JP2001290332A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the misregistration of a black image forming part for a multicolor image forming device. SOLUTION: The image forming device is provided with plural image forming parts, a test pattern carrier for carrying plural test patterns formed by plural image forming parts, and a test pattern reading means for optically reading plural test patterns carried by the test pattern carriers and for detecting the misregistration by the test pattern reading means and correcting the registration. The test pattern 22 (TK) which is formed with developer having spectral reflection characteristics which cannot be read by the test pattern reader and a test pattern 22 (TM) which is formed by developer with spectral reflection characteristics and which can be read by the test pattern reader are formed in the overlaid state, and then, the test patterns in the overlaid state are read by the test pattern reader, then the misregistration amount is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine and a laser beam printer utilizing an electrophotographic technique.

[0002]

2. Description of the Related Art FIG. 1 is a sectional view showing a conventional example of this type of image forming apparatus. Color separation of color originals for each pixel,
It comprises a pixel reading section for digitally reading as an electric signal, and a laser beam printer section (LBP) for obtaining a full-color print by an electrophotographic method using an image signal converted into an electric signal.

[0003] The configuration and operation will be described below.

In the image reading section, a color original 31 is irradiated by an original exposure lamp (illumination lamp) 32, and a color reflected light image reflected from the color original 31 is formed on a color image sensor 33. A color image signal that has been color-separated for each pixel by a color image sensor 33 (CCD color line sensor) is
The signal is processed and input to the image processing circuit 26.

[0005] In the image processing circuit 26, after the input signal is digitized and color correction is performed by digital image processing of the color signal, the digital image signal is converted into image forming units PM, PC, P.
Send to Y, PK.

The image forming unit has an image forming unit for performing a latent image process and a developing process for each of magenta (M), cyan (C), yellow (Y), and black (BK). The image visualized in step is multiplex-transferred to a recording medium.

In this method, since the electrophotographic processes can be overlapped with each other, the copying speed can be increased, and is called a 4D method.

The optical scanning device 3 includes laser units 36M and 36 each including a laser light source, an inclination correcting lens, and an fθ lens.
The signals modulated from C, 36Y and 36K are converted into a rotating polygon mirror 3
7, for example, the reflection mirror 45M for magenta color,
The light is reflected at 46M and 47M to form an image on the photosensitive drum 1M.
The same applies to other colors.

The photosensitive drum 1 is rotating clockwise.
An electrostatic latent image is formed on the photosensitive drum 1 uniformly charged by the primary charger 2M by the exposure. This latent image is made a visible image by the developing unit 4M.

The transfer unit includes a transport belt 6 for holding and transporting a transfer material of a recording medium, and transfer chargers 7M, 7C, 7C.
Y, 7K.

The respective image forming units PM, PC, PY,
The images formed by PK are transferred to transfer chargers 7M, 7C, 7
Multiple transfer is performed on the transfer material at Y and 7K.

The transfer material supporting the unfixed image transferred by the conveyor belt 6 and transferred in the multiplex image forming section is fixed by the fixing device.

As the transfer material fed from the paper feed cassette 61 advances, the leading end of the transfer material is
, The image signals of the respective color components already stored in the memory device are read out at an appropriate timing by a timing control circuit (not shown) in synchronization with the leading edge signal of the transfer material. Input to the device.

In such an apparatus, since an image of each color component of magenta, cyan, yellow, and black is formed for each image forming unit, it is an important technique how to accurately overlap the images of each image forming unit. In a high-quality full-color copying machine, the position accuracy of the superposition of images of each color component needs to be 100 μm or less. If the amount of image shift is larger than this, color shift due to color overlap,
Color unevenness occurs. It is very difficult to adjust each component for image formation with such accuracy. Even if the adjustment can be made, for example, misalignment due to thermal expansion of each component due to temperature fluctuation, misalignment due to reproducibility of mechanical positional accuracy after jam processing, scratches on the photosensitive drum, and defects in the developing device Due to the replacement of components, etc., the adjusted position is immediately shifted, and once shifted, it is practically impossible for the user to adjust it.

In order to make such adjustments automatically,
For example, as shown in FIG. 2, a test pattern 22 for registering each color component yellow, magenta, and cyan is printed on the conveyor belt 6 at regular intervals, and the test pattern 22 is formed of two parts, for example, a CCD at the back and front sides. The reading devices 12-1 and 12-2 detect the amount of deviation in the main scanning direction and the sub-scanning direction in each image forming unit, and detect the amount of deviation in the sub-scanning direction and the main scanning direction by the correction means. Has been proposed that automatically corrects.

FIG. 3 is a timing chart showing the timing of forming registration marks in this type of image forming apparatus.

As shown in FIG. 3, in the sub-scanning direction, the number of lines is counted by a counter circuit (not shown) from the rise of an output signal ITOP from an ITOP sensor 67 for detecting the leading end of the transfer material.
After counting tm time, after counting tc time for cyan, counting for ty time for yellow, and counting for tk time for black, the output signal M
By transmitting the TOP, CTOP, YTOP, and KTOP signals, the above-described test pattern 22 is read by the reading device 1.
The counts tm, tc, ty, and kk may be determined based on the timings detected in 2-1 and 12-2.

FIG. 4 is a timing chart showing test pattern formation timing in this type of image forming apparatus.

Each signal MBD, CBD, YBD, KBD is a detection signal of a laser beam for forming a magenta, cyan, yellow, and black latent image, and each signal determines a main scanning position of an image at each position. This is a reference signal for performing Each image has a laser beam detection signal MBD,
Image count x from CBD, YBD, KBD respectively
m, xc, xy, and xk, and are determined by the enable signals MEN, CEN, YEN, and KEN. These are also determined based on the positions detected by the readers 12-1 and 12-2. What is necessary is just to set a value appropriately.

In the automatic tilt correction, for example, magenta is automatically corrected by tilting the reflection mirrors 45M, 46M, 47M by an actuator (not shown).

[0021]

By reading the test pattern 22 thus transferred onto the transport belt by the reading sensor 12a such as a CCD, it is possible to detect a registration deviation. In order to detect the reflected light from the toner pattern on the belt, it is necessary to have a reflection area (sensitivity) to the irradiation light in the spectral reflection characteristics of the toner. This condition is satisfied for the magenta, cyan, and yellow toners. However, in the case of a black toner in which an appropriate amount of magenta, cyan, and yellow colorants are mixed as a colorant, there is no problem.
Black produced by mixing various kinds of coloring agents makes the production method complicated, so that it is difficult to control the color and the production cost increases. For this reason, if a carbon-based colorant used in a black-and-white copying machine is used as a normal colorant, there is no reflection region in any wavelength region, and the pattern on the transport belt cannot be identified.

FIGS. 5, 6, and 7 show the reflectance of magenta, cyan, yellow, and black toners with respect to the irradiation light wavelength, that is, the spectral reflection characteristics.

That is, the yellow (Y), magenta (M), and cyan (C) toners shown in FIG. 5 are 400 to 500 nm, 500 to 600 nm, and 600 to 7 respectively.
Since it absorbs light having a wavelength of 00 nm, conversely, it has a reflection region at other wavelengths. The black BK in which these three types of colorants are mixed as shown in FIG. 6 has a reflection region in the infrared region. In a system using such a toner, the mark may be read by irregularly reflected infrared light from the surface of the toner particles.

However, when carbon is used as a colorant for black BK as shown in FIG. 7, there is no reflection in all wavelength regions.

As a result, there is a problem that the registration deviation of the black image forming portion PK cannot be detected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a resist correction test pattern using a toner of a color that makes reflected light undetectable on a spectral characteristic can be detected on a transport belt by a spectral characteristic. It is an object of the present invention to provide an image recording apparatus which detects a registration deviation by superimposing and transferring toner on a resist correction test pattern and reading the amount of overlap with a sensor.

[0027]

The problem to be solved by the present invention is solved by the following means.

According to a first aspect of the present invention, there are provided a plurality of image forming units, a test pattern carrier capable of carrying a plurality of test patterns formed by the plurality of image forming units, and a plurality of test pattern carriers on the test pattern carrier. A test pattern reading means for optically reading the test pattern, wherein the test pattern reading means detects the amount of registration deviation and corrects the registration. A test pattern formed of a developer having
Forming a test pattern formed of a developer having a spectral reflection characteristic which can be read by the test pattern reading means, and reading the superposed test pattern by the test pattern reading means to detect a registration shift amount. The image forming apparatus is a feature.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

The first to third embodiments correspond to the problem and correspond to the problem. A resist correction test pattern of a color toner which can be detected on a transport belt by a resist correction test pattern using a toner of a color in which reflected light cannot be detected on a spectral characteristic. It is an object of the present invention to obtain an image forming apparatus that detects a registration deviation by transferring a pattern on a pattern and reading the overlapping amount with a sensor.

Embodiment 1 FIG. 8 is a cross-sectional view for explaining a main configuration of an image forming apparatus according to Embodiment 1 of the present invention.
The same components as those in FIG. 1 are denoted by the same reference numerals.

In FIG. 8, a video signal output from the registration correction pattern generation control section 27a is output to a laser driver 27b, and the respective photosensitive drums are output via the laser scanning optical devices 3M, 3C, 3Y, 3Y. An electrostatic image corresponding to the registration correction test pattern is formed at a desired position of 1M, 1C, 1Y, and 1K.

In the image forming apparatus configured as described above, the test pattern forming means (each of the first to fourth image forming units PM, PC, PY, PK) starts a predetermined resist alignment pattern forming process on the photosensitive member. Then, the transfer control unit (in this embodiment, the registration correction pattern generation control unit 27a) sets the color pattern having no reflection characteristic on the test pattern of the color developer having the reflection characteristic transferred onto the transport belt 6. The multi-transfer of the test pattern of the developer (in this embodiment, black) is controlled, and the multi-transfer is performed so that a color developer test pattern having a reflection characteristic and a test pattern of a color developer having no reflection characteristic are overlapped. It is also possible to let.

When the test pattern reading device 12 detects the registration test pattern of each color transferred on the conveyor belt 6 in this manner, the timing control means (also used by the digital image processing unit 27) controls the reading device 12. By controlling the image forming timing based on the output,
Perform resist alignment.

FIGS. 9 and 10 show a schematic diagram (FIG. 9) of the test pattern 22 transferred onto the conveyor belt 6 and a reflection signal (FIG. 10) at that time. The test pattern 22 of the color toner TK having no reflection characteristics is multiplex-transferred onto the test pattern 22 of the color toner (magenta toner) TM having reflection characteristics, and non-overlapping portions (positions x1, x
The amount of registration can be determined by detecting the size L between (2). As shown in FIG. 10, the test pattern 2 of the illumination lamp 12b is between the positions x1 and x2.
2, the output voltage signal V of the reading sensor 12a is large.

FIGS. 11 to 14 show overlapping patterns when a square pattern 0 is used as a registration correction test pattern. The test pattern 2 of the color toner TK (black) having no reflection characteristics with hatching
2. By detecting the elliptical shape and the size of the non-overlapping portion, the registration amounts L1 and L of the color image forming unit with respect to the image forming unit PK (black station) are detected.
2 can be detected.

In this embodiment, it is necessary to transfer the toner having no reflection characteristic from the toner having the reflection characteristic, and it is desirable to arrange the toner TK having no reflection characteristic in the final image forming portion PK.

FIG. 15 illustrates the transfer processing of the square pattern with reference to a timing chart.

As shown in this figure, a predetermined time tm, t has elapsed since the rise of the reference ITOP shown in FIG.
c, ty and tk at the timing of each photosensitive drum 1M.
When laser exposure for image formation is started for 1C, 1Y, and 1K, four colors are exactly overlapped on the transport belt 6 or the transfer material P. Therefore, FIG.
In order to superimpose the black (hatched portion in FIG. 16) test pattern on the magenta M, cyan C, and yellow Y test patterns as shown in FIG. Good. FIG. 15 is a schematic diagram illustrating a test pattern transfer state of the present embodiment, in which a pair of pairs is transferred so as to face predetermined positions in the width direction orthogonal to the arrow A in the conveyance direction of the conveyance belt 6. Note that the hatched area in FIG.
The black K pattern of the image forming unit PK is magenta M,
This indicates that the image is transferred while being superimposed on the cyan and yellow Y color toners.

The test pattern for registration correction of each image forming portion transferred in this manner is detected by the reading device 12 provided downstream of the transport belt.

[Embodiment 2] FIG. 17 schematically shows a test pattern detected when both superposed toners have spectral reflection characteristics, for example, when the toners TM and TC have a color shift of length L. It is shown. FIG. 18 shows the test pattern 2 in the moving direction of the conveyor belt of FIG. 17 on the horizontal axis.
2, each position x1, x2, x3, x4 is taken, and the vertical axis shows the output voltage signal V of the reading sensor 12a.

According to this characteristic, in the portions x2 and x3 of the superimposed test pattern, the reflected signal V is high and the superimposed amount can be detected by identifying this. According to this method, if the black toner TK shown in FIGS. 11 to 14 is replaced with the color toners TM, TC, and TY, it is impossible to distinguish between the two test patterns. For this purpose, a recognizable identification mark pattern must be formed on one of the test patterns. Figures 19-2
FIG. 2 shows an example of the pattern of the identification mark. A test pattern 22 (TC) indicated by oblique lines is provided with an identification mark 22a.

[Embodiment 3] FIGS. 23 and 24 schematically show test patterns detected when the toner TY to be superimposed has a spectral reflection characteristic and the lower toner TK has no spectral reflection characteristic. It is shown in a typical manner.

According to this characteristic, in the portion of the superposed test pattern, the reflection signal becomes lower due to the superposition, and the superposition amount and direction are detected by discriminating between the portions x3 and x4 having the higher reflection characteristics. Can be.

In the above embodiment, the four-drum type full-color image forming apparatus shown in FIG. 1 has been described as an example.
The present invention can be applied to a full-color copying machine of a type in which a color developer is multiply developed on a photosensitive drum.

[0046]

According to the present invention, a plurality of image forming units, a test pattern carrier capable of carrying a plurality of test patterns formed by the plurality of image forming units, and a plurality of test pattern carriers on the test pattern carrier are provided. An image forming apparatus that has a test pattern reading unit that optically reads a test pattern, detects a resist shift amount by the test pattern reading unit, and corrects a resist. A test pattern formed of a developer having a spectral reflection characteristic that can be read by the test pattern reading means, and a test pattern formed of a developer having a spectral reflection characteristic read by the test pattern reading means. And detects the amount of registration deviation. That from the image forming apparatus, even a developer without spectral reflection characteristics, can be a test pattern for each registration correction reader detects readily identified. Therefore, registration of each color developer can be corrected with high accuracy, and a clear full-color image without color shift can be formed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a four-drum type color image forming apparatus.

FIG. 2 is a perspective view of a test pattern reading device for resist alignment.

FIG. 3 is a timing chart showing the timing of forming marks for resist alignment.

FIG. 4 is a timing chart showing the timing of forming marks for resist alignment.

FIG. 5 is a diagram illustrating a spectral reflection characteristic of a color developer.

FIG. 6 is a diagram showing the spectral reflection characteristics of three-type mixed black.

FIG. 7 is a diagram showing the spectral reflection characteristics of carbon black.

FIG. 8 is a block diagram of color shift correction control according to the first and second embodiments.

FIG. 9 is a longitudinal sectional view illustrating a light reflection state when the developer is superposed.

FIG. 10 is a diagram showing an output voltage V of a reading sensor in FIG. 9;

FIG. 11 is a plan view showing a pattern when the developer is superimposed.

FIG. 12 is a plan view showing a pattern when the developer is superimposed.

FIG. 13 is a plan view showing a pattern when the developer is overlaid.

FIG. 14 is a plan view illustrating a pattern when the developer is superimposed.

FIG. 15 is a timing chart showing data formation timing of a correction test pattern of the image forming apparatus shown in FIG. 8;

FIG. 16 is a schematic diagram of a test pattern on a transport belt.

FIG. 17 is a longitudinal sectional view illustrating a light reflection state when a developer is superimposed in Embodiment 2 of the present invention.

18 is a diagram showing an output voltage of a reading sensor in FIG.

FIG. 19 is a plan view showing a pattern when the developer is overlaid.

FIG. 20 is a plan view illustrating a pattern when the developer is superimposed.

FIG. 21 is a plan view showing a pattern when the developer is superimposed.

FIG. 22 is a plan view showing a pattern when the developer is overlaid.

FIG. 23 is a longitudinal sectional view illustrating a light reflection state when a developer is superimposed in Embodiment 3 of the present invention.

24 is a diagram showing an output voltage signal V of the reading sensor in FIG.

[Explanation of symbols]

 1. photosensitive drum 2. primary charging device 3. scanning optical device 4. developing device 5. cleaning device 6. transport belt 7. transfer charging device 8. fixing device 12. test pattern reading device 22 Test pattern 26 Image processing circuit 27 Timing control means 31 Color document 33 Color image sensor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiaki Tahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Gaku Fujita 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Non-corporation (72) Inventor Yoshihiro Murasawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masami Izumizaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Koji Amamiya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Nobunatsu Sasanuma 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc.

Claims (1)

[Claims] A plurality of image forming units, a test pattern carrier capable of carrying a plurality of test patterns formed by the plurality of image forming units, and a plurality of test patterns on the test pattern carrier. An image forming apparatus for detecting a resist deviation amount by the test pattern reading means and performing resist correction, wherein the test pattern reading means forms a developer having a spectral reflection characteristic which cannot be read by the test pattern reading means. And a test pattern formed of a developer having a spectral reflection characteristic that can be read by the test pattern reading unit. The test pattern reading unit reads the superposed test pattern, Image forming characterized by detecting the amount Location.