JP3031207B2 - Image measuring method, image measuring device, and sensor unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic black-and-white or color image forming apparatus such as a copying machine or a printer, and more particularly to the density of an image formed on an image carrier such as a photosensitive drum or the formation of an image. The present invention relates to an image measuring method, an image measuring device, and a sensor unit for measuring a state and the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a black-and-white or color copying machine of the above-described electrophotographic type, after uniformly charging the surface of an image carrier such as a photosensitive drum, the image is exposed to light. An electrostatic latent image corresponding to the information is formed, and an image is formed by developing the electrostatic latent image. At that time, in the case of a color electrophotographic apparatus, a color image is formed by repeating uniform charging, image exposure and development processes for a predetermined number of colors. The above-mentioned color electrophotographic apparatus and the like have uniform charging for forming an image,
Among the components for performing image exposure and development processes, there are environmental and temporal characteristics such as charging characteristics of a photoconductor, output intensity of a light source for performing image exposure, developing bias voltage of a developing device, and charging characteristics of a developer. There are elements that are unstable with respect to changes, and if the characteristics of these constituent elements change, the image quality and density of the halftone image in particular tend to change. In the above-described color electrophotographic apparatus, in particular, when the image density of even one color changes in a halftone image, the color tone of an image obtained by superimposing a plurality of colors fluctuates, and it becomes impossible to reproduce an image of a predetermined color tone. This is often a problem, and various proposals have been made for a method of controlling the density fluctuation of a halftone image.

As a technique relating to the density control of such a halftone image, for example, there is a technique disclosed in Japanese Patent Application Laid-Open No. 35466/1988. A toner density control device disclosed in Japanese Patent Application Laid-Open No. 64-36466 discloses a density control device for forming an arbitrary pattern on a photoreceptor and controlling the pattern density and the read toner density. Is composed of one light emitting unit and a plurality of light receiving units installed at different angles with respect to the light emitting unit.

[0004] Further, the technique according to this proposal will be described. The toner density control device detects a wavelength of, for example, around 800 to 2000 nm, which has a small absorption amount on the surface of the photoreceptor with respect to a reference pattern developed on the photoreceptor. The light is radiated, and the density of the reference pattern is measured based on the amount of reflected light. At this time, the reflected light includes a diffuse reflection component reflected by the toner and a regular reflection component reflected by the surface of the photoreceptor in a portion where there is no toner.

FIG. 19 shows an output characteristic when the toner amount on the photosensitive member is measured by a density sensor by the method according to the above proposal. Generally, in a highlight region where the amount of toner is small, the specular reflection component rapidly decreases in accordance with the amount of toner. Therefore, it is desirable to measure the amount of toner based on the output of the specular reflection component in terms of accuracy. However, in a region where the amount of toner is large, the diffuse reflection component increases with respect to the specular reflection component. Does not hold. Therefore, in an area where the amount of toner is large, a method of detecting the amount of toner using the output of the diffuse reflection component by the second light receiving unit is used. If a pinhole or the like is arranged on the light receiving surface of the light receiving unit for detecting the regular reflection component and the amount of the diffuse reflection component incident on the light receiving unit for detecting the regular reflection component is minimized, the toner amount can be reduced. The detection accuracy in a large area can be improved as shown in FIG.

[0006]

However, the above-mentioned prior art has the following problems. That is, in the case of the apparatus disclosed in JP-A-64-35466, a pinhole or the like is provided on the light-receiving surface of the light-receiving unit for detecting a specular reflection component in order to improve detection accuracy in an area where the amount of toner is large. It is necessary to arrange and minimize the amount of diffuse reflection component incident on the light receiving unit for specular reflection component detection. In this case, however, it is necessary to precisely match the pinhole and the incident optical axis. However, there is a problem that high accuracy is required for assembling the density sensor and the like. Further, in the case of the device according to the above proposal, if the specular reflection component and the diffuse reflection component are accurately separated to further improve the detection accuracy, the length of the incident optical path incident on the light receiving portion for specular reflection component detection is increased. Therefore, there is a problem that the size of the apparatus is increased. Further, in the case of the apparatus according to the above proposal, if the photoconductor on which a toner image of an arbitrary pattern is formed has a position change due to the influence of eccentricity or the like, the amount of light incident on the light receiving portion for detecting the regular reflection component is reduced. Because of the rapid decrease, the detection accuracy of the toner density is reduced, and if the relative position between the density sensor and the photoconductor changes, there is also a problem that stable measurement of the toner density becomes impossible.

Further, in the case of the apparatus according to the above proposal, as described above, it is mainly to detect the density fluctuation by measuring the amount of toner on the photoreceptor and to control the density by selecting an appropriate parameter. Done in The parameters at that time are the intensity of the light source that performs image exposure and the charged potential of the photosensitive drum, but since the control was not necessarily performed by grasping the essential cause of the density fluctuation, There is a problem that the density of the toned image cannot be controlled with high accuracy. One of the reasons is that although it is possible to measure the amount of toner on the photoconductor, it is possible to measure the state of formation of an image formed on the photoconductor, and a sufficiently small and highly accurate sensor is required. It was not.

More specifically, the image quality of the halftone image formed on the photoreceptor is determined not only by the image density, that is, the amount of toner, but also by the spread or disturbance of the fine line image or dot image. Is done. However, in the case of the apparatus according to the above proposal, since only the average density of a certain area of the image formed on the photoconductor is measured, the spread or disorder of the fine line image or the dot image is detected. It is not possible to detect in a state where the spread or disturbance of these fine line images or dot images is caused by any image forming parameters, and it is possible to accurately control the density of the halftone image. I couldn't do that.

In order to accurately control the density of a halftone image, in order to detect the spread or disturbance of a fine line image or a dot image in addition to the image density, an image formed on a photoconductor is required. It is also conceivable to take an image using a video camera or the like, and analyze the image captured by the video camera or the like using an image analysis device that performs a Fourier transform or the like to analyze an image formation state.

However, in this case, the structure of the apparatus for detecting the state of image formation becomes very complicated, which not only increases the size and cost of the apparatus but also analyzes the state of formation of the detected image. Requires a certain amount of time, the state of formation of the image formed on the photoreceptor is immediately detected, and the detected state of formation of the image is used as an image forming parameter of a color electrophotographic apparatus or the like. There is another problem that the density of the halftone image cannot be accurately controlled by feedback.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is not only to reduce the amount of toner of an image formed on an image carrier such as a photoconductor, but also to achieve the object. Another object of the present invention is to provide an image measuring method, an image measuring device, and a sensor unit which can detect even an image forming state and have a simple configuration.

Another object of the present invention is to provide an image measuring method and an image measuring method capable of performing stable and accurate density measurement even when the relative position between the image carrier and the light amount detecting unit changes. It is to provide a measuring device and a sensor unit.

Still another object of the present invention is to detect an image forming state and feed back the detected image forming state to the image forming apparatus to determine the image forming state. It is an object of the present invention to provide an image measuring method, an image measuring device, and a sensor unit which can control the image quality.

[0014]

Means for Solving the Problems] image measuring method according to claim 1 of the present invention, the measurement image on the image bearing member collimated light
The image is irradiated, the reflected light is made incident on the condensing optical system, and from the measured values of the reflected light amounts at a plurality of locations in the region including the vicinity of the infinity focal position of the reflected light by the condensing optical system, on the image carrier.
An image measuring method characterized in that the state of formation of the image to be measured is measured. Further, according to claim 2
In the image forming method, parallel light is projected on an image to be measured on an image carrier.
And the specular reflection light from the image carrier and the
Diffuse reflected light is made incident on the condensing optical system, and the reflected light
Multiple in the area including near the focal position at infinity by the focusing optics
From the measured value of the light intensity distribution of the reflected light at the location, on the image carrier
The feature is to measure the formation state of the image to be measured
Image measurement method.

According to a third aspect of the present invention, there is provided an image measuring method for analyzing an abnormality of an image forming unit which has formed a measured image from a measured state of the measured image on the image carrier. The image measuring method according to claim 1 or 2, wherein:

Further, in the image measuring method according to a fourth aspect of the present invention, the light amount measurement at least at a position near an infinity focal point of the light-collecting optical system is used as a light amount detection value at a plurality of positions by the reflected light amount detection unit. Characterized by using a value
An image measuring method according to any one of claims 1 to 3 .

Still further, according to a fifth aspect of the present invention, there is provided an image measuring apparatus, wherein the parallel light source irradiates the measured image on the image carrier with parallel light, and the parallel light source irradiates the parallel light with the parallel light source. A condensing optical system that condenses the reflected light from the image to be measured, a light amount detecting unit that detects light amounts at a plurality of locations in an area including the vicinity of the infinity focal position of the light collecting optical system, and a light amount detecting unit. Image bearing from detected values of reflected light amount at multiple locations
Measuring means for measuring the formation state of the image to be measured on the holding body ,
An image measuring device comprising:

Further, in the image measuring apparatus according to a sixth aspect of the present invention, the parallel light source may include an image to be measured on the image carrier.
6. The image measuring apparatus according to claim 5 , comprising a light emitting source for generating light for irradiating an image , and a parallel optical system for collimating the light emitted from the light emitting source.

Further, in the image measuring apparatus according to a seventh aspect of the present invention, a light emitting source for generating light for irradiating an image to be measured on an image carrier and light emitted from the light emitting source are collimated. A light-collecting optical system that collects reflected light from an image to be measured generated by the irradiation of the parallel light, and a light-amount detecting device that detects light amounts at a plurality of locations in an area including a position near an infinity focal point of the light-collecting optical system. And a measuring means for measuring a state of formation of an image to be measured on the image carrier from detection values of reflected light amounts at a plurality of positions by the light amount detection unit.

Further, the image measuring apparatus according to claim 8 of the present invention, the light emitting source, an image measuring apparatus according to any one of claims 5 to 7, characterized in that it consists of a coherent light source is there.

Further, in the image measuring device according to a ninth aspect of the present invention, the light quantity detecting section is constituted by a plurality of light receiving sections capable of measuring a light quantity distribution, and the measuring means is provided at a plurality of places by the light quantity detecting section. From the reflected light distribution on the image carrier
Claims, characterized in that measuring the formation state of the measured image
An image measuring device according to any one of claims 5 to 8 .

[0022] Also further, the image measuring apparatus according to claim 10 of the present invention, the light amount detector is made integral n-dimensional light receiving element (n> 1), the measuring means is the n-dimensional light receiving element The image measurement according to any one of claims 5 to 9, wherein a state of formation of an image to be measured on the image carrier is measured by using a detection value corresponding to the light receiving position at (a) as a light amount at the location. Device.

Furthermore, the image measuring apparatus according to claim 11 of the present invention includes an image carrier measured by the measuring means
From the state of formation of the measured image on the body, the measured
An image measuring apparatus according to any one of claims 5 to 10, characterized in that it comprises an analysis means for analyzing an abnormality of the image forming means to form an image.

In the image measurement apparatus according to a twelfth aspect of the present invention, at least a light amount measurement value near an infinity focal position of the light-collecting optical system is used as the light amount detection value at a plurality of positions by the light amount detection unit. Claims for use
An image measuring device according to any one of claims 5 to 11 .

Further, a sensor unit according to a thirteenth aspect of the present invention includes a light emitting source for irradiating an image to be measured on an image carrier, and irradiating the light emitted from the light emitting source with parallel light. A condensing optical system that condenses the reflected light from the measured image generated by the above, and disposed near the infinity focus of the condensing optical system, and reflects the reflected light from the measured image after passing through the optical system. A sensor unit comprising a light receiving element for detecting at a plurality of locations, wherein the light emitting source, the condensing optical system, and the light receiving element are integrally formed.

[0026]

The image measuring method according to any one of the first to third aspects of the present invention has the function as described in these image measuring methods.

In the image measuring apparatus according to a fourth aspect of the present invention, first, the light emitted from the parallel light source is irradiated on the image to be measured by the condensing optical system. Then, the light scattered by the image to be measured enters the light-collecting optical system, and is guided to a light-amount detecting unit provided in a region including the vicinity of the infinity focal position of the light-collecting optical system. On the other hand, the light that is specularly reflected without being scattered by the image to be measured enters the condensing optical system as parallel light, and is condensed by this condensing optical system,
The light is guided to a position conjugate with the light source on the light amount detection unit.

Here, since the light quantity detecting section is configured to detect the light quantity at a plurality of locations in the area including the vicinity of the focal point at infinity of the condensing optical system, light other than light scattered by the image to be measured. In addition, by detecting evenly reflected light that is not scattered by the image to be measured at a different position on the light amount detection unit, much image information can be obtained.

First, specularly reflected light is incident on the light quantity detecting section at a position conjugate with the light emitting section, and diffusely reflected light is incident on other areas. Further, as the light amount detection unit, for example, a one-dimensional or two-dimensional split sensor can be used, and the light that is specularly reflected without being scattered by the image to be measured enters the condensing optical system as parallel light. Then, since the light is condensed by the light condensing optical system and guided to a position conjugate with the light source on the light amount detection unit, the area of the light receiving unit for the specularly reflected light is set to a small area in the same manner as the light source, It can be reliably separated from the diffusely reflected light, and is excellent in the ability to detect the toner density particularly in a high density portion. Further, by measuring the diffuse reflection component by dividing it with a parallel light beam, the condensing optical system becomes partially coherent, so that the power spectrum can be detected.

By arranging the image to be measured at the infinity focal position of the condensing optical system, the diffuse reflected light and the specular reflected light are collimated after passing through different portions of the condensing optical system. Therefore, they do not intersect each other. Therefore, the regular reflection light and the diffuse reflection light do not match on the light amount detection unit. That is, the specularly reflected light and the diffusely reflected light always enter different positions on the light amount detection unit and do not interfere with each other. Therefore, according to the present invention, even if the relative position between the sensor unit and the image to be measured fluctuates, the specularly reflected light and the diffusely reflected light at one point pass through different positions of the light collecting optical system, They are roughly parallel. Therefore, the regular reflection light and the diffuse reflection light hardly match on the light amount detection unit,
The output of the light amount detection unit hardly fluctuates, and a stable and accurate output can be obtained.

Further, as described in claim 7 of the present invention, by using a coherent light source as a light emitting source, the light amount detecting section is provided as an optical Fourier transform surface, and obtains a power spectrum of an image. be able to. By analyzing the power spectrum, it is possible to grasp the disorder and the degree of the developed image and the cause of the fluctuation, and it is possible to perform an appropriate treatment.

According to a tenth aspect of the present invention, there is provided an image measuring apparatus, comprising: an analyzing unit that analyzes an abnormality of the image forming unit that has formed the measured image based on a formation state of the measured image measured by the measuring unit. Since the image forming unit is provided, the abnormality of the image forming unit can be analyzed by the analyzing unit.

Further, in the sensor unit according to the twelfth aspect of the present invention, since the light emitting source, the condensing optical system and the light receiving element are integrally formed, the image measuring device having the above-mentioned operation is unitized. It can be made compact.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment.

FIG. 1 shows an embodiment of the image measuring apparatus according to the present invention.

In FIG. 1, reference numeral 1 denotes a light source. As the light source 1, for example, coherent light (interferable light) having a wavelength of 780 nm or longer is used.
A semiconductor laser that emits a laser beam is used. The coherent light source 1 is disposed on the object-side infinity focal plane of the converging optical system 2 composed of a convex lens, that is, on a plane at the position of the focal length f of the converging optical diameter 2, and is emitted from the coherent light source 1. The divergent light is collimated by the condensing optical system 2 to form a photoconductor 3 as an image carrier.
Irradiated on top. Here, the “focal point” is, as is well known, a point at which a ray incident parallel to the optical axis intersects with the optical axis, or a ray emitted from that point travels parallel to the optical axis after passing through the optical system. These points are referred to as an image-side focal point, and the latter is referred to as an object-side focal point. The object-side focal point and the image-side focal point are points conjugate to infinity points in the image space and the object space, respectively. Therefore, here, the “focal point” of the condenser optical system 2
Is referred to as “infinity focal point”, and a plane orthogonal to the optical axis of the condensing optical system 2 in which the “infinity focal point” exists is referred to as “infinity focal plane”. Although the coherent light source 1 is arranged on the object-side infinity focal plane of the light-collecting optical system 2, it is not always necessary to arrange the coherent light source 1 exactly on the object-side infinity focal plane. You may comprise so that it may be arrange | positioned near the position along the optical axis direction of a focal plane.

As the photoconductor 3, for example, a photoconductor formed in a drum shape or a belt shape of a color image forming apparatus such as a color copying machine or a printer is used. When measuring an image at a timing other than the process of forming an image, a test image having a predetermined density (for example, a halftone density) is formed in a predetermined pattern. The test image is formed with a predetermined image structure such as a line screen or a halftone screen as shown in FIG. 4A according to the image forming conditions of the color image forming apparatus. Also, the test image above
Instead of forming an image of one type of density such as halftone,
If necessary, the image may be formed over a plurality of densities or conditions such as low density, halftone density, and high density.

Further, the photosensitive member 3 is arranged at a focal point on the image side of the condensing optical system 2 at infinity, and the specularly reflected light from the photosensitive member 3 is, as shown in FIG. An optical sensor 5 as a light amount detection unit which is re-entered into the condensing optical system 2 as it is and is disposed on the object-side infinity focal plane of the condensing optical system 2, that is, on a plane at the focal length f of the condensing optical diameter 2 It is led to. At this time, the specularly reflected light from the photoreceptor 3 enters the condensing optical system 2 again as parallel light, is condensed by the condensing optical system 2, and is converged on the object side of the condensing optical system 2. Since the light is guided to the optical sensor 5 disposed on the far focal plane, the position where the specularly reflected light is collected on the optical sensor 5 is a substantially point-like position conjugate with the coherent light source 1.

On the other hand, when the toner of the test image exists on the photoconductor 3, the light collimated by the condensing optical system 2 emits the test light formed on the photoconductor 3 as shown in FIG. The diffusely reflected light scattered by the toner 4 of the image and scattered by the toner 4 re-enters the condensing optical system 2 in a spread state, and the optical sensor Irradiation is performed substantially uniformly over a wide area on the surface 5.

Here, as shown in FIG. 2, the light sensor 5 disposed on the object-side infinity focal plane of the condensing optical system 2 emits light of specularly reflected light on the photoreceptor 3. The first detection unit 5a in the area A1 having a small diameter for detecting the first detection unit 5a and the first detection unit 5
When the test image formed on the photoreceptor 3 has a predetermined image structure, the second detection unit 5b in the area A2 larger than a is located at a predetermined distance from the regular reflection light. 2 for detecting the reflected light of the side band irradiated on each
The third detection units 5c and 5c of the two areas B and the first
And a fourth detection unit 5d of a plane square area C for emitting light of a background part which is irradiated substantially uniformly to regions other than the third detection units 5a to 5c. As the optical sensor 5, a sensor composed of a silicon photodiode divided into the first to fourth detection units 5a to 5d as described above is used. However, the present invention is not limited to this. As shown in FIG. 3, the optical sensor 5 includes a first to a fourth detectors 5a to 5d shown in FIG. A one-dimensional or two-dimensional CCD sensor 10 or the like arranged in a zigzag manner, an SPD element divided into first to fourth detection units, or the like may be used.

Here, in FIGS. 1 and 2, various parameters are as follows. Focal length of focusing optical system 2 f (mm) wavelength of semiconductor laser λ (mm) screen pitch on image plane d (μm)

In this case, the image height h on the image plane corresponding to the surface of the optical sensor 5 is represented by h = f · tan θ, and the effective aperture value of the converging optical system 2 in this embodiment ( NA value) is set to be very small, and tan θ = θ = sin θ. That is, the surface of the optical sensor 5 and the photoreceptor 3 satisfy the condition that they are regarded as optical Fourier transform surfaces.

In this case, a sine wave image having a period of d (μm) on the photoconductor 3 is converted into an optical Fourier transform plane, that is, an optical sensor 5.
Since it appears as a spectrum at a position of D = f × λ / 2d × 10 ⁻³ (mm) from the principal ray on the surface, it has a spectrum distribution as shown in FIGS. 4B and 2A. .
Fig. 2 (B) shows the surface of the optical sensor 5 corresponding to this spelling.
By arranging the light receiving section 5c having the plurality of light receiving areas B having the form described above, the spectrum of the toner 4 image on the photoconductor 3 can be detected.

That is, an image having a line screen structure as shown in FIG. 4A formed on the photoreceptor 3 ideally has a step-like density distribution as shown in FIG. 5A. However, in reality, the density distribution can be approximated by a sine wave image having a period of d (μm) as shown in FIG. This figure 5
When a sine wave image having a period of d (μm) as shown in FIG. 4B is optically Fourier transformed, an average density of the sine wave image having a period of d (μm) is obtained at the center as shown in FIG. A corresponding peak appears, and two sidebands corresponding to the period of the sine wave image appear at positions separated by the distance D given by the above equation on both sides of the central peak signal.

With the above arrangement, the image measuring apparatus according to this embodiment measures not only the toner amount of an image formed on an image carrier such as a photosensitive member but also the state of image formation as follows. The density can be detected, and even when the relative position between the image carrier and the detection unit changes, stable and accurate density measurement can be performed. Further, in this embodiment, it is possible to detect the image formation state, immediately feed back the detected image formation state, and control parameters for determining the image formation state.

That is, in this embodiment, first, before the image measurement, a test image of a predetermined density (for example, halftone density) is formed on the photoreceptor 3 as shown in FIG. It is formed with a line screen structure. Next, as shown in FIG. 1, divergent light LB composed of a laser beam is emitted from the coherent light source 1, and the divergent light LB emitted from the coherent light source 1 is collimated by the condensing optical system 2. The light is irradiated onto the photoconductor 3. Then, the specularly reflected light that is specularly reflected by the surface of the photoreceptor 3 enters the condensing optical system 2 again as parallel light, and the condensing optical system 2 causes the light of the light sensor 5 of the optical sensor 5 as shown in FIG. The light is guided onto one light receiving section 5a. On the other hand, when the test image toner 4 exists on the photoconductor 3, the light collimated by the condensing optical system 2 is scattered by the test image toner 4 formed on the photoconductor 3, The diffusely reflected light scattered by the toner 4 enters the condensing optical system 2 again in a spread state as shown in FIG. The upper fourth light receiving portion is irradiated substantially uniformly over a wide area.

In this embodiment, as shown in FIG. 4, the test image formed on the photoreceptor 3 has a line screen structure with a screen pitch d (μm). The surface of the photosensor 5 and the photoconductor 3 are regarded as optical Fourier transform surfaces, as described above. Therefore, as shown in FIGS. 4B and 4C, the light scattered by the test image having the line screen structure includes the DC component applied to the central portion 5a of the optical sensor 5 and the photosensitive member 3 The sine wave image having a period of d (μm) is located at a position separated by D = f × λ / 2d × 10 ⁻³ (mm) from the DC component which is the principal ray on the optical Fourier transform surface, that is, the optical sensor 5 surface. Appears as a spectrum. Since a plurality of light receiving elements 5a to 5d having the configuration shown in FIG. 2B are arranged on the surface of the optical sensor 5 corresponding to these spells, the spectrum of the toner 4 image on the photoreceptor 3 is obtained. Can be detected.

FIG. 6 schematically shows the effect of the present invention when the photosensitive member surface is defocused in the optical axis direction. The photoreceptor 3 is arranged at the image-side infinity focal position of the condensing optical system 2, so that the specularly reflected light indicated by the dotted line in the drawing is focused on the object-side infinity focal plane by the condensing optical system 2. The specular reflection light without defocus indicated by the solid line above coincides with the light sensor 5. On the other hand, the diffuse reflected light represented by the one-dot chain line does not coincide with the regular reflected light on the optical sensor 5 because it travels in parallel with the regular reflected light by the condensing optical system 2.
Therefore, according to the embodiment of the present invention, since the specular reflection light and the diffuse reflection light are received at different positions on the optical sensor 5, defocus free is realized as the toner amount measuring device.

In this embodiment, the light source 1 is a coherent light source, and the specular reflection component is strong and the diffuse reflection component is weak on the surface of the photoreceptor 3. Therefore, the condensing optical system 2 used in this embodiment is It can be considered as a partially coherent optical system.
Given as an optical Fourier transform surface of the surface. As described above, when the condensing optical system 2 has high coherency and the test image on the photoconductor 3 has a screen structure as shown in FIG. 4A, the light intensity distribution on the surface of the optical sensor 5 is As shown in FIG. 4B, the light intensity distribution on the line aa ′ in FIG. 4B is composed of a DC component at the center and spatial frequency components of the screens on both sides thereof. 4 (C). This is the power spectrum of the test image formed on the photoreceptor 3, and the central part is a value corresponding to the DC component, that is, the average toner amount.
The side bands on both sides correspond to the spatial frequency spectrum of the screen.

As described above, the optical sensor 5 for detecting these light intensity distributions is divided into first to fourth light receiving sections 5a to 5d as shown in FIG. The first light receiving section 5a of the optical sensor 5 detects only the DC component, the second light receiving section 5b detects the low frequency sideband of the first light receiving section 5a, and the third light receiving section 5c. Detects the power spectrum of the screen structure, and the fourth light receiving unit 5d
This is for detecting components other than 1, A2, and B.

As long as the image formed on the photosensitive member 3 is not disturbed, the output corresponding to each area changes according to the area ratio of the line screen as shown in FIG. . The output of the first light receiving portion 5a of the optical sensor 5 matches the regular reflection light amount of the conventional toner density detecting device. Further, the output of the second light receiving section 5b changes in accordance with the image structure on the photoconductor 3 in the electrophotographic color image forming apparatus. Here, in the above electrophotographic color image forming apparatus, parameters relating to the image structure on the photoconductor 3 include: 1) photoconductor charging potential V _H (volt) 2) post-exposure potential V _L (volt) 3) such bias potential V _B (volt) 4) developer tribo value T _R (coulombs / g) 5) the developer toner concentration T _C (%) can be mentioned.

According to this embodiment, it is possible to detect when an abnormality occurs in each of the above parameters 1) to 5). Here, for simplicity, the parameter of the 1) to 3), as shown in FIG. 8, defining a development contrast V _D and the cleaning field V _C as follows. 6) Development contrast V _D = V _B −V _L 7) Cleaning field V _C = V _H −V _B At this time, each parameter is set to each light receiving section 5 a of the optical sensor 5.
FIG. 9 is a table summarizing the magnitude of the effect on the output of .about.5d.

[0053] Now, there are variations in the development contrast V _D, 3) the bias potential, 4) the developer tribo value, 5) the developer toner concentration, 7) when a parameter such as the cleaning field does not change, the optical sensors 5 The DC components (the output A1 of the optical sensor 5a) and the screen spectrum (the output B of the optical sensor 5b) are most affected during the output.
And the result is as shown in FIG. Further, it can be seen that the influence on the outputs A2 and C of the optical sensor 5 is small.

[0054] Similarly, with respect to the variation of the cleaning field V _C, as shown in FIG. 11, the output C of the optical sensor 5d is most affected, the output A1 of the optical sensor 5a also affected by low density portion You can see that.

[0055] Further, with respect to the variation of the developer tribo values T _R, as shown in FIG. 12, greatly affect the output B, especially medium density region of the optical sensor 5c, the output A of the optical sensor 5a
It can be seen that there is a slight effect even in the high concentration region. That is, when the developer tribo value T _R is normal, 13
(A), the while the peak of the sideband of the Fourier spectrum is increased, when the developer tribo value T _R is abnormal, as shown in FIG. 13 (A), the Fourier spectrum Sideband peaks are lower.

Further, the fluctuation of the developer toner concentration T _C is as follows.
As shown in FIG. 14, the influence on the output A1 of the optical sensor 5a is great, the output A2 of the optical sensor 5b is slightly affected, and the output B of the optical sensor 5c is affected. Is affected by the development contrast V _D
Since the extent influence on the output B not greater, it is possible to identify the variation factor of the variation of the change and development contrast V _D of the developer toner concentration T _C.

Therefore, each light receiving section 5a of the optical sensor 5
It is possible to automatically analyze the state of image formation by automatically detecting the fluctuation of the output from .about.5d using a control circuit such as a CPU or a comparator of a hardware circuit.

FIG. 15 is a flowchart showing the analysis operation of the control circuit including the CPU and the like.

First, the output A of the light receiving section 5a of the optical sensor 5
It is determined whether or not the difference between 1 and the reference value is within a predetermined range (step 1). If the difference between the output A1 of the light receiving section 5a and the reference value is within the predetermined range, the light receiving section 5c is determined. It is determined whether or not the difference between the output B and the reference value is within a predetermined range (step 2). If the difference between the output B of the light receiving unit 5c and the reference value is within a predetermined range, step 1 is performed again. And the light receiving section 5c
If the difference between the output B and the reference value is not within the predetermined range,
It is determined that the developing tribo is defective (step 3).

If the difference between the output A1 of the light receiving portion 5a of the optical sensor 5 and the reference value is not within a predetermined range, the light receiving portion 5a
It is determined whether or not the difference between the output B and the reference value is within a predetermined range (step 4). If the difference between the output B of the light receiving unit 5c and the reference value is not within the predetermined range, the developing contrast is determined. Is determined to be abnormal (step 5). On the other hand, when the difference between the output B of the light receiving unit 5c of the optical sensor 5 and the reference value is within a predetermined range, it is determined whether the difference between the output C of the light receiving unit 5d and the reference value is within the predetermined range. Is determined (step 6), and if the difference between the output C of the light receiving section 5d and the reference value is not within a predetermined range, it is determined that the cleaning field is abnormal (step 7).

Further, when the difference between the output D of the light receiving portion 5d of the optical sensor 5 and the reference value is within a predetermined range, the difference between the output A2 of the light receiving portion 5b and the reference value is within the predetermined range. It is determined whether or not the toner density is present (step 8). If the difference between the output A2 of the light receiving unit 5b and the reference value is not within a predetermined range, it is determined that the toner density is abnormal (step 9). If the difference between the output A2 of the light receiving unit 5b and the reference value is within a predetermined range, the process returns to step 1.

As described above, the fluctuation of the output from each of the light receiving sections 5a to 5d of the optical sensor 5 is analyzed by using a control circuit such as a CPU to determine which of the image forming conditions causes the fluctuation. Automatic detection can be performed, and the detected fluctuation factors of the image formation state can be immediately fed back to control parameters for determining the image formation state.

FIG. 16 shows an embodiment of the sensor unit according to the twelfth aspect of the present invention. The same parts as those of the above embodiment are denoted by the same reference numerals and described. A light-emitting source for irradiating the image to be measured, a condensing optical system for collimating light emitted from the light-emitting source, and condensing reflected light from the image to be measured generated by the irradiation of the parallel light; Placed near the infinity focus of the optical optics,
A light-receiving element that detects reflected light from the image to be measured after passing through the optical system at a plurality of locations; and the light-emitting source, the condensing optical system, and the light-receiving element are integrally formed. .

That is, in this embodiment, as shown in FIG. 16, a coherent light source 1, a condensing optical system 2 composed of a convex lens, and an optical sensor 5 are integrally mounted on a housing 21 of a sensor unit 20. The sensor unit 20, in which the coherent light source 1, the convex lens, and the like are arranged at predetermined positions, is small and can be easily mounted around the photoconductor 3. The condensing optical system 2 may be provided with a mask that blocks portions other than the portion through which the light emitted from the coherent light source 1 and the light reflected from the photoconductor 3 pass, if necessary.

FIGS. 17 and 18 show different modifications of another embodiment of the image measuring apparatus according to the fourth or sixth embodiment of the present invention. In this embodiment, an optical sensor for detecting regular reflection light and an optical sensor for detecting diffuse reflection light are arranged separately at different positions.

That is, in the image measuring apparatus shown in FIG. 17, the light arranged on the plane at the object-side infinity focal plane of the condensing optical system 2 of the above embodiment, that is, at the position of the focal length f of the condensing optical diameter 2 is used. A small mirror 3 at the position corresponding to the sensor 5
0 is arranged, and this mirror 30
The light in the area corresponding to the area A1 and the area A2 in (B) is reflected so as to be orthogonal to the side, and the light in the area corresponding to the area A1 and the area A2 is reflected by the light receiving units 31a and 31b of the first optical sensor 31. Is to be detected. Further, an optical sensor 32 for detecting light in a region corresponding to the region B and the region C in FIG. 2B is disposed behind the mirror 30 in the optical axis direction.

The image measuring device shown in FIG. 18 uses a so-called Schlieren optical system. This image measuring device is arranged on the optical axis of the light collecting optical system 2 so that the focal length of the light collecting optical system 2 can be adjusted. coherent light source 1 at a position slightly away from f
After the divergent light LB emitted from the coherent light source 1 passes through the helical beam splitter 41 and is deflected by the 波長 wavelength plate 42,
The light is substantially collimated by the condensing optical system 2. The photoreceptor 3 is arranged on the image side of the condensing optical system 2 at a substantially infinity focal position, and the specularly reflected light from the photoreceptor 3 re-enters the condensing optical system 2 as substantially parallel light, and The light is again deflected by the wave plate 42, is reflected by the helical beam splitter 41, and is guided to the first optical sensor 43. On the other hand, the toner 4
In the case where there is, the collimated light is diffused on the toner 4 surface, and the helical beam splitter 4
The light is guided to the second optical sensor 44 without passing through 1. Thus, all of the same effects as those of the above embodiment can be realized by the coaxial optical system, and miniaturization and efficiency can be achieved.

The other configuration and operation are the same as those of the above embodiment, and the description thereof will be omitted.

[0069]

As described above, according to the present invention,
It is possible to provide an image measuring method, an image measuring device, and a sensor unit capable of detecting not only the amount of toner of an image formed on an image carrier such as a photoconductor but also the state of image formation.

According to the present invention, there is provided an image measuring method, an image measuring apparatus, and a sensor unit capable of performing stable and accurate density measurement even when the relative position between the image carrier and the detecting member changes. can do.

Further, according to the present invention, image forming parameters such as charging potential, bias potential, exposure potential, developing tribo value, developing toner density, etc. are detected, and these detected image forming parameters are immediately fed back. As a result, it is possible to provide an image measuring method, an image measuring device, and a sensor unit capable of controlling a parameter for determining an image forming state.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of an image measuring device according to the present invention.

FIG. 2A is an explanatory diagram showing a light receiving state of an optical sensor, and FIG. 2B is a configuration diagram showing a light receiving section of the optical sensor.

FIG. 3 is a configuration diagram showing another modified example of the optical sensor.

FIG. 4A is an explanatory view showing an image to be measured on a photoconductor, FIG. 4B is a schematic view showing a light receiving state of an optical sensor, and FIG. 4C is light received by the optical sensor; It is a waveform diagram which shows light.

FIGS. 5A and 5B are explanatory diagrams showing measured images on a photoreceptor, respectively.

FIG. 6 is an explanatory diagram illustrating a light receiving state according to a position change of a photoconductor.

FIGS. 7A to 7D are graphs each showing an output of an optical sensor.

FIG. 8 is a graph showing an electrostatic latent image on a photoconductor.

FIG. 9 is a chart showing a result of analyzing a change in image forming conditions.

FIGS. 10A to 10D are graphs each showing an output of an optical sensor.

FIGS. 11A to 11D are graphs each showing an output of an optical sensor.

FIGS. 12A to 12D are graphs each showing an output of an optical sensor.

FIGS. 13A and 13B are waveform diagrams each showing a change in Fourier spectrum.

FIGS. 14A to 14D are graphs each showing an output of an optical sensor.

FIG. 15 is a flowchart illustrating an operation of analyzing a change in image forming conditions.

FIG. 16 is a block diagram showing another embodiment of the image measuring device according to the present invention.

FIG. 17 is a configuration diagram showing still another embodiment of the image measuring device according to the present invention.

FIG. 18 is a configuration diagram showing still another embodiment of the image measuring device according to the present invention.

FIG. 19 is a graph showing measurement results of a conventional toner concentration measuring device.

FIG. 20 is a graph showing measurement results of a conventional toner concentration measuring device.

[Explanation of symbols]

1 coherent light source, 2 focusing optics, 3 photoconductor,
4. Toner image, 5 light sensor.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03G 15/00 303 G01B 11/24 G06T 1/00

Claims (13)

(57) [Claims] 1. An area including a vicinity of an infinity focus position of the reflected light by irradiating parallel light to an image to be measured on an image carrier , making the reflected light incident on a condenser optical system, and reflecting the reflected light. From the measured values of the reflected light amount at multiple locations on the image carrier
Image measurement method is characterized in that so as to measure the state of formation of an image. 2. An image to be measured on an image carrier is irradiated with parallel light.
And the specular reflection light from the image carrier and the expansion from the image to be measured.
The diffusely reflected light is made incident on the condensing optical system, and the reflected light is collected.
Multiple points in the area including near the focal position at infinity by the optical optics
From the measured value of the light intensity distribution of the reflected light at
The feature is to measure the formation state of the measurement image
Image measurement method . 3. A process according to claim 1 or 2 SL, characterized in that from the state of formation of the measurement image on the measured image carrier so as to analyze the abnormality of the image forming means to form an image to be measured
Image measuring method of the placement. 4. A light quantity measurement value at least in the vicinity of a focal point at infinity of the condensing optical system is used as a light quantity detection value at a plurality of positions by the reflected light quantity detection unit.
The image measuring method according to claim 1 . 5. A parallel light source for irradiating parallel light to an image to be measured on an image carrier, and condensing optics for condensing reflected light from the image to be measured generated by irradiation of the parallel light by the parallel light source. System, a light amount detection unit that detects light amounts at a plurality of locations in an area including the vicinity of the infinity focus position of the light-collecting optical system, and an image bearing device based on detection values of reflected light amounts at the plurality of locations by the light quantity detection unit.
An image measuring apparatus, comprising: a measuring unit that measures a state of forming an image to be measured on a body . 6. The object to be measured on an image carrier , wherein the parallel light source is
6. The image measuring apparatus according to claim 5 , comprising: a light emitting source for generating light for irradiating an image; and a parallel optical system for collimating the light emitted from the light emitting source. 7. A light-emitting source for generating light for irradiating an image to be measured on an image carrier, and collimating the light emitted from the light-emitting source and reflecting from the image to be measured caused by the irradiation of the parallel light. A light-collecting optical system that collects light, a light-amount detecting unit that detects light amounts at a plurality of locations in an area including the vicinity of an infinity focal position of the light-collecting optical system, An image measuring apparatus comprising: a measuring unit that measures a state of forming an image to be measured on an image carrier from a detected value. 8. An image measuring apparatus according to claim 5 , wherein said light emitting source comprises a coherent light source. 9. The image forming apparatus according to claim 1, wherein the light amount detection unit includes a plurality of light receiving units capable of measuring a light amount distribution, and the measuring unit determines a light amount distribution at a plurality of locations by the light amount detection unit on the image carrier.
Claims, characterized in that measuring the formation state of the measured image
An image measuring device according to any one of claims 5 to 8 . 10. The light amount detecting section is composed of an integrated n-dimensional light receiving element (n> 1), and the measuring means determines a detection value corresponding to a light receiving position of the n-dimensional light receiving element at a corresponding light amount. The image measuring apparatus according to claim 5 , wherein a measurement state of an image to be measured on the image carrier is measured. 11. An image carrier measured by said measuring means.
From the state of formation of the measured image on the body, the measured
Image measuring apparatus according to any one of claims 5 to 10, characterized in that it comprises an analysis means for analyzing an abnormality of the image forming means to form an image. As 12. light amount detection value of the plurality of locations by the light amount detector, wherein, wherein the use of light intensity measurements at infinity focal position vicinity of at least the light converging optical system
The image measurement device according to claim 5 . 13. A light-emitting source for irradiating an image to be measured on an image carrier , collimating light emitted from the light-emitting source, and condensing reflected light from the image to be measured caused by the irradiation of the parallel light. A light-receiving element that is disposed near the infinity focus of the light-collecting optical system and detects reflected light from an image to be measured after passing through the optical system at a plurality of locations; A sensor unit in which a light source, a condensing optical system, and a light receiving element are integrally formed.