JP5625756B2 - Manufacturing method of scanning optical device and adjustment amount calculation device used in manufacturing of scanning optical device - Google Patents

Description

  The present invention relates to a method for manufacturing a scanning optical device and an adjustment amount calculation device used at the time of manufacturing the scanning optical device.

  A light source, a coupling lens that converts light emitted from the light source into a light beam, a deflector that deflects the light beam that has passed through the coupling lens in the main scanning direction, and a light beam emitted from the deflector in the main scanning direction and sub-scanning 2. Description of the Related Art A scanning optical device including a scanning lens that focuses or refracts in a direction and forms an image on a surface to be scanned is known.

  Since the scanning optical device needs to form an image of a light beam on a fine point on the surface to be scanned, the accuracy of each optical component itself is required, and each optical component can realize a good imaging state. It is necessary to place it accurately. For example, in Patent Document 1, a light source unit (unit having a semiconductor laser and a coupling lens) that has been roughly adjusted is mounted on an optical unit (scanning optical device) that uses the light source unit to be adjusted, and is near the image plane. The adjustment state of the light source unit to be adjusted is calculated based on the result, and the interval between the semiconductor laser of the light source unit to be adjusted and the coupling lens is adjusted.

JP 2005-189260 A

  However, the conventional technology does not use the data acquired in the inspection of the individual optical components, but combines the optical components that have passed the inspection, and observes (measures) the imaging state of the combination to obtain the light source. The unit was adjusted and was inefficient.

  Therefore, the present invention uses the data obtained in the inspection of the optical component to realize efficient assembly of the scanning optical device, and the adjustment amount calculation used when manufacturing the scanning optical device. An object is to provide an apparatus.

In order to achieve the above object, the present invention includes a light source, a coupling lens that converts light emitted from the light source into a light beam, a deflector that deflects the light beam that has passed through the coupling lens in a main scanning direction, and Scanning optics comprising one scanning lens that focuses or refracts the light beam emitted from the deflector in the main scanning direction and the sub-scanning direction and forms an image on the surface to be scanned, and a housing that supports each of these optical components. A device manufacturing method comprising:
Inspecting the scanning lens to obtain a depth of focus end in the main scanning direction and sub-scanning direction of the scanning lens;
From the depth of focus end acquired in the inspection process,
Zml = (MDF_l + C1) / Mm
Zmu = (MDF_u-C1) / Mm
Zsl = (SDF_l + C2) / Ms
Zsu = (SDF_u−C2) / Ms
However,
Mm: vertical magnification in the main scanning direction Ms: vertical magnification in the sub-scanning direction C1, C2: positive constant MDF_l: smaller value of the depth of focus in the main scanning direction MDF_u: larger of the depth of focus in the main scanning direction One of the values SDF_l: the smaller value of the focal depth ends in the sub-scanning direction SDF_u: an adjustable amount calculating step for calculating the larger value of the focal depth ends in the sub-scanning direction;
Zml <Zmu
Zsl <Zsu
max {Zml, Zsl} <min {Zmu, Zsu}
An adjustment amount determining step for determining an adjustment amount Scp in the optical axis direction of the coupling lens in a range of max {Zml, Zsl} to min {Zmu, Zsu}
The scanning lens inspected in the inspection step is assembled to the casing, and the position of the coupling lens in the optical axis direction is determined in accordance with the adjustment amount Scp determined in the adjustment amount determination step. And an assembling step for assembling the housing. Note that when the vertical magnification is a positive value and the vertical magnification is substituted with a negative value, the right side of the above formula for calculating Zml, Zmu, Zsl, Zsu is multiplied by -1.

  In this way, the coupling lens can be moved (adjusted) in the adjustable amount calculation step using the depth of focus end in the main scanning direction and the depth of focus end in the sub-scanning direction measured in the inspection process. In the adjustment amount determination step, the adjustment amount Scp in the optical axis direction of the coupling lens is calculated. In the assembly step, the position of the coupling lens is adjusted according to the adjustment amount Scp. If the coupling lens is assembled to the housing, a scanning optical device having desired optical performance can be obtained. That is, the scanning optical device can be efficiently assembled using the inspection result of the scanning lens.

  In addition, according to the present invention, the position of the coupling lens in the optical axis direction has been conventionally discarded as a non-standard scanning lens that does not satisfy the specified depth of focus standard by measuring the focal depth end of the scanning lens. By adjusting, it became possible to use as much as possible.

The present invention also provides a light source, a coupling lens that converts light emitted from the light source into a light beam, a deflector that deflects the light beam that has passed through the coupling lens in a main scanning direction, and the light emitted from the deflector. At the time of manufacturing a scanning optical device comprising one scanning lens that focuses or refracts a light beam in the main scanning direction and the sub-scanning direction to form an image on the surface to be scanned, and a housing that supports each of these optical components, It can be configured as an adjustment amount calculation device that calculates an adjustment amount Scp of the position of the coupling lens in the optical axis direction with respect to the light source.
The adjustment amount calculation device includes an acquisition unit that acquires a depth of focus end in the main scanning direction and the sub-scanning direction of the scanning lens obtained by inspecting the performance of the scanning lens;
From the focal depth end acquired by the acquisition means,
Zml = (MDF_l + C1) / Mm
Zmu = (MDF_u-C1) / Mm
Zsl = (SDF_l + C2) / Ms
Zsu = (SDF_u−C2) / Ms
However,
Mm: vertical magnification in the main scanning direction Ms: vertical magnification in the sub-scanning direction C1, C2: positive constant MDF_l: smaller value of the depth of focus in the main scanning direction MDF_u: larger of the depth of focus in the main scanning direction One of the values SDF_l: the smaller one of the depth-of-focus ends in the sub-scanning direction SDF_u: an adjustable amount calculating means for calculating the larger value of the depth-of-focus ends in the sub-scanning direction;
Zml <Zmu
Zsl <Zsu
max {Zml, Zsl} <min {Zmu, Zsu}
Adjustment amount determining means for determining an adjustment amount Scp in the optical axis direction of the coupling lens in a range of max {Zml, Zsl} to min {Zmu, Zsu}
Output means for outputting the adjustment amount Scp determined by the adjustment amount determination means.

  According to such an apparatus, since the adjustment amount Scp of the coupling lens is output based on the end of the focal depth of the scanning lens, the adjustment amount Scp is acquired in the assembling process to efficiently assemble the scanning optical device. Can do.

  According to the present invention, it is possible to efficiently assemble a scanning optical device using the inspection result of the scanning lens.

It is a main scanning sectional view of a scanning optical device concerning one embodiment. It is a perspective view explaining a main scanning direction and a sub-scanning direction. It is a flowchart explaining the manufacturing process of a scanning optical apparatus. It is a flowchart explaining the manufacturing process of a scanning optical apparatus. It is a figure explaining a through focus curve. It is a graph which shows an example of the through focus curve of the main scanning direction. It is a graph which shows an example of the through focus curve of a subscanning direction. It is a figure explaining the relationship between the adjustable range and adjustment amount Scp.

Next, a manufacturing method according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, a scanning optical device 10 that is a target in the manufacturing method of one embodiment includes a light source unit 14, an aperture stop 3, a cylindrical lens 4, a polygon mirror 5 as an example of a deflector, and an example of a scanning lens. The fθ lens 6 is configured such that the laser light emitted from the light source unit 14 is condensed in a spot shape on the scanned surface 9A of the photosensitive drum 9 and scanned. Each of these optical components is fixed to the housing 20.

  The light source unit 14 includes a semiconductor laser 1 as an example of a light source and a collimator lens 2 as an example of a coupling lens. The semiconductor laser 1 and the collimating lens 2 are fixed (supported) to the light source support 14A.

  The semiconductor laser 1 has one or a plurality of light emitting elements. When the semiconductor laser 1 has a plurality of light emitting elements, the sub-scanning direction (the direction perpendicular to the main scanning direction. FIG. 1 shows the depth direction of the drawing. See also FIG. 2). A plurality of light emitting elements are arranged side by side (not shown). Note that the plurality of light emitting elements arranged to be shifted in the sub-scanning direction can be arranged to be slightly shifted in the main scanning direction as needed.

  The collimating lens 2 is a lens that converts laser light emitted from the semiconductor laser 1 into a light beam. This light beam may be any of parallel light, convergent light, and divergent light.

  The aperture stop 3 is a member having an aperture that defines the diameter of the light beam produced by the collimating lens 2.

  The cylindrical lens 4 is a lens that forms an image of the light beam that has passed through the collimating lens 2 and the aperture stop 3 on the mirror surface 5A of the polygon mirror 5 in the shape of a long line in the main scanning direction.

  The polygon mirror 5 is a member in which a plurality of mirror surfaces 5A are arranged at an equal distance from the rotation shaft 5B, and FIG. 1 illustrates an example having six mirror surfaces 5A. The polygon mirror 5 is rotated at a constant speed around the rotation axis 5B, and deflects the light beam that has passed through the cylindrical lens 4 in the main scanning direction. The direction in which the light beam is deflected is the main scanning direction (see also FIG. 2).

  Only one fθ lens 6 is provided in the scanning optical device 10. The fθ lens 6 converges or refracts the light beam deflected by being reflected by the polygon mirror 5 in the main scanning direction and the sub-scanning direction, thereby forming a spot image on the scanned surface 9A, and the polygon mirror The surface tilt of the mirror surface 5A is corrected. The fθ lens 6 has fθ characteristics such that the light beam deflected at a constant angular velocity by the polygon mirror 5 is scanned on the scanned surface 9A at a constant velocity. The fθ lens 6 has a pair of opposing lens surfaces L1 on the incident side (polygon mirror 5 side) and lens surface L2 on the emission side (scanned surface 9A side). As an example, these lens surfaces L1 and L2 are aspherical in the main scanning plane, and both are toric surfaces. The curvature of the lens surfaces L1 and L2 in the sub-scanning plane (cross section orthogonal to the main scanning direction) continuously changes from the axis of the optical axis A1 toward the outside of the main scanning direction in the effective portion. .

  As described above, since only one fθ lens 6 performs high-precision fθ conversion in the main scanning direction and surface tilt correction in the sub-scanning direction, the most complex light beam conversion among the above-described optical components is performed. Is what you do. Therefore, in order to accurately focus the light beam on the scanned surface 9A, the optical performance accuracy (shape accuracy) of the fθ lens 6 is the most important among the optical components, and each optical component is assembled to the housing 20. At this time, it is desirable to adjust the position of other optical components in accordance with the characteristics of the fθ lens 6. In the present embodiment, the image formation state on the scanned surface 9A is adjusted by adjusting the position of the collimating lens 2 with respect to the semiconductor laser 1 in accordance with the characteristics of the fθ lens 6.

Specifically, a method for manufacturing the scanning optical device of the present embodiment will be described with reference to the flowcharts of FIGS.
As shown in FIG. 3, in the manufacturing method of the present embodiment, the fθ lens 6 is inspected to obtain the depth of focus end in each of the main scanning direction and the sub-scanning direction (step S1, inspection process). For this inspection, a master scanning optical device in which an optical component other than the fθ lens 6 having sufficient accuracy is assembled at an accurate position is prepared, and the fθ lens to be inspected in the master scanning optical device. 6 is assembled. Then, the cross-sectional shape (light intensity distribution) of the light beam formed at a plurality of image height positions is measured to obtain a through focus curve described later.

  The depth of focus end is an amount displaced from the scanning surface 9A in the direction of the optical axis A1 (referred to as a defocus position, in this embodiment, the side far from the light source is a positive value and the near side is a negative value) And the diameter of the light beam, two values are a defocus position on the side far from the light source and a defocus position on the side near the light source when the desired light beam diameter is obtained. By measuring the size of the light beam in the main scanning direction and the size in the sub-scanning direction, two focal depth ends in the main scanning direction and two focal depth ends in the sub-scanning direction are obtained.

  Specifically, the depth of focus end can be well understood by looking at the through focus curve of the fθ lens 6. As shown in FIG. 5, the relationship between the defocus position and the beam diameter is plotted at each image height position (in FIG. 5, three points of −105 mm, 0 mm, and 105 mm are illustrated. Also see FIG. 1 for the image height). In the measurement at each image height position, a U-shaped curve ("" that the light beam diameter becomes the smallest at a predetermined defocus position and the light beam diameter becomes larger as the distance from the defocus position where the light beam diameter becomes the smallest. Defocus curve "). Of these plural defocus curves, a curve obtained by selecting and connecting the defocus curves showing the largest light beam diameter is a through focus curve (thick line in FIG. 5). If the image size guaranteed by the scanning optical device 10 (the maximum light beam diameter allowed on the scanned surface 9A) is called a reference light beam diameter, there are two defocus positions at which the through-focus curve takes the reference light beam diameter. It is the end of the depth of focus.

  Since the depth of focus end measured in step S1 is in both the main scanning direction and the sub-scanning direction, for example, in the main scanning direction, a reference light beam diameter Dm (for example, by a through focus curve such as a solid line in FIG. 6). As a defocus position having a beam diameter of 75 μm), a larger depth of focus end MDF_u (+8 mm) and a smaller depth of focus end MDF_l (−2 mm) can be obtained. Further, in the sub-scanning direction, the larger focal depth end SDF_u (+6.5 mm) is used as a defocus position having a light beam diameter of a reference light beam diameter Ds (for example, 95 μm) by a through focus curve as shown by a solid line in FIG. The smaller focal depth end SDF_l (−5.4 mm) can be obtained.

  The focal depth end determined in this way is a value that means that a desired (guaranteed) small image can be obtained in the range of the defocus position between the larger value and the smaller value. In other words, it means the end of the allowable range of focus position deviation. Even if the errors and assembly errors of all the parts constituting the scanning optical device 10 are taken into consideration, as long as the focus shift amount (defocus amount) is between the larger and smaller focus depth ends, other If the fθ lens 6 is fixed to the housing 20 at the designed position (within a predetermined tolerance range from the designed nominal dimension) together with the optical components, an image of a desired small size can be obtained on the scanned surface 9A. it can.

  Therefore, here, as an example, the fθ lens 6 is required in consideration of errors and assembly errors of all the components constituting the scanning optical device 10 (installed in the housing 20 without adjusting the position of the optical components). However, the defocus amount is assumed to be, for example, -4 mm to +4 mm in the main scanning direction and the sub-scanning direction. In other words, it is assumed that the half value C1 of the required depth of focus in the main scanning direction is 4 (mm) and the half value C2 of the required depth of focus in the sub-scanning direction is 4 (mm).

When C1 and C2 are set in this way,
In step S2,
MDF_l <−C1 (= −4) (1)
MDF_u> C1 (= 4) (2)
SDF_l <−C2 (= −4) (3)
SDF_u> C2 (= 4) (4)
Determine whether all of the above are satisfied.

  When all of these inequalities are satisfied (S2, Yes), an image with a desired small size can be obtained without adjusting the position of each optical component. Therefore, the adjustment amount Scp of the collimating lens 2 in the optical axis direction is set to 0, the fθ lens 6 is assembled to the housing 20 at the designed position, the collimating lens 2 is assembled to the light source support 14A at the designed position without adjusting the position, and the light source unit 14 is assembled to the housing 20 ( S3).

  On the other hand, if at least one inequality is not satisfied in step S2 (S2, No), in the past, it was discarded without using the fθ lens 6, but in this embodiment, it is possible after step S4. As much as possible, the adjustment amount Scp of the collimating lens 2 is calculated, and the position of the collimating lens 2 is adjusted during assembly so that the fθ lens 6 is used.

  As an example, in the through focus curves of FIGS. 6 and 7, the depth of focus SDF_l in the sub-scanning direction is smaller than −4 and SDF_m is larger than 4, thereby satisfying the above expressions (3) and (4). At the focal depth end in the main scanning direction, MDF_u is larger than 4 and satisfies Expression (2), but MDF_l is larger than −4 and does not satisfy Expression (1). 6 and FIG. 7 is a through focus curve when the focal position is moved by moving the collimating lens 2.

In step S4, first, the adjustable amounts Zml, Zmu, Zsl, Zsu are calculated by the following equation (S4, adjustable amount calculation step).
Zml = (MDF_l + 4) / Mm (5)
Zmu = (MDF_u-4) / Mm (6)
Zsl = (SDF_l + 4) / Ms (7)
Zsu = (SDF_u-4) / Ms (8)
However,
Mm: vertical magnification in the main scanning direction Ms: vertical magnification in the sub-scanning direction

  The vertical magnification is a value corresponding to (the movement amount of the focal position / the movement amount of the collimating lens) when the collimating lens 2 is moved in the optical axis direction. As described above, in the present invention, the vertical magnifications define the expressions (5) to (8) as positive values. When the vertical magnification is handled as a negative value, the expressions (5) to (8) are defined. The right side of is multiplied by -1. For example, in the case of Zml, the adjustable amount is obtained by dividing the difference between MDF_l and −4 by the vertical magnification Mm in the main scanning direction. This is an amount (amount with direction) to move the collimating lens 2 when it is assumed to be. The same applies to Zmu, Zsl, and Zsu.

Then, as shown in FIG. 4, in step S <b> 5, the relationship between the sizes of these adjustable amounts Zml, Zmu, Zsl, and Zsu is compared, and by adjusting the position of the collimator lens 2, a light beam diameter having a desired small size. Is determined. In particular,
Zml <Zmu (9)
Zsl <Zsu (10)
max {Zml, Zsl} <min {Zmu, Zsu} (11)
Judgment is satisfied. Note that max {a1, a2, a3,...} Means that the largest value is selected from the set of {a1, a2, a3,. ,... Means that the smallest value is selected from the set of {a1, a2, a3,. In the above equation, when one of the two focal depth ends in the main scanning direction is within −4 mm to 4 mm, the other is moved outside −4 mm to 4 mm, and the other is −4 mm to 4 mm. When one of the two focal depth ends in the sub-scanning direction is within -4 mm to 4 mm, one of them is outside -4 mm to 4 mm. It is confirmed whether the other does not enter within -4 mm-4 mm by moving. Further, the expression (11) confirms the same in the relationship between the depth of focus end in the main scanning direction and the depth of focus end in the sub-scanning direction. One of the four depth of focus ends is −4 mm. By moving it outside the range of ˜4 mm, it is confirmed whether the other depth of focus ends within the range of −4 mm to 4 mm.

  This will be described with reference to FIG. 8. One value is selected as the adjustment amount Scp, but the adjustment range (possible Scp value) for the main scanning direction and the adjustment for the sub-scanning direction. If there is an overlap in the possible range (possible Scp values), the adjustment amount Scp can be set. In FIG. 8, this overlapping range is indicated by RS.

  If any one of the expressions (9) to (11) is not satisfied (S5, No), even if the position of the collimating lens 2 is adjusted, the light beam diameter cannot be made smaller than a predetermined size at all image heights. (S10), the use of the fθ lens 6 for assembly is abandoned.

When all of the expressions (9) to (11) are satisfied (S5, Yes), the adjustment amount Scp of the collimating lens 2 is calculated by the following expression (12) (S6, adjustment amount determination step).
Scp = (max {Zml, Zsl} + min {Zmu, Zsu}) / 2 (12)
That is, the central value is selected from the range of possible adjustment amount Scp values (RS range in FIG. 8). In this way, by using the median value in the range of possible adjustment amount Scp, a margin as large as possible can be taken so that the luminous flux does not become larger than the desired diameter.

  When the adjustment amount Scp is determined, the fθ lens 6 is assembled to the housing 20 at the designed position (S7, assembly process). Then, the light source unit 14 is formed by assembling the semiconductor laser 1 and the collimator lens 2 to the light source support 14A. At this time, the position of the collimating lens 2 in the optical axis direction with respect to the semiconductor laser 1 is adjusted according to the adjustment amount Scp (S8, assembly process). Further, the created light source unit 14 and other optical components are assembled to the housing 20 at the designed positions (S9, assembling step).

  As described above, according to the method of manufacturing the scanning optical device 10 of the present embodiment, whether or not the position of the collimator lens 2 should be adjusted using the measurement result at the focal depth end of the fθ lens 6, If the adjustment is made, the adjustment amount Scp is calculated and the position of the collimating lens 2 is adjusted based on the adjustment amount Scp, thereby obtaining an image having a desired light beam diameter on the scanned surface 9A. be able to. Since the fθ lens 6 is not used only when adjustment is not possible in consideration of the adjustable range of the position of the collimating lens 2, fθ that has not been used because of insufficient performance is conventionally used. The lens 6 can also be used for assembly to improve the yield. As described above, according to the method for manufacturing the scanning optical device 10 of the present embodiment, the scanning optical device 10 can be efficiently manufactured.

Note that the present invention can be configured as an arithmetic unit for the adjustment amount Scp. That is, it is possible to input the depth-of-focus information to an arithmetic unit having a CPU, ROM, RAM, etc., and perform the processes from steps S2 and S4 to S6 to output the adjustment amount Scp. Specifically, the focus acquired by the acquisition means and the acquisition means for acquiring the depth of focus end in the main scanning direction and the sub-scanning direction of the scanning lens obtained by inspecting the performance of the scanning lens in a computer. Adjustable amount calculation means for calculating the expressions (5) to (8) from the depth end, and judging the inequalities of the expressions (9) to (11) and satisfying all of these, the collimation according to the expression (12) An adjustment amount determination unit that determines the adjustment amount Scp in the optical axis direction of the lens 2 and an output unit that outputs the adjustment amount Scp determined by the adjustment amount determination unit may be provided.
The acquisition of the focal depth end in the acquisition means may be input by an electrical signal from the inspection device of the fθ lens 6 or may be input by a person from a keyboard. The output means may output the adjustment amount Scp on the screen, and the operator of the process may check the adjustment amount Scp, or the adjustment amount Scp is sent to the assembly device of the collimating lens 2 as an electric signal. (Data) may be output.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be appropriately modified and implemented. For example, in the above-described embodiment, the semiconductor laser 1 and the collimating lens 2 are both supported by the light source support 14A, the light source unit 14 is assembled, and the light source unit 14 is assembled to the casing 20, whereby the collimating lens 2 is mounted on the casing. However, the collimating lens 2 may be directly assembled to the housing 20 without creating the light source unit 14.

  Further, the adjustment amount determining step or the adjustment amount determining means has selected the median of the range of possible adjustment amounts Scp according to the equation (12), but is not limited to the median, and max {Zml, Zsl} The adjustment amount Scp can be freely determined within the range of ~ min {Zmu, Zsu}.

  Furthermore, in the assembling process, as an example, the fθ lens 6 is first assembled to the housing 20 and then the collimator lens 2 is assembled. However, the assembly order of the fθ lens 6 and the collimator lens 2 is the first. The collimating lens 2 may be assembled to the housing 20 before the fθ lens.

  Moreover, although the polygon mirror 5 was illustrated as an example of a deflector, a galvanometer mirror can also be employ | adopted as a deflector.

DESCRIPTION OF SYMBOLS 1 Semiconductor laser 2 Collimating lens 4 Cylindrical lens 5 Polygon mirror 6 f (theta) lens 9 Photosensitive drum 9A Scanning surface 10 Scanning optical apparatus 14 Light source unit 14A Light source support 20 Case

Claims (6)

A light source, a coupling lens that converts light emitted from the light source into a light beam, a deflector that deflects the light beam that has passed through the coupling lens in a main scanning direction, and a light beam emitted from the deflector in the main scanning direction and A scanning optical device manufacturing method comprising: one scanning lens that focuses or refracts in a sub-scanning direction and forms an image on a scanned surface; and a housing that supports each of these optical components.
Inspecting the scanning lens to obtain a depth of focus end in the main scanning direction and sub-scanning direction of the scanning lens;
From the depth of focus end acquired in the inspection process,
Zml = (MDF_l + C1) / Mm
Zmu = (MDF_u-C1) / Mm
Zsl = (SDF_l + C2) / Ms
Zsu = (SDF_u−C2) / Ms
However,
Mm: vertical magnification in the main scanning direction Ms: vertical magnification in the sub-scanning direction C1, C2: positive constant MDF_l: smaller value of the depth of focus in the main scanning direction MDF_u: larger of the depth of focus in the main scanning direction One of the values SDF_l: the smaller value of the focal depth ends in the sub-scanning direction SDF_u: an adjustable amount calculating step for calculating the larger value of the focal depth ends in the sub-scanning direction;
Zml <Zmu
Zsl <Zsu
max {Zml, Zsl} <min {Zmu, Zsu}
An adjustment amount determining step for determining an adjustment amount Scp in the optical axis direction of the coupling lens in a range of max {Zml, Zsl} to min {Zmu, Zsu}
The scanning lens inspected in the inspection step is assembled to the casing, and the position of the coupling lens in the optical axis direction is determined according to the adjustment amount Scp determined in the adjustment amount determination step, and the coupling lens is A method of manufacturing a scanning optical device, comprising: an assembling step for assembling the housing. The adjustment amount determining step includes
Scp = (max {Zml, Zsl} + min {Zmu, Zsu}) / 2
The method of manufacturing a scanning optical apparatus according to claim 1, wherein the adjustment amount Scp is determined by: The focal depth ends in the main scanning direction and the sub-scanning direction obtained by the inspection process are as follows:
MDF_l <−C1
MDF_u> C1
SDF_l <−C2
SDF_u> C2
If all of the above are satisfied, the adjustment amount Scp is set to 0 without performing the adjustable amount calculation step and the adjustment amount determination step, and the coupling lens is placed at the position as designed in the assembly step. The method of manufacturing a scanning optical device according to claim 1, wherein the scanning optical device is assembled to a body.   In the assembling step, a light source unit is assembled by supporting the light source and the coupling lens together on a light source support, and the coupling lens is assembled to the casing by assembling the light source unit to the casing. The method for manufacturing a scanning optical device according to claim 1, wherein: A light source, a coupling lens that converts light emitted from the light source into a light beam, a deflector that deflects the light beam that has passed through the coupling lens in a main scanning direction, and a light beam emitted from the deflector in the main scanning direction and The coupling lens for the light source at the time of manufacturing a scanning optical device comprising one scanning lens that converges or refracts in the sub-scanning direction and forms an image on the surface to be scanned, and a housing that supports each of these optical components. An adjustment amount calculation device that calculates an adjustment amount Scp of the position in the optical axis direction of
An acquisition means for acquiring a depth of focus edge in the main scanning direction and the sub-scanning direction of the scanning lens, obtained by inspecting the performance of the scanning lens;
From the focal depth end acquired by the acquisition means,
Zml = (MDF_l + C1) / Mm
Zmu = (MDF_u-C1) / Mm
Zsl = (SDF_l + C2) / Ms
Zsu = (SDF_u−C2) / Ms
However,
Mm: vertical magnification in the main scanning direction Ms: vertical magnification in the sub-scanning direction C1, C2: positive constant MDF_l: smaller value of the depth of focus in the main scanning direction MDF_u: larger of the depth of focus in the main scanning direction One of the values SDF_l: the smaller one of the depth-of-focus ends in the sub-scanning direction SDF_u: an adjustable amount calculating means for calculating the larger value of the depth-of-focus ends in the sub-scanning direction;
Zml <Zmu
Zsl <Zsu
max {Zml, Zsl} <min {Zmu, Zsu}
Adjustment amount determining means for determining an adjustment amount Scp in the optical axis direction of the coupling lens in a range of max {Zml, Zsl} to min {Zmu, Zsu}
An adjustment amount calculation apparatus comprising: output means for outputting the adjustment amount Scp determined by the adjustment amount determination means. The adjustment amount determining means includes
Scp = (max {Zml, Zsl} + min {Zmu, Zsu}) / 2
The adjustment amount calculation device according to claim 5, wherein the adjustment amount Scp is determined by:

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