JP2006349715A - Image density detector and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image density detector for detecting image density on an image carrier by using a low-cost optical density sensor, and to provide an image forming apparatus using the image density sensor. <P>SOLUTION: The image forming apparatus includes; an image carrier which holds an image; an image forming means for forming the image on the image carrier based on inputted image data; and a detecting means for detecting image information on the image formed on the image carrier. A plurality of optical density sensors having different characteristics functioning as the detecting means are arranged in the moving direction of the image on the image carrier. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer. In particular, the present invention relates to an image forming apparatus that forms a reference pattern for adjusting image density on an image carrier and adjusts image forming conditions based on optical detection results.

  In image forming apparatuses such as conventional copying machines and laser beam printers, image density control has been used to stabilize the image density of an image to be printed. In particular, when a full-color image is formed by superimposing cyan, magenta, yellow, and black toners, the tone of a color image to be printed changes when any of the densities changes, so that a halftone image Concentration must also be controlled. Here, in order to perform image density control, it is necessary to first detect the image density of the apparatus. As a detection method, a method using an optical density sensor in which a light emitting element and a light receiving element are integrated is generally used. That is, an image is formed on the image carrier with the reference pattern, light from the light emitting element is irradiated onto the toner-attached area, and light reflected from the image carrier and toner is detected by the light receiving element. Since the amount of reflected light varies depending on the toner adhesion amount on the surface of the image carrier, the toner adhesion amount and thus the image density can be detected by the output of the light receiving element. As the optical density sensor, for example, a sensor as shown in Patent Document 1 is used. FIG. 9 shows a conventional toner adhesion amount measuring apparatus described in Patent Document 1.

  In FIG. 9, the optical density sensor includes a light emitting unit 102 that projects light onto the surface of the photosensitive drum 101, and a light receiving unit 103 that receives reflected light reflected by the light projected from the light emitting unit 102 when it hits an object. Here, the photosensitive drum 101 is obtained by mounting a metal rotating drum 101a with a photosensitive member 101b such as selenium or amorphous silicon.

  The light emitting unit 102 includes an LED 104 that is a light emitting element and a P polarizing filter 105 that transmits only P-polarized light. The LED 104 is arranged at an angle inclined with respect to the normal direction of the photosensitive drum 101. The The light receiving unit 103 includes a polarization separation prism 106 that separates P-polarized light and S-polarized light, and two photodiodes (hereinafter referred to as PD 107 and PD 108) that are light receiving elements. PD 107 and PD 108 are the same element, and only their mounting positions are different.

  The detection operation of the optical density sensor having the above configuration will be described. Toner that is an image forming substance in an image forming apparatus using an electrophotographic process is electrostatically attached to the surface of the photosensitive drum 101. When the measurement light is projected from the LED 104 to the toner 109 attached to the photosensitive drum 101, the measurement light including the P-polarized light P1 and the S-polarized light S1 is cut by the P-polarization filter 105, and the light Only P1 is projected onto the toner 109.

  A part of the incident light P <b> 1 of the toner 109 is reflected on the surface of the toner 109, and the rest is transmitted through the toner layer. A part of the light transmitted through the toner layer is further reflected on the surface of the photoreceptor 101b, and the rest is transmitted through the photoreceptor 101b. And all the light which permeate | transmitted the photoconductor 101b is reflected by the surface of the rotating drum 101a.

  The reflected light described above is light-reflected on the surface of the toner 109, the polarization of which is disturbed by the toner 109 that is a dielectric, and includes P-polarized light and S-polarized light. The light reflected from the surface of the photoconductor 101b becomes P-polarized light without being disturbed because the photoconductor 101b becomes conductive and non-dielectric when the light is incident. The light reflected from the surface of the rotating drum 101a is a non-dielectric material because the rotating drum 101a is metallic, and the polarization is not disturbed and becomes P-polarized light.

  A polarization separation prism 106 is provided on the optical path of the light that is regularly reflected by the light reflected by the projection light, and the regularly reflected light is separated into P-polarized light and S-polarized light. Of these separated lights, the P-polarized light is received by the PD 107 and the S-polarized light is received by the PD 108.

  A part of the light projected onto the toner 109 is reflected by the dielectric toner 109 as P-polarized light P2 and S-polarized light S2, and part of the light transmitted through the toner layer is the photoreceptor 101b. Is reflected as P-polarized light P3. Further, all the remaining light transmitted through the photosensitive member 101b is reflected as P-polarized light P4 on the surface of the rotating drum 101a.

  These reflected lights S2, P2, P3, and P4 enter the polarization separation prism 106, and are separated into P component light P2, P3, and P4 and S component light S2. As for the separated light, P-polarized light P2, P3, and P4 are received by the PD 107, and S-polarized light S2 is received by the PD.

  Here, among the light P2, P3, and P4 received by the PD 107, the light P3 and P4 are light that has passed through the toner 109. Therefore, the light P3 and P4 vary depending on the amount of toner 109 attached. That is, when the adhesion amount of the toner 109 is large, the lights P3 and P4 decrease, and when the adhesion amount of the toner 109 is small, the lights P3 and P4 increase. Therefore, the amount of toner 109 attached can be known by measuring the lights P3 and P4.

  Of the light P2, P3, and P4 received by the PD 107, the light P2 is reflected by the toner 109, and is proportional to the light S3 reflected by the toner 109 received by the PD. Therefore, a value approximate to the light P2 can be obtained by multiplying the output signal of the PD 108 by the constant coefficient K. As a result, the lights P3 and P4 are obtained by subtracting a value obtained by multiplying the output signal of the PD 108 by the constant coefficient K from the output signal of the PD 107. That is, if the adhesion amount of the toner 109 is T, the output signal of the PD 107 is an output signal a, and the output signal of the PD 108 is an output signal b, the adhesion amount T is proportional to a−Kb.

PD 107 and PD 108 photoelectrically convert each reflected light to output output signals a and b, which are sent to signal processing circuit 110 shown in FIG. The signal processing circuit 110 includes amplifiers 111a and 111b and a differential amplifier 112. The amplifier 111a amplifies and outputs the output signal a of the PD 107, and the amplifier 111b amplifies bK by multiplying the output signal b of the PD 108 by a constant coefficient K. Output a signal. Then, the differential amplifier 112 calculates the difference signal as toner adhesion amount information and outputs it as measurement data T.
Japanese Patent No. 2729976 (page 3, FIG. 1)

  However, in the conventional configuration, two light receiving elements are necessary and one polarizing element is necessary due to the configuration of one light emission and two light receptions, and thus the number of parts is large. In addition, the optical path for receiving the specularly reflected light requires accuracy in the housing for fixing each element in order to provide the accuracy, which has been a factor in increasing costs.

  The present invention solves the above-described conventional problems, and provides an image density detection apparatus capable of detecting an image density on an image carrier using an inexpensive optical density sensor and an image forming apparatus using the same. For the purpose.

  In order to solve the above-described conventional problems, an image density detection apparatus of the present invention includes an image carrier that holds an image, and an image forming unit that forms an image on the image carrier based on input image data. Detecting means for detecting image information of an image on the image carrier, and a plurality of optical density sensors having different characteristics are used as the detecting means. With this configuration, it is possible to detect the image density using an inexpensive optical density sensor having a rough configuration without using an expensive optical density sensor having a large number of parts.

  The image forming apparatus according to the present invention further includes an image carrier that holds an image, an image forming unit that forms an image on the image carrier based on input image data, and an image of the image on the image carrier. Detection means having a plurality of optical density sensors having different characteristics in order to detect density, and adjustment means for adjusting conditions when the image forming means forms an image based on the image density detected by the detection means Prepare. With this configuration, it is possible to adjust the image density by using an inexpensive image density detection means.

  According to the image density detection device of the present invention, an image density can be detected by combining a low-cost photosensor without using an expensive image density sensor with a large number of parts and high mechanical accuracy. A low-cost image forming apparatus can be provided without deteriorating quality.

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

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1 of the present invention. The image forming apparatus in FIG. 1 forms a color image by superposing four color toners of cyan, magenta, yellow, and black. The input color image data is decomposed into four-color image data by a preceding controller (not shown) and input to the image output unit 10 for each color.

  In the image output unit 10, the laser output unit 11 is driven based on the input image data, and the modulated laser light irradiates the photosensitive drum 12. At this time, the surface of the photosensitive drum 12 is uniformly charged by the scorotron charger 13, and an electrostatic latent image is formed by irradiation with laser light. The electrostatic latent image formed on the photosensitive drum 12 is developed into a visible toner image when the developing roller of the corresponding color comes in contact with the developing unit 14Y, 14M, 14C, or 14K. A primary transfer bias is applied to the primary transfer roller 16, and the toner image attached to the surface of the photosensitive drum 12 is moved to the surface of the intermediate transfer belt 15 by electrostatic force. After the toner image is transferred to the intermediate transfer belt 15, the photosensitive drum 12 removes the toner remaining on the surface by the cleaner 19. This completes the monochrome image forming process. By repeating this process for each color, a color toner image is formed on the surface of the intermediate transfer belt 15.

  The color toner image formed on the surface of the intermediate transfer belt 15 is transferred onto the conveyed paper by the secondary transfer roller 17 to which a secondary transfer bias is applied. The fixing device 18 presses the heated roller against the paper, and fixes the color toner image transferred onto the paper to the paper. Thereafter, the sheet is discharged out of the apparatus, and a series of image forming processes is completed. Here, the image density sensor 20 is installed between the last developing device 14 </ b> K and the primary transfer roller 16 in order to detect the density of the toner image on the photosensitive drum 12.

  The image density sensor 20 is composed of two photosensors 21 and 22, and these two photosensors are arranged side by side in the rotation direction of the photosensitive drum 12. FIG. 2 shows a layout of the photosensor 21 when viewed from the thrust direction of the photosensitive drum. FIG. 3 shows a layout of the photosensors 21 and 22 when viewed from the central axis direction of the photosensitive drum. Photosensors 21 and 22 are LEDs 21 a and 22 a that are light emitting elements and photodiodes 21 b and 22 b that are light receiving elements arranged side by side. The distance and angle between the sensor surface and the surface of the photosensitive drum 12 are set so that the sensitivity of the photosensor is the highest. Here, the distance between the sensor surface of the photosensors 21 and 22 and the surface of the photosensitive drum 12 is set to 6 mm, and the axis in the normal direction is perpendicular to the sensor surface and the surface of the photosensitive drum 12.

  The photosensor 21 and the photosensor 22 have the same element configuration, but the arrangement of the elements is different. That is, the distance between the LED 22a and the photodiode 22b is longer than the distance between the LED 21a and the photodiode 21b. By changing this distance, when detecting the density of the reference toner image formed on the surface of the photosensitive drum 12, it is possible to change whether the reflected light is mainly detected or the scattered reflected light is mainly detected. Can do. That is, since both the LED and the photodiode have directivity, a light emitting area in which the LED illuminates the surface of the photosensitive drum 12 and a light receiving area in which the photodiode receives light reflected from the surface of the photosensitive drum 12. This is achieved by changing the overlapping state.

  FIG. 4 shows a configuration diagram of a photosensor having a detection principle mainly based on regular reflection light. In addition to the short distance between the LED 21a and the photodiode 21b, the directivity of the LED 21a is wide, and the light emitting area covers the entire light receiving area of the photodiode 21b. Therefore, specularly reflected light enters from all the light receiving regions of the photodiode 21b, so that the ratio of the specularly reflected light to the received light increases.

  On the other hand, FIG. 5 shows a configuration diagram of a photosensor having a detection principle mainly based on scattered light. Compared with the photosensor of FIG. 4, the distance between the LED 22a and the photodiode 22b is longer, and the directivity of the LED 22a is narrower. Therefore, the light emitting area of the LED 22a and the light receiving area of the photodiode 22b do not overlap at all. The regular reflection light irradiated from the LED 22a and reflected by the surface of the photosensitive drum 12 is not received by the photodiode 22b, but only scattered light is received.

  These two types of photosensors 21 and 22 are arranged side by side in the rotation direction of the photosensitive drum 12 as shown in FIG. At the time of density detection, the photosensor 21 mainly composed of regular reflection light detects the black toner adhesion amount, and the photosensor 22 mainly composed of scattered light detects toner adhesion amounts of colors other than black, that is, cyan, magenta and yellow. Black is detected by specularly reflected light. When light is projected onto a black toner image, most of the scattered light component reflected by the toner image is absorbed by the black toner, and only a small amount of scattered light component is emitted. This is because it does not come. As a result, even if the toner adhesion amount increases, the increase amount of the scattered light component is small, so that a sufficient dynamic range cannot be obtained and the detection accuracy does not increase.

  On the other hand, the specularly reflected light component is close to total reflection when the toner is not attached, so most of the light is reflected by the surface of the photosensitive drum 12, and most of the light is received by the photodiode 21b. When the amount of toner adhering increases, the surface of the photosensitive drum 12 is covered, so that the proportion of the light that is scattered and reflected in the projected light increases and the proportion of the regular reflection light decreases. Furthermore, since a part of the reflected light is absorbed by the black toner, the amount of light received as regular reflected light is greatly reduced. For this reason, when the amount of adhering toner increases, the sensor output photoelectrically converted by the photodiode 21b greatly decreases.

  However, in the case of color toners such as cyan, magenta, and yellow, the tendency is opposite to that in the case of black toner. The amount of specularly reflected light component at the time of color toner detection also becomes maximum when the toner is not attached, and when the toner adheres and the surface of the photosensitive drum 12 is covered, the scattered reflection component increases. The amount of specular reflection decreases. However, since it does not absorb light like black toner, the amount of decrease is smaller than that of black toner. Specifically, when the output of the photodiode is compared between when no toner is attached and when the toner is attached on one side, that is, when a solid image is formed, the dynamic range at the time of detecting the color toner is larger than that at the time of detecting the black toner. Only about half.

  On the other hand, the scattered reflected light component at that time is slightly present because scattering reflection occurs due to fine irregularities on the surface of the photosensitive drum 12 even when the toner is not attached. As the toner adhesion amount increases, the amount of scattered reflected light also increases accordingly. Therefore, the amount of toner adhesion can be detected by subtracting the output at the time of detecting the background without toner adhesion from the output at the time of adhesion of toner from the output of the photodiode. Since the dynamic range when the toner is not attached and when the solid image is formed is larger than when detecting the regular reflection light, it is preferable to use the scattered reflection light for the detection of the color toner.

  As described above, when black toner is detected, detection is performed based on the specular reflection light component, and when color toner is detected, detection is performed based on the scattered reflection light component. That is, black toner is detected by the photosensor 21 that detects mainly reflected light, and color toner is detected by the photosensor 22 that mainly detects scattered reflected light, so that detection can be performed according to the characteristics of each toner. it can.

  Further, in order to control the image forming process conditions in order to keep the image density within a predetermined range, the reference toner image is formed by changing the bias voltage of the charging process and the developing process. Since these bias voltages and the like can be changed only in the rotation direction of the photosensitive drum 12, two types of photosensors are arranged side by side in the circumferential direction of the photosensitive drum 12, as shown in FIG.

  In the present embodiment, the density sensor including two photosensors is provided at one location near the photosensitive drum 12, but a plurality of density sensors may be provided. Thereby, the density can be uniformly controlled over the entire printed image.

(Embodiment 2)
FIG. 6 is a schematic configuration diagram of the image forming apparatus according to the second embodiment of the present invention. The image forming apparatus shown in FIG. 6 does not superimpose one color at a time on a single photoconductor drum 12 as in the image forming apparatus shown in FIG. 1, but the photoconductor drums 12Y, 12M, 12C, and 12K and their associated ones. The developing devices 14Y, 14M, 14C and 14K and the charger (not shown) are arranged in the moving direction of the intermediate transfer belt 15 and arranged in tandem. The laser output unit 11 irradiates the surface of the corresponding photosensitive drum with four laser beams independently based on the four systems of input image data. Here, the density sensor 20 does not detect the toner image attached to the surface of the photosensitive drum, but detects the toner image transferred from the photosensitive drum to the intermediate transfer belt 15 so as to detect the black photosensitive member. It arrange | positions in the back | latter stage of the position where the drum 12K touches. By doing so, only four density sensors are required on the photosensitive drum.

  The image forming process in this configuration will be described by taking a yellow image forming process as an example.

  A charger (not shown) uniformly charges the surface of the yellow photosensitive drum 12Y. The laser output unit 11 exposes the uniformly charged surface of the photosensitive drum 12Y based on the input yellow image data to form an electrostatic latent image. The developing device 14Y attaches toner to the electrostatic latent image formed on the surface of the photosensitive drum 12Y to form a visible toner image. Thereafter, the toner image moves to the surface of the intermediate transfer belt 15 by electrostatic force when the photosensitive drum 12Y rotates and reaches the position of the first transfer roller 16Y. Thus, a yellow toner image is formed on the intermediate transfer belt 15.

  Similarly, for magenta, cyan, and black, toner images are transferred to the surface of the intermediate transfer belt 15 and are overlaid to form a color toner image. The color toner image formed on the intermediate transfer belt 15 is transferred to the sheet conveyed at the position of the second transfer roller 17. The fixing device 18 presses the heating roller against the toner image transferred onto the paper and fixes it on the paper. Thereafter, the sheet is conveyed to a conveyance roller (not shown) and discharged outside the apparatus. As described above, the tandem-type image forming apparatus can perform four-color superposition at a time by shifting the image formation start timing by a time corresponding to the interval between the photosensitive drums, thereby achieving high-speed image formation. It becomes possible.

  The density sensor 20 is composed of photosensors 21 and 22, and is disposed in the subsequent stage of the black photosensitive drum 12K. At the time of image density detection, light is projected onto a toner image of a reference pattern formed under a predetermined process condition, and light reflected from the toner image is received and detected. At this time, since the sheet is not conveyed, the toner image on the intermediate transfer belt 15 is removed by a cleaner (not shown).

  FIG. 7 and FIG. 8 show an example of a reference pattern formed for image density detection. FIG. 7 shows a reference pattern in which the pattern density, that is, the coverage is changed. Here, each color is formed with three coverages of 20% (Y1), 50% (Y2), and 100% (Y3). FIG. 8 shows an image formed by changing the process conditions with a reference pattern having the same coverage. Here, the reference pattern having a coverage of 50% is formed by changing the developing bias. Assuming that the reference developing bias is −350 V, image formation is performed under three types of conditions such as −300 V (Y4), −350 V (Y5), and −400 V (Y6).

  For the reference pattern to be formed, a set density for the pattern is determined in advance (for example, a density of 1.5 at 100% coverage and a density of 0.4 at 20% coverage). It is desirable that this is close to the set concentration under any environmental conditions and aging conditions. For this reason, a reference pattern is formed under the current environmental conditions and time-dependent conditions, and the process conditions are controlled so that the reference pattern becomes the set concentration.

  In the present embodiment, in the reference pattern in which the coverage is changed, the coverage is set to 20%, 50%, and 100%. Furthermore, when the detection accuracy of 100% coverage is not sufficient, extrapolation may be performed from the result of density detection at, for example, 20% and 60% coverage. Further, when changing the process conditions, the developing bias is changed by 50V, but other numerical values may be used. Further, parameters such as laser power and charging bias may be used as parameters, and parameters having deep correlations such as charging bias and developing bias may be linked.

  In the present embodiment, the density sensor including two photosensors is provided at one location near the intermediate transfer belt 15, but a plurality of density sensors may be provided. At that time, it is possible not only to detect the image density by providing density sensors at both ends in the printing direction, but also to serve as a color deviation detection sensor by forming and reading a reference pattern for color deviation detection. It is.

  In this embodiment, the density sensor is arranged in the moving direction of the image carrier (photosensitive drum or intermediate transfer body) so that the influence of uneven toner adhesion in the main scanning direction can be suppressed. A configuration for detecting patches was adopted. For example, in an apparatus configuration in which toner unevenness in the main scanning direction does not originally occur, the density sensor is arranged in a direction intersecting with the moving direction of the image carrier (photosensitive drum or intermediate transfer member). May be.

  In the present embodiment, the image carrier is an intermediate transfer belt, but may be a roller-shaped intermediate transfer roller. In this case as well, as in the case of the intermediate transfer belt, the same effect can be obtained by placing a density sensor between the position where the photosensitive drum of the color to be overlaid last comes into contact with the position where it is transferred to the paper. Is obtained.

  An image density detection apparatus and an image forming apparatus using the same according to the present invention detect a toner adhesion amount, that is, an image density, on a toner image carrier such as a photosensitive drum or an intermediate transfer belt using a low-cost photosensor. . This eliminates the need for an expensive concentration sensor having a complicated configuration and a precisely adjusted optical path, and is effective in reducing the cost of the apparatus. Furthermore, not only the image density but also a plurality of density sensors are installed at both ends of the image forming area, so that it can also serve as a color shift detection sensor.

1 is a schematic configuration diagram of an image forming apparatus according to Embodiment 1 of the present invention. Photosensor layout as seen from the thrust direction of the photoconductor drum Photo sensor layout as seen from the central axis of the photoconductor drum Configuration diagram of photo sensor with detection principle based on specular reflection light Configuration diagram of photo sensor with detection principle based on scattered light Schematic configuration diagram of an image forming apparatus in Embodiment 2 of the present invention The figure which shows an example of the reference pattern formed for image density detection The figure which shows an example of the reference pattern formed for image density detection Schematic configuration diagram of a conventional toner adhesion amount measuring device Configuration diagram of signal processing circuit of conventional toner adhesion amount measuring device

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image formation part 12 Photosensitive drum 14Y, 14M, 14C, 14K Developer 15 Intermediate transfer belt 20 Density sensor 21, 22 Photo sensor 21a, 22a LED
21b, 22b Photodiode 101 Photosensitive drum 104 LED
105 P polarization filter 106 Polarization separation prism 107, 108 Photodiode 109 Toner

Claims (16)

An image carrier for holding an image;
Image forming means for forming an image on the image carrier based on input image data;
Detecting means for detecting image information of an image on the image carrier,
An image density detection apparatus comprising: a plurality of optical density sensors having different characteristics as the detection means. The image according to claim 1, wherein the plurality of optical density sensors are a scattering type optical density sensor that mainly detects scattered light and a regular reflection type optical density sensor that mainly detects regular reflected light. Concentration detector. 3. The image density detection apparatus according to claim 2, wherein the specular reflection type optical density sensor detects a black image density, and the scattering type optical density sensor detects an image density of other colors. The specular reflection type optical density sensor and the scattering type optical density sensor are each composed of a light emitting element and a light receiving element that receives reflected light reflected by a detection object, and the light emitting element and the light receiving element. The image density detection apparatus according to claim 2, wherein a distance between the image density and the image density is different. 5. The image density detection device according to claim 4, wherein the scattering type optical density sensor is set such that the distance between the light emitting element and the light receiving element is longer than that of the regular reflection type optical density sensor. The specular reflection type optical density sensor is configured by arranging a light emitting element and a light receiving element closer than a predetermined distance,
5. The image density detecting apparatus according to claim 4, wherein the scattering type optical density sensor is configured by disposing the light emitting element and the light receiving element farther than the predetermined distance. An image carrier for holding an image;
Image forming means for forming an image on the image carrier based on input image data;
Detecting means for detecting image information of an image on the image carrier,
The detection means includes
A first optical density sensor configured by arranging a light emitting element and a light receiving element closer than a predetermined distance;
A second optical density sensor configured such that a light emitting element and a light receiving element are disposed farther than the predetermined distance;
An image density detection apparatus comprising: The first optical density sensor is a specular reflection type optical density sensor that mainly detects specular reflection light.
8. The image density detecting apparatus according to claim 7, wherein the second optical density sensor is a scattering type optical density sensor that mainly detects scattered light. 9. The image density detection apparatus according to claim 8, wherein the regular reflection type optical density sensor detects a black image density, and the scattering type optical density sensor detects an image density of a color other than that. An image carrier for holding an image;
Image forming means for forming an image on the image carrier based on input image data;
Detecting means for detecting image information of an image on the image carrier,
The detection means includes a plurality of optical density sensors each having a light emitting element and a light receiving element that receives reflected light obtained by reflecting light emitted from the light emitting element by a detection target,
The image density detection apparatus according to claim 1, wherein the plurality of optical density sensors have different distances between the light emitting element and the light receiving element. The plurality of optical density sensors are:
A specular reflection optical density sensor that mainly detects specular reflection light;
A scattering type optical density sensor that is set so that the distance between the light emitting element and the light receiving element is longer than that of the specular reflection type optical density sensor, and mainly detects scattered light;
Have
11. The image density detecting apparatus according to claim 10, wherein the specular reflection type optical density sensor detects a black image density, and the scattering type optical density sensor detects an image density of other colors. The plurality of optical density sensors are arranged at the same position with respect to a direction perpendicular to the rotation direction of the image carrier and at different positions with respect to the rotation direction of the image carrier. Or the image density detecting device according to 10. The first optical density sensor and the second optical density sensor are arranged at the same position with respect to the direction perpendicular to the rotation direction of the image carrier and at different positions with respect to the rotation direction of the image carrier. The image density detection apparatus according to claim 7. The image density detection apparatus according to claim 1, wherein the image carrier has a photosensitive layer on a surface thereof. The image density detection apparatus according to claim 1, wherein the image carrier is a transfer body to which a toner image is transferred from a photosensitive member. An image density detection device according to any one of claims 1 to 15,
Adjusting means for adjusting the conditions when the image forming means of the image density detecting device forms an image based on the image density detected by the detecting means of the image density detecting device;
An image forming apparatus comprising:

Images