JP2000171742A - Scanning optical system and scanning image pickup optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an installation space by simplifying a structure. SOLUTION: A light source 21, a condensing lens system 22 and a scanning means 23 are successively arranged on an optical axis 20, and a surface to be scanned 24 is scanned with a luminous flux deflected by the scanning means 23. The condensing lens system 22 is constituted of a fixed condensing lens 22a and a focus variable lens 22b, and the light source 21, the focus variable lens 22b and the scanning means 23 are synchronously controlled by a control circuit 25. The focus variable lens 22b is formed by covering transparent liquid 31 with front and rear transparent elastic bodies 32a and 32b and a case 33. A driving ring 34 is provided at the inside of the case 33 on the rear side of the transparent elastic body 32b, and the driving ring 34 is driven in a back-and- forth direction by an actuator 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a scanning optical system for forming an image on a photosensitive drum or the like, and a scanning imaging optical system for obtaining an image from a subject or the like.

[0002]

2. Description of the Related Art FIG. 15 shows a conventional scanning optical system used in a laser printer. In this scanning optical system, a light beam emitted from a light source 1 is sensitized via a condenser lens 2 and a polygon mirror 3 to a light beam. The light is condensed on the photosensitive drum 4 on the drum 4 and is scanned in the main scanning direction. At this time, the drive circuit 5 performs control based on the signal input to the light source 1. The photosensitive drum 4 rotates in a sub-scanning direction orthogonal to the main scanning direction. The light source 1 and the scanning in both directions are controlled synchronously to form a latent image on the photosensitive drum 4 based on two-dimensional information by main scanning and sub scanning. Then, the latent image is transferred to recording paper through processes such as development, transfer, and fixing.

In such a scanning optical system, the optical path length between the polygon mirror 3 and the photosensitive drum 4 differs depending on the position in the main scanning direction. Although the light is condensed at the light point Pc, the light is condensed at the light condensing points Pc ′ in front of the photosensitive drum 4 at both ends of the photosensitive drum 4, and the resolution decreases as the light moves toward both ends.

On the other hand, a scanning optical system which prevents such a decrease in resolution is disclosed in Japanese Patent Application Laid-Open No. 58-179315. In this scanning optical system, as shown in FIG. 16, the above-described condenser lens 2 includes a moving lens 2a and a fixed lens 2
b. In the moving lens 2a, as shown in FIG. 17, the lens 11 is held by the flexure 12, and the flexure 12 is installed so as to be able to move back and forth. A coil 13 is wound around the outer periphery of the flexure 12, and a pair of ring-shaped magnets 14 and 15 are arranged before and after the coil 13. The flexure 12, that is, the movable lens 2a is driven by an electromagnetic force generated between the coil 13 and the magnets 14 and 15, so that the condensing position on the photosensitive drum 4 is controlled in synchronization with the position in the main scanning direction. It has become.

[0005]

However, in the above-mentioned conventional example shown in FIG.
On the other hand, a space for moving the movable lens 2a is required, while a reduction in the resolving power at the position Pc 'separated from both ends from the position c can be prevented. In addition, the flexure 12 is installed so as to be able to move back and forth, and a magnet 14 is provided before and after the coil 13.
The arrangement is complicated because of the arrangement of 15.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a scanning optical system and a scanning imaging optical system which can adjust the focus with a simple configuration.

[0007]

According to the present invention, there is provided a scanning optical system for scanning a light beam emitted from a light source, and condensing the light beam from the light source on a surface to be scanned. A focusing optical system having a focus adjusting means for adjusting the focus,
The focus adjusting means is constituted by enclosing an optically transparent liquid in an elastic body, and the focus is adjusted by deforming one surface of the elastic body.

A scanning image pickup optical system according to the present invention is a scanning image pickup optical system comprising a scanning unit, an image forming optical system, and an image pickup device, wherein the image forming optical system includes a focus adjusting unit for adjusting a focus. It is characterized by being arranged between the scanning means and the image sensor.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a block diagram of the first embodiment, which is a scanning optical system such as a laser beam printer. On the optical axis 20, a light source 21, a condenser lens system 22, and a scanning unit 23 are sequentially arranged.
The light beam deflected by the scanning on the surface to be scanned 24. The condenser lens system 22 includes a fixed condenser lens 22a and a variable focus lens 22b. The light source 21 is a semiconductor laser light source, and is disposed at the focal point of the fixed condenser lens 22a. The scanning means 23 is a polygon mirror, and the surface to be scanned 24 is the surface of the photosensitive drum. Then, the light source 21, the variable focus lens 22b, and the scanning unit 2
3 is connected to the control circuit 25.

FIG. 2 is a structural view of the variable focus lens 22b. An optically transparent liquid 31, such as silicone oil, is wrapped by front and rear transparent elastic bodies 32a and 32b and a case 33 to form a lens. . A drive ring 34 is provided inside the case 33 behind the rear elastic body 32b,
The drive ring 34 is driven in the front-rear direction by an actuator 35. The actuator 35 is a bimorph ring body in which a piezoelectric element has a bimorph structure, and is driven according to an electric signal from the control circuit 25.

This type of variable focus lens 22b is described in, for example, "MOEMS97 Technical Digest (November 18-21, 1997, Nara, pp. 55-61)".
`` Quick-Response Dynamic Focusing Utilizing Pi
ezoelectric Bimorph Actuator ". The effective beam diameter of the variable focus lens 22b is 5 mm,
For driving a piezoelectric bimorph ring with an outer diameter of 14 mm
When the body is stacked, high-speed driving with a frequency response up to 300 Hz is possible.

In the scanning optical system of the first embodiment, the light beam emitted from the light source 21 passes through the fixed condenser lens 22a and the variable focus lens 22b of the condenser lens system 22, and is reflected by the scanning means 23. , The condensing position Pc1 on the scanned surface 24,
Scanning is performed in the main scanning direction on Pc0 and Pc2, and scanning is performed in the sub-scanning direction orthogonal to the main scanning direction by rotating the surface to be scanned 24. At this time, the control circuit 25 controls the light source 21, the focus variable lens 22b, the scanning means 23, and the surface to be scanned 24 in synchronization.

During this time, the actuator 35 drives the drive ring 34 in a direction parallel to the light beam, and presses one of the transparent elastic members 32a as shown in FIG.
2a and 32b are deformed, and the focus variable lens 22b acts as a convex lens. Then, the control circuit 25 controls a signal sent to the actuator 35 to control the amount of deformation of the transparent elastic body 33a, that is, the focus.

As a result, as shown in the developed view of FIG. 4 excluding the polygon mirror 3, the light beam from the light source 1 is collimated by the fixed condenser lens 22a, and the collimated light beam is changed by the focus variable lens 22b to the scanning surface. At the center on the top 24, the light is condensed at the position Pc0, and at both ends, the light is condensed at the positions Pc1 and Pc2, thereby preventing a decrease in resolution at a position away from the center.

As described above, in the first embodiment, the transparent liquid 3
1 is wrapped by the transparent elastic bodies 32a and 32b and the case 33, and one of the transparent elastic bodies 32a is deformed, so that the configuration of the focus variable lens 22b is simplified and
The response speed of the variable focus lens 22b is improved, and no vibration occurs during response. Also, the variable focus lens 22b
Since it does not move itself, the installation space is reduced.

In the first embodiment, the scanning means 23
A similar effect can be achieved by employing a galvanomirror, an electro-optical element, a variable apex prism, or the like. The scanned surface 24 may be a display screen or recording paper. Further, the actuator 35 is a piezoelectric bimorph ring, but is not limited to this.

FIG. 5 is a diagram showing a main part of a modification of the second embodiment, in which a condenser lens system 22 'is arranged in place of the condenser lens system 22 of the first embodiment. This condenser lens system 2
In 2 ′, in addition to the fixed condenser lens 22a and the variable focus lens 22b of the first embodiment, a fixed lens 22c is disposed between the variable focus lens 22b and the scanning unit 23.

In this case, as shown in the developed view of FIG. 6, the light flux from the light source 21 is collimated by the fixed condenser lens 22a, and the combined focal positions Pc0, Pcl, Light is focused on Pc2.

FIG. 7 is a block diagram of another modification of the first embodiment, in which a lens 26 is arranged between the scanning means 23 and the surface 24 to be scanned in the first embodiment. In the third embodiment, the optical path between the scanning means 23 and the scanned surface 24 is
Since the light-collecting positions Pc0, Pcl, and Pc2 do not overlap with the light-collecting positions Pc0, Pcl, and Pc2, the light-collecting positions Pc0, Pcl, and Pc2 can be corrected in accordance with a change in the focus of the focus variable lens 22b.

At this time, the focal position of the variable focus lens 22b and the scanning position of the scanning means 23 are synchronized, and the light emitting state of the light source 21 is controlled accordingly. Further, the focus variable lens 22b controls according to the distance between the scanning unit 23 and the surface to be scanned 24 and the scanning angle of the scanning unit 23.

FIG. 8 is a block diagram of another modified example of the first embodiment. In the modified example shown in FIG. 7, a distance detecting means 27 for detecting the distance to the surface to be scanned 24 is added. The distance detecting means 27 is electrically connected to the control circuit 25, and the focus variable lens 22b is controlled based on information on the distance of the distance detecting means 27. In this modification, an appropriate light-collecting state can be obtained even if the distance to the surface to be scanned 24 changes.

In the first embodiment, a one-dimensional scanning optical system has been described. However, by moving these scanning optical systems in a sub-scanning direction orthogonal to the main scanning direction, a two-dimensional scanning optical system is obtained. An optical system can be obtained.

FIG. 9 is a block diagram of the second embodiment, in which the converging lens system 4
2. The scanning means 43 and the scanned surface 44 are sequentially arranged. The light source 41 is a laser light source, and a condenser lens system 42
Is composed of a fixed condenser lens 42a and a variable focus lens 42b. The scanning unit 43 is a galvanomirror capable of scanning a light beam in a two-dimensional direction, and the scanned surface 44 is a screen. The light source 41, the variable focus lens 42b, and the scanning means 43 are connected to a control circuit 45, and the control circuit 45 performs synchronous control so as to form an appropriate image on the scanned surface 44.
This second embodiment can also achieve the same effects as the first embodiment.

The light source 41 can be replaced with a light source other than a laser light source. Further, a lens having the same configuration as the variable focus lens 22b of the first embodiment can be used as the variable focus lens 42b, and a plurality of lenses or a single lens may be used. The scanning unit 43 can achieve the same effect as a combination of a plane mirror, a combination of a polygon mirror and a mirror, an electro-optical element, a variable apex prism, and the like.

FIG. 10 is a block diagram of a modification of the second embodiment. The light source 41 of the second embodiment includes a plurality of light source groups 41a to 41a.
A color image is displayed on the scanned surface 44 by appropriately setting the emission wavelength of each of the light source groups 41a to 41c.

FIG. 11 is a block diagram of another modification of the second embodiment, in which a lens system 46 is arranged between the scanning means 43 and the surface to be scanned 44 of the modification shown in FIG. In this modified example, even when the optical path between the scanning unit 43 and the surface to be scanned 44 differs depending on the scanning direction, the optical performance according to the scanning position can be corrected, and the optical characteristics associated with a change in focus can be corrected.

FIG. 12 is a block diagram of the third embodiment, which is a scanning image pickup optical system. An image sensor 5 is provided on the optical axis 50.
1. An imaging optical system 52 and a scanning unit 53 are arranged, and the scanning unit 53 can scan a scanned surface 54 of a subject. The imaging device 51 is a photoelectric conversion device including one or more pixels, and converts an image formed by the imaging optical system 52 into an electric signal. Imaging optical system 52
Is composed of a fixed condenser lens 52a and a variable focus lens 52b. The scanning unit 53 is a two-dimensional scanning unit such as a galvanometer mirror, and the optical axis 50 is deflected. Then, an image sensor 51 and a variable focus lens 52
b. The scanning means 53 is connected to the control circuit 55 and is controlled synchronously.

The variable focus lens 52b is a lens having excellent high-speed response similar to the variable focus lens 22b of the first embodiment, and controls a conjugate position with respect to the photoelectric conversion element 51 and the imaging optical system 52. It is possible to do. The image sensor 51 and the scanned surface 54 are arranged at conjugate positions, and by changing points on the scanned surface 54 by the scanning means 53, the image sensor 51 can obtain an image on the scanned surface 54. Have been.

FIG. 13 shows a state in which a plane including the optical axis 50 is scanned, and shows that the object distance between the scanning means 53 and the surface to be scanned 54 changes according to the scanning angle θ. The object distance of the scanning point 56b with respect to the scanning angle θ changes with respect to the object distance of the scanning point 56a at the intersection of the one scanned surface 54a and the optical axis 50.
δ = D / cos θ−D.

Therefore, the control circuit 55 only needs to control the focus variable lens 52b so as to obtain the change amount δ according to the scanning angle θ, and the signals obtained from the image sensor 51 are rearranged in the scanning order to form one object. An image on the scanning surface 54a can be obtained. In practice, the correction of the change amount δ depending on the deflection direction by the scanning means is also performed. By sequentially moving the other scanned surfaces 54b, 54c,...
It is possible to capture an image even in a space that has an extension in the depth direction.

FIG. 14 is a block diagram of a modification of the third embodiment. An image sensor 51 'such as a CCD is used in place of the image sensor 51 of the third embodiment.
Is a photoelectric conversion element in which photoelectric conversion units are two-dimensionally distributed. Then, the imaging element 51 ′, the focus variable lens 5
2b and the scanning means 53 are connected to the control circuit 55, and are controlled synchronously.

In this modification, since the photoelectric conversion elements are two-dimensionally distributed, areas 58a, 58b,... Can be formed on one scanning surface 54a. In this case,
The image sensor 51 'and the area 58a on the surface to be scanned 54a correspond to each other. By scanning with the scanning means 53 and controlling the focal length with the variable focus lens 52b, a wide range of images can be obtained. The scanning surface 54
By moving b, 54c,..., an image can be obtained also in the depth direction.

In the third embodiment, an optical system may be arranged between the scanning means 53 and the surface 54 to be scanned. Although the case where the scanned surface 54 is orthogonal to the optical axis 50 has been described, the synchronization between the focus variable lens 52b and the scanning unit 53 is changed even when the scanned surface 54 is inclined from the direction orthogonal to the optical axis 50. This allows the scanned surface 54 to be scanned.

Then, after one scanning surface 54a is scanned, the scanning surfaces 54b, 54c,... Are sequentially moved. However, if spatial scanning is possible as a result,
The order is not limited. Further, the image sensor 5
1, 51 'may be a photoelectric conversion element comprising one or more pixels, and a similar effect can be achieved by using a line sensor or an area sensor.

Further, the focus variable lens 52b is driven based on signals from the image pickup devices 51 and 51 'to automatically adjust the focus, and information on the distance is obtained from the state of the focus variable lens 52b at this time. You can also. In this case, a scanning imaging optical system capable of three-dimensional scanning can be realized.

[0036]

As described above, in the scanning optical system according to the present invention, the focus adjusting means is constituted by enclosing the optically transparent liquid in the elastic body, so that the structure of the focus adjusting means is simplified. At the same time, the installation space for the focus adjusting means is reduced.

Further, the scanning and imaging optical system according to the present invention can perform scanning and imaging on a plane in a space and a depth direction.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a configuration diagram of a variable focus lens.

FIG. 3 is an explanatory diagram of an operation of a variable focus lens.

FIG. 4 is an exploded view showing a state excluding a scanning unit.

FIG. 5 is a configuration diagram of a modified example of the first embodiment.

FIG. 6 is a development view excluding a scanning unit.

FIG. 7 is a configuration diagram of another modification of the first embodiment.

FIG. 8 is a configuration diagram of another modification of the first embodiment.

FIG. 9 is a configuration diagram of a second embodiment.

FIG. 10 is a configuration diagram of a modification of the second embodiment.

FIG. 11 is a configuration diagram of another modified example of the second embodiment.

FIG. 12 is a configuration diagram of a third embodiment.

FIG. 13 is an explanatory diagram of a scanning state.

FIG. 14 is a configuration diagram of a modification of the third embodiment.

FIG. 15 is a configuration diagram of a conventional example.

FIG. 16 is a configuration diagram of another conventional example.

FIG. 17 is a configuration diagram of a conventional moving lens.

[Explanation of symbols]

 21, 41, 51 Light source 22, 42, 52 Condensing lens system 22a, 42a, 52a Fixed condensing lens 22b, 42b, 52b Variable focus lens 23, 43, 53 Scanning means 24, 44, 54 Scanned surface 25, 45 , 55 control circuit 31 transparent liquid 32a, 32b transparent elastic body 33 case 34 drive ring 35 actuator

Claims (13)

[Claims] 1. A scanning device for scanning a light beam emitted from a light source, and a light condensing device for condensing the light beam from the light source on a surface to be scanned, wherein the light condensing device has a focal point for adjusting a focal point. In a scanning optical system having adjusting means, the focus adjusting means is constituted by enclosing an optically transparent liquid in an elastic body, and adjusts the focus by deforming one surface of the elastic body. A scanning optical system characterized in that: 2. The scanning optical system according to claim 1, wherein said focusing means includes at least one fixed lens having a positive refractive power. 3. The scanning optical system according to claim 1, wherein said focus adjusting means and said scanning means are synchronized. 4. The scanning optical system according to claim 1, wherein said light source, said focus adjusting means and said scanning means are synchronized. 5. The scanning optical system according to claim 2, wherein the fixed lens is a lens that collimates a light beam from the light source. 6. The scanning optical system according to claim 1, wherein said scanning means is capable of scanning in a one-dimensional direction or a two-dimensional direction. 7. The scanning optical system according to claim 3, wherein said focus adjustment means controls based on information on a distance of a scanning position. 8. The scanning optical system according to claim 7, further comprising a distance detecting means for detecting information on a distance of the scanning position. 9. The scanning optical system according to claim 8, wherein a lens system is arranged between the surface to be scanned and said scanning means. 10. A scanning image pickup optical system comprising a scanning unit, an image forming optical system, and an image pickup device, wherein the image forming optical system includes a focus adjusting unit for adjusting a focus, and the scanning unit and the image pickup device are connected to each other. A scanning and imaging optical system, wherein the focus adjusting means is disposed between the two. 11. The apparatus according to claim 10, wherein said focus adjusting means is constituted by enclosing an optically transparent liquid in an elastic body, and adjusts a focus by deforming one surface of said elastic body. A scanning imaging optical system according to claim 1. 12. The scanning imaging optical system according to claim 10, wherein said scanning means and said focus adjusting means are synchronized. 13. The scanning image pickup optical system according to claim 10, wherein said scanning means is capable of scanning in a two-dimensional direction.