JP2001343287A - Optical measuring device and color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light quantity measuring device and a color image forming device capable of maintaining highly precise full color picture quality with satisfactory reproducibility. SOLUTION: An optical measuring device is constituted of an LED for irradiating a density patch with lights, a lens 14 for converging the lights reflected from the density patch, and a photodiode 16 for receiving lights from the lens 14. The lens 14 is positioned at a case body 17, and the influence of aberration generated in the peripheral edge area of the lens 14 is removed, and a ring- shaped lens aperture 13 for deciding the valid diameter of the lens is arranged near the lens 14. A circular light absorbing member 11 is fit into the inside face of the lens aperture 13, and the light absorbing member 11 is constituted of a circular resin ring 19 on whose inside face a light absorbing sheet 15 made of black light absorbing materials is formed, and the lights reaching from the lens 14 to the inside face of the lens aperture 13 are absorbed by the light absorbing sheet 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical measuring apparatus and a color image forming apparatus, and more particularly, to an object which irradiates the object with light and reflects the reflected light by a condenser lens. The present invention relates to an optical measurement device for measuring characteristics and a color image forming 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. Lar
sen, Performance Testing of Color-Difference Metri
cs Using a Color Tolerance Dataset, COLOR resea
rch and application, vol.14, Number 3, June 1
989).

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.

Therefore, the present applicants have proposed an optical measuring device, that is, a color image monitor sensor as a means for enabling online output image monitoring after the fixing process (Japanese Patent Laid-Open No. 9-71279). ). The sensors are yellow (Y), magenta (M), and Sian (C)
Blue (B), green (G) and red (R) light emitting diodes (visible light LE
D, hereinafter referred to as an 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 converted to a toner single color density patch (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 to identify each full color, Moreover, it is possible to provide a monitoring sensor which is necessary and sufficient in performance.

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, even when the paper surface fluctuates up and down by about 1 mm, the output of the light receiving element changes by about 15%. With such an output fluctuation, it is difficult to detect a minute difference between the density patches on the sheet 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, in the above-described color image monitor sensor, a large amount of unnecessary reflected stray light is generated in the housing from the lens to the light receiving element, in addition to the light beam directly incident on the light receiving element.

Actually, the stray light reflection component (FIG. 12) is deduced from the output characteristic that should be constant within the predetermined effective range shown by the dotted line in FIG.
(A component included in a shaded portion indicated by a solid line) changes to the added output characteristic.

In order to prevent the influence of such reflected stray light, as shown in FIG. 13, an anti-reflection process such as an anti-reflection film 75 is applied to the inner surface of the housing 77 to prevent the stray light on the inner surface of the housing 77 from being reflected. However, it was not possible to sufficiently prevent reflected stray light. For this reason, the sensor output changes subtly due to the variation between the paper surface distances, and an output characteristic that does not depend on the distance variation cannot be obtained.

In view of the above, it is an object of the present invention to provide an optical measuring apparatus and a color image forming apparatus capable of maintaining high-precision full-color image quality with good reproducibility.

[0019]

In order to achieve the above object, an optical measuring apparatus according to the present invention irradiates an object with light, condenses reflected light from the object with a condenser lens, and collects the reflected light from the object. In an optical measurement device that detects the amount of light with a light receiving element provided near the focal position of the optical lens and measures the characteristics of the object, in a direction intersecting the optical axis of the condenser lens,
And a member provided in the vicinity of the condenser lens so as to include at least a part of the transmission area of the periphery of the condenser lens,
And a suppression unit provided in at least a part of the region including the optical axis side surface of the member and for suppressing reflection.

It is well known that it is effective to suppress the generation of stray light in an optical measuring device. However, the present inventors often find that reflected stray light that affects output characteristics occurs near a condenser lens. I got the knowledge that.

Since the member is provided in the vicinity of the condenser lens, the member blocks a part of the light directed to the condenser lens before reaching the condenser lens, or
The light emitted from the condenser lens is blocked. At this time, among the surfaces of the member, for example, light reaching the surface on the optical axis side such as a surface facing the optical axis of the member or a surface intersecting at an acute angle with respect to the optical axis is reflected and propagated. It is considered that the light enters the light receiving element and becomes reflected stray light which affects output characteristics.

In view of the above, in the present invention, a suppressor for suppressing reflection is provided in at least a part of the region including the optical axis side surface of the member provided near the condenser lens. Therefore, it is possible to prevent the light reaching the surface on the optical axis side from being reflected and entering the light receiving element.

Thus, the generation of reflected stray light can be effectively suppressed, so that an optical measuring device having output characteristics according to the characteristics of the object can be obtained.

Further, in the present invention, it is preferable that the length of the suppressing means along the optical axis is formed to be equal to or greater than the length along the optical axis of the optical axis side surface of the member. this is,
When the length along the optical axis of the suppression means is formed shorter than the length along the optical axis of the optical axis side surface of the member, one region of the optical axis side surface of the member is exposed and reflected stray light is exposed. This is because it may be a source. For this reason, the suppression of the stray light can be improved by forming the suppression means along the optical axis to have a length equal to or longer than the length along the optical axis of the optical axis side surface of the member.

Further, the restraining means can be formed so that the length along the optical axis is not more than 2/3 of the diameter of the condenser lens. The inventor of the present invention can obtain a sufficient reflection suppression effect only by providing a suppression unit having a length along the optical axis that is equal to or less than 2/3 of the diameter of the condenser lens.
It is possible to effectively suppress the occurrence of reflected stray light,
The experimental result is obtained. Therefore, it is possible to effectively suppress the generation of reflected stray light without imposing an excessive cost.

Examples of such a member include a support member for supporting the light-collecting lens so that the light-receiving element is disposed near the focal position of the light-collecting lens, and a region where the output of the light-receiving means is constant. Or a support member also serving as an opening that defines the opening diameter of the condensing lens so as to secure the aperture.

Further, in the present invention, it is preferable that the suppressing means is made of a light absorbing material. The light-absorbing material may be any material that absorbs light, and can be appropriately selected and used. For example, a material having a light absorbing property, a material having a light absorbing property by providing a sheet made of a light absorbing material on the surface or a black surface even if the material itself does not have a light absorbing property. Can be used. Since such a light-absorbing material is easily available and easily processed, it is suitable for cost reduction.

Further, in the optical measuring device of the present invention, a light emitting diode can be used as the light source. In an optical measuring device, a light source plays a large role. 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 an optical measurement device. Therefore, an inexpensive light emitting diode can be employed, and the cost of the optical measurement device can be reduced.

The light source may employ at least one kind of visible light emitting diode of red, green and blue visible light emitting diodes. 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 terms of 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 color image forming apparatus of the present invention, the color image forming apparatus detects the output color image and controls the color image forming conditions according to the detection result. An image forming unit that forms with a plurality of color materials based on formation conditions, and the above-described optical measurement device of the present invention, and detects a light amount of a sample image using at least one of the plurality of color materials. And a control unit for controlling the forming condition in accordance with the detection result.

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 forming 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 above-described optical measurement device of the present invention.
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, in the color image forming apparatus of the present invention, 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.

[0035]

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.

[Basic Principle of Reflection] First, even when the position of a sheet as an example of an object fluctuates, a stable amount of light can be detected. That is, the light incident on the photoelectric conversion element does not depend on the vertical fluctuation of the paper surface. The principle will be described with reference to the drawings.

FIG. 2 shows a basic positional relationship between components in an optical system for explaining the present principle.
As shown in FIG. 2, the present optical system includes a lens 14 having an optical axis CL perpendicular to the paper surface P. Lens 14
A photoelectric conversion element 16 such as a photodiode is provided near the rear focal plane of the lens 14 on the optical axis CL. In addition, the present optical system includes a light source 12 such as an LED whose irradiation optical axis is in a direction different from the optical axis CL of the lens 14, and the irradiation angle of the light source 12 is 45 degrees with respect to the optical axis CL of the lens 14. Is set. The light source 12 irradiates the irradiation area Ar on the paper surface P with irradiation light.

FIG. 3 shows that, of the above optical system, reflected light or scattered light from the paper surface P passes through the lens 14, and
3 shows a state where the light enters the photoelectric conversion element 16 installed on the rear focal plane. In this drawing, for the sake of convenience, it is assumed that the lens has no aberration, the thickness is zero, and the lens width is infinite.

In FIG. 3, PL4 is the lens position, PL
Reference numeral 3 denotes a rear focal plane on which the light receiving side of the photoelectric conversion element 16 is installed, PL5 and PL6 correspond to the fluctuating (up and down in FIG. 2 or 3) paper surface position, and PL1 and PL2 correspond to the fluctuating paper surface positions PL5 and PL6. Reference numeral 11 denotes an optical axis of the lens 7. Further, regarding the lens 14, the center is O, the front focal point is Fa, the rear focal point is Fb, the front focal distance is fa, the rear focal distance is fb, and the end points of the effective light receiving area of the photoelectric conversion element 16 are C and Fb− The distance between C is r
And

Further, different paper surface positions PL5,
When considering light rays reflected from the reflection points A1 and A2 in PL6 and imaged at the imaging plane positions PL1 and PL2 through the lens and up to the imaging points B1 and B2, the light rays are effectively received by the photoelectric conversion element 16. The reflection angles (angles with respect to the direction of the optical axis CL of the lens) at the reflection points A1 and A2 when passing through the end point C of the area are s1 and s2.

The distance between the sheet P and the lens 14 is a
1, a2, the distance between the photoelectric conversion element and the imaging surface is b1,
b2, the optical axis CL of the lens 14 of the reflected light on the paper surface
Let L be the passing point at which a ray parallel to
1, L2. In addition, the light beam reflected at the reflection points A1 and A2, passes through the end point C of the effective light receiving area of the photoelectric conversion element 16, and forms an image at the image forming points B1 and B2.
Pass points passing through L4 are defined as M1 and M2. Furthermore, L
The distance between 1 and M1 is d1, and the distance between L2 and M2 is d2.

In this imaging system, from Newton's equation:
Equations (1) and (2) hold. (A1-fa) / fa = fb / b1 (1) (a2-fa) / fa = fb / b2 (2) Similarities between the triangle B1L1M1 and the triangle B1FbC,
Using the similarity between the triangle B2L2M2 and the triangle B2FbC, the following equations (3) and (4) are established. r / b1 = d1 / (b1 + fb) (3) r / b2 = d2 / (b2 + fb) (4) Further, when the angles s1 and s2 are used in the triangle A1L1M1 and the triangle A2L2M2, the following (5) Equation (6) and Equation (6) hold. d1 = a1 · tan (s1) (5) d2 = a2 · tan (s2) (6) Here, the equations (5) and (6) are substituted into the equations (3) and (4). And the following equations (7) and (8) are obtained. a1 = ((b1 + fb) / r) / (b1 · tan (s1)) (7) a2 = ((b2 + fb) / r) / (b2 · tan (s2)) (8) By substituting equation (8) into equations (1) and (2), the following equations (9) and (19) are obtained. r / tan (s1) = fa (9) r / tan (s2) = fa (10) From the equations (9) and (10), the following equation (11) can be derived. s1 = s2 (11) When the above is generalized, the reflection points Ai (i = i) at the paper surface positions PL5, PL6, etc., which fluctuate in the direction along the optical axis CL, such as the paper surface position PL5, the paper surface position PL6, etc. 1, 2,
3,...), Passes through the lens 14 and forms an image plane P
When considering a light ray to an imaging point Bi formed by L1, PL2, etc., when this light ray passes through the end point C of the photoelectric conversion element 16, the reflection angle si at the reflection point Ai is determined by another parameter. Regardless, it is always constant.

That is, the reflection angle si is always constant even if the reflection area (irradiation area Ar) moves on the paper plane P with the fluctuation of the paper plane P and the reflection point Ai moves. Therefore, if reflection and scattering occur ideally, the reflection point Ai
Is the same, the number of rays included in the reflection angle si is considered to be constant, so the amount of light incident on the photoelectric conversion element 16 between Fb and C is the distance between the sheet P and the lens 14. Or the amount of light accurately depending on the state of each reflection point Ai without depending on the distance between the sheet P and the photoelectric conversion element 16.

Therefore, the light that is reflected (including scattering and diffusion) from a specific area on the paper and enters the photoelectric conversion element does not depend on the distance between the photoelectric conversion elements on the paper surface, but depends on the area. Becomes

Although each line segment is represented on a plane in FIG. 3, in an actual optical system, it can be considered as a rotating body around the optical axis CL of the lens 14. That is, the distance r (line segment FbC) of the photoelectric conversion element 16 is
Although the distance is constant around the optical axis CL of the lens 14, the distance r does not need to be constant in an actual optical system, and the shape of the photoelectric conversion element 16 can be arbitrarily selected, such as a circle or a square. It is possible. Moreover, the photoelectric conversion element 16
It is not necessary to set the position of the optical axis CL of the lens 14 as its center. If the reflected light from the object (paper surface P) is within the rear focal plane PL3 where the light passes through the lens 14 and enters, The lens 14 may be provided at a position that does not include the optical axis CL.

In this manner, only the light reflected within a specific angle range from a point on the paper surface, regardless of the vertical movement of the target object, for example, the paper surface P, is set on the surface including the rear focal position PL3 of the lens 14. By receiving the light by the photoelectric conversion element 16, the characteristics such as the reflectance, the density, and the color of the reflection area can always be accurately measured.

[Principle of Preventing Stray Light] Next, prevention of the incidence of reflected light (stray light) from the inside of the casing of the apparatus to the photoelectric conversion element 16 will be described. Especially when measuring with high accuracy,
It is necessary to prevent even slight stray light.

Ideally, only light rays included in the above-described reflection angle si should enter the photoelectric conversion element 16 via the lens 14, but in reality, the lens 14
Other than the light beam directly incident on the photoelectric conversion element 16 through
For example, as shown in FIG. 4, stray light 60 arriving at the inner surface of the lens aperture 13 facing the optical axis may be reflected and enter the photoelectric conversion element 16.

Therefore, in order to enable more accurate measurement, in the present embodiment, as shown in FIG. 1A, an annular lens aperture for limiting the opening of the lens 14 and holding the lens 14 is provided. 13 is provided with an annular light absorbing member 11 as shown in FIG.

The light absorbing member 11 has an annular resin ring 19 whose outer surface fits into the inner surface of the lens aperture 13.
And a light absorbing sheet 15 made of a black light absorbing material provided on the inner surface of the resin ring 19.
The light absorbing sheet 15 is provided with stray light 60 arriving from the lens 14.
Absorb.

The width W2 of the inner surface of the light absorbing member 11 along the optical axis (W2 is an arbitrary positive number) is equal to the width W1 of the lens aperture 13 along the optical axis (W1 is an arbitrary positive number). ) Or larger than the width W1 (W2 ≧ W1). In the present embodiment, the width is formed larger than the width W1 of the lens aperture 13 along the optical axis.

When the width W2 of the inner surface of the light absorbing member 11 along the optical axis is smaller than the width W1 of the inner surface of the lens aperture 13 along the optical axis, the inner surface of the lens aperture 13 is exposed and exposed. This is because the stray light 60 that has reached the region is reflected and enters the photoelectric conversion element 16.

Accordingly, the width W2 of the inner surface of the light absorbing member 11 along the optical axis is formed to be at least as large as the width W1 of the lens aperture 13 along the optical axis so as to cover at least the inner surface of the lens aperture 13. The stray light 60 can be prevented from being reflected by the inner surface of the lens aperture 13.

The width W 2 of the inner surface of the light absorbing member 11 along the optical axis is determined by the width W 2 of the lens aperture 13 along the optical axis.
1, the light absorbing member 11 is fitted to the lens aperture 13 when the light absorbing member 11 is fitted to the lens aperture 13.
Even if the lens 1 and the lens aperture 13 are fitted in a slightly displaced state, the inner surface of the lens aperture 13 is not exposed and the state of being covered with the light absorbing member 11 can be maintained, which is preferable.

Further, the present inventor has found that the width W2 of the inner surface of the light absorbing member 11 along the optical axis is equal to the diameter of the lens 14 which is 2 mm.
In the case where the ratio is set to about / 3 or less, as shown in FIG. The knowledge that output characteristics can be obtained was obtained.

For this reason, in the present embodiment, the width W2 of the inner surface of the light absorbing member 11 along the optical axis is set to about ／ or less of the diameter of the lens 14. Accordingly, a sufficient stray light suppressing effect can be obtained only by providing the light absorbing member 11, so that other members such as providing an anti-reflection member on the inner surface of the housing in addition to the light absorbing member 11 do not have to be used. So
It is preferable because no extra cost is required.

[Image Forming Apparatus] Next, an embodiment of the present invention will be described based on the basic principle described above. This embodiment is adapted to an image forming apparatus that forms an image by an electrophotographic method.

FIG. 5 shows a main part of an image forming apparatus as an example of an image output apparatus based on the xerographic method according to the embodiment of the present invention. , An image output unit IOT). The image forming apparatus of the present embodiment includes an image output unit IOT and an optical measurement device 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.

The optical measuring device 10 measures the density of an image formed on the paper P, and is installed on the rear side (downstream side) of the fixing device 40. The optical measurement device 10 is connected to an image control unit (not shown) for controlling each unit of the image output unit IOT. In FIG. 5, the image reading unit and the image processing unit are omitted.

Next, an image forming procedure in the image output unit IOT will be described. First, an original image signal input from an input unit (not shown), which reads an original with an image reading device (not shown) such as a scanner or is prepared by an external computer or the like (not shown), Appropriate processing is performed by a processing unit (not shown). The input image signal 5 obtained by this
0 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 photoreceptor 42 is uniformly charged by the scorotron charger 38 before the laser beam is irradiated, and when the uniformly charged photoreceptor 42 is irradiated with the laser beam, the surface thereof is exposed. Then, an electrostatic latent image corresponding to the input image signal 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. As a result, a fixed image on which the toner is fixed is formed on the paper P. Thereafter, the photoconductor 42 is cleaned by the cleaner 36, and one image forming operation is completed. The optical measuring device 10 is installed downstream of the fixing device 40, and detects the image density after fixing.

Next, on the basis of the detection result of the optical measuring device 10, a process of controlling 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 to obtain a desired image quality. Will be described.

First, a reference image signal is output in accordance with an instruction from an image control unit (not shown), and a color patch of each color is formed on a sheet P as a sample image. Next, the fixed image density of the color patch is measured by the optical measurement device 10, and according to the difference between the measured fixed image density, which is the detected value, and the fixed image density target value of the reference image stored in the memory in advance. Then, a desired image quality is obtained by feedback-controlling the image output unit IOT using at least one of the operation amounts of the charge amount, the exposure amount, the developing bias, the developing roll rotation speed, and the toner supply coefficient.

In this case, the optical measuring device 10
High-precision feedback is possible by measuring with high accuracy without being affected by the vertical fluctuation of

Incidentally, 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 in advance, it is fed back to each conversion processing section to convert the color conversion matrix. By correcting the coefficients, it is possible to obtain a desired image quality.

[Optical Measuring Apparatus] FIG. 6 shows a schematic configuration of the optical measuring apparatus 10 of the present embodiment. Optical measuring device 1
0 is roughly divided into an LED (light emitting diode) 12, a lens 14, and a photoelectric conversion element 16, and the basic positional relationship of these components is shown by the above principle (see FIG. 2).

In the present embodiment, the installation location of the photoelectric conversion element 16 is a plane including the focal position of the lens 14 and perpendicular to the optical axis CL. Each component uses an LED as the light source 12, a 15 mm aperture as the lens 14, and a focal length of 2 mm.
A plano-convex lens of 0 mm is used, and a PIN-Si photodiode having an effective detection area of 12 mm is used as the photoelectric conversion element 16. The optical axis CL of the lens 14 is perpendicular to the paper surface P, and the irradiation angle of the light source 12 is 45 degrees with respect to the optical axis of the lens 14.

A sample image 25 having a color patch 24 formed on the surface is located on the emission side of the LED 12.
The LED 12 emits light to the sample image 25 from a position inclined with respect to the sample image 25. The lens 14
Corresponds to the condenser lens of the present invention, the photoelectric conversion element 16 corresponds to the light receiving element of the present invention, and the color patch 24 corresponds to the object of the present invention.

The color patch 24 by the LED 12
The lens 14 and the photoelectric conversion element 16 are located on the reflection side of the. The photoelectric conversion element 16 receives the reflected light from the surface of the color patch 24 of the sample image 25 via the lens 14.

The photoelectric conversion element 16 is housed in a housing 17 as shown in FIG. 1A, and the housing 17 prevents unnecessary light from entering the photoelectric conversion element 16. I have.

An annular lens aperture 13 is provided on the light exit side of the lens 14. The lens aperture 13 has an inner diameter smaller than the outer diameter of the lens 14 and
It has a function as a positioning abutment for positioning the lens 14 on the housing 17 and a function of removing the influence of aberration generated in the peripheral region of the lens 14 and determining the lens effective diameter.

An annular light absorbing member 11 as shown in FIG. 1B is fitted on the inner surface of the lens aperture 13. The width W of the light absorbing member 11 in the direction along the optical axis is formed to be about 2/3 or less of the lens diameter L.

The light absorbing member 11 includes an annular resin ring 19 whose outer surface fits into the inner surface of the lens aperture 13 and a light absorbing sheet 15 made of a black light absorbing material provided on the inner surface of the resin ring 19. The light absorbing sheet 15 is moved from the lens 14 to the lens aperture 13.
Absorbs light that has reached the inner surface of the

As a result, light reaching the lens aperture 13 from the lens 14 is prevented from being reflected and becoming stray light. In addition, the light absorbing member 11 may correspond to a deterrent unit of the present invention, and may completely absorb the arriving light,
The absorption may be made in a range that does not affect the output characteristics of the sensor. Further, the lens aperture 13 corresponds to a member of the present invention.

The light absorbing member 11 is formed of a resin ring 19
It can be easily made by sticking the light absorbing sheet 15 to the inner surface of the device. Of course, the resin ring 19 itself may be made of a light absorbing resin to form the light absorbing member 11.

FIG. 7 shows the measurement results of the optical measuring device 10 when the light absorbing member 11 is provided inside the lens aperture 13. 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 seen from the figure,
The relationship between the paper surface variation distance and the output of the photoelectric conversion element is such that two places where the output is large occur due to the influence of the aberration of the lens 14, but in the area between them, the output variation of the photoelectric conversion element 16 is extremely large. A flat and stable output of the photoelectric conversion element having a small value can be obtained.

As described above, in this embodiment, even when the reflection surface of the object (paper surface) fluctuates in the optical axis direction, measurement can be performed without being affected by the fluctuation. Further, by providing the light absorbing member 11 on the inner surface of the lens aperture 13 provided in the vicinity of the lens 14, it is possible to prevent light reaching the inner surface of the lens aperture 13 from being reflected from the lens. This can effectively suppress the generation of reflected stray light, and enables highly accurate measurement not affected by stray light. In addition, it is possible to simultaneously measure the reflectance, density, color, and the like of the image at the same location with high accuracy, and feed back the result to an image control system or the like.

Further, according to the present embodiment, a compact and low-cost optical measuring apparatus can be provided. Therefore, in an image forming apparatus such as a color printer, the output image quality can be reduced without increasing the size and cost. It can be greatly improved.

In the present embodiment, the optical measuring device has been described as measuring the density. However, the present invention is not limited to this, and the present invention is not limited to this. It can also work. The details will be described below.

First, when colorimetry is performed, light is irradiated from a direction of 45 degrees with respect to the direction perpendicular to the paper surface and light is received in the direction of 0 degrees, or light is irradiated from the direction of 0 degrees and the direction of 45 degrees is irradiated. Is generally used. Therefore, in colorimetry, it is desirable to set the irradiation angle to 45 degrees. However, the angle is not limited to 45 degrees unless the deviation in the diffusion direction of the paper surface is large.

In the optical measuring device 10 shown in FIG.
When the color of the light source 12 is set to red (R), green (G), or blue (B), R, G, B formed on the paper surface
(C) or magenta (M), which are complementary colors of
Alternatively, the density of the irradiation area Ar of the yellow (Y) image is
It can be measured using the output of the photoelectric conversion element 16. Note that any of the above R, G, B, and white light sources may be used as the light source for measuring the density of black (K).

As described above, the present inventors set the light source to R,
As a result of setting and measuring each color of G and B, even if the vertical fluctuation of the paper surface is 1 mm, the required output change can be suppressed to 0.2% or less, and the color difference can be reduced from 0.2 or less depending on the density. It has been found that the color difference is equivalent to a level of about 0.4 which can be distinguished, and that a color difference of a level that cannot be distinguished by the naked eye can be easily distinguished.

The present invention is not limited to the use of the R, G, and B light sources alone. A plurality of light sources, such as R, G, and B, are installed and sequentially turned on to output the output of the photoelectric conversion element. It is also possible to perform full-color image evaluation by obtaining.

For example, as shown in FIG.
R, G, and B main measurement devices 10B, 10G, 10R,
10K is installed at least one each. An example of the optical measuring device will be described. The optical measuring device 10 is capable of supporting four colors corresponding to each toner single color (for example, yellow, magenta, cyan, and black).
Has a pair. As shown in FIG. 9, the present optical measurement device 1
0 denotes LEDs 12B, 12G, 12R, and 12K, lenses 14B, 14G, 14R, and 14K, and photoelectric conversion element 18.
It comprises sensor blocks 10B, 10G, 10R and 10K having B, 18G, 18R and 18K, respectively. When a density patch (color patch) of each color corresponds to a single color of each toner and is a yellow patch 24Y, a magenta patch 24M, a Sian patch 24C, and a black patch 24K, LE
If the light source color (light source spectrum) of D12 is a complementary color of each toner single color, that is, blue, green, and red, the accuracy of each color density detection can be improved.

FIG. 10 shows the relationship between the color patch of each color and the spectrum of the light source. The light source for the black patch may use any light source color of blue, green, red or white in principle. In this embodiment, a red LED which has high sensitivity of the light receiving element and is relatively inexpensive is used. are doing.

Each of these photoelectric conversion elements 16B, 18
Using the outputs of G, 18R, and 18K, the image density of each color of the C image (patch), M image, Y image, and K image on the paper surface P moving in a predetermined direction (the arrow Z direction in FIG. 8) is measured. From these measurement results, full-color image quality can be measured.

As described above, the optical measurement device is used as a high-precision colorimeter for performing full-color image evaluation, and the result is fed back to each step of the image output device, whereby a high-quality image can be obtained. It is possible to obtain.

In this embodiment, the optical measuring device 1
0, the irradiation light from the light source 12 and the output signal are used as they are. However, in order to be able to perform measurement with higher accuracy and high-precision feedback without being affected by the vertical fluctuation of the paper P, the irradiation It is preferable to control the output signal by light and light reception.

That is, the disturbance light incident on the photoelectric conversion element 16 includes light other than the irradiation light from the light source 12,
There is a possibility that disturbance light such as indoor lighting is included. In order to remove this disturbance light, it is conceivable to cover the periphery of the device with a housing, but it may not be possible to completely remove the device. Therefore,
In order to remove the light more completely, the light source 12 is driven by blinking at a predetermined cycle or duty such as emitting a light pulse. As a result, disturbance light is transmitted to the photoelectric conversion element 16.
Appear as an offset in the output of For this reason, by removing the output offset of the photoelectric conversion element 16 in synchronization with the above-described predetermined cycle or duty, more accurate characteristic measurement can be performed. Regarding this technology, for example, transistor technology ((1990-3) p473 to p476)
As described in the above description, it can be realized by driving the light source with a specific light pulse and including an arithmetic circuit of a photoelectric conversion element (PD) including an offset removing circuit such as a sample hold.

Further, in this embodiment, the position of the optical measuring device in the image output device in the image forming apparatus is set as the position for measuring the image after fixing. There may be.

In this embodiment, the case where the present invention is applied to an image forming apparatus using an electrophotographic method has been described. However, any apparatus that forms and outputs an image is limited to the image forming apparatus. However, the present invention can also be applied to an image output device such as an ink jet system or a thermal film system.

Further, in the present embodiment, the case where the present invention is applied to an image forming apparatus has been described. However, the present invention is not limited to an image forming apparatus, and does not include a step of forming an image. In an apparatus for transporting an object on which an image is formed, the apparatus can be applied to measurement of characteristics of an image formed on the object during the transportation, and highly accurate image measurement can be performed.

Further, in the present embodiment, the case where flat paper is used as the object has been described, but the present invention is not limited to this. For example, the target object does not need to be flat like paper, and even if it has a shape having irregularities,
The characteristics of the reflection area can be accurately measured. Therefore, the present invention is applicable not only to measurement of an image but also to measurement of various characteristics of an object.

In the above embodiment, the light absorbing member 11 is provided on the inner surface of the lens aperture 13. However, the present invention is not limited to this structure. For example, the light absorbing member 11 is made of a material having light absorbing properties. Lens aperture 13
Alternatively, it is possible to apply the lens aperture 13 processed so as to have light absorbing properties over the entire inner surface of the lens aperture 13.

In the present embodiment, the light-absorbing sheet 15 is made of a black light-absorbing material. However, the light-absorbing sheet 15 may be any material that absorbs light. Not limited to

In the present embodiment, the structure in which the light absorbing member is provided in the lens aperture 13 on the exit side of the lens 14 has been described. However, the present invention is not limited to the lens aperture 13; A lens such as an abutting member or an aperture member that is supported so as to be arranged at a position, in a direction intersecting the optical axis of the lens 14 and including at least a part of the transmission area on the periphery of the lens 14. Any member provided in the vicinity of 14 is applicable.

In the present embodiment, the light absorbing member 1 is attached to the lens aperture 13 provided on the exit side of the lens 14.
1, the present invention is not limited to this configuration. For example, as shown in FIG. 11A, the lens holder 13 is provided on the entrance side of the lens 14 and the exit side of the lens 14.
a and 13b, the light absorbing member 11 is provided on the optical axis side of both the lens holder 13a provided on the exit side of the lens 14 and the lens holder 13a on the exit side of the lens 14. The absorption sheet 15 is provided by bonding or the like, or as shown in FIG. 11B, the lens holder 13b is provided on the incident side of the lens 14 and the lens holder 13a is not provided on the emission side of the lens 14. In this case, the light absorbing member 11 is provided on the inner surface of the lens holder 13b on the incident side of the lens 14 or the light absorbing sheet is
May be attached. In these cases, the lens holders 13a and 13b correspond to the members of the present invention.

In the present embodiment, the fixed image density is detected using the sample image. However, without preparing a sample image for reading in advance, it is usually determined by judging from an image signal or the like. The fixed image density detection may be performed by using the output image of (1).

Further, in this embodiment, based on the detection information from the sensor, the operation is controlled 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 is performed according to the difference between the detected value and the target value. However, the present invention is not limited to this, and other control methods may be used. That is, control methods such as fuzzy control, neuro control, and learning inference control may be used.

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, and other methods include: 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 this 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 heat-sensitive film system, may be used. There may be.

[0104]

As described above, according to the present invention,
This has the effect that generation of reflected stray light can be effectively suppressed. For this reason, there is an effect that high-precision full-color image quality with good reproducibility can be maintained.

[Brief description of the drawings]

FIG. 1A is a schematic cross-sectional view showing a partial configuration of an optical measurement device according to the present embodiment, and FIG.
It is a perspective view of the light absorption member shown to (A).

FIG. 2 is a schematic configuration diagram of an optical measurement device according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating the principle of an optical system around an optical measurement device.

FIG. 4 is an explanatory diagram for explaining stray light of the optical measurement device.

FIG. 5 is a block diagram illustrating a schematic configuration of an image output unit in the image forming apparatus according to the present embodiment.

FIG. 6 is a block diagram illustrating a schematic configuration of an optical measurement device according to the present embodiment.

FIG. 7 is a diagram showing measurement results obtained by an optical measurement device.

FIG. 8 is a conceptual diagram showing another example of the optical measurement device according to the present embodiment.

FIG. 9 is a block diagram illustrating a schematic configuration of an optical measurement device including a plurality of sensor blocks.

FIG. 10 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.

11A is a schematic sectional view showing a partial configuration of an optical measurement device according to another embodiment of the present invention, and FIG.
(B) It is an outline sectional view showing the partial composition of the optical measuring device of yet another embodiment of the present invention.

FIG. 12 is a diagram showing a measurement result by an optical measuring device having a conventional configuration, and a diagram showing ideal output characteristics from the optical measuring device.

FIG. 13 is a schematic cross-sectional view illustrating a partial configuration of an example of an optical measurement device having a conventional configuration.

[Explanation of symbols]

10, 10B, 10G, 10R, 10K Optical measuring device 10B, 10G, 10R, 10K Sensor block 11 Light absorbing member 12 Light source 13 Lens aperture 13a, 13b Lens holder 14, 14B, 14G, 14R, 14K Lens 15 Light absorbing sheet 16 Photoelectric conversion element 17 Housing 18, 18B, 18G, 18R, 18K Photoelectric conversion element 19 Resin ring 24 Color patch 24Y Yellow patch 24C Sian patch 24M Magenta patch 24K Black patch 25 Sample image 30 Laser output unit 32 Developing device 34 Transfer device 36 Cleaner 38 Scorotron charger 40 Fixer 42 Photoconductor 50 Input unit 60 Stray light

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03G 15/00 303 G03G 15/01 Y 2H030 15/01 H04N 1/028 Z 5C051 H04N 1/028 B41J 3/00 D 5C072 1/19 H04N 1/04 102 (72) Inventor Seigo Makita 2274 Hongo, Ebina City, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Makoto Kano 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Corporation In-house (72) Inventor Hisao Ito 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. EE02 EE13 GG02 HH02 JJ11 JJ30 KK01 LL04 NN06 2G065 AA04 AB04 AB22 AB28 BA09 BB06 BB20 BB50 CA07 2H027 DA09 DE02 EA01 EA02 EA04 EA05 EB04 EC03 EC06 2H030 AA03 AD04 AD16 BB02 ABB1 BB21 BA03 CA06 DA03 DB01 DB22 DC07 5C072 AA01 AA03 BA19 DA02 DA15 DA18 DA21 EA05 QA14

Claims (5)

[Claims] An object is irradiated with light, reflected light from the object is condensed by a condenser lens, and the amount of light is detected by a light receiving element provided near a focal position of the condenser lens. In an optical measurement device for measuring characteristics of an object, provided in the direction intersecting with the optical axis of the condenser lens, and provided in the vicinity of the condenser lens so as to include at least a part of a transmission region of a periphery of the condenser lens. An optical measurement device comprising: a member provided; and a suppression unit provided in at least a part of the region including the optical axis side surface of the member and for suppressing reflection. 2. The apparatus according to claim 1, wherein the restraining means is formed such that a length along the optical axis is equal to or longer than a length along an optical axis of the optical axis side surface of the member. The optical measuring device as described in the above. 3. The optical measuring device according to claim 1, wherein the suppressing means is made of a light absorbing material. 4. A color image forming apparatus for detecting an output color image and controlling a condition for forming the color image according to a result of the detection, wherein a plurality of color materials are formed based on the color image. And an optical measurement device according to any one of claims 1 to 3, wherein the light amount of a sample image using at least one of the plurality of color materials is determined. A color image forming apparatus comprising: detecting means for detecting; and control means for controlling the forming condition according to the detection result. 5. The color image forming apparatus according to claim 4, wherein the detection unit is provided downstream of a final step of the image forming unit.