JP4750897B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a color laser printer, a color copying machine, and a color facsimile mainly employing an electrophotographic process.

  The present invention relates to an image forming apparatus that forms image information on an image support such as a transfer material, such as an electrophotographic apparatus, a laser beam printer, and a printing apparatus, and more particularly to a color electrophotographic apparatus or a color laser beam printer. As described above, the present invention relates to a multiple image forming apparatus in which a plurality of image forming units are arranged to form a multiple image. Hereinafter, in connection with the multiplex image forming apparatus of the present invention, in this specification, an example of an in-line method in which a plurality of different color image forming units are arranged in series and a developed image is transferred onto a transfer material conveyed by a transfer belt. I will talk about it.

  Conventionally, an image forming apparatus that includes a plurality of image forming units, forms images of different colors in each image forming unit, and transfers the images on the same transfer material, such as a so-called color image forming apparatus. Various multi-image forming apparatuses have been proposed. In such a multi-image forming apparatus, when transferring the image of the image forming unit to the transfer material, as a conveying means for conveying the transfer material to the image forming unit, A belt is often used. When forming multiple images as described above, if the registration of toner images of four colors, such as cyan, magenta, yellow, and black, transferred on the transfer material is poor, color misregistration and hue change As a result, the quality of the transferred image is significantly deteriorated, and the registration accuracy occupies a large weight for the image quality. In addition, the density and gradation of each color image transferred to the transfer material for each image area are the change in the photosensitive drum characteristics due to the environment, durability, etc., the change in the ratio of the developer toner to the carrier amount, the developer The image density needs to be controlled in order to always output a high-quality and stable density image that changes with deterioration due to durability.

  However, in the conventional multiplex image forming apparatus, one transfer material from each image forming unit due to fluctuations in the speed of the belt, incomplete maintenance of the belt, the image forming unit, etc. or position reproducibility after replacement, etc. Transfer between images formed from each image portion (color misregistration) occurs. This is a serious problem such as color blur or hue change in a color image. Therefore, in the conventional multiple image forming apparatus, a specific color misregistration detection pattern is transferred to the transfer belt in order to correct a shift in the transfer position of each color transferred from each image forming unit onto one transfer material and superimposed. Later, the pattern was read as an electrical signal by a color misregistration detection sensor as a pattern reading device, and the signal was processed to correct a shift in the transfer position of each color (hereinafter referred to as color misregistration correction).

  Further, in order to control the density of the image transferred onto the transfer material, after transferring the density detection pattern having gradation for each color to the transfer belt, the density detection pattern of the pattern is transferred to the transfer belt as described above. A density detection sensor as a pattern reading device has also been used to control the density of an image that is optically read and transferred onto a transfer material (hereinafter referred to as density correction).

  However, in the above-described conventional example, since each of the color misregistration detection pattern and the density detection pattern is read by a separate pattern reading device, from the viewpoint of effective use of the space in the multiple image forming apparatus, the cost is also reduced. It could not be said that it was the best from the aspect. Therefore, the color misregistration detection pattern and the density detection pattern transferred to the transfer material can be read by the same pattern reading device, and the multiple image which can minimize the space occupied by the pattern reading device and reduce the manufacturing cost. A forming apparatus is provided (see, for example, Patent Document 1).

  Furthermore, a method has been proposed in which color misregistration correction and image density adjustment are performed in the same sequence to shorten the waiting time of the user.

  In addition, when the surface state of the ground changes depending on the degree of use, the amount of reflected light also varies. Therefore, as a solution, a method has been devised in which the amount of light during color misregistration detection and density detection is changed according to the amount of reflected ground light. However, in Patent Document 2, the same light amount setting value is used as the light amount setting value at the time of color misregistration detection and density detection (see, for example, Patent Document 2).

  Further, recent color misregistration detection sensors and density detection sensors mainly employ a method of detecting regular reflection components or irregular reflection components of reflected light. FIG. 2 is a conceptual diagram showing the relationship between irradiation light and regular reflection light. FIG. 3 is a conceptual diagram showing the relationship between irradiation light and irregular reflection light. In the type of sensor that detects specularly reflected light, as shown in FIG. 2, the reflected light is reflected in a direction that is symmetrical to the irradiation angle α with respect to the normal of the base surface (electrostatic adsorption belt surface, hereinafter referred to as ETB surface). Detect light. As shown in FIG. 3, the sensor of the type that detects irregularly reflected light detects light reflected in a direction (light receiving angle β) different from the irradiation angle α with respect to the normal line of the base surface (ETB surface). The amount of specular reflection depends on the refractive index specific to the material of the base (ETB) and the reflectance determined by the surface state, and feels glossy. FIG. 4 is a conceptual diagram showing the relationship between irradiation light and regular reflection light when toner is present on the ETB, and FIG. 5 is a graph showing the relationship between toner amount and regular reflection light amount. The amount of regular reflection is maximized when no toner is present on the ground. When the toner pattern is formed on the ground, the ground is hidden and the specular reflection light disappears in a portion where the toner is present as shown in FIG. Therefore, the relationship between the toner amount of the toner pattern and the amount of reflected light becomes smaller as the amount of toner increases as shown in FIG. The toner pattern here is a pattern created by laying toner on the conveyance belt, and includes a color misregistration detection pattern and a density detection pattern.

  However, a problem arises when chromatic toner is detected by a density detection sensor that detects regular reflection light. FIG. 6 is a conceptual diagram of irradiation light and reflected light when chromatic toner is detected. When light is applied to the density detection pattern of the chromatic color toner, irregularly reflected light increases as the amount of toner increases, and the reflected light is diffused in all directions. Therefore, the light detected by the density detection sensor is the sum of the regular reflection component and the irregular reflection component as shown in FIG. As shown in FIG. 7, the relationship between the toner amount and the amount of reflected light at this time is the sum of the fine solid line that is the regular reflection characteristic and the broken line that is the irregular reflection characteristic, and exhibits negative characteristics such as a thick solid line. For this reason, the linearity necessary for density detection cannot be obtained, and the density detection accuracy is not sufficient. Therefore, by subtracting the diffuse reflection light component from the sum of the regular reflection light component and the diffuse reflection light component, only a regular reflection light component that is sensitive to visual characteristics and has high reflected light intensity and high detection accuracy can be obtained with a simpler density detection means. Has been devised (see, for example, Patent Document 3).

Japanese Patent No. 2573855 JP 2001-16553 A JP 2003-215883 A

  In the one-emission two-light-receiving sensor system, when the same light amount setting value is used at the time of color misregistration detection and density detection as in the conventional example, the difference in pattern density between color misregistration detection and density detection and the difference in detection conditions There has been a problem that either the color misregistration detection or the density detection is not determined as an appropriate light amount setting value. For example, if the reflected light amount of the background is detected in advance and the light amount at the time of color misregistration detection and density detection is obtained based on the result, if the irregular reflection output from the toner pattern is higher than the regular reflection output from the belt, the irregular reflection output Is saturated and the irregular reflection output from the toner pattern is lower than the regular reflection output from the belt, the dynamic range of the irregular reflection output is reduced, which is affected by waveform rounding and random noise, so accurate density detection and color Misalignment cannot be detected. Furthermore, if the amount of reflected light of the toner pattern is detected in advance and the amount of light at the time of color misregistration detection and density detection is obtained based on the result, the specular reflection output is saturated or the dynamic range is insufficient. There are cases where density detection and color misregistration detection cannot be performed.

  Therefore, the present invention determines a light amount setting value at the time of color misregistration detection and density detection separately in a system of one light emission and two light receiving sensors, and sets an appropriate light amount value at each detection, thereby achieving high-precision color. It is an object of the present invention to provide an image forming apparatus that can perform deviation correction and density correction.

In order to solve the above-described problems, the present invention has the following configurations (1) to (3).
(1) a plurality of image forming units each having an image carrier for carrying a toner image;
An endless belt,
Transfer means for transferring a toner image carried on each image carrier of the plurality of image forming means onto the endless belt;
Pattern forming means for forming a color misregistration detection pattern and a density detection pattern on the endless belt by the transfer means;
Illuminating means for illuminating the endless belt and the color misregistration detection pattern and the density detection pattern;
Comprising a first light detecting means for detecting the amount of specular reflection from the irradiation area irradiated with light by the illumination means and a second detection section for detecting the amount of irregular reflection light from the irradiation area;
The amount of emitted light at the time of color misregistration detection and density detection is determined separately from the amount of specular reflection from the endless belt and the amount of specular reflection or irregular reflection from the toner area. And an image forming apparatus characterized by separately determining the amount of emitted light at the time of density detection.
(2) a plurality of image forming units each having an image carrier for carrying a toner image;
An endless belt,
Transfer means for transferring a toner image carried on each image carrier of the plurality of image forming means onto the endless belt;
Pattern forming means for forming a color misregistration detection pattern and a density detection pattern on the endless belt by the transfer means;
Illuminating means for illuminating the endless belt and the color misregistration detection pattern and the density detection pattern;
Comprising a first light detecting means for detecting the amount of specular reflection from the irradiation area irradiated with light by the illumination means and a second detection section for detecting the amount of irregular reflection light from the irradiation area;
From the regular reflection light amount from the endless belt and the regular reflection light amount or irregular reflection light amount from the toner area, separately determine the light emission amount at the time of color shift detection and density detection,
An image forming apparatus characterized by separately determining the amount of emitted light at the next color misregistration detection and density detection at the time of density detection.
(3) a photosensitive drum;
Image forming means for forming a toner image on the photosensitive drum;
A belt to which a toner image formed on the photosensitive drum is transferred,
An image forming apparatus that forms and detects a color misregistration detection pattern, performs color misregistration correction based on the detection result, forms and detects a density detection pattern, and performs image density control based on the detection result,
A light emitting element that emits light, a regular reflection light receiving element that receives specular reflection light when irradiated by the light emitting element, and a diffuse reflection light reception that receives irregular reflection light when irradiated by the light emitting element. An optical detection means including an element;
The detection of the color misregistration detection pattern is performed based on the output of the irregularly reflected light receiving element when the light misregistration light is irradiated to the color misregistration detection pattern, and the detection of the density detection pattern is performed as described above. Based on the output of the regular reflection light receiving element and the output of the irregular reflection light receiving element when light is emitted from the light emitting element to the density detection pattern,
Further, regarding the detection of the color misregistration detection pattern, the output of the irregularly reflected light receiving element is not saturated when the light emitting element emits light toward the color misregistration detection pattern or the light emission amount determining toner pattern. While adjusting and setting the light emission amount of the light emitting element,
Control means for adjusting and setting the light emission amount of the light emitting element so that the output of the regular reflection light receiving element is not saturated when the light emitting element emits light toward the belt with respect to detection of the density detection pattern And an image forming apparatus.

  According to the first aspect of the present invention, the light quantity setting value at the time of color misregistration detection and density detection is determined separately in the one light emission two light receiving sensor system, and an appropriate light quantity value is set at each detection. Thus, it is possible to perform highly accurate color misregistration correction and density correction.

  According to the second aspect of the present invention, when color misregistration is detected in the one-emission two-light-receiving sensor system, the light amount setting values at the time of color misregistration detection and density detection are determined separately, and appropriate for each detection. It is possible to set the light quantity value.

  According to the third aspect of the present invention, the light amount setting value at the time of color misregistration detection and at the time of density detection is separately determined at the time of density detection in the system of one light emission and two light receiving sensors, and an appropriate light amount at the time of each detection. It is possible to set a value.

  According to the fourth aspect of the present invention, the density correction is performed by detecting the regular reflection light quantity and the irregular reflection light quantity from the belt, and the color shift correction is performed by detecting the irregular reflection light quantity from the belt and the toner pattern. In this system, it is possible to separately determine the light amount setting values at the time of color misregistration detection and density detection, and to set an appropriate light amount value at each detection.

  According to the fifth aspect of the present invention, the density correction is performed by detecting the regular reflection light quantity and the irregular reflection light quantity from the belt, and the color misregistration correction is performed by calculating the regular reflection light quantity from the belt and the toner pattern. In the detection system, it is possible to separately determine the light amount setting value at the time of color misregistration detection and density detection, and to set an appropriate light amount value at the time of each detection.

Change graph of conveyor belt and sensor output when detecting toner pattern on conveyor belt Conceptual diagram showing the relationship between the light emitted from the light source and the specularly reflected light reflected to the light receiving element Conceptual diagram showing the relationship between irradiated light and diffusely reflected light Conceptual diagram showing the relationship between irradiation light and regular reflection light when toner is present on the ETB A graph showing the relationship between the amount of toner and the amount of specular reflection Conceptual diagram of irradiated light and reflected light when chromatic toner is detected Conceptual diagram showing the relationship between the amount of toner and the amount of reflected light 1 is a perspective explanatory view showing a schematic configuration of an image forming apparatus of the present invention. Explanatory drawing of the detection means of this invention Circuit configuration diagram of detection means of the present invention Algorithm of operation of the first embodiment and the second embodiment Configuration diagram of color misregistration detection pattern of the first embodiment Configuration diagram of color misregistration detection pattern of second embodiment Relationship diagram between the amount of toner before light amount correction and the amount of reflected light in the first embodiment FIG. 4 is a relationship diagram between the amount of toner after light amount correction and the amount of reflected light when density is detected in the first embodiment. FIG. 6 is a relationship diagram between the toner amount after light amount correction and the amount of irregularly reflected light when color misregistration is detected in the first embodiment. Relationship diagram between toner amount before light amount correction and reflected light amount in the second embodiment Relationship diagram between the amount of toner after light amount correction and the amount of reflected light at the time of density detection in the second embodiment FIG. 6 is a relationship diagram between a toner amount after light amount correction and a reflected light amount when color misregistration is detected in the second embodiment.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  In the present embodiment, in a system in which density correction is performed using a regular reflection output and irregular reflection output with a single light emission and two light receiving sensor, and color misregistration correction is performed using irregular reflection output, the positive correction when the conveyance belt is detected at the time of color misalignment detection is performed. The light amount is calculated from the diffuse output when the reflected output and the light emission quantity determination pattern are detected, so that the dynamic range of the sensor output required at the time of color shift detection and density detection is increased, and at the next color shift detection and density detection. Determine the optimal amount of light separately.

  A first embodiment of the present invention will be described below with reference to the drawings.

  First, a schematic configuration of the image forming apparatus of the present invention will be described with reference to FIG. The color image forming apparatus of the present embodiment includes four color (yellow Y, magenta M, cyan C, and black Bk) image forming units. Subscript symbols a, b, c, and d in FIG. 8 indicate C, Y, M, and Bk, respectively. Reference numeral 1 denotes a photosensitive drum that forms an electrostatic latent image. A laser scanner 2 performs laser exposure according to an image signal to form an electrostatic latent image on the photosensitive drum 1. Reference numeral 3 denotes an endless conveyance belt that sequentially conveys the paper to the image forming units for each color, and also has a function of a transfer belt. Reference numeral 4 denotes a driving roller that rotationally drives the conveyor belt 3, and is connected to a driving means including a motor and a gear (not shown). Reference numeral 5 denotes a driven roller that rotates following the movement of the conveyance belt 3 and applies a constant tension to the conveyance belt 3. Reference numeral 20 denotes a transfer roller. Reference numeral 6 denotes a pair of optical sensors that detect a color misregistration detection pattern and a density detection pattern formed on the conveyance belt 3, and are provided on both sides of the conveyance belt.

  The first photosensitive drum 1a in FIG. 8 is uniformly charged by the charging roller 17a while being driven to rotate at a predetermined peripheral speed in the direction of arrow d1, and corresponds to a digital image signal scanned from the laser scanner 2a. By receiving the modulated laser beam through the imaging exposure optical system, an electrostatic latent image of the first color (here, cyan) component is formed. The image signals of the respective colors are transmitted to the laser scanners after a predetermined time has elapsed from the timing of sheet conveyance by the conveyance transfer belt 3.

  Subsequently, the electrostatic latent image is developed with the first color (cyan) toner using the first developing device 18a to obtain a visible image for the first color component. The procedure described above is performed for the second color (yellow), the third color (magenta), and the fourth color (black). The transport transfer belt 3 is rotationally driven in the direction of the arrow d2 at the same peripheral speed as the photosensitive drum 1a. The transfer of the cyan visible image from the photosensitive drum 1a to the sheet P adsorbed and supported on the transport transfer belt 3 is performed by applying a transfer bias supplied from a high voltage power supply (not shown).

  Thereafter, for yellow, magenta, and black, a full-color toner image is obtained by sequentially superimposing and transferring on the sheet P adsorbed and supported on the conveyance transfer belt using the same procedure.

  The sheet P to which the toner image has been transferred is separated from the transport transfer belt and transported to a fixing device (not shown). The sheet P conveyed to the fixing device is fixed with a toner image by heat and pressure at a fixing nip portion between the fixing roller and the pressure roller. At the time of cleaning, a toner having a polarity opposite to that applied at the time of transfer is applied to collect the toner in the cartridge.

  FIG. 9 shows detection means (light sensor) corresponding to 6 in FIG. 51 is a light emitting element, for example, LED. 52 and 59 are light receiving elements, for example, photosensors. 3 is a conveyance belt, and 9 is a toner pattern. Reference numeral 53 denotes light emitted from the light emitting element 51. 54 is light received by the light receiving element 52, and 58 is light received by the light receiving element 59. The light emitting unit 51 and the light receiving unit 52 are configured by a regular reflection optical system with the transport belt 3 as a reflecting surface, and the light emitting unit 51 and the light receiving unit 59 are configured by an irregular reflection optical system with the transport belt 3 as a reflecting surface. ing. Further, the position of the color misregistration detection pattern or the density of the density detection pattern is detected based on the difference between the light reflectance by the conveyor belt 3 and the light reflectance by the toner pattern.

  FIG. 10 shows a circuit configuration of the detection means in FIG. The pattern detection unit is composed of an LED light emitting unit (LED) and a photosensor light receiving unit or the like (PD). The LED emits light to the transport belt, and the reflected light from the transport belt is received by the light receiving element PD. The detected current from the light receiving element PD is converted into a voltage V1 by an IV conversion circuit and input to a CPU (not shown). The CPU compares and calculates the magnitude relationship between the “output voltage value of the IV conversion circuit” and the “target output voltage value”, and determines the light amount at the next color misalignment detection and density detection. Further, on / off of the light emitting element and light amount adjustment are performed by varying the LED drive current by PWM control (Input in FIG. 10) of a CPU (not shown).

  FIG. 12 shows a configuration of a color misregistration detection pattern formed on the conveyance belt 3 of FIG. This color misregistration detection apparatus uses a light emission light quantity determination pattern 93 (93a, 93b) as shown in FIG. 12 on the conveyor belt 3 in order to calculate the optimum light quantity setting value at the next color misregistration detection and density detection. Form. The light emission quantity determination pattern may be any color as long as it is a solid color pattern other than Bk. Further, color misregistration detection patterns 9, 10, 11, 12 (a: C, b: Y, c: M, d: Bk) as shown in FIG. To do. The color misregistration detection pattern is also a solid pattern. Reference numerals 9 and 10 are patterns for detecting the amount of color misregistration in the sub-scanning direction, and reference numerals 11 and 12 are patterns for detecting the amount of color misregistration in the main scanning direction. The pattern is read by a pair of sensors 6 provided side by side in the main scanning direction of the conveyor belt, the optimum light amount setting value at the next detection is determined, and the color misregistration amount between each color is detected. In addition, since the color misregistration detection apparatus of this embodiment performs diffuse reflection detection, when detecting Bk toner, color misregistration is performed by placing color toner patterns 13a, 13b, 13c, and 13d having different light reflectivities under the Bk toner pattern. Perform detection.

  In general, the light receiving sensor has a characteristic that the response speed decreases when the amount of received light is small. In FIG. 1, color misregistration detection patterns 9, 10, 11, and 12 (magenta in the drawing) are put on the transport belt 3 to rotate the transport belt 3, and the surface of the transport belt and the color misregistration detection pattern is detected by the optical sensor 6. It is the figure which showed the change of the sensor output at the time of detecting. The horizontal axis represents time, and the vertical axis represents the optical sensor output. d2 indicates the conveyance direction of the conveyance belt 3. A waveform M represents an actual sensor output waveform. A waveform N shows an ideal waveform when the sensor output responds without delay. A waveform O indicates a sensor output waveform when the amount of received light from the sensor is lower than that of the waveform M. The color misregistration amount is calculated based on the center value of the time when the output of the light receiving element crosses the threshold voltage as in the conventional example. The actual sensor output waveform M is a round waveform compared to the ideal waveform N as shown in FIG. Therefore, the actual sensor output waveform M has a color shift amount time error ΔTa due to a rounded waveform with respect to the ideal waveform. When the amount of light received by the sensor is reduced, the waveform is further affected by the rounding like the waveform O. For this reason, the influence of the round waveform increases, and a color shift amount time error ΔTb is generated. This is larger than ΔTa. Also, if the waveform is rounded, it is easily affected by random noise.

  For this reason, the target light amount setting value at the time of density detection and color misregistration detection is set so that the dynamic range of the sensor output is increased on condition that the sensor output is not saturated, and it depends on the light reflectance by the belt and the toner pattern. The difference in light reflectance must be increased.

  FIG. 11 shows the algorithm of the operation of this embodiment. The operation up to the determination of the light amount will be described with reference to FIG.

  First, a light emission quantity determination pattern (FIG. 12: 93a, 93b) is formed on the conveyor belt, and a color misregistration detection pattern (FIG. 12, 9, 10, 11, 12, 13) is formed. (Step S1). Wait until it is time to read the reflected light from the surface of the conveyor belt before the first light emission quantity determining pattern. The reading timing of the optical sensor is calculated and controlled by the CPU from the pattern formation timing. When it is time to read the reflected light from the conveyor belt surface, the light emitting element (LED) is caused to emit light, and the amount of regular reflected light when the belt is detected is set to a level that does not saturate even when the belt is new. The on / off of the light emitting element and the light amount adjustment are performed by PWM control of the LED driving circuit with a signal from the CPU (step S2). The conveyance belt is driven to rotate, and the light emission quantity determination pattern is detected (step S3). The optimum light quantity value at the time of color misregistration detection and the optimum light quantity value at the next density detection are calculated and stored by the CPU. In addition, the calculated optimal light amount value at the time of color misregistration detection is set as the light amount (step S4), and the conveyance belt is rotated to detect a color misregistration detection pattern (step S5). A color misregistration correction value for performing color misregistration correction such as fine adjustment of image frequency and adjustment of writing timing is calculated (step S6). at the same time. By turning off the LED and applying a bias reverse in polarity to the bias applied at the time of transfer, the toner is collected in the cartridge and the transport belt is cleaned (steps S7 and S8).

  FIG. 14A shows the relationship between the toner amount and the reflected light amount in this embodiment, and shows the state before the light amount correction. In this embodiment, the maximum light reception amount of regular reflection is larger than the maximum light reception amount of irregular reflection. In FIG. 14A, Vx is the target output voltage for regular reflection and irregular reflection output, Va is the regular reflection maximum output before light amount correction, and Vb is the irregular reflection maximum output before light amount correction. Before the light quantity correction, a state at a light quantity L1 at which the regular reflection output and the irregular reflection output are not saturated is shown. FIG. 14B shows the relationship between the reflected output after the light amount correction at the time of density detection and the toner amount, and FIG. 14C shows the relationship between the irregular reflection output after the light amount correction at the time of color shift detection and the toner amount. . Since both the regular reflection output and the irregular reflection output are used in the density detection, the light amount Ld is set so that the regular reflection output is not saturated and the dynamic range is increased. Since the regular reflection output is not used in color misregistration detection, the light amount Lr is set so that the irregular reflection output is not saturated and the dynamic range is increased.

Here, it is assumed that the light amount setting value of the light emission amount determining toner pattern is L1, the regular reflection output at the time of detecting the belt is Vb, and the irregular reflection output at the time of detecting the light emission amount determining pattern is Vt. When the target irregular reflection output voltage at the time of color misregistration detection is Vr and the target regular reflection output voltage at the time of density detection is Vd, the optimum light quantity setting value Lr at the time of color misregistration detection and the optimum light quantity setting value at the time of density detection. Ld is calculated from the equations (1) and (2).
Lr = (Vr / Vt) * L1 (1)
Ld = (Vd / Vb) * L1 (2)
It can be asked. At this time, as described above, the target regular reflection output voltage value and the target irregular reflection output voltage value are set so that the sensor output is not saturated and the dynamic range of the sensor output is increased.

  As described above, in the system in which the density correction is performed using the regular reflection output and the irregular reflection output by the one light emission two light receiving sensor, and the color misregistration correction is performed using the irregular reflection output, when the conveyance belt is detected when the color misregistration is detected. From the diffuse reflection output when the regular reflection output and the color misregistration detection pattern are detected, the light quantity is calculated so that the dynamic range of the sensor output required at the time of color misregistration detection and density detection is increased, and at the next color misalignment detection and density detection. By determining the optimal amount of light separately, it is possible to reduce the influence of waveform rounding and random noise during both color misregistration detection and density detection, and to perform highly accurate color misregistration correction and density correction. It is. In this embodiment, the light amount is adjusted by PWM control by the CPU, but it goes without saying that the light amount can be adjusted by using a D / A converter of the CPU.

  In this embodiment, the optimum light amount at the next color misregistration detection and density detection is determined at the time of color misregistration detection, but the optimum light amount at the next color misregistration detection and density detection by the same process at the density detection. Needless to say, it is possible to determine.

  In the present embodiment, in a system in which density correction is performed using a regular reflection output and irregular reflection output with a single light emission and two light receiving sensor, and color misregistration correction is performed using a specular reflection output, when a conveyance belt is detected when color misregistration is detected. The amount of light is calculated from the irregular reflection output when the specular reflection output and the pattern for determining the amount of emitted light are detected, so that the dynamic range of the sensor output required at the time of color misalignment detection and density detection is increased, and at the next color misalignment detection and density The optimal amount of light at the time of detection is determined separately.

  In the present embodiment, the same detection means (FIG. 9) and circuit configuration (FIG. 10) as in the first embodiment are used.

  FIG. 13 shows the configuration of the color misregistration detection pattern in the present embodiment formed on the conveyor belt 3 of FIG. The color misregistration detection apparatus in the present embodiment performs color misregistration correction in the same manner as in the first embodiment, and further calculates the optimum light amount setting value at the next color misregistration detection and density detection on the conveying belt 3 as shown in FIG. As shown, a light emission quantity determining pattern 94 (94a, 94b) and color misregistration detection patterns 9, 10, 11, 12 (a: C, b: Y, c: M, d: Bk) are formed. In addition, since the color misregistration detection apparatus according to this embodiment performs regular reflection detection, unlike the first embodiment, it is not necessary to lay a color toner pattern having a different light reflectance below the Bk toner pattern.

  As for the operation algorithm, the same algorithm as in the first embodiment can be used.

  FIG. 15A shows the relationship between the amount of toner and the amount of reflected light in this embodiment. In this embodiment, the amount of irregularly reflected light when the belt is detected is larger than the amount of regular reflected light when the belt is detected. In FIG. 15A, Vx ′ represents a target output voltage for regular reflection and irregular reflection output, Va ′ represents a regular reflection maximum output before light amount correction, and Vb ′ represents an irregular reflection maximum output before light amount correction. In addition, before the light amount correction, a state at a light amount L1 'in which the regular reflection output and the irregular reflection output are not saturated is shown. FIG. 15B shows the relationship between the reflected output after the light amount correction at the time of density detection and the toner amount, and FIG. 15C shows the relationship between the reflected output after the light amount correction at the time of color shift detection and the toner amount. . In density detection, control is performed to subtract the irregularly reflected light component from the sum of the regular reflected light component and the irregularly reflected light component, so that the light amount Ld ′ is set so that the regular reflection output is not saturated and the dynamic range is increased. Since the irregular reflection output is not used in the color misregistration detection, the light amount Lr ′ is set so that the irregular reflection output is not saturated and the dynamic range is increased. The color misregistration detection pattern of this embodiment is set to a toner density (Tx in FIG. 15C) that maximizes the difference between the regular reflection output from the belt and the irregular reflection output from the color misregistration detection pattern.

  Also in the second embodiment, the same calculation method as in the first embodiment can be used by separately determining the optimum light amount at the next color misalignment detection and density detection.

  As described above, in the system in which the density correction is performed using the regular reflection output and the irregular reflection output by the one light emission / two light receiving sensor, and the color misregistration correction is performed using the specular reflection output, when the conveyance belt is detected when the color misregistration is detected. The amount of light is calculated from the specular reflection output and the diffuse reflection output when the emitted light amount determination pattern is detected, so that the dynamic range of the sensor output required for color misalignment detection and density detection is increased. By determining the optimal amount of light at the time of density detection separately, the effects of waveform rounding and random noise are reduced at both color shift detection and density detection, and high-precision color shift correction and density correction are performed. Is possible. Although the light amount adjustment is performed by the PWM control by the CPU as in the first embodiment, it is needless to say that the light amount can be adjusted using a D / A converter of the CPU. In this embodiment, the optimum light amount at the next color misregistration detection and density detection is determined at the time of color misregistration detection, but the optimum light amount at the next color misregistration detection and density detection by the same process at the density detection. Needless to say, it is possible to determine.

  In this embodiment, in the system in which the density correction is performed using the regular reflection output and the irregular reflection output by the one light emission two light receiving sensor, and the color misregistration correction is performed using the irregular reflection output, the conveyance belt is detected at the first color misalignment detection. The amount of light is calculated from the specular reflection output and the diffuse reflection output when the emitted light intensity determination pattern is detected so that the dynamic range of the sensor output required at the time of color misalignment detection and density detection is increased. In addition, the optimum light quantity at the time of density detection is determined separately. The pattern for determining the amount of emitted light is eliminated from the next detection of the color misregistration amount. From the specular reflection output when the conveyor belt is detected during color misregistration detection and the irregular reflection output when the color misregistration detection pattern is detected, the color misregistration detection and density The amount of light is calculated so that the dynamic range of the sensor output required at the time of detection is increased, and the optimum amount of light at the next color misalignment detection and density detection is determined separately.

  In the present embodiment, the same detection means (FIG. 9) and circuit configuration (FIG. 10) as in the first embodiment are used.

  Regarding the operation algorithm, the first color misregistration detection can be performed in the same manner as in the first embodiment. From the second time onward, a pattern for determining the amount of emitted light is not formed, but the method for determining the optimum light amount at the time of next color misregistration detection and density detection separately from the color misregistration detection pattern by the same calculation method as in the first embodiment. be able to.

  As described above, in the system in which the density correction is performed using the regular reflection output and the irregular reflection output by the one light emission two light receiving sensor, and the color misregistration correction is performed using the irregular reflection output, the light emission amount from the second or subsequent color misalignment detection. By eliminating the determination pattern, it is possible to reduce the second and subsequent color misregistration detection and light amount determination time as compared with the first embodiment. Further, as in the first embodiment, it is possible to reduce the influence of waveform rounding and random noise both at the time of color misregistration detection and at the time of density detection, and to perform highly accurate color misregistration correction and density correction. Although the light amount adjustment is performed by the PWM control by the CPU as in the first embodiment, it is needless to say that the light amount can be adjusted using a D / A converter of the CPU. In this embodiment, the optimum light amount at the next color misregistration detection and density detection is determined at the time of color misregistration detection, but the optimum light amount at the next color misregistration detection and density detection by the same process at the density detection. Needless to say, it is possible to determine.

  In the present invention, as shown in the first to third embodiments, the present invention is not limited to the one-light-emission / two-light-reception sensor, and other light-emission / light-reception configurations may be used.

DESCRIPTION OF SYMBOLS 1 Image carrier which carries a toner image 2 Several image forming parts 3 Conveying part which conveys the recording medium P with respect to several image forming parts 4 Drive roller 5 Followed roller 6 Optical sensor 9, 10 Color shift of subscanning direction Patterns 11 and 12 for detecting the amount Pattern 13 for detecting the amount of color misregistration in the main scanning direction Color toner pattern 17 having different light reflectivity on the lower layer of the Bk toner pattern 17 Charging roller 18 Developer 20 Transfer roller 51 Light emission Elements 52 and 59 Light-receiving element 53 Emitted light 54 Regular reflection 58 Diffuse reflection

Claims (3)

A plurality of image forming means each having an image carrier for carrying a toner image;
An endless belt,
Transfer means for transferring a toner image carried on each image carrier of the plurality of image forming means onto the endless belt;
Pattern forming means for forming a color misregistration detection pattern and a density detection pattern on the endless belt by the transfer means;
Illuminating means for illuminating the endless belt and the color misregistration detection pattern and the density detection pattern;
Comprising a first light detecting means for detecting the amount of specular reflection from the irradiation area irradiated with light by the illumination means and a second detection section for detecting the amount of irregular reflection light from the irradiation area;
The amount of emitted light at the time of color misregistration detection and density detection is determined separately from the amount of specular reflection from the endless belt and the amount of specular reflection or irregular reflection from the toner area. And an image forming apparatus characterized by separately determining the amount of emitted light at the time of density detection. A plurality of image forming means each having an image carrier for carrying a toner image;
An endless belt,
Transfer means for transferring a toner image carried on each image carrier of the plurality of image forming means onto the endless belt;
Pattern forming means for forming a color misregistration detection pattern and a density detection pattern on the endless belt by the transfer means;
Illuminating means for illuminating the endless belt and the color misregistration detection pattern and the density detection pattern;
Comprising a first light detecting means for detecting the amount of specular reflection from the irradiation area irradiated with light by the illumination means and a second detection section for detecting the amount of irregular reflection light from the irradiation area;
From the regular reflection light amount from the endless belt and the regular reflection light amount or irregular reflection light amount from the toner area, separately determine the light emission amount at the time of color shift detection and density detection,
An image forming apparatus characterized by separately determining the amount of emitted light at the next color misregistration detection and density detection at the time of density detection . A photosensitive drum;
Image forming means for forming a toner image on the photosensitive drum;
A belt to which a toner image formed on the photosensitive drum is transferred,
An image forming apparatus that forms and detects a color misregistration detection pattern, performs color misregistration correction based on the detection result, forms and detects a density detection pattern, and performs image density control based on the detection result,
A light emitting element that emits light, a regular reflection light receiving element that receives specular reflection light when irradiated by the light emitting element, and a diffuse reflection light reception that receives irregular reflection light when irradiated by the light emitting element. An optical detection means including an element;
The detection of the color misregistration detection pattern is performed based on the output of the irregularly reflected light receiving element when the light misregistration light is irradiated to the color misregistration detection pattern, and the detection of the density detection pattern is performed as described above. Based on the output of the regular reflection light receiving element and the output of the irregular reflection light receiving element when light is emitted from the light emitting element to the density detection pattern,
Further, regarding the detection of the color misregistration detection pattern, the output of the irregularly reflected light receiving element is not saturated when the light emitting element emits light toward the color misregistration detection pattern or the light emission amount determining toner pattern. While adjusting and setting the light emission amount of the light emitting element,
Control means for adjusting and setting the light emission amount of the light emitting element so that the output of the regular reflection light receiving element is not saturated when the light emitting element emits light toward the belt with respect to detection of the density detection pattern an image forming apparatus characterized by chromatic when the.

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