JP2008039636A - Photoelectric detection device, its light emission intensity adjusting method, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately and quickly perform level adjustment of a driving signal for allowing a light reception signal level to reach a target value, when a characteristic of the light emission signal level of a light receiving element to a driving signal level of a light emitting element is expressed by a plurality of approximate expressions corresponding to a domain of the driving signal level, in a photoelectric detection device having the light emitting element and the light receiving element. <P>SOLUTION: The light emitting element is driven by a driving signal having a prescribed reference level (S1, S2), and an adjustment range of the driving signal level and a calculation formula in the adjustment range are selected (S8-S11), based on a height relation between the light reception signal level and its target value (S7), and an approximate expression is determined by using the light reception signal level when the light emitting element is driven by each driving signal having a plurality of levels in the selected adjustment range and the calculation formula, and the driving signal level is adjusted by using the approximate expression (S12). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes a photoelectric detection device that detects an object by detecting reflected light radiated from the light emitting element and reflected by the object, a method for adjusting the emission intensity thereof, and an optical detection device thereof. More specifically, the present invention relates to an apparatus and method for adjusting the light emission intensity of a light emitting element so that the level of a light reception signal is always constant even when the reflectance is reduced due to deterioration of a detection target.

  Conventionally, in a color image forming apparatus employing an electrophotographic technique, a photosensitive drum as an image carrier is charged by a charging unit, and a laser beam is irradiated on the charged photosensitive drum in accordance with image information to form a latent image. The latent image is developed by a developing means, and the developed toner image is transferred to a recording paper to form an image.

  In addition, a plurality of image stations that perform such a series of image forming processes are provided, and toner images of each color of C (cyan), M (magenta), Y (yellow), and BK (black) are formed on each photoconductor. In addition, tandem color image forming apparatuses that form color images by transferring color images for transfer formed on an endless belt-like intermediate transfer belt at the transfer position of each photoreceptor onto recording paper have become widespread. is doing.

  In this tandem type color image forming apparatus, when an image is formed on a photoconductor of each color and transferred to a recording paper on a transfer belt, there is a color shift on the recording paper if the transfer image position of each color deviates from the ideal position. An image is formed and the quality of the image is degraded.

  Therefore, conventionally, as a pre-processing of image formation, a toner image of a misregistration correction pattern is formed on the photosensitive drum without conveying the recording paper when the power switch of the apparatus main body is turned on or every predetermined number of times of image formation. Then, this toner image is transferred onto an intermediate transfer belt, and this is read by a CCD sensor or the like to detect a positional deviation, and an electric signal is applied to the image signal to be recorded, and is provided in the optical path of the laser beam. The reflecting mirror is driven to correct the optical path length change or optical path change. (See Patent Document 1).

  Further, in such a color image forming apparatus, since the color images are formed by superimposing the toner images of the respective colors, it is necessary to always form the toner images of the respective colors with an appropriate density. This is because, if a toner image of any color is not formed with an appropriate density, a full color image formed by superimposing them causes a color shift.

  Therefore, the following adjustment is performed in order to always form toner images of the respective colors with appropriate densities. That is, an image density detection sensor is provided so as to face the surface of the intermediate transfer belt, and as a pre-processing of image formation, a toner image of a toner density adjustment pattern is formed on the photosensitive drum without conveying the recording paper. Is transferred onto the intermediate transfer belt, and the density of the toner image transferred onto the intermediate transfer belt is detected by an image density detection sensor. Based on the detection result, image forming conditions are adjusted, and the toner of any color The image is also adjusted so that it is always formed with an appropriate density (see Patent Document 2).

  As described above, when the positional deviation correction pattern is read by the CCD sensor, or when the toner image for detecting the toner density (hereinafter referred to as the toner density detection pattern) is read by the image density detection sensor, these patterns are illuminated by the light emitting element. To do. Here, since the reflectance of the intermediate transfer belt is higher than the reflectance of the toner, the CCD sensor or the image density detection sensor detects the photoelectric conversion output of the reflected light from the intermediate transfer belt and the positional deviation correction pattern or toner. Each pattern can be detected based on the level difference from the photoelectric conversion output of the reflected light from the toner of the density detection pattern.

  However, if the reflectivity decreases due to dirt or deterioration of the intermediate transfer belt, the difference from the reflectivity of the toner becomes small, so that it is difficult to accurately detect the misalignment correction pattern or the toner density detection pattern. Become. As an image forming apparatus that addresses such problems, an image forming apparatus that performs calibration so that the photoelectric conversion output level of reflected light from the background (image carrier surface) of the toner density detection pattern is always constant is proposed. (See Patent Document 3). Here, the light emission intensity of the light emitting element is adjusted by adjusting the duty ratio of the pulse of the drive signal input to the light emitting element, that is, by PWM (pulse width modulation). Then, when the product is new, the PWM value is set to a predetermined value, the photoelectric conversion output level at that time is stored, and the subsequent PWM value is adjusted so that the stored photoelectric conversion output level is always obtained.

  The above-mentioned Patent Document 3 does not describe the procedure for adjusting the light emitting element so that the photoelectric conversion output level is always constant, and thus is not described in the literature, but the photoelectric conversion output level is always constant. A conventional method for adjusting the light emitting element will be described.

FIG. 10 is a graph showing characteristics of the light receiving signal level (photoelectric conversion output level) of the light receiving element with respect to the drive signal level of the light emitting element. In this figure, the horizontal axis (X axis) is the drive signal level, and the vertical axis (Y axis) is the received light signal level. Further, f _A (X) is a characteristic when new, and f _B (X) is a characteristic after use for a predetermined time.

In FIG. 10, it is assumed that the light reception signal level is Y ₁₁ (= f _A (X ₁₁ )) when the drive signal level is set to X ₁₁ when the product is new. When the image forming apparatus is used, the reflectance decreases due to dirt or deterioration of the intermediate transfer belt, and the drive signal level vs. received light signal level characteristic changes to f _B (X). If set to X _11, received light signal level _{Y 12 (= f B (X} 11)) , and the lowered than when new. Therefore, X ₁₂ which is X having f _B (X) = Y ₁₁ is obtained by the following procedure.

In FIG. 10, when the maximum value of the drive signal level is 1, first, the drive signal level is set to ½, and the received light signal level is measured. If light reception signal level is larger than Y _11, to set the levels of the drive signal to 1/4 (= 1 / 2-1 / 4), if the received light signal level is smaller than Y _11, drive signal level Is set to 3/4 (= 1/2 + 1/4). In the same manner, according to the magnitude relationship between the received light signal level and Y ₁₁ , the drive signal level addition / subtraction value (subtraction when large, addition when small) is a geometric series having a ratio of ½. by going to set to converge to X _12.

However, in this method, when the magnitude relationship between the light reception signal level and Y ₁₁ is inverted due to noise mixing, it is not possible to obtain an appropriate drive signal level X ₁₂ . If a large number of drive signal levels are set and the above procedure is executed for each of them, this problem can be solved, but it takes much time and the processing load also increases.

Thus, there is a method for obtaining X ₁₂ by obtaining an approximate expression of f _B (X) without setting a large number of drive signal levels in this way. That is, for example, f _B (X) is approximated by a linear function αX + β (α and β are constants), a plurality of drive signal level sample values are set, and α, β using the received light signal levels corresponding to those sample values. Is used to determine the approximate expression and X ₁₂ is determined using the approximate expression.

  However, in such a method for calculating the drive signal level using the approximate expression, if there is only one approximate expression depending on the drive signal level versus the light receiving signal level characteristic, the difference between the approximate expression and the actual characteristic becomes large, and the There is a problem that a high drive signal level cannot be obtained. In order to solve this problem, it is conceivable to use two or more approximate equations. However, it is possible to obtain an accurate drive signal level by itself, but it takes a long time.

Japanese Patent No. 2642351 JP2002-6568 (paragraph 0004) JP 2002-296852 A

  The present invention has been made to solve such problems, and its object is to detect an object by detecting reflected light emitted from a light emitting element and reflected by the object with a light receiving element. In the photoelectric sensing device, when the drive signal level vs. received light signal level characteristic is expressed by a plurality of approximate expressions according to the drive signal level range, the adjustment range of the drive signal level is limited and adapted to the adjustment range By selecting an approximate expression, the driving signal level can be set accurately and quickly.

The invention according to claim 1 includes a light emitting element and a light receiving element that detects reflected light of light emitted from the light emitting element to an object, and a light receiving signal level of the light receiving element with respect to a driving signal level of the light emitting element. Is a photoelectric detection device whose characteristics are expressed by a plurality of approximate expressions that differ according to the drive signal level range, and that drives the light emitting element with a drive signal of a predetermined reference level. Determining means for determining a magnitude relationship between the light receiving signal level and the target value when the light emitting element is driven by a driving signal of a predetermined reference level, and the drive signal level based on the determination result of the determining means A selection means for selecting the adjustment range and the calculation formula of the adjustment range, and the light-receiving element when the light-emitting element is driven by drive signals of a plurality of levels within the adjustment range selected by the selection means. The approximate expression is obtained using the optical signal level and the calculation formula selected by the selection means, and the drive signal level with the received light signal level of the light receiving element as the target value is determined using the approximate expression. And a photoelectric detector.
According to a second aspect of the present invention, there is provided the photoelectric detection device according to the first aspect, wherein a plurality of the reference levels are provided.
According to a third aspect of the present invention, in the photoelectric detection device according to the second aspect, the plurality of pairs of light emitting elements and light receiving elements are provided, and the reference level driving means is driven by a driving signal having a different reference level for each light emitting element. The determining means determines the magnitude relationship between the light receiving signal level of the light receiving element and the target value for each set, and the selecting means determines the drive signal level for each set based on the determination result of the determining means. The adjustment range and the calculation formula are selected.
According to a fourth aspect of the present invention, in the photoelectric detection device according to any one of the first to third aspects, the reference level is a drive signal level at a boundary between the plurality of approximate expressions.
A fifth aspect of the present invention is an image forming apparatus comprising the photoelectric detection device according to any one of the first to fourth aspects.
The invention according to claim 6 includes a light emitting element and a light receiving element that detects reflected light of light emitted from the light emitting element to an object, and a light receiving signal level of the light receiving element with respect to a driving signal level of the light emitting element. The light emission intensity of the light emitting element is adjusted so that the light reception signal level of the photoelectric detection device is a predetermined target value, in which the characteristics of the photoelectric detection device are expressed by a plurality of approximate expressions that vary depending on the drive signal level range A reference level driving step of driving a light emitting element with a drive signal of a predetermined reference level, and a light reflected from the light emitted from the light emitting element driven at the reference level to the object. Receiving light by the element, generating a received light signal, determining a magnitude relationship between the level of the received light signal and the target value, and an adjustment range of the drive signal level based on a determination result of the magnitude relationship; as well as Selecting a calculation formula for obtaining an approximate expression of the adjustment range, driving the light emitting element with a plurality of levels of drive signals within the selected adjustment range, and driving with the plurality of levels of drive signals The reflected light of the light emitted from the light emitting element to the object is received by the light receiving element, a light receiving signal is generated, and the levels of the plurality of light receiving signals and the selected calculation formula are used. And a step of determining a drive signal level using the approximate expression as a target value with the received light signal level of the light receiving element as a target value. It is an adjustment method.
According to a seventh aspect of the present invention, in the method for adjusting the light emission intensity of the photoelectric detection device according to the sixth aspect, a plurality of pairs of light emitting elements and light receiving elements are provided, and the reference level driving step drives different reference levels for each light emitting element. Driven by a signal, the determination step determines a magnitude relationship between the light reception signal level of the light receiving element and the target value for each set, and the selection step is performed for each set based on a determination result of the determination step. The adjustment range of the drive signal level and the calculation formula are selected.

  According to the present invention, the characteristics of the light receiving signal level of the light receiving element with respect to the driving signal level of the light emitting element are expressed by a plurality of approximate expressions that differ according to the range of the driving signal level, and the light emitting element is represented by a driving signal having a predetermined reference level. Based on the magnitude relationship between the light receiving signal level of the light receiving element and its target value when driven with the, select the calculation formula for obtaining the adjustment range of the driving signal level and the approximate expression of the adjustment range Using the light receiving signal level of the light receiving element when driving the light emitting element with a plurality of levels of driving signals within the adjustment range and the selected calculation formula, the approximate expression is obtained, and using the approximate expression, Since the drive signal level with the received light signal level of the light receiving element as the target value is determined, the adjustment range of the drive signal level is limited, and an approximate expression suitable for the adjustment range is used. Level setting can be performed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a front view showing a configuration of a main part of a color image forming apparatus according to a first embodiment of the present invention.

  This color image forming apparatus has a configuration in which image forming portions of respective colors are arranged along an intermediate transfer belt, and is a so-called tandem system. That is, four image forming units (electrophotographic process units) 6Y, 6M, 6C, and 6BK are arranged in order from the upstream side in the rotation direction of the intermediate transfer belt 5. The intermediate transfer belt 5 is an endless (endless) belt wound around a drive roller 7 and a driven roller 8 that are driven to rotate. The drive roller 7 is driven to rotate by a drive motor (not shown).

  The plurality of image forming units 6Y, 6M, 6C, and 6BK have the same internal configuration except that the colors of the toner images to be formed are different. The image forming unit 6Y forms a yellow toner image, the image forming unit 6M forms a magenta toner image, the image forming unit 6C forms a cyan toner image, and the image forming unit 6BK forms a black toner image. Therefore, in the following description, the image forming unit 6Y will be specifically described. However, since the other image forming units 6M, 6C, and 6BK have the same configuration as the image forming unit 6Y, the image forming units 6M, 6C are similar to the image forming unit 6Y. 6BK, only the symbols distinguished by M, C, and BK are displayed in the figure in place of the Y added to each component of the image forming apparatus 6Y, and the description thereof is omitted.

  The image forming unit 6Y includes a photoreceptor drum 9Y, a charger 10Y disposed around the photoreceptor drum 9Y, an exposure device 11, a developing device 12Y, a photoreceptor cleaner (not shown), a static eliminator 13Y, and the like. ing. The exposure device 11 is configured to irradiate laser beams 14Y, 14M, 14C, and 14BK that are exposure lights corresponding to the colors of the toner images formed by the image forming units 6Y, 6M, 6C, and 6BK.

  At the time of image formation, the outer peripheral surface of the photosensitive drum 9Y is uniformly charged by the charger 10Y in the dark, and then exposed by the laser beam 14Y corresponding to the yellow image from the exposure device 11, so that the electrostatic latent image is formed. It is formed. The developing device 12Y visualizes (develops) the electrostatic latent image with yellow toner, thereby forming a yellow toner image on the photosensitive drum 9Y. This yellow toner image is transferred onto the intermediate transfer belt 5 by the action of the transfer unit 15Y at a position where the photosensitive drum 9Y and the intermediate transfer belt 5 are in contact (primary transfer position). After the transfer of the toner image is completed, unnecessary toner remaining on the outer peripheral surface of the photosensitive drum 9Y is wiped off by the photosensitive cleaner, and then is neutralized by the static eliminator 13Y and waits for the next image formation. Similarly, a magenta toner image, a cyan toner image, and a black toner image are respectively transferred to the intermediate transfer belt 5 by the functions of the transfer units 15M, 15C, and 15BK at the photosensitive drums 9M, 9C, and 9BK and the primary transfer position. Transcribed above. By this transfer, a full color image is formed on the intermediate transfer belt 5 by superimposing the images of the respective color toners.

  On the other hand, the sheets 4 stored in the sheet feeding tray 1 are sent out in order from the uppermost one, conveyed onto the intermediate transfer belt 5, and at a position where the intermediate transfer belt 5 and the sheet 4 are in contact (secondary transfer position). A full color toner image is transferred. The sheet 4 on which the full-color superimposed image is formed is peeled off from the intermediate transfer belt 5 and fixed on the image by the fixing device 16, and then discharged to the outside of the image forming apparatus.

  In the color image forming apparatus according to the present embodiment, as in the conventional image forming apparatus, the image forming units 6Y, 6M, 6M, 6M, and 6M are pre-processed when the power switch of the apparatus main body is turned on or every predetermined number of image formations. 6C and 6BK form a positional deviation correction pattern, a toner density detection pattern, and the like on the intermediate transfer belt 5, and photoelectric elements disposed so as to face the downstream side of the image forming unit 6BK in the rotation direction of the intermediate transfer belt 5. These patterns are detected by the sensor 17, and positional deviation correction control and toner density control are performed. Details of these controls are disclosed in the above-mentioned Patent Documents 1 and 2, etc., and will not be described here. The control is performed so that the light reception signal level of the reflected light from the intermediate transfer belt 5 becomes a predetermined target value. A means for adjusting the light emission intensity of the sensor 17 will be described.

FIG. 2 is a block diagram showing an electrical configuration of a device that adjusts the light emission intensity of the light emitting element 20 of the photoelectric sensor 17.
This device includes a CPU 30, a RAM 32, a ROM 33, a nonvolatile memory 34, and an I / O port 35 connected to each other via a data bus 31, and the light emitting element 20 of the photoelectric sensor 17 that is connected to the I / O port 35. The portion for controlling the light emission amount (the drive circuit 23, the light emission amount control unit 24) and the portion for taking in the detection signal of the light receiving element 21 of the photoelectric sensor 17 (amplifier 25, A / D converter 26). The photoelectric sensor 17 irradiates and reflects the light emitted from the light emitting element 20 on the flat surface or curved surface (on the roller 7) of the surface of the intermediate transfer belt 5 (FIG. 1), and the regular reflected light or diffuse reflected light is reflected. The light receiving element 21 is disposed so as to receive light.

  The CPU 30 executes control of the entire apparatus and various processes, the RAM 32 serves as a work area when the CPU 30 executes various controls, and the ROM 33 stores programs used when the CPU 30 executes various controls. Yes. Further, in the nonvolatile memory 34 such as NVRAM (nonvolatile RAM) or flash memory, various data (details will be described later) necessary for setting the detection signal level of the light receiving element 21 to a predetermined target value. Stored.

  FIG. 3 is a circuit diagram showing a specific configuration example of the light emitting element 20 and the drive circuit 23. As shown in this figure, the anode of the light emitting element 20 made of a light emitting diode is connected to the power source, the cathode of the light emitting element 20 is connected to the collector of the transistor constituting the drive circuit 23, and the base of the transistor has light emission. A PWM drive signal from the quantity control unit 24 is supplied through a low-pass filter and an amplifier. A series circuit of a resistor and a diode is connected between the emitter of the transistor and the ground. This diode is provided in order to prevent the light emitting element 20 from emitting light due to noise of a predetermined threshold value (eg, 0.7 volts) or less.

FIG. 4 is a graph showing the characteristics of the light reception signal level of the light receiving element 21 with respect to the drive signal level of the light emitting element 20 (drive signal level versus light reception signal level characteristic). The horizontal axis (X axis) of this graph is the drive signal level of the light emitting element 20, and the vertical axis (Y axis) is the light reception signal level of the light receiving element 21. As shown in this figure, drive signal level to the received light signal level characteristics, between a maximum value from 0 of the driving signal is expressed by two approximate functions as a boundary drive signal X _0. Here, the region (region a) below X ₀ is the quadratic function f ₁ (X) = eX ² + gX (e and g are constants), and the region (region b) above X ₀ is the linear function f ₂ (X ) = HX + k (h and k are constants). Here, the photoelectric conversion characteristic of the light receiving element 21 is linear, and therefore, the light emission intensity with respect to the drive current level of the light emitting layer element 20 is the same characteristic as this figure.

The nonvolatile memory 34 stores data of drive signal level vs. received light signal level characteristics (f ₁ (X), f ₂ (X)) when the intermediate transfer belt 5 is new. The non-volatile memory 34 stores a drive signal level X ₁₁ when the light reception signal level reaches a predetermined target value Y ₁₁ when the intermediate transfer belt 5 is new. Further, f ₁ (X) and f ₂ (X) are stored in the nonvolatile memory 34. Therefore, when the intermediate transfer belt 5 is new, when the drive signal level of the light emitting element 20 and X _11, the light receiving signal level of the light receiving element 21 by increasing or decreasing next Y _11, the levels of the drive signal from X _11, a light receiving it is possible to increase or decrease the signal level from the Y _11.

However, by using an image forming apparatus, if the reflectivity by dirt and deterioration of the intermediate transfer belt 5 is lowered, setting a driving signal level of the light emitting element 20 to X _11, a light receiving signal of the light receiving element 21 level is less than Y _11. Therefore, in order to make the light reception signal level to the target value Y ₁₁ at the time of a new, it is necessary to drive a signal level greater than X _11. In the present embodiment, the drive signal level is obtained by the following procedure.

Here, as shown in FIG. 4, the drive signal level vs. received light signal level characteristics when the reflectance is reduced due to dirt or deterioration of the intermediate transfer belt 5 are F ₁ (X) in the region a, and F in the region b. ₂ (X). In this embodiment, F ₁ (X) is set to pX ² + qX, F ₂ (X) is set to rX + s, and an approximate expression thereof is used to obtain a drive signal level for setting the received light signal level to the target value Y ₁₁ . Hereinafter, a description will be given with reference to the flowchart shown in FIG.

First, the CPU 30 controls the light emission amount control unit 24 to input a drive signal of a reference level (hereinafter referred to as a reference signal) from the drive circuit 23 to the light emitting element 20 (S1), and causes the light emitting element 20 to emit light (S2). ). Here, the reference level is X ₀ in FIG. 4, that is, the level at the boundary between the regions a and b. Next, the light reflected by the intermediate transfer belt 5 is detected by the light receiving element 21 (S3), amplified by the amplifier 25, and the received light signal level is converted into a digital value by the A / D converter 26 and recorded in the RAM 32 ( S4).

Next, it is determined whether all sample values have been recorded (S5). Here, since only the received light signal level when the light emitting element is driven by the reference signal is recorded, the process proceeds to step S6 to determine whether or not the input signal is the reference signal (S6). Here, since the input signal is the reference signal, the process proceeds to step S7, and it is determined whether or not the light reception signal level is equal to or higher than a predetermined value Z. Here, Z may be f ₂ (X ₀ ) (= f ₁ (X ₀ )), but is preferably set to a value slightly larger than f ₂ (X ₀ ) in consideration of noise.

If it is determined in step S7 that the received light signal level is equal to or higher than Z (S7: YES), a calculation formula A for obtaining pX ² + qX, which is an approximate expression for the region a, is read from the nonvolatile memory 34 and stored in the RAM 32. Store (S8), and set a plurality of samples of different drive signal levels in the region a (S9). On the other hand, if it is determined in step S7 that the received light signal level is less than Z (S7: NO), calculation formula B for obtaining rX + s, which is an approximate expression for region b, is read from nonvolatile memory 34 and stored in RAM 32. Store (S10), and set a plurality of samples of different drive signal levels in the region b (S11).

The processes in steps S8 to S11 will be described with reference to FIG. In this case, since the received light signal level when the drive signal level is X ₀ is smaller than Z (≈Y ₁₁ ), the process proceeds to step S10, and a calculation formula B for obtaining rX + s, which is an approximate expression of the region b, is obtained. While being selected and set in the RAM 32, a plurality of samples having different drive signal levels are set in the region b. Next, the light emitting element 20 is sequentially driven by the plurality of driving signal levels (S2), and the light receiving signal level of the light receiving element 21 is recorded in the RAM 32 (S3, S4). Then, the processes of steps S2 to S4 are repeated (S5: NO, S6: NO) until the recording of the light reception signal level for all the samples of the drive signal level is performed (S5: NO, S6: NO). S5: YES), adjustment is executed (S12).

The adjustment in step S12 is performed as follows. First, by using the received light signal level Y _i for the sample X _i of a plurality of different levels of the drive signal, determining the values of r and s approximations rX + s by the above equation. Next, X that satisfies rX + s = Y ₁₁ is obtained by this approximate expression. In the case of FIG. 4, X = X ₁₂ = (Y ₁₁ -s) / r. In the case of steps S9 and S10 using the approximate expression of the region a, the drive signal level is determined by solving for pX ² + qX = Y ₁₁ . An example of a calculation formula for obtaining r and s and a calculation formula for obtaining p and q are shown below.

上記の式［１］はｒを求める計算式であり、式［２］はｓを求める計算式である。

The above formula [1] is a formula for calculating r, and formula [2] is a formula for calculating s.

また、ｐ、ｑは、式［３］及び式［４］を解くことで得られる、式［５］、式［６］により算出する。

In addition, p and q are calculated by Equation [5] and Equation [6] obtained by solving Equation [3] and Equation [4].

  As described above, according to the image forming apparatus of the first embodiment of the present invention, the magnitude relationship between the light reception signal level of the light receiving element 21 and the target value when the light emitting element 20 is driven by the drive signal of the predetermined reference level. The drive signal level adjustment range and a calculation formula for obtaining an approximate expression of the adjustment range are selected, and the drive signal level sample value is set within the selected adjustment range, and the sample value drive signal is set. An approximate expression is obtained using the received light signal level of the light receiving element 21 when the light emitting element 20 is driven and the selected calculation formula, and the received light signal level of the light receiving element 21 is set as a target using the approximate expression. Since the drive signal level to be a value is determined, a plurality of approximate expressions can be set according to the drive signal level vs. received light signal level characteristics, and the drive current can be set accurately and quickly. In the above description, the value of the level at the boundary between the regions a and b is used as the reference value, but the value in the region a or the region b may be used.

[Second Embodiment]
FIG. 6 is a graph showing the drive signal level vs. received light signal level characteristic of the photoelectric sensor in the color image forming apparatus according to the second embodiment of the present invention, and FIG. 7 shows the received light signal level of the light receiving element as a target value when new. It is a flowchart which shows the procedure which calculates | requires the drive signal level of the light emitting element for setting. The configuration of the main part of the color image forming apparatus according to the present embodiment and the electrical configuration of the apparatus that adjusts the light emission intensity of the light emitting element of the photoelectric sensor are the same as those in the first embodiment, and thus the description thereof is omitted. .

As shown in FIG. 6, the drive signal level vs. received light signal level characteristic of the photoelectric sensor 17 of the present embodiment has four regions a, b, c, d (a in this figure) between 0 and the maximum value of the drive signal. , B and a and b in FIG. 4 are different, and each region is represented by a different approximate expression. Then, when setting the light reception signal level of the light receiving element 21 to the target value, as the reference signal, signal A, i.e. with a signal in the area a, the level is the level of the boundary of b X _A, light receiving signal for the reference signal If the level is equal to or greater than the predetermined value Z, the adjustment range of the drive signal level is set to the region a, and a calculation formula A for obtaining an approximate expression of the region a (different from the calculation formula A in FIG. 5) is selected. sets a sample drive signal level within, is less than the predetermined value Z, as the reference signal, the signal B, that region b, using the signal level X _B is the level of the boundary of c, and the same procedure Execute. Hereinafter, a description will be given with reference to FIG.

  First, the signal A is input as a reference signal from the drive circuit 23 to the light emitting element 20 (S21, S22), and the light emitting element 20 is caused to emit light (S23). Next, the light reflected by the intermediate transfer belt 5 is detected by the light receiving element 21 (S24), amplified by the amplifier 25, and the received light signal level is converted into a digital value by the A / D converter 26 and recorded in the RAM 32 ( S25).

Next, it is determined whether the light reception signal level is equal to or higher than a predetermined value Z. Here, the value of Z, as in the first embodiment, the drive current level to the received light signal level characteristics at the time of a new, it is preferable to slightly larger value than the value corresponding _{to the} drive current X _A.

When it is determined in step S26 that the received light signal level is equal to or higher than Z (S26: YES), when the signal A is input as the reference signal, the calculation formula A for obtaining the approximate expression of the region a is nonvolatile. The data is read from the memory 34 and stored in the RAM 32, and a plurality of samples having different drive signal levels are set in the region a (S29). In addition, when a signal B, a signal C (level X _C signal that is a level at the boundary between the areas c and d), and a signal D (maximum value of the driving signal in the area d) are input as reference signals, Calculation formulas B (different from calculation formula B in FIG. 5), C, and D for obtaining approximate expressions for the regions b, c, and d are read from the nonvolatile memory 34 and stored in the RAM 32, respectively. A plurality of samples of different drive signal levels are set in d.

  After the setting in step S29, as in the first embodiment, the light emitting element 20 is sequentially driven by a plurality of drive signal levels in the set area (S31), and the light receiving signal level of the light receiving element 21 is set in the RAM 32. (S32, S33), and when the recording of the received light signal level for all the samples of the drive signal level is completed (S34: YES), the adjustment is executed (S35).

  On the other hand, when it is determined in step S26 that the received light signal level is less than Z (S26: NO), it is determined whether or not the input reference signal is the signal C (S27). If (S27: NO), the signal is changed to the signal B when the input reference signal is the signal A, and when the signal is the signal B, the signal is changed to the signal C and then the process proceeds to step S22. If it is signal C (S27: YES), the reference signal is set to signal D and the routine proceeds to step 31.

  In other words, until the received light signal level becomes Z or higher, the reference signal is changed in order from the lower level to the higher level, and the received light signal level becomes Z or higher before the reference signal becomes the signal D. In the area, when the signal D is obtained, a plurality of samples having different drive signal levels are set in the area D, and the light emitting element 20 is sequentially driven by the plurality of drive signal levels in the set area. The received light signal level is recorded in the RAM 32, and the adjustment is executed when the received light signal level recording for all the samples of the drive signal level is completed.

  As described above, according to the present embodiment, the drive signal level vs. received light signal level characteristic is approximated by using a larger number of approximate equations than in the first embodiment, so that the drive signal level can be adjusted more accurately. Can do.

[Third Embodiment]
FIG. 8 is a perspective view showing an image forming unit, an intermediate transfer belt, and a photoelectric sensor in a color image forming apparatus according to a third embodiment of the present invention, and FIG. 9 shows a light receiving signal level of a light receiving element as a target value when new. 5 is a flowchart showing a procedure for obtaining a drive signal level of a light emitting element for setting to 1. The configuration of the main part of the color image forming apparatus of this embodiment is the same as that of the first embodiment, and the approximation function of the drive signal level vs. light reception signal level characteristic of the photoelectric sensor is the same as that of the second embodiment. .

  As shown in FIG. 8, in this embodiment, three photoelectric sensors 17, 18, 19 are opposed to each other in the main scanning direction of the intermediate transfer belt 5, and each detects reflected light from the vicinity of the left end, the center, and the vicinity of the right end. .

  As shown in FIG. 9, as a reference signal for driving the light emitting elements of the photoelectric sensors 17, 18, and 19, the photoelectric sensor 17 sets the signal A, the photoelectric sensor sets the signal B, and the photoelectric sensor 19 sets the signal C (S41). Each light emitting element is inputted from each drive circuit (S42), and each light emitting element is caused to emit light (S43). Next, the light reflected by the intermediate transfer belt 5 is detected by each light receiving element (S44), amplified and digitally converted, and recorded in the RAM 32 (S45).

  Next, it is determined whether or not the light reception signal level of the photoelectric sensor 17 is equal to or higher than a predetermined value Z (S46). If it is determined that it is equal to or higher than Z (S46: YES), calculation for obtaining an approximate expression of the region a. Expression A is read from the nonvolatile memory 34 and stored in the RAM 32, and a plurality of samples having different drive signal levels are set in the region a (S49).

  After the setting in step S49, as in the first embodiment, the light emitting elements are sequentially driven by a plurality of drive signal levels in the region a (S53), and the light receiving signal levels of the light receiving elements are recorded in the RAM 32. (S54, S55) When the recording of the received light signal level for all the samples of the drive signal level is completed (S56: YES), the adjustment is executed (S57).

  On the other hand, if it is determined in step S46 that the light reception signal level is less than Z (S46: NO), it is determined whether or not the light reception signal level of the photoelectric sensor 18 is equal to or greater than a predetermined value Z (S47). If it is determined that the value is greater than or equal to Z (S47: YES), the calculation formula B for obtaining the approximate expression of the region b is read from the nonvolatile memory 34 and stored in the RAM 32, and a plurality of different drives are stored in the region b. A signal level sample is set (S50). Thereafter, the light emitting elements are sequentially driven by a plurality of driving signal levels in the set region b (S53), and the light receiving signal levels of the light receiving elements are recorded in the RAM 32 (S54, S55). When the recording of the signal level is completed (S56: YES), adjustment is executed (S57).

  If it is determined in step S47 that the light reception signal level is less than Z (S47: NO), it is determined whether the light reception signal level of the photoelectric sensor 19 is equal to or greater than a predetermined value Z (S48). If it is determined that the value is greater than or equal to Z (S48: YES), a calculation formula C for obtaining an approximate expression of the region c is read from the nonvolatile memory 34 and stored in the RAM 32, and a plurality of different drivings are stored in the region c. A signal level sample is set (S51). Thereafter, the light emitting elements are sequentially driven by a plurality of drive signal levels in the set area c (S53), the light receiving signal levels of the light receiving elements are recorded in the RAM 32 (S54, S55), and the light receiving for all the driving signal level samples is received. When the recording of the signal level is completed (S56: YES), adjustment is executed (S57).

  Furthermore, when it is determined in step S48 that the received light signal level is less than Z (S48: NO), the calculation formula D for obtaining the approximate expression of the region d is read from the nonvolatile memory 34 and stored in the RAM 32, A plurality of samples having different drive signal levels are set in the region d (S52). Thereafter, one of the photoelectric sensors 17, 18, and 19 is driven by the plurality of drive signal levels in the set area d (S53), and the received light signal level of the light receiving element is recorded in the RAM 32 (S54, S55). ) When the recording of the received light signal level for all the samples of the drive signal level is completed (S56: YES), the adjustment is executed (S57).

  As described above, the driving signals of the signals A, B, and C are sequentially used in the second embodiment, but are simultaneously used in the present embodiment, so that the adjustment speed is increased accordingly. .

  In each of the above embodiments, the light emission intensity is adjusted so that the level of the reflected light from the intermediate transfer belt 5 becomes a predetermined value. However, in order to convey the reflected light from the photosensitive drum or paper. The present invention can also be applied to an apparatus that adjusts the emission intensity so that the reflected light from the conveyor belt becomes a predetermined value.

1 is a front view showing a configuration of a main part of a color image forming apparatus according to a first embodiment of the present invention. It is a block diagram which shows the electric constitution of the apparatus which adjusts the emitted light intensity of the light emitting element of the photoelectric sensor of FIG. FIG. 3 is a circuit diagram illustrating a specific configuration example of a light emitting element and a drive circuit in FIG. 2. 3 is a graph showing characteristics of a light receiving signal level of a light receiving element with respect to a driving signal level of the light emitting element of FIG. 2. 6 is a flowchart illustrating a procedure for obtaining a drive signal level for setting a light reception signal level to a target value at the time of a new product in the color image forming apparatus according to the first embodiment of the present invention. 6 is a graph showing a drive signal level vs. received light signal level characteristic of a photoelectric sensor in a color image forming apparatus according to a second embodiment of the present invention. 6 is a flowchart illustrating a procedure for obtaining a drive signal level for setting a light reception signal level to a target value at the time of a new product in the color image forming apparatus according to the second embodiment of the present invention. FIG. 10 is a perspective view illustrating an image forming unit, an intermediate transfer belt, and a photoelectric sensor in a color image forming apparatus according to a third embodiment of the present invention. 10 is a flowchart illustrating a procedure for obtaining a drive signal level for setting a light reception signal level to a target value at the time of a new product in the color image forming apparatus according to the third embodiment of the present invention. It is a graph which shows the characteristic of the light reception signal level of the light receiving element with respect to the drive current of a light emitting element.

Explanation of symbols

  5 ... Intermediate transfer belt, 6Y, 6M, 6C, 6BK ... Image forming section, 17, 18, 19 ... Sensor, 20 ... Light emitting element, 21 ... Light receiving element, 23 ... Drive circuit, 24... Luminescence amount control unit, 32... RAM, 30.

Claims (7)

A light-receiving element that detects reflected light of light emitted from the light-emitting element to an object, and the characteristics of the light-receiving signal level of the light-receiving element with respect to the driving signal level of the light-emitting element are the drive signal level Is a photoelectric detection device represented by a plurality of different approximate expressions depending on the range of
Reference level driving means for driving the light emitting element with a driving signal of a predetermined reference level, and determining a magnitude relationship between a light receiving signal level and the target value when the light emitting element is driven with a driving signal of a predetermined reference level A selection unit that selects the adjustment range of the drive signal level and the calculation formula of the adjustment range based on the determination result of the determination unit, and a plurality of levels within the adjustment range selected by the selection unit The approximate expression is obtained using the received light signal level of the light receiving element when the light emitting element is driven by the drive signal and the calculation formula selected by the selection means, and the light receiving element is obtained using the approximate expression. And a means for determining a drive signal level having the received light signal level as the target value. The photoelectric detection device according to claim 1,
A photoelectric detection device comprising a plurality of the reference levels. The photoelectric detection device according to claim 2,
There are a plurality of sets of light emitting elements and light receiving elements, the reference level driving means is driven by a driving signal having a different reference level for each light emitting element, and the judging means A photoelectric detection apparatus, wherein a magnitude relationship with the target value is determined, and the selection unit selects a drive signal level adjustment range and the calculation formula for each group based on a determination result of the determination unit. . In the photoelectric detection device according to any one of claims 1 to 3,
The photoelectric detection device according to claim 1, wherein the reference level is a driving signal level at a boundary between the plurality of approximate expressions.   An image forming apparatus comprising the photoelectric detection device according to claim 1. A light emitting element and a light receiving element that detects reflected light of light emitted from the light emitting element to an object, and the characteristics of the light receiving signal level of the light receiving element with respect to the driving signal level of the light emitting element are the drive signal level A method of adjusting the light emission intensity of the light emitting element so that the light receiving signal level of the photoelectric detection device, which is expressed by a plurality of different approximate expressions depending on the range of the above, becomes a predetermined target value,
A reference level driving step of driving the light emitting element with a driving signal of a predetermined reference level, and the light receiving element receives reflected light of the light irradiated from the light emitting element driven at the reference level to the object. A step of generating a signal, a step of determining a magnitude relationship between the level of the received light signal and the target value, an adjustment range of the drive signal level, and an approximation of the adjustment range based on a determination result of the magnitude relationship Selecting a calculation formula for obtaining a formula; driving the light emitting element with a plurality of levels of driving signals within the selected adjustment range; and the light emitting element driven with the plurality of levels of driving signals The approximate expression using the step of receiving the reflected light of the light irradiated to the object from the light receiving element and generating a light reception signal, the level of the plurality of light reception signals and the selected calculation formula Asking for The light emission intensity adjustment method of a photoelectric detection device, wherein a received light signal level of the light receiving element and a step of determining a driving signal level to the target value by using the approximate expression. The light emission intensity adjustment method of the photoelectric detection device according to claim 6,
A plurality of sets of light emitting elements and light receiving elements are provided, and the reference level driving step is driven by a driving signal having a different reference level for each light emitting element, and the determination step includes the light receiving signal level of the light receiving element and the light receiving element for each set. Determining a magnitude relationship with a target value, wherein the selection step selects a driving signal level adjustment range and the calculation formula for each group based on a determination result of the determination step; Luminous intensity adjustment method.

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