JP2001305453A - Optical scanner, line image forming optical system in optical scanner, image-formation adjustment method in optical scanner and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce an image plane fluctuation in the main scanning direction and the subscanning direction caused by a temperature change, by using an optical element made of a resin easy in processing and assembling, without using a mechanical mechanism nor narrowing the latitude of designs. SOLUTION: The line image forming optical system in an optical scanner which sets a beam from a light source 1 as a beam having a prescribed beam form with a coupling optical system 2, image-forms the beam as a long line image in the main scanning direction with line image forming optical systems 3, 4, deflects it with a light deflector 5 having a deflection reflecting surface near the image forming position of the line image, condenses a deflection beam toward a surface to be scanned 7 with a scanning image forming optical system 60, forms a light spot on the surface to be scanned 7 to perform the optical scanning of the surface to be scanned 7 has one or more lenses 3 made of a resin, and one or more glass lenses 4. The lens 3 made of a resin includes two planes having negative power in the subscanning direction and at least one plane having negative power in the main scanning direction. The power of each surface of the lens 3 made of a resin is set so that the image plane fluctuation caused by the temperature change of the coupling optical system and/or the scanning image forming optical system is effectively reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical scanning device, a line image forming optical system in the optical scanning device, an imaging adjustment method in the optical scanning device, and an image forming apparatus.

[0002]

2. Description of the Related Art Optical scanning devices are widely known in relation to digital copying machines, laser printers and the like. In these optical scanning devices, "a beam from a light source (which means" light beam "in this specification) is converted into a beam having a predetermined beam form by a coupling optical system, and this beam is formed by a line image forming optical system in the main scanning direction. The beam is deflected by an optical deflector having a deflecting / reflecting surface in the vicinity of the image forming position of the line image, and the deflected beam is condensed toward the surface to be scanned by the scanning image forming optical system. A light spot is formed on a surface to perform optical scanning of the surface to be scanned ".
In this way, the beam from the light source side is formed as a long line image in the main scanning direction in the vicinity of the deflecting reflection surface of the optical deflector by the line image forming optical system. Correction ”can be performed. In recent years, digital copiers and laser printers have been required to have a higher image density, and the spot diameter of a light spot formed on a surface to be scanned tends to be smaller. Further, in order to realize a “special surface shape” required for cost reduction and reduction in diameter, resin elements of optical elements constituting an optical scanning optical system are being developed. The light spot is formed by converging a deflection beam deflected by an optical deflector toward a surface to be scanned by a scanning imaging optical system, and ideally is formed by a beam waist of the converging deflection beam. Things. In the optical scanning device having the above configuration, the scanning image forming optical system is an “anamorphic optical system having different powers in the main scanning direction and the sub-scanning direction”. Therefore, the beam waist position of the deflected beam in the main scanning direction is used. And the beam waist position in the sub-scanning direction generally do not completely match. The beam waist positions in the main scanning direction and the sub-scanning direction are connected to each other in image planes in the main scanning direction and the sub-scanning direction, and these are curved according to the field curvature of the optical system. In order to perform good optical scanning with a “light spot having a small diameter in both the main scanning direction and the sub-scanning direction”, the beam waist position in the main scanning and sub-scanning direction must be set at the “position of the light spot in the main scanning direction ( Irrespective of the image height), it is necessary that the image plane in the main scanning direction and the sub-scanning direction substantially coincide with the surface to be scanned. The optical design is performed so as to satisfactorily correct the field curvature in the main scanning and sub scanning directions.

[0003] However, no matter how good a design result is, it does not mean that a design optical characteristic is actually realized. For example, if there is a processing error or an assembling error in a general fθ lens as a scanning imaging optical system, the actual image plane position of the deflected beam is shifted with respect to the position of the surface to be scanned. "Increase in diameter" than the value of. fθ lens etc. "substantially as designed"
If it is created and assembled with high accuracy, a light spot having a spot diameter substantially as designed can be formed on the scanned surface, but if the fθ lens includes a `` resin lens '', When the temperature in the optical scanning device changes, "a change in the refractive index or shape of the resin lens" occurs, causing "image surface fluctuation" in which the image surface is shifted with respect to the surface to be scanned, and the spot diameter increases. . Further, when the metal holder that holds the coupling optical system expands or contracts due to the temperature change, the distance between the coupling optical system and the light source changes by a small distance, and the coupling action changes, which also increases the spot diameter. Cause. The direction of the image plane fluctuation (the direction in which the image plane moves) due to the “temperature change” of the resin lens occurs in opposite directions when the power of the resin lens is positive and when the power of the resin lens is negative. On the optical path from to the optical deflector, a “resin lens with the opposite power to the fθ lens resin lens” is deployed, and by adjusting each power, the fluctuation of the image plane due to the temperature change It is possible to cancel each other (Japanese Unexamined Patent Publication No. Hei 8
-292388, Japanese Patent No. 2804647). In the method described in JP-A-8-292388,
Since the resin lens provided between the light source and the optical deflector "has no power in the main scanning direction", there is no correction function for image plane fluctuation in the main scanning direction due to a temperature change. The spot diameter cannot be prevented from increasing.
In all the embodiments described in JP-A-8-292388, the “resin lens having negative power” for correction is constituted by a plano-concave cylindrical lens, but as described in the embodiments, The radius of curvature is considerably small, about 5 mm to 8 mm, and the processing accuracy and assembly accuracy are severe. This is because the correction function for the temperature change is provided on only one surface.

[0004] Japanese Patent No. 2804647 discloses an image plane in the main scanning direction using a resin lens having a power "the absolute value is equal and the sign is opposite" to the power of the resin lens included in the scanning image forming optical system. It is disclosed that the image plane fluctuation in the sub-scanning direction is “suppressed to a level that does not cause a problem” by correcting the fluctuation and limiting the position of the scanning image forming optical system. According to this method, “image plane fluctuation due to temperature change” can be effectively reduced in both the main scanning direction and the sub-scanning direction. However, since the arrangement of the scanning imaging optical system is restricted, the optical scanning The degree of freedom in the optical design of the device is greatly limited. JP-A-10-20225 and Japanese Patent No. 27617
No. 23 discloses a method of mechanically moving a collimating lens or the like in the optical axis direction to correct the image plane fluctuation. A "detection component" or the like is required, which increases the cost and power consumption.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to independently adjust the image plane position caused by a processing error or an assembly error in the main scanning direction and the sub-scanning direction. The present invention is also directed to a method of reducing image plane fluctuations caused by temperature changes by using a resin optical element which is easy to process and assemble without using a mechanical structure, and by reducing the degree of freedom in design in the main scanning direction and the sub-scanning direction. It is an object to effectively reduce light in the scanning direction.

[0006]

According to the present invention, there is provided a method for adjusting an image in an optical scanning apparatus, wherein a beam having a predetermined beam form from a light source side is converted into a line image long in a main scanning direction by a line image forming optical system. An image is formed, deflected by an optical deflector having a deflecting / reflecting surface near the image forming position of the line image, and the deflected beam is condensed toward the surface to be scanned by the scanning image forming optical system. And a method of adjusting the image formation of a deflecting beam in an optical scanning device that performs optical scanning of a surface to be scanned by forming a laser beam, which is characterized by the following points (claim 1). That is, the line image forming optical system is composed of two or more optical elements, and these optical elements include two or more surfaces having negative power in the sub-scanning direction and a surface having negative power in the main scanning direction. Include. An optical element having a surface having negative power in the main scanning direction, another optical element having a surface having negative power in the sub-scanning direction, a light source side optical system (light source / coupling optical system), and / or scanning By adjusting the relative positional relationship with the imaging optical system independently for the optical element and the other optical elements, the beam waist position in the main scanning direction and the sub-scanning direction of the deflecting beam with respect to the position of the surface to be scanned. Adjust. As described above, the "optical element" for adjusting the relative positional relationship with the light source side optical system and / or the scanning image forming optical system has a "surface having negative power in the main scanning direction". On the other hand, by adjusting the above “relative positional relationship”, the image plane position in the main scanning direction can be adjusted with respect to the surface to be scanned. Also, since the “other optical element” includes a “surface having negative power in the sub-scanning direction”, by adjusting the “relative positional relationship” to the “other optical element”, The image plane position in the sub-scanning direction can be adjusted with respect to the surface to be scanned. Since this imaging adjustment method adjusts a positional shift of an image plane due to a processing error or an assembling error, the line image imaging optical system or the scanning image forming optical system includes “including a resin optical element. It can be implemented "with or without." In the case of displacing the “component optical element” of the line image forming optical system in the “relative position adjustment” of the above optical element and other optical elements, it is not necessary to use a mechanical displacement mechanism for the displacement. Instead, it can be displaced using an appropriate jig, and after adjustment, can be fixed with an adhesive or the like.

The "line image forming optical system" of the present invention is "a beam from a light source is converted into a beam having a predetermined beam form by a coupling optical system, and this beam is converted into a long line in the main scanning direction by the line image forming optical system. The image is formed as an image, deflected by an optical deflector having a deflecting / reflecting surface near the image forming position of the line image, and the deflected beam is condensed toward the surface to be scanned by the scanning image forming optical system.
A linear image forming optical system in an optical scanning device that forms a light spot on a scanned surface and performs optical scanning on the scanned surface ”. The "line image forming optical system" according to the second aspect has the following features. That is, the line image forming optical system has one or more resin lenses and one or more glass lenses. The one or more resin lenses include “at least two surfaces having negative power in the sub-scanning direction and at least one surface having negative power in the main scanning direction”. The power of each surface of the one or more resin lenses is set so as to “effectively reduce the image plane fluctuation of the coupling optical system and / or the scanning imaging optical system due to a temperature change”. The line image forming optical system according to the third aspect has the following features. That is, the line image forming optical system has one or more resin image forming mirrors and one or more glass lenses. The one or more resin imaging mirrors include "at least one surface having a negative power in the main scanning direction and a stronger negative power in the sub-scanning direction". The power of each surface of the one or more resin imaging mirrors is set so as to “effectively reduce the image plane fluctuation of the coupling optical system and / or the scanning imaging optical system due to a temperature change”.
The line image forming optical system according to the fourth aspect has the following features. That is, the line image forming optical system has one or more resin image forming mirrors, one or more resin lenses, and one or more glass lenses. The one or more resin imaging mirrors are “surfaces having at least negative power in the sub-scanning direction”
The one or more resin lenses have at least one surface having “at least a surface having negative power in the sub-scanning direction”, and the system formed by the resin imaging mirror and the resin lens is “ At least one surface having a negative power in the main scanning direction ”. The power of each surface of the at least one surface of the resin imaging mirror and at least one surface of the resin lens can be used to effectively reduce the image plane fluctuation of the coupling optical system and / or the scanning imaging optical system due to temperature change. "Reduce".

That is, the line image forming optical system according to the second, third or fourth aspect effectively reduces the image plane fluctuation of the coupling optical system and / or the scanning image forming optical system due to a temperature change. "The image plane variation caused by the temperature change of the coupling optical system" is described in the above-mentioned "The metal holder holding the coupling optical system expands or contracts with the temperature change, and the coupling optical system and the light source The image produced by the fact that the coupling action changes due to a small change in the distance of the optical fiber or that the optical characteristics change due to temperature changes in the resin optical element when the coupling optical system includes a resin optical element This is a surface variation, and the image surface variation may occur even if the scanning image forming optical system does not include an optical element made of a resin material. “Image plane variation due to temperature change” of the scanning image forming optical system means that when a resin optical element is included in the scanning image forming optical system, the optical characteristics of the resin optical element change due to temperature change. This is the image plane fluctuation caused by this. In the case where the scanning image forming optical system includes a resin optical element, the line image forming optical system according to claim 3 has two resin lenses and one glass lens. And 2
The power of each surface of the two resin lenses, including “three surfaces having negative power in the sub-scanning direction and one surface having negative power in the main scanning direction” in the two resin lenses It is possible to effectively reduce the image plane fluctuation caused by the temperature change of the resin optical element included in the scanning image forming optical system (claim 5). Claim 2 or 3 or 4 or 5 above
In the line image forming optical system described above, a sub-surface of the “surface having negative power in the sub-scanning direction” included in the resin optical element (resin forming mirror, resin lens) in the line image forming optical system. The power in the scanning direction can be "set substantially equal to each other" (claim 6). As described above, the line image forming optical system according to any one of claims 2 to 6 describes that the image plane fluctuation caused by a temperature change is “an image plane fluctuation caused by a characteristic change due to a temperature change of a resin optical element”. By "cancelling", it is possible to effectively reduce the light in both the main scanning direction and the sub-scanning direction.

As described above, in order to correct the image plane fluctuation in the sub-scanning direction, a large negative power is required in the sub-scanning direction. When “two or more surfaces having negative power in the sub-scanning direction” are included in the resin lens, the negative power in the sub-scanning direction for correcting the image plane fluctuation is distributed to two or more lens surfaces. Therefore, the negative power of each surface can be reduced, and the tendency to reduce the radius of curvature of these surfaces in the sub-scanning direction can be effectively reduced.
The manufacture and assembly of the resin lens becomes easy. Further, when a resin image forming mirror is used as in the line image forming optical system according to the third and fourth aspects, the negative power of the resin image forming mirror is smaller than that in the case of “due to refraction on the lens surface”. Since it is "achievable with a smaller curvature", the radius of curvature of the resin imaging mirror may be large. Therefore, as in the case of claim 3, the image surface fluctuation correction can be performed by only one resin imaging mirror. Can be realized, and the production and assembly of the resin imaging mirror are easy. The optical scanning apparatus according to the present invention is configured such that "a beam having a predetermined beam form from the light source side is formed as a long line image in the main scanning direction by a line image forming optical system, and a deflecting reflection surface is formed near the line image forming position. An optical deflector that deflects the light, condenses the deflected beam toward the surface to be scanned by the scanning imaging optical system, forms a light spot on the surface to be scanned, and optically scans the surface to be scanned. " It is. An optical scanning device according to a seventh aspect is characterized in that, after performing the image adjustment by the “image forming adjustment method according to the first aspect”, each optical element of the line image forming optical system is fixed. An optical scanning device according to an eighth aspect is characterized in that the "line image forming optical system according to any one of the second to sixth aspects" is used as the line image forming optical system. In this case, when the scanning image forming optical system of the optical scanning device includes a resin optical element, the “line image forming optical system according to claim 5” can be used as the line image forming optical system. Item 9), an “fθ lens” can be used as the scanning image forming optical system (claim 10). In the above description, various gas lasers, solid-state lasers, semiconductor lasers, and LEDs can be used as the light source. In addition, the optical scanning device may be of a so-called single beam type or a multi-beam type. In this case, a beam combining type in which a beam from a semiconductor laser array or a plurality of light sources is combined by a prism as a light source. A light source device can be used. As the "optical deflector having a deflecting / reflecting surface", a rotating single-sided mirror, a rotating two-sided mirror, a rotating polygonal mirror, or a galvanometer mirror can be used.

An image forming apparatus according to the present invention is configured such that “an optical scanning is performed by an optical scanning device on a photosensitive surface of a photosensitive medium to form a latent image,
An image forming apparatus that visualizes a latent image to obtain an image,
As an optical scanning device for optically scanning a photosensitive surface of a photosensitive medium, the optical scanning device according to any one of claims 7 to 10 is used. 12. The image forming apparatus according to claim 11, wherein the photosensitive medium is a "photoconductive photoconductor", and an electrostatic latent image formed by uniform charging of the photosensitive surface and optical scanning of the optical scanning device is a "toner image". It can be configured to be visualized (claim 12). The toner image is fixed on a sheet-shaped recording medium (transfer paper or “OHP sheet (plastic sheet for overhead projector)”).
In the image forming apparatus according to claim 10 or 11, for example, a "silver salt photographic film" can be used as the photosensitive medium. In this case, the latent image formed by the optical scanning by the optical scanning device can be visualized by the “development method of a normal silver halide photographic process”. Such an image forming apparatus can be implemented as, for example, an "optical plate making apparatus" or an "optical drawing apparatus". The image forming apparatus according to claim 12 can be specifically implemented as a laser printer, a laser plotter, a digital copying machine, a facsimile machine, or the like.

[0011]

FIG. 1 is a view for explaining an embodiment of the invention of an optical scanning device. (A) shows a state viewed from the sub-scanning direction, and (b) is a diagram in which the optical path from the light source to the surface to be scanned is linearly developed and the vertical direction is the sub-scanning direction. The light source denoted by reference numeral 1 is a “semiconductor laser”. The divergent beam emitted from the light source 1 is converted into a predetermined beam form suitable for the subsequent optical system by a coupling lens 2 as a “coupling optical system”. The beam form of the coupled beam can be a "divergent beam" or a "convergent beam", but in this embodiment it is a "parallel beam". The coupled beam is a "line image forming optical system"
Are sequentially transmitted through the two lenses 3 and 4 and condensed in the sub-scanning direction by the action of the line image forming optical system, and are located near the deflecting and reflecting surface of the rotary polygon mirror 5 as an “optical deflector”. An image is formed as a "long line image in the main scanning direction". The beam reflected by the deflecting reflection surface is transmitted through an fθ lens 60 (which is constituted by two lenses 6a and 6b in this embodiment) constituting a scanning image forming optical system, and is operated by the fθ lens 60. The light is condensed toward the scanned surface 7 and forms a light spot on the scanned surface 7. When the rotary polygon mirror 5 rotates at a constant speed, the reflected beam is deflected at a constant angular velocity, and the light spot optically scans the surface 7 to be scanned. At this time, the light scanning by the light spot is made uniform in speed according to the fθ characteristic of the fθ lens 60. fθ
Both lenses 6a and 6b constituting the lens 60 are resin lenses. Therefore, when there is a temperature change in the optical scanning device, the refractive index and the shape of the material of the lenses 6a and 6b change. This change causes an image plane fluctuation (image plane fluctuation due to a temperature change). Image plane fluctuation caused by this temperature change
The correction is performed by the line image forming optical system. Of the two lenses 3 and 4 constituting the “line image forming optical system”, the lens 3 is a “resin lens” and the lens 4 is a “glass lens”.

The “incident surface 3a of the resin lens 3”, on which the parallel beam from the coupling lens 2 first enters, has “negative power” in both the main scanning direction and the sub-scanning direction.
This negative power differs between the main scanning direction and the sub scanning direction,
The negative power in the sub-scanning direction is larger. The exit surface 3b of the lens 3 is a "cylindrical surface having negative power only in the sub-scanning direction". The beam emitted from the resin lens 3 enters the glass lens 4. The glass lens 4 is a “toroidal lens”, and converts an incident beam into a substantially parallel beam in the main scanning direction and condenses it in the sub-scanning direction. The beam emitted from the glass lens 4 is incident on the deflecting and reflecting surface of the rotary polygon mirror 5 while being focused in the sub-scanning direction.
An image is formed at the position of the deflecting reflection surface as a "long line image in the main scanning direction". The glass lens 4 changes the coupling state (coupled beam form) of the exit beam from the coupling lens 2 (for example, changes the coupled beam form to a slightly convergent beam). Thus, a "cylindrical lens" can be used instead of a toroidal lens. Among the “image plane fluctuations in the main scanning and sub-scanning directions” due to temperature changes of the resin lenses 6a and 6b in the fθ lens 60, the image plane fluctuations in the main scanning direction are caused by the “main scanning” of the incident surface 3a of the resin lens 3. And the image plane variation in the sub-scanning direction is corrected by the “negative power” of the entrance surface 3a and the exit surface 3b of the resin lens 3.
Correct with. The fθ lens 60 is an anamorphic imaging system having an imaging function of making the position of the deflecting reflection surface and the position of the surface to be scanned substantially geometrically optically conjugate in the sub-scanning direction. Since the power is stronger than the positive power in the main scanning direction, the image plane fluctuation in the main scanning and sub-scanning directions accompanying the temperature fluctuation becomes “larger” in the sub-scanning direction. For this reason, “larger negative power” is required for correcting the image plane fluctuation in the sub-scanning direction. However, since the resin lens 3 has negative power in the sub-scanning direction in both the entrance surface 3a and the exit surface 3b, The radii of curvature in the sub-scanning direction of the entrance surface 3a and the exit surface 3b may be larger than those in the case of "correction on a single surface", so that the resin lens 3 can be easily manufactured and assembled. Further, by making the negative powers of the entrance surface 3a and the exit surface 3b substantially equal, the effect of distributing the negative power to the two surfaces (the radius of curvature of one surface does not become extremely small) increases.

FIG. 2 shows another embodiment of the optical scanning device, and FIG.
It is drawn according to. The same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In this embodiment, the “line image forming optical system” has three lenses 1.
0, 11, and 12. Of these three lenses, lenses 10 and 11 are resin lenses, and lens 12 is a glass lens. The incident surface 10a of the resin lens 10 has negative power in the main scanning and sub scanning directions, but the negative power in the sub scanning direction is stronger than the negative power in the main scanning direction. The exit surface of the resin lens 10 has negative power only in the sub-scanning direction. The entrance surface 11a of the resin lens 11 has negative power only in the sub-scanning direction,
1b is a plane. The glass lens 12 is
a is a "cylindrical surface having a positive power only in the sub-scanning direction", and the emission surface 12b is a "spherical surface having a positive power". Therefore, the resin lens 6 in the fθ lens 60
Among the “image plane fluctuations in the main scanning and sub-scanning directions” due to the temperature changes of a and 6b, the image plane fluctuations in the main scanning direction are corrected by the “power in the main scanning direction” of the incident surface 10a of the resin lens 10. The image plane variation in the sub-scanning direction is caused by the incident surface 10a, the exit surface 10b of the resin lens 10, and the incident surface 1 of the resin lens 11.
Correction is made by “power in each sub-scanning direction” 1a. Since the negative power required for the correction is divided and distributed to the three surfaces 10a, 10b, and 11a, the power is further divided than in the embodiment of FIG.
The radius of curvature of each surface can be reduced.
It is possible to easily manufacture and assemble 0,11. Of course, by making these three negative powers substantially equal to each other, the effect of distributing the negative power to the three surfaces increases. In the embodiment shown in FIG. 2, it is of course possible to distribute the negative power in the sub-scanning direction also to the exit surface of the resin lens 11 and to distribute the negative power in the sub-scanning direction necessary for correction to the four surfaces. is there.

FIG. 3 shows another embodiment of the optical scanning device according to FIG. The same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In this embodiment, the “line image forming optical system” includes a resin image forming mirror 20 on one surface and a glass lens 21.
The resin imaging mirror 20 has an anamorphic convex shape, has negative power in the main scanning direction, and has "stronger negative power" in the sub-scanning direction. Therefore, the parallel beam from the coupling lens 2 side is reflected by the resin imaging mirror 20.
When it is reflected to the divergent beam, the divergence in the sub-scanning direction is larger than the "divergence in the main scanning direction". The glass lens 21 is a toroidal lens having a positive power in both the main scanning direction and the sub-scanning direction, has a stronger power in the sub-scanning direction, and transmits a transmitted beam “a parallel beam in the main scanning direction and a converging beam in the sub-scanning direction”. Convert to The “main scan / scan” caused by the temperature change of the resin lenses 6a and 6b in the fθ lens 60
Of the "image plane fluctuation in the sub-scanning direction", the image plane fluctuation in the main scanning direction is corrected by the power in the main scanning direction of the resin imaging mirror 20, and the image plane fluctuation in the sub-scanning direction is corrected by the resin imaging mirror. Correction is made with power in the sub-scanning direction of 20. Since the radius of curvature of the reflection surface of the reflection imaging system can be made approximately four times as large as the "radius of curvature of the refraction surface when the same power is realized by the refraction surface", as in this embodiment, the resin imaging mirror is used. Even when “correction of image plane variation” is performed only on one reflecting surface of the reflecting mirror 20, the radius of curvature of the reflecting surface does not become so small.
Zero machining accuracy and assembly accuracy can be reduced. FIG. 4 shows still another embodiment of the optical scanning device according to FIG. The same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In this embodiment, the "line image forming optical system" includes a resin image forming mirror 30, a resin lens 31, and a glass lens 32.
The resin imaging mirror 30 has “negative power in both the main scanning and sub-scanning directions”, and the resin lens 31 has “negative power only in the sub-scanning direction on both the entrance surface and the exit surface”. Since the line image forming optical system forms the beam from the light source side as a long line image in the main scanning direction, the glass lens 32 naturally has “positive power in the sub scanning direction”. Glass lens 3
2 has "positive power weaker than the sub-scanning direction" in the main scanning direction. Resin lens 6 in fθ lens 60
Among the “image plane fluctuations in the main scanning and sub-scanning directions” caused by the temperature changes of “a” and “6b”, the image plane fluctuations in the main scanning direction are “power of the resin imaging mirror 30 in the main scanning direction”, and The image plane variation in the direction is described as “the resin imaging mirror 30 and the resin lens 31
In the sub-scanning direction of the entrance / exit surface of the laser beam. " As described above, the negative power required for correcting the image plane variation in the sub-scanning direction is divided and distributed to the reflecting surface of the resin imaging mirror 30 and the lens surface of the resin lens 31 so that each surface is divided. It can be easily understood that the radius of curvature of the optical element can be effectively increased, and the manufacture and assembly of these optical elements become easy. The “negative power in the main scanning direction” necessary for correcting the image plane fluctuation in the main scanning direction may be given to only the reflecting surface of the resin imaging mirror 30 or may be applied to the resin other than the reflecting surface. The negative power in the main scanning direction applied to the lens surface of the resin lens 31 may be distributed to the lens surface of the lens 31 made of resin, or the resin imaging mirror 30 may not be given power in the main scanning direction. The correction can be performed only by using the correction.

[0015]

EXAMPLE Here, a specific example will be described. This example is a specific example of the embodiment shown in FIG.
The beam from the light source is converted into a “parallel beam” by the coupling lens. Coupling lens focal length: 2
It is 7 mm, and the material of the lens barrel holding it is aluminum (linear expansion coefficient: 2.31 × 10 ⁻⁵ ). Therefore,
When the temperature changes from 25 ° C. to 10 ° C., the distance between the object point and the coupling lens is reduced by 0.00936 mm, and the coupled light flux tends to diverge. If the temperature is 2
When the temperature changes from 5 ° C. to 45 ° C., the distance between the object point and the coupling lens increases by 0.01247 mm, and the coupled light flux tends to be focused. The light source 1 is a semiconductor laser having an emission wavelength of 780 nm. fθ lens 60 has a combined focal length in the main scanning direction: 225.3 mm, a combined focal length in the sub-scanning direction: 78 mm, a writing width (effective optical scanning width): ± 161.5 mm, and an angle of view: ± 40.6. Degrees. Shown in FIG. 2 (b), plane spacing: d ₁ to d ₆ are as follows.

D ₁ = 3 mm, d ₂ = 5 mm, d ₃ = 3 m
m, d ₄ = 5 mm, d ₅ = 6 mm, d ₆ = 129.8 mm The radii of curvature of the entrance and exit surfaces of the resin lenses 10, 11 and the glass lens 12 are as follows. Radius of curvature of 10a Main-119.52mm Secondary-16.7mm Radius of curvature of 10b Primary 副 Secondary 16.7mm Radius of curvature of 11a Primary 副 Secondary-16.7mm Radius of curvature of 11b Primary 副 Secondary 半径 Radius of curvature of 12a Primary 副 Secondary 13.54 mm, radius of curvature of 12b -179.978 mm (spherical surface) The refractive indexes of the resin lenses 10 and 11 are both 1.52397.
8 (λ = 780 nm, 25 ° C.), and the glass lens 12 has a refractive index of 1.733278 (λ = 780 nm, 2
5 degrees C). The lens surfaces 10a, 10b, 11a
Since the curvature radius is the same in the sub-scanning direction, the negative powers of these surfaces in the sub-scanning direction are the same.

In this embodiment, the above 25 ° C. is designed as a “reference temperature”. Reference temperature: 25 degrees C
At the center of FIG. 5A. The broken line indicates the main scanning direction, and the solid line indicates the sub-scanning direction. The line image forming optical system has "no function to correct image plane fluctuation caused by temperature change"
In other words, when the optical characteristics of the line image forming optical system are not affected by the temperature change, and when the environmental temperature (the temperature in the optical scanning device) rises to 45 ° C., in the main scanning and sub-scanning directions, Each field curvature fluctuates as shown in the right diagram of FIG. 5A, and when the ambient temperature drops to 10 ° C., each field curvature in the main scanning and sub-scanning directions becomes as shown in FIG. It fluctuates as shown on the left. In the case of the line image forming optical system of the embodiment, since the lenses 10 and 11 are made of resin and the optical characteristics change with the temperature change, when the environmental temperature rises to 45 ° C., each of the main scanning and sub-scanning directions is performed. The curvature of field is corrected as shown in the right diagram of FIG. 5B, and when the ambient temperature drops to 10 ° C., the curvature of field in the main scanning and sub-scanning directions is changed to the left in FIG. The correction is made as shown. From this result, it will be understood that the effect of correcting the image plane variation of the resin lenses 10 and 11 in the line image forming optical system in the above embodiment is extremely good. By the way, when the spot diameter of the light spot formed on the surface to be scanned is reduced, if the wavefront aberration is not good, the light intensity distribution of the light spot does not have a simple mountain shape, and a good spot shape cannot be realized. In the above embodiment, the “wavefront aberration in the sub-scanning direction” at an image height of the light spot of 0 mm is:
This is as shown in FIG. Although this wavefront aberration is not bad at all, the maximum value (peak value “PV”) is 1λ.
Therefore, when the spot diameter in the sub-scanning direction becomes extremely small, it becomes difficult to narrow down the spot diameter in the sub-scanning direction. In such a case, it is possible to correct the wavefront aberration including the “surface that is non-circular in the sub-scanning direction” in the line image forming optical system. For example, when the shape of the incident surface 10a of the lens 10 in the embodiment in the sub-scanning direction is made non-circular and the non-arc shape is optimized according to the wavefront aberration correction, the wavefront aberration becomes as shown in FIG. Become. In this wavefront aberration, the maximum value is 0.11λ, and FIG.
Is corrected to about 1/16. With such good wavefront aberration, a good light spot can be realized by narrowing the spot diameter in the sub-scanning direction to a very small value.

FIG. 7 shows the "relationship between defocus (displacement between beam waist and scanned surface) and spot diameter" in the above embodiment. (A) relates to the main scanning direction, and (b) relates to the sub-scanning direction. In this embodiment, assuming that the spot diameter of the light spot for optical scanning is “40 μm” in both the main scanning direction and the sub-scanning direction, the spot diameter variation width is 40 ± 4.
In the state of defocus: 0, the spot diameter is 37 μm in both the main scanning and sub-scanning directions so as to be within μm.
It is designed to be. Then, the depth: W (the defocus range where the spot diameter fluctuation width falls within 40 ± 4 μm) is
It is about 2.7 mm (± 1.35 mm) in the main scanning direction and about 3 mm (± 1.5 mm) in the sub-scanning direction. Therefore, the shift amount of the image plane due to the temperature change is ±
It must be kept within 1.35 mm and within ± 1.5 mm in the sub-scanning direction. Since the temperature guaranteed area of the optical scanning device is about 10 ° C. to 45 ° C., if the reference temperature (room temperature) is 25 ° C., the “remaining” of the image plane position after being corrected by the line image forming optical system. Fluctuation amount "to" 0.06 mm / degree C "
Therefore, the linear image forming optical system may be designed to satisfy such a condition. FIG.
In the embodiments shown in FIGS. 4 to 4, the beam from the light source is one beam. However, a multi-beam scanning method using a light source such as a semiconductor laser array having a plurality of light emitting points or combining a plurality of light sources such as LDs is used. As the optical scanning device, the optical scanning device of the present invention can be implemented. As described above, `` the image plane in the main scanning direction and the sub-scanning direction is a series of beam waist positions in the main scanning direction and the sub-scanning direction, ''
The image plane fluctuation amount can be actually measured as “fluctuation in beam waist position at each image height”. The fluctuation of the beam waist position is substantially equivalent to the fluctuation of the curvature of field.

The above description is based on the premise that each of the optical elements arranged on the optical path from the light source to the surface to be scanned is processed as designed and arranged at an appropriate position. When the optical scanning device is actually implemented, processing errors and assembly errors are inevitably generated in each optical element. These errors occur according to the probability and differ depending on the individual optical element. The scanning image forming optical system is most likely to cause processing errors and the like, and has the greatest influence. If there is a processing error or an assembly error in the optical element constituting the scanning imaging optical system, the beam waist position of the deflection beam will be shifted with respect to the surface to be scanned.
The effective light scanning area appears as an image plane shift in the main scanning direction and the sub-scanning direction. The imaging adjustment of the present invention is a method of adjusting the beam waist position in the main scanning and sub-scanning directions with respect to the surface to be scanned in the above-described case. For example, when the optical system configuration of the optical scanning device is as shown in FIG. 4 described above, the beam waist position in the main scanning and sub-scanning directions is shifted with respect to the scanned surface 7 due to a processing error of the fθ lens 60 or the like. In the case of deviation, the imaging adjustment can be performed as follows.
That is, as shown in FIG. 8, the resin lens 31 and the glass lens 32 among the resin imaging mirror 30, the resin lens 31, and the glass lens 32 constituting the line image forming optical system.
Are displaceable in the optical axis direction. Since the glass lens 32 also has power in the main scanning direction, by moving the glass lens 32 in the optical axis direction, the “beam waist position in the main scanning direction” generated due to a processing error or the like of the fθ lens 60 or the like. Is corrected, and the beam waist position can be adjusted so as to substantially coincide with the scanned surface 7. After such adjustment, the glass lens 32 is fixed. Since the resin lens 31 has power only in the sub-scanning direction, by moving the resin lens 31 in the optical axis direction, it is possible to shift the beam waist position in the main scanning direction (adjusted earlier) without changing fθ The "deviation of the beam waist position in the sub-scanning direction" caused by a processing error or the like of the lens 60 or the like can be corrected, and the beam waist position can be adjusted so as to substantially coincide with the scanned surface 7, and after such adjustment, The resin lens 31 is fixed. By performing the image formation adjustment in this way, it is possible to achieve a good match between the image plane and the scanned surface 7 in both the main scanning direction and the sub-scanning direction.

The above-mentioned resin lens 31 and glass lens 3
In the “fixing after adjustment” of item 2, at least one of these lenses is “adhered to the air to be fixed with an ultraviolet curable resin or the like” so that it is conventionally necessary to rotate the lens holder around the optical axis. The need for a V-groove is eliminated. In addition, when the resin lens 31 is fixed by the air bonding, unnecessary deformation can be suppressed since there is no need to apply a load with a leaf spring or the like (claim 6). FIG. 9 is a diagram for explaining a case where the image forming adjustment method is performed in the case of the optical scanning device shown in FIG. Since the resin lens 10 has power in the main scanning direction, by moving the resin lens 10 in the optical axis direction, “the beam waist position in the main scanning direction is generated due to a processing error of the fθ lens 60 or the like. The beam waist position can be adjusted so as to substantially coincide with the surface 7 to be scanned. After such adjustment, the resin lens 10 is fixed. Since the resin lens 11 has power in the sub-scanning direction, by moving the resin lens 11 in the optical axis direction, “the beam waist position in the sub-scanning direction is generated due to a processing error of the fθ lens 60 or the like. The deviation can be corrected, and the beam waist position can be adjusted so as to substantially coincide with the scanned surface 7. After such adjustment, the resin lens 11 can be fixed. When the resin lens 10 having different negative powers in the main scanning direction and the sub-scanning direction is moved in the optical axis direction and the “beam waist position in the main scanning direction” is adjusted so as to substantially coincide with the surface 7 to be scanned. This causes the beam waist position in the sub-scanning direction to shift, but the resin lens 11
Since has power only in the sub-scanning direction, the “beam waist position in the sub-scanning direction” can be adjusted so as to substantially coincide with the surface 7 to be scanned. By the way, since the resin lenses 10 and 11 are anamorphic, if these lenses have a rotational position error around the optical axis or a deviation of the optical axis in the sub-scanning direction, the wavefront aberration will be deteriorated. It is difficult to form a small diameter light spot satisfactorily. For example, in the case of the above-described embodiment, the wavefront aberration of the resin lens 10 when “the shape of the incident side lens surface 10a surface in the sub-scanning direction is optimized to be a non-circular shape” is as described above. As shown in FIG. 6B, in this case, when the resin lens 10 is shifted from the regular position by 0.1 mm in the sub-scanning direction, the wavefront aberration is reduced as shown in FIG.
As shown in the figure, the maximum value deteriorates to 0.44λ. Further, when the resin lens 10 is rotated by 0.05 degrees around the optical axis from the normal direction, the wavefront aberration becomes as shown in FIG.
It deteriorates to 0.53λ at the maximum value. Therefore, when fixing the resin lenses 10 and 11, it is preferable to adjust the rotational position around the optical axis and the position in the sub-scanning direction. In FIG.
After adjustment, the resin lens 10 and the resin lens 11 are fixed by “air bonding that is fixed with an ultraviolet curing resin or the like”.
The glass lens 12 is fixed in contact with the base 90.
The resin lens 10 and the resin lens 11 are chucked, and the above-mentioned adjustment is performed while floating in the air. For this reason, the resin lens 10 and the resin lens 11 are fixed to the base 90 via the adhesives 100 and 101, respectively. In the case of the imaging adjustment method described with reference to FIGS. 8 and 9, in order to adjust the beam waist position, “the resin imaging mirror 20 or 30 and the light source side optical system (the light source 1 and the coupling lens) are used. Adjustment of "relative positional relationship with 2)" can also be used.

The line image forming optical system of the optical scanning device described above with reference to FIGS. 1 and 2 has a beam form from a light source 1 by a coupling optical system 2 in a predetermined beam form. (Parallel beam), and this beam is formed as a long line image in the main scanning direction by the line image forming optical systems 3 and 4 (10, 11, 12), and is deflected and reflected in the vicinity of the line image forming position. The light is deflected by the optical deflector 5 having a surface, and the deflected beam is condensed toward the surface 7 to be scanned by the scanning image forming optical system 60 to form a light spot on the surface 7 to be scanned and the light on the surface 7 to be scanned. A line image forming optical system in an optical scanning device for performing scanning, comprising one or more resin lenses 3 (10, 11) and one or more glass lenses 4 (12). The resin lens 4 (10, 11) has a surface 3a having negative power in the sub-scanning direction, b (10a, 10b, 11a) of at least two surfaces, the surface 3a having a negative power in the main scanning direction
(10a) at least one surface, and the scanning image forming optical system 60
A linear image forming optical system (Claim 2) in which the power of each surface of the one or more resin lenses is set so as to effectively reduce the image plane fluctuation caused by the temperature change. FIG.
The optical image forming optical system included in the optical scanning device according to the embodiment described above is configured such that a beam from a light source 1 is converted into a beam having a predetermined beam form by a coupling optical system 2, and this beam is formed into a linear image. The optical systems 20 and 21 form an image as a long line image in the main scanning direction, and the image is deflected by an optical deflector 5 having a deflecting / reflecting surface near the image forming position of the line image. The light is condensed toward the scanning surface 7 and is scanned
A line image forming optical system in an optical scanning device that forms a light spot on the surface to scan the surface to be scanned 7 and has a resin image forming mirror 20 and a glass lens 21. The imaging mirror 20 has a surface having negative power in the main scanning direction and strong negative power in the sub-scanning direction, and effectively reduces the image plane fluctuation of the scanning imaging optical system 60 due to a temperature change. Thus, a line image forming optical system in which the power of the surface of the resin image forming mirror is set (claim 3).

Further, in the line image forming optical system of the optical scanning device described in the embodiment with reference to FIG. 4, the beam from the light source 1 is converted into a beam having a predetermined beam form by the coupling optical system 2. This beam is formed into a line image forming optical system 30, 31,
32 forms a line image in the main scanning direction as a long line image, deflects it by an optical deflector 5 having a deflecting reflection surface in the vicinity of the image forming position of the line image, and deflects a beam onto the surface 7 to be scanned by a scanning image forming optical system 60. A line image forming optical system in an optical scanning device for forming a light spot on the surface to be scanned 7 and performing light scanning on the surface to be scanned 7, comprising one or more resin image forming mirrors 30
And one or more resin lenses 31 and one or more glass lenses 32. The resin imaging mirror 30 has a surface having negative power at least in the sub-scanning direction. The lens 31 has at least one surface having negative power at least in the sub-scanning direction. A system including the resin imaging mirror 30 and the resin lens 31 has a surface (resin having negative power in the main scanning direction). At least one surface of the imaging mirror, and at least one resin imaging mirror and at least one surface of the scanning imaging optical system 60 so as to effectively reduce image surface fluctuations caused by temperature changes. The power of each surface of the resin lens is set (claim 4). The line image forming optical system of the above-described embodiment includes two resin lenses 10 and 11.
And one glass lens 12, and the two resin lenses 10, 11 have three surfaces (10a, 10b, 11a) having negative power in the sub-scanning direction, and One surface (10a) having a negative power is included, and two resin-made surfaces are used so as to effectively reduce the image surface fluctuation caused by the temperature change of the resin optical element 6b included in the scanning imaging optical system 60. The power of each surface of the lenses 10 and 11 is set (claim 5), and the surfaces (10a, 10b,
11a) wherein the power in the sub-scanning direction is set to be substantially equal to each other (claim 6). The optical scanning device described in the embodiment with reference to FIGS. 1 to 4 above emits a beam having a predetermined beam form from the light source 1 side to the line image forming optical systems 3, 4 (10, 4).
11, 12 or 20, 21 or 30, 31, 3
According to 2), a linear image is formed as a long line image in the main scanning direction, and is deflected by an optical deflector 5 having a deflecting / reflecting surface near the image forming position of the line image. 7. A line image forming optical system according to claim 2, wherein the light scanning device performs light scanning on the surface to be scanned 7 by forming a light spot on the surface 7 to be scanned. A scanning image forming optical system 60 includes a resin optical element 6b, and is used as a line image forming optical system.
The line image forming optical system (described in the embodiment) can be used (claim 9). The scanning image forming optical system 60 is an fθ lens (claim 10). In each of the embodiments described above, the image plane fluctuation caused by the temperature change in the scanning image forming optical system 60 is corrected by the line image forming optical system. Obviously, the line image forming optical system can be configured so as to effectively reduce the image plane fluctuation of the system and the scanning image forming optical system due to the temperature change.

In the image forming adjustment method described in the embodiment with reference to FIGS. 8 and 9, the beam of a predetermined beam form from the light source 1 is applied to the line image forming optical systems 30, 31, 32 ( 10,
11, 12), an optical deflector 5 which forms a long line image in the main scanning direction and has a deflecting / reflecting surface near the image forming position of the line image
In the optical scanning apparatus, the deflected beam is condensed toward the surface to be scanned 7 by the scanning and imaging optical system 60, and a light spot is formed on the surface to be scanned 7 to perform optical scanning of the surface to be scanned 7. A method for adjusting the image formation of a deflected beam, wherein the line image forming optical system is provided with two or more optical elements 30, 31, 32 (1
0, 11, 12), these optical elements include two or more surfaces having negative power in the sub-scanning direction and a surface having negative power in the main scanning direction. The relative positional relationship between the optical element having the surface having the power of the sub-scanning direction and the other optical element having the surface having the negative power in the sub-scanning direction and the scanning image forming optical system is shown by the optical elements 31 (10) and An image forming adjustment method for adjusting the beam waist position of the deflection beam in the main scanning direction and the sub-scanning direction with respect to the position of the scanning surface by independently adjusting the other optical elements 32 (12). In each of the embodiments of the optical scanning device, if the image forming adjustment is performed by this image forming adjustment method, and each optical element of the line image forming optical system is fixed.
The described optical scanning device is implemented. Finally, an embodiment of the image forming apparatus will be described with reference to FIG. This image forming apparatus is a “laser printer”. The laser printer 100 has a “photoconductive photosensitive member formed in a cylindrical shape” as the photosensitive medium 111. Around the photosensitive medium 111, a charging roller 112 as a charging unit, a developing device 113, a transfer roller 114, and a cleaning device 115 are provided. A well-known "corona charger" can be used as the charging means. The laser beam L
B, an optical scanning device 117 is provided.
The “exposure by optical writing” is performed between the developing device 2 and the developing device 113. 11, reference numeral 116 denotes a fixing device, reference numeral 118 denotes a cassette, reference numeral 119 denotes a pair of registration rollers, reference numeral 120 denotes a paper feed roller, reference numeral 121 denotes a conveyance path, reference numeral 122 denotes a pair of discharge rollers, reference numeral 123 denotes a tray,
Reference symbol P indicates a transfer sheet as a recording medium. When performing image formation, the photosensitive medium 11 which is a photoconductive photoconductor is used.
1 is rotated clockwise at a constant speed, and the surface thereof is charged roller 1
The photosensitive drum 12 is uniformly charged by the laser scanning device 12 and receives an exposure by writing the laser beam LB of the optical scanning device 117 to form an electrostatic latent image. The formed electrostatic latent image is a so-called “negative latent image”, and the image portion is exposed. This electrostatic latent image is reversely developed by the developing device 113, and a toner image is formed on the image carrier 111. Cassette 118 containing transfer paper P
Is detachable from the main body of the image forming apparatus 100, and the uppermost sheet of the stored transfer paper P is fed by the feed roller 120 in a state where it is mounted as shown in the figure. The fed transfer paper P has its leading end held by a pair of registration rollers 119. The registration roller pair 119 sends the transfer paper P to the transfer portion in synchronization with the timing at which the toner image on the image carrier 111 moves to the transfer position. The transferred transfer paper P is superimposed on the toner image at the transfer section, and the toner image is electrostatically transferred by the operation of the transfer roller 114. The transfer paper P on which the toner image has been transferred is sent to a fixing device 116, where the toner image is fixed, and is discharged onto a tray 123 by a discharge roller pair 122 through a conveyance path 121. The surface of the image carrier 111 after the transfer of the toner image is
15 removes residual toner and paper dust. The above-described OHP sheet or the like can be used instead of the transfer paper, and the transfer of the toner image can be performed via an “intermediate transfer medium” such as an intermediate transfer belt. Good image formation can be performed by using the optical scanning device 117 of each of the above-described embodiments. Therefore, this image forming apparatus is an image forming apparatus that forms a latent image by performing optical scanning on the photosensitive surface of the photosensitive medium 111 by the optical scanning device 117 and visualizes the latent image to obtain an image. As the optical scanning device 117 for optically scanning the photosensitive surface, the optical scanning device 117 according to any one of claims 7 to 10 can be used (claim 11).
The photosensitive medium 111 is a photoconductive photosensitive member, and an electrostatic latent image formed by uniform charging of the photosensitive surface and optical scanning by the optical scanning device is visualized as a toner image.

[0024]

As described above, according to the present invention, a novel optical scanning device, a linear image forming optical system in the optical scanning device, an image forming adjustment method in the optical scanning device, and an image forming apparatus can be realized. . According to the linear image forming optical system of the present invention, the image plane fluctuation caused by the temperature change of the optical element made of the resin material included in the optical scanning device is reduced without using a mechanical configuration, and the degree of freedom in design is reduced. Without using a “resin optical element that is easy to process and assemble”, it can be effectively reduced in the main scanning direction and the sub-scanning direction. Therefore, the optical scanning device using such a line image forming optical system can effectively prevent or reduce the increase in the spot diameter regardless of the temperature change within a practical allowable range of the temperature change. Optical scanning can be realized.
Further, according to the imaging adjustment method of the present invention, the beam waist positions in the main scanning and sub-scanning directions of the deflecting beam caused by the processing error of the optical element such as the fθ lens and the like are independently set on the surface to be scanned. If the optical element of the line image forming optical system is fixed after performing such adjustment, the main scanning
Since the beam waist position in the sub-scanning direction matches well with the surface to be scanned, good optical scanning is possible. Further, the image forming apparatus of the present invention can always achieve good image formation irrespective of a temperature change by using the optical scanning device as described above.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining one embodiment of an optical scanning device of the present invention.

FIG. 2 is a diagram for explaining another embodiment of the optical scanning device of the present invention.

FIG. 3 is a diagram for explaining another embodiment of the optical scanning device of the present invention.

FIG. 4 is a diagram for explaining still another embodiment of the optical scanning device of the present invention.

FIG. 5 is a diagram for explaining an image plane fluctuation caused by a temperature change and its correction in the embodiment.

6A and 6B are diagrams illustrating a wavefront aberration (a) in the example and a wavefront aberration (b) when one of the lens surfaces in the sub-scanning direction is made non-circular in the example.

FIG. 7 is a diagram illustrating a relationship between defocus and a spot diameter according to the embodiment.

FIG. 8 is a diagram for explaining a case where the imaging adjustment method according to claim 1 is implemented in the embodiment of FIG. 3;

FIG. 9 is a diagram for explaining a case where the imaging adjustment method according to claim 1 is implemented in the embodiment of FIG. 2;

FIG. 10 illustrates a resin lens 10 according to the embodiment.
FIG. 7 is a diagram for explaining deterioration of wavefront aberration when there is an azimuth error around the optical axis and when the wavefront aberration is shifted in the sub-scanning direction.

FIG. 11 is a diagram for describing an embodiment of an image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source (semiconductor laser) 2 Coupling optical system (coupling lens) 3 Resin lens which comprises a line image forming optical system 4 Glass lens which comprises a line image forming optical system 5 Optical deflector (rotating polygon mirror) ) 60 Scanning optical system (fθ lens) 7 Scanned surface

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 17/08 B41J 3/00 D H04N 1/113 H04N 1/04 104A F-term (Reference) 2C362 AA48 BA86 BB14 BB22 DA03 2H045 AA01 CA04 CA34 CA55 CA63 CB22 2H087 KA19 LA22 LA25 LA28 NA08 PA04 PB04 QA02 QA14 QA22 QA26 QA33 QA42 QA45 RA07 TA03 TA06 UA01 5C072 AA03 BA04 DA03 DA04 DA23 HA02 HA09 HB10 RA12 9

Claims (12)

[Claims] 1. A beam having a predetermined beam form from a light source side is formed as a long line image in a main scanning direction by a line image forming optical system, and a light having a deflecting reflection surface in the vicinity of the image forming position of the line image. In an optical scanning device that deflects by a deflector, condenses a deflected beam toward a surface to be scanned by a scanning imaging optical system, forms an optical spot on the surface to be scanned, and optically scans the surface to be scanned, A method for adjusting the image formation of a deflected beam, comprising: forming a linear image forming optical system by two or more optical elements; and providing these optical elements with two or more surfaces having negative power in the sub-scanning direction. An optical element having a surface having a negative power in the main scanning direction, including a surface having a negative power in the main scanning direction, and another optical element having a surface having a negative power in the sub-scanning direction; The relative positional relationship with the optical system and / or the scanning imaging optical system, By independently adjusting the optical element and other optical elements, the beam waist position in the main scanning direction and the sub-scanning direction of the deflected beam is adjusted with respect to the position of the surface to be scanned. Imaging adjustment method. 2. A beam from a light source is formed into a beam having a predetermined beam form by a coupling optical system, and the beam is formed as a long line image in a main scanning direction by a line image forming optical system.
The light is deflected by an optical deflector having a deflecting / reflecting surface near the image forming position of the line image, and the deflecting beam is condensed toward a surface to be scanned by a scanning image forming optical system to form a light spot on the surface to be scanned. A line image forming optical system in an optical scanning device that performs optical scanning of a surface to be scanned, comprising: one or more resin lenses; and one or more glass lenses; The resin lens includes at least two surfaces having negative power in the sub-scanning direction and at least one surface having negative power in the main scanning direction, and includes a coupling optical system and / or a scanning imaging optical system.
To effectively reduce the image plane fluctuation due to temperature change,
A linear image forming optical system, wherein the power of each surface of the one or more resin lenses is set. 3. A beam from a light source is converted into a beam having a predetermined beam form by a coupling optical system, and the beam is formed as a long line image in the main scanning direction by a line image forming optical system.
The light is deflected by an optical deflector having a deflecting / reflecting surface near the image forming position of the line image, and the deflecting beam is condensed toward a surface to be scanned by a scanning image forming optical system to form a light spot on the surface to be scanned. A line image forming optical system in an optical scanning device for performing optical scanning of a surface to be scanned, comprising: one or more resin imaging mirrors; and one or more glass lenses; The above-described resin imaging mirror includes at least one surface having negative power in the main scanning direction and stronger negative power in the sub-scanning direction, and includes a coupling optical system and / or a scanning imaging optical system.
To effectively reduce the image plane fluctuation due to temperature change,
A line image forming optical system, wherein the power of each surface of the one or more resin image forming mirrors is set. 4. A beam from a light source is formed into a beam having a predetermined beam form by a coupling optical system, and the beam is formed as a long line image in the main scanning direction by a line image forming optical system.
The light is deflected by an optical deflector having a deflecting / reflecting surface near the image forming position of the line image, and the deflecting beam is condensed toward a surface to be scanned by a scanning image forming optical system to form a light spot on the surface to be scanned. A line image forming optical system in an optical scanning device for optically scanning a surface to be scanned, comprising: one or more resin imaging mirrors; one or more resin lenses; and one or more glass lenses Wherein the one or more resin imaging mirrors have at least one surface having negative power in at least the sub-scanning direction, and the one or more resin lenses have at least one surface in the sub-scanning direction. The resin imaging mirror and the resin lens include at least one surface having a negative power in the main scanning direction. The coupling optical system and / or Alternatively, there is an image plane fluctuation due to temperature change of the scanning imaging optical system. To mitigate, the linear image forming optical system, characterized in that the one or more sides of the resin imaging mirrors and surfaces of the power of one or more plastic lenses are set. 5. The line image forming optical system according to claim 2, further comprising two resin lenses and one glass lens, wherein the two resin lenses are arranged in the sub-scanning direction. Includes three surfaces with negative power and one surface with negative power in the main scanning direction, effectively reducing image plane fluctuations caused by temperature changes in resin optical elements included in the scanning imaging optical system A line image forming optical system, wherein the power of each surface of the two resin lenses is set such that the power is set. 6. A line image forming optical system according to claim 2, wherein the surface having a negative power in the sub-scanning direction included in the resin optical element in the line image forming optical system. And a power in the sub-scanning direction is set substantially equal to each other. 7. A beam having a predetermined beam form from a light source side is formed as a long line image in a main scanning direction by a line image forming optical system, and a light having a deflecting reflection surface near an image forming position of the line image. In an optical scanning device that deflects by a deflector, condenses a deflected beam toward a surface to be scanned by a scanning imaging optical system, forms an optical spot on the surface to be scanned, and optically scans the surface to be scanned, An optical scanning device, wherein each optical element of a line image forming optical system is fixed by performing image forming adjustment by the image forming adjusting method according to claim 1. 8. A beam having a predetermined beam form from a light source side is formed as a long line image in the main scanning direction by a line image forming optical system, and a light having a deflecting reflection surface near an image forming position of the line image. In an optical scanning device that deflects by a deflector, condenses a deflected beam toward a surface to be scanned by a scanning imaging optical system, forms an optical spot on the surface to be scanned, and optically scans the surface to be scanned, An optical scanning device using the line image forming optical system according to any one of claims 2 to 6. 9. An optical scanning device according to claim 8, wherein the scanning image forming optical system includes a resin optical element, and wherein the line image forming optical system according to claim 5 is used. . 10. The optical scanning device according to claim 9, wherein the scanning image forming optical system is an fθ lens. 11. An image forming apparatus for forming a latent image by performing optical scanning on a photosensitive surface of a photosensitive medium by an optical scanning device and visualizing the latent image to obtain an image, wherein the light on the photosensitive surface of the photosensitive medium is provided. An image forming apparatus comprising: an optical scanning device that performs scanning, wherein the optical scanning device according to any one of claims 7 to 10 is used. 12. The image forming apparatus according to claim 11, wherein the photosensitive medium is a photoconductive photoreceptor, and an electrostatic latent image formed by uniform charging of a photosensitive surface and optical scanning by an optical scanning device is:
An image forming apparatus which is visualized as a toner image.