JP2004074718A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner which is more inexpensive and capable of keeping the amount of light emission constant, by changing the amount of the emission of laser light without using a variable resistor. <P>SOLUTION: In this optical scanner for an electrophotographic process, the voltage of a laser diode 1 is varied by a fixed resistor Rkm and a D/A converter 18 when the light intensity of the laser diode 1 is set at a prescribed amount. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical scanning device as an electrophotographic process means.
[0002]
[Prior art]
It is common to use a variable resistor as a laser power adjustment method in an optical scanning device. For example, it is disclosed that a variable resistor is used in an adjustment portion as shown in FIG. 3 by a configuration as disclosed in Japanese Patent Application Laid-Open No. 9-69663.
[0003]
[Problems to be solved by the invention]
In an optical scanning device, the amount of light emitted from a single laser needs to be a predetermined amount in order to determine the energy of light applied to a photoconductor. However, this light emission amount has a difference in light emission current and a difference in divergence angle which the laser element itself has.
[0004]
In addition, there is a difference in monitor current to prevent a change in intensity during light emission, and there is also a difference caused by a lens or a mirror after light emission from a laser. There is a need to do.
[0005]
For this reason, the emission amount of the laser is obtained by changing the current flowing through the laser using a variable resistor as disclosed in Japanese Patent Application Laid-Open No. 9-69663.
[0006]
FIG. 3 is a schematic diagram showing a general optical scanning device. FIG. 4 is a schematic diagram showing the laser unit of FIG. 3 and 4, light emitted from the laser diode 1 of the laser unit A passes through a collimating lens 2 for obtaining parallelism and an aperture 3 for determining the size.
[0007]
Thereafter, the light passes through the cylinder lens 5 for condensing light, the polygon mirror 6, the lenses I7 and II8 for determining the uniformity and position of the beam, and reaches the photosensitive member 10. Depending on the arrangement of the optical path and the like, the angle of light may be changed by disposing the reflection mirror 9 and the like.
[0008]
At this time, the difference in the reflectance and transmittance of the lens and the mirror causes a change in the amount of emitted light reaching the photoreceptor 10. To absorb this change, the emission current of the laser diode 1 needs to be changed.
[0009]
On the other hand, even in the laser diode 1 alone, since there is an error in the optical output with respect to the current flowing through the laser diode 1, the current value required to flow through the laser diode 1 is different even if the same optical output is required. At the same time, the amount of light that can be effectively used varies depending on the spread of light emission of the laser diode 1, so that it is necessary to change the light emission current.
[0010]
Further, the laser generally includes a laser diode 1 for emitting light and a photodiode 1a for monitoring the light emission amount. The photodiode 1a receives light traveling in the opposite direction to the light traveling toward the photoreceptor 10 and outputs an output proportional to the amount of light emitted. The sensitivity also varies.
[0011]
As a method for changing the light emission amount, a method of attaching a variable resistor to the laser substrate 4 and determining a laser drive output and a monitor output for an appropriate light emission amount and executing the method is generally adopted.
[0012]
FIG. 5 is a control circuit diagram for controlling a potential by a monitor output in a general optical scanning device. As shown in FIG. 5, a current (monitor output) Im flowing through the photodiode 1a in the laser diode 1 is converted into a voltage value Vm by the variable resistor Rm and the differential amplifier 11.
[0013]
The laser diode 1 emits light by this voltage value and a reference voltage Vref generated by a PD (reference power supply 18) output corresponding to a desired light emission amount. The laser power supply is switched so that this state is always maintained, and the light emission amount during light emission is set to a predetermined amount so as to be always kept constant during the image light emission period.
[0014]
That is, the lighting control unit 13 operates as follows, using the reference voltage Vref generated by the variable resistor Rm and its voltage value Vm as a reference of the comparator 12.
[0015]
That is, when the output Vm of the photodiode 1a is larger than the reference voltage Vref, the drive power supply for the laser diode 1 is discharged (discharge power supply 14 / SW2) to lower the light output, and conversely, the output Vm of the photodiode 1a is reduced. When is smaller, the operation of charging the driving power supply (charging power supply 15 / SW1) to further increase the light output is repeated.
[0016]
Therefore, the variable resistor Rm that determines Vm generated by the differential amplifier 11 determines the light that reaches the photoconductor 10. Here, 16 is a switching power supply, and 17 is a bias power supply.
[0017]
However, in this technique, since it is necessary to attach the variable resistor Rm, there is a problem that the cost is increased and an adjustment time for setting the variable resistor Rm to an appropriate light emission amount occurs.
[0018]
Therefore, an object of the present invention is to provide an optical scanning device which is capable of constantly maintaining a constant light emission amount at a lower cost by performing the change in the light emission amount of the laser without using a variable resistor. It is in.
[0019]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the invention according to claim 1, in the optical scanning device as the electrophotographic process means, when the light intensity of the laser diode is set to a predetermined amount, the voltage of the laser diode is set to a fixed resistance. The most main feature is an optical scanning device that varies with a D / A converter.
[0020]
According to the second aspect of the present invention, when the light intensity of the laser diode is determined to be a predetermined amount of light emission by a light intensity detector, and the setting of the D / A converter is determined, the setting is determined by the predetermined amount. The optical scanning device according to claim 1, which is automatically determined by feeding back the power supply set value to the control unit, is a main feature.
[0021]
According to a third aspect of the present invention, the optical scanning device according to the second aspect uses an interface of the control unit to feed back the predetermined amount of light emission to the control unit.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the optical scanning device of the present invention. In the figure, portions which are not particularly relevant to the present invention and which are described in the control circuit in the general optical scanning device in FIG. 5 are denoted by the same reference numerals as those in FIG. 5 and their description is omitted.
[0023]
In FIG. 1, a laser power supply circuit reference power supply is a laser power supply voltage Vb generated by a D / A converter 18 for multi-value control of a main body control unit, and is used as a reference power supply of the comparator 12.
[0024]
The initial light emission amount is determined by the laser level power supply voltage Vb and the potential Vkm generated from the fixed resistor Rkm. This eliminates the need for the variable resistor Rm and means for changing the variable resistor.
[0025]
That is, if the initial light emission amount is higher than the predetermined light emission amount value, the laser level power supply Vb is reduced by using the D / A converter 18 to reduce the light emission amount. Conversely, if the light emission amount is smaller than the predetermined amount, the laser power supply level Vb is increased by using the D / A converter 18 to determine the light emission amount. This makes it possible to set a predetermined light emission amount only with a fixed resistor without using a conventional variable resistor.
[0026]
As means for determining the light emission amount, a light intensity detector 19 is disposed between the photoconductor and the optical scanning device. While rotating the polygon mirror described in the conventional apparatus, the laser diode 1 emits all light and enters the light intensity detector 19.
[0027]
It is ideal to select a fixed resistance value so that the laser level power supply Vb at this time becomes a value closer to the center. The digital initial value of the D / A converter 18 is also set near the center.
[0028]
Then, the polygon mirror is rotated while the laser diode 1 emits all light, and the light is stored in the light intensity detector 19. FIG. 2 is a flowchart of the light emission amount adjustment mode of the laser diode.
[0029]
In FIG. 2, the adjustment mode is set, the laser diode 1 is fully turned on, and the polygon mirror is rotated (S1). Next, the light emission amount data is collected (S3) assuming that there is a write synchronization signal (S2). It is determined whether or not the collected light emission amount data is within the light emission amount specification range (S4). If the data is within the specification range, the laser diode 1 is turned off, the polygon mirror is stopped (S5), and the adjustment mode ends.
[0030]
Further, it is determined whether or not the collected light emission amount data is within the light emission amount standard range (S4). If not, the output of the D / A converter 18 is reset (S6), and the light emission amount data is converted. Sampling (S3) is repeated until the collected light emission amount data falls within the light emission amount specification range. The digital output of the D / A converter 18 is varied according to the result of the light intensity detector 19 and is set to a predetermined value.
[0031]
The detection result of the light intensity detector 19 is fed back to the control unit 20 of the optical scanning device via an interface, for example, an input / output port such as a GP-IB or a serial port. From the difference in the light emission amount, a new digital setting value of the D / A converter 18 for setting the laser light emission amount is set.
[0032]
The amount of change in the amount of light emission in one byte can be predicted by using the gradation of the D / A converter 18 and the laser emission start current value (Ith) in this calculation. Becomes possible.
[0033]
When an analog amount proportional to the light detected by the light intensity detector 19 is output, the analog amount is input in parallel to an analog detection circuit (not shown) of the control unit 20, for example, a fixing thermistor temperature detection circuit. It is also possible to use a setting method that is used when setting the light emission amount.
[0034]
【The invention's effect】
As described above, according to the first aspect, a less expensive optical scanning device can be provided by adjusting only the D / A converter as the means for changing the laser emission intensity.
[0035]
According to the second and third aspects of the present invention, there is provided an optical scanning device capable of shortening the work by executing the light emission amount of the laser diode by the detection result of the light intensity detector and the calculation of the control unit of the optical scanning device. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of an optical scanning device according to the present invention.
FIG. 2 is a flowchart of a light emission amount adjustment mode of a laser diode.
FIG. 3 is a schematic view showing a general optical scanning device.
FIG. 4 is a schematic diagram illustrating the laser unit of FIG. 3;
FIG. 5 is a control circuit diagram for controlling a potential by a monitor output in a general optical scanning device.
[Explanation of symbols]
Reference Signs List 1 laser diode 18 D / A converter 19 light intensity detector 20 control unit Rkm fixed resistance

Claims (3)

In an optical scanning device as an electrophotographic process means, when the light intensity of the laser diode is set to a predetermined amount, the voltage of the laser diode is varied by a fixed resistor and a D / A converter. When the light intensity of the laser diode is determined to be a predetermined amount of light emission by a light intensity detector and the setting of the D / A converter is determined, the setting determination feeds back a predetermined amount of power supply set value to the control unit. 2. The optical scanning device according to claim 1, wherein the optical scanning device is automatically determined by performing the operation. The optical scanning device according to claim 2, wherein an interface of the control unit is used to feed back the predetermined amount of light emission to the control unit.

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