Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2000-04-27
2003-02-11
Spyrou, Cassandra (Department: 2872)
Optical waveguides
With optical coupler
Input/output coupler
C385S085000, C385S089000, C385S124000, C347S225000
Reexamination Certificate
active
06519387
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image recording device and to an optical fiber, and in particular, to an image recording device which records an image onto a recording medium by main scanning and subscanning a light beam onto the recording medium by relatively moving the light beam and the recording medium, and to an optical fiber used in the image recording device.
2. Description of the Related Art
Conventional image recording devices have been known in which a laser beam outputted from a light source such as a laser is inputted to an optical fiber. The light emitted from the optical fiber is collected by a lens. While a drum, on whose outer peripheral surface a recording medium is set, is rotated in a main scanning direction, the collected light beam is scanned in the subscanning direction which is orthogonal to the main scanning direction. In this way, the image is recorded onto the recording medium which is disposed at the focal point position of the lens. For example, WO 97/27065 discloses an image recording device in which light emitted from an optical fiber array, to which infrared lasers are inputted, is focused on a drum by a telecentric lens optical system, so as to record an image. In these image recording devices, a usual optical fiber having a core/clad structure having a core of a circular cross-sectional configuration is used. The profile of the light emitted from an optical fiber having a core of a circular cross-sectional configuration is circular, and the spot configuration of the beam scanned on the recording material is also circular.
However, by carrying out exposure at a high illumination intensity and in a short time, in order to reduce the energy used for exposure, it is preferable for the spot configuration of the scanned beam to be, rather than circular, short in the main scanning direction.
Further, by making the light intensity substantially constant in the widthwise direction, variations in the widths of the written lines, which variations are caused by variations in the amount of light, can be suppressed. A stable, good image can thereby be obtained. Therefore, it is preferable that the spot configuration of the scanned beam is rectangular or the like, rather than circular.
A scanned beam spot having an elongated configuration or a rectangular configuration can be obtained by using as a light source a broad-area-type semiconductor laser (with which the profile of the emitted light is an elongated configuration or a rectangular configuration). A broad-area-type semiconductor laser is high output, and is effective for applications requiring a high output light source, such as the recording of images onto a heat-mode-type photosensitive recording material. However, because the light source is high output, much heat is generated. In cases in which light sources are disposed in an array, cooling thereof is difficult. Further, when a semiconductor laser is built-in into the optical unit of an image recording device as the output source of the scanning beam, a problem arises in that, when the semiconductor laser malfunctions, it is troublesome to replace the semiconductor laser with a new one.
Japanese Patent Application Laid-Open (JP-A) No. 7-276701 discloses an image recording device which carries out recording by laser light outputted from an optical fiber which is formed such that the output end portion thereof is shaped to have a flat surface in the vertical direction. The object of the invention of JP-A-7-276701 is to obtain pixels having no convexities nor concavities, by forming the optical fiber to have a flat surface in the vertical direction at the output end portion of the optical fiber. However, the drawings of JP-A-7-276701 only illustrate an optical fiber having an external configuration in which a circular-tube-shaped fiber is flattened midway along the fiber, and JP-A-7-276701 does not clearly disclose the material, refractive index, or structure of the optical fiber. Thus, it can only be concluded that this device utilizes a single-composition optical fiber having a uniform refractive index. With such an optical fiber, there are the problems that the light propagation loss is great and the efficiency of utilizing the light beam is markedly low. Further, an optical fiber whose shape is flattened midway along the fiber has the problem that production thereof is difficult because the produceability and reproducibility of the optical fibers is poor.
As described above, it has until now not been possible to realize an image recording device which can obtain a beam spot having an elongated configuration in the subscanning direction or a beam spot having a rectangular configuration by using an optical fiber.
SUMMARY OF THE INVENTION
The present invention was developed in consideration of the above-discussed problems with conventional image recording devices, and an object of the present invention is to provide an image recording device in which a beam spot of a configuration which extends in an elongated manner in the subscanning direction or a beam spot of a rectangular configuration can be obtained, and which can be suitably used in recording onto heat-mode-type photosensitive recording materials. Further, another object of the present invention is to provide an image recording device in which, even if the amount of light or the sensitivity of the recording material or the like varies, a stable, good image can be obtained, and which has a low propagation loss, can be manufactured easily, and is practical.
The present inventors conducted experiments in order to overcome the above-discussed problems, and as a result, overcame the above problems by the following means.
A first aspect of the present invention is an image recording device for recording an image on a recording medium by main scanning and subscanning a light beam with respect to the recording medium by relatively moving the light beam and the recording medium, comprising a light source which emits a laser beam which has been modulated in accordance with image data; an optical fiber having a core, a clad covering the core, a light exit portion, and a light entry portion optically joined to the light source, which receives the laser beam into the optical fiber, the core having a cross-sectional configuration in a plane substantially orthogonal to an optical axis direction of the laser beam corresponding to at least one of an elongated configuration and a configuration having two parallel sides at least at the light exit portion of the optical fiber; and a focusing lens which focuses, on the recording medium, a light beam emitted from the light exit portion of the optical fiber.
A second aspect of the present invention is the image recording device of the first aspect, wherein the focusing lens focuses the laser beam on the recording medium such that a configuration of the laser beam on the recording medium is the elongated configuration and the elongated configuration includes a short dimension oriented in a direction coinciding with a direction in which the main scanning is conducted.
A third aspect of the present invention is the image recording device any one of the first aspect and the second aspect, wherein the cross-section of the core is the elongated configuration and the elongated configuration includes a short dimension oriented in a direction coinciding with a direction in which the main scanning is conducted.
A fourth aspect of the present invention is the image recording device of the first aspect, wherein the cross-section of the core is configuration having two parallel sides, and the focusing lens focuses the laser beam on the recording medium such that a light intensity of the light beam emitted from the light exit portion of the optical fiber is substantially same at least one of in a direction in which the main scanning is conducted and in a direction in which the sub scanning is conducted.
A fifth aspect of the present invention is the image recording device any one of the first to forth aspects, wherein t
Sunagawa Hiroshi
Umemura Shizuo
Assaf Fayez
Fuji Photo Film Co. , Ltd.
Spyrou Cassandra
Sughrue & Mion, PLLC
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