JP2005337749A - Reflected light sensing method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sensor for sensing an always stable and accurate adhesion amount over the whole adhesion amount region in the sensing of the adhesion amount of a powder such as toner or the like. <P>SOLUTION: In the optical sensor composed of one light emitting element and at least two light detecting elements and equipped with a correction mechanism for operationally processing the output of regular reflected light and the output of diffused reflected light and correcting the operationally processed output values to a predetermined level, a standard object to be sensed for regular reflected light is used for regular reflected light while a standard object to be sensed for diffused light is used for diffused light and adjustment for determining the diffused light output level obtained by the standard object to be sensed for diffused light is performed based on the regular reflected light output value obtained by the standard object to be sensed of reflected light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reflected light detection method and an image forming apparatus. More specifically, the present invention relates to a reflection type optical sensor used for detecting the amount of powder adhering in an image forming apparatus which is one of apparatuses using powder such as toner. Related to output adjustment.

Conventionally, in an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, a density detection toner patch is provided on an image carrier such as a photoconductor in order to always obtain a stable image density. (Hereinafter also referred to as a density pattern or density detection pattern), the patch density is detected by an optical detection means, and the development potential is changed based on the detection result (specifically, LD power, charging bias) , Change of development bias).
In the case of the two-component development method, image density control is performed such that the maximum target adhesion amount (adhesion amount for obtaining a target ID) becomes a target value by changing the toner density control target value in the developing device. It is carried out.

As such a density detection patch detection means, a reflection type optical sensor in which an LED is used as a light emitting element (light emitting means) and a PD (photodiode) or PTr (phototransistor) is used as a light receiving element (light receiving means) is generally used. Known to.
Conventionally, as a configuration of a reflection type optical sensor, a configuration in which only specular reflection light from a toner patch is a detection target (for example, Patent Document 1), and a configuration in which only diffuse reflection light from a toner patch is a detection target (for example, Patent Document 2) and a configuration (for example, Patent Document 3) in which both reflected lights are detected are known.
The specularly reflected light output obtained by detecting specularly reflected light is the light that is specularly reflected by the detection target surface (the incident angle and the reflection angle are equal), and the detection target surface is smooth (= specular glossiness is In the case of high), the irradiated light is only slightly diffused on the detection target surface, and most of the light is specularly reflected as specular reflection light.
On the other hand, unlike the state of the detection target surface where the specularly reflected light output is obtained (the state where the specular gloss is high), when powder such as toner adheres, the incident light is diffused in the toner. Therefore, the amount of specular reflection light decreases, and conversely, the amount of diffuse reflection light, in other words, the amount of reflection light that does not become regular reflection increases. Such diffuse reflected light is conspicuous when color toner is used as a detection target, and in the case of black toner, the irradiated light is hardly absorbed and thus does not increase so much.

Conventionally, when a color image is obtained using not only black but also a plurality of colors of toner, a latent image carrier is formed by combining regular reflection light and diffuse reflection light for toners of colors other than black and black. The amount of toner adhering on a certain photoconductor or transfer belt is detected (for example, Patent Document 4).
On the other hand, as a method for detecting the adhesion amount of toner of each color for a color image using toner of black and a color other than black by combining the regular reflection light output and the diffuse reflection light output, for example, regular reflection light Output corresponding to a pure specular light component in the output obtained as the specular reflection light output by subtracting the diffuse reflection light output from the specular reflection light output at the output of the light receiving sensor that can obtain the output and the diffuse reflection light output respectively. There has been proposed a method for determining the value (for example, Patent Document 4).

JP 2001-324840 A (paragraph "0035" column) JP-A-5-249787 (paragraph "0019" column) JP 2001-194443 A (paragraph "0004" column) JP-A-10-319669 (paragraph “0018” column)

In the optical sensor used to determine the toner adhesion amount of each color, if there is a variation in sensitivity in each element of light emission and light reception, in particular, if there is a variation in diffuse reflection light output, it is a pure positive based on the regular reflection light output. There is a possibility that the reflected light output cannot be determined, and the toner adhesion amount cannot be accurately determined.
One of the causes of the variation in the diffuse reflected light output is the light emitting element output and the light receiving element output lot variation (sensor sensitivity variation). In other words, it is assumed that each element is adjusted so that there is no variation in output (sensitivity) at the shipping inspection stage, but it cannot be said that all shipping lot units are subject to adjustment. Or it may be shipped without proper adjustment. For this reason, when an element that is not sufficiently adjusted is used when determining the toner adhesion amount in the image forming apparatus, there is a possibility that the toner adhesion amount cannot be properly determined due to variations in sensitivity of the optical sensor. .

  An object of the present invention is to provide a reflected light detection method capable of accurately determining the adhesion amount of powder such as toner even when the sensitivity variation of the optical sensor has not been eliminated, and to perform appropriate image density control using the same. An object is to provide an image forming apparatus.

  The invention according to claim 1 is a reflected light detection method using one light emitting element and at least two light receiving elements, wherein the specular reflection light output and the diffuse reflection light output are subjected to arithmetic processing, and the arithmetic processing output is performed. In an optical sensor having a correction mechanism that corrects the value to a predetermined level, a standard detection object for specular reflection light is used for the specular reflection light, and a standard detection object for diffused light is used for the diffuse light, respectively. An adjustment for determining the diffused light output level obtained by the standard detected object for diffused light is performed based on the specularly reflected light output value obtained by the standard detected object of reflected light.

  According to a second aspect of the present invention, in the reflected light detection method according to the first aspect, the diffused light output level is set by using, as the standard detected object, an object that does not cause a change in reflectance over time or over time. It is characterized in that adjustments for determination are made.

  According to a third aspect of the present invention, in the reflected light detection method according to the first aspect, the diffused light output level can be set by using a powder having a particle size of 500 μm or less as the standard detected object for the diffused light. It is characterized in that adjustments for determination are made.

  According to a fourth aspect of the present invention, in the reflected light detection method according to the first aspect, the standard detected object is a powder having a diffuse reflectance of 90% or more in an LED wavelength region of 800 to 1100 nm. An adjustment for determining the diffused light output level is performed.

  According to a fifth aspect of the present invention, in the reflected light detection method according to the first aspect, the regular reflectance on the material surface is preferably 3 to 15%, preferably as the one for the regular reflected light among the standard detected objects. An adjustment for determining the diffused light output level is performed by using 5 to 10% of a substance.

  A sixth aspect of the present invention is the reflected light detection method according to the third or fourth aspect, wherein the powder is enclosed in a container made of a member having at least one surface capable of transmitting light from the light emitting element. It is characterized by performing adjustment for determining the diffused light output level by using it as a detection object.

  According to a seventh aspect of the present invention, in the reflected light detection method according to one of the first to sixth aspects, a variable resistor (VR) is used as an adjustment mechanism for determining the diffused light output level. It is said.

  The invention according to claim 8 is the reflected light detection method according to any one of claims 1 to 7, wherein the adjustment condition for determining the diffused light output level is determined by a storage unit provided in the sensor body. It is characterized by being registered.

  The invention according to claim 9 is characterized in that the reflected light detection method according to one of claims 1 to 8 is used in an image forming apparatus.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the reflected light detection method uses an adhesion amount of toner used for visible image processing of an electrostatic latent image as a detection target after sensitivity adjustment. It is characterized by being targeted.

According to an eleventh aspect of the present invention, in the image forming apparatus according to the ninth or tenth aspect, at least one of the reflected light detection methods can be used, and the toner adheres in the case of multiple use. The current value when the specularly reflected light output (Vsg) on the non-detection target surface becomes a predetermined value is Ireg, and the diffused light output (Vdif) when the detection target surface is covered with barium sulfate (BaSO ₄ ) is predetermined. When the current value when the value becomes Idif,
Idif / Ireg = 0.5-1.0
And a characteristic in which the sensitivity ratio in all reflected light detection methods is set within ± 20%.

  According to a twelfth aspect of the present invention, in the image forming apparatus according to the tenth or eleventh aspect, a toner having a weight average particle diameter of 8 μm or less is used.

  According to a thirteenth aspect of the present invention, in the image forming apparatus according to the tenth or eleventh aspect, a toner having an average circularity of 0.93 or more is used.

  According to the first to fourth aspects of the present invention, the standard detection object is provided for each of the specular reflection light and the diffuse reflection light, and therefore, when using an optical sensor that generates uneven sensitivity after shipment. However, it is possible to correct the variation in diffuse reflected light output. In particular, in the invention described in claim 2, it is possible to maintain stable prevention of sensitivity unevenness by not causing a change in reflectivity over time or over time. The generation of the diffuse reflected light component can be stabilized while the generation is kept low, and the diffuse reflected light component can be reliably obtained in the invention of claim 4.

  According to the fifth aspect of the present invention, since the regular reflectance is defined for the regular reflected light as the standard detection object, it is possible to improve the accuracy of the diffuse reflected light output calculated based on the regular reflected light output. Become.

  According to the sixth aspect of the invention, since the powder used as the standard detection object is used by being sealed in a light transmissive container, the diffuse reflected light from the powder is stable without being influenced by disturbance. And this state can be maintained.

  According to the seventh aspect of the present invention, since the variable resistor is used as the diffuse reflected light output level adjustment mechanism, the diffuse reflected light output level can be adjusted efficiently and the adjustment range can be selected without using a complicated configuration. It becomes.

  According to the eighth aspect of the present invention, the adjustment information in the optical sensor can be used by another control unit by registering the adjustment condition of the diffuse reflected light output level in the storage unit of the sensor body, and the hardware It becomes possible to make adjustments on the side unnecessary.

  According to the ninth and tenth aspects of the present invention, the specular reflection light output and the diffuse reflection light output based thereon can be obtained by using the standard detection object, so even if the sensitivity variation adjustment of the optical sensor is not appropriate. It is possible to optimize the diffuse reflected light output on the detection target surface by the optical sensor, and it is possible to improve the accuracy of toner adhesion amount detection.

  According to the eleventh aspect of the present invention, the output ratio between when the toner is not adhered to the detection target surface and when the surface is covered with barium sulfate is set to a predetermined relationship, thereby suppressing variations in the reflected light output between the sensors. In addition, it is possible to detect the toner adhesion amount with high accuracy, so that the image density adjustment system can be enhanced.

  According to the twelfth and thirteenth aspects of the present invention, the sensitivity of specular reflection light is prevented from being lowered by defining the particle diameter and circularity of the toner, and the difference is determined based on the normal shaman light output. It is possible to suppress the sensitivity variation of the diffuse reflected light output.

  The best mode for carrying out the present invention will be described below with reference to the illustrated embodiments.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus to which a reflected light detection method according to an embodiment of the present invention is applied. The image forming apparatus 20 shown in the figure is a color laser printer capable of writing with laser light corresponding to image information of different colors. However, the present invention is not limited to this, and a copying machine, a printing machine, a facsimile machine, and the like. Is also included as an image forming apparatus.
The image forming apparatus 20 shown in FIG. 1 forms a color image directly from a latent image carrier onto a recording sheet by superimposing and transferring a color separation image onto a recording sheet such as paper adsorbed on a transfer belt used as a transfer body. Is used.

In FIG. 1, an image forming apparatus 20 includes the following apparatuses.
Image forming devices 21M, 21C, 21Y, and 21BK that form images of respective colors according to the document image, transfer devices 22 that are arranged to face the image forming devices 21M, 21C, 21Y, and 21BK, and the respective image forming devices A manual feed tray 23 serving as a sheet supply means for supplying a recording sheet to a transfer area facing the devices 21M, 21C, 21Y, 21BK and the transfer device 22, a first paper feed cassette 24A provided in the paper feed device 24, and A second paper feed cassette 24B, and a registration roller 30 for supplying a recording sheet conveyed from the manual feed tray 23 or the paper feed cassettes 24, 24 in accordance with image forming timings by the image forming devices 21M, 21C, 21Y, 21BK. And a fixing device 1 for fixing the sheet-like medium after transfer in the transfer region.

  Although not described in detail, the fixing device 1 is configured to employ a belt fixing system in which a heated belt is disposed on the side facing the image. For this reason, the fixing device 1 is equipped with a heat source for heating the belt and a fixing roller and a pressure roller that constitute a nip portion that is a fixing region while nipping and conveying the sheet facing the belt, and the belt is fixed. It is configured to pass between the roller and the heat source and pass through the nip portion.

  The transfer device 22 corresponds to a belt device using a belt (hereinafter referred to as a transfer belt) 22A that is wound around a plurality of rollers as a transfer body, and the details will be described in FIG. Transfer bias means 22M, 22C, 22Y, and 22BK for applying a transfer bias are disposed at positions facing the photosensitive drum in the image forming apparatus, respectively, and the moving direction of the transfer belt 22A (the direction indicated by arrow A in FIG. 1). ), A suction bias means 31 for applying a suction bias for attracting the recording sheet to the transfer belt 22A prior to the transfer of the first color can contact the transfer belt 22A on the side where the first color is transferred. Is arranged.

The image forming apparatus 20 has a larger heat capacity than that of paper such as plain paper generally used for copying, 90K paper such as OHP sheets, cards, postcards, thick paper equivalent to about 100 g / m ² or more, and envelopes. Any so-called special sheet can be used as the recording sheet.

FIG. 2 is a schematic diagram schematically showing the configuration of the transfer device 22, in which the transfer belt 22 </ b> A is composed of a high-resistance endless single-layer belt having a volume resistivity of 10 ⁹ to 10 ¹¹ Ωcm. The material is PDVDF (polyvinylidene fluoride). The material used for the transfer belt 22 is not limited to the above-mentioned polyvinylidene fluoride, and a material that can obtain high glossiness can be selected. For example, polyimide (PI) in which carbon black is dispersed can be selected.
Polyimide is characterized by high durability, and when black carbon is dispersed in this material, so-called electronic conductive resistance characteristics with little environmental dependence and good temporal resistance stability can be obtained. The volume resistivity in this case is approximately 10 ⁸ to 10 ⁹ Ω · cm.
When carbon black is dispersed in polyimide, the transfer belt 22 becomes black, but the optical power is higher than that of the above-mentioned polyvinylidene fluoride, so that a so-called specular reflection state is obtained, and this reflection characteristic is utilized. Thus, the detection accuracy of the optical sensor can be prevented from being adversely affected. In addition, high durability leads to less wear, and there is also an advantage that there is little reduction in gloss over time. It should be noted that a transparent material that does not contain carbon can be used for the transfer belt 22 as the material of the transfer belt 22 when the optical sensor is used. In this case, a metal plate as a reflecting member is provided on the back side of the belt. The light reflected from the metal plate on the back side is detected by the optical sensor.
The transfer belt 22A is wound around support rollers 32 to 37 so as to be able to pass through transfer positions that are in contact with and face the photosensitive drums 25M, 25Y, 25C, and 25K located in the respective image forming units.
Among the supporting rollers, at a position facing the entrance roller 37 on the upstream side in the moving direction of the recording sheet on the stretched surface side of the transfer belt 22 </ b> A facing each photoconductor, a predetermined voltage from the power supply 38 is applied. The roller transfer belt 22 </ b> A as the bias unit 31 is disposed on the outer peripheral surface.
Of the supporting rollers, a roller denoted by reference numeral 33 is a driving roller that frictionally drives the transfer belt 22A, and is connected to a driving source (not shown) and can rotate in the direction indicated by the arrow.

  Transfer bias applying members 39Y, 39M, 39C, and 39K are provided at positions on the inner side of the belt that face each photoconductor across the transfer belt 22A so as to contact the slope of the transfer belt 22A. These bias applying members are bias rollers having a sponge or the like on the outer periphery, and a transfer bias is applied to the roller core from each transfer bias power source 40Y, 40M, 40C, 40K. Due to the action of the applied transfer bias, a transfer charge is applied to the transfer belt 22A, and a transfer electric field having a predetermined strength is formed between the transfer belt 22A and the surface of the photosensitive drum at each transfer position. Further, a backup roller 41 is provided in order to appropriately maintain the contact between the recording sheet and the photosensitive member in the transfer area and to obtain the best transfer nip.

The transfer bias applying members 39Y, 39M, and 39C and the backup roller 41 disposed in the vicinity thereof are integrally held by the swing bracket 42 so as to be rotatable, and can be rotated about the rotation shaft 42A. This rotation is clockwise when the cam 43 is rotated in the direction of the arrow.
The entrance roller 37 and the attracting bias means 31 composed of the roller are supported by the entrance roller bracket 44 and can be rotated clockwise from the state of FIG. 2 with the roller shaft 36A as the center of rotation.
A hole 42 </ b> B provided in the swing bracket 42 is engaged with a pin 44 </ b> A fixed to the entrance roller bracket 44, and rotates in conjunction with the rotation of the swing bracket 42. By the clockwise rotation of the brackets 42 and 44, the bias applying members 39Y, 39M, and 39C and the backup roller 41 disposed in the vicinity thereof are separated from the photoconductors 25Y, 25M, and 25C, and are attracted to the entrance roller 37. The biasing means 31 also moves downward. It is possible to avoid contact between the photoconductors 25Y, 25M, and 25C and the transfer belt 22A during black-only image formation.

  On the other hand, the transfer bias member 39K positioned on the downstream side in the moving direction of the recording sheet on the extended surface of the transfer belt 22A and the backup roller 41 adjacent to the transfer bias member 39K are formed into an exit bracket 45 that can be rotated about the rotation shaft of the exit roller 32 as a fulcrum. When the transfer device 22 is attached to and detached from the main body of the image forming apparatus, it can be rotated clockwise by operating a handle (not shown). The transfer bias member 39K and the backup bias member 39K can be rotated from the photosensitive member 25K for black image formation. The roller 41 can be separated.

In FIG. 1, a cleaning device 46 having a brush roller and a cleaning blade that can contact the transfer belt 22A is provided outside the transfer belt 22A mounted on the drive roller 33. Foreign matter such as adhering toner can be removed.
A roller 34 is provided downstream of the drive roller 33 in the moving direction of the transfer belt 22A in a direction to push the outer peripheral surface of the transfer belt 22A, and a winding angle of the transfer belt 22A around the drive roller 33 is secured. A roller 35 positioned in the loop of the transfer belt 22A further downstream than the roller 34 functions as a tension roller that applies a pressing force by a pressing member (spring) 47 to the transfer belt 22A to give a tension.
In the image forming apparatus 20 shown in FIG. 1, since the transfer device 22 extends obliquely, the space occupied by the transfer device 22 in the horizontal direction can be reduced.

In the image forming apparatus 20 having the above configuration, image formation is performed based on the following steps and conditions. In the following description, an image forming apparatus in which image formation is performed using magenta toner denoted by reference numeral 21M on behalf of each image forming apparatus will be described, but the same applies to other image forming apparatuses. Preface.
At the time of image formation, the photosensitive drum 25M is rotationally driven by a main motor (not shown), and is neutralized by an AC bias (DC component is zero) applied to the charging device 27M, and its surface potential is a predetermined potential (for example, approximately −50V). Is set to the reference potential.
Next, the photosensitive drum 25M is uniformly charged to a potential substantially equal to the DC component by applying a DC bias superimposed with an AC bias to the charging device 27M.
When the photosensitive drum 25M is uniformly charged, a writing process is executed. An image to be written is written for forming an electrostatic latent image using a writing device 29 in accordance with digital image information from a controller unit (not shown). That is, in the writing device 29, laser light from a laser light source that emits light based on a laser diode light emission signal binarized for each color corresponding to digital image information is converted into a cylinder lens (not shown), a polygon motor 29A, A photosensitive drum carrying an image for each color via an fθ lens (not shown), first to third mirrors, and a WTL lens. In this case, the photosensitive drum 25M is irradiated and irradiated for convenience. The surface potential on the surface of the photosensitive drum of the portion thus made becomes a predetermined potential (for example, approximately −50 V), and an electrostatic latent image corresponding to the image information is formed.

The electrostatic latent image formed on the photosensitive drum 25M is subjected to visible image processing by using a toner having a color complementary to the color separation color by the developing device 26M. In the developing process, an AC bias is applied to the developing sleeve. The toner (Q / M: -20 to -30 μC / g) is developed only in the image portion where the potential has been lowered by the irradiation of the writing light by applying a DC bias (-300 to -500 V) superposed on A toner image is formed.
Each color toner image that has undergone a visible image process in the development process is transferred to a recording sheet that is fed out with registration timing set by a registration roller 30, but the recording sheet is transferred to a roller before reaching the transfer belt 22A. The sheet is biased to the transfer belt 22A by application of a suction bias by the sheet suction bias means 31 configured as described above.
The recording sheet electrostatically attracted to the transfer belt 22A and conveyed and moved together with the transfer belt 22A is transferred bias members 39Y, 39M, and 39C provided in the transfer device 22 at a position facing the photosensitive drum in each image forming device. The toner image is electrostatically transferred from the photosensitive drum by applying a bias having a polarity opposite to that of the toner by 39K.

The recording sheet that has undergone the transfer process of each color is subjected to curvature separation using the curvature of the exit roller 32, and is conveyed toward the fixing device 1 (see FIG. 1), and passes through a fixing nip constituted by a fixing belt and a pressure roller. By passing, the toner image is fixed on the transfer paper. Thereafter, in the case of single-sided printing, the first paper discharge direction B toward the in-body paper discharge tray 20A (see FIG. 1) or external paper discharge. The paper is discharged by being switched by the discharge switching claw 48 in any one of the second paper discharge directions C toward the tray.
When the first paper discharge direction B is selected, the recording sheets are stacked in a face-down state with the image surface facing downward, and when the second paper discharge direction C is selected, the recording sheet is installed on the outer casing, although not shown. The sheet is conveyed toward a post-processing device (such as a sorter or a binding device) or a recirculation path for image formation on both sides through a switchback.

In the color laser printer according to the present embodiment, in addition to the image forming mode as described above, a process control operation (hereinafter referred to as a process controller) is performed in order to optimize the image density of each color when the power is turned on or after a predetermined number of sheets have passed. (Abbreviated as operation).
In this process control operation, a density detection patch (hereinafter abbreviated as a P pattern) corresponding to a standard detection object having a gradation pattern for each color toner, charging bias and development bias at appropriate timings. Are sequentially switched to form an image on the transfer belt, and the output voltage of these P patterns is shown in the vicinity of one of the driving rollers of the transfer belt 22A, in FIGS. Detected by a concentration detection sensor (hereinafter abbreviated as P sensor) 50 located outside the position where 22A has passed, the output voltage is converted by an adhesion amount conversion algorithm (powder adhesion amount conversion method) described later. Then, the current development capability (development γ, Vk) is calculated, and the development bias value and the toner density control target value are changed based on the calculated values. It is carried out. The density detection sensor, so-called P sensor 50, is not limited to the position targeting the transfer belt 22A described above, but can be provided at a position targeting each photoconductor.

  The P sensor 50 is a member used to execute the reflected light detection method according to the present embodiment, and as shown in FIG. 3, the LED 51 incorporated in the element holder 50A, the regular reflection light receiving element 52, and the diffuse reflection. A light receiving element 53 is provided, and a reflection component of light emitted to a density detection pattern (toner patch) 55 formed on the detection target surface 54 is detected by each light receiving element. Note that a phototransistor or a photodiode is used as the light receiving element.

In this embodiment, an algorithm of a toner adhesion amount conversion method according to the following procedure is used, and the diffused light output is converted into a toner adhesion amount value based on this algorithm. This procedure is intended for the processing with the transfer belt 22A shown in FIG. 1, and the content of this procedure is Japanese Patent Application No. 2003-307445 (August 29, 2003) filed earlier by the present applicant. Details are described in Japanese Patent Application No. 0305138). In this embodiment, the toner patch formed on the transfer belt 22A is targeted. However, the same procedure as in the case of the transfer belt 22A is used by forming a toner patch of a color that is a reference for density control in each photoconductor. Of course it is possible.
As the above procedure,
(1) Sampling the regular reflection light output and diffuse reflection light output of the gradation pattern. (2) (2) Only the “regular reflection light component” is extracted by decomposing the specular reflection light output into “regular reflection light component” and “diffuse reflection light component”.
(3) The “diffuse light component from the toner” is extracted by removing the “diffuse reflection light component from the belt background” from the diffuse reflection light output.
(4) A deposition amount range in which each output is linear with respect to the deposition amount by using a linear relationship with the deposition amount of two output conversion values that are independent (intersect) obtained from (2) and (3). , The diffuse reflected light output conversion value of a certain specular reflected light output conversion value (or adhesion amount) is corrected so that the diffuse reflected light output conversion value has a certain value, whereby the diffuse reflected light output relative to the adhesion amount ( Correction value) is uniquely determined.
(5) The adhesion amount conversion process is performed based on the relationship between the “adhesion amount” and the “diffuse reflection light output correction value” obtained in advance.

Regarding the sensitivity correction of the diffuse reflection light output conversion value listed in (4), the following procedure and means are used in this embodiment.
(4-1) The current (If) of the LED 51 (see FIG. 3) is set so that the regular reflected light output becomes a predetermined voltage (for example, 4 V) by the standard object for regular reflected light.
(4-2) At the current (If) or If × α (α: arbitrary), the sensor adjustment mechanism allows the diffuse reflected light output to be a predetermined voltage by the diffuse reflected light standard detected object, Adjust the level of the diffuse output value.
In this embodiment, the sensor adjustment mechanism uses a VR (variable resistor) provided in the diffusion output circuit. As a result, the adjustment work can be easily performed, and various adjustment widths can be selected by the resistance, so that it is possible to cope with various levels of output adjustment.

(4-3) In this embodiment, barium sulfate (BaSO ₄ ) is used as a standard detection object used as a reference for adjusting the sensitivity of the diffuse reflected light output.
Conventionally, Munsell chart paper has been used as the standard object for diffuse reflected light, but the paper is not only low in physical strength, but is always affected by the environment such as moisture absorption and deterioration over time. It is difficult to maintain a constant reflectivity. Therefore, when such paper is used, the reflectance of the object to be detected also varies, and the diffuse reflected light output after sensitivity adjustment also varies.
In this embodiment, as is well known for use in paints and X-ray contrast media, it is harmless to the human body and relatively easily available, and is an optimal diffusion for use as a calibration member for optical instruments. In addition to being a representative substance to be reflected, barium sulfate, which is a so-called barium sulfate with little change in environment and time, is used as a standard object to be detected.

(4-3) When the present inventor considered the case where barium sulfate (BaSO ₄ ) was used as a standard detection object, a sufficient diffused reflected light output could be obtained in a solidified powder. As a result, it has been found that the sensitivity of the P sensor 50 is effective. It was also confirmed that when the powder was hardened, it was important to make the layer thickness sufficiently thick so that only reflected light from the barium sulfate particles was used. In other words, when the layer thickness is thin, there is an influence of reflected light from the surface of the transfer belt serving as the detection target surface or the background portion of the photoreceptor, and the process of distinguishing from the reflected light from the barium sulfate itself becomes complicated.
By defining the layer thickness as described above, a stable diffuse reflected light output can be obtained without changing the reflectance without being influenced by environmental conditions over time.

Further, barium sulfate as a standard detection object may cause regular reflection on the particle surface when the particle size is large, which may cause unevenness in the diffuse reflected light output value.
Therefore, in this embodiment, only powder having a particle size of 500 μm or less is used in order to suppress or ignore regular reflection on the particle surface. Therefore, when it is recognized that no specular reflection component is generated, not only barium sulfate having the above particle diameter but also other substances can be used.

(4-4) The P sensor 50 for the powder used as the standard detection object has a wavelength at the LED 51 in consideration that the detection object that obtains the diffuse reflected light output is a color toner. The region is set to an infrared light region (800 nm to 1100 nm) that is not visible. The present inventor conducted an experiment using the above wavelength region for the above powder, and confirmed that a stable diffuse reflected light output can be obtained if the diffuse reflectance is 90% or more in the above wavelength region. .

(4-5) The powder such as barium sulfate used as the standard detection object is preferably used in a state where the powder itself is hardened so that the reflectance does not change. It is conceivable to produce only by compression molding without using a solvent or an adhesive.
However, it has been found that when compression molding, it is weak against impact and fragile.
Therefore, in this embodiment, the powder is enclosed in a container using a material capable of transmitting light, for example, glass or the like, on the incident light incident side.
Thereby, when glass is used, the light from the LED 51 that passes through the glass is diffusely reflected by the powder, and the reflected light passes through the glass and enters the diffuse reflection light receiving element 53 (see FIG. 3). As a result of experiments using this configuration, the present inventor has confirmed that the influence of the glass on the diffuse reflected light output can be suppressed and a pure diffuse reflected light output can be obtained.
By using such a powder storage structure, it is possible to maintain a constant reflectivity by preventing damage to the powder used as a standard object and a change in reflectivity, and once producing a container. It is possible to prevent the change with time.

(4-6) On the other hand, apart from the standard detected object used for adjusting the diffuse reflected light output described above, the standard detected object used for adjusting the regular reflected light output, based on the following consideration, As in the case where the surface of the transfer belt or the photoreceptor background is formed, a substance having a reflectance of 3 to 15%, preferably 5 to 10% is used.
In other words, the specular reflection light output changes depending on the state change of the surface property (glossiness, surface roughness, etc.) on the surface to be detected. It becomes important, and the influence on the diffuse reflected light output adjusted with reference to the regular reflected light output is also increased.
For this reason, if the specular reflection light output at the adjustment stage is different from the specular reflection light output at the practical use stage, the diffuse reflection light output may vary.
Therefore, the standard detection object used for adjusting the regular reflection light output so as not to cause a variation in the diffuse reflection light output may have a level equivalent to the regular reflectance on the surface of the transfer belt or the photoreceptor background. As a result, the reflectance described above is set.

In the optical sensor according to this example, the sensitivity shown in FIGS. 4 and 5 is obtained when the sensitivity adjustment in the P sensor is performed based on the above configuration.
FIG. 4 shows the relationship between the diffuse reflected light output from the P sensor and the toner adhesion amount for 50 P sensors. FIG. 5 shows the procedures and means of (4-1) to (4-6). It is the adjustment result by the algorithm using the procedure of (1)-(5) using. Incidentally, FIGS. 6 and 7 show FIGS. 4 and 4 in the case of using the procedures listed in (1) to (5) without using the procedures and means listed in (4-1) to (4-6). FIG. 6 is a diagram illustrating a result of parameters corresponding to 5;
As is clear from FIGS. 4 and 5, the variation in the diffuse reflection light output value is reduced compared to the results shown in FIGS. 6 and 7 (the relationship of L <L0 in FIGS. 4 and 6), and The diffuse reflected light output value after sensitivity adjustment is also optimized (relationship of L ′ <L0 ′ in FIGS. 5 and 7). The reason for this is that some of the P sensors for which the results shown in FIGS. 6 and 7 are obtained are misadjusted. As a result, there are P sensors that cannot be corrected by the algorithm. I understand.
From such a result, according to the present embodiment, it is possible to improve the accuracy of the image density adjustment by appropriately adjusting the sensitivity of the diffuse reflected light output value.
The results in FIGS. 4 to 7 do not cover the entire wavelength region of the LED 51, but mainly show the upper and lower limits in the results.

In the present embodiment, for example, the current value when the regular reflection light output Vsg of the photoconductor background becomes a predetermined value (4 V) in each sensor when the sensitivity adjustment described above is performed is Ireg. When the current value Idif when the diffuse reflected light output Vdif when the surface to be detected is covered with barium sulfate (BaSO ₄ ) is a predetermined value (4V) is assumed, the ratio (Idif / Ireg) is 0. It was confirmed to be 5 to 1.0. Further, when the sensitivity was investigated for the plurality of P sensors, the result that the sensitivity ratio was within ± 20% (output value variation was within ± 20%) was obtained. The variation in diffuse reflection light output should be as small as possible. However, with this level of variation, the algorithm can confirm that the difference from the actual toner adhesion amount is extremely small, and performs high-precision image density control. In the above, it is desirable to use a P sensor that can adjust the diffuse reflected light output value that falls within such a range.

  Although it is assumed that sensitivity adjustment with the P sensor is performed individually for each P sensor, a memory chip is provided in the sensor itself as means for eliminating the complexity of the adjustment operation on the hardware side. In this memory chip, the adjustment process conditions (current value and voltage value at a predetermined object to be detected) for each P sensor are registered and stored in advance, and the toner adhesion amount obtained experimentally as a mathematical expression or table data in advance is stored. The diffuse reflected light output value after sensitivity correction is converted into a conversion table. As a result, the sensitivity correction of the P sensor can be performed automatically and with high accuracy on the software side, not on the adjustment operation on the hardware side. As a result, the adjustment work for each sensor becomes unnecessary, the labor and time burden required for the adjustment process can be reduced, and the cost can be reduced.

On the other hand, the P sensor that performs sensitivity adjustment in the present embodiment uses diffuse reflected light even when the toner used for development has a weight average particle diameter of 8 μm or less and an average circularity of 0.93 or more. It was confirmed that output sensitivity correction was performed with high accuracy.
In other words, the toner used when forming a full-color image tends to have a small particle size in order to exhibit characteristics such as gradation and character reproducibility. For this reason, as the particle size is reduced, the coverage with the toner increases, and as a result, the sensitivity of the regular reflection light output of the P sensor tends to decrease (influence of shadow factor). However, in this embodiment, the sensitivity adjustment when using the standard detection object does not cause deterioration in accuracy as described above, so that the sensitivity is hardly affected. Therefore, by using the P sensor according to the present embodiment, the accuracy of image density control can be prevented from being lowered.

1 is a schematic front view of a color laser printer as an image forming apparatus using an optical sensor according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a configuration of a transfer device used in the image forming apparatus shown in FIG. 1. It is a block diagram of the optical detection means of the type which detects a regular reflection light and diffuse reflection light simultaneously used as a structure of the optical sensor by a present Example. It is a diagram which shows the relationship between the toner adhesion amount at the time of using the optical sensor by a present Example, and a diffuse reflected light output value. It is a diagram which shows the adjustment result of the diffuse reflected light output value performed using the optical sensor by a present Example. It is a diagram which shows the relationship between the toner adhesion amount and a diffuse reflected light output value at the time of using the optical sensor of a different structure from the optical sensor by a present Example. It is a diagram which shows the adjustment result of the diffuse reflected light output performed using the optical sensor shown in FIG.

Explanation of symbols

20 Image forming apparatus 50 Optical sensor 51 LED
52 Regular Reflection Light Receiving Element 53 Diffuse Reflection Light Receiving Element 54 Detection Target Surface 55 Density Detection Patch

Claims (13)

A reflected light detection method using one light emitting element and at least two light receiving elements, wherein the reflected light output and the diffuse reflected light output are subjected to arithmetic processing, and the corrected output value is corrected to a predetermined level. In a reflected light detection method using an optical sensor having a mechanism,
The specularly reflected light standard detection object is used as the specular reflection light, and the diffused light standard detection object is used as the diffused light. A reflected light detection method, wherein an adjustment is made to determine a diffused light output level obtained by a standard detected object for diffused light as a reference. The reflected light detection method according to claim 1,
A reflected light detection method, wherein an adjustment for determining the diffused light output level is performed by using an object that does not cause a change in reflectance over time or the environment as the standard detection object. The reflected light detection method according to claim 1,
The reflected light detection method, wherein an adjustment for determining the diffused light output level is performed by using a powder having a particle size of 500 μm or less as the target object for the diffused light. The reflected light detection method according to claim 1,
The standard object to be detected is adjusted to determine the diffused light output level by using a powder having a diffuse reflectance of 90% or more in an LED wavelength region of 800 to 1100 nm as a target. Reflected light detection method. The reflected light detection method according to claim 1,
For determining the diffused light output level by using a substance having a regular reflectance on the surface of the material of 3 to 15%, preferably 5 to 10%, for the regular reflection light among the standard detection objects. A reflected light detection method, wherein adjustment is performed. The reflected light detection method according to claim 3 or 4,
Adjustment is made to determine the diffused light output level by using the powder as a standard detection object in a state where at least one surface is sealed in a container made of a member capable of transmitting light from a light emitting element. Reflected light detection method. In the reflected light detection method according to any one of claims 1 to 6,
A reflected light detection method, wherein a variable resistor (VR) is used as an adjustment mechanism for determining a diffused light output level. In the reflected light detection method according to one of claims 1 to 7,
The reflected light detection method, wherein the adjustment condition for determining the diffused light output level is a configuration registered by a storage unit equipped in the sensor body.   An image forming apparatus using the reflected light detection method according to claim 1. The image forming apparatus according to claim 9.
The reflected light detection method is directed to an adhesion amount of toner used for visible image processing of an electrostatic latent image as a detection target after sensitivity adjustment using a standard detection object. The image forming apparatus according to claim 9 or 10, wherein:
At least one of the reflected light detection methods can be used. When a plurality of reflected light detection methods are used, the regular reflected light output (Vsg) on the detection target surface to which the toner does not adhere becomes a predetermined value. The current value when the diffused light output (Vdif) when the detection target surface is covered with barium sulfate (BaSO ₄ ) becomes a predetermined value is Idif,
Idif / Ireg = 0.5-1.0
The image forming apparatus is characterized in that the characteristics are set such that the sensitivity ratio in all reflected light detection methods is within ± 20%.   12. The image forming apparatus according to claim 10, wherein a toner having a weight average particle diameter of 8 μm or less is used. 12. The image forming apparatus according to claim 10, wherein a toner having an average circularity of 0.93 or more is used.

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