JPH03130716A - Scanning optical device - Google Patents

Abstract

PURPOSE:To correct the curvature of an image with high accuracy by detecting the vibration position of a first image forming optical system with a detecting means consisting of a detecting light source and a light receiving part, and controlling the vibration based on a detecting signal. CONSTITUTION:The cylindrical lens 22 of a first image forming optical system is provided so as to be movable or vibratable along an optical axis R, and executes the correction of the curvature of image. A detecting means for detecting the movement is constituted of the detecting light source 20 and the light receiving part 21, and a luminous flux from the light source 20 is limited and received by a control member 23. By the receiving light quantity of the light receiving part 21, the moving amount of the cylindrical lens 22 is known, and the detecting signal is brought to feedback to an actuator for moving or vibrating the lens 22. In such a manner, an exact control corresponding to a deflection scan can be executed, and the curvature of the image can be corrected with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanning optical device used in digital copying machines, laser printers, laser plotters, laser facsimile machines, laser engraving machines, etc.

The present invention relates to a scanning optical device that has a surface tilt correction function and can reduce field curvature.

[Conventional technology]

A scanning optical device that scans a scanned medium by deflecting light from a light source using various deflectors has been well known, and is used in digital copying machines, laser printers, laser plotters, laser facsimile machines, laser engraving machines, etc. It is used as a scanning optical system.

By the way, in the above-mentioned scanning optical device, it is well known that when a reflective surface is used to deflect the light beam, the pitch of the main scanning lines becomes uneven due to the surface inclination of the reflective surface during deflection. It is necessary to make corrections for this.

In addition, if the deflection angle during deflection scanning is large, curvature of field will occur due to the imaging lens system.In order to obtain a high-density spot diameter, the curvature of field due to the imaging lens system must be Both directions must be corrected.

On the other hand, as scanning optical devices, scanning optical systems that use a rotating polygon mirror as an optical deflector have become mainstream in order to increase scanning speed. The surface of the deflection-reflecting surface is tilted, causing a phenomenon in which the scanning position of the scanned surface varies.

Therefore, in order to correct the surface tilt when a rotating polygon mirror is used as a deflector, a scanning optical device using a correction optical system such as an fθ lens system has been proposed (Japanese Patent Laid-Open No. 63-1066
18, JP-A-62-147421, etc.).

In addition, as a method for correcting field curvature in a scanning optical device, for example, in a post-objective type scanning optical device in which an imaging lens system (mainly using a spherical lens) is installed in front of a deflector, deflection scanning Along with this, a technology has been proposed to correct field curvature in the main and sub-scanning directions by moving the light source in the optical axis direction (Japanese Patent Application Laid-Open No. 1983-1999).
14820, etc.), and in both post- and pre-objective type scanning optical devices in which an imaging lens system (mainly using a spherical lens) is installed before and after a deflector, the collimating lens and the condensing lens are used for deflection scanning. A technique has been proposed that similarly corrects field curvature in the main and sub-scanning directions by moving in the optical axis direction in accordance with the
-57108, JP-A-58-57109, etc.).

[Problem to be solved by the invention]

By the way, if the imaging lens system of the scanning optical system that has the above-mentioned mechanism for correcting field curvature is a spherical lens, the spherical lens has an astigmatism difference. The field curvature is different. In addition, in the above-mentioned surface tilt correction optical system, since there are lenses in the optical path having different powers (lens refractive powers) in the main and sub-scanning directions, the body surface curvatures in the main and sub-scanning directions are different. Therefore, simply moving the spherical lens in the optical path or the light source cannot correct the field curvature in both the main and sub-scanning directions, and even if such a correction mechanism is applied to the above-mentioned surface tilt correction optical system, However, a problem arises in that the field curvature in the main and sub-side scans cannot be completely corrected.

In addition, regarding the control of the movement of the light source and lens when correcting field curvature using conventional technology, ``performing sine vibration'' is used.
Although such operations are described, the control device and control method are not specifically described.

However, in a scanning optical system using a rotating polygon mirror,
To correct field curvature, it takes several hundred to several thousand H.
It is necessary to control the vibration movement of z, and as a result, with normal open-loop control, there is a delay in control and the control is unable to follow the curvature of field, which makes it difficult to obtain a correction effect. The problem arises that there is no.

In addition, in general optical systems that do not have a mechanical correction mechanism for field curvature, field curvature is corrected only by using an fθ lens or the like in the optical system, and by using a lens configuration that combines multiple lenses. Therefore, field curvature in both the main and sub-scanning directions, fO characteristics (magnification error 1 uniform velocity scanning property), spherical aberration, sine conditions, etc. are required as design conditions for the optical system. There is a trade-off relationship between them, and it is difficult to make all design conditions favorable at the same time. Therefore, if the above-described curvature of field can be corrected, the degree of freedom in design for improving other conditions will increase, and it is expected that the design of the scanning optical system will become easier. For this reason, in a scanning optical device having a surface tilt correction optical system, the density of the scanning optical system has been increased due to the need to correct the field curvature.
Furthermore, the required precision of the f-theta lenses used is increasing, and the number of lenses is also increasing, making assembly and adjustment difficult and increasing the cost of scanning optical devices due to the increased number of parts. There is a problem of rising prices.

The present invention has been made in view of the above circumstances, and incorporates a new field curvature correction mechanism system into a conventional surface tilt correction optical system, thereby facilitating the design of lens systems such as fθ lenses, collimating lenses, cylindrical lenses, etc. The purpose is to provide a high-performance scanning optical device, and in particular, to avoid the use of a complicated and expensive lens system with a large number of lenses, in response to the increasing density of optical systems in scanning optical devices in recent years. It is an object of the present invention to provide an inexpensive and high-performance scanning optical device that can correct field curvature.

Furthermore, in the present invention, when correcting field curvature by movement or vibration of the cylindrical lens accompanying deflection scanning in a scanning optical device, the movement or vibration of the lens is accurately detected and this detection signal is fed back to the control system. By doing so, the objective is to achieve high accuracy in correction of field curvature, reduce the cost of an fθ lens system, and improve printing quality.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a light source, a collimating optical system that substantially collimates the light beam emitted from the light source, and a first imaging system that forms a linear image of the substantially collimated light beam. an optical system, a deflection reflection surface that deflects and scans the light beam emitted from the first imaging optical system, a scanned medium that is scanned by the light beam deflected by the deflection reflection surface, the scanned medium and the deflection The deflection reflection surface is arranged between the reflective surface and the deflected light beam to form an image on the scanned medium, and the deflection reflection surface in a plane perpendicular to the scanning surface (sub-scanning direction) of the light beam deflected by the deflection reflection surface. In a scanning optical device having a second imaging optical system that maintains a geometrically conjugate relationship between the surface and the scanned medium, the first imaging optical system is provided to move or vibrate in the direction of its optical axis, and includes a detection light source for detecting the moving position of the first imaging optical system, and a light receiving section that receives the light flux from the light source. and a regulating member for regulating the light flux from the detection light source is provided in the first imaging optical system, and by regulating the light flux from the detection light source with the regulation member. This is to prevent detection errors and the like by preventing excess light from being applied to the light receiving section.

Further, in the above scanning optical device, an aperture member may be provided in the first imaging optical system as a regulating member for regulating the light flux from the detection light source. The size of the aperture of this aperture member changes with respect to the movement direction or vibration direction of the first imaging optical system, and by changing the aperture size in this way, changes in the amount of light with respect to movement are magnified. This improves detection accuracy.

[For production]

In the scanning optical device according to the present invention, the light beam emitted from the light source becomes a substantially parallel light beam in the collimating optical system, and is incident on the first imaging optical system including a cylindrical optical system or the like. The light flux that has passed through the first imaging optical system is formed into a linear image, and then reflected by the deflection reflection surface of the rotating polygon mirror, and is deflected and scanned. The light flux deflected and scanned by the rotating polygon mirror is formed into an M image on a scanned medium such as a photoreceptor by a second imaging optical system consisting of an fθ lens, and scans the scanned medium while connecting minute spots. .

Here, the second imaging optical system consisting of an fθ lens and the like is disposed between the scanned medium and the deflection reflection surface of the rotating polygon mirror.
The deflected light beam is imaged on the scanned medium, and the deflection reflection surface and the scanned medium are geometrically conjugated in a plane perpendicular to the deflection scanning plane of the light beam deflected by the rotating polygon mirror. The position of linear imaging by the first imaging optical system is adjusted in the optical axis direction in synchronization with the deflection scanning of the rotating polygon mirror. It is moved or vibrated and acts to correct field curvature.

Further, it has a light source for detecting the moving position of the first imaging optical system, and detects a change in the amount of light due to the movement of the first imaging optical system with a light receiving section that receives the light flux from the light source, By feeding back this detection signal to a control system that controls the movement or vibration of the first imaging optical system, it becomes possible to control the movement or vibration of the first imaging optical system in accordance with the deflection scanning accurately.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings.

First, a basic configuration example of a scanning optical device to which the present invention is applied will be explained.

FIG. 12 is a schematic configuration diagram of a scanning optical device to which the present invention is applied, and this scanning optical device uses a semiconductor laser (LD
), a collimating lens 2 for substantially collimating the light beam emitted from the light source 1, and an aperture 3 for cutting unnecessary portions of the light flux substantially collimated by the collimating lens 2. , a first cylindrical lens 4 that forms a linear image of the light beam that has passed through the aperture 3, and a rotating polygon tR (polygon mirror) 5 that has a deflection and reflection surface that deflects and scans the light beam emitted from the first cylindrical lens 4. , a photoreceptor 7 which is a scanned medium scanned by the light beam deflected by the rotating polygon mirror 5; an fθ lens system that maintains a geometrically optically conjugate relationship between the deflection reflection surface and the photoreceptor 7 in a plane perpendicular to the deflection scanning plane of the light beam that forms an image on the body 7 and is deflected by the rotating polygon mirror 5; 6, the first cylindrical lens 4 is moved in the optical axis direction as the light beam of the rotating polygon mirror 5 scans, and the deflection reflecting surface of the rotating polygon i5 is caused by the first cylindrical lens 4. It is characterized by being arranged near the linear imaging position.

In the figure, reference numeral 8 denotes a second cylindrical lens, and reference numeral 9 denotes a mirror disposed at the scanning end of the light beam deflected and scanned by the rotating polygon mirror 5, and reflects a part of the light beam 10 reflected by the mirror 9. It is a synchronous detector that detects luminous flux.

Now, in the scanning optical device having the configuration shown in FIG.
The light beam emitted from the laser light source 1 passes through the collimating lens 2 to become a substantially parallel light beam, and after cutting off unnecessary peripheral parts by the aperture 3, it enters the first cylindrical lens 4. The light beam passing through the first cylindrical lens 4 is deflected and scanned by a rotating polygon mirror 5, and fθ
An image is formed on the photoreceptor 7 through an fθ lens system including a lens and a second cylindrical lens 8, and the image is scanned on the photoreceptor 7 while connecting minute spots.

Further, the light beam at the scanning end during scanning is guided by a mirror 9 to a synchronization detector 10, and data writing is synchronized based on a signal from this synchronization detector 1°.

Also, based on the signal from this synchronization detector 10, the first
By moving the cylindrical lens 4 in the optical axis direction, the field curvature of the optical system is corrected.

Further, an fθ lens system 6 disposed between the photoconductor 7 and the deflection reflecting surface of the rotating polygon mirror 5 forms an image of the deflected light beam on the photoconductor 7, and the beam is deflected by the rotating polygon mirror 5. The deflection reflection surface and the photoreceptor 7 are maintained in a geometrically optically conjugate relationship in a plane perpendicular to the deflection scanning plane of the light beam, and the deflection reflection surface is corrected for surface inclination.

Next, FIG. 13 shows a conceptual diagram of the optical system of the scanning optical device shown in FIG. Figure 13 (b
) is a conceptual diagram of the optical system on a plane (sub-scanning direction) that is perpendicular to the deflection scanning plane and includes the optical axis.

Here, in this optical system, as described above, the single-plane tilt correction is performed using an anamorphic optical system in which the fθ lens system 6 is an anamorphic optical system, and the deflection reflection surface 5a of the rotating polygon mirror 5 and the image surface 2 are geometrically optically adjusted in sub-scanning. This is done by arranging them in a conjugate relationship.

Incidentally, reference numeral 11 in the figure indicates soundproof glass that covers the outer periphery of the rotating polygon mirror 5.

Next, FIG. 14 shows the movement of the imaging position when the first cylindrical lens 4 is moved in the optical axis direction in the optical system shown in FIG. 13.

Here, in FIG. 14, the lens position and luminous flux before the movement of the first cylindrical lens 4 are represented by a solid line, and after the movement is represented by a broken line, and the amount of movement of the first cylindrical lens 4 is represented by Δc
The amount of movement of the imaging position when y is assumed to be Δrs.

Also, the distance between the imaging position of the first cylindrical lens 4 before movement and the principal point position of the fθ lens system 6 is S, the imaging position of the FE lens system 6 is S', and the focal length of the fθ lens system 6 is f.
Then, at this time, it can be expressed as S'f S=S'-f, and similarly, it can be expressed as. Therefore, Δl5−f”.

Here, if ΔIS<S'-f, Δl5−f2 Δcy= (S’-f)” (However, it can be expressed as m=S'/S).

That is, when the field curvature is ΔIS, the sub-scanning field curvature can be corrected by moving the first cylindrical lens by Δcy=ΔIS/m2 and moving its linear imaging position.

Further, at this time, in the main scanning, as shown in FIG. 13(, ), the first cylindrical lens 4 has no power, so there is no change in the curvature of field.

15(a) and 15(b) respectively show aberration diagrams before and after correction of field curvature by the above-mentioned scanning optical device.
The curvature of field before correction shown in Figure (a) is set so that the curvature of field is small in the main scan a, but no consideration has been taken to reduce the curvature of field in the sub-scan. ,
The curvature of field on the sub-scanning side is arcuate or parabolic. Also, the amount of curvature is +30” in scanning half-width.
Approximately LOmm at the position (the polygon rotates +15°)
It becomes. This curve can be approximated by a part of a sine wave or a cosine wave, and when the amount of correction and the amount of curvature of field are plotted, the line diagram shown in FIG. 16 is obtained.

In addition, the amount of field curvature of +30'' in FIG. 15(a) is expressed as ΔIs
Then, the amount of correction for field curvature is preferably ΔIS(θ)=Δl5(−cos(6θ)+1). However, in the above equation, θ is the polygon rotation angle, and when θ=O, the image height ratio is O.

Now, in the scanning optical device shown in FIG. 13, since the rotating polygon mirror 5 has six reflective surfaces, the polygon rotation angle .theta. of the negative surface can be set to +30 degrees. Therefore, if the first cylindrical lens 4 moves n cycles (n is an integer of 1 or more) during this +30°, the first cylindrical lens 4 will move smoothly when the next reflecting mirror surface comes around. Can be done. That is, when the number of mirror surfaces of the rotating polygon mirror 5 is N, +180" / N T n
The periodic first cylindrical lens 4 will move. Therefore, by moving the first cylindrical lens 4, the sub-scanning field curvature can be corrected as shown in FIG. 15(b). Furthermore, at this time, the curvature of field in the main scan does not change.

Note that FIG. 14 above shows the case where n=1.

As the movement mechanism for the first cylindrical lens described above, an actuator for moving an objective lens used in an optical pickup optical system for an optical disk or the like can be used.

Now, as explained above, in the scanning optical device according to the present invention, the linear imaging position by the first cylindrical lens is provided movably in the optical axis direction, and the first The cylindrical lens is periodically moved in the optical axis direction to move its linear imaging position in the optical axis direction,
Since it has a correction mechanism that corrects field curvature, it is possible to reduce field curvature with high precision.

By the way, in a scanning optical system using a rotating polygon mirror having a plurality of deflection and reflection surfaces, in order to correct field curvature,
It is necessary to control the linear imaging position by the first imaging optical system such as the first cylindrical lens to vibrate or move at several 100 to 1000 Hz in synchronization with the deflection scanning by the one-rotation polygon mirror. However, when this control is performed using open-loop control that simply moves periodically in accordance with the deflection scan, there is a problem that the actuator's operation is delayed and cannot follow the movement, and the effect of field curvature correction is not improved. A problem arises.

Therefore, in the present invention, in a scanning optical system configured such that the first imaging optical system is moved in the direction of its optical axis in accordance with the deflection scanning of the deflection reflecting surface of the one-rotation polygon mirror, the first imaging optical system is moved in the direction of its optical axis. A light source for detecting the moving position of the optical system and a light receiving section for receiving the light beam from the light source are provided, and the optical axis of the light source is set to be substantially perpendicular to the optical axis of the scanning light.

That is, in the scanning optical device according to the present invention, by providing the detection means using the detection light source and the light receiving section, the detection means accurately detects the moving position of the first imaging optical system, and the detected position is determined by the deflection. The idea is to perform feedback control (closed-loop control) to accurately follow scanning, and to improve the accuracy of field curvature correction.

Hereinafter, a detailed explanation will be given based on specific examples.

FIG. 1 is a perspective view showing a schematic configuration of main parts of a scanning optical system showing an embodiment of a scanning optical device according to the present invention, and reference numeral 5 in the figure shows a rotating polygon mirror (polygon) having a plurality of deflection and reflection surfaces. mirror).

Further, reference numeral 22 is a cylindrical lens which is the first imaging optical system, and is adapted to move or vibrate along the optical axis R as described above. Reference numeral 20 denotes a detection light source for detecting the moving position of the cylindrical lens 22, which is the first imaging optical system, or an optical fiber that guides a light beam from the light source, and is provided above the cylindrical lens 22.

Reference numeral 23 is a regulating member that regulates the light flux from the detection light source (or optical fiber) 20, which is a feature of the present invention, and its function is similar to that of a knife. Reference numeral 21 denotes a light receiving section that receives the light beam from the detection light source 20. Note that the regulating member 23 is provided integrally with the cylindrical lens 22 and is configured to move simultaneously with the cylindrical lens 22.

FIG. 2(a) is a side plan view of the first imaging optical system portion of the scanning optical system shown in FIG. The light flux is restricted by the regulating member 23, and a part of the light flux (the shaded area already shown in the figure) is blocked. Then, the unblocked luminous flux (a in the figure)
) reaches the light receiving section 21. Light receiving section 2 at this time
FIG. 2(b) shows the state of the luminous flux on 1.

Here, FIG. 3 shows the correspondence between the amount of light received by the light receiving section 21 and time, that is, the movement of the cylindrical lens 22.

As shown in FIG. 3, the formula for varying the amount of light is, if the maximum value of the amount of light is Tmax and the minimum value of the amount of light is lm1n, then from the movement formula of the cylindrical lens 22 (the above-mentioned formula for the correction amount of field curvature), It is expressed as

Therefore, the amount of movement of the cylindrical lens 22 can be determined from the amount of light, and if this is fed back to a control system (not shown) that moves or vibrates the cylindrical lens 22, accurate control corresponding to deflection scanning becomes possible.

Next, FIG. 4 is a diagram showing another example of the arrangement positions of the detection light source, the regulating member, and the light receiving section, in which the light source 20 is arranged to the right of the cylindrical lens 22, and the regulating member 23' is located at the light source. In this example, the light receiving section 21' is arranged on the side surface of the cylindrical lens facing the detection light source 20, and the light receiving section 21' is arranged on the left side of the cylindrical lens 22 and on the optical axis of the light beam from the detection light source 20. This arrangement in Figure 4 and the first
Considering the arrangement shown in the figure, the arrangement positions of the detection light source, regulating member, and light receiving section are the cylindrical lens 2.
2 top and bottom.

It is clear that it can be set in any direction, left or right.

In addition, in both FIGS. 1 and 4, the regulating member 23 (
23') is shown as being attached to the cylindrical lens 22, but as shown in FIG. It is also possible to have the effect of

Next, FIG. 6 is a perspective view showing a schematic main part configuration of a scanning optical system showing another embodiment of the present invention, and similarly to FIG. A rotating polygon mirror with
22 is a cylindrical lens which is a first imaging optical system, and is adapted to move or vibrate along the optical axis R as described above.

Further, reference numeral 20 denotes a detection light source for detecting the moving position of the cylindrical lens 22, which is the first imaging optical system, or an optical fiber that guides a light beam from the light source, and is provided above the cylindrical lens 22. code 23
is a regulating member that regulates the light flux from the detection light source (or optical fiber) 20, which is a feature of the present invention. In this embodiment, the regulating member 23 is formed by a plate-shaped aperture member having an opening approximately in the center. The aperture member has an aperture shape whose size changes in the direction of movement or vibration of the cylindrical lens 22. Further, reference numeral 21 denotes a light receiving section that receives the light beam emitted from the detection light source 20 and transmitted through the opening of the regulating member (opening member) 23.

FIG. 7 is a diagram showing how the light flux from the detection light g20 is restricted by the regulating member 23. FIG. ) respectively indicate the time when the view is at its maximum (Iimax). Note that Ω in the figure indicates the maximum length of the opening.

Furthermore, Fig. 8 shows an example in which a rectangular opening is provided whose size does not change, and Fig. 8(a) shows that when the amount of transmitted light is the minimum (1, m1n) FIG. 8(b) shows the case where the amount of transmitted light is maximum (I2max).

Note that Q in the figure is the same length as the maximum length Q of the opening shown in FIG.

Now, let's compare FIG. 7 and FIG. 8.

11m1n<I,min, I,max<I2m
Although it is ax, (engineering, [oax-11min) ) (I2max-I
, ff1in). Therefore, the aperture shape shown in FIG. 7 can increase the difference in light amount.

FIG. 9 shows a regulating member having the opening shape shown in FIG. 7;
9 is a diagram showing the correspondence between the amount of light at the light receiving section 21 and time, that is, the amount of light and the amount of movement of the cylindrical lens 22 when using the regulating members each having the opening shape shown in FIG. 8. FIG.

The variation formula for the light quantity I, , I, in FIG. 9 is expressed as follows, but since the variation width of I, is larger, the detection accuracy is improved with the aperture shape shown in FIG. 7.

Therefore, using the cylindrical lens 22
If feedback is applied to the control system that controls the movement or vibration of the deflector, accurate control corresponding to deflection scanning becomes possible.

Next, FIGS. 10 and 11 show different examples of opening members 25 and 26 used as regulating members, respectively.
In the example shown in FIG. 0, the direction of the opening of the opening member 25 is
This is a reverse example of what is shown in Figures and Figure 7, and
In the example shown in FIG. 11, the longest end of the opening of the opening member 26 is cut off to open one side.

〔Effect of the invention〕

As explained above, in the scanning optical device according to the present invention, the linear imaging position by the first imaging optical system is moved or vibrated in the optical axis direction in response to the deflection scanning by the deflection reflection surface, so that the image plane Because of the configuration that corrects curvature, it is possible to correct field curvature without using a complicated and expensive special lens system, so it is possible to provide a relatively inexpensive scanning optical device.

Furthermore, in the present invention, by detecting the movement position of the first imaging optical system, a detection signal from the imaging state detection means is fed back to the movement control system of the first imaging optical system. Therefore, it is possible to easily control the movement of the first imaging optical system following the deflection scanning, and it is possible to improve the accuracy of correcting field curvature. Furthermore, according to the present invention, it is possible to use highly accurate position detection means that could not conventionally be used to detect changes in the linear imaging position, so it is possible to perform highly accurate movement control. becomes.

Moreover, since the detection means is configured by combining a light source, a regulating member with a simple structure, and a light receiving section, the detection means can be manufactured at low cost.

Furthermore, when an aperture member having an aperture whose size changes with respect to the movement or vibration direction of the first imaging optical system is used as the regulating member, the first imaging optical system It is possible to increase the change in the amount of light received by the light receiving section with respect to movement or vibration of the sensor, and it is possible to improve detection accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main parts of a scanning optical system showing an embodiment of the present invention, and FIG. 2(a) shows a side view of the first imaging optical system part of the scanning optical system shown in FIG. Plan view from above, Figure 2 (b
) is an explanatory diagram of the light receiving state of the light flux at the light receiving section shown in FIG. 1 and FIG. 2 (a), and FIG. A diagram showing the correspondence with time when the lens is moved. Figure 4 is a schematic diagram of the main parts of the scanning optical system when the positions of the detection light source, regulating member, and light receiving section are changed. Figure 5 is the cylindrical lens. FIG. 6 is a schematic perspective view of a holding member that supports a holding member and is integrally equipped with a regulating member. FIG. Figure 7 (a), (b)
) is a diagram showing how the light flux from the detection light source shown in Figure 6 is restricted by the regulating member, and Figures 8 (a) and (b) are diagrams showing the light flux from the detection light source when the aperture shape is rectangular. Figure 9 is a diagram showing how the luminous flux of is restricted by the regulating member.
, a diagram showing the correspondence between the light-receiving scene at the light-receiving unit shown in FIG. 8 and the time when the cylindrical lens moves, and FIGS. 10 and 11 are diagrams showing different examples of the aperture member used as the regulating member. , FIG. 12 is a schematic main part configuration diagram showing an example of a scanning optical device to which the present invention is applied, and FIG. 13 is a conceptual diagram of the scanning optical system of the scanning optical device shown in FIG. FIG. 4A is a conceptual diagram showing the arrangement of the optical system on the deflection scanning plane, and FIG. FIG. 14 is an explanatory diagram for explaining the method of correcting field curvature in the optical system shown in FIG. 13, and FIG. 15 is an aberration diagram.
a) is an aberration diagram before the correction of the field curvature by the optical system shown in Fig. 13, the same figure (b) is an aberration diagram after the same correction, and Fig. 16 is the field curvature correction in the optical system shown in Fig. 13. FIG. 3 is a diagram showing the relationship between the amount of curvature of field and the amount of correction with respect to the scanning angle at time. 1...Laser light source, 2...Collimating lens,
3...Aperture, 4...First cylindrical lens, 5...Rotating polygon mirror, 5a...Deflection reflecting surface, 6...Fθ lens system, 7... Photoreceptor, 8
...Second cylindrical lens, 9...Reflection mirror, 10...Synchronization detector, 20...Detection light source, 21...Light receiving section, 22...Cylindrical lens , 23.25.26...Regulation member, 24...
・Holding parts. γ Mouth 4 Figure 1 Warm 70 Figure Otsu Most 4J Rut Sell Sell qσ Day (a) ) 4 Mouth ηf Shi D σ] tfn13guσ Way Z & Mouth θ. σ 3 Guza ν Bonro normal angle C

Claims (1)

[Scope of Claims] 1. A collimating optical system that substantially collimates a light beam emitted from a light source, a first imaging optical system that forms a linear image of the substantially collimated light beam, and this first a deflection-reflection surface that deflects and scans the light beam emitted from the imaging optical system; a scanned medium that is scanned by the light beam deflected by the deflection-reflection surface; and a deflection-reflection surface disposed between the scanned medium and the deflection-reflection surface. and forms an image of the deflected light beam on a scanned medium, and at the same time forms a beam between the deflection reflection surface and the scanned medium in a plane perpendicular to the deflection scanning plane (sub-scanning direction) of the beam deflected by the deflection reflection surface. and a second imaging optical system maintained in a geometrically conjugate relationship, the first imaging optical system is moved in the direction of its optical axis as the light beam is deflected and scanned by the deflection reflecting surface. Alternatively, the first imaging optical system is provided so as to vibrate, and a detection means comprising a detection light source for detecting the moving position of the first imaging optical system and a light receiving section that receives the light beam from the light source is provided, and the above-mentioned A scanning optical device characterized in that the first imaging optical system is provided with a regulating member that regulates the light flux from the detection light source. 2. In the scanning optical device according to claim 1, an aperture member is provided in the first imaging optical system as a regulating member for regulating the light flux from the detection light source, and the aperture member has an aperture size of a first diameter. A scanning optical device characterized in that the scanning optical device changes with respect to a moving direction or a vibration direction of an imaging optical system.