JPH03185417A - Scanning optical device - Google Patents

Abstract

PURPOSE:To correct the curvature of an image surface comparatively inexpensively and to improve correction accuracy by providing a first image-forming optical system in such a way that it can be moved or slided in an optical axial direction and detecting the moving position of the system. CONSTITUTION:A cylindrical lens 22 that is the first image-forming system of a scanning optical system is provided in such a way that it can be moved or slided with an actuator, and a light source 20 for travel detection, a regulation reflecting member 23, and a light receiving part 21 are provided at the upper side of the lens 22. The curvature of the image surface can be corrected by moving or oscillating the cylindrical lens 22 in the optical axial direction corresponding to deflective scan in such constitution, and the correction can be performed comparatively inexpensively. At this time, the amount of travel of the lens 22 is detected with the light receiving quantity of the light receiving part 21, and the correction accuracy can be improved by feeding back a detection signal to the actuator and performing cloed loop control.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a scanning optical device used in a digital copying machine, a laser printer, a laser plotter, a laser facsimile, a laser plate making machine, etc. The present invention relates to a scanning optical device having the same structure and capable of reducing 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, when the imaging lens system of the scanning optical system that has the above-mentioned field curvature correction mechanism is a spherical lens, the spherical lens has an astigmatism difference, so generally the image in the main and sub scanning directions is The surface 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 field 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 of the main and dramatic image 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, operations such as ``performing sine vibration'' are described, but the control device and control method are not specifically described. It has not been done.

However, in a scanning optical system using a rotation number affi, it takes several hundred to several tens of times to correct the curvature of field.
It is necessary to perform vibration movement control at 00 Hz, and for this reason, with normal open loop control, there is a problem that the ix control is delayed and the control cannot follow the curvature of field, so the correction effect cannot be achieved. The problem arises that it cannot be done.

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, fθ characteristics (magnification error 1 uniform velocity scanning property), spherical aberration, sine conditions, etc. are required as optical system design conditions. They are in a trade-off relationship, and it is difficult to make all design conditions favorable at the same time. Therefore, if the above-mentioned field curvature can be corrected, the number of degrees of freedom 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 single-sided 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. Both can correct field curvature. The purpose is to provide an inexpensive and high-performance scanning optical device.

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, it is possible to improve the accuracy of field curvature correction and reduce the cost of the fθ lens system.

The purpose is to 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 reflection member for regulating the light flux from the detection light source is provided in the first imaging optical system, and the regulation reflection member regulates the light flux from the detection light source. This prevents excess light from being applied to the light receiving section, thereby preventing detection errors and the like.

Further, in the above-mentioned scanning optical device, the size of the reflection part of the regulation reflection member which regulates the light flux from the detection light source is changed with respect to the moving direction or the vibration direction of the first imaging optical system. By changing the size of the reflecting portion in this way, it is possible to magnify the change in the amount of light due to movement or vibration, and it is possible to improve detection accuracy.

Note that the detection light source is preferably arranged such that the optical axis of the light source is inclined with respect to the optical axis of the scanning light so as not to affect the scanning light.

[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. An image is formed on a scanned medium such as a photoreceptor by a second imaging optical system, and the scanned medium is scanned while forming 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.

It also has a detection light source for detecting the moving position of the first imaging optical system, and detects a change in light amount 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 the detection signal to a control system that controls the movement or vibration of the first imaging optical system, it is possible to control the movement or vibration of the first imaging optical system in accordance with the deflection scanning accurately. Become.

〔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 a seven-percher 3 for cutting unnecessary portions of the light beam 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 mirror 5 that has a deflection reflection surface that deflects and scans the light beam emitted from the first cylindrical lens 4. and a photoreceptor 7, which is a scanned medium that is scanned by the light beam deflected by the rotating polygon mirror 5.
A mirror is disposed between the photoreceptor 7 and the deflection reflection surface of the rotating polygon mirror 5, and forms an image of the deflected light beam on the photoreceptor 7, and is perpendicular to the deflection scanning plane of the light beam deflected by the rotation polygon mirror 5. It has an fθ lens system 6 that maintains a geometrically optically conjugate relationship between the deflection reflecting surface and the photoreceptor 7 within the plane.

The first cylindrical lens 4 is moved in the optical axis direction as the light beam of the rotating polygon 'R5 scans, and the deflecting reflection surface of the rotating polygon mirror 5 is moved to the linear imaging position by the first cylindrical lens 4. It is characterized by being placed nearby.

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.
A beam of light emitted from a laser light source 1 passes through a collimating lens 2 to become a substantially parallel beam of light, and after cutting unnecessary peripheral parts by an aperture 3, it enters a first cylindrical lens 4. The light beam passing through the first cylindrical lens 4 is deflected and scanned by the rotating polygon #15, and f
An image is formed on the photoconductor 7 through an fθ lens system including a θ lens and a second cylindrical lens 8, and the photoconductor 7 is scanned while forming minute spots.

Furthermore, 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 10.

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 also forms an image of the rotating polygon #! In a plane perpendicular to the deflection scanning plane of the light beam deflected by 5, the deflection reflection surface and the 6 light body 7 are maintained in a geometrically optically conjugate relationship, and act to correct the surface tilt of the deflection reflection surface. .

Next, FIG. 13 shows a conceptual diagram of the optical system of the scanning optical device shown in FIG. 12, and FIG. 13(a) is a conceptual diagram of the optical system on the deflection scanning surface (main scanning direction). 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 mentioned 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 in the sub-scanning, the deflection reflection surface 5a of the rotating polygon tlt5 and the image plane Z
This is done by arranging them in a geometrically optically conjugate relationship.

Note that reference numeral 11 in FIG. 1 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 ΔIS.

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 fθ lens system 6 is S', and the focal length of the fθ lens system 6 is f.
Then, at this time.

S'-f Similarly, It can be expressed as

therefore, becomes.

here.

If Δl5(S'-f), (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/m'' and moving its linear imaging position.

Further, at this time, in the main scanning, as shown in No. 13@(a), 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.

Since no consideration has been made to reduce the curvature of field in the sub-scanning side, the curvature of field on the sub-scanning side is arcuate or parabolic. In addition, the amount of curvature is approximately 10 am at a position of ±30 @ scanning half-width (the polygon rotates ±15 @)6, and this curve is approximated by a part of a sine wave or cosine wave. When the amount of correction and the amount of curvature of field are plotted, the 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 correction amount for field curvature should be ΔIS(θ)=Δl5(-cos(68)+1). However, in the above equation, θ is the polygon rotation angle, and when θ=0, the image height ratio is It becomes O.

Now, in the scanning optical device shown in FIG. 12, since the rotating polygon @5 has 6 reflecting mirror surfaces, the polygon rotation angle θ of the negative plane can be set to ±30 @. 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 primary reflecting mirror surface turns. be able to. That is, the rotating polygon mirror 5
When the number of mirror surfaces is N, the first cylindrical lens 4 moves in n periods at ±180@/N. Therefore, by moving the first cylindrical lens 4, the sub-scanning field curvature can be corrected as shown in FIG. 15(b). Also, at this time, the body surface curvature in the main scan does not move. 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 hundred inches at 100 GHz in synchronization with the deflection scanning by the rotating polygon mirror. However, this control If the actuator is simply moved periodically in accordance with the deflection scan using open-loop control, there is a problem that the actuator operation is delayed and cannot follow the movement, resulting in the problem that the field curvature correction effect is not improved. .

Therefore, in the present invention, in a scanning optical system configured such that the first imaging optical system is moved in the optical axis direction in accordance with the deflection scanning of the deflection reflecting surface of the rotating polygon mirror, the first imaging optical system A detection 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 so as not to be orthogonal to the optical axis of the scanning light. do.

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 description 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 the scanning optical device according to the present invention, and reference numeral 5 in FIG. 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 indicates α with respect to the optical axis R of the cylindrical lens 22 which is the first imaging optical system.
(<90@') It is a detection light source such as an LED that has an optical axis in an inclined direction, and in the case of Fig. 1, the cylindrical lens 2
It is located above 2. Reference numeral 23 denotes a regulating reflection member that regulates the light flux from the detection light source 20, which is a feature of the present invention. Reference numeral 21 denotes a light receiving section made of a PIN photodiode or the like that receives the light beam from the detection light source 20 after being reflected by the regulating reflection member 23. Note that the regulation reflection member 23 is provided integrally with the cylindrical lens 22 and is configured to move simultaneously with the cylindrical lens 22.

28th! ! I(a) is a plan view of the first imaging optical system part of the scanning optical system shown in FIG. Part of it is reflected by the member 23, and the reflected light beam a is transmitted to the light receiving section 21.
reach. Note that the boxes in Figure 1 indicate the light flux that was not reflected, and Figure 2 (b) shows the state of the light flux on the light receiving unit 21. The area of the light beam at the top is a reflected light portion a' and a portion 1' where no reflected light comes.

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 the equation for the movement of the cylindrical lens 22 (the formula for the amount of correction of field curvature described above), where the maximum value of the amount of light is xax and the minimum value of the amount of light is lm1n. Than.

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 reflection member, and the light receiving section, in which the light source 20' and the light receiving section 211 are arranged to the right of the cylindrical lens 22, and the regulating The reflecting member 23'' is connected to its light source 20' and light receiving section 2.
In this example, the lens 1' is disposed on the side surface of the cylindrical lens 22 facing the lens 1'. Considering the arrangement shown in FIG. 4 together with the arrangement shown in FIG.
It is clear that it can be set in any direction, up, down, left or right of 2.

In addition, in both FIGS. 1 and 4, the regulating reflective member 2
3 (23') is attached to the cylindrical lens 22, as shown in FIG. is also possible.

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, in which, like FIG. 1, the reference numeral 5 in FIG. A rotating polygon 11 having
1 (polygon mirror), and 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.

Further, reference numeral 20 indicates an LE having an optical axis in a direction tilted by α (<90”) with respect to the optical axis R of the cylindrical lens 22.
This is a detection light source such as D, and in the case of FIG. 6, it is provided above the cylindrical lens 22. Reference numeral 23 denotes a regulation reflection member that reflects the light beam from the detection light source 20. In this embodiment, the regulation reflection member 23 has a triangular reflection part (reflection surface) 23a approximately in the center, and this reflection Part 23
A is characterized in that the size changes in the direction of movement or vibration of the cylindrical lens 22. code 21
is a light receiving section such as a PIN photodiode that receives the light beam from the light source 20 after being reflected by the regulation reflecting member 23.

Figure 7' shows that the light flux from the detection light source 20 is regulated by the reflecting member 2.
3 is a diagram illustrating how a1. a is the part where the luminous flux is reflected, b, , b
□' is the part of the light beam that is not reflected. Therefore, Fig. 7 (
a) is when the amount of reflected light is the minimum (I, 5 inches), Figure 7 (b)
) indicates the time when the amount of reflected light is maximum (IXwax). Note that a in the figure indicates the maximum length of the reflecting portion 23a.

Moreover, FIG. 8 simply shows an example in which a rectangular reflecting portion whose size does not change is provided, and FIG. FIG. 8(b) shows the reflected scene when it is at its maximum (I, wax).

Note that Q in the figure is the same length as the maximum length a of the reflecting portion 23a shown in FIG.

Here, when comparing Fig. 7 and Fig. 8, 11w1n (
I, win I, wax<I, wax, but (11wax-11w+in) > (1,max-I
, win).

Therefore, the shape of the reflecting portion as shown in FIG. 7 can increase the difference in light amount.

FIG. 9 shows the amount of light and time at the light receiving section 21 when a regulating reflective member having a reflecting section shape shown in FIG. 7 and a regulating reflecting member having a reflecting section shape shown in FIG. 8 are used, respectively. 3 is a diagram showing the correspondence between the amount of light and the amount of movement of the cylindrical lens 22. 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 reflecting part 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, FIG. 1θ and FIG. 11 show different examples of the regulating reflective member, and in the example shown in FIG. This is an example in which the periphery of the central triangular portion 24a is a reflective surface, and in the example shown in FIG. be. In addition, in FIG. 11, the triangular portion 25a may not be used as a reflective surface, but a portion around the triangular portion 25a may be used as a reflective surface.

〔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, the 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 the accuracy of correcting field curvature can be improved. According to this method, it is possible to use highly accurate position detection means, which could not conventionally be used to detect changes in the linear imaging position, and therefore it is possible to perform highly accurate movement control.

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

Furthermore, by configuring the detection means as a reflection type, the light source and the light receiving section can be installed in the same direction with respect to the first imaging optical system, so the device can be made smaller and the cost can be reduced. .

Well, when a reflecting member having a reflecting part whose size changes with respect to the movement or vibration direction of the first imaging optical system is used as the regulating reflecting 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 drawings]

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. Figure 4 shows the correspondence with time when the lens moves. Figure 4 is a schematic diagram of the main parts of the scanning optical system when the positions of the detection light source, regulating reflection member, and light receiving section are changed. Figure 5 is the cylindrical configuration. FIG. 6 is a diagram showing an example of a case where regulating reflective parts are provided on the side surfaces or upper and lower surfaces of the lens, and FIG. 6 shows another embodiment of the present invention, using a regulating reflective member having a triangular reflecting part (reflecting surface). FIGS. 7(a) and 7(b) are schematic diagrams of the main parts of the scanning optical system in this case, and show how the light flux from the detection light source shown in FIG. 6 is restricted by the reflection part of the regulating reflection member. Figure 8 (a), (b)
) is a diagram showing how the light flux from the detection light source is restricted by the reflective part of the regulating reflective member when the reflective part is rectangular in shape, and Figure 9 shows the reflective part shown in Figures 7 and 8. A diagram showing the correspondence between the amount of light received at the light receiving unit and the time during movement of the cylindrical lens when a shaped regulating reflective member is used, FIGS. 10 and 11 are diagrams showing different examples of the regulating reflective 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 a scanning optical system of the scanning optical device shown in FIG. ) 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. Aberration diagram before field curvature correction, same figure (
b) is an aberration diagram after correction, and FIG. 16 is a diagram showing the relationship between the amount of curvature of field and the amount of correction with respect to the scanning angle when correcting the curvature of field in the optical system shown in FIG. 13. 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, 20.20''...
Detection light source, 21.21'... Light receiving section, 22...
...First cylindrical lens, 22a, 22b...
・・Regulation reflective part, 23.23', 24.25---
-i antireflection member, R...optical axis of scanning light. Shape δ Mouth shape 4's agitation shape C eye 9 illusion * 70 figure 4-/phantom v)-/f day 16 mouth 1d mouth ηf shi 45 Yuko (d) tφn

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 reflection member that regulates the light flux from the detection light source. 2. In the scanning optical device according to claim 1, the size of the reflection part of the regulation reflection member that regulates the light flux from the detection light source changes with respect to the moving direction or vibration direction of the first imaging optical system. A scanning optical device characterized in that: