JPH10213771A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily change a light quantity variable range by providing a light quantity changeover means changing over the light quantity variable range of a laser diode(LD) in accordance with resolution changed over. SOLUTION: A dual LD(DLD) outputs two light beams whose projection angles are different in a subscanning direction from two LD current driving elements(LDD). A resolution changeover switch 140 outputs a resolution changeover signal to execute the changeover of the resolution by specified operation to a controller. The controller is provided with a light quantity changeover circuit 142 changing over the quantity of the outputted beam in accordance with the resolution changeover signal. The circuit 142 is constituted of a PD light quantity control part 118 and a light quantity control circuit 120. The number of the light beams of the LD is changed over in accordance with the changeover of the resolution, and the light quantity variable range of the LD is changed over by the circuit 142 in accordance with the resolution changed over.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly to an optical scanning device that irradiates a photosensitive material while scanning a light beam corresponding to input data.

[0002]

2. Description of the Related Art Conventionally, laser light of one light source (hereinafter, Single B)
In an optical scanning device according to the above-described method, laser light is generally deflected by a polygon mirror that rotates at high speed by rotation of a driving unit such as a scanner motor, and irradiates the photosensitive material while scanning. In such an optical scanning device, the resolution has been switched without lowering the processing capability by switching the rotation speed of the scanner motor in accordance with the resolution. Such a Single
A laser diode (hereinafter abbreviated as LD) that outputs a beam is called a single beam LD.

On the other hand, demands for higher speed and higher resolution in recent years have not been met by increasing the speed of the scanner motor. Therefore, a method of irradiating a plurality of laser beams simultaneously in one scanning period has been proposed. The LD capable of simultaneously outputting a plurality of laser beams is provided with a plurality of LD chips, and a plurality of laser beams (hereinafter, abbreviated as Multi Beam) can be output by turning on the plurality of LD chips. . Such an LD capable of lighting a plurality of LD chips is called a Multi Beam LD. However, MultiBeamL
When the resolution is switched using D, the desired resolution cannot be obtained only by changing the rotation speed of the scanner motor, because the arrangement interval of the LD chips is constant. In order to solve this, it is necessary to switch the number of laser beams to be irradiated to a plurality / single.

Japanese Patent Application Laid-Open No. 1-299042 discloses a resolution switching patent relating to a Multi Beam LD. In the image forming apparatus according to this patent, when switching the scanning density, the number of laser light sources to be used is switched. This makes it possible to switch the plurality of laser emission sources in accordance with the scanning density and suppress the number of rotations of the polygon mirror to 10,000 or less. Accordingly, it is possible to prevent the polygon mirror and the scanner motor from increasing in cost, and to reduce the size.

[0005] Generally, the required light quantity of the photosensitive material per unit time is determined by the product of the process speed and the scan length. Since the scan length is not greatly changed if the same photosensitive material is used, in the conventional Single Barm LD, it is not necessary to largely change the light amount if the process speed does not change even if the resolution changes.

[0006]

However, when a Multi Beam LD having N LDs is used and the resolution is switched by switching between Multi / Single lighting, Single lighting has N times the light amount of Multi lighting. Required. A general LD current drive element (hereinafter, LD driver; LD)
D), the variable range of the light intensity is determined, and Multi / Si
It does not have a light quantity variable range that can support both of ngle lighting. If the amount of light is not the corresponding amount, it is necessary to adjust the irradiation time until the required amount of light is reached, and the processing cannot be sped up.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned facts, and has as its object to provide an optical scanning device capable of easily changing a variable light amount range.

[0008]

According to a first aspect of the present invention, there is provided an optical scanning device for irradiating a photosensitive material with a light beam corresponding to input data while scanning the light beam, and outputs two or more light beams. It has a possible LD, beam number switching means for switching the number of light beams of the LD according to switching of resolution, and light quantity switching means for switching a light quantity variable range of the LD according to the switched resolution. It is characterized by:

According to the present invention, the number of light beams of the LD can be switched according to the switching of the resolution, and the variable light amount range of the LD can be switched by the light amount switching means according to the switched resolution. The light amount variable range can be easily changed based on the number of light beams according to the above.

Accordingly, even in an image forming apparatus in which the resolution is switched by switching the number of beams, the variable range of the light amount can be easily changed, and accordingly, high speed and high resolution can be accommodated.

The change of the light amount variable range generally refers to a change of the light amount outside the light amount adjustment range performed in accordance with the deterioration of the optical member or the like. The case where a range different from the adjustment range is set is included.

According to a second aspect of the present invention, in an optical scanning device for irradiating a photosensitive material while scanning a light beam corresponding to input data, an LD capable of outputting two or more light beams; A light beam deflecting unit for deflecting the light beam from the LD toward the photosensitive material by driving; a rotation speed switching unit for switching the rotation speed of the light beam deflecting unit in accordance with the switching of resolution; The number of light beams of the LD is switched according to the switching of the number of light beams, and the light amount switching means is configured to switch a variable light amount range of the LD according to the switched resolution.

According to the present invention, the number of beams and the number of rotations of the light beam deflecting means are switched in accordance with the switching of the resolution, and the light quantity switching means sets the light quantity variable range of the LD in accordance with the switched resolution. Since the resolution can be switched, the resolution can be switched in a number of steps, and the variable light amount range can be easily changed based on the number of light beams and the rotation speed of the light beam deflecting means according to the resolution. .

Therefore, even in an image forming apparatus in which the resolution is switched by switching the number of beams and the number of rotations of the light beam deflecting means, the light amount variable range can be easily changed. Further, the resolution can be finely switched by switching the resolution using both the number of beams and the rotation speed of the light beam deflecting means.

Since the resolution is switched not only by changing the number of rotations of the light beam deflecting means but also by changing the number of beams, the high speed and high resolution can be achieved without increasing the number of rotations of the light beam deflecting means. Therefore, it is possible to realize a highly reliable optical scanning device by preventing noise and temperature rise.

Therefore, it is possible to change the variable amount of light of the image forming apparatus in which the resolution is changed by switching a plurality of beams without depending only on the rotation speed of the light beam deflecting means driven by the driving means.

According to a third aspect of the present invention, the light quantity switching means includes a light quantity adjusting means for adjusting a light emission quantity of the LD, and a detection sensitivity of the light quantity adjusting means is made to correspond to the number of beams corresponding to the resolution. It is characterized in that the light amount variable range is changed by switching.

According to the present invention, since the light quantity variable range is changed by switching the detection sensitivity of the light quantity adjusting means according to the number of beams, for example, when the number of beams is changed,
In response to this, the light quantity variable range of the LD is easily changed.
Here, since the light amount adjusting means can adjust the light amount of the light beam output from the LD to maintain the light amount at a constant value, by switching the detection sensitivity of the light amount adjusting means, the light amount before the switching is the same. The output of the LD is controlled so that the light amount becomes as high as the above. As a result, the light amount can be easily changed exactly N times. Thus, the variable range of the light amount of the light beam can be easily and reliably changed without providing a special device. Note that, with the change of the light amount variable range, the light amount adjustment range for adjusting the light amount to a constant value can be changed.

At this time, the switching of the detection sensitivity of the light amount adjusting means can be linked with the switching of the number of beams, as in the ninth aspect of the present invention. Accordingly, when the number of beams is changed by the number-of-beams switching unit and the light amount variable range is changed, the detection sensitivity of the light amount adjusting unit is switched in conjunction with the output amount, and the output sensitivity is easily adjusted to the number of beams. can do.

According to a fourth aspect of the present invention, the light amount switching means includes a light amount adjustment filter inserted into an optical path of the LD to adjust the amount of light transmitted through the LD. It is characterized in that the light amount variable range is changed by adjusting the transmittance so that the light beam transmission amount corresponds to the switched number of beams.

According to the present invention, the light amount adjusting filter includes:
Since the transmittance is switched so as to be the transmission amount of the light beam corresponding to the number of beams, when the number of beams is changed according to the resolution, the transmittance of the light amount adjustment filter is switched accordingly. Thus, a light beam having a light amount after adjustment according to the resolution can be obtained. Therefore, the variable light amount range can be easily adjusted without using complicated control.

The invention according to claim 5 is characterized in that it has a synchronous detection sensor amplification switching means for switching the amplification factor of the synchronous detection sensor for detecting the start of scanning of the light beam according to the switching of the resolution.

According to the present invention, since the amplification factor of the synchronization detection sensor is switched according to the resolution, for example, even if the light beam is scanned at a high speed in accordance with the resolution, the amplification factor can be reliably increased by increasing the amplification factor. The light beam can be made detectable.

At this time, the synchronous detection sensor amplifying means can be linked with the beam number switching means, as in the ninth aspect of the present invention. Accordingly, when the beam number is changed by the beam number switching means and the light amount variable range is changed, the light amount of the light beam corresponding to the beam number is changed. Can be reliably detected.

Also, as in the invention according to claim 6, when the synchronous detection sensor is operated, the number of light beams detectable by the synchronous detection sensor can be increased.

According to this, for example, during the high-speed rotation of the light beam deflecting means in which the amount of light incident on the synchronization detection sensor decreases, the number of light beams is increased only during the synchronization detection period to increase the amount of light incident on the synchronization detection sensor. can do. As a result, even when the light beam deflecting unit is rotating at a high speed, the synchronization detection sensor can reliably detect the light beam.

The invention according to claim 7 is characterized in that it has a beam diameter switching means for switching the beam diameter of the light beam from the LD in accordance with the switching of resolution.

According to this, since the beam diameter of the light beam is changed according to the resolution, when the resolution is changed and the light amount is changed, the beam diameter is optimized accordingly. As a result, even when an image is formed using such an optical scanning device, an image with good finishing quality can be formed by a light beam having an appropriate light amount and beam diameter.

At this time, the beam diameter switching means can be linked with the beam number switching means, as in the ninth aspect of the present invention. Thereby, when the number of beams is changed by the number-of-beams switching means and the light amount is changed,
A light beam adjusted to an appropriate beam diameter can be output in conjunction therewith.

Further, this beam diameter switching means is provided in claim 8
As in the invention according to the first aspect, it can be integrated with the light amount adjustment filter as described above. For example, when the shape of the light amount adjusting filter is a slit type, when the light beam passes through the light amount adjusting filter, a suitable amount of light is adjusted by a transmittance according to the number of beams, and the slit responds to the optimum light amount. Beam diameter. This makes it possible to reduce the number of components and downsize the device.

[0031]

FIG. 1 shows an optical scanning device 100 according to the present embodiment.

The optical scanning device 100 has two different LDs.
A dual LD (hereinafter, referred to as DLD) 112 including chips 112A and 112B (see FIG. 2) is provided. The DLD 112 has two LDDs 112A and 112B.
Thus, two light beams having different emission angles in the sub-scanning direction can be output. In FIG. 1, the two light beams are arranged in the front and rear direction on the paper surface, and thus are illustrated in an overlapping manner. The DLD 112 includes a DLD light receiving element (hereinafter abbreviated as PD) 114.
The light amount of the light beam output from 112 is detected.

In the vicinity of the emission side of the DLD 112,
On each optical axis of the two light beams from the DLD 112, a polygon mirror 102 as a light beam deflecting unit is disposed, and two laser beams from the DLD 112 are respectively reflected on reflection surfaces on the side surfaces of the polygon mirror 102. To reach. The polygon mirror 102 has a predetermined number (for example, 6
) Reflective surface. A scanner motor 104 (see FIG. 2) is connected to the polygon mirror 102. The scanner motor 104 rotates the polygon mirror 102 around the axis 102A at a predetermined speed in the direction of arrow R to continuously change the angle of incidence of the light beam on each reflecting surface. Thus, the light beam from the DLD 112 is deflected by the polygon mirror 102.

On the optical path of the light beam deflected by the polygon mirror 102, a pair of imaging lenses 106A and 106B
A photosensitive drum 108 formed into a cylindrical shape is rotatably disposed with an optical system 106 made of the same interposed therebetween. A drive unit (not shown) is connected to the photosensitive drum 108, and the photosensitive drum 108 rotates in one direction by the driving force of the drive unit.

As shown in FIG. 2, the DLD 112
The image processing device 150 is connected via the controller 116. The image processing device 150 includes the controller 1
16 to output the image data.

The controller 116 includes a light amount controller 11
8, a scanner rotation speed control unit 134, an SOS gain control unit 126, and a beam diameter switching control unit 136.

The light amount control circuit 118 includes a light amount control circuit 12
0 is provided. The light amount control circuit 120 includes LD current driving elements (hereinafter abbreviated as LDD) 122A and 122B.
Is connected to the DLD 112 via the. The light amount control circuit 120 can temporarily store the image data input from the image processing device 150 for every two scanning lines.

The LDDs 122 A and 122 B are turned on / off based on the image data and output a light beam having a light amount controlled by the light amount control circuit 120.

The light quantity control unit 118 includes a PD light quantity control circuit 124, and a light quantity control circuit 120 and a DLD
112. PD light quantity control circuit 12
4 detects the amount of LD light from the DLD 112,
The current-voltage conversion and amplification are performed, and the light amount control circuit 120
Output to

The light quantity control circuit 120 compares the output value from the PD light quantity control circuit 124 with a reference value and controls the light quantity so that the light quantity becomes a specified light quantity.

The scanner rotation speed control unit 134 is connected to the scanner motor 104 and
2 is controlled.

The SOS gain control section 126 has a synchronization detection sensor 128 (hereinafter referred to as the SOS sensor 128) (FIG. 1).
See).

The SOS sensor 128 is a polygon mirror 1
02 on the main scanning surface on which the light beam reflected and deflected by the scanning is scanned, the scanning start position (Start Of S
can; SOS) on the optical path of the light beam that converges. The SOS sensor 128 is connected to the light amount control circuit 120, and when an SOS beam is detected by the SOS sensor 128, an image writing timing signal is input from the SOS sensor 128 to the light amount control circuit 120. When a write start timing signal is input from the SOS sensor 128, the light quantity control circuit 120 starts modulating the image signal in the line after a predetermined time has elapsed.

As shown in FIG. 5, the SOS gain control section 126 is provided with an amplifier 130, and an SOS sensor 128 is connected to one input terminal side of the amplifier 130. The resistors Rf and Rg are connected in parallel between the other input terminal side and the output terminal side, and the gain changeover switch 132 is connected to the resistor Rf side.
The gain changeover switch 132 is turned on / off in response to a speed changeover signal from the scanner rotation speed controller 134 of the controller 116. Therefore, the gain switch 132
Is turned on / off, thereby changing the resistance value.

The beam diameter switching control unit 136 includes the LDD 11
2A and 112B are connected to a beam diameter switching driver 138. The beam diameter switching driver 138 drives according to a signal from the beam diameter switching control unit 136, and drives the LDD1.
The beam diameter of the output beams of 12A and 112B is changed.

Incidentally, a resolution changeover switch 140 is connected to the controller 116. The resolution changeover switch 140 outputs to the controller 116 a resolution changeover signal for executing a resolution changeover by a predetermined operation. Here, as an example, 600 dpi and 300d
Switching of resolution is performed with pi.

The controller 116 changes the number of output beams from the DLD 112 according to the resolution switching signal. That is, when the resolution is 300 dpi, one output beam is used, and when the resolution is 600 dpi, two output beams are used. In response, the LDD 122 to be driven
A and 122B are selected.

As shown in FIG. 3, the controller 116 is provided with a light amount switching circuit 142 for switching the light amount of the output beam in accordance with the resolution switching signal. The light amount switching circuit 142 includes a PD light amount control unit 118
And a light amount control circuit 120. The light amount switching circuit 142 includes LDDs 122A and 122B.
, Respectively, one of which will be described as an example.

In the light amount switching circuit 142, the light amount control circuit 1
On the 20 side, a comparator 144 is provided. The reference voltage Vref and the PD light amount monitor voltage Vr from the PD 114 are input to the input terminal of the comparator 144.

One end of monitor current detection resistors Ra and Rb as light emission output detection means is connected to the input side of the PD light quantity monitor voltage Vr of the comparator 144. The other end of the monitor current detection resistor Ra is grounded. The other end of the monitor current detection resistor Ra is connected to a resistance value switch 1
It is connected to the other end of the monitor current detection resistor Rb via 46, and is grounded similarly to the monitor current detection resistor Rb.

The monitor current detection resistors Ra and Rb are interlocking variable resistors, and are adjusted to always have the same resistance value. The monitor current detection resistors Ra and Rb correct the monitor current Is to a constant value. Thereby, LDD11
This prevents the monitor current Is from becoming different values due to differences in the threshold currents, differential efficiencies of the 2A and 112B, and the transmittance of optical components.

The resistance changeover switch 146 is connected to the DLD 11
The number of output beams of 2, ie, Single (one) or Dual
It is turned on / off according to a resolution switching signal for switching (two). Here, it turns on in the case of Single, and turns off in the case of Dual.

The output terminal of the comparator 144 is LDD1
The light amount control signal is connected to the LDD 122A or the LDD 122B and is output to the LDD 122A or the LDD 122B as a result of the comparison between the light amount monitor voltage Vr and the reference voltage Vref. The LDDs 122A and 122B output a light beam according to the input light amount control signal.

The LDDs 122A and 122B have E
The NB signal is input, and the LDDs 122A and 122B whose light amount is controlled by the ENB signal are selected. For example, in the case where the resolution is set to half of that in the case of two beams, the data is not divided into the A channel and the B channel, and the light amount is controlled to be twice that in the case of two beams.

Also, the reference voltage Vref is
It is possible to change the light amount according to the factor of the light amount decrease due to the sensitivity deterioration of 08, and thereby the light amount set on the optical scanning device 100 can be changed within a predetermined range.

The resolution switching signal input to the controller 116 is input to the SOS gain control unit 126, the scanner rotation speed control unit 134, and the beam diameter switching control unit 136. In the SOS gain control unit 126, the scanner rotation speed control unit 134, and the beam diameter switching control unit 136,
The gain of the sensor 128, the rotation speed of the scanner motor 104, and the beam diameter are controlled so as to be adjusted to values according to the resolution.

Next, the operation of the present embodiment will be described. First, the outline of the optical scanning device 100 will be described.

In the optical scanning device 100, the image processing device 15
After temporarily storing data “A + B” for two scanning lines inputted from 0 in the light amount control circuit 120, the data is divided into A channel and B channel. When the image writing timing signal is input from the SOS sensor 128, the data is divided into “A” and “B” and output to the LDDs 122A and 122B. In the LDDs 122A and 122B, according to the light amount control signal instructed from the light amount control circuit 120, the LDD
Light 112A and 112B. With this, DLD
Two output beams are emitted from 112. At this time,
The light amount of the output beam from the DLD 112 is detected by the PD 114, and the light amount of the output beam is adjusted to an appropriate value by the light amount switching circuit 142, as described later.

The output beam from the DLD 112 irradiates the side surface of the polygon mirror 102 which is driven to rotate in a predetermined direction (the direction of arrow R in FIG. 1) at a set number of rotations, and is deflected. The deflected output beam passes through the optical system 106 and irradiates the photosensitive surface of the photosensitive drum 108. The output beam scans and exposes the photosensitive surface of the photosensitive drum 108 in a predetermined direction by rotating the polygon mirror 102.

On the other hand, since the photosensitive drum 108 is rotationally driven by rotation driving means (not shown), the sub-scan is performed in a direction different from the main scan by the output beam.

Thus, main scanning and sub-scanning are performed, and an image corresponding to the image data is formed on the photosensitive surface of the photosensitive drum 108.

Next, control associated with resolution switching will be described. The optical scanning device 100 is provided with a resolution changeover switch 140, and outputs a resolution changeover signal by a predetermined key scan. A single mode in which one output beam is output and a dual mode in which two output beams are output are selected, and the mode is switched.

When the resolution is switched by the resolution switch 140, the number of rotations of the scanner motor 104 is changed according to the set number of output beams. Here, when there is no change in the number of beams, the speed becomes high when the resolution is switched to high, and becomes low when the resolution is switched to low. If the number of beams is changed, the speed is determined according to the number of beams used.

For example, when the resolution is set to 3/4 of the two-beam lighting, one of the LDDs 112A and 112B is turned on to make one output beam, and the scanner rotation speed control circuit 134 controls the polygon mirror 102 Increase the number of revolutions by 1.5 times. At this time, the image data is not divided into the A channel and the B channel, and the light amount is controlled by one of the LDDs 122A and 122B selected by the ENB signal, and the light amount is controlled to be twice as large as the case of two beams.

As a result, the resolution can be switched, the number of rotations of the polygon mirror 102 can be set, and an image can be formed on the photosensitive drum 108 at an appropriate scanning speed.

When the number of revolutions of the scanner is changed according to the resolution switching signal from the resolution switching switch 140,
Accordingly, the SOS gain control unit 126 adjusts the gain of the SOS sensor 128.

As shown in FIG. 5, when the SOS gain control section 126 switches the scanner rotation speed between high speed and low speed, the gain changeover switch 132 responds accordingly.
Is switched. That is, it turns on at a low speed (slow) and turns off at a high speed (fast). As a result, the output voltage Vouts at the time of low speed is Vouts = (1 + Rf)
Rg / (Rf + Rg)) RhVin, while the output voltage Voutf at high speed is Voutf = (1 + Rg /
Rh) Vin. At this time, the output voltage Vo at high speed
utf becomes larger than the output voltage Vouts at low speed.

As a result, when the scanning speed is high, S
The OS gain increases and the SOS gain decreases when the OS gain is slow. As a result, the SOS can be easily adjusted according to the scanning speed.
Gain can be adjusted.

Accordingly, the scan speed becomes higher and the SO
Even if the amount of incident light on the light receiving surface of the S sensor 128 decreases,
The amplification factor of the SOS sensor 128 increases, and the SOS sensor 128 can reliably detect one scan of the light beam.

Note that the single speed at which the scanner speed is the fastest
When the high resolution is set in the mode, the LDS1 which is not used for writing is used instead of increasing the SOS gain.
One of 12A and 112B may be turned on only during the SOS period. This allows the SOS sensor 128 to more reliably detect the output beam.

Next, a description will be given of the change of the light quantity variable range accompanying the resolution switching. LDD to which image data was sent
In 122A and 122B, the LDs 122A and 122B are turned on according to the light amount control signal instructed from the light amount control circuit 120. The PD light provided at the DLD 112 detects the LD light amount at that time. When detected by the PD 114, the PD 114 outputs a monitor current Is proportional to the amount of emitted light.
Is output.

Here, 600
When the resolution is switched to dpi or 300 dpi,
The light amount switching circuit 142 adjusts the light amount of the output beam output from the DLD 112 by changing a monitor current detection resistance value corresponding to the detection sensitivity.

When the resolution is switched to 600 dpi by the resolution switching signal, the resolution switch 140 of the light amount switching circuit 142 is turned off.

When the resolution changeover switch 140 is turned off, the monitor current Is does not flow through the monitor current detection resistor Ra. At this time, since the input voltage of the comparator 144 has a high impedance, the monitor current Is of the PD 114 flows through the monitor current detection resistor Rb. Thereby, PD1
14, the value of the light amount monitor voltage Vroff is Vroff =
It can be obtained by Rb × Is. As a result, the light amount is adjusted by comparing the obtained Vroff with the reference voltage Vref.

On the other hand, when the resolution is 300 dpi, the resolution switching switch 140 is turned on by the resolution switching signal.

When the resolution changeover switch 140 is turned on, the monitor current Is becomes the monitor current detection resistors Ra and Rb.
To the combined resistance. Therefore, the light amount monitor voltage Vr
on is Vron = (Ra × Rb / (Ra + Rb)) ×
It can be determined by Is. As a result, the amount of light is
It is adjusted by comparing the obtained Vron with the reference voltage Vref.

Here, since the control voltage Vron is adjusted by the reference voltage Vref so that Vron = Vroff, the monitor current Is is increased until Vroff = Vron when the resolution changeover switch 140 that reduces the combined resistance is off. You. As a result, the light amounts of the LDDs 112A and 122B increase. Therefore, in the case of 600 dpi, if the monitor current detection resistors Ra and Rb have the same resistance value, LDD1
The light amounts of 12A and 112B are twice as large as 300 dpi.

FIG. 4 is a graph showing the relationship between the light quantity and the control voltage. Here, the X-axis direction indicates a control voltage (Vron, Vroff) for changing the light amount, and the Y-axis direction indicates the light amount. As shown in the graph, the single mode and the dual mode have different light amount variable ranges, and when the same control voltage is applied, the light amount in the single mode is twice that in the dual mode. In addition, by switching between the light amount variable range in the Single mode (see arrow S) and the light amount variable range in the Dual mode (see arrow D), the light scanning device 100 has a wider light amount variable range (see arrow E). Will have.

As a result, the light amount variable range of the LDDs 112A and 112B can be easily changed according to the number of output beams according to the resolution. As a result, LDD11
2A and 112B are only a predetermined light amount variable range for changing the set light amount on the optical scanning device in accordance with factors such as deterioration of the sensitivity of the photosensitive drum 108, contamination of optical components, and reduction of the light amount due to deterioration of the LDDs 112A and 112. Instead, the light amount variable range can be further changed in accordance with the resolution switching. Therefore, the LDD 122A having a small light amount variable range,
Even with 112B, a large light amount variable range can be obtained.

Therefore, by changing the monitor current detection resistance value in conjunction with the resolution switching signal, the light amount variable range of the LDDs 112A and 112B can be easily changed.

In this embodiment, the case of two beams has been described as an example. However, in the case of three beams or more, the number of interlocking resistors R is increased to similarly change the light amount according to the resolution switching signal. Can be. If N interlocking resistors are used for N beams, an N-fold variable light amount range can be obtained.

In the present embodiment, although the monitor current detecting resistors Ra and Rb, which are interlocking variable resistors, are used to switch the light amount of the output beam output from the DLD 112 by the resolution switching signal, the present invention is not limited to this.

FIG. 6 shows another light amount switching circuit 160. The light amount switching circuit 160 is a PD light amount control circuit 1
62 and a light amount control circuit 120. The PD light amount control circuit 162 includes an electronic volume (hereinafter abbreviated as EVR) 164. One end of the EVR 164 is connected to the PD 114, whereby the monitor current Is is applied to the EVR 164. The other end of the EVR 164 is connected to the comparator 144 of the light amount control circuit 120, so that the light amount monitor voltage Vr is input to the comparator 144. The EVR 164 changes a resistance value according to an externally applied voltage.

The EVR 164 is connected to a beam switch 166. Beam switch 16
Reference numeral 6 switches between a single mode and a dual mode by switching a terminal that is turned on in response to a resolution switching signal. Hereinafter, the side that is turned on in Single mode is the Single side,
The side that is turned on in Dual mode is called the Dual side.

The beam switch 166 is connected to monitor current detection resistors Rc and Rd. The monitor current detection resistor Rc is connected to the Dual side of the beam switch 166 and
Each is connected to the Single side. On the other hand, the monitor current detection resistor Rd is connected to the Single side at one end, and is grounded at the other end. The monitor current detection resistors Rc and Rd have the same resistance value.

On the Dual side of the beam switch 166,
The resistor Re is connected, and the beam changeover switch 166 is connected.
Is switched to the Dual mode, the voltage applied to the EVR 164 can be set by adjusting the value of the resistor Re.

When such a light amount switching circuit 160 is used, when the beam switch 166 is set to the Dual mode,
A voltage is applied to both the monitor current detection resistors Rc and Rd.

On the other hand, in the Single mode, since the voltage is divided by the monitor current detection resistors Rc and Rd, the voltage is half that in the Dual mode. When this voltage is applied to the EVR 164, the resistance of the EVR 164 becomes half,
The amount of light is increased until the monitor current Is doubles. As a result, the light amount becomes a double value. Similarly, in the case of three or more beams, the monitor current detection resistor R and the resolution switch 1
The number of terminals can be increased, and the amount of light can be changed according to the resolution switching signal.

Thus, similarly to the above, the light amount and the light amount variable range can be easily changed, and a light beam of an appropriate light amount can be output even when the resolution is switched.

In this embodiment, the light amount switching circuit 142
Although the light amount of the light beam output from the DLD 112 is adjusted by 160, the method of adjusting the light amount of the light beam for scanning and exposing the photosensitive drum 108 is not limited to these methods.

FIGS. 7 and 8 show an optical scanning device 170 according to another embodiment. Note that components having the same functions and effects as those of the optical scanning device 100 described above are denoted by the same reference numerals and description thereof will be omitted.

The optical scanning device 170 is disposed between the DLD 112 and the polygon mirror 102 so as to be insertable into the optical path of the light beam output from the DLD 112 or detachable from the optical path. Further, the light amount adjustment filter 172 is arranged in the vicinity of the optical path of the light beam, where the light is focused. The light amount adjustment filter 172 is
The light beam output from the DLD 112 has a transmittance of 50%.

As shown in FIG. 8, the optical scanning device 170
The controller 176 controls the amount of light so that the amount of light detected by the PD 114 is maintained at a predetermined value.
A D light amount control unit 180 is provided.

The controller 176 is provided with a filter insertion control unit 178. The filter insertion control unit 178 is connected to the light amount adjustment filter 172 via a driver 174. Filter insertion control unit 178
Outputs a filter insertion signal to the driver 174 according to the resolution switching signal. The driver 174 is driven in accordance with a signal from the filter insertion control unit 178 to move the light amount adjustment filter 172.

Next, the light amount adjustment processing in the optical scanning device 170 will be described. When the resolution switching signal is input to the controller 176, the Si switching is performed in accordance with the resolution switching signal.
The ngle mode or the dual mode is selected.

Here, the light amount in the Dual mode is half the light amount per LDD 112A, 112B compared to the light amount in the Single mode. That is, two LDDs
If both are used, compared to the case where one of 112A and 112B is used, the amount of light per unit becomes ２.

Therefore, the light amount is set in the single mode, the LDDs 112A and 112B are driven together, and the light amount adjusting filter 172 is inserted on the optical path to reduce the light amount of the light beam to 50%.

Therefore, by adjusting the light amount to the single mode,
By driving the DD 112A, 112B, L
It is not necessary to largely change the light quantity fluctuation per one of the DDs 112A and 112B.
The light amount can be easily adjusted only by inserting and removing the light source 2 in and out of the optical path of the light beam.

When the light amount adjustment is performed using the light amount adjustment filter 172, the width of the light amount variable range and the light amount adjustment range can be changed according to the light amount adjusted by the light amount adjustment filter 172.

FIG. 9 shows another example of the light amount adjusting filter 172. The light amount adjustment filter 172 is provided in FIG.
As shown in FIGS. 9A and 9B, a plurality of different filters 180 form a set of light amount adjusting filters 18.
2, 184 may be configured. Such a filter 1
The number of 80 can be appropriately determined according to the number of light sources. Also, such a set of light amount adjustment filters 18
Depending on the configurations of 2, 184, the mode of insertion / removal of the light beam on the optical path can be appropriately changed. Note that FIG.
In the light amount adjustment filter 182 shown in FIG.
By rotating in the direction of arrow M around one, each filter 180 is inserted into the optical path of the output beam. In the light amount adjustment filter 184 shown in FIG.
By rotating around arrow 85 in the direction of arrow L, each filter 180 is inserted into the optical path of the output beam.

Further, as shown in FIG. 8C, a light amount adjusting filter 186 in which a filter 180 and a slit 188 are used in combination may be used. Thereby, the filter 1
The beam diameter can be easily changed according to the resolution by using the slit 188 while adjusting the light amount using the 80. In the light amount adjustment filter 186, each filter 180 is inserted on the optical path of the output beam by moving in the direction of arrow K. In the optical scanning device 170, the position of the light amount adjustment filter 172 is
And the polygon mirror 102, but the invention is not limited to this. At the place where the light is condensed near the LD, the filter can be made small and economical.
2 and the photosensitive drum 108. Further, the change of the transmittance by such a filter may be performed by mechanically inserting the filter on the optical path of the light beam, or electrically by using a liquid crystal or the like.

Controller 116 in the present embodiment
May be provided with a resolution switching prohibition unit that prohibits a change in resolution during the formation of an image that is one section, for example, for each page.

During the resolution switching, the SOS cycle is also undefined because the rotation speed of the scanner motor is undefined. In such a state, accurate synchronization cannot be achieved, and, despite the normal operation, rotation abnormality detection is activated or two images are output on the same sheet. When the resolution is switched within the same page, the resolution switching prohibition unit can prohibit images having different resolutions from being present on the same sheet. Also, it can be provided.

Further, the controllers 116 and 176 according to the present embodiment have the DLD
A beam output prohibiting unit that prohibits the output of the light beam by the S. 112 and an SO that prohibits the SOS detection during resolution switching.
S detection inhibiting means may be provided for each or both of them.

The resolution switching often involves a change in the number of revolutions of the scanner motor, and it takes time to change. For this reason, the beam output prohibiting unit and the SOS detection prohibiting unit prohibit the output of the light beam and the SOS detection during such invalid time, respectively. Waste of toner can be prevented.

The resolution switching prohibiting means and the SOS
When a resolution change request is made according to the detection prohibition unit, the LDDs 112A and 112B can be turned off, and the LDDs 112A and 112B can be turned on after the resolution changing step is completed.

In the present embodiment, two LDDs 112
The case of the DLD 112 provided with A and 112B has been described as an example. However, the same can be applied to a Multi Beam LD having three or more beams.

In this embodiment, the resolution is switched by
Although the number of light beams output from the DLD 112 and the number of rotations of the scanner motor 104 are used together, the same effect can be obtained even when the resolution can be switched only by the number of light beams.

Further, in the present embodiment, the number of beams is switched in accordance with the resolution switching signal, and the switching processing of the light amount is performed in conjunction with the switching, but the present invention is not limited to this. For example, the switching of the number of beams and the switching of the resolution may be performed separately, and the switching processing of the light amount may be performed only according to the switching of the number of beams.

[0110]

According to the present invention, even in an optical scanning device which changes the resolution by switching the number of beams, the variable range of the amount of light can be easily changed. Without increasing the speed, it is possible to cope with high speed and high resolution, and it is possible to prevent noise and temperature rise due to an increase in the rotation speed of the light beam deflecting means. Further, even in an optical scanning device capable of switching resolution by using both the number of rotations and the number of beams of the light beam deflecting means,
The light amount variable range can be easily changed, and the light amount variable range can be easily changed to an appropriate light amount variable range according to a fine resolution switching step.

By switching the amplification factor of the synchronous detection sensor according to the resolution, the synchronous detection sensor can reliably detect the light beam.
A malfunction of the synchronization detection sensor caused by changing the light amount variable range can be prevented.

Further, by having the beam diameter switching means, the beam diameter of the output beam can be changed according to the resolution, and a light beam having an appropriate beam diameter according to the light amount can be output.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an optical scanning device according to an embodiment of the present invention.

FIG. 2 is a block diagram of the optical scanning device according to the embodiment.

FIG. 3 is a circuit diagram of a light amount switching circuit according to the present embodiment.

FIG. 4 is a graph illustrating an example of a relationship between a control voltage and a light amount in the optical scanning device according to the present embodiment.

FIG. 5 is a circuit diagram of an SOS gain control unit of the optical scanning device according to the present embodiment.

FIG. 6 is a circuit diagram of another light amount switching circuit according to the present embodiment.

FIG. 7 is a schematic diagram of another optical scanning device according to the embodiment of the present invention.

FIG. 8 is a block diagram of another optical scanning device according to the present embodiment.

9A is a schematic perspective view of a light amount adjustment filter according to the embodiment, FIG. 9B is a schematic plan view of another light amount adjustment filter according to the embodiment, and FIG. FIG. 9 is a schematic plan view of another light amount adjustment filter according to the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 light scanning device 102 polygon mirror (light beam deflecting means) 104 scanner motor (driving means) 108 photosensitive drum (photosensitive material) 112 DLD (laser diode) 114 PD (light emission output detecting means) 116 controller 118 light quantity control unit 120 light quantity control Circuit (number of beam switching means) 122 LDD 124 PD light quantity control circuit 126 SOS gain control section 128 SOS sensor (synchronous detection sensor) 134 Scanner rotation speed control section 136 beam diameter switching control section 142 light quantity switching circuit (light quantity switching means) 160 light quantity Switching circuit (light quantity switching means) 162 PD light quantity control circuit 172 Light quantity adjusting filter (light quantity switching means) 178 Filter insertion control section

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 15/043 G03G 15/04 120 15/04

Claims (9)

[Claims] 1. A light beam according to input data,
In an optical scanning device for irradiating a photosensitive material while scanning, a laser diode capable of outputting two or more light beams, a beam number switching means for switching the number of light beams of the laser diode according to switching of resolution, An optical scanning device, comprising: a light amount switching unit that switches a light amount variable range of the laser diode according to the switched resolution. 2. A light beam according to input data,
In an optical scanning device for irradiating a photosensitive material while scanning, a laser diode capable of outputting two or more light beams, and light for deflecting the light beam from the laser diode toward the photosensitive material by rotationally driving the laser diode Beam deflecting means, rotation number switching means for switching the number of rotations of the light beam deflecting means in response to switching of resolution, and beam number switching means for switching the number of light beams of the laser diode in response to switching of resolution. An optical scanning device, comprising: a light amount switching unit that switches a variable light amount range of the laser diode according to the switched resolution. 3. The light amount switching unit includes a light amount adjusting unit that adjusts a light emission amount of the laser diode, and switches a detection sensitivity of the light amount adjusting unit in accordance with the number of beams according to a resolution, thereby obtaining a light amount. 3. The optical scanning device according to claim 1, wherein the variable range is changed. 4. The light amount switching means includes a light amount adjustment filter inserted on an optical path of the laser diode to adjust a transmitted light amount of the laser diode, wherein the light amount adjustment filter is a beam switched according to a resolution. 3. The optical scanning device according to claim 1, wherein the light amount variable range is changed by adjusting the transmittance so that the light beam transmission amount corresponds to the number. 5. A synchronous detection sensor amplification switching means for switching an amplification factor of a synchronous detection sensor for detecting the start of scanning of the light beam according to a change in resolution. The optical scanning device according to claim 1. 6. The optical scanning device according to claim 5, wherein the number of light beams detectable by the synchronization detection sensor is increased when the synchronization detection sensor operates. 7. The apparatus according to claim 1, further comprising a beam diameter switching means for switching a beam diameter of the light beam from the laser diode in accordance with a change in resolution. Optical scanning device. 8. The beam diameter switching means is inserted on the optical path of the laser diode to adjust the amount of light transmitted by the laser diode and to transmit the amount of light beam corresponding to the number of beams switched according to the resolution. The optical scanning device according to claim 7, wherein the optical scanning device is integrated with a light amount adjustment filter that adjusts the transmittance so as to satisfy the following condition. 9. A switching of the detection sensitivity of the light amount adjusting unit, a switching of the light amount adjusting filter, a switching of the amplification factor of the synchronous detection sensor, or a switching of the light beam in conjunction with the switching of the beam number switching unit of the laser diode. 4. The method according to claim 3, wherein the switching of the beam diameter is performed.
8. The optical scanning device according to 4, 5, or 7.