JPH05288677A - Toner-quantity detecting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform detection to a high density level without the effects of the life of a light emitting diode, temperature and contamination by providing a light source, which emits the light on a light sensitive body, a wavelength resolving photodetector, which divides the reflected light from the light sensitive body into the wavelength distribution, and a means, which detects the quantity of toner on the light sensitive body. CONSTITUTION:The emitted light from a light source 21 is reflected from the surface of a light sensitive body 1 and received with a wavelength resolving photodetector 22. The ratio of the outputs from the respective photodetectors 22 is obtained by utilizing the difference in spectral reflectances of the light sensitive body 1 and the toner. Thus the toner quantity on the light sensitive body 1 is detected. When an angle A of the reflected light of the light from the light source 21 at the light sensitive body 1 is smaller, the amount of the reflected light is increased. It is preferable that the angle A is 90 degrees or less. The light sensitive body 1 has the cylindrical shape. Therefore, the light path, on which-the light from the light source 21 reaches the photodetector 22 through the light sensitive body 1, is formed in a plane including the major axis of the cylinder so as to avoid nonuniformity of the reflecting direction caused by the curvature of the cylinder. As the shape of the light beam cast on the light sensitive body, the elliptical shape, which is in parallel with the axial direction of the cylinder, is suitable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner amount detecting device for detecting the toner density on a photosensitive drum in an electrostatic transfer type electrophotographic copying machine.

[0002]

2. Description of the Related Art Photoreceptor drums used in electrophotographic copying machines have characteristics depending on usage conditions, such as the influence of ambient temperature and humidity, deterioration over long-term use, or continuous large-volume copying without long-term use. Changes. Further, there are many factors that make the output image density unstable in an electrophotographic copying machine, such as the amount of toner adhering to the photoconductor changes due to the deterioration of the developer.

For this reason, a conventional toner amount detecting device exposes a non-image portion of a photosensitive drum with an image of a reference target, develops the image, and detects the density of the toner image by an optical detection method to detect the toner image. The supply amount, the developing bias voltage, the charging current, and the exposure current are controlled to maintain the optimum density of the output image. With this optical detection method, a pair of light emitting diodes and light receiving elements are provided and a reflection type arrangement is adopted.
This is a method of detecting the amount of toner on the photoconductor by the amount of reflected light, and a reference target having a uniform density (solid black) is used.

[0004]

However, in the above-mentioned optical detection method of the toner amount detection device, since the absolute light amount of the reflected light is detected, long-term deterioration of the light emitting diode, characteristic change due to temperature of the light emitting diode and the light receiving element, There is a problem in that the amount of toner cannot be accurately detected due to a change in temperature inside the electrophotographic copying machine and stains because it is entirely affected by a change in light amount due to stains. Further, at a high density level, the reflected light becomes extremely small, and the signal is buried in noise, which causes a problem that detection is difficult.

An object of the present invention is to provide a toner amount detecting device having a wide dynamic range capable of detecting a high density level without being affected by the life, temperature, dirt, etc. of a light emitting diode.

[0006]

The invention according to claim 1 of the present application is a wavelength-resolving light-receiving element for receiving a light source for irradiating a photoconductor and dividing reflected light from the photoconductor into at least two or more wavelength distributions. And a reference image that gives the photoreceptor a reference exposure,
Means for detecting the amount of toner on the photoconductor on the basis of the ratio of the output values from the wavelength resolving light receiving element.

The invention of claim 2 of this application is characterized in that a double junction type semiconductor color sensor is used for the wavelength resolving light receiving element.

The invention of claim 3 of this application comprises a light source for irradiating the photoconductor, a light receiving element for receiving the reflected light from the photoconductor, and a distribution of black and white regions of constant density on the surface of the photoconductor. And a means for detecting the amount of toner on the photoconductor depending on the state that the toner occupies the surface of the photoconductor.

According to a fourth aspect of the present application, in the reference image forming means, the density of the black area and the white area is 200 to 120 dots per inch, and the area ratio of the black area is 80% to 60%. It is a means for forming a mold reference image.

According to a fifth aspect of the present invention, a light source for irradiating the photoconductor, a light receiving element for receiving the reflected light from the photoconductor, a reference image forming means for giving a reference exposure to the photoconductor, and the light receiving device are provided. The amount of toner on the photoconductor is determined by comparing a reference density sample corresponding to the reference toner concentration of the element, a signal of the photodetection element detecting toner on the photoconductor and a signal of detecting the reference density sample on the photoconductor. Means to detect,
It is characterized by having.

According to the invention of claim 6 of this application, the photoconductor has a cylindrical shape, and an optical path of a light beam from the light source to the wavelength-resolving light receiving element or the light receiving element is in a plane including a long axis of the cylinder. It is characterized by being in.

According to the invention of claim 7 of this application, the shape of the light beam with which the photoreceptor is irradiated is elliptical, and the major axis of the ellipse coincides with the major axis direction of the cylinder of the photoreceptor. Characterize.

[0013]

In the present invention, the reference image is formed on the photoconductor. This reference image may be obtained by exposing and developing a reference target on which an image is drawn, or may be formed by reading out image data. The reference image causes the photosensitive member to be in a state in which the reference toner amount is overlaid. The photoconductor is irradiated with light from a light source, and reflected light is received by a wavelength resolution light receiving element divided into a plurality of wavelength regions. The amount of toner on the photoconductor is detected from the ratio of the outputs of the wavelength resolution light receiving element.

Further, in the present invention, the photosensitive member is exposed and developed by the distributed reference image so that the reference toner amount is kept. Light is emitted from the light source to the photoconductor, and reflected light is received by the light receiving element. The amount of toner on the photoconductor is detected from the output of the light receiving element.

Further, in the present invention, the photosensitive member is exposed and developed by the reference image, and the reference toner amount is kept. Light is emitted from the light source to the photoconductor, and reflected light is received by the light receiving element. On the other hand, the reference density sample is also irradiated with light from the light source, the reflected light is received by the light receiving element, and the toner amount on the photoconductor is detected by comparing the output of the photoconductor with the output of the reference density sample.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the construction of an electrophotographic copying machine. The electrophotographic copying machine 10 includes a rotating drum-shaped photosensitive member 1.
A charging device 2, an exposure device 3, a developing device 4, a transfer device 5, a static eliminator 6, a cleaner 7, and a toner amount detecting device 20 are provided around the photoconductor 1, respectively. The toner amount detection device is provided between the developing device 4 and the transfer device 5, or between the transfer device 5 and the static eliminator 6 when the toner amount detection mode does not fix the recording paper. Further, the charging device 2, the exposing device 3, the developing device 4, and the toner amount detecting device 20 are connected to the control device 9, and the control device 9 controls the toner amount detecting device 2.
A signal is output according to the input from 0, and the charging device 2, the exposing device 3, and the developing device 4 are controlled.

When copying is performed in the electrophotographic copying machine 10, the surface of the photoconductor 1 is uniformly charged by the charger 2 in the dark, and the exposure device 3 gives an optical image to be written on the photoconductor 1. At this time, the resistance of the exposed portion of the photoconductor 1 is lowered and the charged electric charge is removed, and the charged electric charge is left in the non-exposed portion to form an electrostatic latent image. On the other hand, the developing device 4 charges the toner with a polarity opposite to that of the photoconductor 1 to make the latent image visible. The toner amount detecting device 20 is
The toner amount on the photoconductor 1 is detected and transmitted to the control device 9, and the control device 9 detects the state of the toner on the photoconductor 1 by the input from the toner amount detection device 20 and, for example, charges the toner. A signal for adjusting the charging current, a signal for adjusting the exposure current to the exposing device 3, or a signal for adjusting the toner supply amount or the bias voltage to the developing device 4 is output to the developing device 2 and these signals are adjusted so that the optimum toner amount is obtained. Control. Thus, the photoconductor 1
Transfer the toner on the recording paper 8 by the transfer device 5,
The toner image transferred by heating or pressing is fused to the recording paper 8 to form a permanent image. After the transfer, the electric charge remaining on the photoconductor 1 is removed by the static eliminator 6, and the residual toner remaining on the photoconductor 1 is removed by the cleaner 7. As described above, copying is performed by repeating a series of processes from charging to cleaning.

At this time, in order to optimally control the toner amount,
It is necessary to form an image of a reference target (not shown) on the photoconductor 1 and detect the amount of toner on the photoconductor after the process by the developing device 4. In particular, if this control is automatically performed, a reference target is provided outside the copy effective area, a toner amount detection mode is entered when the power is turned on, and a predetermined toner amount is applied onto the photoconductor 1 so that the charging current is set. , Exposure current, toner supply amount, developing bias voltage, etc. are controlled. The reference target is composed of a known halftone of uniform density and is installed, for example, on the back side of the table (glass and its frame) on which the original is placed, in the immediate vicinity of the copy effective area. In this case, a plurality of reference targets having different densities may be sequentially arranged. Alternatively, a serviceman may set the manuscript on the platen at the time of adjustment. Further, in a laser printer or the like, the reference target may be stored as image data, and this data may be read and formed on the photoconductor during the toner amount detection operation.

FIG. 2 is an explanatory diagram of a toner amount detecting device according to an embodiment of the present invention. The toner amount detecting device 20 includes a light source 21, a wavelength resolving light receiving element 22, and a detecting circuit 23. The light emitted from the light source 21 is reflected on the surface of the photoconductor 1 and is received by the wavelength resolving light receiving element 22. The amount of toner on the photoconductor is detected by taking the output ratio from each element of the wavelength resolving light receiving element 22 by utilizing the difference in spectral reflectance between the photoconductor 1 and the toner.

In the toner amount detecting device 20, light in the visible region to the near infrared region or a part of the light is used, and therefore a white light source, LED, EL (electroluminescence) or the like is used as the light source 21. Electrophotographic copying machine 10
In the above, the light from the exposure unit 3 can be guided to the light source 21 by an optical fiber or the like. It has been confirmed by experiments that the smaller the angle A formed by the light from the light source 21 reflected by the photoconductor 1, the greater the amount of reflected light, and it is desirable that the angle A be within 90 degrees.

Since the photosensitive member 1 has a cylindrical shape, in order to prevent the reflection direction from becoming uneven due to the curvature of the cylinder,
The light path from the light source 21 to the wavelength resolving light receiving element 22 via the photoconductor 1 is formed within a plane including the long axis of the cylinder.

The shape of the light beam with which the photosensitive member 1 is irradiated is preferably an elliptical shape parallel to the axial direction of the cylinder, and the major axis diameter of the ellipse is 2 to 2 in consideration of uneven toner adhesion. 10
mm is good.

In this embodiment, since the difference in the spectral reflectance characteristics of the photoconductor and the toner is utilized, it is premised that the emission spectrum of the light source does not change. To compensate for this, do the following: The applied current of the white lamp is controlled so that the output of the wavelength resolving light receiving element 22 when the toner is not on the photoconductor at all becomes a specified value, and the emission spectrum of the white lamp becomes a predetermined spectrum. To do so. Immediately after that, the toner density is detected. By doing so, detection can always be performed under a constant emission spectrum.

Further, in order to monitor the emission spectrum of the light source 21, another wavelength resolving light receiving element capable of reading the spectral characteristic of light emission may be arranged.

The wavelength resolving light receiving element 22 comprises a plurality of light receiving elements such as photodiodes arranged in a plane, and filters having different spectral transmittances are arranged on the upper surface thereof. It is preferable that the distance between the respective light receiving elements is narrow, and if possible, it is desirable that two light emitting elements having different spectral sensitivities or two divided elements are contained in one package and share the optical window. Note that the number of wavelength-resolved light receiving elements is not limited to two, and more may be provided.

An example in which a double junction type semiconductor color sensor is used for the wavelength resolving light receiving element 22 will be shown. FIG. 3A shows 2
It is sectional drawing which shows the structure of a heavy-junction semiconductor color sensor, and the same figure (B) is a figure which shows the electrical equivalent circuit of two photodiodes of this color sensor. In the double-junction semiconductor color sensor, the PN junction is doubled in the thickness direction of silicon, short-wavelength light is absorbed near the surface of silicon, and long-wavelength light is absorbed in the deep portion. Therefore, the photodiode PD1 having the shallower PN junction has sensitivity on the short wavelength side, and the photodiode PD2 having the deeper PN junction has sensitivity on the long wavelength side. The short-circuit currents of the two photodiodes PD1 and PD2 are respectively changed to Isc1 and Isc.
sc2, as shown in FIG. 4, the ratio (Isc2 / I
From sc1), the wavelength of the light incident on the photodiode can be known. In this color sensor, two photodiodes PD1 and PD2 are vertically stacked, and there is no spatial positional deviation.
D2 is equally affected by dirt on the optical window. Therefore, by taking the output ratio of both, the influence can be completely eliminated.

The outputs from the photodiodes PD1 and PD2 are amplified by a amplifying circuit and a waveform shaping circuit of the detection circuit 23 and converted into a shaped waveform, and then input to a control device 9 including a microprocessor, where an output ratio between the two. Is calculated.

Since it is necessary to prevent ambient light other than the reflected light from the photoconductor 1 from entering the wavelength resolving light receiving element 22, the wavelength resolving light receiving element 22 is provided with a cylinder or a condenser lens. Alternatively, there is a method in which the light source 21 is pulse-emitted to make the toner amount detection signal alternating, and the influence of noise due to ambient light is suppressed. In this case, the light source 21 and the wavelength resolving light receiving element 22 are operated in synchronization. The wavelength resolving light receiving element 22 receives the light specularly reflected by the photoconductor 1 or the light diffusely reflected, and specular reflection is preferable because the amount of reflected light is large.

In such a toner amount detecting device,
It has been experimentally confirmed that the reliability of the toner concentration detection signal is improved and the toner concentration detection signal is also effective.

FIG. 5 shows the result obtained by an experiment using a double junction type semiconductor color sensor as the wavelength resolving light receiving element 22. The horizontal axis shows the optical density after copying to recording paper,
Specifically, it is expressed by the following equation.

Copy output density = -log (I / I0) where I0 is the amount of incident light and I is the amount of reflected light. The larger the copy output density value, the higher the toner density. To maintain good copy output, copy output density is 0.1
It is necessary to control from 1 to 1.4.

The white circles in FIG. 5 indicate the output ratio Is of PD1 and PD2.
The graph plotting c2 / Isc1 represents the spectral change of the reflected light. On the other hand, the black circle is the output I of PD2.
The graph plotting sc2 represents the absolute value of the amount of reflected light. The output ratio (spectral change) shows a large change at high concentration (around 1.4), and a high detection accuracy at high concentration can be expected. On the other hand, the output of PD2 (change in reflected light amount) shows a large change at medium and low concentrations (0.1 to 1.2). The output of PD2 can also be used for the detection of medium and low concentrations. However, the output of PD2 (absolute value of the amount of reflected light) varies due to various factors. Therefore, the output value of the PD 2 obtained by the reflected light from only the photoconductor is used as a reference value, and the output value obtained when the toner density is detected is divided by the reference value for normalization. This makes it possible to compensate for output fluctuations due to external factors.

Depending on the density range, either the ratio of output values or the output value is appropriately selected to detect the toner density. That is, by using the wavelength resolving light receiving element, a wide dynamic range from low density of copy output density to high density can be detected with high accuracy. It goes without saying that the output of PD1 may be used instead of the output of PD2.

Therefore, the toner amount is detected by using the ratio of the detection values only when the toner amount is at the high density level, and the toner amount is detected from the detection value itself of the light receiving element when the toner amount is at the medium or low density level. May be.

The toner on the photoconductor adheres in a coarse density state with a gap, and is crushed and becomes dense on the paper in the subsequent transfer and fixing processes. At this time, if the toner density is high, a density difference will appear on the paper after fixing, but there will be no difference in the output of the toner amount detection device, and the reflected light amount will be extremely small, so the signal will be buried in noise. Detection accuracy cannot be maintained.

Next, an example of a toner amount detecting device having improved detection sensitivity when the amount of toner on the photosensitive member is large will be described.

In this toner amount detecting device, a distribution type target whose density is expressed by halftone dots is used as a reference target. The distribution type target is one in which black dots and white dots are alternately arranged and represents an average halftone by the area ratio of black dots and white dots, and the density level of black dots and white dots is constant. This reference target may be provided as an image in the run-up section of the optical system, or may be set on the platen by the operator. Further, in a laser printer or the like, the reference target may be stored as image data, and this data may be read and formed on the photoconductor during the toner amount detection operation. The configuration of the toner amount detecting device using the distributed target is substantially the same as that of FIG. 2, but it is not necessary to use the wavelength resolving light receiving element, and an ordinary light receiving element such as a photodiode or a phototransistor may be used. The arrangement of the light source and the light receiving element is also the same as in FIG. 2, the path of the beam is in the plane including the long axis of the photosensitive drum, and the reflection angle is small. Further, it is desirable that the beam has an elliptical shape and its major axis is aligned with the major axis of the photosensitive drum.

The distributed reference target is composed of a pattern in which a black portion and a white portion having a constant density are arranged, and there are several possible patterns. Especially when the photoconductor is cylindrical, the direction of the pattern is significant. FIG. 6 shows an example of the pattern. The arrows in FIG. 6 represent the axial direction and the rotation direction of the photosensitive drum, respectively. Figure 6
In (A), the isolated dot-shaped white portion 51 is the black portion 50.
Are scattered (halftone dots), and the shape of the white portion 51 is a circle or a polygon. In (B), a black portion 50 and a white portion 51 are formed in stripes in a direction perpendicular to the axial direction of the photosensitive drum. In (C), a black portion 50 and a white portion 51 are formed in stripes in the horizontal direction with respect to the axial direction of the photosensitive drum. In (D), black portions 50 and white portions 51 are formed in stripes in the vertical and horizontal directions with respect to the axial direction of the photosensitive drum. In (E) and (F), a black portion 50 and a white portion 51 are formed in stripes in a direction (45 degrees) oblique to the axial direction of the photosensitive drum.

The electrophotographic copying machine using the photosensitive drum has the following features.

Normally, the photosensitive drum is rotated by transmitting the power of the motor through a gear or a belt, so that highly accurate rotation control cannot be realized and a pattern in the direction of rotation (for example, FIG. 6).
When the copy output of (C) is blurred or there is a boundary between the black portion and the white portion in the rotation direction (for example, FIG. 6C),
A phenomenon called an edge effect in which a black portion of a boundary is removed in white may occur. Since these occur when the uniformity of the rotation direction is poor, it is preferable to use the pattern of FIG. 6B. Alternatively, the black portion 50 and the white portion 51 may be exchanged. Also, due to the influence of the exposure distribution and uneven charging,
This is especially noticeable when the copy output in the axial direction becomes non-uniform and the photosensitive drum is scratched. In such a case, the pattern of FIG. 6C is suitable.

The pattern of FIG. 6D is a pattern provided with both of FIGS. 6B and 6C, and the output obtained from both patterns may be averaged.

FIGS. 6 (E) and 6 (F) have the averaging effect on the pattern itself, and FIG. 6 (A) shows a general pattern showing non-uniformity in the rotational direction and non-uniformity in the axial direction. Both can be affected.

The above patterns may be selectively used according to the state of the copying machine, and some patterns may be prepared in advance and used in combination.

FIG. 7 shows an adhered state (cross section) when the distributed target is exposed and the toner is developed on the photoconductor. Ideally, as shown in FIG. 7A, when the toner 30 adheres to a portion corresponding to a black dot (solid line) and the toner adhesion amount increases due to fluctuations in the developing bias voltage or the like, a dotted line is formed. Further, toner is attached on it. However, in reality, the toner does not stick in this way, but sticks in a trapezoidal shape as shown in FIG. 7B. Get fat. As described above, when the toner adhesion amount increases, the area where the photoconductor appears decreases. When the black and white dots are arranged at appropriate intervals, the toner covers the entire surface of the photoconductor 1 with a certain toner adhesion amount or more. Be seen.
There are two states, that is, the surface of the photoconductor appears and the surface does not appear before and after this adhesion amount, and a large output change can be obtained by catching these states with the toner amount detection device.

As described above, the present embodiment is effective in detecting toner at a high density level.

FIG. 8 shows an output example of the toner amount detecting device showing the effect of this embodiment. The horizontal axis represents the optical density after copying on the recording paper, and is specifically expressed by the following equation.

Copy output density = -log (I / I0) where I0 is the amount of incident light and I is the amount of reflected light. In order to maintain good copy output, it is necessary to control the characteristics of the photoconductor from 0.1 to 1.4 in terms of copy output density.
Shows an example of output when the copy output density is around 1.4. The white circles and the dotted lines show an output example of the conventional toner amount detection device, and it can be seen that the dispersion of the measurement points is large and the inclination of the output characteristic is small. On the other hand, the black circles and the solid lines show output examples according to the present embodiment, and it can be seen that output characteristics with a large inclination are obtained.

In order to obtain the output as shown by the solid line in FIG. 8, a target having a dot area of 200 to 120 dots per inch and a black area ratio of 80 to 60% is used as the reference target.

In this embodiment, only the distributed target is used as the reference target, so naturally it can be used in combination with the above-mentioned embodiment. At that time, a distributed type target and a solid target may be arranged side by side, and detected sequentially by the toner amount detecting device. Further, the present embodiment can be performed by using the output ratio from two light receiving elements (combined with the above-described embodiment), or can be performed by the output signal from one light receiving element.

Next, another application example of this embodiment will be described. An example of application to a digital copying machine using a scanned laser beam will be described. Although the distributed target is used as the reference target in this embodiment, the distributed target is not particularly used in the present adaptive example, and the laser beam is modulated and applied to the photosensitive member. As a result, a pattern as shown in FIG. Expose.
The latent image is similarly exposed by using a distributed target and formed on the photoconductor by modulation of the laser beam.

It is needless to say that the effects of this embodiment are the same in this application example, and that it is possible to easily form a distributed latent image and to have many types of patterns, which is an added advantage.

Next, the fact that the toner density on the photoconductor is within a certain density range is accurately detected by compensating for the fluctuation of the light quantity of the light source, the sensitivity change due to the temperature of the light receiving element, and the change of the light receiving quantity due to dirt. An example of a toner amount detecting device that can be used will be described.

FIG. 9 is a configuration diagram of the toner amount detecting device and the photoconductor 1 of this embodiment as viewed from above.

The toner amount detecting device comprises a light source 21, a light receiving element 25, a detecting circuit 23 and a reference density output device 40. The light source 21 and the light receiving element 25 are the same as those in FIG. 2, and the beam path is the length of the photosensitive drum. It is in the plane including the axis, and the reflection angle is small. Also, the shape of the beam is elliptical,
It is desirable to align the major axis with the major axis of the photosensitive drum.

FIG. 10 is a diagram showing the structure of the reference density output device 40. The reference density output device 40 is formed in a rectangular plate shape and has a through hole 42 in the center. On both sides of the through hole 42, reference density samples 41 and 43 that provide the same output as the output of the light receiving element 25 at a certain reference toner density are provided. The reference density output device 40 is movably provided as shown in FIG.
The light from the light source 21 is sometimes used as a reference concentration sample 41,
43, the reflected light is received by the light receiving element 25, and sometimes passes through the through hole 42 to hit the photoconductor 1, and the light receiving element 25 holds the toner density information on the photoconductor 1
Is received by. The toner amount detecting device detects the respective outputs of the light receiving element 25 obtained from the reflected light from the photoconductor 1 and the reflected light from the reference density samples 41 and 43.
The signal is amplified and shaped by 2 and transmitted to the control device 9.

The reference density samples 41 and 43 are set so that the arbitrary reference toner density to be accurately measured is an intermediate value, and the output obtained by the light receiving element 25 is also at a certain reference toner density. The output value of is obtained as an intermediate value. That is, the output obtained by receiving the light reflected by the photoconductor 1 and the reference density sample 4
By comparing the outputs obtained by receiving the light reflected from Nos. 1 and 43, it is possible to identify whether the toner density on the photoconductor 1 is within a certain reference density range.

By doing so, the toner density on the photoconductor 1 when the reference original (target) is placed is not affected by the change in the light emission amount of the light source 21 and the change in the sensitivity of the light receiving element 25. It can be controlled within the reference concentration range.

The reference concentration sample is made of plastic, paper, ceramics or the like, or the toner is fused or fixed with an adhesive, and two or more reference concentration ranges are set. It may be one.

Instead of moving the reference density sample, the optical path may be switched by a rotating (vibrating) mirror to obtain reflected light from the photoconductor and the reference density sample. An example thereof is shown in FIG. The rotating mirror 44 is inserted in the middle of the optical path to switch the optical path. When the rotating mirror is in the state of 44a, the light path of the light of the light source 22 is not switched and the light is applied to the photoconductor 1 and the reflected light is incident on the light receiving element 24. When the rotating mirror is in the state of 44b, the optical path is bent as shown by the dotted line and hits the reference sample 41, and the reflected light is incident on the light receiving element 24. Further, when the rotating mirror is at a certain angle, the optical path is bent as indicated by the alternate long and short dash line, the light beam strikes the reference sample 43, and the reflected light is incident on the light receiving element 24. At that time, it is effective that the reference concentration sample can be placed in a place where it is hard to get dirty (a place away from the photoconductor and the developing device).

This embodiment can also be used in combination with the above-mentioned two embodiments by using a wavelength resolving light receiving element as the light receiving element 25 and using a distributed target as the reference target.

[0061]

As described above in detail, according to the present invention, the light quantity of the light source and the sensitivity change due to the temperature of the light receiving element are changed by using the light in a plurality of wavelength regions and taking the ratio of the outputs respectively obtained. The amount of toner on the photoconductor can be detected without being affected by changes in the amount of received light due to dirt, etc., deterioration due to long-term use of the photoconductor, characteristic changes that are sensitive to ambient temperature and humidity, and characteristic changes during use. To ensure that you always get a high quality copy.

Further, by using a distributed target as the reference target, it is possible to detect a high density toner concentration, and thereby it is possible to control the characteristics of the photoconductor in a wide dynamic range. Even high quality copies can be maintained.

Further, by providing a sample from which the output at the reference density is obtained from the light receiving element and comparing it with the toner amount detection signal, the light amount fluctuation of the light source, the sensitivity change due to the temperature of the light receiving element, the received light amount change due to dirt, etc. It is possible to discriminate that the amount of toner on the photoconductor is within the reference density range without being affected by, and there is an effect that the copy output is always kept in high quality.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an electrophotographic copying machine.

FIG. 2 is a diagram showing a basic structure of a toner amount detection device according to an embodiment of the present invention.

FIG. 3 is a structural cross-sectional view of a color sensor used in the toner amount detection device.

FIG. 4 is a wavelength sensitivity characteristic diagram of the color sensor.

FIG. 5 is a diagram showing a result of an experiment using a double-junction type color sensor as a wavelength resolving light receiving element.

FIG. 6 is an example of a pattern of a distributed target used in the toner amount detecting device according to another embodiment of the present invention.

FIG. 7 is a diagram illustrating a basic principle of the toner amount detection device.

FIG. 8 is a characteristic diagram showing an output example of the toner amount detection device.

FIG. 9 is a diagram showing a configuration of a toner amount detecting device according to another embodiment of the present invention.

FIG. 10 is a view showing a structure of a reference density output device used in the toner amount detection device.

FIG. 11 is a diagram showing a configuration of a toner amount detecting device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 20 Toner amount detection device 21 Light source 22 Wavelength resolving light receiving element 25 Light receiving element 30 Toner 41 Reference density sample 43 Reference density sample 50 Black part 51 White part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor No ▲ Saki ▼ Kiyohiro 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Toshio Nomura 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka No. 22 SHARP Co., Ltd. (72) Inventor Nobuaki Kayoshi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Prefecture

Claims (7)

[Claims] 1. A light source for irradiating a photoreceptor, a wavelength resolving light receiving element for receiving reflected light from the photoreceptor in at least two wavelength distributions, and a reference image for giving a reference exposure to the photoreceptor. Means for detecting the amount of toner on the photosensitive member based on the ratio of the output values from the wavelength resolving light receiving element, and a toner amount detecting device. 2. The toner amount detecting device according to claim 1, wherein a double junction type semiconductor color sensor is used for the wavelength resolving light receiving element. 3. A light source for irradiating the photoconductor, a light receiving element for receiving the reflected light from the photoconductor, and a distribution type reference image formed on the surface of the photoconductor with a distribution of black and white regions of constant density. A toner amount detecting device, comprising: a reference image forming unit for controlling the amount of toner on the surface of the photosensitive member; 4. The reference image forming means is means for forming a distributed reference image in which the density of the black area and the white area is 200 to 120 dots per inch and the area ratio of the black area is 80% to 60%. The toner amount detecting device according to claim 3. 5. A light source for irradiating a photoconductor, a light receiving element for receiving reflected light from the photoconductor, a reference image forming means for giving a reference exposure to the photoconductor, and a light receiving element corresponding to a reference toner density. And a means for detecting the amount of toner on the photoconductor by comparing the signal of detecting the toner on the photoconductor by the light receiving element and the signal of detecting the reference density sample on the photoconductor. A toner amount detecting device characterized by the above. 6. The photoconductor has a cylindrical shape, and an optical path of a light beam from a light source to a wavelength resolution light receiving element or a light receiving element is in a plane including a long axis of the cylinder. 5. The toner amount detection device according to item 5. 7. The toner amount detecting device according to claim 6, wherein the shape of the light beam with which the photoconductor is irradiated is elliptical, and the major axis of the ellipse coincides with the major axis direction of the cylinder of the photoconductor.