JPH06242387A - Laser scanning optical system - Google Patents

Abstract

PURPOSE:To simplify initial adjustment and mending work and to unitize renewal parts in the case a failure occurs. CONSTITUTION:An LD 1, a collimator lens 2, an aperture unit 3 and an LD driving circuit 51 are mounted in an LED unit 50, and further a bar code display part 50a displaying the light passing rate of the unit 50 is installed in the unit 50. The light passing rate is the ratio of the light quantity of a laser beam projected from the LD unit 50 to a laser beam projected from the LD 1, and the light passing rate is set in a control part by the bar code scanner of the device main body not shown in figure. The control part sets a driving current to the LD 1 corresponding to the light passing rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scanning optical system applied to an image forming apparatus such as a laser printer, a digital copying machine and a laser facsimile.

[0002]

2. Description of the Related Art A laser scanning optical system is applied to a laser printer, for example, and scans a laser beam corresponding to image information on a photosensitive member to form an electrostatic latent image.

FIG. 5 is a perspective view showing a schematic structure of a conventional laser scanning optical system.

Reference numeral 1 is an LD (laser diode), 2 is a collimating lens, and 3 is an aperture unit whose aperture diameter is variably set.

A laser beam emitted from an LD (laser diode) 1 is collimated by a collimator lens 2 and is made redundant by an aperture unit 3 which is a beam diameter setting means for setting an aperture diameter corresponding to a pixel density. The laser beam is cut. The laser beam is condensed by the first cylinder lens 4 and scanned in the main scanning direction (X direction) by the polygon mirror 7 rotated by the polygon motor 6. Then, the pair of Fθ lenses 8 converts the equiangular movement into the constant velocity movement and corrects the field curvature.
The laser beam is reflected by the first mirror 9 and enters the second cylinder lens 10, is condensed in the sub-scanning direction (Y direction) by the second cylinder lens 10, and corresponds to the pixel density on the photosensitive drum 5. Project a light spot of diameter. The laser beam reflected by the polygon mirror 7 is incident on the PD (photodiode) 14 via the second mirror 11, the third cylinder lens 12 and the optical fiber 13.
The PD 14 outputs a detection signal to a CPU (Central Processing Unit), which will be described later, in synchronization with the laser beam incident timing, and the CPU starts image formation for each scanning in synchronization with the detection signal.

FIG. 6 is a block diagram showing the main part of the aperture unit.

Reference numeral 15 is an aperture plate in which a reference opening 15a is formed, and 16 is a plurality of openings 16a each having a different opening width W.
A shield plate formed with a shield 17 is an actuator that meshes with the rack portion 16b of the shield plate 16, and a position sensor 18 detects the position of the shield plate 16.

The laser beam passes through the reference opening 15a so that the beam diameter becomes the reference diameter, and the CPU, which will be described later, drives the actuator 17 to move the shielding plate 16 when the pixel density is changed. The position of the shielding plate 16 is detected by the position sensor 18, and the CPU detects the detection signal from the position sensor 18 so that the opening 16a having the opening width W corresponding to the pixel density matches the position of the reference opening 15a. To control the actuator 17. The laser beam that has passed through the opening 16a has a beam diameter corresponding to the pixel density.

FIG. 4 is a block diagram showing an example of a control unit in a conventional laser scanning optical system.

Reference numeral 41 is a CPU (central processing unit) that controls the entire apparatus, and 42 is a ROM (read / write unit) that stores control data.
Only memory), 43 is D / A (digital / analog)
A converter, 44 is a current control circuit, 45 is a driver for supplying a drive current to the LD 1, and 46 is a comparator.

The laser scanning optical system is subjected to initial adjustment so that the variable resistance element 48 has a reference resistance value before being mounted on an image forming apparatus such as a laser printer. At this time, C
The PU 41 outputs a digital control signal to the D / A converter 43 so that the drive current supplied from the driver 45 to the LD 1 gradually increases. The D / A converter 43 converts the digital control signal into an analog control signal and outputs the analog control signal to the current control circuit 44. The current control circuit 44 supplies a current corresponding to the analog control signal to the driver 45, and the driver 45 amplifies the current and supplies it to the LD 1 as a drive current. When the CPU 41 gradually increases the signal level of the digital control signal, the optical output of the laser beam emitted from the LD1 gradually increases. The light output of the laser beam emitted from the laser scanning optical system is monitored by a monitor device (not shown), and the monitor device outputs a reference light output detection signal to the CPU 41 at the timing when the light output reaches the reference light output value. Output to. The CPU 41 receives the reference light output detection signal and fixes the signal level of the digital control signal. At this time, a constant voltage is applied to the positive terminal of the comparator 46 by the constant voltage circuit 47, and the PD 14 generates a monitor voltage proportional to the optical output of the laser beam. The PD 14 is connected to the variable resistance element 48 and the negative terminal of the comparator 46. By increasing the resistance value of the variable resistance element 48, the PD 46 is connected to the comparator 46.
The monitor voltage applied to is boosted. Variable resistance element 48
Has a resistance value set to the minimum value before adjustment, and the resistance value is gradually increased with the laser beam reaching the reference light output value during adjustment. As a result, the monitor voltage from the PD 14 to the comparator 46 is gradually increased, and the comparator 46 inverts the output at the timing when the monitor voltage and the constant voltage become equal. At this timing, the resistance value of the variable resistance element 48 is fixed, and the initial adjustment is completed.

At the time of image formation, the CPU 41 controls the comparator 46
The laser beam can be held at the reference light output value by controlling the signal level of the digital control signal to the D / A converter 43 in accordance with the comparison signal from. Also,
When changing the reference light output value when changing the pixel density,
The U41 outputs a voltage setting signal to the constant voltage circuit 47 to change the control voltage applied to the comparator 46 by the constant voltage circuit 47.

[0013]

However, since the laser scanning optical system is a large unit, the adjustment jig for fixing the laser scanning optical system at the time of initial adjustment and measuring the light quantity is also large, There is a problem that the adjustment work is inefficient. Moreover, even if one member such as the LD1 fails in the constituent members, the entire laser scanning optical system must be replaced, and repair work is inefficient.
Moreover, since a member having no abnormality is also replaced, there arises a problem that the cost becomes high.

An object of the present invention is to provide a laser scanning optical system in which initial adjustment work and repair work are simplified and replacement parts at the time of failure are unitized.

[0015]

In order to solve the above problems in the present invention, a laser scanning optical system according to claim 1 comprises a laser diode for emitting a laser beam, and a driving means for driving the laser diode. In a laser scanning optical system including a collimator lens for collimating the laser beam and a beam diameter setting means for switching the aperture diameter of the aperture to set the beam diameter of the laser beam,
The laser diode, the driving means, the collimating lens, and the beam diameter setting means are configured as a single laser diode unit.

According to a second aspect of the present invention, there is provided a laser scanning optical system in which a laser diode for emitting a laser beam, a driving means for supplying a driving current to the laser diode, and a collimating lens for collimating the laser beam are provided. Beam diameter setting means for switching the aperture diameter of the aperture to set the beam diameter of the laser beam, light quantity detecting means for detecting the light quantity of the laser beam and outputting a monitor signal, and the driving means corresponding to the monitor signal. In contrast, in the laser scanning optical system including a control unit that sets the current value of the drive current, the laser diode, the driving unit, the collimator lens, and the beam diameter setting unit are configured as a single laser diode unit. And the control means outputs from the laser diode in the laser diode unit. In correspondence with the light amount ratio between the laser beam emitted from the laser beam and the laser diode unit which is characterized by correcting the current value.

According to a third aspect of the present invention, there is provided a laser scanning optical system in which a laser diode for emitting a laser beam, driving means for supplying a drive current to the laser diode, and a collimating lens for collimating the laser beam are provided. A beam diameter setting means for switching the aperture diameter of the aperture to set the beam diameter of the laser beam, a light quantity detecting means for detecting the light quantity of the laser beam and outputting a monitor signal, and comparing the monitor signal with a reference signal for comparison. A laser scanning optical system comprising: a comparison unit that outputs a signal; and a control unit that sets a current value of the drive current to the drive unit in accordance with the comparison signal, the laser diode, the drive unit, The collimator lens and the beam diameter setting means are configured as a single laser diode unit, and the control means , And sets the signal level of the reference signal in correspondence with the light amount ratio between the laser beam emitted from the laser beam and the laser diode unit which is emitted from the laser diode in the laser diode unit.

Further, in the laser scanning optical system according to a fourth aspect of the present invention, the laser diode unit is provided with a display section for displaying data corresponding to the light quantity ratio by a bar code, and the control means is a bar for reading the display section. It is characterized by having a code scanner.

[0019]

According to the laser scanning optical system of the first aspect, the laser beam emitted from the laser diode unit is generated by the laser diode unit composed of the laser diode, the driving means, the collimating lens and the beam diameter setting means. When initially adjusted to the reference light amount, the laser beam emitted from the laser scanning optical system is also adjusted to the reference light amount within the error range.

According to another aspect of the laser scanning optical system in the present invention, the laser diode unit and the control means for correcting the current value of the drive current set in the drive means corresponding to the light quantity ratio in the laser diode unit. With this, it is possible to control the laser beam emitted from the laser diode unit to the reference light amount without performing the initial adjustment for setting the current value of the drive current corresponding to the reference light amount.

According to the laser scanning optical system of the third aspect, the laser diode unit and the control means for setting the signal level of the reference signal in the comparison means in correspondence with the light quantity ratio in the laser diode unit. It is possible to control the laser beam emitted from the laser diode unit to the reference light amount without performing the initial adjustment for setting the initial value of the signal level of the monitor signal corresponding to the reference light amount.

Further, according to the laser scanning optical system of the fourth aspect, by the display section provided in the laser diode unit and the bar code scanner provided in the control means,
Bar code data corresponding to the light quantity ratio is displayed on the display section of the laser diode unit, and a read signal obtained by reading the display section is sent to the control means.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. In addition, in FIGS. 1 to 3, FIGS.
The members corresponding to the members described on the basis of FIG.

FIG. 1 is a perspective view showing an LD unit in one embodiment of the laser scanning optical system of the present invention.

The LD unit 50 includes an LD 1, a collimator lens 2, an aperture unit 3 and an LD drive circuit 51.
The LD drive circuit 51 includes a current control circuit 44 and a driver 45 which are integrated with each other. Also,
The LD unit 50 is provided with a bar code display section 50a on which a bar code read by a bar code scanner described later is printed.

In the present embodiment, the laser beam emitted from the LD unit 50 is measured by the monitor device and the initial adjustment is executed. Generally, the polygon mirror 7,
Cylinder lenses 4 and 10, Fθ lens 8 and mirror 9,
The light loss of the laser beam at 11 is slight. Therefore, even when the LD unit 50 that has been initially adjusted in advance is attached to the apparatus, the laser beam on the photoconductor drum 5 is controlled to the reference light output value within the error range.

Since the LD unit 50 is small in size with respect to the entire laser scanning optical system, the jig for initial adjustment of the LD unit 50 is also downsized, and the adjustment work is made efficient. Further, when the LD1 fails, the LD unit 50 may be replaced, so that the repair work is made efficient and the number of members to be replaced is reduced.

In the laser scanning optical system, the actuator 17 of the aperture unit 3 can be separated from the LD unit 50 and arranged on the laser scanning optical system body side. As a result, the number of constituent members can be reduced without affecting the optical characteristics of the LD unit 50 as a replacement part.

Next, the control of the control unit when the LD unit 50 is attached to the laser scanning optical system as a replacement part will be described.

FIG. 2 is a block diagram showing an example of the control unit in this embodiment.

In general, the laser beam emitted from the LD1 diverges in the shape of an elliptical cone as shown in FIG. this is,
This is because the laser beam spreads by diffraction because the light emitting region of the LD1 is very small. Further, the laser beam is emitted in the x and y directions of the virtual xy plane as shown in FIG.
The light intensity is distributed as shown in (A) and (B). The light intensity is
The distribution is similar to that of a Gaussian curve (normal distribution curve), and is horizontal (x direction) to the pn junction surface of the laser chip.
And the emission angle in the vertical direction (y direction) is different, and the emission angle in the vertical direction is relatively large. LD like this
The radiation characteristic of 1 is, for example, 1 / with respect to the light intensity of the optical axis L.
The divergence angles θx and θy of the laser beam, which are relative light intensities of 2, are used as parameters. Generally, the divergence angles θx and θy are
There are variations depending on the laser chip. Further, when comparing the light intensity on the optical axis L between the laser chips, FIG.
As shown in (A) and (B), the light intensities are different even if the drive current is the same.

From the above, even if the total amount of light emitted from the LD 1 is the same, the aperture unit 3 having the opening width W is formed.
If the LD unit 50 is different, the laser beam that has passed through will have a variation in the amount of light, as shown by the shaded areas in FIGS. 9 (A) and 9 (B). The initial adjustment of the LD unit 50 is to output the LD unit 50 to the input drive current.
This is for setting the current value of the drive current so that the light quantity of the laser beam is constant because there is a variation in the light quantity of the laser beam.

In the LD unit 50 of this embodiment, the amount of light emitted from the LD 1 and the amount of laser beam emitted from the LD unit 50 are measured in advance by a constant drive current,
The light transmission rate in the LD unit 50 is calculated. At this time, in the aperture unit 3, the position of the shielding plate 16 is set so that the laser beam passes through the reference opening 15a, and the emitted light amount is measured. Each measured LD unit 50
For the light transmittance of, the corresponding bar code is
It is printed on 50a.

The control unit of this embodiment is a bar code scanner 49.
The bar code scanner 49 reads the bar code display section 50a and sends a read signal to the CPU 61. When the LD unit 50 is attached to the device body, the resistance value of the variable resistance element 48 is fixed to a predetermined value in advance. At this time, the CPU 61 causes the LD unit to receive the read signal.
The voltage value of the control voltage applied to the comparator 46, which is a comparison means, by the constant voltage circuit 47 by outputting the voltage setting signal corresponding to the light transmittance to the constant voltage circuit 47. Is set according to the light transmission rate.

By setting the control voltage in accordance with the light transmission rate of the LD unit 50, the light amount of the laser beam emitted from the LD unit 50 can be controlled to be constant, so that initial adjustment becomes unnecessary and Compatibility as a replacement part for the LD unit 50 is ensured.

FIG. 3 is a block diagram showing another example of the control unit in this embodiment.

The resistance value of the variable resistance element 48 is fixed to a predetermined value in advance. In the PD 14, the detection signal is converted into a voltage signal by the variable resistance element 48, and the A / D converter 72 is used.
A monitor signal of a voltage corresponding to the light amount of LD1 is sent to. The A / D converter 72 converts the monitor signal into a digital signal and sends it to the CPU 71. The CPU 71 compares the signal level of the digitized monitor signal with the optical output setting reference level, and performs digital control on the D / A converter 43 based on the level difference between the signal level of the monitor signal and the optical output setting reference level. Change the signal level of the signal. Here, when the LD unit 50 is attached, the CPU 71 causes the barcode display section 50 to operate by the barcode scanner 49.
The light output setting reference level is set according to the light transmission rate of the LD unit 50 read from a. As a result, the light amount of the laser beam emitted from the LD unit 50 can be controlled to be constant, so that initial adjustment is unnecessary and compatibility as a replacement part of the LD unit 50 is ensured.

In the control section of FIG. 3, the voltage value of the control voltage for the comparator 46 is set in correspondence with the light transmission rate, and in the control section of FIG. 4, the light output setting is made in correspondence with the light transmission rate. Although the reference level is set, even if the control voltage or the light output setting reference level is fixed and the resistance value of the variable resistance element 48 is set in accordance with the light transmittance of the LD unit 50, the light is emitted from the LD unit 50. It is possible to control the light amount of the laser beam to be made constant.

[0039]

As described above, according to the laser scanning optical system of the first aspect, when the laser beam emitted from the laser diode unit is initially adjusted to be the reference light amount, the laser scanning optical system is operated. Since the emitted laser beam is adjusted to the reference light amount within the error range, the size of the laser diode unit is smaller than that in the case where the entire laser scanning optical system is initially adjusted, which facilitates the adjustment work. The adjustment jig can also be downsized.

Further, according to the laser scanning optical system of the second aspect, the laser beam emitted from the laser diode unit is adjusted without performing the initial adjustment for setting the current value of the drive current corresponding to the reference light amount. By making it possible to control to the reference light amount, the laser diode unit can be attached to the main body of the device without performing initial adjustment, so that compatibility of the laser diode unit can be secured as a replacement part, and Installation work and replacement work can be simplified.

According to the laser scanning optical system of the third aspect, the laser beam is emitted from the laser diode unit without performing the initial adjustment for setting the initial value of the signal level of the monitor signal corresponding to the reference light amount. Since it is possible to control the laser beam to the reference light intensity, the laser diode unit can be attached to the main body of the device without performing initial adjustment, ensuring compatibility of the laser diode unit as a replacement part. You can
Moreover, the installation work and the replacement work can be simplified.

Further, according to the laser scanning optical system of the fourth aspect, the bar code data corresponding to the light quantity ratio is displayed on the display part of the laser diode unit, and the read signal obtained by reading the display part is sent to the control means. By doing so, since the light quantity ratio of the laser diode unit can be easily input to the control means, the work of attaching the laser diode unit to the apparatus body can be simplified.

[Brief description of drawings]

FIG. 1 is a perspective view showing an LD unit in an embodiment of a laser scanning optical system of the present invention.

FIG. 2 is a block diagram showing an example of a control unit in this embodiment.

FIG. 3 is a block diagram showing another example of a control unit in the present embodiment.

FIG. 4 is a block diagram showing an example of a control unit in a conventional laser scanning optical system.

FIG. 5 is a perspective view showing a schematic configuration of a conventional laser scanning optical system.

FIG. 6 is a configuration diagram showing a main part of an aperture unit.

FIG. 7 is an explanatory diagram of radiation characteristics of a laser beam emitted from an LD.

FIG. 8 is a characteristic diagram showing a light intensity distribution of a laser beam emitted from an LD.

FIG. 9 is an explanatory diagram of a difference in laser beam emission characteristics due to an LD.

[Explanation of symbols]

1 ... LD (laser diode), 2 ... Collimating lens, 3 ... Aperture unit, 14 ... PD (photodiode), 46 ... Comparator, 49 ... Bar code scanner, 50 ... LD unit, 50a ... Bar code display section, 51 ... LD drive circuit, 61, 71 ... CPU (central processing unit).

Claims (4)

[Claims] 1. A laser diode for emitting a laser beam, a driving means for driving the laser diode, a collimating lens for collimating the laser beam, and an aperture diameter of an aperture to switch the beam diameter of the laser beam. In the laser scanning optical system including the beam diameter setting means, the laser scanning optical system, the laser diode, the driving means, the collimator lens, and the beam diameter setting means are configured as a single laser diode unit. system. 2. A laser diode for emitting a laser beam, a driving means for supplying a driving current to the laser diode, a collimating lens for making the laser beam parallel light, and an aperture diameter of an aperture for switching the laser beam beam. A beam diameter setting means for setting a diameter, a light amount detecting means for detecting a light amount of a laser beam and outputting a monitor signal, and a current value of the drive current for the drive means in correspondence with the monitor signal. In the laser scanning optical system including a control means, the laser diode, the driving means, the collimator lens, and the beam diameter setting means are configured as a single laser diode unit, and the control means includes the laser diode unit. Laser beam emitted from the laser diode in A laser scanning optical system characterized in that the current value is corrected in accordance with a light quantity ratio with a laser beam emitted from a unit. 3. A laser diode for emitting a laser beam, a driving means for supplying a driving current to the laser diode, a collimating lens for collimating the laser beam, and a beam of the laser beam by switching the aperture diameter of the aperture. Beam diameter setting means for setting a diameter, light quantity detecting means for detecting a light quantity of a laser beam and outputting a monitor signal, comparing means for comparing the monitor signal with a reference signal and outputting a comparison signal, and the comparison signal In the laser scanning optical system including a control means for setting the current value of the drive current to the drive means corresponding to the above, the laser diode, the drive means, the collimator lens, and the beam diameter setting means are united. One laser diode unit, and the control means is provided in the laser diode unit. A laser scanning optical system, wherein a signal level of the reference signal is set in correspondence with a light quantity ratio between a laser beam emitted from a laser diode and a laser beam emitted from a laser diode unit. 4. The laser diode unit is provided with a display section for displaying data corresponding to the light quantity ratio by a bar code, and the control means is provided with a bar code scanner for reading the display section. Item 2
Or the laser scanning optical system described in 3.