JP2021181904A - Colorimetric device and image forming apparatus - Google Patents

Abstract

To reduce the time required for correction processing of a colorimetric device and prevent a reduction in colorimetric accuracy.SOLUTION: A colorimetric unit 202 has a colorimetric sensor 2001a that can read an image formed on a sheet and a white reference plate and performs colorimetry by measuring reflected light of light from a light source with which a test image formed on the sheet is irradiated, and performs calibration of the colorimetric sensor 2001a by using a result of the reading of the white reference plate with the colorimetric sensor 2001a. The colorimetric sensor 2001a selectively executes any one of first correction processing including light quantity adjustment as correction processing and second correction processing not including the light quantity adjustment, and the time required for the second correction processing is shorter than the time required for the first correction processing. The colorimetric sensor performs the first correction processing and subsequently performs the second correction processing not including performing the light quantity adjustment so as to reduce the time required for the calibration.SELECTED DRAWING: Figure 3

Description

The present invention relates to a technique of measuring a test image formed on a paper by a color measuring device and correcting the color measuring device.

In recent years, electrophotographic image forming devices have become widespread in the office market as laser printers, multifunction devices, etc., and their entry into the commercial printing market is accelerating. This is because, in the market where printed matter is a commercial product, electrophotographic image forming equipment has a low number of copies such as regional newspapers and direct mail, and a short period of time and low demand for printing a wide variety of products compared to conventional offset printing machines. This is due to the fact that it can be met at a cost.

Items for evaluating image quality include graininess, in-plane uniformity, character quality, and color reproducibility, and among them, color reproducibility is important. Color reproducibility is the ability to output the same color as the color of a printed document. Conventionally, in order to output an image having high color reproducibility, a test chart in which a plurality of predetermined color patch images are formed is output, and the output test chart is measured by a color measuring device to perform color correction. However, the color measurement work of the test chart is performed offline, and the work time for color correction becomes long.

Therefore, it is desired to shorten the color measuring time in the color measuring device, and an image forming device equipped with the color measuring device in-line near the paper ejection portion of the printer is also on the market. Patent Document 1 discloses an image forming apparatus including an in-line color measuring apparatus that detects a patch image formed on a recording medium by a spectrophotometer. However, in the image forming apparatus described in Patent Document 1, if the number of spectrophotometers is not increased, the patches arranged on the test chart are only one row in the paper transport direction. Therefore, in this case, the number of patches that can be placed on one test chart is reduced, and the time required for color measurement becomes long. In addition, increasing the number of spectrophotometers is not desirable because it increases the cost.

Patent Document 2 discloses a configuration in which a spectrophotometer as a colorimeter performs color measurement while scanning on a test chart in the main scanning direction. In this configuration, which is used in inkjet image forming equipment, patches can be placed in the main scanning direction without increasing the number of color measuring equipment, dramatically increasing the number of test charts required for color correction. It is possible to reduce. Here, the measurement of the patch image by the spectrophotometer is performed after the calibration operation by the white reference plate is executed. However, when performing control for measuring a large number of patch images such as color profile creation, the time required for adjustment by the spectrophotometer becomes long. As the adjustment time becomes longer, there is a high possibility that the state such as the temperature of the spectrophotometer and the state when the calibration operation is executed will be different. In order to prevent this, for example, calibration can be performed at predetermined intervals during adjustment by a spectrophotometer. Further, if it is desired to shorten the adjustment time, the temperature of the spectrophotometer can be monitored and the calibration operation can be executed when the temperature changes more than a predetermined value.

Japanese Unexamined Patent Publication No. 2017-147562 Japanese Patent No. 57518112

Since the adjustment time by the in-line spectrophotometer takes a long time depending on the control performed at the time of adjustment, it is necessary to increase the number or frequency of calibration of the white reference plate. However, the calibration of the white reference plate includes a plurality of steps such as dark current adjustment, light amount adjustment, distortion correction, and white reference plate data update, and if all of these steps are executed, a large amount of time is required for the calibration operation. As a result, the total adjustment time by the spectrocolorimeter becomes long due to the time required for calibration of the white reference plate, and the productivity may decrease. Further, it is desirable to prevent a decrease in the productivity of the image forming apparatus by shortening the time required for calibrating the white reference plate in processing such as color measurement, not limited to adjustment by a spectrophotometer.

It is an object of the present invention to shorten the time required for the correction process of the color measuring device and to prevent the deterioration of the color measuring accuracy.

In order to solve the above problems, the color measuring device of the present invention can read the image formed on the paper and the reference member, and the test image formed on the paper is irradiated with a light source. It has a color measuring means that measures the reflected light of light to measure a color, and a control means that performs a correction process of the color measuring means by using the reading result of the reference member by the color measuring means. The control means selectively executes either the first correction process or the second correction process as the correction process, and in the second correction process, one of the processes executed in the first correction process. It is characterized in that the remaining processing excluding the processing of the portion is executed, and the time required for the second correction processing is shorter than the time required for the first correction processing.

According to the present invention, it is possible to shorten the time required for the correction process of the color measuring device and prevent the deterioration of the color measuring accuracy.

Configuration diagram of the image formation system. The control block diagram of the image formation system. Schematic diagram of the color measurement unit. The control block diagram of the colorimeter. Schematic block diagram of the colorimetric sensor. (A) to (e) are graphs showing a dark voltage output for a pixel and the like. The flowchart of the first correction process. The flowchart of the second correction process. (A) and (b) are flowcharts showing the measurement control of a patch train. Flow chart of color measurement control.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiment, the image forming apparatus has a color measuring device, and the color measuring device provided in the color measuring device moves a stationary test chart while securing a certain distance on the test chart. Measure the color and density of the patch image. The definition of the test chart will be described later.

FIG. 1 includes an image forming apparatus 100 that generates printed matter, a color measuring apparatus 200 that measures a printed image with a colorimeter and executes various adjustment controls, and a finisher 300 that performs post-processing such as sorting and staples. The schematic block diagram of the image formation system 10 is shown. The image forming apparatus 100 includes an operation unit 172, a paper feeding unit 110, an intermediate transfer belt 111, a fixing device 119, and a FAN 120 for fixing and cooling. An image is formed on a print medium such as paper fed from the paper feed unit 110 based on data read from a document or data received from a PC or the like, and a printed matter is generated.

The printing process method is, for example, an electrophotographic method or an inkjet recording method. FIG. 1 shows an example of an electrophotographic method, which has an image forming unit and an exposure device corresponding to the respective toners of yellow (y), magenta (m), cyan (c), and black (k). Since all of these have the same configuration, in order to simplify the explanation, reference numerals are given to the image forming unit and the exposure device corresponding to the black toner in FIG. 1, and the images corresponding to the toners of other colors are designated. The reference numeral is omitted for the forming portion. The image forming unit forms a toner image on the intermediate transfer belt 111 according to the data read from the document or the data received from a PC or the like. The details are shown below.

In the figure, the image forming unit 113k includes a photosensitive drum, a charger, and a developing device, and an exposure device 114k is provided in the vicinity of the image forming unit 113k. The photosensitive drum is a drum-shaped photosensitive member having a photosensitive layer provided on its surface, and is rotated at a predetermined process speed in the counterclockwise direction in the drawing by a drive motor (not shown). The charger charges the photosensitive layer of the rotating photosensitive drum to a uniform potential. The exposure device 114k irradiates the photosensitive layer of the charged photosensitive drum with a laser beam modulated by the scanning line image data obtained by developing the black separated color image. The exposure device 114k has a built-in rotating mirror. The laser beam is reflected by the rotating mirror and irradiates the photosensitive drum, thereby scanning the photosensitive drum in accordance with the rotation of the rotating mirror. By scanning with a laser beam, an electrostatic latent image is formed on the photosensitive layer of the photosensitive drum.

The developer develops the electrostatic latent image by adhering toner of the corresponding color to the electrostatic latent image. As a result, a toner image of the color corresponding to the surface of the photosensitive drum is formed. The surface of the photosensitive drum comes into contact with the intermediate transfer belt 111, and the toner image supported on the photosensitive drum is transferred to the intermediate transfer belt 111 (primary transfer). A full-color toner image is formed on the intermediate transfer belt 111 by superimposing and transferring the toner image from the photosensitive drum of each color.

The intermediate transfer belt 111 is a non-stretchable, endless belt member. The intermediate transfer belt 111 is supported by being hung on a tension roller 117, a belt drive roller 116, and a secondary transfer inner roller 115, which are support mechanisms. The belt drive roller 116 is rotationally driven by a drive mechanism (not shown) to rotate the intermediate transfer belt 111 in the clockwise direction in the drawing. A secondary transfer outer roller 118 is provided at a position facing the secondary transfer inner roller 115 with the intermediate transfer belt 111 interposed therebetween. The secondary transfer inner roller 115 and the secondary transfer outer roller 118 form a secondary transfer region. The intermediate transfer belt 111 is driven by the belt drive roller 116 to convey the toner image transferred from the image forming unit to the secondary transfer region. The toner image carried by the intermediate transfer belt 111 is transferred to a printing medium by a transfer electric field in the secondary transfer region to form a toner image (secondary transfer). The print medium P on which the toner image is formed is conveyed to the fixing device 119 to fix the toner image, and a printed matter is generated. The printed matter discharged from the fixing device 119 is cooled by the FAN 120 for fixing and cooling, and then conveyed to the color measuring device 200.

The color measuring device 200 is a device for adjusting the color and density of the output image of the image forming device 100. In order to adjust the color and density, it is necessary to print the image for adjustment on paper by the image forming apparatus 100 and output it separately from the normal printed matter output by the user. The printed matter on which the image for adjustment is printed is hereinafter referred to as a test chart, and the image on the test chart is referred to as a chart image. The chart image is an image in which a large number of patch images printed in a predetermined size are arranged. The patch image is a test image test image for adjusting the image quality of the image formed by the image forming apparatus 100, and is composed of various densities and colors. The color measuring device 200 measures a patch image such as a color patch or a density patch output by the image forming device 100. The measurement result is used for correction of the color measuring device, for example, calibration, and various adjustments of the image forming device 100. Further, the color measuring device 200 can be operated in a plurality of adjustment modes according to the parameters to be corrected, and can be operated in, for example, an adjustment mode by generating a color profile, a density gradation adjustment mode, and the like. Further, a temperature sensor S for detecting the temperature of the color measuring device 200 is provided in the color measuring device 200.

When the test chart is output from the image forming apparatus 100, the color measuring device 200 transfers the flag 210 from the normal printed matter path to the color measuring unit 202 so as to convey the test chart to the color measuring unit 202. Switch to the transport route to reach. When the measurement of the test chart by the color measuring unit is completed, the color measuring device 200 sets the flag 211 from the path through which the normal printed matter is conveyed to the output tray 201 so as to output the test chart to the output tray 201. Switch to the transport route to reach. As a result, the test chart is transferred. The finisher 300 performs predetermined post-processing, for example, sorting and staple processing specified by the user on the ordinary printed matter discharged from the color measuring device 200, and conveys the printed matter to the output tray 310.

<Electric hardware configuration>
FIG. 2 shows a control block of an image forming system. In the figure, the printer control unit 150 of the image forming apparatus 100 includes a CPU 151, a ROM 152, a RAM 153, and an ASIC 154. The CPU 151 expands the control program stored in the ROM 152 into the RAM 153 and executes an instruction. The ASIC 154 is connected to various loads such as an image forming unit and a paper feed transport unit, and executes various controls by commands from the CPU 151. The CPU 151 communicates with the CPU 171 of the controller control unit 170 that controls the operation unit 172, and controls the printer based on the input information input through the operation unit 172 of the controller control unit 170.

Further, the CPU 151 is provided with a communication IF 161 for communicating with the color measuring device 200 and the finisher 300 connected to the downstream side. The communication line connected to the downstream device via the communication IF 161 includes a serial signal line and a parallel signal line including a power supply remote signal. Information is sent and received between devices using serial data via a serial signal line. In addition, it is possible to start the power supply of the downstream device by transmitting the power supply remote signal. The CPU 151 controls the CPUs 251 and 351 described later through the communication IF 161 as needed.

The color measurement control unit 250 of the color measurement device 200 has a CPU 251, a ROM 252, a RAM 253, and an ASIC 254, similarly to the image forming device 100. The CPU 251 expands the control program stored in the ROM 252 into the RAM 253 and executes an instruction. The ASIC 254 is connected to each load such as a paper carrier and executes various controls according to a command from the CPU 251. Further, the CPU 251 communicates with the image forming apparatus 100 and the finisher 300 through the communication IF 261.

The finisher control unit 350 of the finisher 300 has a CPU 351 and a ROM 352, a RAM 353, and an ASIC 354 like the image forming apparatus 100. The CPU 351 expands the control program stored in the ROM 352 into the RAM 353 and executes an instruction. The ASIC 354 is connected to each load such as a paper transport unit, a punch processing unit, and a staple processing unit, and executes control by a command from the CPU 351. Further, the CPU 351 communicates with the image forming apparatus 100 and the color measuring apparatus 200 through the communication IF 361.

<Color measurement unit configuration>
FIG. 3 is a schematic configuration diagram of the color measuring unit 202. The color measurement sensor 2001a is held by the color measurement sensor holder 2001b, and the color measurement sensor holder 2001b is connected to a rail 2006 for moving in the direction described as the scanning direction. The color measurement sensor 2001a and the color measurement sensor holder 2001b are collectively referred to as a color measurement carriage 2001. When the test chart is transported into the color measuring unit 202, the color measuring carriage 2001 is retracted out of the test chart transport path, and specifically, the color measuring carriage 2001 is arranged on the white reference plate 2002. In order to correct reading unevenness due to variations in the characteristics of the optical system, the light emitting element, and the image pickup element included in the color measuring unit 202, shading correction and the like are performed using the reading result of the white reference member. In this embodiment, the white reference plate 2002 is used as the reference member, but for example, a white reference document can be used as the reference member.

Since the color measurement carriage 2001 is moved onto the white reference plate 2002, a position sensor 2005a for detecting the position of the color measurement sensor 2001a is arranged in the color measurement unit 202. The color measuring carriage 2001 moves on the white reference plate 2002 by moving a predetermined distance from the timing when the position sensor 2005a detects the color measuring sensor 2001a and stopping. The test image is read by the color measurement sensor 2001a with this position where the color measurement sensor 2001a can read the white reference plate 2002 as a reference position. The color measuring carriage 2001 is made capable of moving the rail 2006 by the motor 204 shown in FIG. 4 described later.

The test chart is represented by reference numeral C in FIG. 3, and is configured by arranging a plurality of quadrangular patch images of a predetermined size in a two-dimensional array. The back surface of the test chart is supported by the backing member 2003. Hereinafter, the operation of the color measurement carriage 2001 and the test chart transfer control during the color measurement operation will be described. The test chart is stopped at a predetermined position in the color measuring unit 202 by the transport rollers 2004a and 2004b. Specifically, the center position of the leading patch row in the paper transport direction is a position that matches the reading center position of the color measurement sensor 2001a.

The patch first detected by the color measurement carriage 2001 is a solid black patch image called a trigger patch, which is the second patch or later (represented by reference numerals P1, P2 ... In FIG. 3) from the detection timing of the trigger patch. Control the patch detection timing. The color measurement sensor 2001a has a window surface on the chart image side, and is arranged so as to be able to detect the patch image on the test chart. The color measurement carriage 2001 moves the color measurement sensor 2001a to a readable position on the test chart. After finishing the measurement of the patch row of the first row by the color measuring sensor 2001a, the color measuring carriage 2001 moves in the scanning direction indicated by D1 in FIG. 3 until the position sensor 2005b is detected. After detecting the position sensor 2005b, the color measuring carriage 2001 moves a predetermined distance and stops.

After that, the test chart is conveyed by the conveying rollers 2004a and 2004b in the moving distance corresponding to the length of one patch in the paper conveying direction indicated by D2 in the drawing. The color measuring carriage 2001 moves in the direction opposite to the scanning direction D1 shown in FIG. 3 and starts the measurement of the patch row of the second row. For the patch rows after the third row, the measurement is basically executed by repeating the same operation as the measurement operations of the first row and the second row.

<Hardware configuration of color measuring device>
FIG. 4 shows a control block diagram of the color measuring device 200. As described with reference to FIG. 2, the CPU 251 executes the process by executing the program stored in the ROM 252. The RAM 253 is a memory for temporarily storing the calculation result during the program processing. The ASIC 254 is connected to the motor 204, the motor 205, PI206, and 207, and is configured to control each load. Although FIG. 4 shows only the load related to the color measuring unit 202, it is actually connected to other loads (not shown). For example, a motor (not shown) for controlling each transport roller in the color measuring device 200, an SL, a reflection type photo sensor, and the like are connected to the ASIC 254.

The CPU 251 communicates with the image forming apparatus 100 and the like through the communication IF 261. Further, the CPU 251 communicates with the microcomputer of the color measurement sensor 2001a through the communication IF262 by a communication method such as SPI communication and controls the CPU 251. Here, the motor 204 is a driving means for moving the color measuring carriage 2001 along the rail 2006. The motor 205 is a driving means for driving the transport rollers 2004a and 2004b. PI206 indicates a position sensor 2005a, and PI207 indicates a position sensor 2005b.

<Structure of color measurement sensor>
FIG. 5 shows an explanatory diagram of a schematic configuration of the color measurement sensor 2001a controlled by the CPU 251. In this example, a spectroscopic sensor was used as the color measurement sensor 2001a. The color measurement sensor 2001a has a CPU 24, a light source 20 for irradiating the patch on the test chart with light, and a light guide 21 for guiding the light from the light source 20 to the patch. The reflected light from the patch is incident on the diffraction grating 22 by the light guide 21. The diffraction grating 22 disperses the light incident from the light guide 21, and the dispersed light is incident on the line sensors 23-1 to 23-n. The light source 20 is, for example, a white LED, and the line sensor 23 is suitable for a CCD sensor or a CMOS sensor. The CPU 24 expands the program stored in the ROM 25 into the RAM 26 and executes it to control the light source 20 and the line sensor 23. Further, the CPU 24 executes various arithmetic processes on the signal received by the line sensor to calculate the spectral reflectance.

6 (a) to 6 (d) are graphs showing the dark voltage output for a pixel, the dark voltage output for a wavelength, and the reflectance for a wavelength, which are obtained by calculating the spectral reflectance. In FIGS. 6A to 6C, the horizontal axis of the graph represents the pixel numbers (1 to N), and the vertical axis represents the output voltage. In FIG. 6D, the horizontal axis of the graph indicates the wavelength (400 to 700 nm), and the vertical axis indicates the output voltage. FIG. 6E is a graph showing the reflectance with respect to the wavelength. The horizontal axis of the graph shows the wavelength (400 to 700 nm), and the vertical axis shows the reflectance.

The CPU 24 measures the dark voltage of the line sensor 23 before causing the light source 20 to emit light. The result is shown in FIG. 6 (a). As shown, the dark voltage values and their changes are both small. In FIG. 6A, the maximum value of the dark voltage is shown as Vdark. Next, the CPU 24 executes a calibration operation using the reading result of the white reference plate 2002. As a calibration operation, the light intensity adjustment is first executed. The light intensity adjustment is an adjustment that matches the maximum value (Vpeak) of the peak output value of the line sensor with the target value (Vtar). The output value of the line sensor at the time of calibration is shown in FIG. 6 (b). This adjustment is performed in order to correct the life of the light source 20, the dirt on the window surface of the color measurement sensor 2001, the fluctuation of the output of the line sensor 23 due to the temperature change of the sensor 2001, and the like. As shown in FIG. 6B, two peaks appear in the line sensor output value, and the peak having the higher output value is shown as Vpeak in the figure.

Next, the spectral data of the white reference plate 2002 is measured by the adjusted amount of light. The result is shown in FIG. 6 (c). The CPU 24 calculates the amount of positional deviation α of the light incident on the line sensor 23 from the measurement data shown by the solid line in FIG. 6 (c). The misalignment amount α is calculated by comparing with the spectral data (FIG. 6 (c): broken line) of the white reference plate measured at the time of shipment from the factory of the color measurement sensor 2001. The spectral data of the white reference plate measured at the time of shipment from the factory is referred to as the initial white reference plate data. The initial white reference plate data is stored in the ROM 25.

The CPU 24 corrects this positional deviation amount α and converts the output value for each pixel into an output value for each wavelength. This correction is referred to as distortion correction. The result is shown in FIG. 6 (d). Since the conversion is performed in this way, unlike FIGS. 6A to 6C, the horizontal axis of FIG. 6D is not a pixel but a wavelength. Hereinafter, converting the output value for each pixel into the output value for each wavelength will be referred to as pixel wavelength conversion. After that, the CPU 24 actually measures the patch image, executes dark voltage correction and pixel wavelength conversion processing on the measured data, and calculates the spectral reflectance by comparing with the spectral data of the white reference plate. The result is shown in FIG. 6 (e).
The formula of patch spectral reflectance (Rp) is shown below.
Rp = (patch spectroscopic data / white reference plate spectroscopic data) × reference plate reflectance ... Equation 1
The reference plate reflectance is data obtained by measuring the reflectance of the white reference plate with a general measuring instrument such as a commercially available measuring instrument, and in the present embodiment, the reference plate reflectance is stored in the ROM 25.

FIG. 7 is a flowchart of the white reference plate calibration operation executed by the CPU 24, which is an example of the correction process of the color measuring device 200. Hereinafter, the process of adjusting the amount of light shown in this figure will be referred to as the first correction process. The CPU 24 performs a color measurement operation when there is an input instructing color measurement from the user through the operation unit 172, or when the color measurement device 200 is started. In the color measurement operation, the transfer control and the initial positioning control of the test chart, which will be described later, are performed, and the first correction process is executed. In the first correction process, the dark voltage correction (S100), the light amount adjustment (S101), the standby (S102), the white reference plate measurement (S103), and the white reference plate correction (S104) are executed in this order. This order is the same as the order in the description in FIGS. 6A to 6E.

The CPU 24 performs dark voltage correction (S100), adjusts the amount of light (S101), and then stands by (S102). This standby time indicates the time until the light amount of the light source stabilizes after the light amount adjustment is performed. Since the time until the amount of light stabilizes correlates with the time until the temperature of the light source 20 stabilizes, it takes a very long time. The CPU 24 performs the white reference plate measurement (S103) after the standby, and then performs the white reference plate correction (S104). The white reference plate correction referred to here refers to distortion correction.

FIG. 8 shows a flowchart showing the second correction process of the white reference plate calibration operation. In this case, the CPU 24 executes the white reference plate measurement (S200) and performs the white reference plate correction (S201) without executing the dark current correction, the light amount adjustment, and the standby shown in S100 to S102 of FIG. 7. In the second correction process, the rest of the processes executed in the first correction process (in this example, dark current correction, light intensity adjustment, and standby process) are executed, and the second correction process is performed. The time required for the processing is shorter than the time required for the first correction processing. In the second correction process, if the time is shorter than that of the first correction process, a process not included in the first correction process may be executed. For example, a simple light amount adjustment process may be performed, which is inferior in accuracy to the light amount adjustment in S101 of FIG. 7, but has a shortened processing time. Alternatively, another process different from the light amount adjustment process in the first correction process and having a short processing time can be performed.

In the second correction process, since there is no waiting time for adjusting the amount of light and stabilizing the amount of light thereafter, the measurement time is shortened and the calibration operation can be executed very quickly. Further, in the color measurement control by the color measuring device 200, a large number of patch images may be formed on the test chart and the measurement may be executed over a plurality of images. In such a case, the time required for measurement may be, for example, 5 minutes or more. As a result, it is necessary to perform white reference plate calibration during the measurement in order to prevent the accuracy of the measured value from being lowered due to the influence of the change in the ambient temperature of the color measurement sensor 2001a.

In the present embodiment, the second correction process is performed every time a predetermined process is performed after the color measurement is started. The details will be described later. The second correction process may be performed after the first predetermined time has elapsed (for example, after 5 minutes or more have elapsed) after the color measurement is started. Alternatively, when the temperature of the color measuring device 200 is detected by the temperature sensor S and the difference from the temperature at the time of the first correction processing (or the temperature at the time of the previous second correction processing) exceeds a predetermined temperature difference, the second The correction process may be performed. By performing the second correction process in this way, it is possible to suppress the influence of the temperature change and correct the color measuring device 200 without performing time-consuming light amount adjustment. Therefore, it is possible to prevent a decrease in the color measurement accuracy of the color measuring device 200 while suppressing the influence on the time required for the measurement to be extremely small.

The main purpose of adjusting the amount of light is to adjust the output decrease of the line sensor 23 due to the stain on the window surface of the color measurement sensor 2001a. Therefore, by performing the first correction process at the start of color measurement to adjust the amount of light, it is possible to suppress a decrease in measurement accuracy due to a decrease in the output of the line sensor 23. On the other hand, if the measurement time is 5 minutes or more after the start of color measurement, the output of the line sensor 23 may change due to the fluctuation of the ambient temperature of the color measurement sensor 2001a. With regard to this, by executing the second correction process, it is possible to suppress a decrease in accuracy of the measured value due to the influence of such fluctuations in the ambient temperature. This is because the white reference plate calibration is executed, and the measuring device is corrected so as to suppress the deterioration of the accuracy of the measured value due to the influence of the change in the ambient temperature of the color measuring sensor 2001a. In the short time of about 5 minutes described above, the influence of stains on the window surface and the like is small, so that it is not necessary to adjust the amount of light. Therefore, even in the second correction process in which the light amount adjustment or the like is not performed, it is possible to prevent the measurement accuracy of the color measuring device 200 from deteriorating.

As described above, the CPU 24 selectively determines whether the color measuring device 200 performs the first correction process for adjusting the light amount or the second correction process for not adjusting the light amount. In the present embodiment, the CPU 24 executes the first correction process at the time of starting the color measuring device 200 or when there is an input instructing calibration from the user. When the elapsed time from the first correction process exceeds the above-mentioned first predetermined time, the second correction process is performed. Further, in the present embodiment, the CPU 24 performs the second correction process again when the elapsed time from the second correction process exceeds the second predetermined time. This is because the temperature may change even after the second correction process is performed. The second predetermined time may be the same as the first predetermined time, but is preferably longer than the first predetermined time. This is because the temperature usually converges to the saturation temperature with the passage of time, and the fluctuation of the temperature with respect to the time becomes small.

On the other hand, if a long time has passed since the first correction process including the light amount adjustment was performed, the stain on the white reference plate 2002 and the stain on the window surface of the color measurement sensor 2001a may not be negligible. Therefore, the CPU 24 may re-execute the first correction process after the first correction process is performed and then the third predetermined time longer than the first predetermined time and the second predetermined time described above has elapsed. .. From the above, sufficient measurement accuracy can be obtained even by performing a simple calibration in which the white reference plate measurement and distortion correction (white reference plate correction) are performed without adjusting the amount of light by the second correction process. Be done.

Hereinafter, the color measuring operation of the color measuring device 200 in the present embodiment will be described. In the color measurement operation, the color measurement carriage 2001 shown in FIG. 3 scans on the test chart and always returns to the position of the white reference plate during this scan. Therefore, it is easy to perform calibration at the timing when the color measuring carriage 2001 returns to the position of the white reference plate. The test chart contains multiple patch columns. When the color measurement control is executed at the time of starting the color measurement device 200 or the like, the color measurement carriage 2001 measures the patch row of the first row of the test chart. A flowchart showing the measurement control in this case is shown in FIG. 9A. Further, the measurement control of the patch row of the first row is described as the first scanning control.

In the first scanning control, the CPU 251 of the color measurement control unit 250 sets the rotation direction of the motor 204 to the direction D1 for scanning the patch row of the first row (S300). This direction D1 is the direction shown as D1 in FIG. 3 described above. Next, the CPU 251 actually drives the motor 204 to start scanning (S301). The CPU 251 determines whether or not the trigger patch is detected (S302), and if the trigger patch is not detected (S302: No), executes S302 again. When the trigger patch is detected (S302: Yes), the CPU 251 determines whether or not a predetermined time Ta has elapsed after the trigger patch is detected (S303). If Ta has not elapsed (S303: No), the CPU 251 executes S303 again. When Ta has elapsed (S303: Yes), the CPU 251 executes the patch measurement a (S304).

The CPU 251 determines whether or not a predetermined time Tb has elapsed from the timing of starting patch measurement in S304 (S305), and if the predetermined time Tb has not elapsed (S305: No), executes S305 again. do. When the predetermined time Tb has elapsed (S305: Yes), the CPU 251 executes the patch measurement b (S306). The patch measurement a shows the measurement of the first patch image after the trigger patch, and the patch measurement b shows the measurement of the patch image after that.

Next, the CPU 251 determines whether or not the measurement of N patches has been completed, with the total number of patches in the first column being N (S307), and when the measurement of N patches has not been completed (S307). : No), S307 is executed again. When the measurement of N patches is completed (S307: Yes), the CPU 251 determines whether or not the position sensor 2005b is detected (S308). When the position sensor 2005b is not detected (S308: No), the CPU 251 executes S308 again. When the position sensor 2005b is detected (S308: Yes), the CPU 251 moves the color measurement carriage 2001 by a predetermined amount and then stops it (S309). This completes the first scan control.

Next, FIG. 9B shows a flowchart showing the measurement control of the patch row of the second row of the test chart by the color measurement carriage 2001 when the color measurement control is executed. Hereinafter, this measurement control will be referred to as a second scanning control. The CPU 251 sets the rotation direction of the motor 204 to D2, which is the direction opposite to D1 (S400). Since the operations from S401 to S407 are the same as those of S301 to S307 of the operation flow of the first scanning control described with reference to FIG. 9A, the description thereof will be omitted. After executing S407, the CPU 251 determines whether or not the position sensor 2005a is detected (S408), and if the position sensor 2005a is not detected (S408: No), executes S408 again. When the position sensor 2005a is detected (S408: Yes), the CPU 251 stops the color measurement carriage 2001 after moving a predetermined amount (S409). The above is the operation flow of the second scanning control.

FIG. 10 shows a flowchart showing a process executed by the CPU 251 during color measurement control. When a color measurement control command is input by the user through the operation unit 172 of the image forming apparatus 100 or a PC (not shown), the image forming apparatus 100 outputs a test chart in which a plurality of predetermined color patch images are formed. .. In the color measuring device 200, the test chart is conveyed to a predetermined position of the color measuring unit 202 under the control of the CPU 251 (S500). Next, the CPU 251 executes the initial positioning control of the color measurement carriage 2001 (S501).

The initial positioning control is executed by grasping the current position of the color measuring carriage 2001 based on the signal outputs of the position sensors 2005a and 2005b. When the position sensor 2005a is detected, the color measuring carriage 2001 is moved in the direction of the position sensor 2005b until the position sensor 2005a is no longer detected. After that, the position sensor 2005a is detected again by reversing the rotation direction of the motor 204. After the position sensor 2005a is detected again, the color measuring carriage 2001 is moved by a predetermined moving distance and stopped. This makes it possible to move the color measurement carriage 2001 on the white reference plate 2002 in a predetermined manner.

Next, the CPU 251 executes the first correction process (S502). As a result, the color measurement sensor 2001a completes the calibration including the light intensity adjustment. The CPU 251 executes the first scan control (S503). Next, the CPU 251 drives and controls the motor 205 in order to move the test chart by a predetermined distance (S504). This predetermined distance is a distance corresponding to the length of the patch in the transport direction. This makes it possible to match the position of the second row with the detection position of the color measurement sensor 2001a. The CPU 251 executes the second scanning control (S505). Here, the color measurement carriage 2001 is moving directly above the white reference plate 2002. The CPU 251 executes the second correction process after executing the first scan control and the second scan control (S506).

As described above, in the present embodiment, the second correction process is executed after the predetermined process, that is, the first scan control and the second scan control is executed. Since the first scan control and the second scan control are performed in a short time and do not exceed 5 minutes, the temperature change occurring during that time is small. Even when a temperature change occurs, the second correction process can be performed to correct the effect, so that the influence of the temperature change of the color measuring device 200 can be suppressed and the deterioration of the color measuring accuracy can be prevented. After that, the CPU 251 determines whether the measurement of all the patch rows on the test chart is completed (S507).

When the measurement is not completed (S507: No), the CPU 251 moves the test chart by a predetermined distance (S508), and executes S503 again. The moving distance here is the same as the moving distance in S504. When the CPU 251 determines that the measurement is completed (S507: Yes), the CPU 251 discharges the test chart to the output tray 201 (S509). This completes the color measurement control. In this way, by separating the processing content between the white reference plate correction process before patch measurement and the white reference plate correction process after patch measurement, stable measurement accuracy is suppressed while suppressing an increase in the time required for color measurement control. The color measurement operation that can realize the above can be executed.

In the example shown in FIG. 10, since the time required for the second correction process is short, the patch sequence of the test chart is performed by performing the reciprocating operation of the color measurement carriage 2001 (that is, the first scan control and the second scan control). The second correction process is executed every time two columns are measured. However, the present invention is not limited to this. That is, the second correction process may be executed every time an arbitrary predetermined number of patch sequences are measured. This makes it possible to shorten the time required for color measurement control.

The present invention is not limited to the example shown in FIG. As described above, as another form, the second correction process may be performed when the elapsed time from the start of color measurement exceeds the first predetermined time. Alternatively, the second correction process may be performed when the temperature detected by the temperature sensor S exceeds a predetermined temperature difference from the temperature at the time of the first correction process. Further, the second correction process may be performed again after the second correction process is performed. In this case, the second and subsequent correction processes may be executed when the second predetermined time, which is longer than the first predetermined time, is exceeded.

Further, if a long time has passed since the first correction process was performed, the influence of stains on the window surface and the like may not be negligible. Therefore, after the first correction process is performed, the first correction process may be executed again after the first predetermined time and the third predetermined time longer than the second predetermined time have elapsed.

As described above, according to the present embodiment, it is possible to measure the patch image with high accuracy without increasing the time required for adjusting the color measuring device. In particular, even when performing adjustment control that requires a long time such as measuring a large number of patch images, it is possible to suppress the time required for adjustment and prevent deterioration of color measurement accuracy due to temperature changes.

Claims (11)

A color measuring means capable of reading an image formed on a sheet of paper and a reference member, and measuring the reflected light of light emitted from a light source on the test image formed on the sheet of paper to measure a color. ,
It has a control means for performing correction processing of the color measuring means by using the reading result of the reference member by the color measuring means.
The control means selectively executes either a first correction process or a second correction process as the correction process, and in the second correction process, among the processes executed in the first correction process. The remaining processing except for a part of the processing is executed, and the time required for the second correction processing is shorter than the time required for the first correction processing.
Color measuring device. The partial processing is characterized in that it is a light amount adjusting processing of the color measuring means.
The color measuring device according to claim 1. The control means is characterized in that the first correction process is executed when the color measuring device is activated.
The color measuring device according to claim 1 or 2. The control means is characterized in that the first correction process is executed when an input instructing correction of the color measuring device is received from a user.
The color measuring device according to any one of claims 1 to 3. The test image includes a plurality of patch sequences composed of a plurality of patch images, and the control means measures each time a predetermined number of patch sequences of the test image are measured after the first correction process is executed. The color measuring device according to any one of claims 1 to 3, wherein the second correction process is executed. The control means is characterized in that the second correction process is executed after the lapse of a first predetermined time after the first correction process is executed.
The color measuring device according to any one of claims 1 to 5. The control means is characterized in that the second correction process is executed and then the second correction process is executed after a second predetermined time longer than the first predetermined time has elapsed.
The color measuring device according to claim 6. The control means is characterized in that after the first correction process is executed, the first correction process is executed again after the lapse of the first predetermined time and the third predetermined time longer than the second predetermined time. ,
The color measuring device according to claim 7. The control means performs the second correction process when the difference between the temperature detected by the temperature sensor in the color measuring device and the temperature detected when the first correction process is executed exceeds a predetermined temperature difference. Characterized by doing,
The color measuring device according to any one of claims 1 to 8. The test image includes a plurality of patch sequences composed of a plurality of patch images.
A transporting means for transporting the paper on which the test image is formed to the color measuring means, and a transporting means.
The color measuring means further includes a moving means for moving the patch train between a readable position and a readable position of the reference member.
The control means reads the patch sequence of the test image by the color measuring means with the position where the color measuring means can read the reference member as a reference position.
The color measuring device according to any one of claims 1 to 9, wherein the second correction process is executed when the color measuring means is in the reference position. Image forming means for forming an image and
A color measuring means capable of reading an image formed on a sheet of paper and a reference member, and measuring the reflected light of light emitted from a light source on the test image formed on the sheet of paper to measure a color. ,
The correction processing of the color measuring means is performed using the reading result of the reference member by the color measuring means, and the image of the image forming means is performed based on the color measuring result of the color measuring means corrected by the correction processing. It has a control means for controlling the formation conditions, and has.
The control means selectively executes either a first correction process or a second correction process as the correction process, and in the second correction process, among the processes executed in the first correction process. The remaining processing except for a part of the processing is executed, and the time required for the second correction processing is shorter than the time required for the first correction processing.
Image forming device.

Images