JP7027847B2 - Reading device, image forming device and reading method - Google Patents

Description

The present invention relates to a reading device, an image forming device and a reading method.

In an image forming apparatus or the like that forms an image on the conveyed paper, the position where the image is formed on the paper may be displaced due to the variation in the paper conveying position.

Therefore, there is known an image forming apparatus that detects the end position in the main scanning direction, that is, the width direction of the paper being conveyed, and controls the image writing position in the image forming portion based on the detection result (for example, patent). See Document 1). The image forming apparatus according to Patent Document 1 sequentially switches and turns on a plurality of light sources having different wavelengths, and detects the position of the edge of the paper in the width direction by using the reflected light from the paper that matches the color of the paper. is doing.

However, since there are innumerable types of paper, depending on the paper to be detected, sufficient reflected light may not be obtained by using any of the provided light sources, and the edge position of the paper may not be detected. there were.

The present invention has been made in view of the above points, and an object of the present invention is to read the edge position of an object without being restricted by the type of the object such as paper.

The reading device according to one aspect of the disclosed technique has a pixel array in which a plurality of pixels for outputting a detection signal are arranged in a predetermined direction, a sensor unit arranged so as to be able to read the edge of an object, and the predetermined one. At each position in the direction, the adder that adds the output of the pixel of the pixel array, the edge position detector that detects the edge position of the object based on the output of the adder, and the output of the adder It has a pixel number detection unit that detects the number of pixels that is equal to or greater than a predetermined threshold, and the edge position detection unit has a pixel number threshold in which the pixel number detected by the pixel number detection unit is within a predetermined range. It is characterized in that the edge of the object is detected when the value does not fall below .

According to the embodiment of the present invention, the edge position of the object can be read without being restricted by the type of the object.

It is a figure which illustrates the structure of the image forming apparatus which has the edge position reading apparatus of 1st Embodiment. It is a figure which illustrates the structure of the sensor part in the edge position reading apparatus of 1st Embodiment. It is a figure which illustrates the positional relationship between a sensor part and a paper in the edge position reading apparatus of 1st Embodiment. It is a block diagram which illustrates the hardware composition of the edge position reading apparatus of 1st Embodiment. It is a block diagram which illustrates the functional structure of the control apparatus in the edge position reading apparatus of 1st Embodiment. It is a flowchart which illustrates the processing of the control apparatus in the edge position reading apparatus of 1st Embodiment. It is a figure explaining the 1st example of the data read by the conventional edge position reading apparatus. It is a figure explaining the 2nd example of the data read by the conventional edge position reading apparatus. It is a figure explaining the 3rd example of the data read by the conventional edge position reading apparatus. It is a figure which illustrates the data read by the edge position reading apparatus of 1st Embodiment. It is a figure explaining the influence of the reflected light of the background area in an edge position reading apparatus. It is a figure explaining the state of reading the edge position by the edge position reading apparatus of 2nd Embodiment. It is a figure explaining the state of reading the edge position by the edge position reading apparatus of 3rd Embodiment. It is a figure explaining the state of reading the edge position by the edge position reading apparatus of 4th Embodiment. It is a figure explaining the inclination of the paper to be conveyed. It is a figure which illustrates the data read by the edge position reading apparatus of 5th Embodiment. It is a block diagram which illustrates the functional structure of the control apparatus in the edge position reading apparatus of 5th Embodiment. It is a figure which illustrates the correction of the position and the inclination of the paper based on the output of the edge position reading apparatus of 5th Embodiment. It is a block diagram which illustrates the functional structure of the control apparatus in the edge position reading apparatus of 6th Embodiment. It is a figure which shows the 1st example of the data read by the edge position reading apparatus of 6th Embodiment. It is a figure which shows the 2nd example of the data read by the edge position reading apparatus of 6th Embodiment. It is a figure explaining an example of the instability of the output value of a pixel due to the type of paper. It is a block diagram which illustrates the functional structure of the control apparatus in the edge position reading apparatus of 7th Embodiment. It is a figure explaining an example of the effect of the width direction moving average processing. It is a figure explaining an example of the side effect of the width direction moving average processing. It is a block diagram which illustrates the functional structure of the control apparatus in the edge position reading apparatus of 8th Embodiment.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components may be designated by the same reference numerals and duplicate explanations may be omitted.

[First Embodiment]
FIG. 1 is a diagram illustrating the configuration of an image forming apparatus 500 having the edge position reading apparatus 100 of the first embodiment.

An automatic document feeder 1 having a document table 2 is provided above the image forming apparatus 500. When the print key is pressed, the bundle of documents placed on the platen 2 is fed to a predetermined position on the contact glass 5 by the feeding roller 3 and the feeding belt 4 in order from the bottom document. ..

The scanner unit 6 optically reads the document fed on the contact glass 5 and acquires image data. Based on the image data acquired by the scanner unit 6, the writing unit 7 irradiates the surface of the photoconductor 8 with a laser beam to form an electrostatic latent image. The electrostatic latent image formed on the surface of the photoconductor 8 is made into a toner image by the developing unit 9.

The paper P stored in the paper trays 11, 12, and 13 is fed by the paper feed devices 14, 15, and 16, respectively, and is conveyed by the transfer unit 10. On the paper P, the toner image formed on the surface of the photoconductor 8 is transferred by the image forming unit 22 between the photoconductor 8 and the transfer unit 17.

The paper P on which the toner image is transferred is conveyed to the fixing unit 18, heated and pressurized, and the toner image is fixed on the surface. The paper P that has passed through the fixing unit 18 is discharged to the outside of the machine by the paper ejection unit 19.

In the case of double-sided printing, the paper P that has passed through the fixing unit 18 is stocked in the double-sided paper feed transfer unit 21 after the transfer path is switched by the branch claw 20. The paper P stocked in the double-sided paper feed transfer unit 21 is inverted and conveyed toward the photoconductor 8 again, and is discharged to the outside of the machine after a toner image is formed on the back surface.

The image forming apparatus 500 has a paper edge position reading device 100 in the transport path of the paper P. The edge position reading device 100 reads the edge position of the conveyed paper P and grasps the conveyed position of the paper P. By adjusting the image formation position according to the transport position of the paper P, the image position shift on the paper P is prevented.

Next, an example of the configuration of the sensor unit 210 included in the paper edge position reading device 100 of the present embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating an outline of the configuration of the sensor unit 210. (A) is a side view, and (b) is a plan view. In FIG. 2, the thick black arrow indicates the transport direction of the paper P, and the thick white arrow represents the direction intersecting the transport direction of the paper P, that is, the width direction. The width direction is a typical example of the "predetermined direction".

The sensor unit 210 has a light source unit 211 and a light receiving unit 212.

The light source unit 211 irradiates one end of the conveyed paper P in the width direction, that is, a region through which the edge passes, with a long line of light in the width direction. The light source unit 211 includes an LED (Light Emitting Diode) array 211d and a substrate 211a. A plurality of LEDs that emit light having a wide wavelength band close to white light are arranged in the width direction on the substrate 211a.

However, the light source unit 211 is not limited to the above configuration, and LEDs of each color of red, green, and blue are turned on at the same time, light of each color is mixed, and light having a wide wavelength band close to white light is irradiated. You may. Further, the configuration may include one element that irradiates a long line of light in the width direction, such as a fluorescent tube. According to the fluorescent tube, it is possible to irradiate white light having a uniform brightness in the width direction.

Furthermore, using a light guide member whose width direction is the longitudinal direction, white, red, green, and blue LEDs arranged at both ends of the light guide member are turned on and passed through the light guide member. You may irradiate the light of the shape. The light guide member can irradiate light having uniform brightness in the width direction. In addition to these, the light source unit 211 may have a configuration different from the above example as long as it can irradiate line-shaped light in the width direction. Further, a light guide lens may be provided to efficiently guide the light from the LED array 211d to the region where the edge in the width direction of the conveyed paper P passes.

The light receiving unit 212 includes a substrate 212a, a pixel array 212r that receives red light, a pixel array 212g that receives green light, and a pixel array 212b that receives blue light.

The pixel array is a photoelectric conversion element that converts an optical signal into an electric signal, for example, an element in which PDs (Photo Diodes) are arranged in an array in the width direction. One photoelectric conversion element corresponds to one pixel and outputs an electric signal according to the amount of light received. "Electrical signal according to the amount of received light" is a typical example of a detection signal. The pixel array outputs an electric signal of one line of pixels.

As shown in the figure, the pixel array 212r, the pixel array 212g, and the pixel array 212b are arranged side by side in the transport direction with the width direction and the pixel arrangement direction substantially parallel to each other.

The pixel array 212r that receives red light has a red color filter in front of the light receiving surface, and receives red light that has passed through the color filter. The red color filter passes light in the red wavelength band and absorbs or reflects light in other wavelength bands. Similarly, the pixel array 212g and the pixel array 212b have green and blue color filters, respectively, and receive light in the green and blue wavelength bands. A color filter that allows red, green, or blue light to pass through is a typical example of "red, green, or blue color selection means."

A CCD (Charge Coupled Device), CMOS (Complementary Metal-Oxide-Semiconductor), or the like may be used for the pixel array. Further, the light receiving unit 212 may be configured by using a CCD or CMOS area sensor having a two-dimensional pixel array. Further, in order to increase the light collection efficiency of the light receiving unit 212, a lens array such as a rod lens array for guiding the light reflected by the paper P to the pixel array may be provided.

The sensor unit 210 irradiates a region through which the widthwise edge of the paper P passes from the light source unit 211 with light close to linear white light. Then, the light receiving unit 212 receives the reflected light from the region through which the edge in the width direction of the paper P passes. Of the reflected light, the red light is received by the pixel array 212r, the green light is received by the pixel array 212g, and the blue light is received by the pixel array 212b.

When only monochromatic light is irradiated and the reflected light is received, the irradiation light may be absorbed by the paper P depending on the color of the paper P, and sufficient reflected light may not be obtained. By irradiating light close to white light and receiving red, green, and blue light as in the present embodiment, it is possible to read the edge position as compared with the case where only monochromatic light is used. The color and type of paper P can be increased.

However, the configuration for obtaining such an effect is not limited to the above. For example, three LED arrays of red, green, and blue may be used as a light source, and each LED array may be sequentially lit while receiving light of each color in a time-division manner by one pixel array. Also with this configuration, the colors and types of the paper P can be increased in the same manner as described above.

Further, the sensor unit 210 may be configured by a CIS (Contact Image Sensor). The CIS is an image sensor in which a light receiving unit, a light source unit, and a rod lens array (equal magnification imaging system lens) are integrated. By using CIS, for example, it is possible to approach the surface of the paper and read the edge position compactly.

FIG. 3 shows an example of the positional relationship between the sensor unit 210 and the paper P in the edge position reading device 100. In FIG. 3, the paper P is conveyed in the direction of the thick black arrow. The sensor unit 210 is provided so as to straddle one end, that is, the edge of the paper P in the width direction indicated by the white arrow. The position in the width direction of the edge of the paper P on which the sensor unit 210 straddles is read by the sensor unit 210. The “sensor unit 210 provided so as to straddle one end of the paper P, that is, the edge in the width direction” is a typical example of the “sensor unit readablely arranged to read the edge of the object”.

Next, the hardware configuration of the edge position reading device 100 will be described with reference to the block diagram of FIG. The edge position reading device 100 has a sensor unit 210 and a control device 300. The edge position reading device 100 operates according to a command from the control device 300.

The sensor unit 210 has a light source unit 211, a light receiving unit 212, and an AFE (Analog Front End) 213. AFE213 is an analog circuit that connects a signal detection device such as a sensor with a digital signal processing device such as a microcomputer or an electronic hardware circuit. The AFE 213 outputs a drive signal to the light receiving unit 212 and the light source unit 211 at a predetermined timing according to a command from the control device 300.

The light source unit 211 is turned on or off when a drive signal is input from AFE213. By lighting, it irradiates a long line of light in the width direction with a predetermined amount of light.

When the drive signal is input from the AFE 213, the light receiving unit 212 outputs to the AFE 213 an analog voltage signal for one line long in the width direction, in which the received light is photoelectrically converted by each pixel of the pixel array. When an analog voltage signal is input from the pixel array of the light receiving unit 212, the AFE 213 executes A / D (Analog / Digital) conversion and outputs the digital voltage signal of each pixel to the control device 300.

When a signal is input from the AFE 213, the control device 300 executes a process of adding pixel output values, an edge position detection process, and the like, as described later, and reads the edge position of the conveyed paper P. The reading result is output to the correction device connected to the subsequent process of the control device 300. The correction device corrects the position of the paper P according to the output of the edge position reading device 100. However, the image position shift on the paper P may be prevented by adjusting the image forming position according to the transport position of the paper P without using the correction device. Further, although the configuration using AFE213 is shown above, the processing performed by AFE213 may be executed by an LED driver circuit, a pixel array driver circuit, an A / D converter, or a circuit in which these are combined.

The control device 300 is configured by, for example, an FPGA (Field-Programmable Gate Array). However, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or the like may execute a part or all of the processing performed by the FPGA. Further, the control device 300 may have a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). For example, according to a program stored in advance in the ROM, the RAM is used as a work memory to control the light source unit 211 and process the output of the pixels read by the light receiving unit 212.

Further, although the configuration in which the control device 300 is provided outside the sensor unit 210 is shown, the present invention is not limited to this. The sensor unit 210 may have the control device 300, or the image forming device, the correction device in the subsequent process, or the like may have the control device 300.

Further, although the configuration in which the sensor unit 210 has the AFE213 is shown, the configuration may be such that the AFE213 is provided outside the sensor unit 210, or the correction device or the like in the subsequent process may have the AFE213.

The control device 300 can realize the functional configuration described below by the above hardware configuration.

FIG. 5 is a block diagram showing an example of the functional configuration of the control device 300. The control device 300 has a communication unit 301, a drive clock generation unit 302, and a preprocessing unit 303. Further, the control device 300 has a condition setting unit 304, a signal level detection unit 305, a signal output addition processing unit 306, and an edge position detection unit 307.

The communication unit 301 communicates to control devices connected to the control device 300, such as the AFE 213 and the correction device, and to input / output data. For example, serial communication is used as the communication method.

The drive clock generation unit 302 generates a drive clock signal and outputs it to the AFE 213 via the communication unit 301. The light source unit 211 and the light receiving unit 212 in the sensor unit 210 are controlled via the AFE 213 at the timing based on the generated drive clock signal.

The pre-processing unit 303 performs processing for removing output noise and the like as pre-processing for processing the pixel output read by the sensor unit 210. The preprocessing includes, for example, a moving average process in the width direction, an average process in the transport direction, and the like.

The width direction moving average process is a process of averaging the output values of pixels adjacent to each other in the width direction in the pixel array of the light receiving unit 212 while shifting the section. For example, the average value of the output values of seven adjacent pixels is obtained from the pixels at arbitrary positions in the width direction, and the output values of the pixels are used. By this processing, output noise due to dust adhering to the light receiving surface, shot noise for each pixel, thermal noise, and the like are removed or reduced. Further, when a rod lens is used, output noise having a periodicity such as a 7-pixel interval and reproducibility may be generated. Since the light collected by the rod lens has an intensity distribution, it is generated by superimposing the intensity distribution for each rod lens along with the arrangement of the rod lenses. Such noise is also removed or reduced by the width direction moving average processing.

The transport direction averaging process is a process of averaging the output values of pixels in the transport direction, that is, in the direction intersecting the width direction. When the fluctuation of the output value for each pixel in the width direction is large, the output noise is removed or reduced by averaging the output values of the pixels even in the direction intersecting the width direction. For example, when a plurality of pixel arrays are provided in the transport direction, the average value of the output values of the pixels adjacent to each other in the transport direction is obtained for the pixels at arbitrary positions in the width direction and used as the output value of the pixels. If a plurality of pixel arrays are not provided in the transport direction, a plurality of output values are acquired by time division in pixels at arbitrary positions in the width direction while transporting the paper P, and the average value thereof is used as the average value. It is the output value of the pixel.

The content of the pretreatment is not limited to the above, and can be variously changed depending on the noise situation and the like.

The condition setting unit 304 sets the condition for reading the edge position. For example, in the width direction moving average processing, preprocessing conditions such as the number of adjacent pixels for averaging the output values are set. Further, reading conditions such as the number of times the edge of the paper P is read, the reading position of the edge in the transport direction, and the timing, or the edge detection condition such as the threshold value for detecting the edge position and how to determine the threshold value are set. The condition can be input, for example, by reading a condition file in which setting data of various conditions are recorded from an external storage device such as a USB (Universal Serial Bus) via the communication unit 301.

The signal level detection unit 305 acquires the signal level Vh and Vl of the output value of the pixel. The signal levels Vh and Vl in the present embodiment are, for example, the maximum value and the minimum value among the output values of the pixels for one line of the pixel array arranged in the width direction. The acquired signal levels Vh and Vl are used for calculating the threshold value when the threshold value is automatically determined. However, the signal levels Vh and Vl are not limited to the maximum value and the minimum value as described above. For example, in a pixel array, even if the size of the paper is the smallest of the papers to be conveyed, the output value of the reflected light is acquired by using the pixels from which the output value of the reflected light from the paper can be obtained. The signal level Vh may be calculated based on the acquired output value. When the acquired signal level Vh is equal to or less than a predetermined threshold value, a predetermined predetermined value, that is, a fixed value may be used as the signal level Vh. From the obtained Vh, the threshold value may be determined as Vh / 2.

On the other hand, for the signal level Vl, a predetermined predetermined value, that is, a fixed value may be used without acquiring data. Since the signal level Vh fluctuates greatly depending on the paper P to be conveyed, it is necessary to obtain it from the acquired data. However, since the signal level Vl is an output value in the background region, the fluctuation of the output value is small.

The signal output addition processing unit 306 adds the output values of the pixels of the pixel array at each position in the width direction. Specifically, for example, at an arbitrary position in the width direction, the output value of the pixel for the red light by the pixel array 212r, the output value of the pixel for the green light by the pixel array 212g, and the blue light for the blue light by the pixel array 212b. Add the output value of the pixel. Then, the added value is output as the output value of the pixel at that position.

The output of each pixel of the pixel array is a signal, and the output value thereof changes to some extent with time. The “pixel output value that changes with time” is an example of the “pixel output signal”. Further, the signal output addition processing unit 306 is an example of "an addition unit that adds the output signals of the pixels of the pixel array at each position in a predetermined direction".

The edge position detection unit 307 specifies a position (coordinate) at which the output value of adjacent pixels in the width direction changes from a value smaller than the threshold value to a value larger than the threshold value, and outputs the position (coordinates) as the edge position of the paper P. The edge position detection unit 307 is an example of an "edge position detection unit that detects the edge of an object".

Next, an example of processing by the control device 300 will be described with reference to the flowchart of FIG.

First, in step S601, the condition setting unit 304 sets the conditions necessary for reading the edge position. As described above, the conditions to be set are preprocessing conditions, edge detection processing conditions, and the like. The condition setting unit 304 outputs the set value to the preprocessing unit 303, the signal level detection unit 305, the signal output addition processing unit 306, and the edge position detection unit 307, and the necessary conditions are set in each unit.

Next, in step S603, the control device 300 issues a command to drive the light source unit 211 and the light receiving unit 212 at the timing based on the clock signal by the drive clock generation unit 302. The command is issued to AFE213 via the communication unit 301. Based on the drive signal from the AFE 213, the light source unit 211 irradiates the region through which the widthwise edge of the conveyed paper P passes at a predetermined timing.

The light receiving unit 212 outputs an analog voltage signal of one line of pixels to the AFE 213 at a predetermined timing based on the drive signal from the AFE 213. The AFE 213 performs A / D conversion and outputs a digital voltage signal of one line of pixels to the control device 300.

The communication unit 301 inputs the output signal of one line of pixels and outputs it to the preprocessing unit 303. The pre-processing unit 303 executes pre-processing such as width direction moving average processing and transport direction averaging processing, and outputs the pre-processing result to the signal level detection unit 305.

Next, in step S605, the signal level detection unit 305 acquires the signal levels Vh and Vl at the output values of the pixels for one line. When the method for determining the threshold value for edge detection is set to "automatic determination" by the condition setting unit 304, the signal level detection unit 305 calculates the threshold value for edge detection from the acquired signal level Vh and Vl. do. The calculated threshold value is input to the edge position detection unit 307. The calculation is performed, for example, by the calculation of (Vh + Vl) / 2. When the threshold value is not automatically determined, the threshold value data recorded in the condition file is input to the edge position detection unit 307.

Next, in step S607, the signal output addition processing unit 306 determines whether to execute the addition processing of the pixel output values based on the values of the signal level Vh and the signal level Vl. That is, when sufficient reflected light is obtained from the paper P and the difference between the signal level Vh and the signal level Vl is large, it is determined that the signal output addition process is not executed. When the difference between the signal level Vh and the signal level Vl is small, it is determined that the signal output addition process is executed. This determination is not limited to the method using the detection results of the signal level Vh and the signal level Vl, but the data such as the type, color, or surface condition of the paper is recorded in the condition file in advance, and the data is referred to. You may judge by that.

If it is determined in step S607 that the signal output addition processing is to be executed, in step S609, the signal output addition processing unit 306 adds the pixel output values at each position in the width direction. That is, for each position in the width direction, for example, the output value of the pixel of the pixel array 212r, the output value of the pixel of the pixel array 212g, and the output value of the pixel of the pixel array 212b are added. The output value of the pixel for one line obtained by the addition is input to the edge position detection unit 307.

If it is determined in step S607 that the signal output addition process is not executed, the signal output addition process is not executed, and the output values of the pixels for one line of the pixel array are input to the edge position detection unit 307. In this case, for example, the output value of the pixels for one line of any one of the pixel array 212r, the pixel array 212g, or the pixel array 212b is input to the edge position detection unit 307.

Next, in step S611, the edge position detection unit 307 identifies a position where the output value of the adjacent pixel in the width direction changes from a value smaller than the threshold value to a value larger than the threshold value, and outputs the position as the edge position of the paper P. ..

Next, when the condition is set to read the edge positions of a plurality of positions of the paper P in the transport direction, it is determined in step S613 whether the edge positions are read at a predetermined position or a predetermined number of times. When it is determined in step S613 that the edge position has been read a predetermined position or a predetermined number of times, the control device 300 ends the process. On the other hand, if it is determined that the paper has not been read, the process returns to step S603, and the reading of the edge position of the paper P is executed again. As will be described later, when the edge positions of a plurality of locations are read, the inclination of the paper P is obtained in addition to the position of the paper P.

The edge position reading device 100 executes the above processing and reads the edge position of the paper P. The position or inclination of the paper P is detected based on the edge position of the paper P. The correction device in the post-process corrects the position or inclination of the paper P based on the detection result.

Next, the data read by the edge position reading device 100 and the actions and effects of the edge position reading device 100 will be described with reference to FIGS. 7 to 9.

FIG. 7 is a diagram illustrating a state in which the edge position of the paper P is read by the edge position reading device 100 and the read data. (A) shows how the paper P is transported along the transport path T in the direction indicated by the thick black arrow, and the edge W of the paper P is read by the sensor unit 210.

(B) shows the output value of the pixel for one line with respect to the red light read by the pixel array 212r. The horizontal axis is the position (coordinates) of each pixel in the pixel array in the width direction. The vertical axis is the output value of the pixel. The broken line represents the signal level Vh of the output value of the pixel, and the difference from the signal level Vl is shown as the range D. The two alternate long and short dash lines 214 indicate the position of the edge W in the width direction and the position of one end 210a of the sensor unit 210, respectively. The dotted line indicates a threshold value 215 for edge detection. Similarly, (c) and (d) show the output values of one line of pixels for green light and blue light read by the pixel array 212g and the pixel array 212b, respectively.

In the region where the light is emitted from the light source unit 211, the amount of reflected light from the region where there is no paper P is small, and the output value of the pixel is small. On the other hand, the amount of reflected light from the region where the paper P is located is large due to the reflection by the paper P, and the output value of the pixel is large. Therefore, by detecting the position in the width direction in which the output value of the pixel changes from a small value to a large value, the position of the edge W of the paper P in the width direction can be read. The area without the paper P is hereinafter referred to as a "background area".

Here, conventionally, the position of the edge W of the paper P is read by using the output value of the pixel for the color having the largest change among red, green, and blue. For example, in FIG. 7, the change in the output value of the pixel with respect to the red light is larger than the change in the output value of the pixel with respect to the green and blue light. This means that the color of the paper P is close to red and the amount of reflected light of red is large. In the example of FIG. 7, the position of the edge W in the width direction can be read by specifying the position where the pixel output value: R with respect to the red light changes from a value smaller than the threshold value 215 to a value larger than the threshold value 215. can.

However, some papers P have various colors and surface conditions, and depending on the paper, a sufficient amount of reflected light may not be obtained. For example, in FIG. 8, the output values of the pixels for red, green, and blue light are all smaller than the threshold value 215. The color of the paper P is black, and a sufficient amount of reflected light cannot be obtained in any of the colors. In such a case, the position of the edge of the paper P cannot be read.

On the other hand, FIG. 9 shows a case where the threshold value for edge detection is lowered as compared with FIG. The dotted line is the threshold value 216. In the example of FIG. 9, the output value of the pixel due to the reflected light from the paper P exceeds the threshold value 216 for any of the red, green, and blue light. However, due to noise light such as dust in the background area, the output value of the pixels may increase even if there is no paper. In FIG. 9, the pixel output 216a represents a pixel output due to noise light. If the threshold value 216 is reduced, the pixel output due to noise light may exceed the threshold value, and in such a case, it becomes impossible to accurately read only the position of the edge.

In the edge position reading device 100 of the present embodiment, the output values of the pixels are added for each position in the width direction. For example, in FIG. 10, (a) is an output value of a pixel for red light, (b) is an output value of a pixel for green light, (c) is an output value of a pixel for blue light, and (d) is a width direction. For each position in, the sum of the output values of the pixels for the red, green, and blue light is shown.

By adding the output values of the pixels for the light of three colors, the output value can be increased as compared with the case where only a single color is used. This makes it possible to prevent the edges of the paper from becoming unreadable due to insufficient light intensity of the reflected light from the paper due to the color and surface condition of the paper. In addition, since the difference between the output value of the pixel due to the noise light and the output value of the pixel due to the reflected light from the paper can be widened, the edge position of the paper may be erroneously read due to the noise light. Can be prevented.

Furthermore, since the output values for light of different colors such as red, green, and blue are used as the output values of the pixels to be added, it is possible to suppress the difference in the amount of reflected light for each color of the paper, and it is possible to suppress the difference in the amount of reflected light for each color of the paper. The edges of the paper can be read.

As described above, according to the edge position reading device 100 of the present embodiment, the edge position of the object can be read without being restricted by the type of the object.

In this embodiment, a configuration is shown in which light close to white is irradiated and red, green, and blue light are received by each of the three pixel arrays, but the present invention is not limited to this. For example, light may be emitted from three light sources of red, green, and blue, and the reflected light of each color may be received in a time-division manner by one pixel array.

The color of the light used is not limited to red, green, or blue, and other colors such as cyan, magenta, or yellow may be substituted or additionally used. Further, the number of pixel arrays and light sources provided for each color may be increased or decreased.

Further, if the light from the object can be received with a sufficiently large output without irradiating the object, it is not necessary to have a light source for irradiating the object with the light.

Further, in the above, the image forming apparatus has shown an example of reading the edge in the width direction of the conveyed paper, but the present invention is not limited to this. For example, it can be applied to read the edge of a transported article or sheet, a moving article or sheet, or the like. It can also be applied to read the edges of various objects such as stopped paper, sheets, or articles in any direction. In addition, an example of using the reflected light from the object is shown, but if the object transmits or passes light, the edge can be read by using the transmitted light or the passing light of the object. good.

[Second Embodiment]
Next, an example of the edge position reading device of the second embodiment will be described with reference to FIGS. 11 to 12. In the second embodiment, the description of the same component as that of the above-described embodiment may be omitted.

First, before explaining the edge position reading device 100a of the second embodiment, the influence of the reflected light in the background region in the edge position reading device will be described with reference to FIG.

FIG. 11 is a schematic view of how the sensor unit 210 reads the edge position of the paper P conveyed in the direction indicated by the thick black arrow from the side. Here, the background area B is an area where the sensor unit 210 reads, and there is no paper P. The background area B is, for example, the belt surface of a transport belt for transporting the paper P. The transport belt is a member that transports the paper P placed on the belt surface by moving the belt surface in the transport direction. In the area read by the sensor unit 210, in the area where there is no paper P, the sensor unit 210 faces the belt surface.

Here, when the region where the edge of the paper P is read is irradiated with light, if the amount of light reflected from the background region B, that is, the belt surface is large and the output value of the pixels in the pixel array is large, the reflected light of the paper P is used. The difference from the pixel output value becomes small. In particular, when the addition processing is performed by the signal output addition processing unit 306, the difference from the signal output of the pixels due to the reflected light of the paper P may be further reduced.

The output of the pixel due to the reflected light from the background region B becomes noise with respect to the output of the pixel due to the reflected light of the paper P. Therefore, when the amount of the reflected light from the background region B is large, the SNR (Signal to Noise Ratio) of the output signal of the pixel due to the reflected light of the paper P decreases. As a result, the edge position of the paper P may not be read correctly.

As shown in FIG. 12, the edge position reading device 100a of the present embodiment has an opening 218 that allows light to pass or pass through a portion facing the sensor unit 210 in a region where the sensor unit 210 reads the edge of the paper P. It is configured to be equipped with. The opening 218 is, for example, in FIG. 12, a gap formed between two transport belts when the paper P is delivered from one transport belt B1 to the next transport belt B2. Since there is no belt surface in this region, even if the sensor unit 210 irradiates light, it is not reflected by the belt surface, and the reflected light does not enter the sensor unit 210.

Therefore, it is possible to prevent the reflected light from the background region B and secure the SNR of the pixel output signal due to the reflected light of the paper P. As a result, the reading accuracy of the edge position of the paper P can be ensured, and the edge position of the paper P can be read correctly.

The effects other than the above are the same as those described in the first embodiment.

[Third Embodiment]
Next, an example of the edge position reading device of the third embodiment will be described with reference to FIG. In the third embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 13 is a diagram illustrating a state of reading the edge position by the edge position reading device 100b of the third embodiment. (A) is a schematic view observing from the side how the sensor unit 210 reads the edge position of the paper P conveyed in the direction indicated by the thick black arrow. (B) is an enlarged view of the periphery of the sensor unit 210.

In the region where the sensor unit 210 reads the edge of the paper P as in the second embodiment, if the opening 218 is provided at a position facing the sensor unit 210, the light emitted from the sensor unit 210 passes through. The reflected light is suppressed. However, when the space for transporting the paper P is narrow, some member may be arranged in the vicinity of the opening 218.

At such times, the light that has passed through the opening 218 may be reflected by a member arranged in the vicinity of the opening 218 and incident on the sensor unit 210. The reflected light from the member may reduce the SNR of the pixel output signal due to the reflected light of the paper P, as described in the second embodiment.

As shown in FIG. 13, the edge position reading device 100b of the third embodiment includes a light absorbing member 219 at a position facing the sensor unit 210 in a region where the sensor unit 210 reads the edge of the paper P. It is supposed to be. The light absorbing member 219 is, for example, black brushed paper. By absorbing light, reflection on the surface is prevented.

The irradiation light from the light source unit 211 in the sensor unit 210 is absorbed by the light absorption member 219, and noise light incident on the sensor unit 210 is prevented. Therefore, it is possible to prevent the reflected light from the background region B and secure the SNR of the pixel output signal due to the reflected light of the paper P. As a result, the reading accuracy of the edge position of the paper P can be ensured, and the edge position of the paper P can be read correctly.

The effects other than the above are the same as those described in the first embodiment.

[Fourth Embodiment]
Next, an example of the edge position reading device of the fourth embodiment will be described with reference to FIG. In the fourth embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 14 is a diagram illustrating a state of reading the edge position by the edge position reading device 100c of the fourth embodiment. (A) is a schematic view observing from the side how the sensor unit 210 reads the edge position of the paper P conveyed in the direction indicated by the thick black arrow. (B) is an enlarged view of the periphery of the sensor unit 210.

In the region where the sensor unit 210 reads the edge of the paper P as in the second embodiment, if the opening 218 is provided at a position facing the sensor unit 210, the light emitted from the sensor unit 210 passes through. The reflected light is suppressed. However, when the space for transporting the paper P is narrow, some member may be arranged in the vicinity of the opening 218.

At such times, the light that has passed through the opening 218 may be reflected by a member arranged in the vicinity of the opening 218 and incident on the sensor unit 210. The reflected light from the member may reduce the SNR of the signal output of the pixel due to the reflected light of the paper P, as described in the second embodiment.

As shown in FIG. 14, the edge position reading device 100c of the fourth embodiment is configured to include a mirror 220 at a position facing the sensor unit 210 in a region where the sensor unit 210 reads the edge of the paper P. .. The reflecting surface of the mirror 220 is tilted at a predetermined angle with respect to the irradiation direction of the light from the sensor unit 210 so that the reflected light does not enter the sensor unit 210. The mirror 220 is an example of a light reflecting surface.

The irradiation light from the light source unit 211 in the sensor unit 210 is reflected by the mirror 220 in a direction different from the direction in which the sensor unit 210 is arranged. This makes it possible to prevent noise light from being incident on the sensor unit 210. The angle at which the reflected light of the mirror 220 does not enter the sensor unit 210 is determined in advance by an experiment or a simulation, and the mirror 220 is adjusted and fixed to this angle.

As described above, it is possible to prevent the reflected light from the background region B and secure the SNR of the signal output of the pixel due to the reflected light of the paper P. As a result, the reading accuracy of the edge position of the paper P can be ensured, and the edge position of the paper P can be read correctly.

The effects other than the above are the same as those described in the first embodiment.

[Fifth Embodiment]
Next, an example of the edge position reading device of the fifth embodiment will be described with reference to FIGS. 15 to 18. In the fifth embodiment, the description of the same component as that of the above-described embodiment may be omitted.

The paper is sandwiched between, for example, a plurality of rollers, gripped, placed on a transport belt, and transported. At this time, due to the difference in the rotation speed of each of the plurality of rollers, the rollers may be tilted and placed on the conveyor belt.

FIG. 15 shows how the paper P is misaligned, that is, shifted in parallel in the width direction, and is tilted and placed on the transport belt for transport. (A) is a state before the misalignment of the paper P is corrected. (B) shows a state after the edge position of the paper P is read by the edge position reading device and the misalignment of the paper P is corrected by the correction device in the subsequent process. The position of the edge of the paper P is corrected before and after the correction. However, the inclination of the paper P remains.

In the edge position reading device 100d of the present embodiment, the sensor unit 210d reads the edge positions of a plurality of different points of the paper P in the transport direction, and detects the inclination of the paper P based on the result.

FIG. 16 shows an example of how the sensor unit 210d reads the edge positions of a plurality of different locations on the paper P, and "pixel output values are added to the red, green, and blue light obtained at each location. Value "is shown. (A) shows the positional relationship between the reading points 1, the reading points 2, and the reading points 3 and the paper P. For easy viewing, the position of the sensor unit 210d in the transport direction is shifted with respect to the paper P, but in reading, the sensor unit 210d is fixed and the paper P is transported. Then, the timing of reading by the sensor unit 210d is shifted, and a plurality of different points on the paper P, that is, edge positions of the reading points 1 to 3 are read.

(B) indicates "a value to which the output value of the pixel is added" at the reading point 1. That is, the output values of the pixels of the pixel array 212r, the pixel array 212g, and the pixel array 212b are added for each position in the width direction. Similarly, (c) and (d) indicate "a value to which the output value of the pixel is added" at the reading point 2 and the reading point 3.

At the reading location 1, the edge position of the paper P in the width direction is W3. At the reading points 2 and 3, the edge positions of the paper P in the width direction are W4 and W5, respectively. Since the paper P is tilted, the edge positions at each location have different values.

FIG. 17 shows an example of the functional configuration of the control device 300d included in the edge position reading device 100d of the present embodiment. The edge position detection unit 307d detects the edge positions W3 to W5 by the same method as described in the first embodiment. In addition to this, the inclination of the paper P is calculated from the edge positions W3 to W5 by, for example, tan ^-1 {(W5-W3) / L ₃₁ }. However, L ₃₁ is the distance in the transport direction from the reading point 1 to the reading point 3. In the above, three edge positions are read, but in order to obtain the inclination of the paper P, at least two edge positions may be read. As the number of reading points is increased, the tilt detection accuracy can be improved due to the effect of averaging.

FIG. 18 shows another example of how the sensor unit 210d reads the edge positions of a plurality of different locations on the paper P in the edge position reading device 100d of the present embodiment. FIG. 18 shows how the inclination of the paper P is corrected based on the edge positions W7 and W6 read at the reading points 1 and 2. (A) is before the correction, and (b) is after the correction.

In the edge position reading device 100d, the sensor unit 210d reads W7 and W6, and the edge position detecting unit 307d calculates the inclination tan ^-1 {(W7-W6) / L ₇₆ }. However, L ₇₆ is the distance in the transport direction from the reading point 1 to the reading point 2. The calculated inclination of the paper P is output to the correction device and corrected by the correction device.

In the edge position reading device 100d, the ideal position in the width direction of the paper P is defined in advance, and the position of the paper P with respect to the ideal position is obtained from the difference from the edge position detected by the edge position detection unit 307d. The deviation may be calculated. For example, in FIG. 18, if W6 is an ideal position, the edge position detection unit 307d can calculate the position deviation of the paper P by the calculation of W7-W6. The calculated misalignment of the paper P is output to the correction device and corrected by the correction device.

As described above, according to the edge position reading device 100d of the present embodiment, the position and the inclination of the paper can be detected based on the edge position of the read paper.

The effects other than the above are the same as those described in the first embodiment.

[Sixth Embodiment]
Next, an example of the edge position reading device of the sixth embodiment will be described with reference to FIGS. 19 to 21. In the sixth embodiment, the description of the same component as that of the above-described embodiment may be omitted.

As described above, in the edge position reading device, when the output value of the pixel exceeds the threshold value due to dust or the like, the edge position may be erroneously detected. In the present embodiment, erroneous detection based on the output value of pixels such as dust is prevented.

FIG. 19 is a block diagram showing an example of the functional configuration of the control device 300e included in the edge position reading device 100e of the present embodiment. The control device 300e has a threshold pixel number detection unit 191 and a dust or the like determination unit 192.

The threshold pixel number detection unit 191 detects the number of pixels whose output value of pixels exceeds the threshold value of the output value in a predetermined range in the width direction. The detected number of pixels is input to the dust or the like determination unit 192. When the number of detected pixels is lower than the threshold value of the number of pixels in a predetermined range set in advance by the condition setting unit 304e, the dust or the like determination unit 192 determines that the output value of this pixel is caused by dust or the like. Then, the determination result is output to the edge position detection unit 307e. The edge position detection unit 307e ignores the output value of the pixel determined to be caused by dust or the like in the edge detection. Further, the condition setting unit 304e allows the predetermined range and the threshold value of the number of pixels to be arbitrarily changed. The threshold pixel number detection unit 191 is an example of the pixel number detection unit. Further, the edge position detection unit 307e is an example of "an edge position detection unit that detects the edge position of an object based on the output of the addition unit and the output of the pixel number detection unit".

FIG. 20 shows an example of data read by the edge position reading device 100e of the present embodiment. The horizontal axis represents the position in the width direction, and the vertical axis represents the output value of the pixel. The black circle plot shows the addition of the pixel output values for red, green, and blue light, and the white circle plot shows the pixel output value for red light, for example, without such addition. Is shown. Further, 193 shown by a solid straight line indicates a threshold value for the output value of the pixel. The dust or the like output 194 circled with a solid line indicates the output value of the pixel caused by the dust or the like, and the paper output 195 surrounded by the broken line square indicates the output value of the pixel caused by the paper P.

For example, in the dust output 194, the number of pixels exceeding the threshold value 193 is one out of the pixel output of red light, that is, the five plots of white circles. On the other hand, in the paper output 195, out of the five white circle plots, the number of pixels exceeding the threshold value 193 is four. Therefore, for example, if the predetermined range is 5 pixels and the threshold value of the number of pixels in the dust determination unit 192 is 2 pixels or more, the edge position can be read correctly without being affected by the output caused by dust or the like. Become.

On the other hand, in the dust output 194, the number of pixels exceeding the threshold value 193 out of the pixel outputs for red, green, and blue light, that is, the five black circle plots, is three. On the other hand, in the paper output 195, out of the five white circle plots, the number of pixels exceeding the threshold value 193 is five. Therefore, in this case, for example, if the predetermined range is 5 pixels and the threshold value of the number of pixels in the dust determination unit 192 is 4 pixels or more, the edge position is correctly read without being affected by the output caused by dust or the like. Is possible.

FIG. 21 shows another example of the data read by the edge position reading device 100e of the present embodiment. FIG. 21 illustrates side effects when the threshold value of the number of pixels is made too large.

In FIG. 21, the black circle plot shows the sum of the pixel output values for red, green, and blue light, and the black dust and the like output 196 circled by the solid line is caused by the black dust and the like. The output value of the pixel is shown. Plot 197 shows the correct edge position, and plot 198 shows the falsely detected edge position. The reason why the output value of the pixel is small in 196 is that dust and the like are black.

In such a case, for example, if the predetermined range is 5 pixels and the threshold value of the number of pixels is 3 pixels or more, the plot 197 of the correct edge position is detected, but the predetermined range is 5 pixels and the threshold value of the number of pixels is set. If the number of pixels is 5 or more, the plot 198 of the wrong edge position is detected. Therefore, when it is predicted that the size of dust or the like is small, or when the pixel output is not added to the red, green, and blue light, it is desirable to reduce the threshold value of the number of pixels.

As described above, according to the present embodiment, the edge position can be read correctly without being affected by the output caused by dust or the like, and a predetermined range and a predetermined range are used depending on whether the pixel output addition processing is performed or not. The threshold value of the number of pixels can be optimized.

[7th Embodiment]
In the seventh embodiment, the description of the same components as those of the above-described embodiment may be omitted.

As mentioned in the explanation of FIG. 5, the threshold value for edge detection may be automatically determined. In that case, for example, among the output values of the pixels in the width direction acquired by the sensor unit 210, the signal level Vh and the signal level Vl are used, and (Vh + Vl) / 2 is set as the threshold value. However, on the paper P, unlike a transparent sheet or metallic paper, the output value of the pixels due to the light reflected by the paper may not be stable.

FIG. 22 shows an example thereof. In FIG. 22, the portion 221 shown by the solid line square shows the output value of the pixel due to the light reflected by the metallic paper. As shown in the figure, the output value changes significantly, and in this case, if the threshold value is automatically obtained using the signal levels Vh and Vl, the edge position may not be read correctly.

Therefore, the edge position reading device 100f of the present embodiment detects the paper type and switches the threshold value determination method according to the paper type.

FIG. 23 is a block diagram showing an example of the functional configuration of the control device 300f included in the edge position reading device 100f of the present embodiment. The control device 300f has a paper type detection unit 222.

The paper type detection unit 222 detects the type of paper to be conveyed. For example, it is realized by referring to the type of paper selected by the operation panel or the like in the image forming apparatus and stored in the RAM. When the paper type detection unit 222 detects that the output value of the pixel due to the reflected light of the transparent sheet or metallic paper is not stable, the paper type detection unit 222 outputs the detection result to the condition setting unit 304f. In this case, the condition setting unit 304f does not automatically determine the threshold value of the pixel output value for edge detection, but sets it to a fixed value. On the other hand, when the paper type detection unit 222 detects that the output value of the pixel due to the reflected light is stable, the paper type detection unit 222 outputs the detection result to the condition setting unit 304f. In this case, the condition setting unit 304f is set to automatically determine the threshold value of the output value of the pixel for edge detection. The condition setting unit 304f is an example of a threshold value determination method change unit, and the paper type detection unit 222 is an example of a type detection unit.

As described above, by switching the setting of the threshold value determination method according to the paper type, the influence of the paper type can be suppressed and the edge position can be read correctly.

[Eighth Embodiment]
As mentioned in the description of FIG. 5, the present embodiment relates to the width direction moving average processing in the preprocessing unit 303. In the seventh embodiment, the description of the same components as those of the above-described embodiment may be omitted.

In the edge position reading device, when a rod lens is used, output noise having periodicity may be generated due to crosstalk of light rays passing through the rod lens or the like. FIG. 24 shows an example of the output noise having such periodicity and the output value after the width direction moving average processing in the preprocessing unit 303. In FIG. 24, the solid line 241 is the output value before the width direction moving average processing, and the broken line 242 is the output value after the width direction moving average processing. Before the processing, there is a variation in the output value with periodicity, but after the processing, the variation is suppressed.

On the other hand, FIG. 25 shows an example of side effects when the width direction moving average processing is performed. In FIG. 25, the dust 243 in the circled portion represents the output of the pixel caused by one dust, and the dust 244 in the circled portion represents the output of the pixel caused by another dust, and is represented by a circle. The enclosed portion 245 represents the output of the pixel due to the edge of the paper P. The solid line plot is the output when the width direction moving average processing is not performed, and the broken line plot is the output when the width direction moving average processing is performed.

As shown in FIG. 25, when the width direction moving average processing is not performed, the number of pixels exceeding the threshold value of the pixel output value is small in the dust 243 and the dust 244. Is determined. However, when the width direction moving average processing is performed, the dust 243 and the dust 244 become a united mass, and the number of pixels exceeding the threshold value of the pixel output value increases. As a result, the dust 243 and the dust 244 are not determined as dust, which causes erroneous detection of the edge position.

Further, when there is output of dust or the like near the edge of the paper P, the two can be separated without performing the width direction moving average processing, but when the width direction moving average processing is performed, both are united and then the edge position. Is detected, which leads to false detection of the edge position.

In particular, when the pixel output addition processing for red, green, and blue light is performed, the output due to dust or the like becomes large, which may cause the side effect of the above-mentioned width direction moving average processing.

Therefore, in the edge position reading device 100g of the present embodiment, the execution of the width direction moving average processing is switched between the case where the addition processing of the pixel output for the red, green, and blue light is performed and the case where the addition processing is not performed. ..

FIG. 26 is a block diagram showing an example of the functional configuration of the control device 300g included in the edge position reading device 100g of the present embodiment. The control device 300 g has a width direction moving average processing execution switching unit 246. When the width direction moving average processing execution switching unit 246 refers to the condition setting unit 304g and performs the addition processing of the pixel output for the red, green, and blue light, the width direction moving average processing execution switching unit 246 should not execute the width direction moving average processing before. When the processing unit 303 is set and the addition processing is not performed, the preprocessing unit 303 is set so as to execute the width direction moving average processing. As a result, output noise can be suppressed by the width direction moving average processing while preventing side effects. The preprocessing unit 303 is an example of a moving average processing execution unit.

Although the edge position reading device, the image forming device, the edge position reading method, and the program according to the embodiment have been described above, the present invention is not limited to the above embodiment and varies within the scope of the present invention. Can be modified and improved.

11, 12, 13 Paper tray (storage unit)
22 Image forming unit 100, 100a, 100b, 100c, 100d Edge position reader 191 Threshold pixel number detection unit (example of pixel number detection unit)
210, 210d Sensor unit (example of sensor unit)
211 Light source unit 212 Light source unit 213 AFE
215, 216, 217 Threshold 218 Aperture 219 Light Absorbing Member 220 Mirror (Example of Light Reflecting Surface)
222 Paper type detection unit (example of type detection unit)
246 Width direction moving average processing execution switching unit 300, 300d Control device 301 Communication unit 302 Drive clock generation unit 303 Preprocessing unit 304, 304e, 304f, 304g Condition setting unit 305 Signal level detection unit 306 Signal output addition processing unit (addition unit) An example)
307, 307d, 307e Edge position detection unit (example of edge position detection unit)
500 Image forming device B Background area P Paper (object)
T transport path W1, W2, W3, W4, W5, W6, W7 Edge position

Japanese Patent No. 4930692

Claims (6)

A sensor unit that has a pixel array in which a plurality of pixels that output detection signals are arranged in a predetermined direction and is arranged so that the edges of an object can be read.
An addition unit that adds the output signals of the pixels of the pixel array at each position in the predetermined direction.
An edge position detection unit that detects the edge position of the object based on the output of the addition unit, and an edge position detection unit.
It has a pixel number detection unit for detecting the number of pixels whose output of the addition unit is equal to or higher than a predetermined threshold value.
The edge position detection unit is a reading device, characterized in that the edge of the object is detected when the number of pixels detected by the pixel number detection unit does not fall below the threshold value of the number of pixels in a predetermined range. The pixel outputs a signal according to the amount of received light, and outputs a signal.
The pixel array receives light of a plurality of different wavelengths and receives light.
The reading device according to claim 1, wherein the adding unit adds an output signal of the pixel to light having a plurality of different wavelengths. The reading device according to claim 1 or 2, wherein the sensor unit includes a plurality of the pixel arrays in a direction intersecting the predetermined direction. The pixel outputs a signal according to the amount of received light, and outputs a signal.
The plurality of pixel arrays each have red, green, or blue color selection means, and receive red, green, or blue light that has passed through the color selection means.
The reading device according to claim 3, wherein the adding unit adds an output signal of the pixel to the red, green, and blue light. An image forming apparatus comprising the reading apparatus according to any one of claims 1 to 4 . A step of reading the edge of an object by a sensor unit having a pixel array in which a plurality of pixels for outputting a detection signal are arranged in a predetermined direction and arranged so that the edge of the object can be read.
An addition step of adding the output signal of the pixel of the pixel array at each position in the predetermined direction by the addition unit.
A step of detecting the edge position of the object based on the output of the addition unit by the edge position detection unit, and
The pixel number detection unit includes a step of detecting the number of pixels whose output of the addition unit is equal to or higher than a predetermined threshold value.
The edge position detection unit is a reading method, characterized in that the edge of the object is detected when the number of pixels detected by the pixel number detection unit does not fall below the threshold value of the number of pixels in a predetermined range.

Images