JP2001086297A - Luminous quantity measurement device and color image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small sized, low cost luminous quantity measurement apparatus and to provide a color image forming device using it. SOLUTION: In an initial calibration job, a detection calibration board (yellow patch) and a comparison calibration board (gray patch) are read to obtain a reflectance difference ΔR (Dc) (100-104), the difference is stored into a memory as a relative ratio, with respect to the reflectance of a standard white board that can be read at all times, such as white paper (106-110), the reflectance of the standard white board such as white paper is detected in the case of calibrating device difference (112-114) and is multiplied a relative value in the memory (116), to cancel the fluctuation and to correct the read value of a sample image (118). Thus, device difference which is specified to sensors can be maintained only with the initial calibration, and a paper output value can always be obtained independently of the changes time passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light quantity measuring apparatus and a color image forming apparatus, and more particularly, to irradiating a target with spot light by a light source and condensing the reflected light on a light receiving element by a condenser lens. And a color image forming apparatus provided with the light amount measuring device.

[0002]

2. Description of the Related Art A network printer as an image output device has rapidly spread due to the development of network technology centering on a computer. In particular, color printers have been actively developed in recent years along with the colorization of output images, and there has been an increasing demand for improving the maintenance stability of color image quality, uniforming the color image quality among a plurality of color printers, and the like. It is coming. Recently, high stability is required for color reproducibility irrespective of installation environment, aging, and machine differences.

In general, the sensitivity of a human to color differences is extremely high. For example, even if the images are not adjacent in time and distance, the color difference of the image to be compared is about 色 E = 5 in the L ^* a ^* b ^* color system, and is distinguished regardless of the observer or the situation. It is known that color difference ΔE = about 3 (color difference recognition limit) is required to make the difference unrecognizable (D.
H. Alman, R .; S. Berns, G .; D. Snyder and W. A. La
rsen, Performance ttesting of Color-Difference
Metrics Using a Color Tolerance Dataset, COL
OR research and application, vol.14, Number
3, June 1989).

For this reason, if the target level of the image reproducibility is to be set below the human color difference recognition limit, the required value for the image forming apparatus becomes extremely high, that is, the color difference ΔE = 3 or less.

However, as is well known, in the conventional electrophotographic system, each process is unstable, and it is difficult to meet the required value of color difference ΔE = 3 or less. this is,
In the first place, electrophotography uses electrostatic phenomena,
This is because the image output state of the apparatus itself fluctuates and the image reproducibility fluctuates due to environmental conditions such as temperature and humidity, and processing material conditions such as temporal deterioration of the photoconductor and the developer.

For this reason, in an image forming apparatus using an electrophotographic system, feedback control is performed to maintain an optimum image density. In general feedback control, the density patch is used to monitor the density reproduction status and environmental conditions in the device to determine the error from the target density, and multiply this by the feedback gain to obtain the set value correction amount of the control actuator. It has been calculated. For example, Japanese Patent Application Laid-Open No. 1-169467 discloses that a desired image density is obtained by measuring a density patch and controlling an exposure condition and a developing bias condition.

As the density patch, an unfixed toner image density patch after the development step or an image density patch formed on a recording medium such as paper after the fixing step is used. The toner image density patch is used because it is easier to create and erase a developed image than a transferred image or a fixed image created on paper, but the correlation between the toner image density patch and the fixed image density is used. However, it is difficult to detect the influence of fluctuations in the subsequent transfer step and fixing step.

On the other hand, a fixed image density patch is a fixed image itself finally obtained by a user as an image form, and can evaluate the image quality including a variation factor in a transfer step and a fixing step. For example, Japanese Patent Application Laid-Open No. 62-296
No. 669, Japanese Patent Application Laid-Open No. 63-185279, and Japanese Patent Application Laid-Open No. 5-199407 disclose a technique for monitoring the density of a fixed image by using an image reading unit incorporated in the apparatus main body. .

However, in order to detect an image, the user must return the image once output to the image reading unit and read it again in order to detect the image. It was extremely troublesome. In the case of an image forming apparatus such as a printer that does not include an image reading unit,
In principle, no image could be detected.

In view of this, the present applicant has proposed a color image monitor sensor as means for enabling online output image monitoring after the fixing process (Japanese Patent Laid-Open No. 9-1).
No. 71279). This sensor is a blue (B), green (G), and red (R) light emitting diode (visible light LED; hereinafter, corresponding to each color of yellow (Y), magenta (M), and cyan (C)). (Referred to as LED) as a light source, and the reflected light from the output image is received by a photodiode.

Generally, the emission spectrum of an LED is RGB.
It is said that it is difficult to spectrally analyze the entire color gamut with high precision because the band is narrower than the spectral distribution by a filter or the like. However, as a use condition of the sensor, a monitor output image is formed as a toner single color patch such as YMC.
By limiting the detection to the density of each single color toner, it is much more advantageous in terms of cost and size than a conventional color sensor that spectrally separates the entire color gamut and identifies each color of full color, and in terms of performance. It is also possible to provide a necessary and sufficient monitoring sensor.

However, when an output image is to be monitored online on the image forming apparatus, the surface to be measured of an output sheet as an image forming medium as an object is moved up and down, that is, perpendicular to the traveling direction of the sheet. There is a possibility that accurate measurement cannot be performed due to a problem in a change in the direction. this is,
When monitoring the density patch on the paper to be detected by using the image monitoring detection unit, the detection unit is used to prevent damage to the image due to contact and to eliminate an additional mechanism around the monitor sensor. This is because it is necessary to monitor the object and the detection target in a non-contact manner.

By the way, in a case where a surface to be measured which fluctuates up and down is measured using an optical system combining a light source, a lens, and a light receiving element (photoelectric conversion element) in a normal optical sensor,
For example, it is known that the output of the light receiving element changes by about 15% even when the paper surface fluctuates up and down by about 1 mm. If there is such an output fluctuation, it is difficult to detect a minute difference between the density patches on the paper to be detected.

[0014] For this reason, the applicants of the present invention, by receiving the reflected light on the paper surface with the photoelectric conversion element provided at the focal position of the lens, can reduce the fluctuation in the optical axis direction of the paper surface in a region satisfying specific conditions. A technology that can obtain an output that does not depend on the output has been proposed (Japanese Patent Laid-Open No. 10-175330).
issue). By combining this technology with a color image monitor sensor using LEDs, it has become possible to realize a highly accurate non-contact online image monitor.

[0015]

However, the required level of the final color reproduction accuracy, that is, the color difference, must be equal to or less than the color difference recognition limit (△ E ≦ 3). The reading accuracy for is more severe. By the way, when the required level of the color difference is allocated to each factor by tolerance and converted into the reflectance accuracy of the sensor, it is known that a reflectance reading accuracy of 1% or less is required.

There are various factors that cause a reading error of the sensor. However, as the required level of the reading accuracy increases, the variation in the wavelength of the sensor light source (eg, LED element) cannot be ignored. A general-purpose LED element has a variation in emission spectrum due to the manufacturing process. This variation in the emission spectrum cannot be avoided when using an LED element whose low cost is a great advantage.

The suppression of variations in the emission spectrum is achieved by using LE
This is achieved by selecting the D elements, but it is not preferable because the cost of the LED elements increases significantly due to the enormous labor for the selection and the extremely low yield.

As a solution to this problem, an LED device in which colored glass is incorporated in a mold resin has been devised (see JP-A-8-162676). In this technique, since the colored glass functions as a band-pass filter, the half width of the emission spectrum is narrowed, and the color purity is improved. However, absorption filters, such as colored glass and gelatin filters, are limited in wavelength selection, that is, wavelength range, are poor in controllability, and are further limited in transmission and durability. Reading accuracy cannot be obtained.

By the way, there is an optical filter known as an interference type band-pass filter which is excellent in wavelength selectivity and controllability of a half-value width. Even in this interference type band-pass filter, the center wavelength varies by several nm to 10 nm. have. Therefore, the variation cannot be eliminated.

Further, it is possible to reduce the variation in the wavelength range by narrowing the transmission band due to the half-value width by using an interference type band-pass filter. Since the output level decreases, SN deteriorates. As a result, although the variation can be suppressed to some extent, the noise component other than the variation increases, so that the accuracy cannot be improved.

Further, if an optical filter is added, the total cost required for the sensor increases, so that an increase in cost cannot be avoided.

The present invention has been made in view of the above circumstances, and has as its object to provide a small-sized and low-cost light quantity measuring device and a color image forming apparatus using the same.

[0023]

SUMMARY OF THE INVENTION The present inventors have arrived at the present invention in order to maintain high-precision full-color image quality with good reproducibility. The present invention provides a small and low-cost image monitor. Provided is a light quantity measuring device capable of non-contact and high-precision online monitoring of a density patch on a paper that is being conveyed up and down using a sensor, and a color image forming apparatus using the same. is there.

A light quantity measuring apparatus according to the present invention is a light quantity measuring apparatus for measuring a light quantity by detecting a reflected light from an object illuminated by a light source with a light receiving element. Detecting means for detecting an output variation of the light receiving element corresponding to a wavelength variation of an emission spectrum of the light source, based on an amount detected by the detecting means, and outputting an output value of the light receiving element based on a reference emission of the light source. Correction means for correcting an output value of the spectrum by light irradiation.

According to another aspect of the present invention, there is provided a light quantity measuring device which irradiates a target with spot light from a light source and reflects light reflected from the target by a condenser lens at a focal position of the condenser lens. A light amount measuring device for measuring a light amount by condensing the light on a plurality of objects, and detecting means for detecting an output variation of the light receiving element corresponding to a wavelength variation of an emission spectrum of the light source based on each of the reflected light amounts from a plurality of objects. When,
Correction means for correcting an output value of the light receiving element based on a detection amount by the detection means so as to be an output value by light irradiation of a reference emission spectrum of the light source.

The light quantity measuring device of the present invention measures the light quantity by detecting the reflected light from the object irradiated with the light from the light source by the light receiving element. According to another aspect of the present invention, there is provided a light amount measuring device configured to stably receive a reflected light amount, a light receiving element provided at a focal position of a reflected light of an object by light emitted from a light source by a condensing lens. And the amount of light can be measured. In these cases, the target object has a different amount of reflected light depending on its density. Therefore, the detecting means detects the output variation of the light receiving element corresponding to the wavelength variation of the light emission spectrum of the light source based on each of the reflected light amounts from the plurality of objects. Each light source has an emission spectrum, and each has a wavelength variation. For this reason, even if the amount of light is the same, output variation occurs in the light receiving element due to wavelength variation. Therefore, the output of the light receiving element varies due to the wavelength variation of the emission spectrum of the light source. In this case, a standard or reference output should be obtained for a standard or reference emission spectrum. Therefore, the difference from the standard or reference output is the output variation of the light receiving element corresponding to the wavelength variation, and this is detected. Since the output variation of the light receiving element is detected, the correction unit corrects the output value of the light receiving element so as to be an output value of the reference light emission spectrum of the light source due to light irradiation. That is, the degree of variation of the output of the light receiving element is detected, and the output value is corrected according to the detected degree of variation. Accordingly, even if the light source has a wavelength variation of the emission spectrum, this can be corrected and an output value independent of the wavelength variation of the emission spectrum can be obtained.

In the light quantity measuring device of the present invention, a light emitting diode can be used as the light source. The light source plays a large role in the light quantity measuring device. For example, in order to perform measurement with high accuracy, it is conceivable to irradiate light with high accuracy using an expensive light source. However, using an expensive light source increases the cost of a light quantity measuring device. In the present invention,
Since the wavelength variation of the emission spectrum of the light source can be corrected, an inexpensive light emitting diode can be employed, and the cost of the light quantity measuring device can be reduced. Since a correction amount corresponding to the wavelength variation can be detected, an output difference between sensors (that is, an instrumental difference) caused by the wavelength variation of the emission spectrum which cannot be avoided when using a small and inexpensive light emitting diode is corrected. be able to. As a result, even when a light emitting diode such as an LED is used as a light source, it is not necessary to consider an output difference between sensors (machine difference).

As the light source, at least one kind of visible light emitting diode among red, green and blue visible light emitting diodes can be adopted. A light emitting diode has a narrow emission band compared to the spectrum by an RGB filter or the like, but is easily available and easily specifies a wavelength band. Therefore, if the measurement is limited to the density measurement, that is, the light amount measurement, the light source can be used as a light source which is necessary and sufficient in performance. Further, by using a plurality of different visible light emitting diodes, the wavelength band of the light source can be broadened, and more stable light can be obtained. Furthermore, when there are a plurality of colors of the object, by associating the wavelength band of the light source for each color, that is, according to the wavelength band,
A light source that matches the color of the object can be obtained.

Further, a photodiode or a phototransistor can be used as the light receiving element. Photodiodes and phototransistors are easy to obtain and easy to obtain output values according to the amount of light. Therefore, if the measurement is limited to the density measurement, that is, the light quantity measurement, it can be used as a light receiving element which is necessary and sufficient in performance.

In the light quantity measuring device according to the present invention, it is possible to detect the output variation of the light receiving element by using, as the detecting means, calibration plates having different densities as the plurality of objects. In order to detect output variations, it is preferable that the target is specified. Therefore, if calibration plates having different densities are used as a plurality of objects, the output variation of the light receiving element can be detected from the difference in the amount of reflected light, and the output value of the light receiving element can be corrected according to the detected degree of variation. As a result, an output value that does not depend on the wavelength variation of the emission spectrum can be obtained. The calibration plate can include a detection calibration plate and a comparison calibration plate.

As at least one of the calibration plates, a calibration plate having a color that does not depend on the wavelength region of at least the emission spectrum of the light source can be used. The output of the light receiving element can be stably obtained without depending on the wavelength by the calibration plate of the color which does not depend on the wavelength. As a calibration plate of a color having no wavelength dependence in the amount of reflected light, there is an object having a gray density such as a gray patch. If this gray patch is used, the amount of reflected light corresponding to the density can be obtained without substantially depending on the wavelength of the emission spectrum of the light source. Therefore, this can be used as a reference calibration plate.

Further, as at least one of the calibration plates, a calibration plate having a color that is wavelength-dependent at least in a wavelength region of an emission spectrum of the light source can be used. The output of the light receiving element corresponding to the wavelength region of the light emission spectrum of the light source can be obtained by the calibration plate of the wavelength-dependent color. The light source is
It generally has an emission spectrum in an arbitrary wavelength region. By using a calibration plate in a wavelength range (for example, a complementary color range) corresponding to the wavelength range, the emission spectrum of the light source may significantly vary. Therefore, by using a calibration plate of a color that depends on the wavelength in the wavelength region of the emission spectrum of the light source as the calibration plate, it is possible to obtain the output of the light-receiving element that depends on the wavelength, and to more closely follow the variation of the emission spectrum of the light source. Correction becomes possible.

The detecting means may further include a calculating means for calculating a relative value between the detected output variation amount and a predetermined standard detected amount. By the detecting means, the output variation of the light receiving element corresponding to the wavelength variation of the emission spectrum of the light source can be detected from the amount of reflected light from the object,
Since the output variation is specific to the light source, it can be applied to a difference between objects. For this purpose, it is preferable to use the output variation relatively. Therefore, if the relative value between the detected output variation amount and the predetermined standard detection amount is obtained by the calculating means, the correction can be easily performed only by detecting the target object corresponding to the standard detection amount.

In this case, it is preferable that the detecting means further detects a predetermined standard plate, and the calculating means calculates the detected amount of the standard plate as a standard detected amount. That is, the predetermined standard detection amount is obtained by further detecting the standard plate. Thus, it is not necessary to determine the standard detection amount in advance, and the detection can be performed only by the detection.

The light quantity measuring device according to the present invention stores the output variation of the light receiving element detected by the detecting means corresponding to the wavelength variation of the emission spectrum of the light source based on each of the reflected light quantities from a plurality of objects. And a correction unit configured to perform the correction based on the output variation stored in the storage unit. That is, the output variation amount detected in advance is held, and based on this, the output variation amount at the time of the correction operation can be calculated. This makes it possible to reuse the detected amount of output variation once detected.

The correcting means estimates the output variation in another density range from the detection result of the output variation in a predetermined density, and the estimation correcting means corrects the output value based on the estimation result. And may be included. Although the detection based on the amount of reflected light depends on the density of the object, it is troublesome to prepare many such densities. on the other hand,
The density characteristic, which is the relationship between the density and the amount of reflected light, can be measured in advance and has a constant distribution. For this reason, the estimation unit can estimate the output variation amount in another density range from the detection result of the output variation amount at the predetermined density. By correcting the output value by the estimation correction means based on the estimation result, it is possible to obtain an output value that does not depend on the wavelength variation of the emission spectrum from the output variation amount at a low density.

[0037] The correcting means can correct the output value to a predetermined linear characteristic or non-linear characteristic based on the detection amount by the detecting means. As described above, the density characteristic can be measured in advance and has a constant distribution, but the distribution can be reduced in computational load by approximating the linear characteristic, and can be reduced by approximating the nonlinear characteristic. Delicate correction can be performed.

By using the light quantity measuring device, it is possible to obtain an easy and low-cost color image forming device. Specifically, in a color image forming apparatus that detects an output color image and controls the formation conditions of the color image according to the detection result, the color image is formed by a plurality of color materials based on the formation conditions. An image forming unit formed by the method, and a light amount measuring device according to the above, wherein the detecting unit detects a light amount of a sample image using at least any one of the plurality of color materials, and according to the detection result. And control means for controlling the formation conditions.

In a color image forming apparatus, a color image is formed by image forming means using a plurality of color materials based on forming conditions. The formation conditions are determined by detecting a color image, and are controlled by the control unit. The control unit controls the formation condition according to the light amount of the sample image using at least one of the plurality of color materials detected by the detection unit including the light amount measurement device. Accordingly, it is possible to provide an image forming apparatus capable of maintaining high-precision full-color image quality with high reproducibility.

In this case, the detecting means can be provided on the downstream side of the final step of the image forming means. By doing so, the output color image itself can be easily used.

Further, the image forming means includes:
The color image can be formed by at least one of the cyan, magenta, yellow, and black coloring materials. Further, the calibration plate can use at least one of the color materials.

Further, the detecting means may include a selecting means for selecting the correction corresponding to the color material.

As described above, according to the present invention, the detecting means for accurately and simply detecting the degree of variation of the output of the light receiving element and the correcting means for correcting the output of the light receiving element according to the detected degree of variation are provided. Thus, the output variation of the light receiving element is corrected. As an example, the calibration plate is read using a toner single color patch and a gray patch, respectively, and the amount of variation from the ideal reflectance value can be detected based on the output difference between the patches. Can be detected. As a result, it is possible to correct an output difference (machine difference) between the sensors due to the LED emission wavelength variation which cannot be avoided when using the LED element in a small size and at low cost. As a result, L
Even when a light emitting diode such as an ED is used as a light source, high-precision online monitoring without an output difference (machine difference) between sensors can be performed, so that the size and cost of the sensor can be reduced.

Further, since the machine difference can be corrected only by the initial calibration, it is not necessary to provide a calibration plate or a mechanism for calibration in the apparatus, and the influence on the productivity of image output can be eliminated. As a result, the overall size of the image forming apparatus can be reduced.
Cost reduction can be achieved.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the present embodiment, the present invention is applied to an image forming apparatus.

FIG. 2 shows a main part of an image forming apparatus according to an embodiment of the present invention. In particular, an image output terminal (hereinafter, referred to as an image output unit IOT) of an image output unit based on an electrophotographic system is schematically shown. The configuration is shown. The image forming apparatus according to the present embodiment includes an image output unit IOT and a fixed image density sensor 10. The image output unit IOT includes a laser output unit 30, a developing device 32, a transfer device 34, a cleaner 36, a scorotron charger. 38, a fixing device 40, and a photoreceptor 42.

Next, an image forming procedure in the image output unit IOT will be described. First, an original image signal input from an input unit 50 (FIG. 3), which reads an original by an image reading device (not shown) such as a scanner or is created by an external computer or the like (not shown), Appropriate processing is performed by a processing unit (not shown). The input image signal obtained by this is input to the laser output unit 30 and modulates the laser light. In this manner, the laser beam modulated by the input image signal is irradiated onto the photoreceptor 42 in a raster manner.

The photosensitive member 42 is uniformly charged by the scorotron charger 38. When the uniformly charged photosensitive member 42 is irradiated with a laser beam, an electrostatic latent image corresponding to an input image signal is formed on the surface of the photosensitive member 42. Is formed. Then, the electrostatic latent image is developed with toner by the developing device 32, the toner image developed by the transfer device 34 is transferred onto the sheet P, and is fixed by the fixing device 40. Thereafter, the photoconductor 42 is cleaned by the cleaner 36, and one image forming operation is completed. The fixed image density sensor 10 is installed downstream of the fixing device 40, and detects the image density after fixing.

Next, based on the detection result of the fixed image density sensor 10, the operation amounts such as the charge amount, the exposure amount, the developing bias, the number of rotations of the developing roll, and the toner supply coefficient are controlled to obtain a desired image quality. The process will be described with reference to a block diagram of a main part related to control of the image forming apparatus in FIG.

As shown in FIG. 3, the image forming apparatus has a CPU 66 for totally controlling the inside of the apparatus. The image forming apparatuses are functionally classified into an image control unit 56 and an image output unit 68. The image control unit 56
An image output unit 58 includes a color conversion control unit 60, an image density control unit 62, and a reference image signal generation unit 64.
Is composed of a control section 58A and a mechanism section 58B. The control unit 58A of the image output unit 58
The mechanism unit 58B includes a color conversion processing unit 68, a light amount controller 70, a developing controller 72, and a grid power supply 74. The mechanism unit 58B includes a laser output unit 30, a developing unit 32, and a charger 38 functioning as an exposure unit. Have been.

The color conversion control unit 60 is for correcting and controlling the conversion coefficients of the color conversion matrix for the input image signal input from the input unit 50. Image density controller 6
Reference numeral 2 is for controlling operation amounts such as a charge amount, an exposure amount, a developing bias, a developing roll rotation speed, and a toner supply coefficient. The reference image signal generating section 64 is for generating a predetermined reference image signal. Color conversion processing unit 68
Converts an input image signal into an output image signal using a color conversion matrix based on conversion coefficients. The light amount controller 70 converts the output image signal into a laser on / off signal pulse width modulated according to the pixel value, and the laser on / off signal is output to the laser output unit 30 as an exposure unit. That is, the light amount controller 70 controls the light amount of the laser light emitted from the laser output unit 30. Development controller 7
Reference numeral 2 is for controlling the developing bias, the rotation of the developing roll, the toner supply amount, and the like. Grid power supply 74
Is for controlling the grid voltage of the scorotron charger 38.

An example of the control operation of the image forming apparatus will be described. First, a reference image signal is output from the reference image signal generation unit to the image output unit 58 in accordance with an instruction from the image density control unit 62, and a color patch of each color is formed on the paper P as a sample image. Next, the fixed image density of the color patch is measured by the fixed image density sensor 10, and the detected value is sent to the image density control unit 62. Image density control unit 62
According to the difference between the measured fixed image density and the target fixed image density target value of the reference image stored in the memory in advance, at least one of a charge amount, an exposure amount, a developing bias, a developing roll rotation speed, and a toner supply coefficient. By controlling the image output unit 58 using any of the operation amounts, a desired image quality can be obtained.

Further, according to the difference between the measured fixed image density and the fixed image density target value of the reference image (reference pattern) stored in the memory 52 in advance, the color conversion matrix is fed back to each conversion processing section. By correcting the conversion coefficient, it is also possible to obtain a desired image quality.

Next, the fixed image density sensor 10 will be described. In the present embodiment, the fixed image density sensor 10 is a single color toner (for example, yellow, magenta,
There are four sets corresponding to (black). As shown in FIG.
The fixed image density sensor 10 includes LEDs 12B, 12G, 1
It comprises sensor blocks each having 2R, 12K, a condenser lens (not shown), and photodiodes 18B, 18G, 18R, 18K. The yellow patches 24Y, the magenta patches 24M, the Sian patches 24C, and the black patches 24 correspond to the density patches of each color for each toner single color.
When K, the light source color of the LED 12 (light source spectrum)
Is the complementary color of each toner single color, that is, blue, green, red,
The accuracy of detecting each color density can be improved.

An example of a sensor block corresponding to these density patches is shown in FIG.
Some are attached to 0P. The sensor block 10B has an LED 12B, a condenser lens 14B, and a photodiode 18B.
The sensor block 10R includes an LED 12R, a condenser lens 14R, and a photodiode 18R. The sensor block 10K includes an LED 12K, a condenser lens 14K, and a photodiode 18K. have. In addition,
The block mounting member 10P is provided with a plurality of (four) elongated holes 25 extending in the vertical direction (the direction of arrow H in FIG. 4) with respect to the sheet P, so that the fixed image density sensor 10 can be entirely vertically adjusted (see FIG. 4 in the direction of arrow H), and the individual sensor blocks 10B, 10G, 10R, and 10K can also be adjusted by the elongated holes 26.

Since these sensor blocks have substantially the same configuration, in the following description, the sensor block for one color will be described as the fixed image density sensor 10 unless otherwise specified. In this case, the description will be made with the alphabetic portions of the reference signs omitted.

FIG. 10 shows a schematic configuration of the fixed image density sensor 10 for one color. Fixed image density sensor 1
No. 0 has an LED (light emitting diode) 12, and a sample image 25 having a color patch 24 formed on its surface is located on the emission side. It is preferable that the LED 12 is ideally inclined by 45 degrees with respect to the sample image 25. On the reflection side of the color patch 24 by the LED 12, a condenser lens 14 and a photodiode 18 are located, and the photodiode 18 reflects light reflected from the surface of the color patch 24 of the sample image 25 via the condenser lens 14. Receive light. The photodiode 18 includes the light receiving element 16 that receives light substantially inside the casing.

The fixed image density sensor 10 corresponds to the light quantity measuring device of the present invention, the color patch 24 corresponds to the object of the present invention, the photodiode 18 corresponds to the light receiving means of the present invention, and the LED 12 corresponds to the light receiving means of the present invention. This corresponds to the light source of the present invention. A part of the configuration of the image control unit 56 corresponds to a part of the correction unit and the detection unit of the present invention.

FIG. 6 shows the relationship between the density patch and the spectrum of the light source. The black patch light source is blue in principle,
Any light source color of green, red or white may be used. In the present embodiment, a red LED which has high sensitivity of the light receiving element and is relatively inexpensive is employed.

Here, the principle that the sensor output becomes constant without depending on the amount of fluctuation even when the medium such as the sheet P is displaced will be described. This principle is described in detail in Japanese Patent Application Laid-Open No. 10-175330.

As shown in FIG. 10, the light emitted from the LED 12 is substantially completely diffusely reflected on the surface of the density patch 24 on the paper P. The reflected light is made incident on the light receiving element 16 of the photodiode 18 behind the condenser lens 14 via the condenser lens 14. Here, by providing the light receiving element 16 at the position of the rear focal plane of the condenser lens 14, only the light rays within a specific angle range with respect to the lens optical axis direction among the reflected light from the density patch 24 are received. The light enters the element 16. Since the angle of the specified incident light beam does not depend on the distance between the condenser lens and the paper surface, the amount of reflected light from the density patch is always kept constant.

FIG. 7 shows a basic principle diagram. In the drawing, the center of the condenser lens 14 is O, the front focal point is Fa, the rear focal point is Fb, the front focal length is fa, the rear focal length is fb, the end point of the light receiving element is C, and the distance between Fb-C is r. For convenience, it is assumed that the condenser lens 14 has no aberration, has a thickness of zero, and a width of infinity.

Here, the light is reflected from the reflection point Ai (i = 1, 2, 3,...) In the density patch 24 on the paper surface.
A point Bi (i) formed on the image plane through the condenser lens 14
= 1, 2, 3, ...). In this case, at the reflection point Ai, the angle Si between the light beam passing through the end point C of the light receiving element 16 and the light beam passing through the rear focal point Fb is:
It is always constant, independent of any other parameters. That is, in FIG. 7, the angles s1 and s2 are always the same regardless of the positions of the reflection points A1 and A2 on the paper surface.

FIG. 8 shows actual output characteristics of the fixed image density sensor 10 based on the principle described above. The horizontal axis a is the paper surface variation distance, and the vertical axis V is the output of the photoelectric conversion element. As can be understood from the figure, the sensor output has a flat portion where the amount of variation in the paper surface is substantially constant between several mm. ≦ 3
It is suppressed to a considerable 0.2% or less.

Next, a case where the lens width is finite will be described with reference to FIG. It is considered that the sensor output is considered to be most restricted in a direction perpendicular to the lens optical axis. When the position of the reflection point is outside the lens width, the reflected light is cut off at the edge of the condenser lens 14, so that the amount of light reaching the light receiving element 16 decreases. Further, the reflected light having a constant light amount spreads by an angle s on one side with respect to the lens optical axis and enters the condenser lens 14. Therefore, it is necessary to consider this spread. Thereby, the reflection point position range t at which the output is constant can be expressed as follows.

T ≦ u−2d where u is the lens width of the condenser lens 14 and d is the width of the reflected light spread at the angle s at the position of the condenser lens 14. However, the value of the width d is a number determined by the specifications of the light receiving element 16 and the condensing lens 14, and is generally 1/1 / the lens width u.
Since it is 10 or less, the reflection point position range is basically determined by the lens width of the condenser lens 14. In order to satisfy this condition, the reflection point, that is, the spot area of the irradiation light may be set within a range sufficiently smaller than the lens width u.

Here, by using a visible light LED as a light source, a low-cost and small-sized sensor can be obtained, but as the required level of reading accuracy increases,
The effect of variations in the emission wavelength of the LED cannot be ignored. According to catalogs and the like, blue and green LEDs have a variation of about 20 nm in beak wavelength. Further, even if the manufacturer can obtain LEDs in which the wavelengths are classified in advance, it is known that about 10 mm varies. FIG. 11 shows the variation of the emission spectrum of the blue LED. Thus, the actually available L
The emission spectrum of the ED has variations.

Next, the influence of the sensor output due to the variation of the emission spectrum will be described. In general, from the spectroscopic viewpoint, the output of the reflection type optical sensor is obtained by multiplying the emission spectrum of the light source, the reflection spectrum of the object, and the spectral sensitivity of the light receiving unit for each wavelength, and integrating them with respect to the wavelength. It is known to be obtained by: FIG. 12 shows the relationship between these spectra. Here, the light source is a blue LED, the object is a density patch of highlight, mid, and shadow of a single color of yellow, and the light receiving unit is a Si photodiode.

At this time, the reflection spectrum of the yellow patch, which is the object, is gently changing even in the complementary color region, which is different from the ideal. For this reason, even in a blue emission spectrum region that should be a complementary color, the reflection output curve has a gradient, and the sensor output value that should be obtained by the multiplication thereof is shifted in the wavelength direction of the emission spectrum ( For example, the shift of the peak wavelength).

As described above, since the LEDs have light emission variations (see FIG. 11), even if they have the same color, they have different LEs.
Under D, the sensor output value fluctuates even if patches of the same density and color are read. That is, output difference between sensors (machine difference)
Will occur. As for the degree of the machine difference, the reflectance of the sensor is 5% at the maximum with respect to the variation shown in FIG.
The above variation will be shown. This is 1 for color difference ΔE
This is a value corresponding to 0 or more.

Further, since the machine difference amount varies depending on the density of the patch (object) to be read, it is difficult to make a uniform correction. This is because the curve shape of the patch reflection spectrum in the emission spectrum region is slightly different for each density, and the degree of the influence on the machine difference also changes for each density.

As described above, it is not easy to correct an output variation showing a complicated behavior. Therefore, in the present embodiment, correction of output variation is performed as a first step to accurately and simply detect the degree of variation in sensor output, and as a second step, sensor output correction is performed according to the detected degree of variation. That is, it is performed in two stages. Hereinafter, for simplicity of explanation, Blue LE
A specific example of the case of reading a yellow patch using D will be described. Note that a case where a yellow patch is read using a blue LED will be described, but it goes without saying that the present invention can be applied to other LEDs and other patches.

FIG. 1 is a flowchart showing the flow of the output variation correction process. FIG. 1 shows the detection of the variation of the first sensor output accurately and simply in the stepwise correction of the output variation as variation detection by initial calibration (step 100 in FIG. 1).
To 110), and performing sensor output correction according to the second degree of variation is shown as sensor output correction (FIG. 1).
Steps 112 to 118).

In step 100 of FIG. 1, a yellow patch, which is a detection calibration plate, is read to obtain an output value R (Yc). In a next step 102, a gray patch, which is a comparison calibration plate, is read and an output value R (Yc) is obtained. (Gc) is obtained. In the next step 104, the reflectance difference ΔR at the initial time is obtained from the output difference between the output values obtained in steps 100 and 102.

If the value of the reflectance difference ΔR is held as an absolute value as it is, the sensor output level may change from the initial value due to a change with time of the LED light amount, circuit gain, and the like. Therefore, in the next step 106, the output value R (W) is obtained by reading the reflectance of a standard white plate that can always be read, such as white paper. And the next step 108
Then, the value of the reflectance difference ΔR obtained in step 104 is compared with the relative ratio (出力 R / R) of the reflectance value (output value R (W)) of the standard white plate read in step 106.
(W)), and the relative value (△ R / R (W)) is stored in the memory in the next step 110. That is, the value of the reflectance difference ΔR is stored in the memory as a relative ratio to the reflectance value of a standard white plate that can always be read, such as white paper.

In the next step 112, a sample image (a yellow patch in this embodiment) is read to obtain an output value R (Ys). In the next step 114, the reflectance of a standard white plate such as white paper is read to obtain the current output value R '(W). Then, the next step 11
In step 6, the reflectance difference ΔR is restored by multiplying the read output value R ′ (W) by the relative value held in step 110. That is, when the machine difference correction is performed, the output value R ′ (W), which is the reflectance value of the standard white plate such as paper white, is detected at that time, and the relative value is stored in the memory. The variation can be canceled by multiplying by the value of the relative ratio (ＷR / R (W)). Generally speaking, considering that the light emission principle of an LED is based on the inter-band transition of carriers in a semiconductor, it is considered that the emission spectrum hardly changes with time compared to the change in light amount. , Fluctuations over time can be ignored.

In the next step 118, the above step 1
The read value of the sample image is corrected using the reflectance difference restored in step 16. Although the details will be described later, the reflectance difference ΔR in the entire density range is obtained from the restored reflectance difference ΔR, and step 1 is performed.
The density (output value R (Y
s)), a reflectance difference ΔR ′ (Ys) corresponding to (s)) is obtained. Then, by subtracting the reflectance difference ΔR ′ (Ys) from the density (output value R (Ys)) of the sample image read in step 112, the corrected reflectance difference ΔR is obtained and output.

According to the above procedure, the amount of mechanical difference unique to each sensor can be held only by the initial calibration, so that an appropriate value of the reflectance difference ΔR can always be obtained irrespective of aging.

The above processing will be described in detail. In the first step of the output variation correction, the variation amount is detected, the difference ΔR between the ideal reflectance and the actual reflectance at each density is detected (step 100). To 104). Here, as an ideal method of calculating the reflectance, it is conceivable to calculate the average reflectance using a number of LEDs having a statistically significant amount. Fluctuates, the output level of the measured value fluctuates. For this reason, every time the output level of the measured value changes, measurement or data processing must be performed, and the actual work becomes enormous, which is impractical.

Therefore, in this embodiment, a yellow patch which is a calibration plate for detection is read, and a color patch which always shows a constant sensor output regardless of light emission variation is prepared as a calibration plate for comparison. And compare. From the difference between these reflectances, the degree of variation in the emission spectrum is detected.

As described above, in order to always show a constant sensor output, it is necessary to have a broad reflection spectrum at least in the LED emission spectrum region. A gray patch is a typical example of this. FIG. 13 shows the reflection spectrum of each density of the gray patch. When reading this gray patch, there is no effect on the sensor output even if the emission spectrum varies. At this time, if the density of the gray patch is selected so as to show the same reflectance as the ideal reflectance in the yellow patch used in the present embodiment, the gray patch and the yellow patch are read. Is the ΔR itself. In this case, if both patches can be read within a short period of time, fluctuations due to the environment and measurement conditions can be ignored, so that the degree of variation in sensor output can be accurately and simply detected.

As described above, the reflectance difference ΔR (D (D) at an arbitrary density (the density of the calibration plate used in the present embodiment: Dc)
c) can be determined.

However, the actual reflectance difference ΔR varies depending on the density (reflectance). For this reason, it is necessary to find the reflectance difference ΔR over all the densities (reflectances), but it is not efficient to perform those operations. Thus, in the present embodiment, it is possible to derive a reflectance difference ΔR that enables correction in all density ranges using ΔR (Dc) at an arbitrary density (reflectance).

FIG. 14 shows the reflectance dependence of the reflectance difference ΔR. The vertical axis is a relative value when the peak value of the reflectance difference ΔR is 100%. As described above, the reflectance difference ΔR changes depending on the density (reflectance). However, considering the mechanism, if the change in the curve shape of the patch reflection spectrum in the emission spectrum region due to the density (reflectance) is always the same, the reflectance dependence of the reflectance difference ΔR should not change. That is, as long as the same toner is used in the image forming apparatus, the reflectance dependency of the reflectance difference ΔR has reproducibility. From the above, if the reflectance difference ΔR (Dc) at an arbitrary density can be accurately detected, the reflectance difference ΔR in all the density ranges can be estimated. Therefore, in the present embodiment, the curve shape of the patch reflection spectrum is stored in advance by a function or a polynomial. Therefore, the reflectance difference ΔR (Dc) at an arbitrary density
Can be accurately detected, the reflectance difference ΔR in the entire density range can be obtained from the curve shape of the patch reflection spectrum, and correction, that is, correction to an ideal reflectance value can be performed.

That is, since the reflectivity difference ΔR shows a non-linear change with respect to the reflectivity (FIG. 14), an approximate expression of the curve of this characteristic is obtained, and the output is obtained by performing a non-linear correction. Variations can be almost completely eliminated.

In this case, the effect of the correction differs depending on the density of the calibration plate used. In general,
It is more effective to use a calibration plate in the density range where the reading reflectance target value is the strictest (for example, a shadow region). However, the reflectance dependence of the reflectance difference ΔR is optimized by the balance with the curve shape. What is necessary is just to select the board density.

The above-described non-linear correction requires complicated processing. Therefore, as a simpler method, correction can be performed by linear approximation. Correction by linear approximation is based on the reflectance difference △ R
This is effective depending on the reflectance-dependent curve shape and the correction target level.

FIG. 15 shows the result of correction by linear approximation. Here, the difference when the density of the yellow patch used as the calibration plate is set to highlight / mid / shadow is also shown. As a result, it is understood that the reflectance difference is 1% or less when a calibration plate having a density of mid or shadow is used.

Next, the reflectance difference ΔR (Dc) due to the calibration plate
Will be described. Considering that the light amount of the LED changes due to aging, it is desirable to detect the reflectance difference ΔR (Dc) every time the machine difference correction is performed. However, this calibration (reflectance difference △ R (D
In order to perform (c) detection), considering that this sensor is an online monitor, it is necessary to install not only the calibration plate itself but also a mechanism for reading the calibration plate in the apparatus. It is thought to have an effect on Further, the calibration work may affect the productivity of image output, which is the basic performance of the apparatus itself.
Therefore, considering the entire apparatus, it is not preferable to always perform the calibration work as the machine difference correction.

Therefore, in the present embodiment, the machine difference correction can be performed without using the calibration plate at all times (step 10).
0-110). According to this, by performing a calibration operation at the time of assembling inspection of the sensor, etc., it is possible to detect the reflectance difference ΔR (Dc) before incorporating the sensor into the device, so that it is necessary to perform calibration in the device. There is no need to install a simple mechanism.

That is, as an initial calibration operation, a yellow patch serving as a detection calibration plate and a gray patch serving as a comparison calibration plate are read, and a reflectance difference ΔR (Dc) at the initial time is obtained from an output difference between these. (Steps 100 to 10
4). If the value of the reflectance difference △ R (Dc) is held as an absolute value as it is, the sensor output level may change from the initial value due to a temporal change in the LED light amount, the circuit gain, and the like. Therefore, the value of the reflectance difference ΔR (Dc) is stored in the memory as a relative ratio to the reflectance value of the standard white plate that can always be read, such as paper white (Step 10).
6-110). Then, when performing the machine difference correction, the reflectance value of a standard white plate such as paper white is detected at that time (steps 112 to 114), and the reflectance value is multiplied by the relative value in the memory (step 112). 116), the fluctuation can be canceled. Generally, considering that the light emission principle of an LED is based on the inter-band transition of carriers in a semiconductor, it is considered that there is almost no change in the emission spectrum with time as compared with the change in the amount of light. Fluctuations can be ignored.

According to the above-described procedure, since the mechanical difference amount unique to each sensor can be held only by the initial calibration, an appropriate value of ΔR (Dc) can always be obtained regardless of the change with time.

As described above, in this embodiment, the degree of variation in the sensor output is accurately and simply detected, and the sensor output is corrected in accordance with the detected degree of variation. It has become possible to correct LED emission wavelength variation that cannot be avoided in use.

As a result, a high-precision online monitor with no output difference (machine difference) between the sensors can be performed by using a small-sized and low-cost image monitor sensor. It has become possible to provide a forming apparatus.

In the present embodiment, a case has been described in which a gray patch is used as a color patch that always obtains a constant sensor output. However, the present invention is not limited to this. Any patch (calibration plate) having a broad reflection spectrum may be used.

In the present embodiment, the yellow patch is used as the calibration plate. However, the present invention is not limited to this, and the present invention is not limited to this. A calibration plate of a special color exhibiting a reflection spectrum shape so as to obtain a more remarkable output difference may be used.

In the present embodiment, the detected reflectance difference ΔR (Dc) is used to correct the reflectance difference ΔR in the entire density range.
The linear correction of the reflectance by linear approximation was performed based on the following equation. However, the present invention is not limited to this. The correction may be performed using the LUT prepared in step (1). Further, non-linear correction may be performed.

Further, in this embodiment, the case where the reflectance difference ΔR (Dc) is detected by the initial calibration has been described. However, the present invention is not limited to this, and there is a problem in cost and space. If not, calibration may be performed at all times or at regular intervals.

In this embodiment, a visible light LED is used as a light source. However, the present invention is not limited to this, and an LED other than visible light may be used as a light source.

In the present embodiment, the fixed image density is detected using the sample image. However, the sample image for reading is not prepared in advance, but is usually determined based on an image signal or the like. The fixed image density detection may be performed by using the output image of (1).

Further, in the present embodiment, based on the detection information from the sensor, the control is performed by at least one of the operation amount of the charge amount, the exposure amount, the rotation number of the developing roll during the developing bias, and the toner supply coefficient. However, other operation amounts may be used. The control object using the detection information from the present sensor may be control other than image density control.

Further, in the present embodiment, the simple feedback control according to the difference between the detected value and the target value is performed, but the present invention is not limited to this, and other control methods, That is, control methods such as fuzzy control, neuro control, and learning inference control may be used.

Further, in this embodiment, the color conversion processing is controlled by correcting the conversion coefficient of the color conversion matrix. However, the present invention is not limited to this. For example, the correction may be performed by controlling the gradation of each color.

Further, in the present embodiment, some control is performed using the detection information from the present sensor as a use. However, the present invention is not limited to this, and other uses such as judgment and It may be a warning display or the like.

In the present embodiment, the electrostatic transfer system is used for image formation. However, the present invention is not limited to this, and other image formation systems, such as an ink jet system and a thermal film system, may be used. There may be.

As described above, in the present embodiment, by providing a mechanism for optimizing the positional relationship of the optical axis optical path, the light source which cannot be avoided in using a low-cost LED element. It was possible to correct the variation of the emission spectrum of.

As a result, high-precision on-line monitoring can be performed in a non-contact manner with respect to the density patch on the paper being conveyed, which fluctuates up and down, using a small-sized and low-cost image monitor sensor. An image forming apparatus capable of maintaining full-color image quality can be provided.

[0108]

As described above, according to the present invention,
The detection means accurately and easily detects the degree of variation in the output of the light receiving element, and the correcting means corrects the output of the light receiving element in accordance with the detected degree of variation, thereby avoiding the use of a small and low-cost light source. This makes it possible to correct the emission wavelength variation that cannot be achieved. As a result, even when a light-emitting diode such as an LED is used as a light source, high-precision online monitoring without an output difference (machine difference) between sensors can be performed, so that the size and cost of the sensor can be reduced.

In addition, by using a small and low-cost sensor for measuring the amount of light as an image monitor for controlling the image quality in the image forming apparatus, a highly accurate online monitor can be performed.
An image forming apparatus capable of maintaining high-precision full-color image quality with good reproducibility can be provided.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a flow of an output variation correction process according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a schematic configuration of an image output unit in the image forming apparatus according to the present embodiment.

FIG. 3 is an overall block diagram including an image control unit of the image forming apparatus according to the present embodiment.

FIG. 4 is a block diagram illustrating a schematic configuration of a fixed image density sensor including a plurality of sensor blocks.

FIG. 5 is an explanatory diagram of a combination of a toner single color patch and a sensor.

FIG. 6 is a characteristic diagram showing a relationship between a reflection spectrum of each color patch of yellow, magenta and Sian, and an LED emission spectrum of each color of RGB.

FIG. 7 is a diagram illustrating the principle of an optical system around a fixed image density sensor.

FIG. 8 is a diagram showing a measurement result by a fixed image density sensor.

FIG. 9 is an explanatory diagram of an irradiation area range in a fixed image density sensor.

FIG. 10 is a block diagram illustrating a schematic configuration of a fixed image density sensor according to the exemplary embodiment;

FIG. 11 is a diagram showing variations in the emission spectrum of a blue LED.

FIG. 12 is a diagram showing the relationship between the emission spectrum of a light source, the reflection spectrum of an object, and the spectral sensitivity of a light receiving unit.

FIG. 13 is a diagram showing a reflection spectrum of each density of a gray patch.

FIG. 14 is a diagram showing a reflectance characteristic of an inverse difference (ΔR).

FIG. 15 is a diagram showing a sensor output variation correction result by linear approximation of the reflectance difference (ΔR).

[Explanation of symbols]

 Reference Signs List 10 Fixed image density sensor (light amount measuring device) 12 LED (light source) 14 Condensing lens 18 Photodiode (light receiving element) 56 Image control unit (detection means, correction means)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/46 H04N 1/46 Z 5F041 (72) Inventor Seigo Makita 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Inside Ebina Works Co., Ltd. (72) Makoto Kano, 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Terms (reference) 2C262 AA24 AB11 BA09 FA13 GA02 2G065 AA04 AB04 AB22 AB28 BA07 BA09 BB26 BB27 BC33 BC35 DA01 DA17 5C072 AA01 AA03 AA05 BA02 BA03 BA13 BA19 CA05 CA14 QA14 QA16 RA15 UA11 UA13 UA18 5C007 MM18 MM5 JA10 JA27 KA03 LB02 MA04 MA10 NA03 5F041 AA11 DC84 EE11 FF 13

Claims (14)

[Claims] 1. A light amount measuring apparatus for measuring a light amount by detecting a reflected light from an object irradiated with light by a light source with a light receiving element, wherein the light source is based on each of the reflected light amounts from a plurality of objects. Detecting means for detecting an output variation of the light-receiving element corresponding to a wavelength variation of the emission spectrum of the light-emitting element; and an output value of the light-receiving element based on the amount detected by the detecting means, the output of the light source being illuminated with a reference emission spectrum. A light amount measuring device, comprising: a correcting unit that corrects the light amount to a value. 2. An object is irradiated with spot light by a light source, and reflected light from the object is condensed by a condenser lens on a light receiving element provided at a focal position of the condenser lens to measure the amount of light. In the light amount measuring device, based on each of the reflected light amounts from a plurality of objects, a detection unit that detects output variation of the light receiving element corresponding to a wavelength variation of an emission spectrum of the light source, and a detection amount by the detection unit. Correction means for correcting the output value of the light receiving element based on the light emission of the reference light emission spectrum of the light source based on the light emission based on the light source. 3. The light quantity measuring device according to claim 1, wherein the light source is a light emitting diode. 4. The apparatus according to claim 1, wherein said detecting means detects an output variation of said light receiving element by using calibration plates having different densities as said plurality of objects. Item 2. The light quantity measuring device according to item 1. 5. The light quantity measuring device according to claim 4, wherein at least one of the calibration plates is a calibration plate of a color that does not depend on a wavelength region of at least a light emission spectrum of the light source. 6. The calibration plate according to claim 4, wherein at least one of the calibration plates is a calibration plate having a color that is wavelength-dependent at least in a wavelength region of an emission spectrum of the light source.
The light amount measuring device according to 1. 7. The apparatus according to claim 1, wherein said detection means further comprises a calculation means for calculating a relative value between the detected output variation amount and a predetermined standard detection amount.
The light quantity measuring device according to any one of claims 1 to 7. 8. The light amount according to claim 7, wherein said detecting means further detects a predetermined standard plate, and said calculating means calculates a detected amount of said standard plate as a standard detected amount. measuring device. 9. A storage unit for storing an output variation of the light receiving element detected by the detection unit corresponding to a wavelength variation of an emission spectrum of the light source based on each of the reflected light amounts from a plurality of objects. The apparatus according to claim 1, further comprising a correction unit configured to perform correction based on output variations stored in the storage unit. 10. An estimating means for estimating an output variation amount in another density range from a detection result of an output variation amount at a predetermined density, and an estimating means for correcting the output value based on the estimation result. The light quantity measuring device according to any one of claims 1 to 9, further comprising a correction unit. 11. The apparatus according to claim 1, wherein the correction unit corrects the output value to a predetermined linear characteristic or a non-linear characteristic based on an amount detected by the detection unit. The light quantity measuring device according to claim 1. 12. A color image forming apparatus which detects an output color image and controls a color image forming condition in accordance with the detection result, wherein the color image is formed by a plurality of color materials based on the formation condition. And a light amount measuring device according to any one of claims 1 to 11, wherein the light amount of a sample image using at least one of the plurality of color materials is measured. A color image forming apparatus comprising: detecting means for detecting; and control means for controlling the forming condition according to the detection result. 13. The image forming apparatus according to claim 12, wherein the detecting unit is provided downstream of a final step of the image forming unit.
3. The color image forming apparatus according to 1. 14. The color image forming apparatus according to claim 12, wherein the detection unit includes a selection unit that selects the correction corresponding to the color material.