JPH10278342A - Method for adjusting optical unit emitting laser beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for adjusting an optical unit emitting a laser beam in which the time required for measuring the local point and adjusting the collimator lens position is shortened by eliminating the scanning operation for detecting the focal point and the moving range of a collimator lens moving mechanism is reduced. SOLUTION: The method for adjusting the focus of a light emitted from a laser diode, and the emitting position thereof, through a collimator lens in an optical unit emitting a laser beam comprises a step (S2) for measuring the three-dimensional position of a laser chip in the laser diode, and a step (S5) for adjusting the three-dimensional position of the collimator lens based on the three-dimensional position of the laser chip thus measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam used in a laser beam printer (LBP), a laser facsimile machine, and the like for performing recording by scanning a photosensitive drum as a recording medium with a laser beam modulated by an image signal. The present invention relates to a method for adjusting an emission optical unit.

[0002]

2. Description of the Related Art In recent years, a recording apparatus such as a laser beam printer (LBP) for recording an image by scanning a laser beam has been widely used. The laser scanning optical system used in the image recording apparatus will be described with reference to FIG. 7. A semiconductor laser light source 71, a collimator lens 72, an imaging optical system 73, a polygon mirror 74 serving as a deflector, and an fθ lens 7
5. A photosensitive drum 76 as a recording medium is arranged along the optical path. The laser beam from the semiconductor laser light source 71 modulated by the image signal is converted into parallel light by a collimator lens 72, further deflected by a polygon mirror 74, formed on a photosensitive drum 76 by an fθ lens 75, and scanned.

In general, the emitted light of a semiconductor laser light source has a property of spreading radially from a light emitting point. Therefore, when used in an LBP or the like, a laser beam emitting optical unit that normally converts the emitted light into a parallel light beam using a collimator lens. Is used. FIG. 8 is a longitudinal sectional view of an example of such a laser beam emitting optical unit. The semiconductor laser diode 40 is fixed to the light emission control circuit board 62, and the substrate 62 and the semiconductor laser diode 40 are fixed to the holder 11. ing. Further, the lens barrel 12 holding the collimator lens 64 is adjusted in focus in a direction parallel to the emitted light, adjusted in an irradiation position in a direction orthogonal to the emitted light, and then fixed to the holder 11 by bonding.

Conventionally, this focus adjustment is performed by causing a laser chip to emit light as shown in FIG. 9, scanning the lens barrel 12 in a direction parallel to the emitted light, capturing the emitted light during that time by the television camera 22, and processing the output signal by image processing. Processing is performed by the device 23 to calculate the peak light amount of the laser beam corresponding to each scanned position. The relationship between the scan movement amount and the peak light amount is as shown in FIG.
% Are calculated by the host computer 24, and the midpoint thereof is set to (a + b) / 2 as the best focus position, and the controller 25 moves the lens barrel 12 to the position having this value. Send a signal to 26.
In the irradiation position adjustment, the position of the emitted light captured by the television camera 22 is processed by the image processing device 23, and the lens barrel 12 is moved so that the emitted light enters a predetermined position.

[0005]

However, in the above-mentioned conventional adjusting method, especially in the focus adjustment, the outer diameter of the laser diode and the position of the laser chip vary in the order of several tens of μm, so that the lens barrel is not designed. It is necessary to perform an adjustment operation in which the laser beam is scanned back and forth around the focus position in the laser beam emission direction, the focus position is calculated based on the value, and then the lens barrel is moved to the focus position. This requires a lens barrel moving mechanism having a large moving range.

The focus adjustment of the conventional two-beam laser emission optical unit is substantially the same as the adjustment of the one-beam laser emission optical unit described above. First, as shown in FIG. 12 is scanned in a direction parallel to the emitted light, the emitted light in the meantime is captured by the TV camera 22, and the output signal is processed by the image processing device 23 to calculate the peak light amount of the laser beam corresponding to each scanned position. doing. The relationship between the scan movement amount and the peak light amount is as shown in FIG. 10, and is 90% of the maximum value of the peak light amount.
The positions a and b are calculated by the host computer 24, and the intermediate point thereof is (a + b) / 2, which is the best focus position of the laser on the emitting side. Next, the measured laser emission is stopped, and the other laser is emitted, and the same focus measurement as described above is performed. Then, the controller 25 sends a signal to the lens barrel moving unit 26 to move the lens barrel 12 to an intermediate position between the detected focus positions of the two lasers.
In adjusting the irradiation position, the two lasers are alternately emitted, and the positions of the respective emitted lights captured by the television camera 22 are processed by the image processing device 23 so that the two emitted lights enter the predetermined positions. Is moving.

In the two-beam optical unit as well, especially in the focus adjustment, the outer diameter of the laser diode and the position of the laser chip vary in the order of several tens of μm. It is necessary to perform an adjustment operation of scanning back and forth in the laser light emission direction with the center as the center, calculating the focus position based on the value, and then moving the lens barrel to the focus position, and performing the operation for two laser emission lights. Therefore, it takes time to measure the focus position, and the lens barrel moving mechanism needs to have a large moving range.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned unresolved problems of the prior art, and does not perform a scanning operation for detecting a focus position, thereby measuring a focus position and a collimator lens position. It is an object of the present invention to provide a method for adjusting a laser beam emitting optical unit, which requires less time for adjusting the laser beam and also requires a shorter moving range of the collimator lens moving mechanism.

[0009]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, a method for adjusting a laser beam emitting optical unit according to the present invention is directed to a laser for adjusting a focus and an emitting position of light emitted from a laser diode by a collimator lens in the laser beam emitting optical unit. A method for adjusting a beam emitting optical unit, comprising:
A measuring step of measuring a three-dimensional position of the laser chip measured in the measuring step; and an adjusting step of adjusting a three-dimensional position of the collimator lens based on measurement information of the three-dimensional position of the laser chip measured in the measuring step. .

In the method for adjusting a laser beam emitting optical unit according to the present invention, when the measuring step detects positions in an X direction and a Y direction, which are directions orthogonal to a light emitting direction of the laser chip, X The directional position is detected from the inner end face position of the current blocking layer or the evaporation preventing layer of the laser chip, and the Y direction position is detected from the interface position between the active layer and the clad layer of the laser chip.

In the method for adjusting a laser beam emitting optical unit according to the present invention, the X-direction position may be a center position between inner end surfaces of the current blocking layer or a center position between inner end surfaces of the evaporation prevention layer. It is characterized by a light emitting position.

In the method for adjusting a laser beam emitting optical unit according to the present invention, when the measuring step detects positions in an X direction and a Y direction which are directions orthogonal to a light emitting direction of the laser chip, The laser diode emits light, and the position in the X direction and the Y direction is detected from the position of the light emitting point.

In the method for adjusting a laser beam emitting optical unit according to the present invention, when detecting a position in a Z direction which is a direction parallel to a light emitting direction of the laser chip in the measuring step, it is connected to a microscope. The surface of the laser chip is imaged by a television camera, and the position of the laser chip within the depth of field of the microscope is detected by an image processing device. Is detected.

Further, according to the method for adjusting a laser beam emitting optical unit according to the present invention, in a laser beam emitting optical unit that emits two light beams, a collimator lens adjusts a focus of emitted light from two laser chips and an emitting position. A method for adjusting a laser beam emitting optical unit for adjusting the three-dimensional position of the two laser chips, the method comprising: measuring a three-dimensional position of each of the two laser chips; and measuring a three-dimensional position of the two laser chips measured in the measuring step. Adjusting a three-dimensional position of the collimator lens based on the position measurement information.

In the method for adjusting a laser beam emitting optical unit according to the present invention, when the position in the X direction and the Y direction that is a direction orthogonal to the light emitting direction of the laser chip is detected in the measuring step, X The directional position is detected from the inner end face position of the current blocking layer or the evaporation preventing layer of the laser chip, and the Y direction position is detected from the interface position between the active layer and the clad layer of the laser chip.

In the method for adjusting a laser beam emitting optical unit according to the present invention, the X-direction position may be a center position between inner end surfaces of the current blocking layer or a center position between inner end surfaces of the evaporation prevention layer. It is characterized by a light emitting position.

In the method for adjusting a laser beam emitting optical unit according to the present invention, in the measuring step, when detecting positions in an X direction and a Y direction which are directions orthogonal to a light emitting direction of the laser chip, The laser chip emits light, and the position in the X direction and the Y direction is detected from the position of the light emitting point.

In the method for adjusting a laser beam emitting optical unit according to the present invention, when detecting a position in a Z direction which is a direction parallel to a light emitting direction of the laser chip in the measuring step, it is connected to a microscope. The surface of the laser chip is imaged by a television camera, and the position of the laser chip within the depth of field of the microscope is detected by an image processing device. Is detected.

In the method for adjusting a laser beam emitting optical unit according to the present invention, in the adjusting step, a direction orthogonal to a light emitting direction of the laser chip is set to X.
Assuming that the Y direction and the direction parallel to the light emission direction of the laser chip are the Z direction, the center of the collimator lens is located at the center position of the XY directions of the two laser chips measured in the measurement step in the XY direction. In the Z direction, the principal point of the collimator lens is aligned with a position at a predetermined distance from the center of the two laser chips in the X and Y directions.

[0020]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(First Embodiment) FIG. 1 is a diagram showing a configuration of an adjusting device of a laser beam emitting optical unit according to a first embodiment.

In FIG. 1, a laser beam emitting optical unit adjusting device 1 includes a television camera 14 for picking up an image of a laser chip disposed inside a laser holder 11 and an image of the laser chip disposed in front of the television camera 14. A microscope 9 for forming an image on an image sensor in a television camera 14 and a mirror for moving a lens barrel 12 having a collimator lens 64 disposed in front of a laser holder 11 in X, Y, and Z directions. Tube moving unit 19 and TV camera 1
An image processing device 16 for processing image data captured by the imaging device 4, a host computer 17 for calculating the amount of movement of the lens barrel 12 based on information output from the image processing device 16, and a host computer 17. A controller 18 for moving the lens barrel moving unit 19 based on the output information is schematically configured.
Note that the configuration of the laser beam emission optical unit is the same as that of the conventional one shown in FIG.

FIG. 2 is a diagram showing the structure of the laser diode.

As shown in FIG.
Is fixed to the laser holder 11 at the portion of the stem 45, and the stem 45 and the laser chip 4 that is the actual light emitting point
2 is mounted via a mount 46 and a submount 43, and the position of the laser chip 42 with respect to the stem 45 varies by several tens of microns depending on the laser diode. Therefore, in the present embodiment, the position of the active layer of the laser chip, which is the actual light emitting point, is directly measured by a television camera, and the position of the collimator lens is adjusted based on the measured position information.

FIG. 3 is a view showing the structure of the laser chip 42. The laser chip 42 is configured in a layered manner at each portion, and the components, shapes, etc. of the respective layers are different. Therefore, it is possible to specify the active layer 54 that is an actual light emitting point. In the present embodiment, the boundary between the active layer 54 and the cladding layer 57 is detected as a light emitting point in the Y direction. The position of the light emitting point in the X direction is set at the inner end 5 of the current blocking layer 55.
It can be detected as a center point between 5a and 55b or a center point between the inner ends 56a and 56b of the evaporation prevention layer 56.

Next, the adjusting operation of the adjusting device 1 for the laser beam emitting optical unit will be described with reference to the flowchart shown in FIG.

First, the laser holder 11 containing the laser chip 42 is set in the adjusting device 1 (step S).
1). Next, the lens barrel 1 in which the collimator lens 64 is built
2 is removed from the laser emission axis (optical axis), and the three-dimensional position of the laser chip 42 inside the laser holder 11 is imaged by the television camera 14 (step S2). Then, the image data is processed by the image processing device 16, and the host computer 17 uses the laser emitting direction (Z direction) of the laser chip 42 and directions orthogonal to the emitting direction (X direction and Y direction).
Direction) is calculated (step S3). At this time,
As described above, the position of the laser chip 42 in the Y direction is detected from the position of the active layer 54 of the laser chip 42,
The position in the X direction is detected from the position of the inner end of the current blocking layer 55 or the evaporation preventing layer 56. The position in the Z direction is
Detection is performed based on the amount of movement of the lens barrel of the microscope 9 when the microscope 9 is focused on the surface of the laser chip 42. The high-power microscope 9 has a very shallow depth of field (several μm).
Therefore, by adjusting the focus of the microscope 9 to the surface of the laser chip 42, the position of the surface of the laser chip 42 can be accurately measured.

Next, the lens barrel 12 which has been first deviated from the optical axis is set in the laser holder 11 (step S4), and XYZ is calculated based on the movement amount calculated by the host computer 17.
By moving the barrel moving unit 19 in each direction, the collimator lens 64 in the barrel 12 is moved to adjust the irradiation position and the focus (Step S5). Finally, the lens barrel 12 is moved to the laser holder 11.
And the adjustment operation is completed (step S
6).

As described above, in this embodiment, an image of the laser diode inserted and fixed in the laser holder is taken from the laser beam emission direction, and the three-dimensional position of the laser chip is measured through the protective glass. The lens barrel holding the collimator lens is adjusted three-dimensionally based on the measured value of the three-dimensional position, and the relative position between the laser chip and the lens barrel, that is, the relative position between the laser chip and the collimator lens is set to a predetermined position. To do. In this way, by directly detecting the position of the laser chip and determining the position of the collimator lens, focus adjustment and irradiation position adjustment on the order of several micrometers can be performed without scanning the collimator lens, greatly reducing the adjustment time. it can. In addition, since it is not necessary to scan the collimator lens in the front-back direction centering on the designed focus position, the moving range of the lens barrel moving mechanism can be greatly reduced, and the movement control can be simplified, so that the cost of the device is greatly reduced. it can.

(Second Embodiment) Next, a second embodiment of the present invention will be described.

The adjusting device for the laser beam emitting optical unit according to the second embodiment has two laser chips in the lens holder 11 and can emit two laser beams. This is a device for adjusting the optical unit.

The configuration of the laser beam emitting optical unit is the same as the conventional one shown in FIG. 8 except that it has two laser chips inside, so that the description is omitted.

FIG. 5 is a view showing a configuration of an adjusting device of a laser beam emitting optical unit according to the second embodiment.

In FIG. 5, a laser beam emitting optical unit adjusting device 101 includes a laser chip disposed inside a laser holder 11 and a television camera 114 for imaging laser light emitted from the laser chip, and a television camera 114.
The image of the laser chip placed in front of
A microscope 109 for forming an image on the image sensor in 4;
A lens barrel moving unit 119 for moving a lens barrel 12 having a built-in collimator lens disposed in front of the laser holder 11 in X, Y, and Z directions, and for processing image data captured by the television camera 114. Image processing device 116, a host computer 117 for calculating the amount of movement of the lens barrel 12 based on information output from the image processing device 116, and a lens barrel moving unit based on information output from the host computer 117. It comprises a controller 118 for moving the 119 and a laser driver 128 for emitting a laser chip.

As described with reference to FIG. 2 in the first embodiment, the laser diode 40 is fixed to the laser holder 11 at the portion of the stem 45. The chip 42 includes a mount 46,
The laser chip 42 is mounted via a submount 43, and the position of the laser chip 42 with respect to the stem 45 varies by several tens of microns depending on the laser diode. Therefore,
In the present embodiment, the actual position of the light emitting point is directly measured by the television camera, and the position of the collimator lens is adjusted based on the measured position information of the light emitting point.
Specifically, the emitted laser light is transmitted to the television camera 114.
And the image processing is performed to calculate the light emission amount distribution in the directions (X direction and Y direction) orthogonal to the beam emission direction (Z direction), and the position of the peak light amount in the distribution is defined as the position of the light emitting point. .

Next, the adjusting operation of the adjusting device 101 of the laser beam emitting optical unit will be described with reference to the flowchart shown in FIG.

First, the laser holder 11 containing two laser chips is set in the adjusting device 101 (step S101). Next, the lens barrel 12 containing the collimator lens 64 is detached from the laser emission axis (optical axis).
The amount of movement of the lens barrel of the microscope 109 when the focus of the microscope 109 is adjusted to the surface of one laser chip is detected.
Thus, the position of the one laser chip in the Z direction is measured. Similarly, the amount of movement of the lens barrel of the microscope 109 when the focus of the microscope 109 is adjusted to the surface of the other laser chip is detected.
Measure the direction position. Then, the center of the Z direction positions of these two laser chips is set as the Z direction position of the two laser chips (step S102). High magnification microscope 1
In 09, since the depth of field is very shallow (several μm), the position of the surface of the laser chip can be accurately measured by adjusting the focus of the microscope 109 to the surface of the laser chip.

Next, the two laser chips inside the laser holder 11 are energized to emit light, and the emission point is imaged by the television camera 114 (step S103). Then, the image data is processed by the image processing device 116, and the position in the direction (X direction and Y direction) orthogonal to the emission direction is calculated by the host computer 117. At this time, the position of the light emitting point is a position where the light amount distribution in the XY directions is calculated and the light amount becomes maximum in the distribution. The position of this light emitting point is 2
For each of the two laser chips, the center of the positions of the two light emitting points is set as the final light emitting point position (step S
104).

Next, the lens barrel 12 which has been first deviated from the optical axis is set on the laser holder 11 (step S105), and the lens barrel moving unit 119 is moved in each of the XYZ directions based on the movement amount calculated by the host computer 117. Is moved, the collimator lens 64 in the lens barrel 12 is moved.
To adjust the irradiation position and the focus (step S106). Finally, the lens barrel 12 is fixed to the laser holder 11 with an adhesive or the like, and the adjustment operation ends (step S107).

As described above, in this embodiment, the position of the laser chip inserted and fixed in the laser holder in the Z direction is measured by a microscope, and the laser chip is energized to emit the laser light emitted from the laser chip. Point X
Measure the position in the Y direction. Based on the measured values in the XYZ directions, the lens barrel holding the collimator lens is three-dimensionally adjusted, and the relative position between the laser chip and the lens barrel, that is, the relative position between the laser chip and the collimator lens, is adjusted to a predetermined relative position. Position. Thus, by directly detecting the position of the light emitting point of the laser chip and determining the position of the collimator lens, focus adjustment and irradiation position adjustment on the order of several μm can be performed without scanning the collimator lens, and the adjustment time is reduced. Can be significantly reduced. Also,
Since it is not necessary to scan the collimator lens in the front-rear direction around the focus position in design, the moving range of the lens barrel moving mechanism can be significantly reduced, and the movement control can be simplified, so that the cost of the apparatus can be significantly reduced.

Further, in the second embodiment, in order to actually emit the laser chip and measure the position of the light emitting point, the first light emitting point is calculated from the position of the active layer of the laser chip before light emission. The position of the light emitting point can be specified more strictly than in the embodiment.

The present invention can be applied to a modification or modification of the above embodiment without departing from the gist of the invention.

For example, in the above-described first embodiment, the adjustment of the one-beam emission optical unit has been described. However, a method of calculating the position of the light emitting point from the position of the active layer of the laser chip of the first embodiment is described. The present invention may be applied to adjustment of a two-beam emission optical unit according to the second embodiment.

Conversely, the method of directly measuring the position of the light emitting point by turning on the laser chip of the second embodiment is applied to the adjustment of the one-beam emission optical unit of the first embodiment. Is also good.

[0045]

As described above, according to the present invention,
In adjusting the laser beam emitting optical unit, there is no need to emit a laser to scan the collimator lens, so that the time spent for measurement and adjustment can be greatly reduced.
In addition, the mechanism for moving the collimator lens can also reduce the moving range. Thereby, the manufacturing cost of the laser beam emitting optical unit can be significantly reduced.

[0046]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an adjustment device of a laser beam emission optical unit according to a first embodiment.

FIG. 2 is a diagram showing a structure of a laser diode.

FIG. 3 is a diagram showing a structure of a laser chip.

FIG. 4 is a flowchart illustrating an adjustment procedure of an adjustment device of the laser beam emission optical unit according to the first embodiment.

FIG. 5 is a diagram illustrating a configuration of an adjustment device of a laser beam emission optical unit according to a second embodiment.

FIG. 6 is a flowchart illustrating an adjustment procedure of an adjustment device of the laser beam emission optical unit according to the second embodiment.

FIG. 7 is a diagram illustrating a configuration of a laser scanning optical system used in the image recording apparatus.

FIG. 8 is a diagram showing a structure of a laser beam emission optical unit.

FIG. 9 is a diagram showing a configuration of a conventional adjustment device for a laser beam emitting optical unit.

FIG. 10 is a diagram showing the relationship between the amount of movement of a collimator lens and the amount of light received by a television camera.

[Explanation of symbols]

 Reference Signs List 1 Adjustment device for laser beam emission optical unit 9 Microscope 11 Laser holder 12 Lens tube 14 TV camera 16 Image processing device 17 Host computer 18 Controller 42 Laser chip 54 Active layer

Claims (11)

[Claims] 1. A laser beam emitting optical unit, comprising: a collimator lens for adjusting a focus and an emitting position of light emitted from a laser diode; A measuring step of measuring a three-dimensional position of the chip; and a measuring step of measuring the three-dimensional position of the laser chip measured in the measuring step.
An adjusting step of adjusting a three-dimensional position. 2. The method according to claim 1, wherein in the measuring step, when a position in an X direction and a direction in a Y direction, which is a direction orthogonal to a light emitting direction of the laser chip, is detected, the X direction position is a current blocking layer or an evaporation preventing layer of the laser chip. From the inner end face position of
2. The method according to claim 1, wherein the position in the Y direction is detected from an interface position between the active layer and the clad layer of the laser chip. 3. The light emitting position according to claim 2, wherein the position in the X direction is a central position between the inner end surfaces of the current blocking layer or a central position between the inner end surfaces of the evaporation preventing layer. The adjustment method of the laser beam emission optical unit described in the above. 4. In the measuring step, when detecting positions in an X direction and a Y direction which are directions orthogonal to a light emitting direction of the laser chip, the laser diode is caused to emit light and an X direction is determined from a position of the light emitting point. The method for adjusting a laser beam emitting optical unit according to claim 1, wherein the position of the laser beam emitting optical unit is detected. 5. In the measuring step, when detecting a position in a Z direction which is a direction parallel to a light emitting direction of the laser chip, an image of a surface of the laser chip is taken by a television camera connected to a microscope. The Z-direction position of the surface of the laser chip is detected by detecting with an image processing device that the surface of the laser chip has entered the depth of field of a microscope. Adjustment method of laser beam emission optical unit. 6. A laser beam emitting optical unit that emits two light beams, wherein a collimator lens is used to emit two light beams.
A method for adjusting a laser beam emission optical unit for adjusting a focus and an emission position of light emitted from two laser chips, comprising: a measurement step of measuring a three-dimensional position of each of the two laser chips; An adjusting step of adjusting a three-dimensional position of the collimator lens based on measurement information of a three-dimensional position of the two laser chips measured in the step. 7. In the measuring step, when detecting positions in an X direction and a Y direction which are directions orthogonal to a light emitting direction of the laser chip, the X direction position is determined by a current blocking layer or an evaporation preventing layer of the laser chip. From the inner end face position of
The method according to claim 6, wherein the Y direction position is detected from an interface position between the active layer and the cladding layer of the laser chip. 8. The light emitting position according to claim 7, wherein the position in the X direction is a central position between the inner end faces of the current blocking layer or a central position between the inner end faces of the evaporation preventing layer. The adjustment method of the laser beam emission optical unit described in the above. 9. In the measuring step, when detecting positions in an X direction and a Y direction which are directions orthogonal to a light emitting direction of the laser chip, the laser chip is caused to emit light, and from the position of the light emitting point, the X direction is detected. 7. The method for adjusting a laser beam emitting optical unit according to claim 6, wherein the position in the Y direction is detected. 10. In the measuring step, when detecting a position in a Z direction which is a direction parallel to a light emitting direction of the laser chip, an image of a surface of the laser chip is taken by a television camera connected to a microscope, and The position in the Z direction of the surface of the laser chip is detected by detecting that the surface of the laser chip has entered the depth of field of the microscope with an image processing device. Adjustment method of laser beam emission optical unit. 11. In the adjusting step, when a direction orthogonal to the light emitting direction of the laser chip is an XY direction and a direction parallel to the light emitting direction of the laser chip is a Z direction, the measuring step is performed for the XY direction. The center of the collimator lens is aligned with the center position of the two laser chips measured in the XY direction, and the collimator is positioned at a predetermined distance from the center position of the two laser chips in the XY direction in the Z direction. The method for adjusting a laser beam emitting optical unit according to claim 6, wherein the principal point position of the lens is adjusted.