JPH02296211A - Drum scanning type scanning optical device - Google Patents

Abstract

PURPOSE:To allow recording of color images at a high speed with a high resolution by rotating a rotary drum and an optical system around the same central axis of rotation and using a mirror for the optical system. CONSTITUTION:This device has the rotary drum 1, the inside surface of which is a surface to be irradiated and rotates in a direction A around the central axis 2 of a cylindrical shape, and the mirror 4 which is positioned on the inner side of the rotary drum 1 and rotates in a direction B around the central axis 2 of the rotary drum 1. Luminous fluxes lambda1 to lambda3 emitted from a light source are reflected by the mirror 4 and are condensed onto the surface to be irradiat ed. Namely, the mirror 4 does not generate chromatic aberrations and, therefore, the focusing of the luminous fluxes lambda1 to lambda3 of plural wavelengths onto the same point on the surface to be irradiated is possible. The high-speed scanning is executed in this way and the spot diameter is reduced with the optical system of the simple constitution, such as mirror.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drum scanning type scanning optical device (for example, an image recording device).

[Prior Art] As image recording devices that record color images by scanning light onto a photoreceptor, there are known polygon scanning type devices and drum scanning type devices.

In the former method, the light beam from the light source is reflected and deflected by a polygon mirror that rotates at high speed, and the light beam is scanned over the irradiated object to perform a specified task. Although it is quick to perform tasks such as recording, it has the disadvantage that if you try to reduce the beam spot diameter on the object to be irradiated, the optical system for guiding the light beam onto the object becomes multi-fiber.

[Invention or problem to be solved] On the other hand, the drum scanning type described later can form a small spot diameter on a rotating drum using a relatively simple optical system, but the drum can be moved at a higher speed as the left. It had the disadvantage that recording and other tasks were slow because it could not be rotated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a drum scanning type scanning optical device having a configuration capable of recording color images at high speed and high resolution in order to solve the above-mentioned drawbacks.

[Means for Solving the Problems] In order to achieve the above object, the scanning optical device according to the present invention has a cylindrical shape, and the inner surface is the surface of the object to be irradiated such as a photosensitive surface. a rotating drum that rotates in a direction, and at least a mirror that is located inside the rotating drum and rotates in a second direction (for example, a direction opposite to the first direction) about the central axis of the cylindrical shape of the rotating drum. An optical system is provided, in which a beam of light emitted from a light source and guided substantially parallel to the central axis is reflected by the mirror and condensed while being scanned onto the surface of the irradiated object.

The above-mentioned mirror may be a curved mirror such as a paraboloid of revolution, or a plane mirror. In the latter case, the light flux passes through the imaging optical system, is reflected by the plane mirror, and is focused onto the object to be irradiated. be done.

If the imaging optical system included in the above optical system is an achromatic imaging optical system, the mirror does not generate chromatic aberration, so the optical system focuses light beams of multiple wavelengths onto the same point on the surface of the irradiated object. be able to.

Further, at least one of the rotating drum and the optical system is moved in a direction parallel to the central axis, but even faster scanning is possible if both are moved in opposite directions.

[Function] Although the above configuration is of a drum scanning type, high-speed scanning is possible because the rotating drum and the optical system are rotated about the same rotation center axis.

In addition, since the optical system uses mirrors without chromatic aberration, it is possible to focus light beams of multiple wavelengths on the same point on the surface of the irradiated object. and high resolution can be achieved.

[Embodiment] FIG. 1 shows a first embodiment of the present invention. In the same figure, 1
2 is a cylindrical rotating drum whose inner surface is a photoreceptor.
3 is a rotational center axis around which the rotating drum 1 is rotated by a rotation drive device (not shown); 3 is a mirror rotation axis coaxial with the central axis 2 of the rotating drum 1; 4 is a paraboloid-shaped mirror of rotation. It is attached to the mirror rotation shaft 3 and rotated about this by a rotation drive device (not shown). Rotation direction of rotating drum 1 (arrow A) and rotation direction of rotating parabolic mirror 4 (arrow E)] B
) are in opposite directions.

Further, the rotating drum 1 and the mirror rotating shaft 3 are movable in directions perpendicular to the rotation direction (main scanning direction) (sub-scanning direction, indicated by arrows C and D, respectively) and in opposite directions.

In the first embodiment, light beams of three wavelengths E1, λ2, and E3 emitted from a light source such as a semiconductor laser that is modulated and driven based on color image information are converted into parallel light and are directed to a parabolic mirror 4. The incident beam is reflected by the mirror 4 and is focused on the same point on the inner surface of the rotating drum. In this case, since the central axis of rotation of the paraboloid of revolution of the parabolic mirror 4 is aligned with the generatrix of the cylindrical shape of the inner surface of the photoreceptor of the rotating drum 1, the axis of rotation is parallel to the axis of rotation of the parabolic mirror 4. A focal point, which is a condensing point for the light, exists on the inner surface of the photoreceptor, and three types of beams are condensed to the same point as described above.

Since the reflective parabolic mirror 4 is used, wavelength-dependent chromatic aberration does not occur, and the three types of parallel beams are focused on a focal point located on the inner surface of the rotating drum 1, which is independent of the wavelength.

Furthermore, regarding scanning in the main scanning direction and scanning in the sub-scanning direction, the rotating drum 1 and the parabolic mirror 4 rotate or move in opposite directions, so that images can be recorded at high speed on the photoreceptor on the inner surface of the rotating drum 1. It will be done.

In this way, by using the scanning optical system of this embodiment, a high-speed, high-resolution image recording apparatus capable of color printing can be realized with a simple configuration.

Next, a second embodiment will be described with reference to FIG. In the second embodiment, instead of the parabolic mirror 4 of the first embodiment, a mo-plane mirror 14, an achromatic imaging optical system 15, and these members 14 are used.
．． An optical system holding means 16 is provided which holds the optical system 15 integrally and is attached to the mirror rotation shaft 3.

Wavelengths modulated based on color image information E1, N2,
The parallel beam of λ3 passes through the achromatic imaging optical system 15 and is reflected by the plane mirror 14 which rotates at an angle of 45 degrees with respect to the mirror rotation axis 3, so that the optical axis is parallel to the mirror rotation axis 3. An image is formed on the photoreceptor on the inner surface of the rotating drum l, which is placed at the set focal position of the achromatic imaging optical system 15. Achromatic imaging optical system 15 It is designed so that there is little chromatic aberration for the light of wavelengths 1, 2+'A, and 3. Spots can be formed.

The other points are the same as the first embodiment, and a high-speed, high-resolution scanning system capable of color matching can be realized with a simple configuration.

The following materials can be used for the photoreceptor of the rotating drum 1 in the above embodiments.

Photoconductive materials for electrophotography (e.g., S, ZnO1c, s
,cdsa,z,slz,,s.

B, 20. , T, 0□, S, organic photoconductive materials such as polyvinylcarbazole, polyvinylpyrene, polyvinylanthracene), silver salt photosensitive materials (for example, microcrystalline particles of silver halide in gelatin); Dispersed wet silver salt photosensitive material, silver halide/silver behenate,
There are dry-type silver salt photosensitive materials whose main ingredients are non-photosensitive organic silver salts such as silver benzotriazole and reducing agents.

[Effects of the Invention] As explained below, the scanning optical device of the present invention is capable of high-speed scanning compared to the conventional drum scanning type, and has a higher scanning speed than the conventional polygon scanning type. The optical system has a simple configuration and the spot diameter is small (possible).

Therefore, it is effective in increasing the speed, resolution, and cost of color-compatible image recording devices and the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment of the invention, and FIG. 2 is a diagram showing a second embodiment of the invention. 1...Rotating drum, 2...Center shaft, 3...
... Mirror rotation axis, 4... Parabolic mirror 14.
...Flat mirror 15...Achromatic imaging optical system,
16...Optical system holding means Applicant: Canon Co., Ltd.

Claims (1)

[Claims] 1. A rotating drum having a cylindrical shape and whose inner surface is the surface of the irradiated object and rotating in a first direction about the central axis of the cylindrical shape, and a rotating drum located inside the rotating drum. and an optical system including at least a mirror that rotates in a second direction about the central axis of the cylindrical shape, and a light beam emitted from the light source and guided approximately parallel to the central axis is reflected by the mirror and is reflected by the mirror. A drum-scanning type scanning optical device that focuses light onto the surface of the irradiator. 2. The scanning optical device according to claim 1, wherein the mirror is a paraboloid of revolution mirror, and the focal point thereof is always on the surface of the object to be irradiated. 3. The mirror is a plane mirror that rotates at an angle of 45 degrees with respect to the central axis, and the optical system includes the plane mirror and an imaging optical system whose focal point is set on the surface of the irradiated object. A scanning optical device according to claim 1. 4. The scanning optical device according to claim 3, wherein the imaging optical system is an achromatic optical system and focuses light beams of a plurality of wavelengths onto the same position on the surface of the object to be irradiated. 5. The scanning optical device according to claim 1, wherein at least one of the rotating drum and the optical system is moved in a direction parallel to the central axis. 6. The scanning optical device according to claim 1, wherein the surface of the object to be irradiated is a photosensitive surface of an image recording device.