JPH08288581A - Method and apparatus for regulating output of light emitting element - Google Patents

Abstract

PURPOSE: To regulate the output of a light emitting element accurately regardless of fluctuation in the quantity of monitor output light. CONSTITUTION: The quantity of output light from a light emission element, i.e., a laser, is monitored by means of a power meter 6 and the drive signal or drive current for laser is controlled by subjecting a trimming resistor 8 to laser trimming thus regulating the quantity of monitor output light to a target value. More specifically, a correction value is determined as the regulation progresses by predicting the fluctuation in the quantity of monitor output light based on the quantity of monitor output light of laser and the regulation time thus controlling the quantity of monitor output light of laser to the correction value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the emission power of a light emitting element used as a light source for optical writing in an electrophotographic copying machine or printer, or a light emitting element used in an optical recording device such as a laser disk. The present invention relates to a light emitting element output adjusting method and an output adjusting apparatus for adjusting and controlling the light emitting element.

[0002]

2. Description of the Related Art In recent years, optical recording devices, such as laser printers, have been attracting attention because of their high quality, multi-gradation, and high-speed printing.

An electrophotographic recording device is also widely used. In this recording device, an image signal read by a scanner, an image signal obtained by communication, an image signal input from an external computer, and the like are used. The light emitting element drive signal is modulated by ON / OFF of the light emitting element, intensity, irradiation time pulse, and the like. As a light emitting element,
There are several methods, such as using LEDs instead of lasers.

By the way, a general electrophotographic recording apparatus has several processes centering on a photosensitive drum when forming an image. That is, first, in the cleaning step, the residual toner on the photosensitive drum during the previous printing is removed with a blade or the like. After that, in the pre-exposure step, the entire photoconductor drum is exposed to eliminate the residual electric charge in the previous printing. Next, in the primary charging step, the surface of the photosensitive drum is uniformly charged with a charging brush or charging roller.

In the exposure step, the uniformly charged photosensitive drum is exposed by irradiating it with a laser beam or the like modulated according to an image signal. At this time, the electric charge on the exposed portion charged on the photoconductor drum loses its potential due to the light energy, and becomes a current proportional to the exposure amount from the photoconductor drum and is discharged through the ground wire (drum ground wire). It As a result, there is a difference in the presence or absence of electric charges between the unexposed portion and the exposed portion on the surface of the photosensitive drum, and an electrostatic latent image is formed.

In the developing step, precharged toner is selectively placed on the electrostatic latent image. As a result, a toner image is formed on the photosensitive drum. The toner on the photoconductor drum is transferred to paper or the like in the transfer step and separated from the photoconductor drum in the separation step. Then, in the fixing step, the fixing roller and fixing film are fixed by heat and pressure.

Here, in a high-resolution recording apparatus, it is necessary to form a high-resolution latent image on a photosensitive drum, and in order to form such a high-resolution latent image, a semiconductor laser is used. It is necessary to reduce the beam diameter of.
The resolution of recent laser beam printers often exceeds 600 dpi, and in order to represent dots as latent images on the order of several tens of microns, many products have achieved the laser beam diameter on the order of several tens of microns. Is coming.

Further, in these recording apparatuses, in order to make the light emission amount of the light emitting element constant, a variable resistor is usually attached, and the light emission amount is monitored by using an opto-electric conversion element or the like, and the reference light emission amount is changed. Making adjustments. However, the conventional 2
In a multi-value printer or the like different from the value printer, the output light amount has a plurality of modes with different drive signals or drive currents, and a plurality of adjustments are required to realize stable multi-gradation. In general, you can switch the mode of the light emission state such as the mode of the minimum light emission amount, the mode of the maximum light emission amount,
Adjustments are made to achieve the optimum output determined in that mode.

As the adjustment becomes complicated and the quality and speed of the optical recording apparatus become higher, the precision required for the adjustment becomes stricter. To meet such demands, laser trimming technology has been used for this adjustment. This laser trimming technology replaces the conventional volume with a variable resistor such as a printing resistor that can be trimmed by laser.By changing the width of the printing resistor by irradiating the variable resistor part with laser from the trimming device. It changes the resistance value.

At this time, the amount of output light is monitored by using an opto-electric conversion element or the like, and laser trimming is performed until the output monitor value reaches a predetermined adjustment value for the mode for adjustment. Most of this series of laser trimming control is performed by a computer using an adjustment procedure program, and automatic adjustment is realized by this laser trimming technique, and high-speed adjustment is performed.

[0011]

However, in the conventional light emitting element output adjusting method and output adjusting apparatus,
Since the monitor output light amount of the light emitting element fluctuates, there is a problem that it is not possible to obtain an accurate light emission output.

In other words, the actual monitor output light quantity of the light emitting element fluctuates, though it is small, due to the transient characteristics having the time constant peculiar to the adjustment sequence until it becomes stable in time. This variation is largely due to the transient thermal characteristics of the device or unit, and is easily affected by the pre-use state of the device or unit, the temperature, and the like. Further, the drive circuit, device, unit, etc. of the light emitting element also have transient thermal characteristics, and further, the device (optical-electrical converter etc.) that monitors the output also has transient characteristics.

Recognition of this variation has not been given much importance so far. The reason is as follows:
In the recording device such as the value printer, the precision which is a problem for minute fluctuations was not required. Secondly, the conventional volume adjustment takes time to adjust, so the fluctuations after switching the mode can be adjusted. The point that was not a problem because it was stable around the time.

In the conventional laser trimming control, the adjustment value is generally fixed, and the laser trimming is continuously executed until the monitor output light amount reaches the target adjustment value. Even if affected, it cannot be corrected.

However, the influence of such fluctuations cannot be ignored if the performance of the apparatus is improved as described above and adjustments that are complicated and require precision are required. For example, when there is a variation as shown in FIGS. 8 and 9, at a time t3 and a time t4 assuming a normal volume adjustment time, when a certain device performs the adjustment at the time t3, the target adjustment is performed. There is an error of w3 from the value. Also,
When the adjustment time in another device is t4, the error of w4 corresponding to the time difference between the times of t3 and t4 is a difference between the devices as an error during adjustment.

The adjustment error due to the influence of such variations is
This is very problematic when performing automatic adjustment (laser trimming, etc.) that requires high accuracy at high speed. When automatic adjustment is performed at the time of t1 at the times of t1 and t2 assuming the adjustment time of laser trimming in FIGS. 8 and 9, an error of w1 from the target adjustment value occurs. If the automatic adjustment time in another device is t2, t1
The error of w2 corresponding to the time difference between the time of t2 and the time of t2 is a difference between the devices as an error during automatic adjustment.

The present invention has been made in view of the above problems, and the output adjustment of the light emitting element capable of obtaining the accurate light emission output even if the monitor output light amount of the light emitting element varies. It is an object to provide a method and an output adjusting device.

[0018]

A method for adjusting the output of a light emitting device according to the present invention is configured as follows.

(1) The output adjustment of the light emitting element in which the output light amount of the light emitting element is monitored by the monitor means and the monitor output is adjusted to a target value by controlling the drive signal or drive current of the light emitting element. In the method
The drive signal or drive current of the light emitting element is controlled based on the monitor output light amount of the light emitting element and the adjustment elapsed time.

(2) In the output adjusting method of the above (1), the drive signal or drive current of the light emitting element is controlled by laser trimming the trimable resistor.

(3) The output adjustment of the light emitting element in which the output light amount of the light emitting element is monitored by the monitor means, and the monitor output is adjusted to a target value by controlling the drive signal or drive current of the light emitting element. In the method
The drive signal or drive current of the light emitting element is controlled by laser trimming the trimmable resistance, and the trimming of the trimmable resistance is performed at least once by trimming the trimming resistance by changing the adjustment value.

(4) The output adjustment of the light emitting element in which the output light amount of the light emitting element is monitored by the monitoring means, and the monitor output is adjusted to the target value by controlling the drive signal or drive current of the light emitting element. In the method
The drive signal or drive current of the light emitting element is controlled by laser trimming a trimmable resistor, and while monitoring the monitor output light amount of the light emitting element and the adjustment elapsed time, the change in the monitor output light amount of the light emitting element is predicted to predict the variation. An adjustment correction value is obtained according to the adjustment elapsed time, and the adjustment value is changed at least once by laser trimming of the same portion of the trimmable resistor so that the monitor output light amount of the light emitting element is controlled to be the obtained adjustment correction value. I did it.

(5) In the output adjusting method of the above (4), the adjustment correction value for predicting the variation of the monitor output light amount of the light emitting element is approximate to the variation of the monitor output light amount of the light emitting element with the adjustment elapsed time as a variable. It was made to calculate using a formula.

(6) In the output adjusting method of the above (4), the adjustment correction value for predicting the fluctuation of the monitor output light amount of the light emitting element is obtained from the value of the correction value table corresponding to the adjustment elapsed time.

The output adjusting device of the light emitting device according to the present invention is constructed as follows.

(7) Monitor means for monitoring the output light quantity of the light emitting element, and control means for adjusting and controlling the monitor output of the monitor means to a target value by controlling the drive signal or drive current of the light emitting element. The control means controls the drive signal or drive current of the light emitting element based on the monitor output light amount of the light emitting element and the adjustment elapsed time.

(8) In the output adjusting device of the above (7), the control means controls the drive signal or drive current of the light emitting element by laser trimming the trimmable resistor.

[0028]

According to the present invention, in the recording apparatus, while monitoring the monitor output light amount of the light emitting element and the adjustment elapsed time, the fluctuation of the monitor output light amount of the light emitting element is predicted and the adjustment correction value according to the adjustment elapsed time is obtained. Then, adjustment is performed so that the monitor output light amount of the light emitting element becomes the adjustment correction value.

[0029]

(Embodiment 1) FIG. 1 is a configuration diagram of an output control device of a light emitting element according to the present invention. Here, a device for controlling a drive signal or a drive current of the light emitting element by laser trimming a trimmable resistor. Shows the configuration of.

The control computer 1 and the laser trimming device 2 are connected using an interface such as GP-IB, and these are also connected to the mode switching signal generator 3 so that any sequence can be freely performed. Has become.

The mode switching signal generator 3 sends a mode switching signal and a light emission signal to the laser unit 4. When this signal is input, the laser unit 4 drives the laser and detects the emitted output light amount as a monitor output by the power meter (monitor means) 6 inside the external light shielding box 5. This monitor output is input to the laser trimming device 2, where laser trimming is controlled, whereby the trimming laser irradiation unit 7 is driven and the trimming resistor 8 on the laser unit 4 is trimmed.

If the laser trimming device 2 itself has a control computer, it can be implemented without using the control computer 1. Further, the laser trimming is program-controlled by the control computer 1 or the laser trimming device 2. 9 is a power supply.

FIG. 2 is a diagram showing the overall construction of a laser printer having the laser unit 4. As described above, this laser printer has several image forming processes centering on the photosensitive drum.

That is, reference numeral 11 in the drawing denotes a photosensitive drum that rotates in the direction of the arrow. First, the cleaning unit 12 removes the residual toner on the photosensitive drum 11 during the previous printing with a blade or the like. After that, the pre-exposure lamp 1
The entire photoconductor drum 11 is exposed by 3 and the residual charge in the previous printing is removed.

Next, the primary charging device 14 uniformly charges the surface of the photosensitive drum with a charging brush or a charging roller. Then, in the exposure process, the uniformly charged photosensitive drum 11 is exposed by irradiating a laser beam modulated according to an image signal from a scanner unit 15 including the laser unit 4 of FIG. . At this time, the electric charge on the photoconductor drum 11 charged in the exposed portion loses its potential due to the light energy, and the photoconductor drum 1
A current proportional to the amount of exposure is generated from 1 and is discharged through the ground wire (drum ground wire). As a result, on the surface of the photosensitive drum 11, there is a difference in the presence or absence of electric charges (difference in drum surface potential) between the unexposed portion and the exposed portion, and an electrostatic latent image is formed.

Next, the precharged toner is selectively placed on the electrostatic latent image by the developing device 17. As a result, an image with toner is formed on the photosensitive drum 11. The toner on the photoconductor drum 11 is transferred to paper or the like by the transfer device 18, further separated from the photoconductor drum 11 by the separator 19, and fixed by heat and pressure of the fixing roller and the fixing film by the fixing device 20. It

FIG. 3 schematically shows the detailed structure of the optical system in the above exposure process. In the scanner unit 15 including the laser unit 4, the semiconductor laser (light emitting element) 22 fixed by the holder 21 is driven by the laser drive signal modulated according to the image signal by the laser drive circuit 23 and the laser modulation circuit 24. It The laser beam emitted from the semiconductor laser 22 passes through a collimator lens 25 and a cylindrical lens 26,
The light is deflected by a rotating polyhedron (polygon mirror) 28 rotated by a scanner motor 27, an image is formed by an FΘ lens 30 composed of a spherical lens 29 and a toric lens, and the photoconductor drum 11 is irradiated with the light through a reflection mirror 16.

The laser beam sequentially scans the photosensitive drum 11 at a constant speed at a predetermined timing in the main scanning direction and the sub scanning direction, whereby an electrostatic latent image is formed on the photosensitive drum 11. In addition, a part of the laser beam is reflected by the horizontal synchronizing mirror 31, and a synchronizing signal that determines the timing of the main scanning of the laser beam is generated by the photodiode 32.
Detected as a reference signal for each timing of the printer. In this way, by irradiating the pre-charged photoconductor drum 11 with the laser beam, the charge on the photoconductor drum 11 is removed and an electrostatic latent image is formed.

In such a laser printer, in order to regulate the light quantity of the laser, a normal automatic output control (hereinafter referred to as A
(Referred to as a PC). In addition, unlike the binary laser printer, in the multi-valued laser printer, the laser modulation circuit 24 of the laser unit 4 in FIG. Adjust the output of intermediate light intensity. Generally, this adjustment is performed by mounting a plurality of volumes.

However, recent laser printers employ a laser trimming technique for the above-mentioned volume adjustment part to adjust the APC and the laser modulator.
In this embodiment, this adjustment method is adopted, and this adjustment method is suitable for automatic adjustment such as laser trimming.
Adjustment using a volume may be used in this embodiment.

The laser trimming device 2 of FIG. 1 drives the semiconductor laser 22 based on the monitor output light amount of the light emitting element, that is, the monitor output light amount (laser beam output light amount) of the power meter 6 as the monitor means and the adjustment elapsed time. A control means for controlling a signal or a drive current is configured, and specifically, the trimming resistor 8 is laser-trimmed to adjust and control the output light amount of the light emitting element to a target value.

In this embodiment, the case where the variation of the output light quantity of the light emitting element can be approximated by a logarithmic function will be described as an example. That is, as shown in FIG. 7, when the variation of the monitor output light amount of the light emitting element has a logarithmic function characteristic, the monitor output light amount is expressed by the output light amount (t) = Alog (t + B) + C (1) Approximate with a function.

In the equation (1), A, B and C are arbitrary constants, which are determined according to the change curve of the monitor output light quantity. Further, t is the adjustment elapsed time, and the value of the output light amount is obtained with the passage of time. In FIG. 7, t1, t2, t
In the adjustment elapsed time of 3, the adjustment correction value is determined and adjusted so that the output light amount becomes the output light amount 1, the output light amount 2, and the output light amount 3.

As a result, no matter which adjustment point is adjusted,
Since the adjustment is performed on one characteristic curve, it is not affected by the fluctuation of the monitor output light amount of the light emitting element, and the adjustment accuracy can be significantly improved regardless of the adjustment elapsed time. According to this method, it is possible to deal with any variation characteristic by arbitrarily changing the approximate expression according to the variation characteristic of the monitor output light amount of the light emitting element.

FIG. 4 is a flow chart showing the operation of this embodiment according to the above method. First, at the same time when the adjustment is started (step S1), a timer for measuring the adjustment elapsed time is started (step S7). Then, the adjustment elapsed time is monitored by referring to the timer (step S2) (step S2).
8) During the monitoring, the adjustment correction value predicted from FIG. 7 is calculated (step S3), and laser trimming is started (step S4). When the laser trimming ends (step S5) and the timer ends (step S9), the output adjustment of the light emitting element ends (step S6).

Here, as is apparent from FIG. 4, in the program in the control computer 1 or the laser trimming device 2, a routine for the integrating timer is provided separately from the control routine for the laser trimming device 2 and before the adjustment is started. The elapsed time is measured from a certain point. In this embodiment, the monitor output light amount and the elapsed time of adjustment are monitored, and laser trimming is performed using these two parameters.

Further, the control routine of the laser trimming device 2 refers to the timer routine at the time of adjustment, obtains the adjustment correction value from the variation approximate function of the equation (1) programmed in advance from the elapsed time, and corrects it. Thus, the laser trimming device 2 is controlled.

The variation of the output light amount of the light emitting element can be approximated by a logarithmic function in most cases, but the above method can be similarly applied even when the variation may be approximated by another function. it can.

(Embodiment 2) As another embodiment, a correction table for predicting a variation in the monitor output light amount of the light emitting element is provided, and an adjustment correction value according to the adjustment elapsed time is obtained from the table, and the light emitting element The accuracy of the adjustment can be significantly improved without being affected by the change in the monitor output light quantity and regardless of the adjustment elapsed time.

FIG. 5 is a flow chart showing the operation of this embodiment using the above method. FIG. 6 shows an example of the contents of the correction table, in which correction value data corresponding to the adjustment elapsed time is shown.

In the flowchart of FIG. 5, the difference from FIG. 4 is the process of step S10 for calculating the adjustment correction value by referring to the correction table, and the other parts are the same as those of FIG. Further, the device configuration in this case is the same as that of the above-described embodiment, and therefore will be omitted.

In this embodiment, the control computer 1
Alternatively, a correction table that can be referred to by a program in the laser trimming device 2 is provided. The correction table shown in FIG. 6 stores correction data corresponding to the adjustment elapsed time by predicting the change in the monitor output light amount of the light emitting element.
Then, similar to the above-described embodiment, a routine for the integration timer is provided separately from the control routine for the laser trimming device 2,
The elapsed time is measured from a certain point of adjustment. The monitor output light quantity and the elapsed time of adjustment are monitored, and
Laser trimming is performed using three parameters.

Further, the control routine of the laser trimming device 2 refers to the correction data corresponding to the adjustment elapsed time while referring to the timer routine at the time of adjustment, obtains the adjustment correction value, and outputs the monitor output light amount of the light emitting element. The laser trimming device 2 is controlled so that is the adjusted correction value.
In this embodiment, this correction table exists in the memory as rewritable software, and the program of the correction table is rewritten and used according to the type of fluctuation of the monitor output light amount of the light emitting element to cope with all fluctuation characteristics. can do.

In each of the above embodiments, while monitoring the monitor output light amount of the light emitting element and the adjustment elapsed time,
Predict the change in the monitor output light amount of the light emitting element, obtain the adjustment correction value according to the adjustment elapsed time, change the laser trimming adjustment value at least once by laser trimming at the same location, and change the monitor output light amount of the light emitting element. You may make it adjust so that it may become the adjustment correction value.

[0055]

As described above, according to the present invention,
Since the drive signal or drive current of the light emitting element is controlled based on the monitor output light quantity of the light emitting element and the adjustment elapsed time, accurate light emission output can be obtained even if the monitor output light quantity of the light emitting element varies. The effect is that you can do it.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an output control device of a light emitting element according to the present invention.

FIG. 2 is a sectional view showing the overall configuration of a laser printer.

FIG. 3 is a perspective view schematically showing a configuration of an exposure optical system of a laser printer.

FIG. 4 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the second embodiment of the present invention.

FIG. 6 is a diagram showing an example of the contents of a correction table according to the second embodiment.

FIG. 7 is an explanatory diagram showing the contents of adjustment correction in each embodiment.

FIG. 8 is an explanatory diagram showing a variation example of the monitor output light amount.

FIG. 9 is an explanatory diagram showing a variation example of the monitor output light amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 control computer 2 laser trimming device (control means) 4 laser unit 6 trimming laser irradiation part 8 trimming resistor (trimmable resistor) 22 semiconductor laser (light emitting element) 23 laser drive circuit 24 laser modulation circuit

Claims (8)

[Claims] 1. A method for adjusting the output of a light emitting element, wherein the output light amount of the light emitting element is monitored by a monitor, and the monitor output is adjusted to a target value by controlling a drive signal or a drive current of the light emitting element. 2. A method for adjusting the output of a light emitting element, comprising controlling a drive signal or a drive current of the light emitting element based on the monitor output light amount of the light emitting element and the adjustment elapsed time. 2. A drive signal or drive current for a light emitting element,
2. The light emitting element output adjusting method according to claim 1, wherein the trimmable resistance is controlled by laser trimming. 3. A method for adjusting the output of a light emitting element, wherein the output light amount of the light emitting element is monitored by a monitor means, and the monitor output is adjusted to a target value by controlling a drive signal or drive current of the light emitting element. In the above, the drive signal or drive current of the light emitting element is controlled by laser trimming the trimmable resistor, and the laser trimming of the trimmable resistor is performed at least once by changing the adjustment value by trimming at the same position. And a method for adjusting the output of the light emitting element. 4. A method of adjusting the output of a light emitting element, wherein the output light amount of the light emitting element is monitored by a monitoring means, and the monitor output is adjusted to a target value by controlling the drive signal or drive current of the light emitting element. In the above, the drive signal or drive current of the light emitting element is controlled by laser trimming the trimmable resistor, and the variation of the monitor output light quantity of the light emitting element is predicted while monitoring the monitor output light quantity of the light emitting element and the adjustment elapsed time. Then, an adjustment correction value is obtained according to the adjustment elapsed time, and the adjustment value is changed at least once by laser trimming of the same portion of the trimmable resistor so that the monitor output light amount of the light emitting element becomes the obtained adjustment correction value. A method for adjusting the output of a light-emitting element, which comprises controlling. 5. The adjustment correction value for predicting the variation of the monitor output light amount of the light emitting element is calculated by using an approximate expression of the variation of the monitor output light amount of the light emitting element with the adjustment elapsed time as a variable. The output adjusting method of the light emitting device according to claim 4. 6. The light emitting element output adjusting method according to claim 4, wherein the adjustment correction value for predicting the variation of the monitor output light amount of the light emitting element is obtained from the value of the correction value table corresponding to the adjustment elapsed time. . 7. Monitor means for monitoring the output light amount of the light emitting element, and control means for adjusting and controlling the monitor output of this monitor means to a target value by controlling the drive signal or drive current of the light emitting element. The output adjusting device of the light emitting element, wherein the control means controls a drive signal or a drive current of the light emitting element based on the monitor output light amount of the light emitting element and the adjustment elapsed time. 8. The light emitting element output adjusting apparatus according to claim 7, wherein the control means controls the drive signal or drive current of the light emitting element by laser trimming the trimmable resistor.