JP5761390B2 - Reflective optical sensor and image forming apparatus - Google Patents

Description

  The present invention relates to a reflective optical sensor and an image forming apparatus.

As an image forming apparatus that forms an image with toner, a copying machine, a printer, a plotter, a facsimile machine, a multifunction printer (MFP), and the like are widely known.
In such an image forming apparatus, generally, an electrostatic latent image is formed on the surface of a “photosensitive drum” that is a latent image carrier, and development is performed to visualize the electrostatic latent image with toner. I have an image.

  There are various development methods for obtaining a toner image, such as a two-component development method using a two-component developer containing toner and a carrier, and a mono-toner development method using a developer composed only of toner. Are known.

Regardless of the development method, in order to obtain a good toner image, the “toner amount to be used for developing the electrostatic latent image” must be appropriate. If a sufficient amount of toner is not supplied to the electrostatic latent image, the image (output image) output from the image forming apparatus becomes an “image with insufficient density”. On the other hand, if the amount of toner supplied to the electrostatic latent image is excessive, the density distribution in the output image is biased toward the “high density side”, resulting in an image that is difficult to see.
In order to check the suitability of the amount of toner used for developing an electrostatic latent image, a latent image carrier that forms an electrostatic latent image or a “toner image on a latent image carrier on a sheet-like recording medium such as transfer paper” It is widely practiced to form a toner density detection pattern (toner pattern) on the transfer belt to be transferred, irradiate the toner pattern with detection light, and determine the suitability of the toner density by changing the amount of reflected light. (Patent Documents 1 to 5 etc.).

The “toner density” is the “image density” of a toner pattern as a toner image.
The toner pattern is formed under “reference image forming conditions” based on image forming conditions such as the charging potential of the latent image carrier, exposure amount, and developing bias. The intensity of reflected light when irradiated with detection light is Since it changes corresponding to the toner density, it is possible to know the level of toner density under the standard image forming conditions by detecting the amount of reflected light.
A high (low) toner density means that the amount of toner supplied to the electrostatic latent image is large (small), so “control toner replenishment to the development unit” according to the detected toner density. It is possible to obtain an appropriate toner image by adjusting image forming conditions.

  The applicant has previously proposed a new “reflective optical sensor” that detects the toner density of a toner pattern (Patent Document 6).

This invention makes it a subject to implement | achieve the reflection type optical sensor which can perform a "higher precision" detection .

The “reflective optical sensor” of the present invention is a reflective optical sensor for detecting the toner density or position of the toner pattern on the support member, and N (≧ 3) light emitting elements arranged in a line in the first direction. An illumination system having a light receiving portion, a light receiving system having N light receiving portions arranged in one direction parallel to the first direction, and N irradiation microlenses in one direction parallel to the first direction. An illumination optical system, and a light receiving optical system having N light receiving microlenses in one direction parallel to the first direction, and an arrangement pitch of the N light emitting units of the illumination system, The arrangement pitch of the N microlenses of the illumination optical system, the arrangement pitch of the N light receiving portions of the light receiving system, and the arrangement pitch of the N microlenses of the light receiving optical system are the same, and the irradiation use micro lens and the light-receiving micro lens is the same Of formed of an optical material, a plano-convex shape the irradiation microlens having a convex surface facing the incident surface, the light receiving microlens is a plano-convex shape having a convex surface on the exit surface, the optical axes of the illumination microlens It is parallel to the corresponding light emitting unit vertical light emitting portion axis as the light emitting portion of the center, shifted by a predetermined distance to the light receiving system side with respect to the light emitting portion axis, the optical axis of each light-receiving microlens lens area of the corresponding center of the light receiving portion that is parallel to the vertical light receiving unit axis as the light receiving portion, with respect to the light receiving portion axis and shifted by a predetermined distance to the illumination system side, the light receiving microlens There larger than the lens area of the irradiation microlens, a lens surface curvature radius of the light-receiving microlenses is smaller than the lens surface curvature radius of the irradiation microlens, lens of the light receiving microlens Thickness is greater than the lens thickness of the illumination microlens.

As described above, the reflective optical sensor of the present invention “ detects the toner density or position of the toner pattern on the support member ” and has the above-described structural features.

Irradiating the detection light to the surface of the support member, by detecting the reflected light, for detecting the toner density or position of the toner pattern on the support member.

Reflective optical sensor of the invention includes an illumination system, and light receiving system, and irradiation microlens and a light receiving microlens.

"Illumination system" will have N (≧ 3) pieces of light emitting unit emits the detection light from the respective light emitting portions. An LED can be preferably used as the light emitting unit, and therefore an “LED array” can be preferably used as the illumination system.

"Light-receiving system" will have an N-number of the light-receiving part. A “photodiode or phototransistor” can be preferably used as the light receiving portion, and therefore a “photodiode array or phototransistor array” can be preferably used as the light receiving system.

N “light receiving microlenses” are arranged in a direction parallel to the N light receiving portions.

Array direction of the light emitting portion of the illumination system (the first direction), the array direction of the light receiving portion of the light-receiving system, the arrangement direction of the irradiation microlens array direction of the light-receiving microlens parallel to each other, in the direction of movement of the support member Makes an orthogonal or predetermined angle with respect to it. Hereinafter, the “support member” is also simply referred to as “moving member”. In addition, the direction in which the support member moves may be referred to as a “sub-direction”.

The illumination system, such that the light beam emitted from the light emitting unit is irradiated as detection light to the moving member through the irradiation microlens, and the reflected light from the moving member is incident on the light receiving unit through the light receiving microlens. The positional relationship among the light receiving system, the irradiation microlens, and the light receiving microlens is determined.

The irradiation microlens and the light receiving microlens are formed of the same optical material, and both the irradiation microlens and the light receiving microlens have a “plano-convex shape”.
The arrangement pitch of the light emitting part / light receiving part, irradiation microlens / light receiving microlens is preferably in the range of about 0.1 mm to 1.0 mm.

The optical axes of the illumination microlens passes through the center of the corresponding light emitting portion, parallel to the vertical light emitting portion axis to the light emitting portion (surface), shifted with respect to the light emitting portion axis to the "receiving system side" Has been.
The optical axis of each light-receiving microlens passes through the center of the corresponding light-receiving unit, is parallel to the light-receiving unit axis perpendicular to (the surface of) the light-receiving unit, and to the illumination system with respect to the light-receiving unit axis It has been shifted to the “coming or moving side”.

The irradiation microlens and the light receiving microlens are made of the same optical material.
Both the irradiation microlens and the light receiving microlens have a plano-convex shape.
The convex lens surface in the “plano-convex shape” is an incident-side surface in the irradiation microlens, and an exit-side surface in the light-receiving microlens.
The lens area, lens surface radius of curvature, and lens thickness are all different between the irradiation microlens and the light receiving microlens.
The “lens area” is larger for the light receiving microlens than for the irradiation microlens.

The radius of curvature of the “convex lens surface” is smaller in the irradiation microlens than in the light receiving microlens.
The “lens thickness” is larger for the light-receiving microlens than for the irradiation microlens.
The optical axis of each irradiation microlens is parallel to the light emitting unit axis that passes through the center of the corresponding light emitting unit and is perpendicular to the light emitting unit, and is shifted to the light receiving system side with respect to the light emitting unit axis.
The above configuration is the basic configuration of the reflective optical sensor.

The reflective optical sensor according to claim 1 is characterized in that, in the “basic configuration”, the optical axis of each light receiving microlens is shifted to the “ illumination system side ” with respect to the light receiving unit axis.

Reflective optical sensor according to claim 2, characterized in that the Oite to the "basic structure", the optical axis of each light-receiving micro lenses are shifted to the "side away from the illumination system" to the light receiving portion axis And

The reflective optical sensor according to claim 1 or 2 , wherein at least one of the irradiation microlens array and the light receiving microlens array has a light shielding film formed in a predetermined region of at least one of the front side and the back side. ( Claim 3 ).

In the reflective optical sensor according to any one of claims 1 to 3, it is preferable that the irradiation microlens and the light receiving microlens are “integrally formed” (claim 4).
In this case, the i (1 ≦ i ≦ N) -th irradiation microlens from the predetermined side in the irradiation optical system and the i (1 ≦ i ≦ N) -th light reception from the predetermined side in the light-receiving optical system . The microlens forms an “oval or rectangular compound lens surface in contact with each other in the sub-direction”, and this compound lens surface is “same pitch as the arrangement pitch of the light emitting portions” in the width direction of the compound lens surface. The structure can be in contact with each other (claim 5).
In this case, the “oval or rectangular” longitudinal direction of the compound lens surface is the arrangement direction of the irradiation microlenses and the corresponding light-receiving microlenses, that is, the “sub-direction”.

The reflection type optical sensor according to any one of claims 1 to 5 includes a first reference received light amount that is “the received light amount of each light receiving portion when the surface of the support member is irradiated with detection light”, and “the support member With reference to the second reference light reception amount, which is the light reception amount of each light receiving portion when the upper toner pattern is irradiated with the detection light, the second reference light reception amount is set to “the amount of light received by diffuse reflected light and the positive light reception amount. “Processing means” that separates into “the amount of light received by reflected light” can also be provided.

Then, in the “processing means”, an operation is performed to obtain a value: D (expanded) / D (positive) obtained by dividing the received light amount by diffuse reflected light: D (expanded) by the received light amount by regular reflected light: D (positive). You can also

The reflective optical sensor according to any one of claims 1 to 5 , wherein the N light emitting units are divided into m sets in the arrangement direction, and each set has a substantially equal number of light emitting units. It is possible to have an “irradiation control device” that causes the light emitting units to blink in synchronization with each other in the order of arrangement ( claim 6 ).

The reflection type optical sensor according to any one of claims 1 to 6 , wherein the number N of the light emitting unit, the light receiving unit, the irradiation microlens, and the light receiving microlens is N,
7 ≦ N ≦ 31
It is preferable that the number is an odd number within the range ( Claim 7 ).
The reason why the value of N is “odd” is that the number of arrays: N has “center”, and the light-emitting portion occupying this center position can correspond to the “center in the main direction” of the toner pattern. is there.

The image forming apparatus according to the present invention includes a latent image carrier, an electrostatic latent image forming unit, a developing device, and a transfer device. The electrostatic latent image forming unit includes a charging unit and an optical scanning device. It has a reflection type optical sensor given in any 1 paragraph of the above-mentioned claims 1-7 ( claim 8 ).

  The “latent image carrier” is a photoconductive photosensitive member formed in a drum shape or a belt shape.

  The “electrostatic latent image forming means” forms an electrostatic latent image by charging and exposing the latent image carrier.

The “developing device” develops the electrostatic latent image and visualizes it as a toner image.
The “transfer device” transfers the toner image to a sheet-like recording medium using a transfer belt. The transfer belt can be the direct transfer belt described above or an intermediate transfer belt.

The “electrostatic latent image forming means” includes a “charging means” for uniformly charging the peripheral surface of the latent image carrier, and charging and optical scanning of the latent image carrier to produce an electrostatic latent image corresponding to the image information. And an “optical scanning device” to be formed.
The “reflective optical sensor” is used to detect “toner density or position” of a toner pattern formed by using a latent image carrier or a transfer belt as a moving member , or “toner density and position” of the toner pattern. .

The image forming apparatus according to claim 8 forms toner images of different colors on a plurality of latent image carriers, and superimposes the plurality of toner images to form a multicolor image (“two-color image” or “full-color image”). including.) may be a tandem type image forming apparatus for forming a (claim 9).

As described above, according to the present invention, a novel reflective optical senner and image forming apparatus can be realized. In the reflective optical sensor of the present invention, the positional relationship among the illumination system, the light receiving system, the irradiation microlens, and the light receiving microlens is optimized as described above, and the optical characteristics of the irradiation microlens and the light receiving microlens are as follows. By optimizing the above, it is possible to effectively increase the amount of light received by the light receiving unit and perform “more accurate detection”.

  Therefore, the image forming apparatus using the reflective optical sensor of the present invention can perform toner image density control and color toner image overlay accuracy with higher performance, and can realize good image formation.

1 is a diagram for explaining a color printer as an image forming apparatus. FIG. It is a figure for demonstrating an optical scanning device. It is a figure for demonstrating an optical scanning device. It is a figure for demonstrating an optical scanning device. It is a figure for demonstrating an optical scanning device. It is a figure for demonstrating the toner pattern detection by a reflection type optical sensor. It is a figure for demonstrating the toner pattern detection by a reflection type optical sensor. FIG. 6 is a diagram for explaining a toner pattern for position detection. It is a diagram for explaining a toner pattern for density detection. It is a figure for demonstrating the toner pattern detection by a reflection type optical sensor. It is a figure for demonstrating the toner pattern detection by a reflection type optical sensor. It is a figure for demonstrating the toner pattern detection by a reflection type optical sensor. 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  Hereinafter, embodiments will be described.

  FIG. 1 shows a schematic configuration of a color printer as an embodiment of an image forming apparatus.

  The color printer 2000 is a “tandem multicolor printer” that forms a full color image by superimposing toner images of four colors (black, cyan, magenta, and yellow).

  The color printer 2000 includes an optical scanning device 2010, four photosensitive drums 2030a, 2030b, 2030c, 2030d, four cleaning units 2031a, 2031b, 2031c, 2031d, four charging devices 2032a, 2032b, 2032c, 2032d, and four developing units. Rollers 2033a, 2033b, 2033c, 2033d, four toner cartridges 2034a, 2034b, 2034c, 2034d, transfer belt 2040, transfer roller 2042, fixing roller 2050, paper feed roller 2054, registration roller pair 2056, paper discharge roller 2058, paper feed A tray 2060, a paper discharge tray 2070, a communication control device 2080, a reflective optical sensor 2245, and a printer control device 2090 that comprehensively controls the above-described units are provided.

  In the following, as shown in FIG. 1, an “XYZ three-dimensional orthogonal coordinate system” is assumed, and the direction along the longitudinal direction of each photosensitive drum is defined as the Y-axis direction (direction orthogonal to the drawing of FIG. 1). The direction along the arrangement direction of the photosensitive drums will be described as the X-axis direction.

  The communication control device 2080 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  In each of the photosensitive drums 2030a to 2030d that are “latent image carriers”, the surface formed as the photosensitive layer is a “scanned surface” of optical scanning by the optical scanning device 2010. The photosensitive drums 2030a to 2030d are rotated in the direction of the arrow (clockwise) in the plane of FIG. 1 by a rotation mechanism (not shown).

  A charging device 2032a, a developing roller 2033a, and a cleaning unit 2031a are arranged along the rotation direction of the photosensitive drum 2030a so as to surround the photosensitive drum 2030a.

  The photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, the toner cartridge 2034a, and the cleaning unit 2031a constitute an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image.

  The charging device 2032b, the developing roller 2033b, and the cleaning unit 2031b, which are arranged so as to surround the photosensitive drum 2030b along the rotation direction of the photosensitive drum 2030b, are an image forming station (hereinafter, for convenience, for forming a cyan image). (Also referred to as “C station”).

  The charging device 2032c, the developing roller 2033c, and the cleaning unit 2031c, which are arranged so as to surround the photosensitive drum 2030c along the rotation direction of the photosensitive drum 2030c, are an image forming station that forms a magenta image (hereinafter, for convenience sake). (Also referred to as “M station”).

  The charging device 2032d, the developing roller 2033d, and the cleaning unit 2031d, which are arranged so as to surround the photosensitive drum 2030d along the rotation direction of the photosensitive drum 2030d, are an image forming station (hereinafter, for convenience, for forming a yellow image). (Also referred to as “Y station”).

  The charging device 2032a and the like constitute “charging means” and, together with the optical scanning device 2010, constitute “electrostatic latent image forming means”.

  The charging devices 2032a to 2032d uniformly charge the surfaces of the corresponding photosensitive drums 2030a to 2030d, respectively.

The optical scanning device 2010 responds by the light flux modulated for each color image information based on the multi-color image information (black image information, cyan image information, magenta image information, yellow image information) from the “higher level device”. The surface of the photosensitive drum to be scanned is optically scanned in the Y direction.
As a result, the potential is attenuated at the light-irradiated portion on the surface of each photosensitive drum, and an electrostatic latent image corresponding to the image information is formed. The formed electrostatic latent image moves to the corresponding developing roller side as the photosensitive drum rotates.
The configuration of the optical scanning device 2010 will be described later.

The toner cartridge 2034a stores black toner, and the black toner is supplied to the developing roller 2033a. The toner cartridge 2034b stores cyan toner, and the cyan toner is supplied to the developing roller 2033b.
The toner cartridge 2034c stores magenta toner, and the magenta toner is supplied to the developing roller 2033c. Yellow toner is stored in the toner cartridge 2034d, and the yellow toner is supplied to the developing roller 2033d.

Each of the developing rollers 2033a to 2033d rotates, and each color toner from the corresponding toner cartridge is thinly and uniformly applied to the surface thereof.
When the applied toner on the surface of each developing roller comes into contact with the surface of the corresponding photosensitive drum, it adheres to the “potential attenuated portion” of the surface and visualizes the electrostatic latent image as a toner image.
The “toner images having different colors” formed for each photoconductor drum move as the photoconductor drum rotates.

The transfer belt 2040 is an “intermediate transfer belt”, and yellow, magenta, cyan, and black toner images are sequentially transferred from the photosensitive drums 2030a to 2030d onto the transfer belt 2040 at a predetermined timing, and are superimposed on each other to form a color. Form an image.
In this embodiment, the transfer belt 2040 that is an intermediate transfer belt is a “support member on which a toner pattern is formed”, and the direction in which the toner image moves on the transfer belt 2040 is the “sub-direction”. A direction (Y-axis direction) orthogonal to the direction is called a “main direction”.

The recording sheets as “sheet-like recording medium” stored in the sheet feeding tray 2060 are fed one by one from the sheet feeding tray 2060 by the sheet feeding roller 2054 and conveyed toward the registration roller pair 2056.
The registration roller pair 2056 pinches the recording paper fed from the paper feed tray 2060 and feeds it toward “between the transfer belt 2040 and the transfer roller 2042” at a predetermined timing. The transfer roller 2042 transfers a color image to the recording paper surface.
The recording sheet on which the color image is transferred is fixed with the color image by heat and pressure applied from the fixing roller 2050. The recording paper on which the color image has been fixed is discharged onto a discharge tray 2070 via a discharge roller 2058 and sequentially stacked.

  When the “transfer residual toner” on the surfaces of the photosensitive drums 2030a to 2030d is removed by the cleaning units 2031a to 2031d corresponding to the photosensitive drums, the surfaces of the photosensitive drums are again transferred to the corresponding charging devices. Return to the opposite position.

  An optical sensor device 2245 using a reflective optical sensor is arranged on the “−X” side (left side in FIG. 1) of the transfer belt 2040. The optical sensor device 2245 will be described later.

  Next, the configuration of the optical scanning device 2010 will be described.

As shown in FIGS. 2 to 5, the optical scanning device 2010 as one embodiment of the optical scanning device includes four light sources 2200a, 2200b, 2200c, 2200d, four coupling lenses 2201a, 2201b, 2201c, 2201d, 4 aperture plates 2202a, 2202b, 2202c, 2202d, 4 cylindrical lenses 2204a, 2204b, 2204c, 2204d, polygon mirror 2104, 4 fθ lenses 2105a, 2105b, 2105c, 2105d, 8 folding mirrors 2106a, 2106b, 2106c, 2106d, 2108a, 2108b, 2108c, 2108d, 4 toroidal lenses 2107a, 2107b, 2107c, 2107d, 4 light detection sensors 2205a, 2205b, 2205c 2205d, 4 one light detection mirror 2207A, and includes 2207b, 2207c, 2207d, etc. (not shown) scanning control unit.
As shown in FIG. 5, these are assembled at predetermined positions of an optical housing 2300 (not shown in FIGS. 2 to 4).

  Hereinafter, for convenience, a direction corresponding to the main scanning direction of the optical scanning is referred to as a “main scanning corresponding direction”, and a direction corresponding to the sub scanning direction is referred to as a “sub scanning corresponding direction”.

  The direction along the optical axis of the coupling lens 2201a and the coupling lens 2201b is referred to as “w1 direction”, and the main scanning corresponding direction on the optical path from the light source 2200a and the light source 2200b to the polygon mirror 2104 is referred to as “m1 direction”.

  The direction along the optical axis of the coupling lens 2201c and the coupling lens 2201d is “w2 direction”, and the main scanning corresponding direction on the optical path from the light source 2200c and the light source 2200d to the polygon mirror 2104 is “m2 direction”. The sub-scanning corresponding direction on the optical path from the light source 2200a and the light source 2200b to the polygon mirror 2104 and the sub-scanning corresponding direction on the optical path from the light source 2200c and the light source 2200d to the polygon mirror 2104 are both the same as the Z-axis direction. Direction.

  The light source 2200b and the light source 2200c are disposed at positions separated from each other in the X-axis direction, and the light source 2200a is disposed on the “−Z” side of the light source 2200b (see FIG. 3). The light source 2200d is disposed on the “−Z” side of the light source 2200c (see FIG. 4).

  The coupling lens 2201a is disposed on the optical path of the light beam emitted from the light source 2200a, and makes the light beam a substantially parallel light beam. The coupling lens 2201b is disposed on the optical path of the light beam emitted from the light source 2200b, and makes the light beam a substantially parallel light beam.

  The coupling lens 2201c is disposed on the optical path of the light beam emitted from the light source 2200c, and makes the light beam a substantially parallel light beam. The coupling lens 2201d is disposed on the optical path of the light beam emitted from the light source 2200d, and makes the light beam a substantially parallel light beam.

  The aperture plate 2202a has an aperture and shapes the light beam that has passed through the coupling lens 2201a. The aperture plate 2202b has an aperture and shapes the light beam that has passed through the coupling lens 2201b.

  The aperture plate 2202c has an aperture and shapes the light beam that has passed through the coupling lens 2201c. The aperture plate 2202d has an aperture and shapes the light beam that has passed through the coupling lens 2201d.

  The cylindrical lens 2204 a forms an image of the light beam that has passed through the opening of the aperture plate 2202 a in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the “sub-scanning corresponding direction”. The cylindrical lens 2204 b forms an image of the light beam that has passed through the opening of the aperture plate 2202 b in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the “sub-scanning corresponding direction”.

  The cylindrical lens 2204 c forms an image of the light beam that has passed through the opening of the aperture plate 2202 c in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the “sub-scanning corresponding direction”. The cylindrical lens 2204d forms an image of the light beam that has passed through the opening of the aperture plate 2202d in the vicinity of the deflection reflection surface of the polygon mirror 2104 in the “sub-scanning corresponding direction”.

  The polygon mirror 2104 has a four-stage mirror having four deflecting reflecting surfaces as a two-stage structure, and the first-stage (lower) four-face mirror deflects the light beam from the cylindrical lens 2204a and the light beam from the cylindrical lens 2204d, respectively. The second stage (upper stage) four-sided mirror is arranged so as to deflect the light beam from the cylindrical lens 2204b and the light beam from the cylindrical lens 2204c, respectively. Note that the first-stage tetrahedral mirror and the second-stage tetrahedral mirror rotate with a phase shift of 45 °, and writing scanning is alternately performed in the first and second stages.

  The light beams from the cylindrical lenses 2204 a and 2204 b are deflected on the “−X” side of the polygon mirror 2104, and the light beams from the cylindrical lenses 2204 c and 2204 d are deflected on the “+ X” side of the polygon mirror 2104.

  Each of the fθ lenses 2105a to 2105d has optical characteristics such that the light spot moves at a constant speed in the main scanning direction on the surface (scanned surface) of the corresponding photosensitive drum 2030a to 2030d as the polygon mirror 2104 rotates. It has a non-circular arc surface shape.

  The fθ lenses 2105 a and 2105 b are arranged on the “−X” side of the polygon mirror 2104, and the fθ lenses 2105 c and 2105 d are arranged on the “+ X” side of the polygon mirror 2104.

  As shown in FIG. 5, the fθ lens 2105a and the fθ lens 2105b are stacked in the Z-axis direction, the fθ lens 2105a is opposed to the first-stage four-sided mirror, and the fθ lens 2105b is opposed to the second-stage four-sided mirror. doing. The fθ lens 2105c and the fθ lens 2105d are also laminated in the Z-axis direction. The fθ lens 2105c is opposed to the second-stage tetrahedral mirror, and the fθ lens 2105d is opposed to the first-stage tetrahedral mirror.

The light beam from the cylindrical lens 2204a deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030a through the fθ lens 2105a, the folding mirror 2106a, the toroidal lens 2107a, and the folding mirror 2108a, thereby forming a light spot. The light spot moves in the longitudinal direction (Y direction) of the photosensitive drum 2030a as the polygon mirror 2104 rotates, and optically scans the photosensitive drum 2030a.
The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030a, and the rotational direction of the photosensitive drum 2030a is the “sub-scanning direction” on the photosensitive drum 2030a.

The light beam from the cylindrical lens 2204b deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030b through the fθ lens 2105b, the folding mirror 2106b, the toroidal lens 2107b, and the folding mirror 2108b, thereby forming a light spot. The light spot moves in the longitudinal direction of the photosensitive drum 2030b as the polygon mirror 2104 rotates, and optically scans the photosensitive drum 2030b.
The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030b, and the rotational direction of the photosensitive drum 2030b is the “sub-scanning direction” on the photosensitive drum 2030b.

The light beam from the cylindrical lens 2204c deflected by the polygon mirror 2104 is irradiated to the photosensitive drum 2030c through the fθ lens 2105c, the folding mirror 2106c, the toroidal lens 2107c, and the folding mirror 2108c, thereby forming a light spot. The light spot moves in the longitudinal direction of the photosensitive drum 2030c as the polygon mirror 2104 rotates, and optically scans the photosensitive drum 2030c.
The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030c, and the rotational direction of the photosensitive drum 2030c is the “sub-scanning direction” on the photosensitive drum 2030c.

The light beam from the cylindrical lens 2204d deflected by the polygon mirror 2104 is irradiated onto the photosensitive drum 2030d through the fθ lens 2105d, the folding mirror 2106d, the toroidal lens 2107d, and the folding mirror 2108d, thereby forming a light spot. . The light spot moves in the longitudinal direction of the photosensitive drum 2030d as the polygon mirror 2104 rotates, and optically scans the photosensitive drum 2030d.
The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030d, and the rotational direction of the photosensitive drum 2030d is the “sub-scanning direction” on the photosensitive drum 2030d.

  A scanning area in the main scanning direction in which image information is written on each photosensitive drum is called an “effective scanning area” or an “image forming area”, but is also called an “effective image area” in this specification.

  The folding mirrors are arranged so that the optical path lengths from the polygon mirror 2104 to the photosensitive drums coincide with each other, and the incident position and the incident angle of the light flux on the photosensitive drum are “equal to each other”. ing.

  Further, the “fθ lens and the corresponding toroidal lens” constitute a surface tilt correction optical system in which the deflection point of the polygon mirror and the surface of the photosensitive drum corresponding thereto are “conjugated to the sub-scanning corresponding direction”. .

An optical system disposed on the optical path between the polygon mirror 2104 and each photosensitive drum is also referred to as a “scanning optical system”.
In the embodiment being described, the “scanning optical system of the K station” is formed by the fθ lens 2105a, the toroidal lens 2107a, and the folding mirrors (2106a, 2108a), and the fθ lens 2105b, the toroidal lens 2107b, and the folding mirrors (2106b, 2108b). The “C-station scanning optical system” is configured as described above.
Similarly, the “M station scanning optical system” is formed by the fθ lens 2105c, the toroidal lens 2107c, and the folding mirror (2106c, 2108c), and the “Y station” is formed by the fθ lens 2105d, the toroidal lens 2107d, and the folding mirror (2106d, 2108d). The scanning optical system "is configured.

  Of the light beam deflected by the polygon mirror 2104 and passed through the scanning optical system of the K station, “a part of the light beam before starting writing” enters the light detection sensor 2205a via the light detection mirror 2207a.

  Of the light beam deflected by the polygon mirror 2104 and passed through the scanning optical system of the C station, “a part of the light beam before starting writing” enters the light detection sensor 2205b via the light detection mirror 2207b.

  Of the light beam deflected by the polygon mirror 2104 and passed through the scanning optical system of the M station, “a part of the light beam before starting writing” enters the light detection sensor 2205c via the light detection mirror 2207c.

  Of the light beam deflected by the polygon mirror 2104 and passed through the scanning optical system of the Y station, “a part of the light beam before starting writing” enters the light detection sensor 2205d via the light detection mirror 2207d.

  The light detection sensors 2205a to 2205d output signals (photoelectric conversion signals) corresponding to the amount of received light.

  A “scan control device” (not shown) determines the scanning start timing of the corresponding photosensitive drum based on the output signal of each light detection sensor, and starts image writing by optical scanning at the determined timing.

  Next, the optical sensor device 2245 will be described.

  As shown in FIG. 6 as an example, the optical sensor device 2245 has four reflective optical sensors 2245a, 2245b, 2245c, and 2245d arranged in the Y direction.

The reflective optical sensor 2245a is disposed at a position facing the “vicinity of the + Y side end” of the transfer belt 2040, and the reflective optical sensor 2245d is disposed at a position of the transfer belt 2040 facing the “near the −Y side end”. Has been.
The reflective optical sensor 2245b is disposed on the “−Y side” of the reflective optical sensor 2245a, and the reflective optical sensor 2245c is disposed on the “+ Y side” of the reflective optical sensor 2245d.

  The four reflective optical sensors 2245a to 2245d are arranged so as to be “substantially equidistant” in the Y-axis direction.

As shown in FIG. 7, the center positions of the reflective optical sensors 2245a, 2245b, 2245c, and 2245d in the Y-axis direction are Y1, Y2, Y3, and Y4, respectively.
The toner patterns facing the reflective optical sensor 2245a in the X direction are toner patterns PP1 and TP1, and the toner patterns facing the reflective optical sensor 2245b are toner patterns PP2 and TP2.

  Similarly, the toner patterns facing the reflective optical sensor 2245c are toner patterns PP3 and TP3, and the toner patterns facing the reflective optical sensor 2245d are toner patterns PP4 and TP4.

  The toner patterns PP1, PP2, PP3, and PP4 are “position detection patterns”, and the toner patterns TP1, TP2, TP3, and TP4 are “density detection patterns”.

Since the position detection patterns PP1, PP2, PP3, and PP4 have the “same configuration”, in the following, the position detection patterns PP1 to PP4 are collectively referred to as “position” when it is not necessary to distinguish the position detection patterns from each other. It is also referred to as “detection pattern PP”.
As shown in FIG. 8, the position detection pattern PP includes four line patterns (LPY1, LPM1, LPC1, LPK1) parallel to the main direction (Y direction) and four lines inclined with respect to the main direction. Line pattern (LPY2, LPM2, LPC2, LPK2).

  The line patterns LPY1 and LPY2 are paired and formed with yellow toner, and the line patterns LPM1 and LPM2 are paired and formed with magenta toner. The line patterns LPC1 and LPC2 are paired and formed with cyan toner, and the line patterns LPK1 and LPK2 are paired and formed with black toner.

  The formation conditions are set so that “two line patterns forming a pair” form a predetermined interval with respect to the traveling direction (sub-direction) of the transfer belt 2040.

The density detection patterns TP1, TP2, TP3, and TP4 shown in FIG. 7 are formed of yellow toner, magenta toner, cyan toner, and black toner, respectively.
Hereinafter, when there is no need to distinguish between the density detection patterns, the density detection patterns TP1, TP2, TP3, and TP4 are collectively referred to as “density detection patterns TP”.

As shown in FIG. 9 as an example, the density detection pattern TP includes five rectangular patterns p1 to p5 (hereinafter referred to as “rectangular patterns”), and the five rectangular patterns p1 to p5 include the transfer belt 2040. Are arranged in a row in the traveling direction (sub-direction), and the gradations of the toner density are different.
In the example of FIG. 9, the toner density increases in the order of the rectangular patterns p1, p2, p3, p4, and p5. That is, the rectangular pattern p1 has the lowest toner density, and the rectangular pattern p5 has the highest toner density.

  The length of each rectangular pattern in the Y-axis direction is Lp, and the length of the transfer belt 2040 in the traveling direction is Wp. In the example in the description, “Lp = 1.0 mm”.

  The gradation of the toner density can be adjusted by adjusting the power of the light beam emitted from the light source of the optical scanning device, the duty ratio in the driving pulse supplied to the light source, the developing bias, etc. It can be changed by controlling the toner adhesion amount, or by changing the “halftone dot area ratio” when the rectangular pattern is composed of halftone dots.

  Hereinafter, when there is no need to distinguish between the position detection pattern and the density detection pattern, these are collectively referred to as a “toner pattern”.

  When “position detection processing and toner density detection processing” of a toner pattern is performed using a reflective optical sensor, the printer control device 2090 instructs the scanning control device to form a position detection pattern and a density detection pattern. Is done.

  In other words, the scanning control device controls the formation of the toner patterns by controlling the Y station to the K station.

  As shown in FIG. 10, the Y station is controlled by forming line patterns LPY1 and LPY2 at positions Y1, Y2, Y3 and Y4 on the photosensitive drum 2030d, and forming a density detection pattern TP1 at position Y1. It is done as follows.

  As shown in FIG. 11, in the control of the M station, line patterns LPM1 and LPM2 are formed at positions Y1, Y2, Y3, and Y4 on the photosensitive drum 2030c, and a density detection pattern TP2 is formed at the position Y2. It is done as follows.

  As shown in FIG. 12, the control of the C station is such that line patterns LPC1 and LPC2 are formed at positions Y1, Y2, Y3 and Y4 on the photosensitive drum 2030b, and a density detection pattern TP3 is formed at position Y3. It is done as follows.

  As shown in FIG. 13, in the control of the K station, line patterns LPK1 and LPK2 are formed at positions Y1, Y2, Y3 and Y4 on the photosensitive drum 2030a, and a density detection pattern TP4 is formed at the position Y4. To be done.

  The toner pattern formed in the shape of each photosensitive drum in this way is transferred to the transfer belt 2040 at a predetermined timing. In this manner, the position detection pattern PP and the density detection pattern TP are formed at positions Y1, Y2, Y3, and Y4 in the Y direction on the transfer belt 2040, respectively. This state is shown in FIG.

The four reflective optical sensors 2245a, 2245b, 2245c, and 2245d constituting the optical sensor device 2245 have the same configuration and structure, and the configuration and structure will be described below with the reflective optical sensor 2245a as a representative. .
As an example, as shown in FIG. 15, the reflective optical sensor 2245a includes nine light emitting portions E1 to E9, nine irradiation microlenses LE1 to LE9, nine light receiving portions D1 to D9, and nine light receiving portions. Microlenses LD1 to LD9 and a “processing device” (not shown).

The number of light emitting units / light receiving units is preferably “an odd number of about 7 to 31” as described in claim 7, but “9 combinations of 9 light emitting units / light receiving units” shown in FIG. "Is one of the preferred ones.

The microlenses LE1 to LE9 are “irradiation microlenses”, and the microlenses LD1 to LD9 are “light receiving microlenses” .
In the following, the arranged microlenses LE1 to LE9 are also referred to as “irradiation microlens array”, and the arranged microlenses LD1 to LD9 are also referred to as “light receiving microlens array”.

15A shows a state in which the reflective optical sensor is viewed from the main direction, and FIG. 15B shows a state in which the reflective optical sensor is viewed from the direction orthogonal to the arrangement direction of the light emitting unit and the light receiving unit.
FIG. 15C shows a state in which the detection light beams S1 to S9 emitted from the light emitting units E1 to E9 and irradiated through the irradiation microlenses LE1 to LE9 irradiate the transfer belt 2040. d) shows how the detection light beams S1 to S9 reflected by the transfer belt 2040 are received by the light receiving portions D1 to D9 via the light receiving microlenses LD1 to LD9.
FIG. 15E shows a state in which the detection lights S1 to S9 from the light emitting units E1 to E9 irradiate the toner pattern, and FIG. 15F shows the detection light S1 reflected by the toner pattern. -S9 respectively show the manner in which light is received by the light receiving parts D1-D9.

The nine light emitting portions E1 to E9 are arranged at equal intervals in one row in the Y direction (main direction). An LED can be used as each light emitting unit. The arrangement pitch (interval between adjacent light emitting portions) Le of the light emitting portions E1 to E9 can be set to 0.4 mm, for example.
The irradiation microlenses LE1 to LE9 correspond to the light emitting portions E1 to E9 on a one-to-one basis. As shown in FIG. 15A, each irradiation lens is shifted to the light receiving portion side from the corresponding light emitting portion. The light flux that is arranged and emitted from the light emitting portion is focused toward the surface of the transfer belt 2040.
In the following description, the light beams emitted from the light emitting units E1 to E9 and collected by the irradiation microlenses LE1 to LE9 are only irradiation microlenses corresponding to the respective light emitting units, as shown in FIG. And the transfer belt 2040 is irradiated as the detection light beams S1 to S9.

The surface of the transfer belt 2040 is smooth, and most of the light irradiated on the surface of the transfer belt 2040 is regularly reflected. As shown in FIG. 15D, the light receiving parts D1 to D9, when the detection light from the light emitting parts E1 to E9 irradiates “parts other than the toner pattern”, the light receiving parts D1 to D9 are light emitting parts E1. Only the specularly reflected light of the detection lights S1 to S9 from .about.E9 is received.
Each of the light receiving parts D1 to D9 individually corresponds to the light emitting parts E1 to E9.
As shown in FIG. 15A, each light receiving portion is arranged on the optical path of “light beam emitted from the corresponding light emitting portion and regularly reflected on the surface of the transfer belt 2040”. That is, the arrangement pitch of the nine light receiving portions D1 to D9 is equal to the arrangement pitch of the nine light emitting portions E1 to E9.

The irradiation microlens array and the light receiving microlens array are integrated, and the integration improves the “operability in assembling these microlens arrays to the reflective optical sensor”. Moreover, the integration accuracy between the microlens arrays is increased by integration.
The lens surface of each microlens can be formed on a glass substrate or a resin substrate using a known processing method such as photolithography or nanoimprint.

As described above, if the arrangement pitch of the light emitting sections in the sub-direction is 0.4 mm, the center interval between adjacent beam spots is also 0.4 mm, and the light spots formed on the surface of the transfer belt 2040 by each detection light are as follows. The size is about 0.4 mm in diameter.
The light spot by the conventional detection light is usually “about 2 to 3 mm in diameter”.

  As each irradiation microlens and each light receiving microlens, a spherical lens having a condensing function in the main direction and the sub direction, an anamorphic lens having different powers in the main direction and the sub direction, and the like can be used.

A PD (photodiode) can be suitably used for each light receiving unit, and each light receiving unit outputs a signal corresponding to the amount of received light.
When it is not necessary to individually specify the light emitting units E1 to E9, an arbitrary light emitting unit is displayed as the light emitting unit Ei, and the irradiation microlens corresponding to the light emitting unit Ei is selected from the irradiation microlens LEi and the light emitting unit Ei. The detection light that has exited and passed through the illumination condenser lens LEi is displayed as detection light Si.

  The light receiving unit corresponding to the light emitting unit Ei is displayed as the light receiving unit Di, and the light receiving microlens corresponding to the light receiving unit Di is displayed as the light receiving microlens LDi.

The nine irradiation microlenses LEi (i = 1 to 9) constituting the irradiation microlens array used in the reflective optical sensor shown in FIG. 15 have a lens diameter, a lens surface curvature radius, and a lens thickness. Takes the “same value”.
Similarly, the nine light receiving microlenses LDi (i = 1 to 9) constituting the light receiving microlens array all have the same value in terms of lens diameter, lens surface curvature radius, and lens thickness.

  However, the irradiation microlens LEi and the light receiving microlens LDi have different optical characteristics.

  As shown in FIG. 15A, the irradiation microlens LEi and the light receiving microlens LDi are “convex flat lenses” in which the surface on the side of the transfer belt, which is a support member, is a flat surface and the opposite surface is a convex surface. .

As a specific example, the irradiation microlens LEi has a lens diameter: 0.415 mm, a convex lens surface radius of curvature: 0.430 mm, and a lens thickness: 1.229 mm. The light receiving microlens LDi has a lens diameter: 0.712 mm, a lens surface radius of curvature: 0.380 mm, and a lens thickness: 1.419 mm.
The arrangement pitch (distance between the optical axes) of the irradiation microlenses LEi is 0.4 mm, and the arrangement pitch (distance between the optical axes) of the light-receiving microlenses LDi is also 0.4 mm.

  The optical axis of the irradiating microlens LEi passes through the center of the corresponding light emitting unit Ei (in order to guide the reflected light reflected by the transfer belt from the corresponding light emitting unit Ei to the light receiving unit Di). Since the optical axis of the light receiving microlens LDi receives more reflected light in the light receiving part Di, the optical axis of the light receiving microlens LDi is shifted parallel to the light emitting part axis perpendicular to the light emitting surface). Is shifted by “0.020 mm toward the irradiation system” in parallel to the light receiving unit axis passing through the center of the light receiving unit Di.

The “inter-lens pitch (distance between optical axes)” in the sub-direction of the irradiation microlens LEi and the light-receiving microlens LDi is 0.445 mm. The “interval in the sub direction” between the light emitting unit Ei and the corresponding light receiving unit Di is 0.500 mm.
The distance from the light emitting portion to the irradiation microlens is 0.800 mm, and the distance from the back surface (plane) of the irradiation microlens array to the transfer belt surface as a support member is 5 mm. These distances apply in all examples (models) shown below.
The refractive index of the material constituting the irradiation microlens array and the light receiving microlens array is “1.53” in all the following examples.

  A microlens array having such a specification (referred to as an integrated combination of an irradiation microlens array and a light receiving microlens array, the same applies hereinafter) is referred to as “model I”.

In the model I, the lens diameter of the light receiving microlens is made larger than the lens diameter of the irradiation microlens, so that diffuse reflection light from the toner pattern can be “received more”.
In addition, by making the lens surface radius of curvature of the light receiving microlens LDi “smaller than that of the irradiation microlens LEi”, total reflection inside the light receiving microlens increases, so that the amount of specularly reflected light can be reduced. It is.

  By reducing the lens surface curvature radius of the light receiving microlens LDi, the light receiving portions D4 and D6 adjacent to the light receiving portion D5 corresponding to the light emitting portion to be turned on (for example, the light emitting portion E5 at the center in the arrangement direction) are arranged. The light beams that have passed through the light receiving microlenses LD4 and LD6 can be greatly refracted, and the "diffuse reflected light" from the toner pattern is transmitted to the light receiving portions D1, D2, D8, D9, etc., away from the light receiving portion D5. An increase in “amount of received diffuse reflected light” at these light receiving portions D1, D2, D8, D9 and the like can also be expected.

  Each of the irradiation microlens LEi and the light-receiving microlens LDi is a “convex spherical lens”, and the irradiation microlens LEi has a condensing power on the incident surface (convex spherical surface) of the lens. The exit surface (plane) does not have a condensing power. In the light-receiving microlens LDi, the incident surface (plane) of the lens does not have a condensing power, but the exit surface (convex spherical surface) has a condensing power.

Hereinafter, density detection processing performed using the optical sensor device 2245 will be described.
For simplicity of explanation, any light emitting part Ei of i = 1 to 9 is turned on, and the detection light Si from the lighted light emitting part Ei is regularly reflected by the transfer belt 2040. The maximum value of the amount of light received by the light receiving unit Di (i = 1 to 9) is normalized to 1.
FIG. 16A shows the normalized amounts of light received by the light receiving portions D1 to D9 when the light emitting portions E1 to E9 are individually emitted.
Note that the amounts of light received in the following description are all the results of a calculation simulation using the reflective optical sensor of the present invention except for those described with reference to FIG.

In the example shown in FIG. 7, the position detection pattern PP moves to the “detection light irradiation position” before the density detection pattern TP, and the toner pattern position detection process precedes the toner density detection process. However, the density detection pattern TP may be detected “before the position detection pattern PP” by reversing the creation positions in the sub-direction of the density detection pattern and the position detection pattern. Needless to say.
In the example in the description, the “main position in the main direction” of the light emitting section E5 in the “array center” of the nine light emitting sections E1 to E9 and the “center position in the main direction” of the toner pattern match. A toner pattern is transferred and formed on the transfer belt 2040. FIG. 16B shows this state.

  The length in the main direction of each rectangular pattern of the density detection pattern PP: Lp is 1.0 mm. Therefore, the rectangular pattern is in the state of FIG. 15B (the position of the light emitting portion E5 is the main direction of the rectangular pattern). In the center position), as shown in FIG. 15 (e), the light is irradiated with three detection lights S4, S5, and S6.

The light emitting portions E1 to E9 are sequentially turned on and off, and the position of the toner pattern can be confirmed based on the amount of light received by each light receiving portion at that time. The amount of light received by each of the light receiving portions D1 to D9 at this time is shown in FIG.
The amount of light received by each of the light receiving parts D1 to D9 when the light emitting parts E4 to E6 are individually turned on is lower than when the other six light emitting parts E1 to E3 and E7 to E8 are individually turned on ( From this, it can be seen that the toner pattern certainly exists at the position where the detection light beams S4 to S6 are irradiated.
Accordingly, the detection light S4 to S6 may be used for toner density detection, but for the sake of simplicity of explanation, the “light reception amount distribution when the light emitting portion E5 is turned on” is used for toner density detection. This is true for all the examples shown below.

As a condition for the calculation simulation, the light emitted from the light emitting portion Ei is “regular reflection only” when irradiating the transfer belt surface as shown in the left diagram of FIG. In this case, as shown in the right diagram of FIG. 16D, “not only the uniform diffusion but also the specular reflection component” is included.
As a condition for the calculation simulation, the “reflectance by the transfer belt” was set to 100%. It is assumed that 50% of the detection light irradiated on the toner pattern is transmitted through the toner pattern and 50% is reflected.
Of the 50% reflection, the diffuse reflection component was 50% of the reflection, and the rest was the regular reflection component.

  As an example, in FIGS. 15E and 15F, when the rectangular pattern moves in front of the reflective optical sensor, the printer control device 2090 “lights the light emitting units E4 to E6 repeatedly and repeatedly”.

As illustrated in FIG. 15F, the detection lights S4 to S6 are regularly reflected and diffusely reflected on the surface of the rectangular pattern.
Hereinafter, the regularly reflected light is also referred to as “regular reflected light”, and the diffusely reflected light is also referred to as “diffuse reflected light”.

  The “processing device (not shown)” of each reflective optical sensor individually determines the amount of light received by each light receiving unit Di based on the output signals of the light receiving units D1 to D9 when the detection light S5 irradiates a rectangular pattern. And stored as “detected received light amount” in “memory not shown”.

  The middle diagram in the middle of FIG. 16C shows the amount of light received by each light receiving unit Di when the detection light S5 irradiates the rectangular pattern p5. In this state, the regular reflection light received by the light receiving portions D4 to D6 is reduced compared to when the detection light S5 irradiates the surface of the transfer belt 2040, while the diffuse reflection light is received by light receiving portions other than the light receiving portions D4 to D6. Light is received at.

  In general, as the “toner density in the rectangular pattern Pi” increases, the regular reflection light monotonously decreases and the diffuse reflection light monotonously increases among the reflected light from the rectangular pattern.

  As shown in FIG. 16B, the printer controller 2090 (FIG. 1) determines that “the yellow toner density is based on the amount of light received by each light receiving portion Di when the detection light S5 irradiates the rectangular pattern TP1. It is determined whether or not “appropriate”, and “appropriate magenta toner density” is determined based on the amount of light received by each light receiving portion Di when the rectangular pattern TP2 is irradiated, and each when the rectangular pattern TP3 is irradiated “Appropriateness of cyan toner density” is determined based on the received light amount of the light receiving part Di, and “appropriateness of black toner density” is determined based on the received light quantity of each light receiving part Di when the rectangular pattern TP4 is irradiated. .

  When the printer control device 2090 determines that “the toner density is not appropriate”, the control device 2090 controls the development processing system of the “corresponding station” so that the toner concentration is appropriate.

Next, toner density detection using the amount of light received by each light receiving portion Di will be described.
As shown in FIG. 16 (a), when the irradiated portion of the detection light is “a transfer belt that is a regular reflector with respect to the detection light”, when the light emitting portion E5 is turned on, the regular reflected light from the transfer belt is Light is received only by the light receiving unit D5 corresponding to the light emitting unit E5 and the light receiving unit D4 and the light receiving unit D6 adjacent to the light receiving unit D5. The amount of received light at the light receiving portions D3 and D7 is set to 0 because it is negligible compared to the amount of received light at D6.

When the detection light is applied to the toner pattern, as shown in FIG. 16C, the reflected light is received by “all light receiving portions D1 to D9”.
When the light emitting unit E5 emits light, it can be easily understood that the amount of light received by the light receiving units D1 to D3 and D7 to D9 is “due to diffuse reflected light”. This is because the specularly reflected light is received only by the light receiving portions D4 to D6.
The amount of light received by the light receiving portions D4 to D6 is the amount of light received by both regular reflection light and diffuse reflection light from the toner pattern. Since it is difficult to accurately divide the amount of light received by the three light receiving units D4 to D6 into “amount of light received by regular reflection light and a light reception amount by diffuse reflected light”, the light receiving unit is used by using the following two assumptions. The amount of received light in D4 to D6 is handled.

In the “first assumption”, among the “light receiving amounts at the light receiving portions D4 to D6” when the light emitting portion E5 is caused to emit light, the light receiving amount at the light receiving portion D5 is the portion where the detection light is irradiated. Regardless of the surface or toner pattern, the amount of light received is “all specularly reflected light”.
The amount of light received by the light receiving unit D4 and the light receiving unit D6 includes both the amount of received regular reflected light and the amount of diffuse reflected light due to the toner pattern.
In handling based on the first assumption (hereinafter referred to as “first handling”), “the amount of light received by the two light receiving portions D4 and D6” is not used for toner density detection. That is, in this handling, when the detection light from the light emitting unit E5 irradiates the toner pattern, the light receiving amounts in the light receiving units D1 to D3 and D7 to D9 are all “light received by diffuse reflected light”.

  In the “second assumption”, the amount of light received by the light receiving unit D5 when the light emitting unit E5 emits light is “regular reflection all” regardless of whether the detection light irradiates the transfer belt surface or the toner pattern. Assuming that “the amount of light received by the light” is, the light receiving amount distribution when the irradiated portion of the detection light is a transfer belt and the light receiving amount distribution when it is a toner pattern, the light receiving portions D4 and D6 receive light. The amount is divided into “the amount of light received by the regular reflection light of the toner pattern and the amount of light received by the diffuse reflection light of the toner pattern”.

  Although the handling based on the second assumption (hereinafter referred to as “second handling”) can “use information on the amount of received light more effectively” than the first handling, it is more complicated than the first handling. It is. The second handling will be described later.

The first handling is applied to the above-mentioned model I of the microlens array, and the light receiving portions D1 to D9 receive the light when detecting the toner pattern (hereinafter, the toner pattern having the density of the toner pattern p5). The amount is shown in FIG.
“D_ALL” in the table represents “sum of received light amounts” of the light receiving units D1 to D9, “positive” in the table represents the received light amount of the light receiving unit D5, and “diffusion” in the table represents the light receiving units D1 to D3. And “sum of received light amounts” of a total of six light receiving parts, ie, the light receiving parts D6 to D9. Note that “E-03” or the like added to the numerical value means that the numerical value is multiplied by “10 ⁻³ ”. The same applies to the following.

  The amount of light received by the light receiving portions D1 to D9 is normalized by the amount of light received by the light receiving portion D5 when “the irradiation portion by the detection light is a transfer belt”, and the amount of light received in other examples shown below is similarly detected. This represents a value obtained by standardizing the amount of light received by each light receiving unit when the object to be irradiated with the light is a transfer belt by “the amount of light received by the light receiving unit D5 when using a model I microlens array”.

  As a comparative example for the model I of the micro lens array (the combination of the irradiation micro lens array and the light receiving micro lens array as described above), two examples of the micro lens array model, that is, the reference model I and the reference model II are I will give you.

The “reference model I” is a model of a microlens array in which the lens surface curvature radius, lens diameter, and lens thickness of the irradiation microlens and the light receiving microlens are all the same. That is, in the reference model I, an irradiation microlens array and a light receiving microlens array are formed by 18 identical microlenses.
In the “reference model II”, the lens diameter and lens thickness of the light receiving microlens are larger than the lens diameter and lens thickness of the irradiation microlens, but the lens surface curvature radius is different between the irradiation microlens and the light receiving microlens. This is a model of a microlens array having the same value.

In the reference model I, as described above, each irradiation microlens and each light receiving microlens have the same shape. As a specific example, the lens diameter of the microlens is 0.529 mm, the lens surface radius of curvature is 0.430 mm, and the lens thickness is 1.228 mm.
The optical axis of each irradiation microlens is parallel to the light emitting unit axis that passes through the center of each corresponding light emitting unit and is perpendicular to the light emitting unit in order to effectively guide the detection light of the light emitting unit to the light receiving unit. The optical axis of each light-receiving microlens passes through the center of each corresponding light-receiving unit and is perpendicular to the light-receiving unit axis so that more reflected light can be received. Is parallel to the irradiation system side by 0.020 mm.
The arrangement pitch of the micro lenses in the sub direction (the distance between the optical axes of the irradiation micro lens LEi and the light receiving micro lens LDi) is 0.445 mm. The “interval in the sub direction” between the light emitting unit and the corresponding light receiving unit is 0.500 mm, which is the same as that of the model I.

  17A shows a state in which the reference model I is viewed from the main direction, and FIG. 17B shows a state in which the reference model I is viewed from a direction orthogonal to the arrangement surface of the light emitting unit and the light receiving unit.

FIG. 17C shows a state in which the detection lights S1 to S9 emitted from the light emitting portions E1 to E9 irradiate the transfer belt, and FIG. 17D shows the detection light reflected by the transfer belt. S1 to S9 are shown as being received by the light receiving portions D1 to D9.
FIG. 17E shows a state in which the detection lights S1 to S9 from the light emitting units E1 to E9 irradiate the toner pattern, and FIG. 17F shows the detection lights S1 to S1 reflected by the toner pattern. S9 shows a state in which the light receiving units D1 to D9 receive the light.

FIG. 17G shows the received light amount distribution of the light receiving portions D1 to D9 when the first handling is applied to the reference model I and the transfer belt and the toner pattern are irradiated with the detection light.
FIG. 17H shows the amount of light received when the first handling is applied to the model I and the reference model I and the transfer belt and the toner pattern are irradiated with the detection light. The distance from the back surface of the microlens array to the transfer belt surface is 5 mm for both models.

As apparent from FIG. 17H, the model I of the microlens array has a “light reception amount of diffuse reflected light” from the toner pattern increased by about 80% compared to the reference model I. This can be attributed to the fact that the lens diameter of the light receiving microlens is increased and the radius of curvature of the lens surface of the light receiving microlens is smaller than that of the irradiation microlens.
In Model I, “the amount of diffuse reflected light received” increases, but “the lens thickness of the light receiving microlens” increases due to the small radius of curvature of the lens surface of the light receiving microlens.

  The “difference in lens thickness” between the light-receiving microlens and the irradiation microlens is about 0.190 mm, which makes it slightly difficult to process the microlens array.

In “reference model II”, the lens diameter of each light-receiving microlens was 0.671 mm, the radius of curvature of the lens surface was 0.430 mm, and the lens thickness was 1.319 mm.
The lens diameter of each irradiation microlens was 0.455 mm, the lens surface radius of curvature was 0.430 mm, and the lens thickness was 1.228 mm. The lens diameter is small “one turn compared to the reference model I”.
The optical axis of each irradiating microlens passes through the center of each corresponding light emitting part and is parallel to the light emitting part axis perpendicular to the light emitting part in order to guide the light from the light emitting part to the light receiving part by reflection. The optical axis of each light receiving microlens is parallel to the light receiving unit axis that passes through the center of each corresponding light receiving unit to receive more reflected light and is perpendicular to the light receiving unit. Furthermore, it is shifted by 0.020 mm to the irradiation system side.

  The arrangement pitch of the micro lenses in the sub direction (the distance between the optical axes of the irradiation micro lens LEi and the light receiving micro lens LDi) is 0.445 mm. The “interval in the sub direction” between the light emitting unit and the corresponding light receiving unit is 0.500 mm, which is the same as that of the model I.

  The “interval in the sub direction” between the light emitting unit and the corresponding light receiving unit is 0.500 mm.

18A shows the reference model II viewed from the main direction, and FIG. 18B shows the reference model II viewed from the “direction perpendicular to the arrangement surface of the light emitting unit / light receiving unit”. (C) has shown the mode that detection light S1-S9 inject | emitted from light emission part E1-E9 has irradiated the transfer belt.
FIG. 18D shows a state in which the detection lights S1 to S9 reflected by the transfer belt are received by the light receiving parts D1 to D9, and FIG. 18E shows the detection light S1 from the light emitting parts E1 to E9. To S9 irradiate the toner pattern, and FIG. 18F shows how the detection light beams S1 to S9 reflected by the toner pattern are received by the light receiving portions D1 to D9.

FIG. 18G shows the received light amount distribution of the light receiving portions D1 to D9 when the first handling is applied to the reference model II and the transfer belt and the toner pattern are irradiated with the detection light.
FIG. 18H shows the received light amounts of the light receiving portions D1 to D9 when the first handling is applied to the model I and the reference model II and the transfer belt and the toner pattern are irradiated with the detection light.

  As is clear from FIG. 18 (h), the amount of diffusely reflected light received in model I is increased by about 5% compared to “reference model II as a comparative example”. This is because the amount of regular reflection light from the transfer belt received by the light receiving portion D5 decreases, and the amount of diffuse reflection light from the toner pattern received by the light receiving portions D1 to D3 and D7 to D9 increases. It is a factor.

  Next, a model II for a combination of an irradiation microlens array and a light receiving microlens array will be described.

  In the model II, the lens surface curvature radius, the lens diameter, and the lens thickness are all different between the irradiation microlens and the light receiving microlens, and the light receiving microlens has the same lens surface curvature radius, lens diameter, and lens thickness. The lens has a larger value than that of the “irradiation microlens”.

  The arrangement pitch of the micro lenses in the sub direction (the distance between the optical axes of the irradiation micro lens LEi and the light receiving micro lens LDi) is 0.445 mm. The “interval in the sub direction” between the light emitting unit and the corresponding light receiving unit is 0.500 mm, which is the same as that of the model I.

  Of course, in model II, all the irradiation microlenses constituting the irradiation microlens array have the same lens surface curvature radius, lens diameter, and lens thickness. The lens surface curvature radius, lens diameter, and lens thickness are the same in all the light receiving microlenses constituting the light receiving microlens array.

In the model II microlens array, as compared with the model I, “the overall size of the irradiation microlens and the light receiving microlens (the sum of the lens diameters of the irradiation microlens and the light receiving microlens”) is model I. It was almost the same as the case of, and only the distribution ratio of the lens diameter was changed.
In addition to the amount of diffusely reflected light received, the “sub-direction shift deviation of the lens in the sub-direction (assuming a deviation of ± 0.020 mm from the ideal position)” corresponding to the tolerance when the microlens array is mounted is also verified. To do.
“Sub-direction shift deviation” refers to an amount by which the entire microlens array is displaced in the sub-direction within a two-dimensional plane formed by the main direction and the sub-direction.

  In Model II, in order to effectively guide the detection light emitted from the light emitting unit to the light receiving unit, the lens diameter of the irradiation microlens is made larger than that of Model I, and the lens diameter of the light receiving microlens is modeled. The configuration is smaller than I. As a result, the lens diameter of the irradiation microlens was 0.455 mm, and the lens diameter of the light receiving microlens was 0.700 mm.

The radius of curvature of the lens surface of the micro lens for irradiation was set to 0.470 mm so that the beam diameter of the detection light irradiated on the transfer belt was 0.500 mm or less. In consideration of the processability of the microlens array, the lens thickness of the light receiving microlens is set to be approximately the same as the lens thickness of the irradiation microlens, and the sensitivity unevenness in the light receiving surface forming the light receiving portion is further reduced. Considering the influence, the irradiation micro lens is used under the condition that the lens surface radius of curvature of the light receiving microlens is larger than that of the model I and the reference model II so that the reflected light irradiates a wide range of the light receiving portion. The lens surface curvature radius of the lens and the light-receiving microlens is optimized so that the amount of diffusely reflected light received is maximized under these conditions.
If a “sub-scan shift shift” occurs when the microlens array is attached, the amount of decrease in the light receiving unit output when the microlens is shifted by the same amount in absolute value from the ideal state to the “positive or negative direction” in the sub direction. The distance between the irradiation microlens and the light receiving microlens in the sub direction is also optimized.
Thus, in the model II, the radius of curvature of the lens surface of the light receiving microlens was 0.750 mm, and the distance between the irradiation microlens and the light receiving microlens in the sub direction was 0.480 mm. The lens thickness of the irradiation microlens is 1.189 mm, and the lens thickness of the light receiving microlens is 1.216 mm.

  The “interval in the sub direction” between the light emitting unit and the corresponding light receiving unit is 0.500 mm.

  In the ideal state set as described above, in the model II microlens array, the optical axis of each irradiation microlens corresponds to guide the reflected light of the detection light from the light emitting part to the light receiving part well. The optical axis of each light-receiving microlens passes through the center of each corresponding light-receiving part, and is shifted by 0.035 mm toward the light-receiving system side in parallel to the light-emitting part axis perpendicular to the light-emitting part. It is shifted by 0.015 mm in the “direction away from the irradiation system side” parallel to the light receiving part axis perpendicular to the light receiving part.

FIG. 19A shows the model II viewed from the main direction, FIG. 19B shows the model II viewed from the “direction perpendicular to the arrangement direction of the light emitting and light receiving units”, and FIG. The detection light beams S1 to S9 from the light emitting units E1 to E9 irradiate the transfer belt.
FIG. 19D shows the detection light S1 to S9 reflected by the transfer belt received by the light receiving parts D1 to D9, and FIG. 19E shows the detection light S1 from the light emitting parts E1 to E9. S9 show how the toner pattern is irradiated.
FIG. 19F shows a state in which the detection light beams S1 to S9 reflected by the transfer belt and the toner pattern are received by the light receiving portions D1 to D9.

FIG. 19G shows the received light amount distribution when the “transfer belt and toner pattern” is detected using the model II microlens array. FIG. 19H shows the amount of received light when the “transfer belt and toner pattern” is detected using the model II and model I microlens arrays.
When Model II is used, the amount of diffusely reflected light received is about 10% less than that when Model I is used.

FIG. 19 (i) shows a case where “the sub-direction shift deviation does not occur (referred to as an ideal state)” when detecting the transfer belt using the model I, the model II, the reference model I, and the reference model II. “D_ALL change” is shown when the sub-direction shift deviation (shown as “Y shift deviation” in FIG. 19I) occurs ± 0.020 mm.
“D_ALL” represents “sum of received light amounts” of the light receiving units D1 to D9, “positive” in the table represents the received light amount of the light receiving unit D5, and “diffusion” in the table represents the light receiving units D1 to D3 and the light receiving unit. This represents the “sum of received light amounts” of a total of six light receiving portions D6 to D9.

“D_ALL” standardizes “value in ideal state” to 1 for each model.
From this result, in the model I, the reference model I, and the reference is also the Dell II, the illumination system, the light receiving system, and the entire microlens array are shifted in the negative direction of the sub direction by “Y = −0.02 mm”. The relative received light amount decreases “larger” when shifted in the positive direction when “Y = 0.02 mm” is shifted in the direction. However, in the case of Model II, the degree of decrease is “sub-direction”. It is substantially symmetrical with respect to the positive and negative directions of the “shift”, and therefore, using Model II makes the effect of sub-direction shift more effective than using other models of microlens arrays. It can be seen that it can be reduced.

  That is, the lens surface curvature radius, the lens diameter, and the lens thickness are all different between the irradiation microlens and the light receiving microlens, and all of the lens surface curvature radius, the lens diameter, and the lens thickness in the light receiving microlens are “irradiation microlens”. The optical axis of each light receiving microlens is shifted in the direction away from the irradiation system with respect to the light receiving unit axis passing through the center of each corresponding light receiving unit and perpendicular to the light receiving unit. By arranging in this way, it is possible to realize a microlens array in which the amount of diffusely reflected light received is increased and the influence of “sub-direction shift shift” is small.

  Hereinafter, a case where the above-described “second handling” is applied to the model I, the model II, the reference model I, and the reference model II will be described.

  As an illustrative example, consider the case where the second treatment is applied to model I.

In the first handling, when the detection light irradiates the toner pattern, the amount of light received by the light receiving unit D5 is regarded as the amount of light received by the regular reflection light, and the “light reception amount by the regular reflection light” and the “diffuse reflection” from the toner pattern. The amounts of light received by the light receiving unit D4 and the light receiving unit D6 in a state where “the amount of light received by light” is mixed are not used for toner density detection.
Since it is difficult to accurately divide the amount of light received by the light receiving unit D4 and the light receiving unit D6 into “amount of received light by regular reflected light” and “amount of received light by diffusely reflected light” based on the toner pattern, application of the second handling In this case, as in the case of the first handling, the light receiving unit D5 corresponding to the light emitting unit E5 to be lit is “regular reflection light” regardless of whether the detection light irradiates the transfer pattern or the toner pattern. Suppose that

Therefore, in the case of the reflected light from the toner pattern, the received light amounts in the light receiving portions D1 to D3 and D7 to D9 are all the received light amounts of diffuse reflected light. The other three light receiving portions D4 to D6 separate the received light amount into “the amount of regular reflected light and the amount of diffuse reflected light”, but the amount of light received by the light receiving portion D5 corresponding to the light emitting portion E5 that is lit. Is defined as “the amount of received light of regular reflection light”, and therefore, the light reception amount of the light receiving portions D4 and D6 may be “separated into the amount of light reception of regular reflection light and the amount of light reception of diffuse reflection light”.
In the case of reflected light from the transfer belt, the light receiving amount of the light receiving unit D4 is A0, the light receiving amount of the light receiving unit D5 is B0, the light receiving amount of the light receiving unit D6 is C0, and in the case of reflected light from the toner pattern, the light receiving unit The received light amount of D4 is A1, the received light amount of the light receiving unit D5 is B1, and the received light amount of the light receiving unit D6 is C1.
Even if the object to be irradiated with the detection light is changed from the transfer belt to the toner pattern, the “distribution ratio of the regular reflection light in each light receiving unit” does not change. Therefore, in the case of the reflected light from the toner pattern, Then, “B1 · A0 / B0” obtained by multiplying the value obtained by dividing A0 by B0 by B1 is the amount of received regular reflected light, and “A1− (B1 · A0 / B0)” is the amount of diffusely reflected light received.
Similarly, “B1 · C0 / B0” obtained by multiplying B1 by the amount of light received by the light receiving unit D6: C0 divided by B0 is the amount of specularly reflected light and “C1− (B1 · C0 / B0)” is diffused. This is the amount of reflected light received.

As described above, according to the second handling, the received light amount of the light receiving portions D4 and D6 can be separated into the received light amount of the regular reflection light and the received light amount of the diffuse reflection light.
The model II, the reference model I, and the reference model II can also perform “separation between the amount of regular reflection light and the amount of diffuse reflection light” in the same manner as described above. A comparison with Model I is shown.

In FIG. 20A, the amount of light reflected by the toner pattern when the second handling is applied to Model I and “toner density is detected” is expressed as “the amount of light received by the regular reflection light and the diffuse reflection of the toner pattern”. The result of separation is shown in “Amount of light received by light”.
In FIG. 20B, the amount of light reflected by the toner pattern when the second handling is applied to the model II and “toner density is detected” is expressed as “the amount of light received by the regular reflection light and the diffusion amount”. The result of separation is shown in “Amount of received light by reflected light”.

  FIG. 20C shows the amount of light reflected by the toner pattern when the second handling is applied to the reference model I and “detects the toner density”. The result of separation is shown in “Amount of received light by diffuse reflected light”.

  FIG. 20D shows the received light amount of the reflected light from the toner pattern when applied to the second method and the reference model II and “detects the toner density”. The result of separation is shown in “Amount of received light by diffuse reflected light”.

FIG. 20 (e) shows the results of summing the received light amounts of the respective light receiving portions when the second handling is applied to the model I, model II, reference model I, and reference model II.
In FIG. 20F, an ideal state where no “sub-scanning shift deviation” occurs in each case using these four models and a sub-scanning shift deviation (“Y shift deviation” in FIG. 20F) are displayed. )) Occurs in the same manner as FIG. 19 (i) in the case where “Y = ± 0.02 mm” occurs.
As is apparent from FIG. 20, in Model II, “the amount of diffusely reflected light received by the toner pattern” is approximately the same as that of Model I, and “Sub-Voltage” is higher than that of Model I, Reference Model I, and Reference Model II. The structure is strong against “scan shift deviation”.

  Here, how to quantify the toner density from the amount of light received by each light receiving part by the “toner patterns having different toner densities” will be described using model II as a representative example.

When the reflection type optical sensor using Model II detects the transfer belt and “toner patterns p1 to p5 having different densities”, it is assumed that the amount of light received by each light receiving unit is as shown in FIG. Note that the received light amount shown in FIG. 21 is an approximate value, not a simulation result.
The results of dividing the amount of light reflected by the toner patterns p1, p2, p3, p4, and p5 into the amount of regular reflected light and the amount of diffuse reflected light by the second handling are shown in FIGS. c), (d), (e), and (f).

In these drawings, the total value of the received light amount of the regular reflected light is D (positive), and the total value of the received light amount of the diffuse reflected light is D (expanded).
FIG. 21G-1 shows a change in D (positive) when the toner patterns p1 to p5 are detected. As shown in the figure, D (positive) decreases as the toner density increases. This is because the higher the toner concentration, the more toner is attached, and the amount of specularly reflected light decreases. The toner concentration and D (positive) have a one-to-one correspondence. In other words, the toner density corresponding to the measured D (positive) is obtained by measuring D (positive).

FIG. 21G-2 shows a change in D (expansion) when the toner patterns p1 to p5 are detected. D (expansion) increases as the toner density increases when toner patterns p1 to p4 are detected, but starts to decrease when toner pattern p5 is detected.
Intuitively, it seems that D (expanded) is “as the density of the toner constituting the rectangular toner pattern increases, the amount of adhering toner increases and increases due to an increase in diffuse reflected light” In FIG. 21 (g-2), this is not the case.
This is because the detection output result is subtracted.

FIG. 21 (g-3) shows the result of calculating D (expansion) / D (positive) by calculation.
The vertical axis shown in FIG. 21 (g-3): D (expanded) / D (positive) indicates that the density of the toner forming the rectangular toner pattern increases in the order of the rectangular toner patterns p1 to p5. It is an increasing “monotonic function”. Therefore, if this “D (expanded) / D (positive)” is measured, the toner density corresponding to each rectangular toner pattern (horizontal axis in FIG. 21 (g-3)) is obtained.

  In FIG. 21 (g-4), “the amount of received regular reflection light” shown in FIG. 21 (g-1) is normalized by a reference value (here, the amount of received regular reflection light by the transfer belt surface). Relative specular reflectance "is shown. In FIG. 21 (g-5), “D (expansion) / D (positive)” shown in FIG. 21 (g-3) is normalized by a reference value (in this case, the diffuse reflection contribution at the maximum density). Value.

In this way, the divided output corresponding to the diffuse reflection: D (expansion) is divided into the divided output corresponding to the regular reflection: D (positive).
A new value may be obtained using the value divided by D: (expanded) / D (positive), and the toner density may be obtained from this value.

  The microlens array described above with respect to the above-mentioned various models is “the irradiation microlens array and the light receiving microlens array are integrally formed” as shown in FIG. The invention according to No. 7 is characterized.

  In FIG. 15A and the like, the state viewed from the “main direction” that is the arrangement direction of the irradiation microlens and the light receiving microlens is shown, and the arrangement state of these microlenses is not particularly mentioned in the above description. It was.

  In each model described above, the arrangement pitch of the irradiation microlenses in the main direction is 0.4 mm, and the distance between the optical axes of the irradiation microlens LEi and the light receiving microlens LDi is 0.5 mm.

  On the other hand, for example, in “Model I”, the irradiation microlens LEi has a lens diameter of 0.415 mm, and the light receiving microlens LDi has a lens diameter of 0.712 mm.

  Accordingly, when the irradiation microlens LEi and the light-receiving microlens LDi are the above-mentioned “circular lens surface having a lens diameter”, these microlenses are “arrayed in the main direction with an array pitch of 0.4 mm”. It is not possible.

  In other words, the arrayed arrayed microlenses for irradiation and light reception have a “lens surface width in the main direction” of 0.4 mm.

Therefore, the microlens array of each model described above is as shown in the upper left diagram of FIG. 21H when viewed from the direction of the optical axis of each microlens.
That is, “irradiation microlens and light receiving microlens” corresponding to each other are in contact with each other in the sub direction to form an “ellipsoidal compound lens surface” that is long in the sub direction. the lens surface in the width direction (main direction), are each other in contact with the same pitch as the array pitch of the light emitting portion (0.4mm in the example in the description) (claim 5).

Therefore, the microlens array of each model described above is as shown in the upper left diagram of FIG. 21H when viewed from the direction of the optical axis of each microlens.
That is, “irradiation microlens and light receiving microlens” corresponding to each other are in contact with each other in the sub direction to form an “ellipsoidal compound lens surface” that is long in the sub direction. the lens surface in the width direction (main direction), are each other in contact with the same pitch as the array pitch of the light emitting portion (0.4mm in the example in the description) (claim 5).

In the embodiment shown in FIG. 21 (h), the "back" side of the integrated microlens array and the light-receiving microlens array irradiation "microlens array", it is provided with "shielding film" (claim 3 ).

When an arbitrary light emitting unit is turned on, the light from the light emitting unit is not only the irradiation microlens corresponding to the light emitting unit, but also a plurality of microlenses (irradiation microlens) arranged around the irradiation microlens. In some cases, the transfer belt or the toner pattern is irradiated through the light receiving microlens).
Such light becomes “flare light (stray light)” with respect to the detection light. When the toner pattern is irradiated, the amount of light received by each light receiving portion is changed. If the change in the amount of light received due to flare light exceeds a negligible level, erroneous detection of the toner pattern position and toner density occurs.
By providing a light-shielding film on the front surface or the back surface of at least one of the irradiation microlens array and the light receiving microlens array, or a predetermined region on the front and back surfaces, the influence of flare light can be reduced or eliminated.

As shown in FIG. 21 (h), when the distance between the light shielding film and the “end portion in the sub-direction of the microlens” is set to 0.300 mm or less, the diffuse reflected light when the flare light irradiates the toner pattern. The amount of received light is about 0.1% with respect to the maximum amount of received light in each light receiving portion when the detection light irradiates the toner pattern, so the “position / toner density” of the toner pattern by flare light The impact on the detection will be negligible.
FIG. 21 (h) shows a case where “a light-shielding film is provided only on the back surface” of the microlens array. However, by providing a light-shielding film at a predetermined position on the surface side of the microlens array, as described above. It is needless to say that a light shielding film may be provided only on the front surface of the microlens array or a light shielding film may be provided on both the front and back surfaces of the microlens array as long as the effect can be obtained.
In the example shown in FIG. 21H, the “irradiation microlens and the light receiving microlens” corresponding to each other are in contact with each other in the sub direction and have a long “oval compound lens surface” in the sub direction. None, this compound lens surface is in contact with the width direction (main direction) of the compound lens surface at the same pitch as the arrangement pitch of the light emitting parts (0.4 mm in the example in the description). The present invention is not limited to such an “ellipse shape long in the sub direction”, but may be a “rectangular shape (strip shape) having the sub direction as a longitudinal direction” as shown in FIG. The light shielding film may be provided in the same manner as in FIG. 21H, and the light shielding film is provided in the same manner as in FIG.

  The “lens diameter of the microlens” in the example shown in FIG. 21 (i) is the “diameter in the sub-direction” of the irradiation microlens and the light receiving microlens forming the rectangular compound lens surface. Even in such a shape, naturally, the lens area of the light receiving microlens is larger than that of the irradiation microlens.

First, in connection with the example shown in FIG. 16, it is stated that “the light emitting portions E1 to E9 are sequentially turned on and off, and the position of the toner pattern can be confirmed based on the amount of light received by each light receiving portion at that time”. It was. In this case, if the time taken to sequentially turn on / off the light emitting units E1 to E9 is long, the toner pattern moves in the sub-direction during this time, so the positional relationship between the reflective optical sensor and the toner pattern. May change and affect the detection accuracy.
In such a case, as in the invention described in claim 6 , N light-emitting portions are divided into “m sets in the arrangement direction so that each set has a substantially equal number of light-emitting portions. It is possible to have an irradiation control device that causes the parts to “blink in synchronization with the arrangement order”.

As in the examples described above, when N = 9, this can be divided into three sets in the arrangement direction, and three light emitting units can be distributed to each set.
That is, the light emitting units E1 to E3 are a first set, the light emitting units E4 to E6 are a second set, and the light emitting units E7 to E9 are a third set.

Then, the first to third sets of light emitting units are blinked in synchronization with the arrangement order.
That is, “the first set of light emitting units E1, the second set of light emitting units E4, and the third set of light emitting units E7” are blinked simultaneously, and then “the first set of light emitting units E2 and the second set of light emitting units E5 and The third set of light emitting units E8 "are simultaneously flashed, and then the" first set of light emitting units E3, the second set of light emitting units E6, and the third set of light emitting units E9 "are simultaneously flashed.

  In this way, compared with the case where the light emitting portions E1 to E9 are sequentially blinked, the number of times all nine light emitting portions are blinked can be reduced to three times, and the amount of displacement of the toner pattern during this period is also small. Further, the length in the sub-direction of the rectangular toner pattern p1 or the like: Wp (see FIG. 9) can be reduced, or detection can be handled even when the moving speed of the toner pattern is increased.

Next, “toner pattern position detection processing” using a reflective optical sensor will be described.
As an example, a reflection type optical sensor using the above-described model I microlens array is used. For simplicity of explanation, as shown in FIG. 22A, the light emitting section Ei (i = 1 to 9) is turned on, and the detection light Si (i = 1 to 9) is regularly reflected by the transfer belt 2040. The maximum value of the amount of light received by the light receiving unit Di (i = 1 to 9) is set to 1.
As shown in FIG. 22B, the position detection pattern is transferred onto the transfer belt 2040 so that the center position of the light emitting portion E5 and the center position of the toner pattern coincide with each other in the main direction. .

The printer control device 2090 shown in FIG. 1 measures the timing when the position detection pattern PP approaches the reflective optical sensor, and continuously turns on the light emitting unit E5.
The detection light from the light emitting unit E5 sequentially irradiates the line patterns LPY1 to LPK2 as the transfer belt 2040 rotates (see FIGS. 22C and 22A).

  Then, the printer control device 2090 traces the output signal of each light receiving unit in time, and the time from when the detection light irradiates the line pattern LPY1 to the line pattern LPM1: Tym, line shape Time from irradiation of the pattern LPM1 to irradiation of the line-shaped pattern LPC1: Tmc, time from irradiation of the line-shaped pattern LPC1 to irradiation of the line-shaped pattern LPK1: Tck is detected (FIG. 22C). (See (B)).

  The output signal of each light receiving unit is amplified and inverted, and passes through a comparison circuit that compares with a predetermined reference value.

If the time: Tym, Tmc, and Tck are substantially the same, the printer control apparatus 2090 determines that “the positional relationship in the sub-direction between the color toner images is appropriate”, and the times: Tym, Tmc, and Tck are “substantially the same”. If not, it is determined that “there is a deviation in the positional relationship between the sub-directions of the respective color toner images”.
When the printer control apparatus 2090 determines that the positional relationship has a deviation, the printer controller 2090 obtains a deviation amount of the positional relationship from the time difference between Tym, Tmc, and Tck, and sends the deviation amount to the scanning control apparatus. The scanning control device adjusts the timing of the optical scanning start in the corresponding station so that the inputted “deviation amount” is zero.

  The printer control device 2090 also irradiates the line pattern LPM2 after irradiating the line pattern LPM1 after the time when the detection light irradiates the line pattern LPY2 until the line pattern LPY2 is irradiated. Time until irradiation: Tm, time from irradiation of the line pattern LPC1 to irradiation of the line pattern LPC2: Tc, time from irradiation of the line pattern LPK1 to irradiation of the line pattern LPK2: Tk It detects (refer FIG.22 (c)).

  Then, the printer control apparatus 2090 compares the times: Ty, Tm, Tc, and Tk with “a reference time predetermined for these times”. If all of the times: Ty, Tm, Tc, and Tk are the same as the reference times for these, the printer control device 2090 determines that “the positional relationship between the color toner images in the main direction is appropriate”.

For example, if the time: Ty is different from the reference time, the printer control device 2090 obtains the “position shift amount in the main direction: ΔS” of the yellow toner image using the following equation (1) (FIG. 22 ( d) See (A) and FIGS. 22 (d) and 22 (B)).
ΔS = V · ΔT · cot θ (1)
In Expression (1), “V” is the moving speed of the transfer belt 2040 in the sub-direction, “ΔT” is the difference between time: Ty and its reference time, and “θ” is the inclination angle with respect to the main direction of the line pattern LPY2. is there. The calculated misregistration amount: ΔS is input to the scanning control device.

  The scanning control device adjusts the Y station so that “the input positional deviation amount: ΔS becomes 0”. The printer control device 2090 also obtains “the center position of the toner pattern in the main direction” from the positional deviation amount: ΔS.

  In the above description, the toner pattern on the transfer belt 2040 is detected. However, the present invention is not limited to this, and depending on the form of the image forming apparatus, the toner pattern on the photosensitive drum or the intermediate transfer belt is detected. Needless to say, you can.

  As the image forming apparatus, the color printer 2000 including a plurality of photosensitive drums has been described. However, the present invention is not limited to this. For example, the present invention can be applied to a printer that includes one photosensitive drum and forms a single color image.

  Further, it may be an image forming apparatus other than a printer, for example, a copier, a facsimile, or a multifunction machine in which these are integrated.

  Although not described, the reflection type of the present invention is also used when the toner density and position of the toner pattern on the photosensitive drum after the toner adheres to the latent image by the developing roller or the toner density or position is detected. An optical sensor is applicable.

In addition, the case of “transfer belt with smooth surface (regular reflection only on the surface)” was given above, but regarding “transfer belt with non-smooth surface (reflection on the surface includes diffuse reflection)” The above idea can also be applied.
That is, if the “detection output distribution by the regular reflector” can be measured by using an appropriate means, it can be “divided into a regular reflection contribution and a diffuse reflection contribution” by using it.
For example, the detection output distribution can be measured in advance using a regular reflector, and the measured distribution can be stored in a memory or the like, or a “surface with a smooth surface” can be formed on a part of the transfer belt. Further, regular reflection at this portion can be detected, or a movable regular reflector can be provided in the image forming apparatus, and the regular reflector can be moved and detected when necessary.

As described above, “the first reference received light amount that is the amount of light received by each light receiving portion when the surface of the support member is irradiated with the detection light, and the case where the toner pattern on the support member is irradiated with the detection light. Referring to the second reference amount of light received is the amount of light received by the light receiving portion, the second reference amount of light received, the processing unit "or to separate to the amount of light received by the light receiving amount and the specular reflection light by the diffuse reflection light, wherein The irradiation control apparatus according to Item 6 is realized by the printer control apparatus 2090 in the embodiment described above.

JP-A-1-35466 JP 2004-21164 A JP 2002-72612 A JP 2004-309292 A JP 2004-309293 A JP 2009-258601 A

Claims (9)

A reflective optical sensor for detecting the toner concentration or position of a toner pattern on a support member,
An illumination system having N (≧ 3) light emitting units arranged in a line in a first direction;
A light receiving system having N light receiving portions arranged in one direction parallel to the first direction;
An illumination optical system having N irradiation microlenses in one direction parallel to the first direction;
A light receiving optical system having N light receiving microlenses in one direction parallel to the first direction,
Arrangement pitch of N light emitting parts of the illumination system, arrangement pitch of N microlenses of the illumination optical system, arrangement pitch of N light receiving parts of the light receiving system, and N pieces of the light receiving optical system The microlens array pitch is the same,
The illumination microlens and the light receiving microlens is formed of the same optical material, plano-convex the irradiation microlens having a convex surface facing the incident surface, a plano-convex shape the light-receiving microlens having a convex surface on the exit surface And
The optical axis of each illumination microlens is parallel to the corresponding light emitting unit central vertical light emitting portion axis as the light emitting portion of the predetermined distance deviation to the light receiving system side with respect to the light emitting unit shaft,
The optical axis of each light-receiving micro lens is parallel to the corresponding light receiving section perpendicular light receiving unit axis as the light receiving portion to the center of, with respect to the light receiving section shaft, a predetermined distance deviation to the illumination system side And
Lens area of the light-receiving micro lens is larger than the lens area of the irradiation microlens,
Lens surface radius of curvature of the light-receiving microlenses is smaller than the lens surface curvature radius of the illumination microlens,
Reflective optical sensor in which the lens thickness of the light-receiving microlenses, wherein the larger the lens thickness of the irradiated microlens. A reflective optical sensor for detecting the toner concentration or position of a toner pattern on a support member,
An illumination system having N (≧ 3) light emitting units arranged in a line in a first direction;
A light receiving system having N light receiving portions arranged in one direction parallel to the first direction;
An illumination optical system having N irradiation microlenses in one direction parallel to the first direction;
A light receiving optical system having N light receiving microlenses in one direction parallel to the first direction,
Arrangement pitch of N light emitting parts of the illumination system, arrangement pitch of N microlenses of the illumination optical system, arrangement pitch of N light receiving parts of the light receiving system, and N pieces of the light receiving optical system The microlens array pitch is the same,
The irradiation microlens and the light receiving microlens are formed of the same optical material, the irradiation microlens has a plano-convex shape having a convex surface on the incident surface, and the light receiving microlens has a plano-convex shape having a convex surface on the exit surface. ,
The optical axis of each illumination microlens is parallel to the corresponding light emitting unit central vertical light emitting portion axis as the light emitting portion of the predetermined distance deviation to the light receiving system side with respect to the light emitting unit shaft,
Optical axis of each light receiving microlens is parallel to the corresponding light receiving section perpendicular light receiving unit axis as the light receiving portion to the center of, with respect to the light receiving unit shaft, misalignment on the side away from the illumination system And
The irradiation microlens and the light receiving microlens are different from each other in lens area, lens surface radius of curvature, and lens thickness, and the lens area of the light receiving microlens is larger than the lens area of the irradiation microlens,
Reflective optical sensor, wherein the both lens surfaces of curvature radius and lens thickness of the light-receiving microlens, a lens surface curvature radius of the irradiation microlenses, larger than the lens thickness. The reflective optical sensor according to claim 1 or 2,
At least one of the reflection type optical sensor, characterized in that at least one of the predetermined regions of the front and rear side, the light shielding film is formed of the irradiation microlens and the light receiving microlens. The reflection type optical sensor according to any one of claims 1 to 3,
A reflection-type optical sensor, wherein an irradiation microlens and a light-receiving microlens are integrally formed. The reflective optical sensor according to claim 4, wherein
An i (1 ≦ i ≦ N) -th irradiation microlens from a predetermined side in the irradiation optical system, and an i (1 ≦ i ≦ N) th light-receiving microlens from the predetermined side in the light-receiving optical system ; However, they form an oval or rectangular compound lens surface in contact with each other in the sub-direction,
A reflective optical sensor characterized in that the compound lens surface is in contact with the array lens surface at the same pitch in the width direction of the compound lens surface. In the reflective optical sensor according to any one of claims 1 to 5,
N light emitting units are divided into m sets in the arrangement direction, each set has a substantially equal number of light emitting units, and has an irradiation control device that blinks each set of light emitting units in synchronization with the arrangement order. A reflective optical sensor. The reflection type optical sensor according to any one of claims 1 to 6,
Number of light emitting units, light receiving units, irradiation microlenses, light receiving microlenses: N
7 ≦ N ≦ 31
A reflection-type optical sensor characterized by being an odd number within the range. A latent image carrier;
An electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image;
A developing device for visualizing a toner image by developing the electrostatic latent image,
A transfer device for transferring a sheet-like recording medium by the transfer belt the toner image,
A reflective optical sensor used to detect the toner density or position of the toner pattern formed using the latent image carrier or the transfer belt as a support member, or the toner density and position of the toner pattern;
The electrostatic latent image forming unit includes a charging unit that uniformly charges the latent image carrier, and an optical scanning device that performs optical scanning on the uniformly charged latent image carrier and forms an electrostatic latent image according to image information. And
An image forming apparatus comprising the reflective optical sensor according to claim 1 as the reflective optical sensor. The image forming apparatus according to claim 8.
A tandem type image forming apparatus that forms toner images of different colors on a plurality of latent image carriers and forms a multicolor image by superimposing the plurality of toner images.

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