JP2000267369A - Density measuring device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately correct the fluctuation of output with a simple means without being restricted by the kind of a photosensor to be used by providing a correction means outputting the output value of a toner image at the time of measuring density by the photosensor as a specified correction value by using the output values of two correction reference points. SOLUTION: An output correction circuit 50 is incorporated in a sensor controller 5 so as to prevent a situation that the output value from the photosensor 4 is fluctuated and an error is caused in the measurement of the density due to the fluctuation. Namely, the circuit 50 performs output correction processing that the output value Vp concerning a toner image for control Tpatch measured by the photosensor 4 at the time of detecting the density is corrected by a correction expression, Vn= (V20-V10)(Vp-V11)/(V22-V11))+V10 and calculated as the output value Vn, In the expression, V10 and V20 express the output values in the early stage of the 1st and the 2nd correction reference points and V11 and V22 express the output values at the time of measuring the density of the 1st and the 2nd correction reference points, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a density measuring apparatus for optically measuring the density of a toner image formed in an image forming apparatus such as a copying machine or a printer by a photosensor having a light emitting element and a light receiving element. In particular, the present invention relates to a density measurement device capable of accurately correcting output fluctuation of the photosensor.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine or a printer using an electrophotographic system, a toner image is generally formed on an image carrier such as a photoconductor, and the toner image is finally formed on a recording paper or the like. Then, the image is formed by transferring the image onto the fixing device. In such an image forming apparatus, since it is necessary to maintain that the toner image is properly and stably formed in accordance with a preset image forming condition, for example, a control image is formed on an image carrier. Toner image (patch)
And a density measuring device for optically measuring the density of the toner image with a photo sensor, and feeding back the measurement result of the density measuring device to control means for controlling image forming conditions to form a required image. It is configured to change the setting for the condition.

The photosensor includes a light-emitting element such as a light-emitting diode and a light-receiving element such as a photodiode, and irradiates light from the light-emitting element to a control toner image on an image carrier, and transmits the light at that time. In many cases, the density of a control toner image is measured from an output value obtained by receiving light or reflected light (specular reflection light or diffuse reflection light) by a light receiving element. Among them, a photo sensor that measures reflected light from a toner image includes a specular reflection sensor configured to receive specularly reflected light and a diffuse reflection type sensor configured to receive diffusely reflected light. There is. In general, a regular reflection type sensor is used for measuring the density of a toner image composed of black toner or color toner, and a diffuse reflection type sensor is used for measuring the density of a toner image composed of color toner other than black.

[0004]

However, in such a density measuring apparatus in an image forming apparatus, the sensitivity of the light emitting element and the light receiving element of the photo sensor is changed due to environmental changes such as temperature, the deterioration of the element itself over time, and the toner. And the output value of the photosensor fluctuates due to dirt or scratches on the surface of the image carrier on which the toner image is formed. However, there is a problem that accurate measurement of density becomes difficult, and accurate image forming conditions cannot be controlled.

[0005] Such output fluctuations of the photosensor are roughly classified into the following three types. In practice, these types of fluctuations often occur in combination. The smaller the density of the toner image, the larger the fluctuation (gain fluctuation type) (FIG. 14). The cause of the fluctuation in this case is
Mainly members on which toner images are formed (drums, belts, etc.)
The presence of dirt or scratches on the surface. The larger the sensor output, the larger the fluctuation (gain fluctuation type) (FIG. 14). In this case, the cause of the fluctuation is mainly contamination of the light-emitting or light-receiving element, fluctuation of the light amount of the light-emitting element, or the like. The sensor output fluctuates at almost the same level as a whole (offset fluctuation type) (FIG. 14). The cause of the variation in this case is mainly a variation in the ambient temperature of the photo sensor. The solid line in FIG. 14 indicates the normal characteristic in the initial stage, and the dotted line indicates the current characteristic that has fluctuated or the characteristic after combination (the same applies to output characteristic diagrams that show fluctuations in output values other than this figure).

On the other hand, the following various countermeasures have been proposed in the past to solve the output fluctuation of the photosensor in the density measuring device, but all of them have some problems, and they have been sufficiently satisfactory. I couldn't do it. Further, in particular, when output fluctuations of the above-mentioned types (1) to (4) occur in combination, there is no device capable of accurately correcting the output fluctuation.

For example, Japanese Patent Application Laid-Open No. 4-14060 discloses an output value V of a photo sensor when a toner image is detected.
p is the output value Vc of the surface (in a clean state without a toner image) of an image carrier such as a photoconductor on which the toner image is formed.
By dividing the ratio (Vp / Vc) by a reference value and comparing the reference value with the output value Vp to correct the image forming process conditions, output fluctuations due to dirt and the like are eliminated to reduce the output value. Stabilizing means are shown.

However, in this conventional example, when a regular reflection type photo sensor is used to detect a toner image on a member such as a belt having a low reflectance, the sensor output value Vc from the member is substantially zero. As a result, it is difficult to use the ratio (Vp / Vc), and there is a problem that output fluctuation cannot be corrected. Further, when a diffuse reflection type photosensor is used, the level of diffuse reflection light from a member forming a toner image is low, so that the sensor output value Vc from that member becomes almost zero. There is a problem that it is not possible to detect an output fluctuation such as a type and to correct the output fluctuation. Furthermore, the above-mentioned type ~
In the case where the output fluctuations occur in combination, there is also a problem that the output fluctuations cannot be accurately corrected only by comparing the output value Vp at the time of toner image detection with the ratio (Vp / Vc). .

Japanese Patent Application Laid-Open No. Hei 4-260077 discloses a means for periodically cleaning the surface of a photosensor with a cleaning member to remove dirt on the sensor surface. However, in the case of this conventional example, although it is possible to cope with the output fluctuation caused by the above-mentioned type of sensor contamination, the fluctuation of the light amount of the light emitting element and the fluctuation of other types occur, and the fluctuation of each type. However, there is a problem that the output fluctuations cannot be corrected when the errors occur in combination.

Further, Japanese Utility Model Publication No. 8-679 discloses that the light quantity of a light emitting element is detected by a monitor means and the reference light quantity of the light emitting element is adjusted by a light quantity adjusting means so as to eliminate the deviation between the detection result and the reference light emission quantity. After adjusting the light receiving element, the light receiving signal at the light receiving element is corrected so as to eliminate the deviation between the result of detection of the light reflected from the toner image by the adjusted light from the light emitting element by the light receiving element and the reference light receiving amount. By
There is disclosed a density detecting device capable of accurately detecting a density without being affected by deterioration of a light emitting element and deterioration of a photosensitive material. However, in the case of this conventional example, although it is possible to correct the light amount fluctuation of the light emitting element of the type described above, there is a problem that the output fluctuation of the type or the like cannot be corrected.

Therefore, an object of the present invention is to provide a simple means for an output fluctuation of any of the above-mentioned types 1 to 3 or a combined output fluctuation without being limited by the type of a photosensor to be used. Another object of the present invention is to provide a density measuring apparatus of an image forming apparatus capable of performing accurate density measurement without such output fluctuation.

[0012]

SUMMARY OF THE INVENTION The present invention, which can achieve the above-mentioned object, is directed to irradiating a toner image formed in an image forming apparatus with light from a light emitting element and reflecting light reflected by the toner image or the reflected light. A density measuring device for measuring the density of the toner image based on the output value of the light receiving element of the photo sensor, the photo sensor being provided with a photo sensor for receiving transmitted light passing through the toner image by a light receiving element; 1
Using the output values of the correction reference point and the second correction reference point,
Output correction means for outputting the output value Vp of the toner image at the time of measuring the density of the photosensor as an output value Vn corrected by the following correction formula: Vn = ｛(V20−V10) (Vp−V11) / (V22−V1)
1)｝ + V10 (where V10 is the output value of the first correction reference point in the initial stage, V20 is the output value of the second correction reference point in the initial stage, and V11 is the density measurement of the first correction reference point. , And V22 indicates the output value at the time of measuring the density of the second correction reference point).

Here, the correction formula in the output correction means will be described.

First, among the fluctuations of each type of the photosensor in the above-described density measuring apparatus, the offset fluctuations such as the above-mentioned fluctuations are irrespective of the difference between the specular reflection type and the diffuse reflection type. By uniformly subtracting or adding the value obtained from the sensor output value of the toner image, it is possible to correct such offset type fluctuation.

Next, regarding the gain-type fluctuations of the above-mentioned types, in the gain-type fluctuations in the regular reflection type sensor, as shown in FIG. Since it is common in the area where the amount of toner is small, the ratio between the output value in the state where the amount of toner is small or not at all and the sensor output value of the toner image can be determined to some extent as in the prior art described above. Can be corrected.

On the other hand, in the case of the gain-type fluctuation in the diffuse reflection type sensor, an area where each type of output fluctuation largely occurs is defined as an area where the amount of toner is small or an area where the amount of toner is large. Because of the difference, the correction cannot be performed simply by taking the ratio between the output value in the state where the toner amount is small or not at all and the sensor output value of the toner image as in the above-described conventional technology.

However, when the two output fluctuations of the type in the diffuse reflection type sensor are combined, as shown in the lower part of FIG. 15, similar to the case of combining the gain-type fluctuation of the type and the offset-type fluctuation of the type. This results in a variation result indicating the characteristic.

Therefore, the present inventors pay attention to the output fluctuation in the case of the synthesis, and perform correction of the offset fluctuation and correction of the gain fluctuation, respectively. It has been found that the output value of the toner image can be corrected to an accurate value without fluctuation even when the fluctuations occur individually or when the fluctuations occur in combination. The offset-type variation can be corrected by calculating the difference between the output value at the initial stage at a specific measurement point and the output value at the time of measuring the density (current). It has also been found that the correction of the minute may be performed by calculating the increase / decrease ratio between the output value at the initial stage at another specific measurement point and the output value at the time of measuring the concentration.

That is, as shown in FIG. 12, when the output fluctuations of the above-mentioned types (1) and (2) occur in combination in the diffuse reflection type sensor, when all of the output fluctuations are combined, finally, the bottom of FIG. A characteristic line (a two-dot chain line) as shown in the figure, the output fluctuation indicated by such a characteristic line is subjected to “correction for offset-type fluctuation” and “correction for gain-type fluctuation” in this order, and the overall output is obtained. The case where the correction is performed will be specifically described as an example.

First, as shown in FIG. 13A, a first correction reference point G1 for correcting the offset-type variation is set to, for example, an image carrier (a photosensitive drum or a belt, an intermediate transfer belt or a drum, Transport belt, drum, recording paper, etc.)
Is set to, for example, a measurement point of a specific toner amount. The output value of the first correction reference point G1 at the initial stage is V10, the output value of the second correction reference point G2 at the initial stage is V11, and the output value of the second correction reference point G2 at the initial stage is V20. The output value is V22. Further, the output value Vp at the time of measuring the density of the toner image
In this case, the normal output value, that is, the corrected output value is defined as Vn.

First, an offset-type variation in the synthesized characteristic line is performed based on the first correction reference point G1. In this case, as shown in FIG. 13B, the characteristic line is shifted toward the output value V10 by the difference (V11−V10) between the current output value V11 at the first correction reference point G1 and the output value V10 in its initial stage. The dotted line shifted in parallel becomes the characteristic line after the offset correction. Assuming that the output value of the toner image after the offset correction is Vp1, the output value Vp1 after the offset correction is expressed by the following equation (a). Vp1 = Vp- (V11-V10) (a)

Next, the gain-type variation in the characteristic line after the offset correction is performed based on the second correction reference point G2. In this case, as shown in FIG. 13C, the output value of the second correction reference point G2 after the offset correction is V
Assuming that 21, the output value of the toner image after the gain correction, that is, the normal output value Vn is expressed by the following equation (b). Vn = {(V20-V10) (Vp1-V10) / (V21-V10)} + V10 (b) From FIG. 13B, V21 is represented by the following equation (c). V21 = (V22−V11) + V10 (c)

Therefore, the corrected toner image output value Vn
Is expressed by substituting the above equations (a) and (c) into the above equation (b) and deforming, as in the correction equation described above. As a result, the changed output value V of the current toner image
By calculating p by applying it to the above-mentioned correction formula,
It can be seen that the output value is obtained as the output value Vn corrected to a normal output value. The correction equation corrects the gain-type variation in the combined characteristic line based on the second correction reference point G2, and then corrects the offset-type variation in the gain-corrected characteristic line by the first correction. In the case where each calculation formula is set up and obtained in a procedure of performing correction based on the reference point G1, it is derived in substantially the same manner.

The first correction reference point and the second correction reference point in the output correction means may be measurement points at which an output value different from the output value (Vp, Vn) of the toner image is obtained. It is not particularly limited and can be set arbitrarily. Incidentally, as the first and second correction reference points, one of the first and second correction reference points is set so as to have a content suitable as a reference (measurement) point for offset correction, and the other is set as a reference (measurement) point for gain correction. It is good to set the one with suitable contents. The output values V10 and V20 of the first and second correction reference points in the initial stage are values when the density measuring device (photosensor) is mounted on the image forming apparatus and set up. Any time other than the above-mentioned setup may be used as long as the initial characteristics (characteristics that can be used as references) of the light emitting element and the light receiving element can be measured.

For example, as the output value of the first correction reference point or the second correction reference point, an output value of the light receiving element when the light emitting element for irradiating the toner image is turned off, or a toner image is formed. The output value of the light receiving element when light is emitted from the light emitting element to the surface of the member can be used. In addition, when a reference reflection surface is provided inside or outside the photosensor, the output value of the light receiving element when light is emitted from the light emitting element to the reference reflection surface, or
If the photo sensor is provided with a light receiving element that monitors the amount of light emitted from the light emitting element that irradiates the toner image with light,
The output value of the light receiving element for monitoring can be used. The output values of the first correction reference point or the second correction reference point can be used by appropriately combining these exemplified output values.

The photosensor in the density measuring apparatus provided with such an output correction means is most effective for a diffuse reflection type photosensor (including a structure used in combination with a regular reflection type photosensor). However, a regular reflection type photosensor or a light transmission type photosensor may be used.
Further, in this density measuring device, the member (support) on which the toner image is formed is not particularly limited as long as the toner image to be measured can be optically measured by a photo sensor. As the member, for example, a photosensitive drum or a belt, an intermediate transfer belt or a drum, a sheet conveying belt or a drum, a recording sheet, and the like can be applied.

[0027]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

[First Embodiment] FIG. 1 is a schematic diagram of a concentration measuring apparatus according to one embodiment of the present invention. This density measuring apparatus 1 is an image carrier (mainly an intermediate transfer belt or drum, a paper transport belt or drum, etc.) 2 in a color image forming apparatus such as a copying machine or a printer using an electrophotographic system.
Image (patch) T for image forming condition control formed on
_{It comprises} a photo sensor 4 for optically detecting the density of the _patch , and a sensor controller 5 for controlling the operation and output signals of the photo sensor 4. The photo sensor 4 is disposed so as to face the surface of the image carrier 2 on which the toner image T _patch is formed.

The photosensor 4 includes a light-emitting element 41 for regular reflection and a light-emitting element 42 for diffuse reflection, such as a light-emitting diode, and irradiation light emitted from these two light-emitting elements 41 and 42, respectively. Upper toner image T
_A common light receiving element 43 composed of a photodiode or the like capable of receiving both of the light reflected by the _patch , and a light-shielding sensor holder (support) that accommodates, installs, and supports the light emitting elements 41, 42, and the light receiving element 43. 44 constitutes the main part.

In the photosensor 4, the irradiation light H ₁ emitted from the light emitting element 41 for regular reflection (the dashed line with an arrow in the figure indicates the optical axis and traveling direction of each light. The same applies hereinafter). ) Can be used as a “specular reflection sensor” by receiving the regular reflection light H ₂ when reflected by the toner image T _patch by the shared light receiving element 43, and also emit light for diffuse reflection. the irradiation light H ₃ emitted from the element 42 is also used as the "diffuse reflection type sensor" by received by the light receiving element 43 of the shared predetermined diffusion reflection light H ₄ when it is reflected by the toner image T _`patch Is available. In the drawing, reference numeral 45a denotes a light-emitting optical path of the light-emitting element 41, 45b denotes a light-emitting optical path of the light-emitting element 42, 45c denotes a light-entering optical path of the light-receiving element 43, and 46 denotes an opening of each of the optical paths 45a to 45c formed in the holder 44. It is a light-transmitting dustproof member that covers and prevents foreign substances such as toner from entering each optical path.

On the other hand, the sensor controller 5 basically controls the light emitting operation of each of the light emitting elements 41 and 42,
A process of correcting an output value by light reception of the light receiving element 43 according to a preset control program as necessary, and controlling an image forming process condition of the image forming apparatus using the corrected output value as a sensor detection result. The information is transmitted to a central control unit or the like for performing the operation.

The sensor controller 5 includes:
In order to prevent the output value of the photosensor 4 from fluctuating as described above and causing an error in the density measurement due to the fluctuation, a predetermined output correction process is performed on the output value of the photosensor 4 as shown in FIG. An output correction circuit 50 is provided. That is, in this output correction circuit 50, FIG.
As shown, for example, the output value Vp relating to the control toner image T _patch measured by the photo sensor 4 at the time of density detection.
Is corrected by the following correction formula, and an output correction process of calculating an output value Vn is performed. Vn = ｛(V20−V10) (Vp−V11) / (V22−V1)
1)｝ + V10

In this correction equation, V10 is the output value of the light-receiving element 43 in the initial stage when the light-emitting elements 41 and 42, which are the first correction reference points G1, are turned off (in this embodiment, during setup), and V20 is This is the output value of the light receiving element 43 in the initial stage of the surface of the image carrier 2 (the surface where the toner image T _patch is not formed), which is the second correction reference point G2. In the same equation, V11 is the light emitting element 4
The output value of the light emitting element 43 at the time of density measurement when the light sources 1 and 42 are turned off, and V22 is the surface of the image carrier 2 (toner image T
_This is the output value of the light emitting element 43 when measuring the density of the surface (when no _patch is formed).

In the sensor controller 5 having the output correction circuit 50, the output values V10 and V20 in the initial stage used in the correction formula are measured at the time of setting up the photosensor 4, and the respective values are output, for example. The data is stored in a storage unit such as the correction circuit 50. That is, the output value V10 is obtained by measuring the output value of the light receiving element 43 in a state where the light emitting elements 41 and 42 are turned off at the time of setup, and the output value V20 is also determined by the toner image T at the time of setup.
_A light emitting element 4 is provided on the surface of the image carrier 2 on which no _patch is formed.
From 2 (41), the output value of the light receiving element 43 in a state where light is irradiated is obtained by measuring in advance. Further, the measurement of the output values V11 and V22 at the time of the density measurement used in the correction formula is executed immediately before the sensor measurement of the toner image T _patch . Here, the measurement timing of the output value V11, V22 is the same time as the sensor measurement of the toner image T _`patch is preferred, but may be immediately followed by the sensor measured from this point of view, of the toner image T _{pa tch} If the timing immediately before or immediately after the sensor measurement is difficult, another timing close to the sensor measurement time of the toner image _Tpatch may be used (for example, a normal image forming operation close to the sensor measurement time). (Before and after (job), when the power of the image forming apparatus body is turned on, or at another predetermined time).

The density measurement by such a density measuring apparatus is performed at a preset time (for example, when the power of the image forming apparatus main body is turned on, when a specified time has come, or when the specified number of images has been reached, etc.). ). Further, the control toner image T _patch formed at the time of the density measurement is formed on the image carrier 2 as a single-color toner image of each color having a predetermined density and dimensions by an image forming system of the image forming apparatus. The detection is performed when the image carrier 2 moves just below the photosensor 4 as the image carrier 2 moves. Incidentally, in this embodiment, the toner image T _patch is mainly formed of color toner other than black toner, but may be formed of black toner.

Next, the operation of the density measuring apparatus 1 and the control operation of the image forming apparatus based on the density measurement will be described with reference to the flowchart of FIG.

First, in the density measuring device 1, when it is determined that the preset density measuring time has come (step 1: S1), the density measurement by the photo sensor 4 and the output correction circuit 50 are performed. Is performed (S2).

First, as shown in FIG. 3, the output values V11 and V22 at the time of density measurement are measured by the density measuring device 1 (S10). The output value V11 is obtained by measuring the output value of the light receiving element 43 in a state where the light emitting elements 41 and 42 of the photo sensor 4 are turned off.
Regarding the output value V22, the light emitting element 4
2 (41) is obtained by measuring the output value of the light receiving element 43 in the state where light is irradiated.

Subsequently, as a density measurement operation, a predetermined control toner image (patch) _Tpatch made of color toner is formed on the image carrier 2 by the image forming apparatus, and the photosensor 4 of the toner image _Tpatch is used. Measurement is performed (S11). That is, since the toner image T _`patch is made of a color toner, the photo sensor 4 is performed the measurement is used as the" diffuse reflection type sensor ", specifically, diffuse reflection on the toner image T _{pa tch} Light emitting element 4 for
2, light H ₃ is emitted, and the shared light receiving element 43 receives the diffusely reflected light H ₄ from the toner image T _patch . Thus, an output value Vp for the toner image T _patch is obtained.

Next, the output value Vp is subjected to a correction process based on the correction formula in the output correction circuit 8 (S12). That is, in the correction equation, the output values Vp and the output values V11 and V22 measured in step S10 and the output values V10 and V20 measured and recorded beforehand are substituted and calculated. Thereby, the corrected output value Vn is calculated.

Step 2 (steps 10-1)
When the density measurement and the output correction process in 2) are completed, the corrected output value Vn previously calculated is determined as a formal measurement result of the photosensor 4 (S3).

Then, the determined measurement result (output value Vn) is sent from the sensor controller 5 to the image forming apparatus side, and the image forming apparatus needs to change the setting of the image forming process conditions set in advance. (S4), it is not necessary to change the setting of the image forming process condition within the allowable range, but if it exceeds the allowable range, the setting change of the condition is not required. Is required, and predetermined image forming process conditions are set (S5). The process conditions set in accordance with the result of the density measurement include, for example, an exposure light amount, a charging potential,
The table includes a table for correcting gradation characteristics of image data in addition to a developing bias potential, a toner density, and the like, but is not limited thereto.

In the density measuring device 1, as described above, the output value Vp relating to the toner image T _patch is corrected, so that the output of the photo sensor 4 has only one type of variation as described above. , Or in combination, the accurate sensor output value Vn in the initial state (at the time of setup), and thus the density of the toner image T _patch , can be measured accurately and _simply regardless of the type of the fluctuation. Thus, the control setting of the image forming process conditions performed based on the measurement result can be performed accurately. Further, in the concentration measuring device 1, it is possible to accurately correct the sensor output without particularly needing to add new components and the like, so that unnecessary cost increase does not occur, and the output value V11 and the output value V11 at the time of concentration measurement are not increased. V
Since the measurement of 22 can be performed instantaneously, there is an advantage that the measurement time is not particularly limited. However,
When such a correction process is performed by a diffuse reflection type photosensor in which the sensor output on the surface of the toner image carrier is smaller than the sensor output of the toner image, the output member Vp relating to the toner image has output values V11 and V22. Is outside the range,
Correction accuracy is slightly reduced.

FIG. 4 is an explanatory diagram showing the relationship between the output characteristics of the density measuring device 1 (photo sensor 4) at the initial stage and at the time of density measurement, and the elements relating to the correction formula of the output correction process. The solid line in the figure shows the output characteristics at the initial stage, and the two-dot chain line shows the output characteristics at the time of concentration measurement after the fluctuation. In the drawing, reference symbol G1 is the above-described first correction reference point, and G2 is the above-described second correction reference point.

For example, in the photosensor 4 having the output characteristics shown in FIG. 4, it is assumed that the measured output values are V10 = 4, V20 = 7, V11 = 1, and V22 = 2. In this case, the output value Vp when the output value Vp relating to the toner image T _{patch is} corrected by the above-described correction formula
n is as follows. The output value Vp is Vp = 3. Vn = {(7-4) (3-1) / (2-1)} + 4 = 1
0

In this embodiment, the density of the toner image T _patch composed of color toner is measured by the diffuse reflection type sensor function of the photo sensor 4 and the output value Vp at that time is measured.
_Has been described as an example where the toner image T _patch has been corrected.
Is composed of black toner, the toner image is measured by the regular reflection type sensor function of the photosensor 4 (that is, the toner image is irradiated with light from the regular reflection light emitting element 41, to receive regular reflection H ₂ to the light receiving element 43), it is possible to correct the output value Vp at that time by the correction equation. In this case, when measuring the output values V20 and V22 used in the correction equation, the light emitting element 4 for specular reflection is used.
What is necessary is just to make 1 emit light and irradiate the surface of the image carrier 2.

[Second Embodiment] FIG. 5 is a schematic diagram of a concentration measuring apparatus according to another embodiment of the present invention. The density measuring device 1 according to the present embodiment uses a photosensor 4 provided with a reference reflection surface 7 for output correction, and includes elements (first and second) used in a correction equation of an output correction circuit 50.
Of the density measuring apparatus according to the first embodiment, except that the correction reference points G1 and G2 and their respective output values) are partially changed.

That is, in the photosensor 4, the reference reflection surface 6 is provided inside the sensor holder 44 between the light exit optical path 45b and the light entrance optical path 45c, and the reference reflection surface 6 has a diffuse reflection light emitting element. A part of the irradiation light H ₃ emitted from 42 is irradiated, and the reflected light H ₈ reflected by the reflection surface 6 is applied.
An optical path 45d for reference reflection is formed so that the light is received by the shared light receiving element 43. In this embodiment, the reference reflection surface 6 is formed by using a part of the sensor holder 44 as it is as a reflection surface, but a separate reference reflection plate (member) is provided in the holder 44. There may be.

Further, since the photosensor 4 is provided with the reference reflecting surface 6, the optical path 45d between the reference reflecting surface 6 and the common light receiving element 43 and the light entering optical path 45c are switched and used. An optical path switching mechanism 7 is provided. The optical path switching mechanism 7 is a mechanism capable of opening one of the optical path 45d and the optical path 45c and shielding the other (the state shown by hatching in the drawing). It is controlled by a control 5 or the like. Therefore, when it is opened the light path 45c for the light incident through the optical path switching mechanism 7 (Fig. 5a), is as diffuse reflected light H ₄ from the toner image or the like is received by the light receiving element 43, whereas the reference reflecting When the optical path 45d is opened (FIG. 5B), the reference reflection surface 6
Reflected light H ₈ from is to be received by the light receiving element 43.

Further, the output correction circuit 50 serves as a first correction reference point G1 in the above-mentioned correction formula used in the output correction processing, the surface of the image carrier 2 (the surface when the toner image T _patch is not formed). And the reference reflection surface 6 is set as the second correction reference point G2. Therefore, the light receiving element 43 when irradiated with light H ₃ of the image bearing member 2 from the surface diffuse reflection light emitting element 42 in the V10 early stage in the correction equation used in this output correction circuit 50 (during setup) output value, V11 becomes similar output value when during its density measurement, also V20 is the output value of the light-receiving element 43 when it receives the reflected light H ₈ from the reference reflecting surface 6 in the initial stage, V22 is its concentration The same output value is obtained at the time of measurement.

The density measuring apparatus 1 including the photosensor 4 and the output correction circuit 50 outputs the output values V10 and V20 when the photosensor 4 is set up, as in the first embodiment. The measured values are stored in a predetermined storage unit. When the density is measured, the output values V11 and V22 are used.
Is measured (step S10 in FIG. 3), and the toner image T
_The output value Vp for the _patch is corrected by the correction formula (S12).

Thus, in the case of the density measuring device 1, even if various output fluctuations occur in the photo sensor 4, the toner image T
The output value Vp of the _patch is obtained as the corrected output value Vn, and the density of the toner image T _patch can be measured accurately and simply.

Further, in the density measuring device 1, since the output value related to the light reflected from the reference reflecting surface 6 is used as one of the output values of the correction reference point, the output value becomes stable and the output correction is performed. Can be performed more stably. Moreover, since the reference reflecting surface 6 is fixedly provided inside the sensor holder 44, the reference reflecting surface 6
Is not contaminated by toner or the like, and its reflection characteristics do not fluctuate. This also enables more stable output correction.

FIG. 6 is an explanatory diagram showing the relationship between the output characteristics of the density measuring device 1 (photosensor 4) according to the present embodiment at the initial stage and at the time of density measurement, and the elements relating to the correction formula of the output correction process. It is. For example, in the photosensor 4 having an output characteristic as shown in FIG. 6, the measured output values are V10 = 4, V20 = 10, V20
Assuming that 11 = 1 and V22 = 3, the toner image T
The output value Vn when the output value Vp relating to _{patch is} corrected by the above-described correction formula is as follows. The output value Vp at this time is Vp = 2. Vn = (10-4) (2-1) / (3-1) + 4 = 7

In this embodiment, the photosensor 4 provided with the reference reflecting surface 6 is shown in FIGS.
It is also possible to use a photosensor 4 of the type shown in FIG.

The photosensor 4 shown in FIGS. 7 and 8 is an example in which the reference reflection surface 6 is provided outside the sensor folder 44. The reference reflection surface plate 60 is arranged in the directions of arrows A and B around the fulcrum 80. It is attached to a cleaning member 8 that swings and touches the sensor surface (dustproof member 46) of the photosensor 4 to clean the surface. When the reference reflecting surface plate 60 is used, the cleaning member 8 moves in the direction of arrow B to clean the sensor surface as shown in FIG. Are positioned so as to close the respective openings. Thereby, the light H ₃ of the light emitting element 42 for diffuse reflection is referenced through its light exiting optical path 45 b (in this example, a part of the main optical path 45 b is partially enlarged to secure the optical path of the light H ₃ ). is irradiated on the reflection surface plate 60, the reflected light H ₉ is adapted to be received by the light receiving element 43 of the shared. On the other hand, when the reference reflecting surface plate 60 is not in use, as shown in FIG. 8A, the cleaning member 8 swings in the direction of arrow A and does not block any of the openings of the optical paths 45a to 45c of the photosensor 4. Waiting in position.

The photosensor 4 shown in FIG. 8 has an embodiment in which the reference reflection surface 6 is provided inside the sensor folder 44 and a light emitting element 47 for irradiating the reference reflection surface 6 with a dedicated reflection surface is provided. It is. That is, the light is irradiated to the reference reflecting surface 6 from the light emitting element 47 for reflecting surface irradiation, the reflected light H ₁₀ which is reflected by the reflecting surface 6 is adapted to be received by the light receiving element 43 of the common through an optical path 45e I have. In this case, it is preferable to use the same light emitting element 47 for diffuse reflection as the light emitting element 47 for diffuse reflection.

[Embodiment 3] FIG. 10 is a schematic diagram of a concentration measuring apparatus according to another embodiment of the present invention. The density measuring apparatus 1 according to this embodiment uses a photo sensor 4 provided with a light receiving element 48 for monitoring the light emission amount of the diffuse reflection light emitting element 42, and uses the photo sensor 4 in the correction formula of the output correction circuit 50. Element (first and second correction reference points G
1 and G2 and their respective output values) have the same configuration as that of the concentration measuring apparatus according to the first embodiment, except for some changes.

That is, in the photosensor 4, a light receiving element 48 for monitoring is provided in an optical path for introduction communicating with the optical path 45b for light emission of the light emitting element 42 for diffuse reflection.
It adapted to monitor measures the amount of light H ₃ from the diffuse reflection light emitting element 42 by the light receiving element 48 for the monitor. In this case, it is preferable to use the same light receiving element 48 as the common light receiving element 43 as the light receiving element 48 for monitoring.

The output correction circuit 50 is used as a first correction reference point G1 in the correction equation used in the output correction processing, as the surface of the image carrier 2 (the surface when the toner image T _patch is not formed). And the output of the monitor light-receiving element 48 (the light amount of the diffuse reflection light-emitting element 43) is set as the second correction reference point G2. Therefore, the light receiving element 43 when irradiated with light H ₃ of the image bearing member 2 from the surface diffuse reflection light emitting element 42 in the V10 early stage in the correction equation used in this output correction circuit 50 (during setup) output value, V11 becomes similar output value when during its density measurement, also V20 is the output value of the light-receiving element 48 when it receives the light H ₃ from the diffuse reflection light-emitting element 43 in the initial stage, the V22 its The same output value is obtained when measuring the density.

The density measuring apparatus 1 including the photosensor 4 and the output correction circuit 50 can output the output values V10 and V20 when the photosensor 4 is set up, as in the first embodiment. The measured values are stored in a predetermined storage unit. When the density is measured, the output values V11 and V22 are used.
Is measured (step S10 in FIG. 3), and the toner image T
_The output value Vp for the _patch is corrected by the correction formula (S12).

Thus, in the case of the density measuring device 1, even if various output fluctuations occur in the photo sensor 4, the toner image T
The output value Vp of the _patch is obtained as the corrected output value Vn, and the density of the toner image T _patch can be measured accurately and simply.

In the density measuring apparatus 1, the output value of the light receiving element 48 for monitoring the light emission amount of the light emitting element 42 is used as one of the output values of the correction reference point. As in (60), the output value becomes stable, and output correction can be performed more stably. In addition, even if the output of the light emitting element 42 fluctuates, the state of the fluctuation is accurately grasped as the output value of the light receiving element 48, so that the output correction at that time is also accurately performed.

FIG. 11 is an explanatory diagram showing the relationship between the output characteristics of the density measuring device 1 (photosensor 4) according to this embodiment at the initial stage and at the time of density measurement, and the elements relating to the correction formula of the output correction process. It is. For example, in the photosensor 4 having the output characteristics shown in FIG. 11, the measured output values are V10 = 4 and V20 = 1.
Assuming that 0, V11 = 1, and V22 = 3, the output value Vn when the output value Vp for the toner image T _{patch is} corrected by the above-described correction formula is as follows. The output value Vp is Vp = 2. Vn = {(10−4) (2-1) / (3-1)} + 4 =
7

[Other Embodiments] The method of combination with the first and second correction reference points used in the above-described correction formula is, for example, the first type in the case of the photosensor in the second embodiment. The second reference point is a combination of a reference reflection surface and the second correction reference point is a first reference reflection surface and the second correction reference point is a second reference point, with the light-emitting element turned off. In the case of the photosensor according to Embodiment 3, a combination of a reference reflection surface (a reflection characteristic different from that of the first reference reflection surface), the second correction is performed in a state where the first correction reference point turns off the light emitting element. A combination in which the reference point is the output of the monitoring light receiving element is possible. Even when the correction formula is configured by such a combination, an accurate correction of the output value can be performed in the same manner as in the above-described first to third embodiments.

Further, in the first to third embodiments described above, the case of the density measuring device using a type which can be used as both a regular reflection type sensor and a diffuse reflection type sensor as the photo sensor 4 has been exemplified. The invention can be similarly applied to a density measuring apparatus using a photosensor of a single type of a diffuse reflection sensor or a single type of a regular reflection type sensor. Further, the present invention can also be applied to a density measuring device using a transmission type photosensor in which light is emitted from a light emitting element to a toner image T _patch and light transmitted through the toner image is received by a light receiving element. It is. Incidentally, the image forming apparatus to which the density measuring apparatus of the present invention is applied,
The method of forming the toner image and the control toner image T
There is no particular limitation on the type of image carrier that forms the _patch .

[0067]

As described above, according to the present invention,
As described above, the output value of the photosensor relating to the toner image is corrected by the output correction unit that performs the correction process based on the correction expression configured using the output values of the first and second correction reference points. Even if various types of output fluctuations occur alone or in combination, the output value of the photo sensor for the toner image can be corrected very easily and accurately, and as a result, errors due to output fluctuations are included. It is possible to perform accurate concentration measurement. Further, the density measuring device provided with the output correction means can be applied without being limited by the type of the photosensor, and has high versatility.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a concentration measuring device according to a first embodiment.

FIG. 2 is a flowchart showing operation contents of a control system relating to concentration measurement and process condition setting.

FIG. 3 is a flowchart showing an operation content of output correction processing at the time of density measurement.

FIG. 4 is an explanatory diagram showing a relationship between output characteristics of a density measuring device (photosensor) according to the first embodiment and elements related to a correction equation at the time of output correction.

FIG. 5 is a schematic diagram of a concentration measuring device according to a second embodiment.

FIG. 6 is an explanatory diagram showing a relationship between output characteristics of a density measuring device (photosensor) according to a second embodiment and elements related to a correction formula at the time of correcting the output.

FIG. 7 is a schematic diagram illustrating another configuration example of a photosensor in the density measurement device according to the second embodiment.

FIG. 8 is an explanatory diagram showing an operation state of the photosensor of FIG. 7;

FIG. 9 is a schematic diagram illustrating another configuration example of a photosensor in the density measuring device according to the second embodiment.

FIG. 10 is a schematic diagram of a concentration measuring device according to a third embodiment.

FIG. 11 is an explanatory diagram showing a relationship between output characteristics of a density measuring device (photosensor) according to the second embodiment and elements related to a correction equation at the time of output correction.

FIG. 12 is an explanatory diagram showing output characteristics when three types of output fluctuations are combined.

FIG. 13 is an output characteristic explanatory diagram for explaining a process of introducing a correction equation.

FIG. 14 is an output characteristic diagram showing types of output fluctuations in the diffuse reflection type and regular reflection type photosensors.

FIG. 15 is an explanatory diagram showing output characteristics when two types of output fluctuations are combined.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Density measuring device, 2 ... Image carrier (member on which a toner image is formed), 4 ... Photo sensor, 5 ... Sensor controller, 6 ... Reference reflection surface, 8 ... Cleaning member, 41, 42 ... Light emitting element, 43 ... light receiving element, 48 ... light receiving element for monitor, 5
0: output correction circuit (output correction means), 60: reference reflection surface plate, T _patch : toner image, G1: first correction reference point, G
2: Second correction reference point.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yamazaki Naoya 2274 Hongo, Ebina-shi, Kanagawa Prefecture, Fuji Xerox Co., Ltd. F-term (reference) 2G059 AA01 BB08 CC01 EE01 EE02 GG02 HH02 KK03 MM16 MM17 NN02 NN05 NN07 NN08 2H027 DA10 DA50 DE02 DE07 DE10 EC03 HB05 HB06 ZA07

Claims (5)

[Claims] 1. A photosensor that irradiates a toner image formed in an image forming apparatus with light from a light emitting element and receives a reflected light reflected by the toner image or a transmitted light transmitted through the toner image by a light receiving element. A density measuring device for measuring the density of the toner image based on the output value of the light receiving element of the photo sensor, wherein the output value of the preset first and second correction reference points of the photo sensor And output correction means for outputting the output value Vp of the toner image at the time of measuring the density of the photosensor as an output value Vn corrected by the following correction formula: Vn = ｛(V20−V10) (Vp−V11) / (V22-V1
1)｝ + V10 (where V10 is the output value of the first correction reference point in the initial stage, V20 is the output value of the second correction reference point in the initial stage, and V11 is the density measurement of the first correction reference point. , And V22 indicates an output value at the time of measuring the density of the second correction reference point). 2. An output value of a first or second correction reference point,
2. The density measuring apparatus according to claim 1, wherein the output value is a value of a light receiving element when a light emitting element for irradiating the toner image is turned off. 3. The output value of the first or second correction reference point is:
2. The density measuring apparatus according to claim 1, wherein the value is an output value of a light receiving element when light is emitted from a light emitting element to a surface of the member on which the toner image is formed. 4. When a reference reflection surface is provided inside or outside of the photosensor, the output value of the first or second correction reference point indicates the light reception when the reference reflection surface is irradiated with light from a light emitting element. 2. The concentration measuring device according to claim 1, wherein the concentration is an output value of an element. 5. When the photosensor is provided with a light receiving element for monitoring a light emission amount of a light emitting element for irradiating the toner image with light, an output value of the first or second correction reference point is used for monitoring the light amount. 2. The concentration measuring device according to claim 1, wherein the output value is a light-receiving element output value.