JP2001091882A - Optical writing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical writing device by which plural optical devices and a light emitting source can be respectively and independently driven in an optical axis direction by a driving means while respective parts can be guided by a common supporting and guiding means, and beam diameter in a main scanning direction, beam diameter in a sub-scanning direction and pitch in the sub-scanning direction on a surface to be scanned can be corrected well in a multi-beam optical scanner. SOLUTION: This device is provided with a light source unit1 consisting of the light emitting source 1a and an optical device 1c, a first optical system 20 guiding a light beam from the unit 1 to a deflector 4 by using plural optical devices 2 and 3, a second optical system 5 image-forming the optical beam deflected by the deflector 4 as a scanning line to the surface to be scanned, a detecting means set so as to be inclined in the main scanning direction on an image surface and detecting the image forming condition of the image forming beam on the surface to be scanned, and a correcting means correcting the image forming condition of the light beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical writing device of a writing optical system such as a digital copying machine or a printer, and more particularly to an optical writing device applicable to an image forming apparatus, a measuring instrument, an inspection apparatus, and the like. Device.

[0002]

2. Description of the Related Art Conventionally, there has been proposed an optical scanning device which adjusts a focal position of a laser beam by moving a focus lens in an optical axis direction. For example, JP-A-10-
Japanese Patent Application Laid-Open No. 20225 discloses a laser that detects a defocus amount of a beam spot on a scanned surface of a photoreceptor with a sensor, and moves a focus lens in the optical axis direction according to the defocus amount. The focus position of the beam is adjusted.

[0003]

However, in a multi-beam optical scanning device that scans a plurality of beams simultaneously, the focus position of the laser beam can be adjusted by moving the focus lens in the optical axis direction. The pitch of the beam in the sub-scanning direction on the surface to be scanned is shifted.

Further, when the optical lens is formed of resin, a change in the refractive index distribution and a change in the shape of the lens due to a rise in temperature causes a shift in the image forming position on the surface to be scanned and a change in the beam spot diameter. Conventionally, the imaging position on the surface to be scanned is corrected by moving the cylindrical lens in the optical axis direction to obtain an appropriate beam spot diameter. In this manner, the cylindrical lens is moved in the optical axis direction. If it is moved, the optical magnification in the sub-scanning direction before being deflected by the deflector changes greatly, and a good image cannot be obtained.

The present invention has been made to solve the above-mentioned problems of the prior art. In a multi-beam optical scanning device, a plurality of optical elements and light-emitting sources are independently driven by a driving means in the direction of the optical axis. And a common support and guide unit guides each unit, so that the beam diameter in the main scanning direction, the beam diameter in the sub-scanning direction, and the pitch in the sub-scanning direction on the surface to be scanned can be satisfactorily corrected. An object is to provide an optical writing device.

[0006]

According to the first aspect of the present invention,
A light source unit formed of a light emitting source and an optical element; a first optical system for guiding a light beam from the light source unit to a deflector using a plurality of optical elements; and a light scanning surface deflected by the deflector. To form a second image as a scanning line
An optical system, a detection unit that is installed with an inclination in the main scanning direction on the image plane, detects an imaging state of an imaging beam on the surface to be scanned, and a correction unit that corrects the imaging state of the beam. It is characterized by.

According to a second aspect of the present invention, in the first aspect of the present invention, the correction means includes a plurality of driving units for independently driving the plurality of optical elements and the light emitting source of the first optical system in the optical axis direction. Means and control means.

[0008] The invention described in claim 3 is the first or second invention.
In the above invention, the light emitting source has a plurality of light emitting points.

According to a fourth aspect of the present invention, in the first, second or third aspect, the detecting means comprises a two-dimensional light detection sensor and an electric circuit for driving the two-dimensional light detection sensor.

[0010] The invention according to claim 5 is the invention according to claims 1, 2,
In the invention described in 3 or 4, the beam imaging state in the main scanning direction is determined based on the distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor.

[0011] The invention according to claim 6 is based on claims 1 and 2,
In the invention described in 3 or 4, the beam imaging state in the sub-scanning direction is determined based on the distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor.

[0012] The invention according to claim 7 is the invention according to claims 1 and 2,
In the invention described in 3 or 4, the beam imaging state in the sub-scanning direction is determined based on the trajectory image of the scanning beam recorded on the two-dimensional light detection sensor.

[0013] The invention according to claim 8 is the first or second invention.
The invention according to the third or fourth aspect, characterized in that the pitch of the scanning beam is determined based on the distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor.

According to a ninth aspect of the present invention, there is provided the first and second aspects.
In the invention according to the third or fourth aspect, the pitch of the scanning beam is determined based on the trajectory image of the scanning beam recorded on the two-dimensional light detection sensor.

According to a tenth aspect of the present invention,
In the invention described in the item 3 or 4, the rotation speed of the deflector can be changed.

The eleventh aspect of the present invention is the first aspect of the present invention.
The invention according to the third or fourth aspect, characterized in that the imaging state of the imaging beam is detected by specifying the reflection surface of the deflector.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an optical writing apparatus according to the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a light source unit having a semiconductor laser as a light emitting source (hereinafter, referred to as an “LD unit”).
Is shown. The LD unit 1 includes an LD array 1a as a light emitting source having a plurality of light emitting points and emitting a plurality of light beams, and an aperture 1 for shaping the light beams into a predetermined shape.
b and a collimating lens 1c as an optical element for converting a light beam into parallel light.

The LD array 1a can be moved in the direction of the optical axis by first driving means 30, which will be described later. By moving the LD array 1a in the direction of the optical axis, the LD array 1a can be moved on the surface to be scanned. The scanning pitch of the light beam in the sub-scanning direction can be adjusted. A specific description of this will be described later.

A first optical system 20 composed of a plurality of optical elements for guiding a light beam emitted from the LD unit 1 to the rotary polygon mirror 4 as a deflector is arranged on the emission side of the LD unit 1. I have. The first optical system 20 includes a cylindrical lens 2 and a cylindrical lens 3. The cylindrical lens 2 has power only in the main scanning direction, while the cylindrical lens 3 has power only in the sub-scanning direction. The rotation speed of the rotating polygon mirror 4 is controlled by a control circuit 71. The control circuit 71 controls the rotation speed of the rotary polygon mirror 4 with high accuracy by controlling the frequency, voltage, current, and the like according to the type of motor used for the rotary polygon mirror 4.

The cylindrical lens 2 can be moved in the direction of the optical axis by a second driving means 40 (see FIG. 2) which will be described later, and by moving the cylindrical lens 2 in the direction of the optical axis. The light beam diameter in the main scanning direction can be adjusted. Further, the cylindrical lens 3 is also provided with a third driving unit 5 described later.
By moving the cylindrical lens 3 in the optical axis direction, the optical beam diameter in the sub-scanning direction can be adjusted by moving the cylindrical lens 3 in the optical axis direction. Specific description of these will be described later.

The first driving means 30, the second driving means 40, and the third driving means 50 constitute a plurality of driving means of a correcting means for correcting an image forming state of a beam, and include an LD array 1a, a cylindrical The lens 2 and the cylindrical lens 3 are independently driven in the direction of the optical axis, and are controlled by a control unit 10 constituting control means of the correction means. That is, the correction unit includes the first driving unit 30, the second driving unit 40, the third driving unit 50, and the control unit 10. The specific description of the first driving means 30, the second driving means 40, and the third driving means 50 will be described later.

On the reflection optical path of the light beam deflected by the deflecting / reflecting surface of the rotary polygon mirror 4, a plurality of light beams deflected by the rotary polygon mirror 4 are scanned by a scanning line with respect to the surface to be scanned of the photosensitive member 8. Lens 5 as a second optical system for forming an image, and a reflection mirror 7 for reflecting a light beam transmitted through the fθ lens 5 toward a surface to be scanned of the photoconductor 8. . A synchronization sensor 9 is provided immediately before the start of scanning. This synchronous sensor 9
Is for determining the timing of writing an image on the scanned surface of the photoconductor 8.

As shown in FIGS. 1 and 6, a two-dimensional image forming a detecting means is provided at a position equivalent to the surface to be scanned of the photosensitive member 8 and on a scanning line at the image plane position of the optical system. The light detection sensor 70 is installed at an inclination angle θ with respect to the main scanning direction. In FIG. 6, reference symbol A indicates a scanning direction, and reference symbol B indicates an image recording area. The synchronization sensor 9 is provided at a position immediately before the start of scanning outside the image recording area, and a two-dimensional light detection sensor 70 is provided at a position immediately after the scanning outside the image recording area on the opposite side. The two-dimensional light detection sensor 70 detects an image forming state of an image forming beam on the surface to be scanned, and is driven by an electric circuit 72 to process a detection signal. The detection means includes a two-dimensional light detection sensor 70 and an electric circuit 72.

As the two-dimensional light detection sensor 70, for example, a number of pixels of several μm, such as a CCD, are arranged on a two-dimensional plane, and when a light beam hits the pixels, electric charges are accumulated therein. A light accumulation sensor capable of detecting the intensity of the beam for each pixel and thereby detecting the imaging state of the imaging beam on the surface to be scanned can be used.

As described above, the two-dimensional light detection sensor 7
0 is set at an inclination angle θ with respect to the main scanning direction, so that when the light beam transmitted through the fθ lens 5 and reflected by the reflection mirror 7 passes through the two-dimensional light detection sensor 70, By receiving the light by the three-dimensional light detection sensor 70, a change in the defocus direction of the light beam can be detected. By driving the two-dimensional light detection sensor 70 by the electric circuit 72, the tilt angle θ can be set to an arbitrary tilt angle from 0 ° to 90 °. As the tilt angle θ increases, the light beam A change in the focus direction can be significantly detected. The light receiving signal of the light beam received by the two-dimensional light detection sensor 70 is input to the control unit 10 via the electric circuit 72.

FIG. 7 shows the beam diameter of the light beam in the main scanning direction when the focal position of the light beam is shifted in the defocus direction. The graph indicated by reference numeral 73 indicates the beam diameter at the time of focusing without any deviation in the defocus direction, and the graph indicated by reference numeral 74 indicates that the beam waist position (the position in the defocus direction where the light beam becomes narrowest) is shifted in the plus direction. The graph denoted by reference numeral 75 indicates the beam diameter when the beam waist position is shifted in the minus direction.

FIG. 8 shows the beam diameter of the light beam in the sub-scanning direction when the focal position of the light beam is shifted in the defocus direction. The graph indicated by reference numeral 76 indicates the beam diameter at the time of focusing without any deviation in the defocus direction, and the graph indicated by reference numeral 77 indicates that the beam waist position (the position in the defocus direction where the light beam becomes narrowest) is shifted in the plus direction. The graph indicated by reference numeral 78 indicates the beam diameter when the beam waist position is shifted in the minus direction. When an element, such as a plastic lens, whose optical characteristics change subtly due to a change in temperature is used as an optical element, the beam waist position is shifted in the defocus direction as shown in FIGS.

Next, the operation of the above embodiment will be described. As shown in FIG. 1, a light beam emitted from the LD array 1a of the LD unit 1 is shaped into a fixed shape by passing through an aperture 1b, and is converted into parallel light by passing through a collimating lens 1c. , Cylindrical lens 2, cylindrical lens 3
And is condensed near the deflection reflection surface of the rotary polygon mirror 4 as a linear image long in the main scanning direction. The light beam condensed near the deflecting / reflecting surface of the rotating polygon mirror 4 is deflected and reflected by the rotation of the rotating polygon mirror 4, passes through the fθ lens 5, is reflected by the reflecting mirror 7, and is scanned by the scanning surface of the photoconductor 8. The light is received by the two-dimensional light detection sensor 70 immediately after the upper portion is scanned.

Based on the light receiving signal of the two-dimensional light detection sensor 70 from the electric circuit 72, the control unit 10 controls the imaging state of the image beam on the surface to be scanned, that is, the sub beam of the light beam on the surface to be scanned. Each data value of the scanning pitch in the scanning direction, the light beam diameter in the main scanning direction, and the light beam diameter in the sub-scanning direction is calculated, and each data value is compared with a previously recorded normal value. Then, in order to make each of the data values a normal value, the first drive means 30, the second drive means 40, and the third drive means 50 are controlled to move the LD array 1a, the cylindrical lens 2, and the cylindrical lens 3 in the optical axis direction. Move to

It should be noted that not all of the LD array 1a, the cylindrical lens 2, and the cylindrical lens 3 are moved in the optical axis direction, but only those whose data values are different from the normal values. For example, the data values of the light beam diameter in the main scanning direction and the light beam diameter in the sub-scanning direction match the normal values, and only the data value of the scanning pitch of the light beam in the sub-scanning direction on the surface to be scanned is normal. If it is different from the value, only the first driving unit 30 is controlled, and the LD array 1a is moved in the optical axis direction by driving the first driving unit 30.

The rotation speed of the rotary polygon mirror 4 can be changed by changing the frequency, voltage, current and the like of the motor used for the rotary polygon mirror 4 by the control circuit 71. For example, by reducing the rotation speed of the rotary polygon mirror 4 by the control circuit 71, the speed of the scanning beam passing over the two-dimensional light detection sensor 70 can be reduced.
The scanning beam can be sufficiently illuminated and received,
An output signal having a good S / N ratio can be obtained, and the measurement can be performed with high accuracy.

As is well known, the rotary polygon mirror 4 is
Although it has a plurality of deflecting / reflecting surfaces, the setting angle of each deflecting / reflecting surface is slightly different from the viewpoint of processing accuracy. Therefore, when the above measurement is performed on a plurality of deflecting reflecting surfaces, a deviation occurs in the measured value for each deflecting reflecting surface. Therefore, the detection and measurement of the imaging beam can be performed with high accuracy by specifying the deflection / reflection surface of the rotary polygon mirror 4. For example, an image is formed by counting detection signals of the synchronous sensor 9 detected for each deflecting / reflecting surface of the rotating polygon mirror 4 and selecting a specific deflecting / reflecting surface by calculation from the number of deflecting / reflecting surfaces of the rotating polygon mirror 4. The beam detection measurement can be performed by specifying the deflection reflection surface of the rotary polygon mirror 4.

Next, the first driving means 30, the second driving means 40, and the third driving means 50, which are characteristic parts of the present invention, will be described. As described above, the first driving unit 30 moves the LD array 1a in the optical axis direction, the second driving unit 40 moves the cylindrical lens 2 in the optical axis direction, and the third driving unit 40 moves the LD array 1a in the optical axis direction. The driving means 50 moves the cylindrical lens 3 in the optical axis direction. FIG.
3 shows an exploded perspective view of the first driving means 30, the second driving means 40, and the third driving means 50, and FIG. 3 shows an assembled perspective view.

The first driving means 30 includes the carriage 1
h, a pulse motor 1i, a lead screw 1q, and the like. Hereinafter, a specific description will be given. As shown in FIGS. 2 and 3, the LD array 1a is fitted into the center hole of the base 1e, and is also pressed by the base 1e by the leaf spring 1f and inserted into the hole of the leaf spring 1f. 1g is fixed to the base 1e by being screwed into the base 1e. The collimator lens 1c is fitted into the center hole of the holder 11 and is fixed to the holder 11 by a set screw 1m inserted into a hole formed in the holder 11 in the radial direction. A hole 1p penetrated in the optical axis direction is formed in the carriage 1h. A base 1e is attached to one surface of the carriage 1h in which the hole 1p is formed (the surface on the near side in FIG. 2) so that the LD array 1a faces the hole 1p. Also, from the other side of the carriage 1h in which the hole 1p is formed, the hole 1p is formed.
The holder 11 is screwed into p, and the LD array 1a faces the collimating lens 1c.

Around the hole 1p of the carriage 1h,
A round hole 1n and a long hole 1o extending in the optical axis direction are formed. The round hole 1n and the long hole 1o constitute a part of the support and guide means, and are machined so as to be highly parallel to each other. As shown in FIG. 3, a shaft 11 as a guide member of the support and guide means extending in the optical axis direction is fitted in the round hole 1n in a highly accurate state with almost no gap. The carriage 1h is guided to move in the optical axis direction with the axis 11 as a reference. On the other hand, a shaft 12 extending in the optical axis direction, which constitutes a part of the support and guide means, is inserted into the elongated hole 1o so as to be in sliding contact with a part of the inner peripheral surface of the elongated hole 1o. This axis 1
Reference numeral 2 denotes an auxiliary member provided to guide the carriage 1h on the shaft 11 in the optical axis direction with high accuracy.

A screw 1k is provided on the upper surface of the carriage 1h.
This fixes the resin spring 1j. Resin spring 1j
A screw groove (not shown) is formed on the lower surface of the lead screw, and this screw groove is screwed with a lead screw 1q fixed to a housing in which the optical writing device is installed. A pulse motor 1i is attached to one end of the lead screw 1q. The rotation of the pulse motor 1i causes the rotation of the lead screw 1q, and the carriage 1h is moved in the optical axis direction by the lead of the lead screw 1q via the resin spring 1j. Moved to The rotational drive of the pulse motor 1i is controlled by the control unit 10.

Next, the second driving means 40 will be described. The second driving means 40 mainly includes a carriage 2h, a pulse motor 2i, a lead screw 2q, and the like. Hereinafter, a specific description will be given. As shown in FIGS. 2 and 3, the carriage 2h has a square hole 2 penetrated in the optical axis direction.
p is formed. The cylinder lens 2 is fitted into the square hole 2p, the cylinder lens 2 is pressed by the carriage 2h by the leaf spring 2r, and the screw 2s inserted into the hole of the leaf spring 2r is screwed into the carriage 2h. Is fixed to the carriage 2h.

Around the square hole 2p of the carriage 2h, a round hole 2n and a long hole 2o extending in the optical axis direction are formed. The round hole 2n and the long hole 2o constitute a part of the support and guide means, and are machined so as to be highly parallel to each other. As shown in FIG. 3, a shaft 11 as a guide member of a support guide extending in the optical axis direction is fitted in the round hole 2n in a highly accurate state with almost no gap. The carriage 2h is guided to move in the optical axis direction based on the shaft 11. On the other hand, a shaft 12 extending in the optical axis direction, which constitutes a part of the support and guide means, is inserted into the elongated hole 2o so as to be in sliding contact with a part of the inner peripheral surface of the elongated hole 2o. The shaft 12 is provided to assist the guide of the carriage 2h in the optical axis direction on the shaft 11 with high accuracy.

A screw 2k is provided on the upper surface of the carriage 2h.
This fixes the resin spring 2j. Resin spring 2j
A screw groove (not shown) is formed on the lower surface of the lead screw, and the screw groove is screwed with a lead screw 2q fixed to a housing in which the optical writing device is installed. A pulse motor 2i is attached to one end of the lead screw 2q. The rotation of the pulse motor 2i causes the lead screw 2q to rotate, and the carriage 2h is moved in the optical axis direction by the lead of the lead screw 2q via the resin spring 2j. Moved to The rotational drive of the pulse motor 2i is controlled by the control unit 10.

Next, the third driving means 50 will be described. The third driving means 50 mainly includes a carriage 3h, a pulse motor 3i, a lead screw 3q, and the like. Hereinafter, a specific description will be given. As shown in FIGS. 2 and 3, the carriage 3h has a square hole 3 penetrated in the optical axis direction.
p is formed. The cylindrical lens 3 is fitted into the square hole 3p, and the cylindrical lens 3 is pressed against the carriage 3h by a leaf spring 3r.
The screw 3s inserted into the hole of the leaf spring 3r is the carriage 3h.
Is fixed to the carriage 3h.

Around the square hole 3p of the carriage 3h, a round hole 3n and a long hole 3o extending in the optical axis direction are formed. The round hole 3n and the long hole 3o constitute a part of the supporting and guiding means, and are machined so as to be highly parallel to each other. As shown in FIG. 3, a shaft 11 as a guide member of the support and guide means extending in the optical axis direction is fitted in the round hole 3n in a highly accurate state with almost no gap. The carriage 3h is guided to move in the optical axis direction with the axis 11 as a reference. On the other hand, the shaft 12 extending in the optical axis direction, which constitutes a part of the support and guide means, is inserted into the elongated hole 3o so as to be in sliding contact with a part of the inner peripheral surface of the elongated hole 3o. The shaft 12 is provided to assist the guide of the carriage 3h in the optical axis direction on the shaft 11 with high accuracy.

A screw 3k is provided on the upper surface of the carriage 3h.
This fixes the resin spring 3j. Resin spring 3j
A screw groove (not shown) is formed on the lower surface of the lead screw, and this screw groove is screwed with a lead screw 3q fixed to a housing in which the optical writing device is installed. A pulse motor 3i is attached to one end of the lead screw 3q. The rotation of the pulse motor 3i causes the lead screw 3q to rotate, and the carriage 3h is moved in the optical axis direction by the lead of the lead screw 3q via the resin spring 3j. Moved to The rotational drive of the pulse motor 3i is controlled by the control unit 10.

As described above, the support and guide means includes the shaft 11 as a guide member, the shaft 12 for assisting the guide of the shaft 11, the round holes 1n, 2n, 3n, and the elongated holes 1o, 2o, 3o. , The LD array 1a, the cylindrical lens 2 and the cylindrical lens 3, and guides the movement in the optical axis direction. That is, the LD array 1a
Is supported by the shaft 11 fitted into the round hole 1n of the carriage 1h and the shaft 12 inserted into the elongated hole 1o. Move to is guided. The rotation of the pulse motor 1i causes the lead screw 1q to rotate, whereby the carriage 1 is moved via the resin spring 1j.
h moves in the optical axis direction, so that the LD array 1a
Can be moved in the optical axis direction while being guided by the shaft 11, and the scanning pitch of the light beam in the sub-scanning direction on the surface to be scanned can be adjusted.

The cylindrical lens 2 is supported by the shaft 11 fitted in the round hole 2n of the carriage 2h and the shaft 12 inserted in the elongated hole 2o, and the carriage 2h is guided by the shaft 11. This guides the movement in the optical axis direction. In addition, the pulse motor 2i
The lead screw 2q is rotated by this rotation, whereby the carriage 2h moves in the optical axis direction via the resin spring 2j, so that the cylindrical lens 2 can move in the optical axis direction while being guided by the shaft 11. ,
The light beam diameter in the main scanning direction can be adjusted.

The cylindrical lens 3 is supported by the shaft 11 fitted in the round hole 3n of the carriage 3h and the shaft 12 inserted in the elongated hole 3o, and the carriage 3h is guided by the shaft 11. This guides the movement in the optical axis direction. Also, the pulse motor 3i
The lead screw 3q is rotated by this rotation, whereby the carriage 3h moves in the optical axis direction via the resin spring 3j, whereby the cylindrical lens 3 can move in the optical axis direction while being guided by the shaft 11. ,
The light beam diameter in the sub-scanning direction can be adjusted.

As described above, the LD array 1a, the cylindrical lens 2, and the cylindrical lens 3
It is guided by a book shaft 11. In other words, axis 1
1 is shared by the LD array 1a, the cylindrical lens 2, and the cylindrical lens 3. Therefore,
The relative positional accuracy of the LD array 1a, the cylindrical lens 2, and the cylindrical lens 3 can be kept high.

In the LD array 1a, the cylindrical lens 2, and the cylindrical lens 3, the shafts 11 and 12 have the mounting portions 20a, 20b, 20c, 20d, 21
By being attached to the optical writing devices a, 21b, 21c, and 21d, the optical writing device is provided so as to be movable in the optical axis direction. As shown in FIGS. 3 and 4, mounting portions 20a and 20
b, 20c, 20d, 21a, 21b, 21c, 21d
Is provided. More specifically, the mounting portion 20
a, 20b, 20c, and 20d are provided in this order at appropriate intervals in the optical axis direction and in the light beam emission direction. In addition, the mounting portions 21a, 21b, 21c, 21d also
In this order, they are provided at appropriate intervals in the optical axis direction and the light beam emission direction. In addition, the mounting portion 20a and the mounting portion 21a, the mounting portion 20b and the mounting portion 21b,
c and the mounting portion 21c, and the mounting portion 20d and the mounting portion 21d are arranged to face each other.

The mounting portions 20a, 20b, 20c, 20
Each of d, 21a, 21b, 21c, and 21d is formed in a stepped shape having an L-shaped cross section, and has a surface B parallel to the optical axis direction and a surface A perpendicular to the surface B. . The surface A of the mounting portions 20a, 20b, 20c, 20d is a reference for installation in a direction perpendicular to the optical axis direction of the shaft 11 of the supporting and guiding means, and is provided on the same extension surface with high precision. . Also, the mounting portions 21a, 21b, 21c, 21
The surface B of d serves as an installation reference in a direction perpendicular to the optical axis direction of the shaft 12 of the support and guide means, and is provided on the same extension surface with high precision. The surface A and the surface B can be formed into a high-precision processing surface using, for example, machining. In the case of molding such as injection molding or die-casting, a high-precision identical die is used. A surface can be formed.

The shaft 11 is provided with mounting portions 20a, 20b, 2
0c and 20d are in contact with both surface A and surface B,
The leaf spring 60 presses against the surfaces A and B,
The mounting portion 2 is formed by screws 61 inserted into holes formed in the mounting portion 2.
0a, 20b, 20c, and 20d. The shaft 12 is in contact with both the surface A and the surface B of the mounting portions 21a, 21b, 21c, and 21d, and is pressed by the surface A and the surface B by the plate spring 60 to form the plate spring 60. With the screws 61 inserted into the holes, the mounting portions 21a, 21b,
It is fixed to 21c, 21d. As described above, since the surface A and the surface B of each mounting portion are formed and provided with high precision, the movement of the carriages 1h, 2h, 3h can be improved with high accuracy, and the LD array 1a, The cylindrical lens 2 and the cylindrical lens 3 can be moved in the optical axis direction with high accuracy.

The pulse motors 1i, 2i, 3i
Between the carriage 1h, 2
This is an important factor for improving the stability of the movement of h and 3h. FIG. 5 shows the relationship between the pulse motor 2i and the shaft 11. As shown in FIG.
The distance between the center axis of i, that is, the center axis of the lead screw 2q and the center of the shaft 11 is d, and the carriage 2h
When the contact points between the shaft 11 and the shaft 11 are P and Q, the driving force F of the pulse motor 2i generates reaction forces R at the contact points P and Q in directions perpendicular to the shaft 11 and opposite to each other. A friction force μR (μ = friction coefficient) in the same direction is generated. The contact point between the extension line of the resultant force of the reaction force R and the frictional force μR at the contact point P and the extension line of the resultant force of the reaction force R and the frictional force μR at the contact point Q is defined as O. When the vertical distance is x, according to the principle of the narrow guide,
If the distance d <x, the carriage 2h can move in the optical axis direction, but if d> x, the carriage 2h
Cannot move in the optical axis direction. This is because an eccentric load is generated due to the positional relationship between the pulse motor 2i and the shaft 11, and the carriage 2h is twisted and meshes with the shaft 11.

Therefore, the pulse motors 1i, 2i, 3i and the shaft 11 must be arranged so as to satisfy the distance d <x.
With the arrangement of i, 2i, 3i and the shaft 11, the carriages 1h, 2h, 3h can be moved in the optical axis direction, but the carriages 1h, 2h, 3h can be moved with high precision and stability. Can not. Therefore, the pulse motor 1 is set so that the vertical distance x is sufficiently larger than the distance d.
i, 2i, 3i and the shaft 11 must be arranged.
Therefore, in the above embodiment, the distance d is made as small as possible to reduce the distance between the pulse motors 1i, 2i, 3i and the shaft 11. That is, the pulse motors 1i, 2i,
The driving point 3i is located near the shaft 11. As a result, the generation of an extra moment due to the eccentric load generated on the shaft 11 of the carriage can be prevented, the power consumption of the pulse motor can be reduced, and the life of the shaft 11 can be extended. Further, the LD array 1a, the cylindrical lens 2, and the cylindrical lens 3 can be moved in the optical axis direction with high precision and smoothness. Also, axis 1
Assuming that the diameter of the shaft 1 is b and the distance between the contact point P and the contact point Q in the optical axis direction is 1, the diameter b of the shaft 11 is made as large as possible and the value of b / l is made small.
h, 2h and 3h can be moved more accurately and stably.

As described above, the carriages 1h, 2h
When the shafts h and 3h move in the direction of the optical axis, frictional force is generated at the contact portions between the shaft 11 and the carriages 1h, 2h and 3h. Therefore, a sintered metal bearing or a ball bearing is used for the contact portions. Thus, the frictional force can be reduced. However, when a sintered metal bearing, a ball bearing, or the like is used, the number of parts increases and the cost increases accordingly. Further, since a sintered metal bearing or a ball bearing is used, the positional accuracy between the shaft 11 and the carriage may be deteriorated. Therefore, a sintered metal bearing or a ball bearing may be used in consideration of the load on the carriage, the moving speed of the carriage, and the like.

Next, detection by the two-dimensional light detection sensor 70 will be described. FIG. 9 shows a two-dimensional light detection sensor 70.
The light output when the two-dimensional light detection sensor 70 receives the light beam when passing through the upper part, that is, the two-dimensional light detection sensor 70
2 shows the distribution of the received light intensity of the scanning beam recorded in FIG. In FIG. 9, X is the main scanning direction and Y is the sub-scanning direction. Pixels of i = 0 to n are arranged in the main scanning direction, and pixels of j = 0 to m are arranged in the sub-scanning direction.

FIG. 10 shows the data when the distribution of the received light intensity of the scanning beam shown in FIG. 9 is viewed from the direction of the arrow α, that is, the trajectory image of the scanning beam recorded on the two-dimensional light detection sensor 70. This data is consistent with the characteristics of the change of the beam diameter in the sub-scanning direction in the defocus direction. This is because the two-dimensional light detection sensor 70 is installed with an inclination in the main scanning direction on the image plane, and as the light beam scans the light receiving surface of the two-dimensional light detection sensor 70, the optical path length becomes continuous. Because it changes to In the data shown in FIG. 10, the thinnest part of the image in the sub-scanning direction is the beam waist position in the sub-scanning direction of the light beam. By calculating by calculation the position where the image becomes thinnest in the sub-scanning direction, it is possible to determine the beam imaging state in the sub-scanning direction. The beam diameter can be adjusted.

When the two-dimensional light detection sensor 70 is installed, it is necessary to determine in advance which position coincides with the image plane in the main scanning direction which is the X direction. You can ask if you are away. That is, the position where j = p in the sub-scanning direction (the sub-scanning position of the light beam) may be obtained.

There are two methods for obtaining the narrowest position of the image in the sub-scanning direction by calculation. The first method is based on the trajectory image of the scanning beam recorded on the two-dimensional light detection sensor 70 shown in FIG. 10, and calculates the image in the sub-scanning direction from the difference between the maximum pixel and the minimum pixel in the sub-scanning direction Y of the recorded image. Is a method of calculating the position where is thinnest. In this method, if the average value of the maximum pixel and the minimum pixel in the sub-scanning direction Y of the recorded image is obtained for each of the plurality of beams, the pitch of the scanning beam can be determined. That is, the pitch of the scanning beam can be determined based on the trajectory image of the scanning beam recorded on the two-dimensional light detection sensor 70, and the light beam diameter in the sub-scanning direction can be adjusted.

In the second method, the center of the scanning beam in the sub-scanning direction and the width of the scanning beam are obtained based on the distribution of the received light intensity of the scanning beam shown in FIG. Is calculated. In other words,
A method of interpolating the light intensity distribution in the sub-scanning direction arranged in the main scanning direction with a function distribution such as a Gaussian distribution or a polynomial function distribution, and obtaining the position of the scanning beam in the sub-scanning direction and the beam diameter in the sub-scanning direction from the result It is. Also, in this method,
If the center of the scanning beam in the sub-scanning direction and the width of the scanning beam are obtained for each of the plurality of beams, the pitch of the scanning beam can be determined. That is, the pitch of the scanning beam can be determined based on the distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor 70, and thus the diameter of the light beam in the sub-scanning direction can be adjusted.

FIG. 11A shows data when the distribution of the received light intensity of the scanning beam shown in FIG. 9 is viewed from the direction of the arrow α.
In other words, the trajectory image of the scanning beam recorded on the two-dimensional light detection sensor 70 is shown, and this data matches the characteristic of the change in the beam diameter in the main scanning direction in the defocus direction. As shown in FIG. 11A, at the beam waist position of the light beam in the main scanning direction, the beam diameter in the main scanning direction is the smallest. That is, light is dense in the main scanning direction.

Therefore, the light detection amounts of pixels at the same position in the main scanning direction (pixels with the same number i) are integrated for pixels from j = 0 to m in the sub-scanning direction, that is, the integrated intensity Si = Σ (Pij) _{j = 0 to m} , i = _{0 to n}
11B, the distribution of the received light intensity shown in FIG. 11B is obtained. This distribution of the received light intensity is a distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor 70. In the distribution of the received light intensity shown in FIG.
Is the maximum value, the position of i is the beam waist position in the main scanning direction of the light beam. The beam imaging state in the main scanning direction can be determined based on the distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor 70 shown in FIG. The diameter of the light beam in the main scanning direction can be adjusted by obtaining the diameter.

[0060]

According to the first aspect of the present invention, a light source unit formed of a light emitting source and an optical element, and a first optical system for guiding a light beam from the light source unit to a deflector using a plurality of optical elements. System, a second optical system that forms an image of the light beam deflected by the deflector as a scanning line on the surface to be scanned, and is installed with an inclination in the main scanning direction on the image surface,
A simple configuration without using a high-speed electric circuit for signal processing, etc., because it includes a detection unit that detects the imaging state of the imaging beam on the surface to be scanned and a correction unit that corrects the imaging state of the beam. Can detect the imaging state of the imaging beam on the surface to be scanned, and satisfactorily correct the beam diameter in the main scanning direction, the beam diameter in the sub scanning direction, and the pitch in the sub scanning direction on the surface to be scanned. be able to.

According to a second aspect of the present invention, in the first aspect of the present invention, the correction means is configured to independently drive the plurality of optical elements and the light emitting source of the first optical system in the optical axis direction. Since it is composed of a plurality of driving means and control means, the beam diameter in the main scanning direction, the beam diameter in the sub-scanning direction,
And the pitch in the sub-scanning direction on the surface to be scanned can be satisfactorily and independently corrected.

According to the invention described in claim 3, according to claim 1,
In the invention according to the second aspect, since the light emitting source has a plurality of light emitting points, the beam diameter in the main scanning direction, the beam diameter in the sub scanning direction, and the , The pitch in the sub-scanning direction can be satisfactorily and independently corrected.

According to the invention described in claim 4, according to claim 1,
In the invention described in 2 or 3, since the detection means comprises a two-dimensional light detection sensor and an electric circuit for driving the two-dimensional light detection sensor, the characteristics of a light beam scanned by a light beam can be grasped instantaneously and an output signal can be obtained. Can be analyzed at a low speed, and it is not necessary to use a high-speed processing circuit as in the related art, and cost can be reduced.

According to the fifth aspect of the invention,
In the invention described in 2, 3, or 4, the beam imaging state in the main scanning direction is determined based on the distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor. The beam imaging state in the main scanning direction can be determined with high accuracy without being adversely affected.

According to the invention described in claim 6, according to claim 1,
In the invention described in 2, 3, or 4, since the beam imaging state in the sub-scanning direction is determined based on the distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor, detection errors and noises are reduced. The beam imaging state in the sub-scanning direction can be determined with high accuracy without being adversely affected.

According to the invention of claim 7, according to claim 1,
In the invention described in 2, 3, or 4, since the beam imaging state in the sub-scanning direction is determined based on the trajectory image of the scanning beam recorded on the two-dimensional photodetection sensor, the arithmetic processing is simple and the measurement time and The beam imaging state in the sub-scanning direction can be determined by shortening the analysis time.

According to the invention described in claim 8, according to claim 1,
In the invention described in 2, 3, or 4, since the pitch of the scanning beam is determined based on the distribution of the received light intensity of the scanning beam recorded on the two-dimensional photodetection sensor, there is no adverse effect such as a detection error or noise. The pitch of the scanning beam can be determined with high accuracy.

According to the ninth aspect of the present invention, the first aspect has the following features.
In the invention described in 2, 3, or 4, since the pitch of the scanning beam is determined based on the trajectory image of the scanning beam recorded on the two-dimensional light detection sensor, the arithmetic processing is simple and the measurement time and the analysis time are shortened. Thus, the pitch of the scanning beam can be determined.

According to the tenth aspect of the present invention, in the first, second, third, or fourth aspect, the rotation speed of the deflector can be changed. By reducing the speed, the speed of the scanning beam passing over the two-dimensional light detection sensor can be reduced, whereby the two-dimensional light detection sensor can be sufficiently irradiated with the scanning beam and received, and An output signal having a good N ratio can be obtained, and the measurement can be performed with high accuracy.

According to the eleventh aspect of the present invention, in the first, second, third, or fourth aspect of the invention, the detection of the imaging state of the imaging beam is performed by specifying the reflection surface of the deflector. The detection measurement of the imaging beam can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is an optical layout diagram showing an embodiment of an optical writing device according to the present invention.

FIG. 2 is an exploded perspective view showing a first driving unit, a second driving unit, and a third driving unit applicable to the embodiment.

FIG. 3 is an assembled perspective view showing the first driving means, the second driving means, and the third driving means.

FIG. 4 is another assembly perspective view showing the first driving means, the second driving means, and the third driving means.

FIG. 5 is a plan view showing a positional relationship between the first driving unit, the second driving unit, and the third driving unit and a supporting and guiding unit.

FIG. 6 is another optical layout showing the above embodiment.

FIG. 7 is a graph showing a light beam diameter in the main scanning direction in the embodiment.

FIG. 8 is a graph showing a light beam diameter in the sub-scanning direction in the embodiment.

FIG. 9 is a graph showing the distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor applicable to the embodiment.

FIG. 10 is a graph showing a trajectory image of a scanning beam recorded on a two-dimensional light detection sensor applicable to the embodiment.

FIG. 11A is a graph showing the distribution of the received light intensity of the scanning beam recorded on the two-dimensional light detection sensor applicable to the above embodiment, and FIG. 11B is a graph showing the locus image thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source unit 1a LD array 2 Cylindrical lens 3 Cylindrical lens 4 Rotating polygon mirror 5 fθ lens 8 Photoconductor 9 Synchronous sensor 10 Control unit 20 First optical system 30 First driving unit 40 Second driving unit 50 Third driving unit 70 2 Dimensional light detection sensor 71 Control circuit 72 Electric circuit

Claims (11)

[Claims] A light source unit formed of a light emitting source and an optical element; a first optical system for guiding a light beam from the light source unit to a deflector using a plurality of optical elements; and light deflected by the deflector. A second optical system that forms an image of the beam as a scanning line on the surface to be scanned, and a detection unit that is installed with an inclination in the main scanning direction on the image surface and detects an imaging state of the image forming beam on the surface to be scanned. An optical writing device comprising: a correction unit configured to correct a beam imaging state. 2. The apparatus according to claim 1, wherein the correcting means comprises a plurality of driving means and a plurality of control means for independently driving the plurality of optical elements and the light emitting source of the first optical system in the optical axis direction. The optical writing device according to claim 1. 3. The optical writing device according to claim 1, wherein the light emitting source has a plurality of light emitting points. 4. The optical writing device according to claim 1, wherein said detection means comprises a two-dimensional light detection sensor and an electric circuit for driving the two-dimensional light detection sensor. 5. A beam imaging state in a main scanning direction is determined based on a distribution of a received light intensity of a scanning beam recorded on the two-dimensional light detection sensor.
5. The optical writing device according to 3 or 4. 6. A beam imaging state in a sub-scanning direction is determined based on a distribution of light receiving intensity of a scanning beam recorded on the two-dimensional light detection sensor.
5. The optical writing device according to 3 or 4. 7. A beam imaging state in a sub-scanning direction is determined based on a trajectory image of a scanning beam recorded on the two-dimensional photodetection sensor. Optical writing device. 8. The light according to claim 1, wherein a pitch of the scanning beam is determined based on a distribution of a received light intensity of the scanning beam recorded on the two-dimensional light detection sensor. Writing device. 9. The optical writing according to claim 1, wherein a pitch of the scanning beam is determined based on a trajectory image of the scanning beam recorded on the two-dimensional light detection sensor. apparatus. 10. The optical writing device according to claim 1, wherein the rotation speed of the deflector can be changed. 11. The method according to claim 1, wherein the imaging state of the imaging beam is detected by specifying the reflection surface of the deflector.
5. The optical writing device according to 2, 3, or 4.