JPH09267514A - Image recorder and method for controlling density of the recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to stably measure the accurate density even when emitting light source wavelength is slightly changed by measuring the density of an image formed on the surface of a photosensitive drum and the drum surface, and correcting the density by considering the temperature change of the drum surface. SOLUTION: ΔV (LL) at low temperature and low humidity and ΔV (HH) at the ambient temperature and normal humidity are, for example, stored in a CPU as a table or calculation formula as the increment of the developing bias initial value Vbs corresponding to the ideal developing bias value to the contrast value to skin solid black, the bias value or correcting increment ΔVbs is obtained as the contrast value obtained by the developing bias initial value Vbs as an input, and the result is stored in a memory. In the normal printing sequence, the developing bias is corrected to be increased by using the obtained correction increment ΔVbs to make it possible to always stably regulate the density without environmental change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus for forming an image by an electrophotographic process and a density control method in the apparatus.

[0002]

2. Description of the Related Art Conventionally, in a monochrome printer or the like using an electrophotographic process, environmental characteristics are determined by the respective components (for example, output stability of a high-voltage unit, periodic replacement of a photosensitive drum, or cartridge formation, density for users. Environmental accuracy (for example,
Even if (temperature, humidity, atmospheric pressure, etc.) occurs, the design margin is set to be within an allowable range and the output image quality is guaranteed.

[0003]

However, although the output image quality of the above-described conventional monochromatic printer or the like can be guaranteed, the need for color printers has increased in recent years, and
Colors are also shifting from composite 7 colors to natural colors (full color), and even if the density (image quality) is guaranteed by the accuracy of each component as in the conventional single color printer, it is necessary to set the designated color accurately. is there.

Further, the parameters once set are also strongly affected by environmental fluctuations (for example, temperature, humidity, atmospheric pressure, sensor dirt, etc.), so that there is a problem that complicated switching is required each time.

The present invention has been made in view of the above-mentioned problems, and an object thereof is an image recording apparatus capable of contributing to the improvement of the image quality without lowering the output image quality even if the environment changes. And to provide a concentration control method in the apparatus.

[0006]

In order to achieve the above object, the present invention is an image recording apparatus for recording an image in an electrophotographic system using a photoconductor drum, wherein the photoconductor drum is provided with a light source. A first irradiating unit that irradiates an image formed by the above developer with light, a unit that detects the intensity of the first reflected light of the light irradiating from the first irradiating unit, and Second irradiating means for irradiating the background portion of the body drum on which the developer is not adhered, means for detecting the intensity of the second reflected light of the light emitted from the second irradiating means, Means for detecting the density of the image and the background portion based on the first reflected light and the second reflected light; means for determining the image forming condition of the image recording based on the detected density; And a means for detecting the temperature in the vicinity of the photosensitive drum, Irradiation wavelength of a light source according to one of the irradiation means may be replaced with the predicted value by the detected temperature, the value of the detected intensity of the reflected light from the background portion is changed by the irradiation wavelength was the replacement.

Another aspect of the present invention is a density control method in an image recording apparatus for recording an image by an electrophotographic method using a photoconductor drum, wherein a developing material on the photoconductor drum is used from a light source. Irradiation step of irradiating the image to be irradiated with light, a step of detecting the intensity of the first reflected light of the light irradiated in the first irradiation step, and a development on the photoconductor drum by a light source. A second irradiation step of irradiating the background portion to which no material adheres with light, a step of detecting the intensity of the second reflected light of the light irradiated in the second irradiation step, and the first reflected light And a step of detecting the density of the image and the background portion based on the second reflected light, a step of determining the image forming condition of the image recording based on the detected density, and the vicinity of the photosensitive drum. And a step of detecting the temperature of That irradiation wavelength of the light source, while being replaced by the predicted value by the detected temperature, the value of the detected intensity of the reflected light from the background portion is changed by the irradiation wavelength was the replacement.

[0008]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. [First Embodiment] FIG. 1 is a diagram showing a cross-sectional structure of an image recording apparatus according to a first embodiment of the present invention and a structure of a density control apparatus installed therein.

In FIG. 1, 1 is an electrophotographic color image forming unit, 2 is a photosensitive drum which receives a laser beam to form a latent image, and 3 is an image developed from the latent image. It is a transfer drum that transfers to paper. 4 is
The laser scanning unit emits an image signal with laser light.

Reference numeral 5 is a developing unit for yellow toner for developing a yellow latent image, 6 is a developing unit for cyan toner, 7 is a developing unit for magenta toner, and 8 is a developing unit for black toner. Is. 9
Is a density sensor unit for detecting the density of the image formed on the photosensitive drum 2, 10 is a detection circuit for the density sensor signal from the density sensor unit 9, and 11 is a reference for supplying a reference voltage to the signal detection circuit 10. It is a voltage circuit. Reference numeral 12 is a CPU (central control unit) that controls the entire apparatus.

Reference numeral 13 is a developing bias power source of the yellow developing unit 5, 14 is a developing bias power source of the cyan developing unit 6, 15 is a developing bias power source of the magenta developing unit 7, and 16 is a black developing unit 8. Of the developing bias power supply.

Next, the operation of the image recording apparatus having the above structure will be described.

Photosensitive drum 2 in color image forming section 1
Then, after being charged by a charger (not shown), a latent image is formed on the surface of the photosensitive drum 2 by the laser light emitted from the laser scanning unit 4. For example, when a yellow latent image is formed, the yellow developing bias power source 13 is activated, the developing bias of the yellow developing unit 5 is applied, and the yellow latent image is visualized by the toner. Then, the visualized toner image is transferred to the transfer drum 3
Is attracted by the transfer high-voltage power supply applied to
The image is transferred from the photosensitive drum 2 to the transfer drum 3.

By carrying out the above-described series of operations in the same manner for each color (yellow Y, magenta M, cyan C, black Bk), a color image is formed on the transfer drum 3, and then a transfer paper (not shown) is formed. ), It is fixed and printed out.

As is apparent from the series of print sequences described above, in the image recording apparatus, the print sequence for each color is independent, and therefore the image on the photoconductor drum 2 or the transfer drum 3 is detected by the density sensor. By measuring with 9, the toner density of each color can be detected. Then, using this detection result, by controlling the recording condition (here, bias) for each recording process,
It is possible to realize the toner formulation that provides the optimum image quality.

Therefore, in the present embodiment, the toner image transferred onto the photosensitive drum 2 is measured by the reflected light amount measuring system including the density sensor 9, and the density of each color toner is always stably combined.

Next, details of the concentration sensor section according to the present embodiment will be described.

FIG. 2 is a diagram showing the configuration of the reflected light detecting section of the density sensor section 9. In the figure, 50 is a light source, and 51 is
Is a light receiving element, which is arranged in a position close to the light source 50.
Reference numeral 2 denotes a light receiving element arranged at a position capable of receiving a part of the light of the light source 50, and receives reflected light from the photosensitive drum 2.

That is, the light source output from the light source 50 irradiates the photosensitive drum 2 and at the same time, a part of the light rays enter the light receiving element 51, while the photosensitive drum 2
When the upper toner image is irradiated with a part of the light rays, reflected (absorbed) light is generated in proportion to the density of the toner image, and the reflected light reaches the light receiving element 52. Therefore, here, basic concentration measurement is performed by amplifying and analyzing the level of the detection signal output from the light receiving element 52.

The amount of light emitted from the light source, for example, when the density is "1", is about 1/64 of the detected light amount when the density is "8". That is, when the detected light amount is photoelectrically converted and amplified, considering a signal voltage of 5 V as the maximum value,
The density "1" has a level of about 78 mV, and this voltage value is low in an ordinary electronic circuit, so that it is easily affected by noise.

Further, as shown in FIG. 1, the substrate on which the density sensor is mounted is close to the surface of the photosensitive drum 2 and
Since the measurement point is immediately after the development with the developing material, the most conceivable case is that it is arranged at a position far from the sequence control board on which the CPU 12 and the like are mounted. Therefore, the following points are taken into consideration in the present embodiment as the functions required for the substrate of the density sensor 9.

1) In order to reduce the influence of dark current generated in the light receiving element 52 such as a pin photodiode, the detection current of the light receiving element 51 is increased.

2) Since the recording density is expressed by a function (logarithm) of the value of the detected current, it is influenced by the size of the density by setting the circuit gain (detection value / Δdensity) fixed. Instead, the recording density is detected with a certain accuracy (error).

3) The density sensor 9 is strongly affected by dirt due to its mechanical layout. Therefore, the density sensor 9 is configured so that the detection value can be guaranteed even if it becomes dirty.

FIG. 3 shows a concentration sensor 9 having the above elements.
FIG. 3 is a block diagram showing the configuration of FIG. In FIG.
Is a diode terminal of the light source 50, 101 is a terminal pin photodiode (light receiving element 51) terminal for monitoring of the light source 50,
Reference numeral 102 is a reflected light measurement diode (light receiving element 52) terminal, and 103 is a voltage-current conversion amplifier, which converts the current input from the monitor pin photodiode terminal 101 into a voltage-current by a combination with a resistor 104.

Reference numeral 106 is a comparison amplifier, and 109 is a voltage-current converter that receives the output from the comparison amplifier 106 and controls the light source current of the light source 50. Also, 114
Is the output of the sensor board, and 115 is a DA (digital / analog) using a plurality of ladder resistors and switching elements.
It is a converter. Note that, for example, 116 is a code signal input terminal from the CPU.

Therefore, the operation of the present density sensor will be described.

In the above, three items of functions considered for the present density sensor are mentioned. The features are: 1) The light amount of the light source is detected by constantly feeding back the detection current to detect the light amount of the light source.

2) The feedback section is constructed on the sensor substrate, and the reference voltage is supplied from the outside in order to fix the circuit gain (detection value / Δconcentration).

3) Since the input-output relationship is always determined by the operation of the above-mentioned feedback section, it is sufficient to turn on only when measuring the light source, and it is possible to extend the life of the LED.

The circuit shown in FIG. 3 is configured to achieve the above three items. That is, the reflected photocurrent is
When it flows in from 1 and is input to the inverting input terminal of the voltage-current conversion amplifier 103, the voltage-current conversion amplifier 103 outputs a voltage equal to the product of the input current and the resistance 104. This voltage (reflected light voltage) is applied to the comparison amplifier 106, where phase correction and amplification are performed. At this time, the analog value DA-converted by the DA converter 115 based on the code signal received from the sequence control board (not shown) is input to the reference voltage side of the amplifier. The result of comparison and amplification as a voltage value is output.

The output resulting from the comparison and amplification with the reference voltage in the comparison amplifier 106 is converted into a current by the voltage-current conversion circuit 109, thereby driving the light source current of the light source 50. Through the above series of operations, the magnitude of the reflected light amount always becomes the value indicated by the code signal sent from the sequence control board.

Next, the light source current flows in from the terminal 102 and is output in the form of a voltage level by the current-voltage conversion circuit composed of the resistor 112 and the amplifier 113. That is, the magnitude of the reflected light voltage is instructed in advance by a code from the sequence control board (digital signal), and the light amount of the light source is monitored. Therefore, the detection level is the reflectance of the reference value (code instruction value). The output is the inverse multiple.
For this reason, it is possible to sense as a signal having a good S / N ratio in a high density region where the reflectance is particularly low, such as black toner.

In the case of obtaining the density from the reflectance, if the emission wavelength of the light emitting diode used as the light source is always stable, the measured value is always stable, but of course, the ambient environment of the device in which the sensor is arranged, The temperature inside the machine is not always constant, and the emission wavelength of the light emitting diode changes due to the temperature change of the light emitting diode of the concentration sensor.
As a result, the measurement accuracy of the present apparatus, which obtains the density by measuring the reflected light, deteriorates.

Therefore, the reflectance of the photosensitive drum changes due to this change of the emission wavelength, and as a result, the reflectance of the photosensitive drum which becomes the background changes. By calculation, it becomes necessary to correct the density detection sequence for obtaining the toner density.

In general, by using a color that most absorbs (sensitizes) the wavelength of the laser to the dielectric layer used on the photosensitive surface of the photosensitive drum used in electrophotography such as a printer, It controls the sensitivity of the body. Therefore, as for the spectral sensitivity of the photoconductor, one having high sensitivity (showing spectral absorption) in the vicinity of the irradiation wavelength is applied.

Therefore, in the present embodiment, regarding the relationship between the spectral sensitivity of the surface of the photosensitive drum and the emission wavelength of the light emitting diode of the light source used for the density sensor, the reflectance is always changed with respect to the emission wavelength from the temperature characteristics. Then, the reflectance data is corrected based on the obtained value, and accurate density measurement is performed.

4 to 6 are diagrams for explaining the concentration measuring operation (processing) in the present embodiment.

FIG. 4 is a diagram showing an example of the spectral sensitivity of the surface of the photosensitive drum. As shown in FIG. 4, the reflectance of infrared wavelengths emitted by the laser unit for writing a latent image is lowered, Further, it shows a characteristic that the reflectance becomes higher as the wavelength becomes shorter. On the other hand, FIG. 5 is a diagram showing the relationship between the emission wavelength of the light emitting diode used in the concentration measuring unit and the temperature characteristic. As shown in the figure, the emission wavelength and temperature characteristics are
The wavelength λ tends to increase as the temperature rises. For example, when the temperature range changes at room temperature by 25 to 50 degrees, the emission wavelength changes by about 5 nm.

FIG. 6 is a diagram for accurately relating the characteristics shown in FIGS. 4 and 5. In the figure, the sensor emission wavelength changes due to temperature change, and as a result, the reflectance of the photosensitive drum surface changes due to the change in wavelength.Therefore, there is an error in the density data from the reflectance data that was created in advance as the density reference. The phenomenon which causes is explained.

The above-mentioned phenomenon shows a remarkable wavelength characteristic especially on the surface of the photosensitive drum. However, depending on the type of toner and the characteristics of the light emitting diode, the same phenomenon as above is observed when the reflectance of the image visualized by the toner is measured. There is a possibility that it will be necessary to perform the correction processing of. Here, the description will be made by focusing on the photoconductor drum that exhibits its characteristics particularly remarkably in the 950 nm region.

In the color density detection process described later, since the color toner exhibits the characteristics of a reflector in the 950 nm region, the characteristic that the reflectance increases as the density increases is used.

Therefore, a sequence for performing concentration measurement using the concentration sensor according to this embodiment will be described.

FIG. 7 is a diagram schematically showing an example of a read patch (image) shape generated on the transfer drum 3 for recording density correction prior to overall printing.

Approximately 800 to 1 which is the emission wavelength range of the LED
In the 000 nm region, when the patch shown in FIG. 7 is black toner, it shows light absorption, and when it is color toner, it shows reflection. Therefore, since the characteristics are different, the density control processing corresponding to monochrome printing and color printing is performed.

8 to 12 are flowcharts showing the procedure of the density control processing according to the present embodiment. When the CPU which executes the control shown in FIGS. 8 to 12 enters the density processing shown in FIG. 8, if the recording is color processing (step S1).
If YES in step S10, the color measurement parameter is set, and if the recording is (white /) black processing (NO in step S10),
The black measurement parameters are set in the registers (steps S20 and S25). Then, the image recording apparatus sets the developing bias to the value Vbs for sampling and starts the printing sequence (step S30).

If the recording is color processing, in step S26 before the processing in step S30,
A measurement wavelength correction process described later is performed.

When the patch of black toner is rotated, there is a background in the direction of rotation of the photosensitive drum, that is, a region where toner is not attached, and then solid black is arranged (see FIG. 7). Therefore, first, the process of step S40, that is,
The density sensor 9 performs the background measurement process (base measurement) shown in FIG.

In this background measurement, first, a value of Vref1 having a low reflectance is set as the background reference voltage (step S100). Then, the light source 50 is raised to the reciprocal multiple of the reflectance by the above-described feedback function and is output, so that the Irb is read (step S110). Then, in the following step S120, the background timeout is determined, and until the timeout occurs,
The light source reading process in step S110 is performed.

Next, at the solid black patch timing,
The density sensor 9 performs the patch measurement process in step S50 of FIG. Specifically, in the patch measurement process shown in FIG. 11, Vref2 having a low reflectance is used as the reference voltage.
Is set (step S200), and the light source level Isb is read in the same manner as in the background processing described above (step S210).
Then, in step S220, a patch time-out is determined, and the light source reading process described above is executed until the time-out ends.

Vref1, Ir thus obtained
The relationship between the values of b, Vref2, Isb and the background density, and the density at the time of solid black detection is expressed by the following equation.

Now, the background density is Du and the solid black processing density is D.
Assuming that t, the background detection signal by the light amount light source control method is: Irb = Vref1 / 10- (Du) (1) The signal detected for solid black is Isb = Vref2 / 10- (Du + Dt). The signal expressed by (2) and multiplied by the reference voltage by the reciprocal of the reflectance is
Each is output.

Therefore, the contrast of solid black processing with respect to the background is obtained from the above two equations: contrast = 10 (Dt + Du) -10 (Du) = (Irb / Vref1) / (Isb / Vref2) = (Irb / Isb ) × (Vref2 / Vref1) (3) Further, in the density difference display, ΔD = log (Irb / Isb) -log (Vref1 / Vref2) (4).

In this embodiment, using these equations,
Find the contrast value.

FIG. 13 is a diagram showing the relationship between the contrast value and the developing bias which is a control parameter. In the figure, the horizontal axis represents the density input (developing bias) value, the vertical axis represents the density or the sensor output, and the curve A represents the developing characteristics at room temperature as an abstract model. On the other hand, the curve B on the upper side (high concentration side) shows the characteristics on the high temperature and high humidity side. Furthermore, the curve C on the lower side (low concentration side) shows the characteristics of low temperature and low humidity as an abstract model.

FIG. 17 is a diagram showing another example of the relationship between the contrast value and the developing bias.

FIG. 14 is a diagram showing, as an abstract model, a curve of the influence of the image density due to the difference in the developing bias, and a plurality of patterns of the variation due to the environment. As shown in (A) to (F) of the same figure, the environmental change is affected by changing the developing bias. Therefore,
It is possible (controllable) to correct the density by the developing bias.

In the graph shown in FIG. 13, the levels detected by the preset developing bias initial value Vbs are C (LL) at low temperature and low humidity, C (NN) at normal temperature and normal humidity, and at high temperature and high humidity, respectively. It is expressed as C (HH).

In the present density control processing, the developing bias initial value Vbs corresponding to the ideal developing bias value (for example, the developing bias obtained at the density of 1.6) with respect to the contrast value of the background with the solid black is obtained. The amount of increase is, for example, ΔV (LL) at low temperature and low humidity, and ΔV (H at normal temperature and normal humidity.
H) in advance as a table or calculation formula
Then, the bias value (or the correction increase ΔVbs) is obtained by inputting the contrast value obtained by the developing bias initial value Vbs, and the result is stored in the memory (step 60 in FIG. 8).

That is, in the bias correction value processing shown in FIG. 12, it is determined in step S290 whether or not the recording is color processing, and if it is color, the contrast based on the light source light amount ISB in step 305 is obtained, and the color is calculated. If not, in step S300, the contrast of solid black processing with respect to the background is obtained. Then, in step S310, the obtained contrast is stored in the table.

In the normal printing sequence, the correction increase amount ΔVbs obtained as described above is used to increase the correction of the developing bias, thereby making it possible to always perform stable density adjustment without environmental fluctuations.

Next, the color toner density detection processing will be described.

The color toner is a curve in which the above-mentioned reflection characteristic increases, and if the well-known characteristic is expressed, D = klog (I0 / (I0-Ir)) (5) or the relation of the detection voltage In this case, Ir = I0 {1-10 ^ (-D / k)} (6) (where ^ means exponentiation).

From the above relationship, in the measurement of color density,
In terms of light absorptance, I0 / Ir = α × exp (Db) = k × {1 / (1-exp- (Dd + Dc))} (7), and in reflectance, Ir / I0 = {1 -Exp-((Dd + Dc) / k)} (8). Here, I0: irradiation light source light amount Ir: reflected light amount Db: black toner density Dd: drum surface density Dc: color density k: proportional coefficient of reflectance and density D

Therefore, the reference density Dd is given, the detection value Ir obtained at that time is set as the density "0", and then the detection voltage is detected according to the above expression by superimposing the color toners. Here, with respect to the count k which relates the density and the absorptance, kt: Proportional count of the reflectance and the density D at the wavelength of 950 nm → depends on each color toner kp: is there.

In the present embodiment, based on the above definition,
The measurement wavelength correction process in step S26 of FIG. 8 is performed. That is, in the measurement wavelength correction process whose details are shown in FIG. 9, in step S1, the temperature measurement value near the light source is obtained by a thermometer (not shown), and in step S2, the emission wavelength is estimated (data input in advance). Then, the amount of change in reflectance corresponding to the wavelength is obtained, and the reciprocal of the amount of change is output as a coefficient (kp).

As described above, in the color toner, the right side of the above equation is a system including addition and exponent, so that the division cancel processing cannot be easily established. Therefore, when the light source I0 is irradiated onto the photoconductor drum whose reflectance is known and density is known, and the reflected light Id at that time is detected, I0 = Id × exp (Dd) using the above kp value. / Kp (9) holds, and I0 corresponding to the light source light amount in the measurement system is satisfied.
Can be obtained from the photoconductor absorption rate. Then, by inputting the obtained I0 into the above formula of color density to complete it, the following is obtained.

Ir = Id × exp (Db) × {1-exp− (Dc / k)} (10) Or, Dc = klog {I0 / (I0-Ir)} = klog {Ir × exp (Db) / (Ir × exp (Db) -Ir)} (11) As a result, the parameter (I0, Dd) for color density measurement is initially determined by the reflection data from the photosensitive drum, and the obtained formula is used. Perform color measurement.

In the above example, by introducing the coefficient kp, the relationship between the reflectance of the surface of the photosensitive drum and the known density is used,
Even when the temperature of the emission wavelength changes, the light source light quantity I
It is designed to estimate 0 and perform more accurate concentration measurement. Although not mentioned here, depending on the wavelength, if the region is affected by the spectral sensitivity characteristics of the color toner, it is necessary to apply the above rule to the constant on the detection side of the toner image. It is possible to come.

In the present embodiment, the proportional count k of the above equation
By introducing the toner count and the corrected reflectance of the wavelength change Δλ of the measurement light source due to the above temperature into
The color density is made more accurate.

As described above, according to the present embodiment, the change in reflectance corresponding to the temperature data detected by the temperature sensor is immediately predicted, and the development bias is increased to correct the change in temperature. Even if the wavelength of the light emission source of the sensor changes due to the environmental change of (3), stable concentration adjustment is always possible.

By correcting the influence of the next light emission wavelength of the light source of the sensor and detecting the density with high accuracy, it is possible to accurately perform color balance especially in low density. [Second Embodiment] A second embodiment according to the present invention will be described below.

In the present embodiment, the guarantee of the spectral sensitivity of the photosensitive member and the guarantee of the spectral sensitivity of each color of the developer toner are ensured in accordance with the change of the wavelength of the emission light source, that is, the temperature change of the LED. is there.

Since the basic principle of the image recording apparatus according to the present embodiment is the same as that of the apparatus according to the first embodiment, its explanation is omitted here.

FIG. 15 is a diagram showing an example of the spectral sensitivity of each color (Y, M, C, BK) color toner. Here, the observation wavelength and the reflection are matched with the characteristics of the spectral sensitivity shown in FIG. Correct the rate relationship. Further, FIG. 16 is a flowchart showing a processing procedure for obtaining the bias correction according to the present embodiment.

In the control sequence according to the present embodiment, after performing the background measurement shown in the above-mentioned first embodiment,
The wavelength correction of the color toner described below is performed.

That is, when the density control processing is started, in the case of color processing, the color parameter and the developing bias initial value are set in the register and the image forming unit (high voltage unit, etc.).
Set to. Then, according to the set parameters, first, the background measurement is performed. In this background measurement, since the reflectance is corrected by the wavelength correction process of the photoconductor described above, it is possible to accurately calculate the light source light amount.

After that, in the measurement of the patch portion, the sensitivity correction is performed by the same method as the measurement of the background (photoconductor), that is, from the spectral sensitivity value shown in FIG. Here, the method of performing the sensitivity correction is to detect and monitor the background reflected light detected by the photoconductor base, and from the detected voltage, Ir = Id × exp (Db) × (1-exp− (Dc / k) ) (12) or Dc = kc × log (I0 / (I0-Ir)) = kc × log (Ir × exp (Db) / (Ir × exp (Db) -Ir)) (13) .

Here, Kc is a proportional constant of the reflectance and the toner concentration at the saturation density of each toner, and when the emission wavelength of the reflectance measuring light source changes with temperature, the reflectance changes. , Is a constant that is determined in advance based on the measured temperature value so as to correct the reflectance of the wavelength change with respect to the temperature change.

If the spectral sensitivity of the material whose concentration is to be measured is known by the detection processing of such a configuration, even if the emission wavelength (measurement wavelength) changes due to the temperature of the light source,
With the above configuration, it is possible to perform measurement with the error minimized.

Even when the present invention is applied to a system composed of a plurality of devices (eg, host computer, interface device, reader, printer, etc.), a device composed of one device (eg, copying machine, (For example, a facsimile machine).

Another object of the present invention is to supply a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and to supply a computer (or CP) of the system or apparatus.
U and MPU) read out and execute the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD
-R, magnetic tape, non-volatile memory card, ROM, etc. can be used.

Further, by executing the program code read by the computer, not only the functions of the above-described embodiment are realized, but also the OS (operating system) running on the computer based on the instruction of the program code. It goes without saying that this also includes the case where the above) performs a part or all of the actual processing and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written in the memory provided in the function expansion board inserted into the computer or the function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that a case where the CPU or the like included in the function expansion board or the function expansion unit performs some or all of the actual processing and the processing realizes the functions of the above-described embodiments is also included.

[0087]

As described above, according to the present invention,
By measuring the density of the surface of the photoconductor drum and the image formed on the surface of the drum and correcting the density by taking into account the temperature change of the drum surface, stable high accuracy is achieved even when the wavelength of the light source is slightly changed. Can be measured, and as a result, it is not necessary to use an expensive LED light source.

[0088]

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional configuration of an image recording apparatus according to a first embodiment of the present invention and a configuration of a density control apparatus installed therein.

FIG. 2 is a diagram showing a configuration of a reflected light detection unit of a density sensor unit 9.

FIG. 3 is a block diagram showing a configuration of a density sensor 9.

FIG. 4 is a diagram showing an example of spectral sensitivity of a surface of a photosensitive drum.

FIG. 5 is a diagram showing a relationship between a light emission wavelength and a temperature characteristic of a light emitting diode used in the concentration measuring unit.

FIG. 6 is a diagram for accurately relating the characteristics shown in FIGS. 4 and 5;

[FIG. 7] Prior to overall printing, for recording density correction,
Read patch (image) generated on the transfer drum 3
It is a figure which shows an example of a shape typically.

FIG. 8 is a flowchart showing a procedure of density control processing according to the embodiment.

FIG. 9 is a flowchart showing a procedure of density control processing according to the embodiment.

FIG. 10 is a flowchart showing a procedure of density control processing according to the embodiment.

FIG. 11 is a flowchart showing a procedure of density control processing according to the embodiment.

FIG. 12 is a flowchart showing a procedure of density control processing according to the embodiment.

FIG. 13 is a diagram showing a relationship between a contrast value and a developing bias.

FIG. 14 is a diagram showing, as an abstract model, a curve of an influence of image density due to a difference in developing bias and a plurality of patterns of variation due to environment.

FIG. 15 is a diagram showing an example of spectral sensitivity of color toners of respective colors (Y, M, C, BK).

FIG. 16 is a flowchart showing a processing procedure for obtaining bias correction according to the second embodiment.

FIG. 17 is a diagram showing another example of the relationship between the contrast value and the developing bias.

[Explanation of symbols]

 1 Color Image Forming Section 2 Photosensitive Drum 3 Transfer Body Drum 4 Laser Scanning Unit 5 Developing Unit for Yellow Toner 6 Developing Unit for Cyan Toner 7 Developing Unit for Magenta Toner 8 Developing Unit for Black Toner 9 Density Sensor 10 Density sensor signal detection circuit 11 Reference voltage circuit 12 CPU (central control unit) 13 Development bias power supply for yellow development unit 14 Development bias power supply for cyan development unit 15 Development bias power supply for magenta development unit 16 Development bias power supply for black development unit 50 Light source 51,52 Light receiving element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 15/01 113 B41J 3/21 L 15/08 115

Claims (8)

[Claims] 1. An image recording apparatus for recording an image by an electrophotographic method using a photoconductor drum, wherein first light is emitted from a light source to an image formed of a developing material on the photoconductor drum. A means for detecting the intensity of the first reflected light of the light emitted from the first irradiation means, and a light source for irradiating the background portion of the photosensitive drum on which the developer is not adhered with light. 2 irradiation means, a means for detecting the intensity of the second reflected light of the light emitted from the second irradiation means, and the image based on the first reflected light and the second reflected light And a means for detecting the density of the background portion, a means for determining the image forming condition of the image recording based on the detected density, and a means for detecting the temperature in the vicinity of the photosensitive drum, The irradiation wavelength of the light source related to the irradiation means is Were together is replaced with the predicted value by the temperature, the image recording apparatus, characterized in that the value of the detected intensity of the reflected light from the background portion at irradiation wavelength was the substitution is changed. 2. The image recording apparatus according to claim 1, wherein the image forming condition is determined by correcting the detected density. 3. The developing material is a Y, M, C, BK color developing material, and the density of the image is detected by considering the reflectance of the color developing material. The image recording apparatus according to claim 1. 4. The image recording apparatus according to claim 3, wherein the detection of the density of the image uses a measurement wavelength in a 950 nm region. 5. The image recording apparatus according to claim 1, wherein the intensities of the first reflected light and the second reflected light are detected by a pin photodiode. 6. The light source is an LED (light emitting dice).
The image recording apparatus according to claim 1, further comprising an ode). 7. The density and temperature of the image are detected by a density sensor and a temperature sensor, respectively, and the density sensor and the temperature sensor are mounted on the same substrate. The image recording apparatus described. 8. A density control method in an image recording apparatus for recording an image in an electrophotographic system using a photosensitive drum, wherein light is emitted from a light source to an image formed of a developing material on the photosensitive drum. A first irradiation step of irradiating, a step of detecting the intensity of the first reflected light of the light irradiated in the first irradiation step, and a background from which the developer on the photosensitive drum does not adhere, from the light source A second irradiation step of irradiating a part with light, a step of detecting the intensity of the second reflected light of the light irradiated in the second irradiation step, the first reflected light and the second reflected light Detecting the density of the image and the background portion based on light; determining the image forming condition of the image recording based on the detected density; and detecting the temperature in the vicinity of the photoconductor drum. And a step of illuminating the light source according to the first irradiation step. Wavelength, while being replaced by the predicted value by the detected temperature, density control method characterized in that the value of the detected intensity of the reflected light from the background portion at irradiation wavelength was the substitution is changed.