses such as an analog copying machine, a digital copying machine, a printer, and a facsimile that form a single-color or color image.

[0002]

2. Description of the Related Art A color image forming apparatus forms a plurality of color images with a plurality of monochromatic color toners and transfers these color images to a transfer material, such as an analog color copying machine, a digital color copying machine, a color printer, a color facsimile, and the like. Wet type or dry type electrostatic color image forming apparatus.
The image forming apparatus, in addition to these color image forming apparatuses,
There are wet-type and dry-type electrostatic image forming apparatuses such as an analog copying machine, a digital copying machine, a printer, and a facsimile which form a monochromatic image with a toner and transfer it to a transfer material. There is a method in which a test pattern image is formed by reading the density of the test pattern image with an optical sensor and the image density is controlled by the reading result of the optical sensor.

Further, in a color image forming apparatus, a toner patch image is read by a sensor having a spectral characteristic and the image density is corrected according to the result, or a toner patch image is formed by a sensor using a combination of light emitting elements and light receiving elements of three primary colors. Method of correcting the image density according to the result, a method of reading the toner patch image with a sensor that is a combination of a light emitting element and a light receiving element having a spectral characteristic, and correcting the image density based on the result, three primary color light emitting elements and light receiving There has been proposed a method of correcting a color mixture by reading a toner patch image with a sensor having a combination of elements or a sensor having a combination of a light emitting element and a light receiving element having a spectral characteristic and determining the degree of color mixing based on the result.

[0004]

In the above-mentioned method, when the density of the test pattern image is read accurately by the optical sensor, there is a problem that the temperature change of the optical sensor, the change over time, and the change of the measurement distance occur even slightly. Become. Therefore,
The optical sensor outputs a standard density patch at a certain cycle, and by correcting the output signal of the optical sensor with respect to the test pattern image from the result, the influence of temperature change and temporal change on the output signal of the optical sensor However, this still cannot eliminate the influence of the variation of the measurement distance on the output signal of the optical sensor.

The present invention solves the above-mentioned problems and is capable of highly accurately compensating for the output signal of the optical sensor from the influences of the temperature change of the optical sensor, the change over time, and the change of the measurement distance. An object is to provide an apparatus and a color image forming apparatus.

[0006]

In order to achieve the above object, the invention according to claim 1 forms an image with toner and transfers the image to a transfer material, and forms a test pattern image with the toner to form the test pattern image. In the image forming apparatus in which the optical density is read by an optical sensor and the image density is controlled by the reading result of the optical sensor, the test pattern image is a striped test pattern image perpendicular to the traveling direction.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the optical sensor of the optical sensor when the background portion of the striped test pattern image is read by the optical sensor in a predetermined state in advance. The output signal Sk is stored, and the output signal of the optical sensor when the toner portion of the striped test pattern image is read by the optical sensor during image formation is Sc, and the optical sensor is formed during image formation. Therefore, when the output signal of the optical sensor when the background portion of the striped test pattern image is read is Sj, Sc is corrected by Sj and Sk, and the result is taken as a corrected density signal. The correction means is provided.

According to a third aspect of the present invention, a plurality of color images are formed with a plurality of single color toners, these color images are transferred to a transfer material, and a color test pattern image is formed with the plurality of single color toners. In a color image forming apparatus in which the density of the color test pattern image is read by an optical sensor and the image density is controlled by the reading result of the optical sensor, a striped color test in which the color test pattern image is perpendicular to the traveling direction is performed. As a pattern image, when the background signal of the striped color test pattern image is read by the optical sensor, the output signal of the optical sensor is output according to the ratio of each color component of the striped color test pattern image. A means for correcting the output signal of the optical sensor is provided.

According to a fourth aspect of the present invention, in the color image forming apparatus according to the third aspect, the optical sensor is used when the background portion of the striped color test pattern image is read by the optical sensor in a predetermined state. The output signal Sk of the sensor is stored, and the output signal of the optical sensor when the color toner portion of the striped color test pattern image is read by the optical sensor during image formation is Sc, while the image formation is in progress. When the output signal of the optical sensor when the background portion of the striped color test pattern image is read by the optical sensor is Sj, correction is performed by Sj and Sk with respect to Sc, and the result is corrected. It is provided with a correction means for using the completed color density signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a printer unit according to an embodiment of the present invention. This embodiment is an embodiment of the invention described in claims 1 to 4, and is an example of a color image forming apparatus including a digital color copying machine. Printer unit 35 as an image forming unit of this embodiment (see FIG. 6)
Are image forming units 1Y, 1M for forming four color images of yellow (hereinafter, referred to as Y), magenta (hereinafter, referred to as M), cyan (hereinafter, referred to as C), and black (hereinafter, referred to as K). It has 1C and 1K.

These image forming units 1Y, 1M, 1
In C and 1K, the photoconductor drums 2Y, 2M, 2C and 2K as image bearing members are respectively connected to the motor 112 (see FIG. 7).
While being driven to rotate in the direction of the arrow by the reference), the surface thereof is a strip electrode (corona discharger) 3Y, 3 as charging means.
It is uniformly charged by M, 3C and 3K. This band electrode 3
Y, 3M, 3C, and 3K are charging high-voltage power sources 98 (see FIG. 7)
High voltage is applied by.

The exposure means composed of a writing unit including the semiconductor lasers 4Y, 4M, 4C, and 4K uses the semiconductor lasers 4Y and 4M according to image signals of respective colors of Y, M, C, and K sent from a host (not shown). 4C, 4
Modulates K to produce semiconductor lasers 4Y, 4M, 4C, 4K
Laser light from the polygon mirrors 5Y, 5M, 5C, 5
Reflect at K.

The polygon mirrors 5Y, 5M, 5C and 5K are rotationally driven by a motor 127 (see FIG. 7) to scan the laser light, and the laser light from the polygon mirrors 5Y, 5M, 5C and 5K is f / θ lens 6Y. , 6M, 6C, and 6K are subjected to optical correction such that the surfaces of the photoconductor drums 2Y, 2M, 2C, and 2K are scanned at a constant speed, and then the photoconductor drums 2Y, 2M, 2C, and 2K are irradiated and exposed to light. An electrostatic latent image is formed on the body drums 2Y, 2M, 2C, and 2K.

These photosensitive drums 2Y, 2M, 2C,
The electrostatic latent image on 2K is a two-component toner containing Y, M, C, and K color toners, respectively, by powder development using a magnetic blade method by developing devices 7Y, 7M, 7C, and 7K as developing means. A visible image (toner image) of each color of Y, M, C, and K is developed by the developer. Thereafter, the photosensitive drums 2Y, 2M, 2C, and 2K are irradiated with light from a discharge lamp (not shown) so that the charges of the electrostatic latent image are discharged, and the electrostatic latent image is erased.

Further, a transfer material 9 made of transfer paper is fed to a registration roller from a paper feeding device using a paper feeding cassette (not shown), and the registration rollers are the photosensitive drums 2Y, 2M.
The transfer paper 9 is sent to the transfer belt 8 in accordance with the visible images on 2C and 2K. The transfer paper 9 is conveyed by the transfer belt 8 and is transferred to the transfer belt 8 and the respective photosensitive drums 2Y, 2M, 2
It passes through each transfer position between C and 2K. At this time, transfer poles (corona discharger) 10Y, 10
M, 10C and 10K are transfer high voltage power sources 99 (see FIG. 7).
A high voltage is applied to the transfer paper 9 to form a full-color image by sequentially transferring the visible images on the photosensitive drums 2Y, 2M, 2C, and 2K onto the transfer paper 9. After forming the full-color image on the transfer paper 9, the full-color image is fixed by a fixing device (not shown) and discharged as a full-color copy to the outside. Here, the fixing device fixes the toner image on the transfer paper 9 by heating the transfer paper 9 with the fixing roller heated by the fixing heater and the pressure roller, and the surface temperature of the fixing roller is detected by the fixing thermistor. The fixing heater is controlled according to the result, and the surface temperature of the fixing roller is controlled to be constant.

FIGS. 6A and 6B show the circuit configuration of this embodiment and its image forming section. The main body control unit 40 as a control unit for controlling various controls for image formation processes a scanner unit 50 as an image reading unit for reading an image of a document and image information from the scanner unit 50. Image processing unit 6 as image processing means
0, a printer unit 35 for recording the image information processed by the image processing unit 60 on the transfer paper 9, and an operation unit 41 for setting copy conditions and displaying the setting contents. There is.

Here, the main body control section 40 controls the display of the operation section 41, key input processing, movement control of the scanner section 50 and the printer section 35, signal transmission according to the magnification change designation, and an image to the image processing section 60. Sending processing mode designating signals (image processing mode designating signals for color conversion, masking, trimming, mirroring, etc.), abnormal signals from modules in each part, operating status status signals (operating status such as standby, read, ready, busy, stop, etc.) Controls system by status signal).

The scanner unit 50 scans an original at a scanning speed that matches a scaling ratio designated by a start signal from the main body control unit 40, reads the original image with a reading device such as a CCD, and reads 8 bits of red (hereinafter referred to as red). Output as image data of each color of R), green (hereinafter referred to as G), and blue (hereinafter referred to as B). When outputting the image data, the scanner unit 50 outputs the horizontal synchronizing signal S-LSYNC and the pixel clock S-STRO output from the image processing unit 60.
The image data is sent to the image processing unit 60 in synchronization with each of BE and the vertical synchronization signal FGATE.

The image processing unit 60 performs γ conversion on the image data of each color of R, G and B sent from the scanner unit 50.
Image processing such as conversion, masking processing, UCR, etc. is further performed, and multi-value processing of pulse width modulation is performed, and each of Y, M, C, K is converted into image data of 1 BIT, and then the printer unit 3
Send to 5. The image processing unit 60 includes a main body control unit 40.
Γ conversion circuit 53 that performs γ conversion of the image data from the scanner unit 50 according to a command from the scanner unit 50, a masking processing circuit 54 that performs masking processing of the image data from the γ conversion circuit 53, and image data output from the masking processing circuit 54. UCR processing circuit 55 for performing UCR processing, this UCR
The image data of 8 BIT from the processing circuit 55 is converted into the semiconductor lasers 4Y, 4M in each writing unit according to the value.
A multi-valued processing circuit 56 for converting into image data of 4C and 4K lighting times, Y, M from the multi-valued processing circuit 56,
It is composed of a buffer memory or the like for outputting the image data of each color of C and K while being shifted by the intervals of the image forming units 1Y, 1M, 1C and 1K of the printer unit 35.

The printer unit 35 has a horizontal synchronizing signal P-L.
1 bit for each of Y, M, C, and K sent from the image processing unit 60 in synchronization with SYNC and pixel clock P-STROBE.
The semiconductor lasers 4Y, 4M, 4C, and 4K in each writing unit are turned on according to the image data of 1 to expose the surfaces of the photoconductor drums 2Y, 2M, 2C, and 2K, and the transfer paper 9 is printed by the color electrophotographic process as described above. Form a full color image on top.

In this way, a full-color image is formed on the transfer paper 9, but in this embodiment, a striped test pattern image of a halftone image described below is previously formed on a memory (not shown). For Y, M,
Image data of each color of C and K is stored, and this Y,
The semiconductor lasers 4Y and 4Y in the writing units are controlled by the image signals of the respective colors corresponding to the image data of the respective colors of M, C and K.
The semiconductor lasers 4Y,
Photosensitive drum 2 by laser light from 4M, 4C, 4K
A latent image of a striped test pattern of each color that is perpendicular to the traveling direction is created at the end portions on Y, 2M, 2C, and 2K, that is, the portion that is outside the area where a normal image is transferred to transfer paper 9. Then, the latent images of the striped test patterns of the respective colors are developed by the developers 7Y, 7M, 7C, and 7K with developers containing color toners of the respective colors of Y, M, C, and K, and Y,
The striped test pattern image of each color of M, C, K is used, and the test pattern image of each color is transferred to the transfer poles 10Y, 10M, 1
By 0C and 10K, the transfer is performed by shifting so as not to overlap the end portion of the transfer belt 8.

Here, the test pattern image of each color has a Y-shaped striped dark portion (a plurality of dark Y toner portions perpendicular to the traveling direction of the intermediate belt 8 and the background portion of the intermediate belt 8 as shown in FIG. 1). Horizontal stripes alternately arranged in the direction) 11YD, Y-shaped striped halftone portions (a plurality of halftone Y toner portions perpendicular to the traveling direction of the intermediate belt 8 and the background portion are alternately arranged in the traveling direction of the intermediate belt 8). Arranged horizontal stripes 11YN, Y stripe highlights (intermediate belt 8)
11YL striped test pattern image consisting of a plurality of highlight Y toner portions and a background portion that are arranged alternately in the traveling direction of the intermediate belt 8), and a diagram following this. Stripe dark portion of M (not horizontal stripes in which a plurality of dark M toner portions and background portions which are perpendicular to the traveling direction of the intermediate belt 8 are alternately arranged in the traveling direction of the intermediate belt 8) 11MD, Stripe of M Halftone portions (horizontal stripes in which a plurality of halftone M toner portions and background portions that are perpendicular to the traveling direction of the intermediate belt 8 are alternately arranged in the traveling direction of the intermediate belt 8) 11MN, M striped highlight portions ( A striped test pattern image of M consisting of 11 ML of horizontal stripes in which a plurality of highlight M toner portions and background portions which are perpendicular to the traveling direction of the intermediate belt 8 are alternately arranged in the traveling direction of the intermediate belt 8; Striped dark portions (horizontal stripes in which a plurality of dark C toner portions and background portions that are perpendicular to the traveling direction of the intermediate belt 8 are alternately arranged in the traveling direction of the intermediate belt 8) 11CD, C striped intermediate tone portions (Horizontal stripes in which a plurality of halftone C toner portions and background portions which are perpendicular to the traveling direction of the intermediate belt 8 are alternately arranged in the traveling direction of the intermediate belt 8) 11CN, striped highlight portions of C (intermediate belt 8)
Striped test pattern image of 11CL and a striped dark of K Portion (horizontal stripes in which a plurality of dark K toner portions and a background portion which are perpendicular to the traveling direction of the intermediate belt 8 are alternately arranged in the traveling direction of the intermediate belt 8) 11K
Striped halftone portions of D and K (horizontal stripes in which a plurality of halftone K toner portions and background portions that are perpendicular to the traveling direction of the intermediate belt 8 are alternately arranged in the traveling direction of the intermediate belt 8) 11K
N and K stripe-shaped highlight portions (horizontal stripes in which a plurality of highlight K toner portions and background portions that are perpendicular to the traveling direction of the intermediate belt 8 are alternately arranged in the traveling direction of the intermediate belt 8)
The striped test pattern image of K consisting of 11 KL is arranged in a line in the traveling direction at the end portion of the transfer belt 8 outside the normal image transfer area.

The transfer belt 8 is a motor 121 (see FIG. 7).
When the striped test pattern images 11YD to 11KL on the transfer belt 8 pass below the color density sensor 12 as an optical sensor, the color density sensor 12 causes the stripes on the transfer belt 8 to rotate. Of the test pattern images 11YD to 11KL are optically read.

Next, the flow of signals from the color density sensor 12 will be described with reference to FIG. As shown in FIG. 3, the color density sensor 12 includes three light emitting elements 14B, 14G, and 14R having peak emission wavelengths of 460 nm, 530 nm, and 600 nm, respectively, and at least 400.
The phototransistor 15 is provided that is sensitive to light having a wavelength of 700 nm.

Transistor array transistor 17
Any one of B, 17G, and 17R is driven by a signal from a microcomputer (microcomputer) 16 and 3
Any one of the light emitting elements 14B, 14G, and 14R is driven, and the light from the light emitting elements 14B, 14G, and 14R causes the striped test pattern images 11YD to 11 on the transfer belt 8.
By irradiating the reading position of KL, the striped test pattern images 11YD to 11KL on the transfer belt 8 are illuminated and the reflected light is received by the phototransistor 15, and the striped test pattern image 11YD on the transfer belt 8 is received.
A density of ~ 11KL is read at the reading position.

In this case, the phototransistor 15 has the striped test pattern images 11YD to 11K on the transfer belt 8.
The reflected light having a light quantity proportional to the density of L is received and a current proportional to the light quantity is output. The resistor 18 converts a change in output current of the phototransistor 15 into a change in voltage. The voltage amplifier 19 amplifies the voltage change of the resistor 18 so as to amplify the weak current change from the phototransistor 15 to a sufficiently large voltage change.

Since noise is likely to be introduced between the phototransistor 15 and the voltage amplifier 19, the phototransistor 15 is
It is necessary to arrange the voltage amplifier 19 and the voltage amplifier 19 as close to each other as possible.
The main body control unit 40 has the microcomputer 16 having an A / D input terminal mounted on its substrate, and after the output signal of the voltage amplifier 19 is input to the A / D input terminal of the microcomputer 16 and converted into a digital signal. It is processed.

FIGS. 4 and 5 are flow charts showing a processing flow for reading the striped test pattern images 11YD to 11KL transferred onto the transfer belt 8 by the color density sensor 12 and correcting the color density. It is programmed in a memory (not shown) in the microcomputer 16 on the main body control unit 40. The main body control unit 40 sends a clock signal from a reference pulse generator (not shown) synchronized with the drum drive motor 112 to the photosensitive drums 2Y, 2M, 2C, and
By counting from the start of electrostatic latent image formation on 2K,
The timing at which the striped test pattern images 11YD to 11KL on the transfer belt 8 arrive under the color density sensor 12 is determined, and the signal from the color density sensor 12 is read.

Striped test pattern images 11YD to 11K
The relationship between the L color and the emission colors of the light emitting elements 14B, 14G, and 14R is the most striped test pattern image 11YD to 11KL.
The complementary color relationship is set so that the density can be largely obtained as a change in the reflected light amount of the striped test pattern images 11YD to 11KL. That is, the main body control unit 40 sets 400 when the Y striped test pattern images 11YD, 11YN, and 11YL pass through the reading position below the color density sensor 12.
the other light emitting elements 14G and 14R by turning on only the light emitting element 14B having a peak emission wavelength between nm and 500 nm.
Is turned off, and the output signal of the color density sensor 12 is read from the voltage amplifier 19. This color density sensor 12
Output signal voltage is Y stripe test pattern image 11Y
Since the light amount of the reflected light from D, 11YN, and 11YL changes periodically in magnitude, it corresponds to the toner portion and the background portion of the Y stripe test pattern images 11YD, 11YN, and 11YL as shown in FIG. And becomes a waveform that periodically changes in magnitude.

The error in the density measurement of the color density sensor 12 that picks up the reflected light from the striped test pattern image is as follows. The difference in the measurement distances of the color density sensor 12 ,. Temperature difference during measurement ,.
Difference in charging state when forming a striped test pattern image ,. Difference in development state when forming a striped test pattern image ,. Difference in laser light amount (difference in exposure state) when forming a striped test pattern image ,. It is caused by a difference in transfer condition when forming a striped test pattern image.

If the distance between the color density sensor 12 and the striped test pattern image at the reading position becomes long due to, for example, decentering of the rotation axis, the color density sensor 12 produces a striped test pattern image as shown by the dotted line in FIG. The output signal voltage of the color density sensor 12 becomes small both when the toner portion is read and when the background portion of the striped test pattern image is read. If the normal distance from the color density sensor 12 to the striped test pattern image at the reading position is d
If the output signal voltage of the color density sensor 12 is 100 when the distance from the color density sensor 12 to the striped test pattern image at the reading position is d, then the color density sensor 12 to the striped test pattern image at the reading position When the distance d of the color density sensor 12 changes to d + Δd due to the eccentricity of the rotating shaft, the relative output signal voltage of the color density sensor 12 is approximately inversely proportional to the square of the measured distance.
/ (D + Δd)} ² .

Since the test pattern image has a striped shape, the color density sensor 12 is used when the toner portion of the striped test pattern image is read and when the background portion immediately adjacent to the toner portion is read. Since the measured distances of 12 are almost equal, Δd is very small.
Further, regarding other errors in the density measurement of the color density sensor 12 with respect to the striped test pattern image, the toner portion for the density measurement of the striped test pattern image is read and the background for correcting the read color density signal is obtained. Since there is almost no difference in time from reading the part, the conditions are almost the same, and the measurement error is small.

Although there are long-term changes such as deterioration of the photoconductor drums 2Y, 2M, 2C and 2K, changes in room temperature, a decrease in the amount of illumination light of the color density sensor 12, and the like, the main body control unit 40 is, for example, a factory As shown in FIG. 4, the light emitting element 14B is turned on to display the Y-shaped striped test pattern images 11YD and 1YD on the transfer belt 8 in a shipping state or immediately after maintenance by a service engineer.
When the background portions of 1YN and 11YL reach the reading position, the output signal voltage Skb of the color density sensor 12 for the background portion is fetched as a reference background signal and stored in the memory, and the light emitting element 14B is turned off.

Then, the main body control section 40 then turns on the light emitting element 14B as shown in FIG. 5 during the normal image formation to make the Y striped test pattern images 11YD, 11YN and 11YL on the transfer belt 8. When the background portion reaches the reading position, the output signal voltage Sjb of the color density sensor 12 for the background portion is read, and the Y striped test pattern images 11YD and 11Y on the transfer belt 8 are read.
When the toner portion of N and 11YL reaches the reading position, the output signal voltage Scb of the color density sensor 12 for the toner portion is read, Scb × (Sjb / Skb) is calculated, and the B color density signal Scb is corrected. Scb * (Sjb / Skb) is stored as the B color density signal.

Further, the main body control section 40 turns on the light emitting element 14G as shown in FIG.
When the background portion of 1 MN or 11 ML reaches the reading position, the output signal voltage Skg of the color density sensor 12 for the background portion is fetched as a reference background signal, stored in the memory, and the light emitting element 14G is turned off.

Then, the main body control section 40 turns on the light emitting element 14G as shown in FIG. 5 during the normal image formation thereafter, so that the M striped test pattern images 11MD, 11MN, 11ML on the transfer belt 8 are formed. When the background portion reaches the reading position, the output signal voltage Sjg of the color density sensor 12 for the background portion is read, and the M striped test pattern images 11MD and 11M on the transfer belt 8 are read.
When the toner portion of N, 11 ML reaches the reading position, the output signal voltage Scg of the color density sensor 12 for the toner portion is read, Scg × (Sjg / Skg) is calculated, and the G color density signal Scg is corrected. Scg × (Sjg / Skg) is stored as the G color density signal.

Further, the main body control section 40 turns on the light emitting element 14R as shown in FIG.
When the background portions of 1CN and 11CL reach the reading position, the output signal voltage Skr of the color density sensor 12 for the background portion is fetched as a reference background signal and stored in the memory, and the light emitting element 14R is turned off.

Then, the main body controller 40 turns on the light emitting element 14R as shown in FIG. 5 during the normal image formation thereafter, and the stripe test pattern images 11CD, 11CN and 11CL of C on the transfer belt 8 are displayed. When the background portion reaches the reading position, the output signal voltage Sjr of the color density sensor 12 for the background portion is read, and the striped test pattern images 11CD and 11C of C on the transfer belt 8 are read.
When the toner portion of N and 11CL reaches the reading position, the output signal voltage Scr of the color density sensor 12 for the toner portion is read and Scr × (Sjr / Skr) is calculated to correct the R color density signal Scr. Scr × (Sjr / Skr) is stored as the R color density signal.

Further, the main body controller 40 turns on the light emitting element 14G as shown in FIG.
When the background portions of 11KN and 11KL reach the reading position, the output signal voltage Skk of the color density sensor 12 for the background portion is fetched as a reference background signal and stored in the memory, and the light emitting element 14G is turned off.

Then, the main body control section 40 turns on the light emitting element 14G as shown in FIG. 5 during the normal image formation thereafter, and the striped test pattern images 11KD, 11KN and 11KL of K on the transfer belt 8 are turned on. When the background portion reaches the reading position, the output signal voltage Sjk of the color density sensor 12 for the background portion is read, and the K striped test pattern images 11KD and 11K on the transfer belt 8 are read.
When the toner portion of N and 11 KL reaches the reading position, the output signal voltage Sck of the color density sensor 12 for the toner portion is read, Sck × (Sjk / Skk) is calculated, and the K color density signal Sck is corrected. Sck × (Sjk / Skk) is stored as the K color density signal.

The main body controller 40 sets the image forming conditions for each color by the corrected B color density signal, the corrected G color density signal, the corrected R color density signal, and the corrected K color density signal stored as described above. Control to control the image density. If the area of the background portion or toner portion of the striped test pattern images 11YD to 11KL is reduced, the density reading timing becomes difficult, but for example, the density of the background portion of the striped test pattern images 11YD to 11KL is set to the toner portion. If the output voltage of the color density sensor 12 is set to be low relative to the density and the output signal voltage of the color density sensor 12 is increased relative to the background portion of low density (the amount of reflected light is large), the striped test pattern images 11YD to 11KL are colored. Color density sensor 12 when it comes near the density sensor 12
When the density is continuously read by, the output signal voltage of the color density sensor 12 repeats peaks (background areas) and valleys (toner areas), so that the peaks and valleys of the output signal voltage of the color density sensor 12 are accurate. No read timing required.

Therefore, when the main body controller 40 reads the output signal voltage of the color density sensor 12 for the background portion and the toner portion of the striped test pattern image of each color as described above, the striped test pattern of each color is read. For each image, the density of the background portion is measured by averaging a plurality of small values within the predetermined range of the mountain portion of the output signal voltage of the color density sensor 12, and the output of the color density sensor 12 is measured. The density of the toner portion is measured by averaging a plurality of values in the valley portion of the signal voltage, which are in a small order within a predetermined range, and the density signal of each color is corrected as described above. By such averaging, the density can be read relatively accurately with respect to dust and partial loss of the image.

Further, the striped test pattern image 11YD-
A circuit in which the magnitude relationship between the density of the background portion of 11 KL and the density of the toner portion is opposite to the above, or when the output signal voltage of the color density sensor 12 becomes smaller for the background portion of low density (large amount of reflected light). In the case of the configuration, the main body control unit 40 sets a plurality of values in descending order within a predetermined range in the peak portion of the output signal voltage of the color density sensor 12 for the striped test pattern image of each color. The density of the toner portion is measured by averaging, and the density of the background portion is determined by averaging a plurality of values in the valley of the output signal voltage of the color density sensor 12 in descending order. It will be measured.

Also, a K-shaped striped test pattern image 11K
When reading the densities of the background portion and the toner portion of D, 11KN, and 11KL, the striped test pattern image 11 of K is used.
KD, 11KN and 11KL are three light emitting elements 14B, 1
It is possible to read the density of the background portion and the toner portion of the striped test pattern images 11KD, 11KN, and 11KL of K regardless of whether it is illuminated by 4G or 14R.
Striped test pattern images 11KD, 11KN, 11K
L may be illuminated with white light by simultaneous lighting of the three light emitting elements 14B, 14G, and 14R.

However, the three light emitting elements 14B, 14G, 1
When 4R are turned on at the same time, the amount of illumination light is too large as compared with the case of illuminating each of the other Y, M, and C striped test pattern images. Therefore, in this embodiment, three light emitting elements 14B,
One of 14G and 14R, for example, the light emitting element 14G
Only one is turned on and the striped test pattern image 11 of K
The densities of the background portion and the toner portion of KD, 11KN, and 11KL are read.

In this embodiment, one phototransistor 15 receives the reflected light from the striped test pattern image. Therefore, if the light emission amounts of the light emitting elements 14B, 14G and 14R are not balanced, the voltage amplifier is used. Since the use area of 19 extends out a linear area, a current close to the maximum rating is applied to the light emitting element 14B that emits a smaller amount of light than other light emitting elements to generate a K-tone test pattern image of a halftone density. The amplification degree of the voltage amplifier 19 is adjusted so that the output signal voltage of the voltage amplifier 19 at the time of reading the concentration is approximately equal to the power source voltage (approximately equal to the power source voltage- (power source voltage-1V)).

In this embodiment, the halftone density striped test pattern images 11YD to 11KL are used.
This is because the color density sensor 12 changes the image density relatively.
This is because the output signal voltage changes significantly.
Further, the background portions of the striped test pattern images 11YD to 11KL are achromatic gray, but when the light emitting elements 14B, 14G and 14R are switched and turned on, the output signal voltage of the color density sensor 12 becomes almost the same value. This is because it is easy to adjust the light amount in the initial stage, and the density of the background portion of the striped test pattern images 11YD to 11KL is brought close to the density of the toner portion so that the vicinity of the density to be measured most accurately can be read with high resolution. The background portion of the striped test pattern images 11YD to 11KL does not necessarily have to be an achromatic gray, and the same color as the toner portion and the same density as the toner portion are read in order to read in the vicinity of the density to be measured most accurately with high resolution. It can be the bare skin.

FIG. 7 shows details of the printer section 35 and the main body control section 40. The printer unit 35 is positioned as a slave with respect to the main body control unit 40. The main body control unit 40 is mainly configured by the microcomputer 16 including a CPU, a ROM, a RAM, an input / output interface circuit, and the like.

On the input side of the microcomputer 16, a paper discharge sensor 91 for detecting the discharge of the transfer paper to the outside, and a paper end sensor 9 for detecting the presence or absence of the transfer paper in the paper feed cassette.
2, a registration sensor 93 for controlling the paper feeding to the registration rollers, a cassette size sensor 94 for detecting the size of the paper feeding cassette, and the developing devices 7Y, 7M, 7
Toner sensors 95Y to 95K for detecting the toner concentration of the developer in C and 7K, and a thermistor 96 for detecting the surface temperature of the fixing roller heated by the fixing heater 96H are respectively connected, and these detection signals are input to the microcomputer 16. To be done.

On the output side of the microcomputer 16, a charging high-voltage power source 98, a transfer high-voltage power source 99, a belt neutralization high-voltage power source 110 for applying a high voltage to a static eliminator 129 for removing the electrostatic charge of the transfer belt 8, and developing devices 7Y, 7M. , 7C, 7K developing bias high voltage power source 111 for applying a developing bias voltage to the developing rollers, and developing devices 7Y, 7M, 7C, 7K for Y, M, C,
A toner replenishing driver 130 for driving a toner replenishing unit for replenishing each of the K toners, and a fixing heater 96.
A heater control unit 115 that controls energization to H, a sheet feeding motor 117 that drives a sheet feeding device, and a pulse motor driver 119 that drives a registration motor 118 that drives a registration roller, various motors (photosensitive drum 2Y, 2D, 2C, 2K driving the photosensitive drum motor 112, the transfer belt 8 driving the transfer belt motor 121, the developing device 7Y, 7M, 7
A motor driver 12 for driving a developing roller motor 122 for driving the C and 7K developing rollers, and a fixing roller motor 123) for driving the fixing roller.
4. The video control unit 128 of the printer unit 35 is connected, and these are controlled by the microcomputer 16.

The video control unit 128 uses the polygon mirror 5
A polygon motor driver 12 for driving a polygon motor 127 which serves as a rotation driving source for Y, 5M, 5C and 5K.
6. A laser driver 125 for driving the semiconductor lasers 4Y, 4M, 4C, 4K is connected, and the semiconductor lasers 4Y, 4M, 4C, 4K are driven by the laser driver 125 according to the image data of each color from the image processing unit 60. At the same time, it controls the polygon motor driver 126. Further, in this embodiment, an operation unit 41 for inputting and displaying the number of copies, transfer paper size, etc., and a RAM backed up by a battery for storing various correction amounts.
have.

As described above, this embodiment is characterized by claim 1.
1 is an example embodiment of the described invention, in which an image is formed with toner and transferred onto a transfer paper as a transfer material, a test pattern image is formed with the toner, and the density of the test pattern image is determined as a color as an optical sensor. In the image forming apparatus that reads the image with the density sensor 12 and controls the image density according to the reading result of the optical sensor 12, the test pattern image is the striped test pattern images 11YD to 11KL that are perpendicular to the traveling direction. The toner portion of the test pattern image for which the density should be measured and the background portion that serves as a reference for correcting the density are alternately read by the optical sensor, and the density of these toner portion and the background portion can be measured very temporally. It is possible to read in a state close to, and the difference in the measurement distance at the time of reading between the toner part and the background part, Degrees difference, the difference in the charged state, the difference between the development status, the difference in the exposure condition, it is possible to minimize the differentially transfer conditions, it is possible to perform high-precision correction.

Further, this embodiment is an embodiment of the invention according to claim 2, and in the image forming apparatus according to claim 1, a striped test pattern image is obtained by the optical sensor 12 in a predetermined state in advance. Output signal Sk of the optical sensor 12 when the background portion of 11YD to 11KL is read
(Skb, Skg, Skr, Skk) is stored, and the output signal of the optical sensor 12 when the toner portion of the striped test pattern images 11YD to 11KL is read by the optical sensor 12 during image formation is Sc ( Scb, Scg, Sc
r, Sck), the output signal of the optical sensor 12 when the background portion of the striped test pattern images 11YD to 11KL is read by the optical sensor 12 during the image formation is Sj.
When (Sjb, Sjg, Sjr, Sjk), Sj for Sc
Since the main body control unit 40 is provided as a correcting unit that corrects the corrected density signal and the corrected density signal by using Sk and Sk, the difference in the measured distance between the toner portion and the background portion of the striped test pattern image at the time of reading is provided. , Temperature difference, charge state difference, development state difference, exposure state difference, transfer condition difference, etc. can be minimized, and against long-term changes such as reduction of illumination light amount of optical sensor. More accurate correction can be performed, and highly accurate correction can be performed.

Further, this embodiment is an embodiment of the invention described in claim 3, wherein a plurality of color images are formed by a plurality of monochromatic color toners Y, M, C and K, and these color images are formed. Is transferred to a transfer paper 9 as a transfer material, a color test pattern image is formed with a plurality of monochromatic color toners, and the density of the color test pattern image is read by a color density sensor 12 as an optical sensor. In the color image forming apparatus which controls the image density according to the reading result of 12, the color test pattern images are striped color test pattern images 11YD to 11KL which are perpendicular to the traveling direction, and the striped color test pattern images 11YD to 11KL are formed. The output signal of the optical sensor 12 output according to the ratio of each color component of
Striped color test pattern image 1 with optical sensor 12
Since the main body control unit 40 is provided as means for correcting with the output signal of the optical sensor 12 when the background portion of 1YD to 11KL is read, the toner portion to be subjected to density measurement in the striped color test pattern image and its correction. It is possible to read the density of the toner part and the background part in a very close temporal manner by alternately reading the background part that is the reference for performing by the optical sensor,
It is possible to minimize the difference in measured distance between the toner portion and the background portion during reading, temperature difference, charge state difference, development state difference, exposure state difference, transfer condition difference, etc. It is possible to make various corrections.

Further, this embodiment is an embodiment of the invention according to claim 4, and in the color image forming apparatus according to claim 3, the optical sensor 1 in a predetermined state in advance.
2 striped color test pattern images 11YD-11
The output signal Sk (Skb, Skg, Skr, Skk) of the optical sensor 12 when the background portion of KL is read is stored, and the optical sensor 12 causes the striped color test pattern images 11YD to 11KL during image formation. The output signal of the optical sensor 12 at the time of reading the color toner portion of Sc is Sc (Scb, Scg, Scr, Sck), and the background portion of the striped color test pattern images 11YD to 11KL is formed by the optical sensor 12 during the image formation. The output signal of the optical sensor 12 when read is Sj (Sjb, Sjg, Sjr, Sj
k), Sc is corrected by Sj and Sk, and the result is used as a corrected color density signal. Since the main body control unit 40 is provided as a correction unit, the toner of the striped color test pattern image is provided. In addition to minimizing the measurement distance difference, temperature difference, charge state difference, development state difference, exposure state difference, transfer condition difference, etc. between the area and the background area when reading, an optical sensor It is possible to perform more accurate correction even for a long-term change such as a decrease in the illumination light amount, and it is possible to perform highly accurate correction.

The invention described in claims 1 to 4 is not limited to the above-mentioned embodiment, and for example, a plurality of color images are formed by a plurality of monochromatic color toners and these color images are transferred to a transfer material. It can be applied to a wet or dry electrostatic color image forming apparatus such as an analog color copying machine, a color printer or a color facsimile.

Further, in the above embodiment, the main body control section 40 illuminates the striped color test pattern image of one color while switching the light emitting elements 14B, 14G and 14R through the transistors 17B, 17G and 17R. You may This is effective when it is desired to detect a color mixture. For example, when M is mixed in a Y-color striped color test pattern image, an optical sensor is used even if the Y-band color test pattern image is illuminated with B light. This is because there is almost no change in the output signal of 12 and the change in the output signal of the optical sensor 12 is the largest when the Y-color striped color test pattern image is illuminated with G light.

However, when there is no fear of color mixture, for example, in the case of a thermal transfer type printer, the light emitting elements 14B, 14G, 14 are applied to the striped color test pattern image of one color.
It is not necessary to illuminate while switching R. That is, the Y striped color test pattern image is illuminated with B light, the M striped color test pattern image is illuminated with G light, the C striped color test pattern image is illuminated with R light, and the K striped. The color test pattern image may be illuminated with G light.

The invention described in claims 1 and 2 can be applied to an image forming apparatus including a digital copying machine for copying a single color. In this case, in the digital copying machine, for example, in the digital color copying machine of the above-described embodiment, the scanner unit reads a monochromatic image of a document, the image processing unit processes the image signal, and the printer unit sets the image forming unit 1
A single color image is formed using only one piece.

Further, the test pattern image is only for one color, and the main body control section reads the striped test pattern image for one color transferred onto the transfer belt 8 by the optical sensor and is the same as the above embodiment. The density signal is corrected to, that is, the output signal Sk of the optical sensor when the background portion of the striped test pattern image is read by the optical sensor in advance in a mechanically good state is stored, and the image is formed during image formation. The output signal of the optical sensor when the toner portion of the striped test pattern image is read by the optical sensor is S
c. When the output signal of the optical sensor when the background portion of the striped test pattern image is read by the optical sensor during image formation is Sj, the Sc is corrected by Sj and Sk. As the corrected density signal, the image density is controlled by controlling the image forming condition by the corrected density signal.

The invention described in claims 1 and 2 can also be applied to a wet or dry electrostatic image forming apparatus such as a printer or a facsimile which forms an image with toner and transfers it to a transfer material. .

[0062]

As described above, according to the first aspect of the invention, an image is formed with toner and transferred to a transfer material, a test pattern image is formed with the toner, and the density of the test pattern image is determined optically. In the image forming apparatus that reads the image with the sensor and controls the image density based on the reading result of the optical sensor, the test pattern image is a striped test pattern image perpendicular to the traveling direction. An optical sensor alternately reads the toner portion to be measured and the background portion that serves as a reference for correcting the toner portion, so that the densities of these toner portion and background portion can be read very close in time. It is possible to minimize the difference between the measurement distance and the temperature difference when reading between the toner portion and the background portion, and perform highly accurate correction. It can be carried out.

According to the second aspect of the invention, in the image forming apparatus of the first aspect, the optical sensor is used when the background portion of the striped test pattern image is read by the optical sensor in a predetermined state. Sensor output signal Sk
And the output signal of the optical sensor is Sc when the toner portion of the striped test pattern image is read by the optical sensor during image formation, and the stripe is output by the optical sensor during image formation. When the output signal of the optical sensor at the time of reading the background portion of the linear test pattern image is Sj, correction is performed by Sj and Sk with respect to Sc, and the result is used as a corrected density signal. As a result, it is possible to minimize the difference in the measurement distance between the toner part and the background part of the striped test pattern image when reading, the temperature difference, etc. It is possible to perform more accurate correction even for changes, and it is possible to perform highly accurate correction.

According to the third aspect of the invention, a plurality of color images are formed with a plurality of single color toners, these color images are transferred to a transfer material, and a color test pattern image is formed with the plurality of single color toners. In a color image forming apparatus in which the density of the color test pattern image is read by an optical sensor and the image density is controlled by the reading result of the optical sensor, the color test pattern image is striped at right angles to the traveling direction. A color test pattern image, and the output signal of the optical sensor output according to the ratio of each color component of the striped color test pattern image is read by the optical sensor in the background portion of the striped color test pattern image. Since a means for correcting the output signal of the optical sensor at the time of An optical sensor alternately reads the toner portion of the image for which the density should be measured and the background portion that serves as a reference for correcting it, and the densities of the toner portion and the background portion are very close in time. It is possible to read in the state, and it is possible to minimize the difference in measurement distance between the toner portion and the background portion during reading, the temperature difference, and the like, and it is possible to perform highly accurate correction.

According to a fourth aspect of the invention, in the color image forming apparatus according to the third aspect, the optical sensor is used to read the background portion of the striped color test pattern image in a predetermined state. The output signal Sk of the optical sensor is stored, and the output signal of the optical sensor when the color toner portion of the striped color test pattern image is read by the optical sensor during image formation is Sc, and the image formation is performed. When the output signal of the optical sensor when the background portion of the striped color test pattern image is read by the optical sensor on the way is Sj, correction is performed on Sc by Sj and Sk, and the result is obtained. Since the correction means for making the corrected color density signal is provided,
In addition to minimizing the difference in measurement distance and temperature difference between the toner portion and the background portion of the striped color test pattern image when reading, it also prevents long-term changes such as reduction of the illumination light amount of the optical sensor. However, more accurate correction can be performed, and highly accurate correction can be performed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an outline of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a part of the embodiment.

FIG. 3 is a characteristic diagram showing a relationship between an emission wavelength and a relative luminous intensity of the color density sensor in the embodiment.

FIG. 4 is a flowchart showing a part of a processing flow of the main body control section in the embodiment.

FIG. 5 is a flowchart showing another part of the processing flow of the main body control unit in the embodiment.

FIG. 6 is a block diagram showing the embodiment example and an image processing unit thereof.

FIG. 7 is a block diagram showing a printer unit and a main body control unit of the embodiment.

FIG. 8 is a waveform diagram showing an output signal waveform of the photo sensor according to the embodiment.

FIG. 9 is a waveform diagram showing an output signal waveform of the photo sensor at the time of normality and at the time of eccentricity in the embodiment example.

[Explanation of symbols]

1Y, 1M, 1C, 1K Image forming unit 8 Transfer belt 11YD, 11YN, 11YL Striped test pattern image 12 Color density sensor 35 Printer section 40 Main body control section 50 Scanner section 60 Image processing section

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location G03G 15/01 B41J 3/00 B G06T 5/00 G06F 15/68 310J H04N 1/46 H04N 1/46 Z C3 ,Four

Claims (4)

[Claims] 1. An image is formed with toner and transferred to a transfer material,
An image forming apparatus that forms a test pattern image with toner, reads the density of the test pattern image with an optical sensor, and controls the image density according to the reading result of the optical sensor, An image forming apparatus having a right-angled striped test pattern image. 2. The image forming apparatus according to claim 1, wherein an output signal Sk of the optical sensor when the background portion of the striped test pattern image is read by the optical sensor in a predetermined state is stored in advance. The output signal of the optical sensor when the toner portion of the striped test pattern image is read by the optical sensor during image formation is Sc, and the striped test pattern is output by the optical sensor during image formation. When the output signal of the optical sensor when the background portion of the image is read is Sj,
An image forming apparatus comprising: a correction unit that corrects Sc with Sj and Sk, and uses the result as a corrected density signal. 3. A plurality of monochromatic color toners are used to form a plurality of color images, the color images are transferred to a transfer material, and a plurality of monochromatic color toners are used to form a color test pattern image. In a color image forming apparatus in which the density is read by an optical sensor and the image density is controlled by the reading result of the optical sensor,
The color test pattern image is a striped color test pattern image orthogonal to the traveling direction, and the output signal of the optical sensor output according to the ratio of each color component of the striped color test pattern image is the optical signal. Image forming apparatus comprising means for correcting the background portion of the striped color test pattern image with an output signal of the optical sensor when a static sensor is read. 4. The color image forming apparatus according to claim 3, wherein an output signal Sk of the optical sensor when the background portion of the striped color test pattern image is read by the optical sensor in a predetermined state in advance. Remember
Sc is an output signal of the optical sensor when the color toner portion of the striped color test pattern image is read by the optical sensor during image formation, and the striped color test pattern is printed by the optical sensor during image formation. When the output signal of the optical sensor when the background portion of the image is read is Sj, Sc is corrected by Sj and Sk, and the result is used as a corrected color density signal. A color image forming apparatus characterized by the above.