JPH06171140A - Laser beam irradiating mechanism of thermal recorder - Google Patents

Abstract

PURPOSE:To surely perform gradation with a simple constitution and without directly modulating a laser oscillating source. CONSTITUTION:A laser beam inadiating mechanism is provided, with a YAG laser 16 which outputs a laser beam L, an ftheta lens 18 which condenses the laser beam L on a heat-sensitive recording material S, and a beam diameter adjusting device 20 which is situated between the YAG laser 16 and the ftheta lens 18 and is capable of changing the beam diameter of the laser beam L to be condensed on the heatsensitive recording material S. The laser beam diameter adjusting device 20 includes a second lens 30, a holder 32 on which the second lens 30 is attached, and an actuator, for example, a laminate type piezoelectric element 34, which moves the holder 32 back and forth along the light path of the laser beam L.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam irradiation mechanism of a thermal recording apparatus for irradiating a thermal recording material with a laser beam to record a gradation image or the like.

[0002]

2. Description of the Related Art Thermal recording apparatuses for imparting thermal energy to a thermal recording material to record an image or the like have been widely used. In particular, there has been proposed one that enables high-speed recording by using a laser as a heat source (Japanese Patent Laid-Open No. 50-23617).
JP-A-58-94494 and JP-A-62-7798.
3 and JP-A-62-78964).

The present applicant has applied a color developing agent, a color developing agent and a light absorbing dye on a support as a heat sensitive recording material which is applied to such a thermal recording apparatus and is capable of recording a good image with high quality. In preparation, a material that develops a color at a concentration according to the applied heat energy has been developed and a patent application has been filed (Japanese Patent Application No. 3-
62682, Japanese Patent Application No. 3-187494).

In this heat-sensitive recording material, microcapsules containing at least a basic dye precursor, a color developer and a light-absorbing dye are dissolved in an organic solvent which is hardly soluble or insoluble in water and then emulsified and dispersed. And a heat-sensitive layer formed by applying a coating liquid containing the emulsion.

By the way, when recording a gradation image or the like on such a heat-sensitive recording material, the laser oscillation source constituting the laser beam irradiation mechanism is directly modulated, or an external modulator such as an acousto-optic modulator (AOM) is used. A method of gradation by changing the laser power applied to the thermosensitive recording material can be considered.

[0006]

However, since this type of heat-sensitive recording material has low sensitivity, a relatively large laser power is required for recording an image or the like. Therefore, in the method of directly modulating the laser oscillation source as described above, a current of several A must be controlled at high speed, and this control becomes considerably complicated and difficult. On the other hand, in the method using AOM or the like, it is necessary to endure thermal damage by a laser beam having a large power, and such an AOM becomes very expensive.

The present invention solves this kind of problem and irradiates a laser beam of a thermal recording apparatus capable of surely performing gradation with a simple structure without directly modulating the laser oscillation source. The purpose is to provide a mechanism.

[0008]

In order to achieve the above object, the present invention irradiates a heat sensitive recording material with a laser beam to impart a predetermined heat energy to the heat sensitive recording material to record an image or the like. A laser beam irradiation mechanism of a thermal recording device, comprising: a laser oscillation source that outputs the laser beam; a focusing optical system that focuses the laser beam on the thermal recording material; the laser oscillation source and the focusing optical system. And a beam diameter adjusting means that is arranged between the system and the beam diameter adjusting means for changing the beam diameter of the laser beam focused on the thermosensitive recording material.

Further, the beam diameter adjusting means may be provided with an optical system which is arranged on the optical path of the laser beam and is movable back and forth along the optical path direction under the action of an actuator.

Furthermore, the beam diameter adjusting means may be provided with a light shielding member which can advance and retreat with respect to the optical path of the laser beam.

[0011]

In the laser beam irradiation mechanism of the thermal recording apparatus according to the present invention, the laser beam output from the laser oscillation source is
By condensing on the thermosensitive recording material via the condensing optical system, predetermined heat energy is applied to the thermosensitive recording material to record an image or the like. At that time, when the beam diameter adjusting means is driven to change the beam diameter of the laser beam focused on the thermosensitive recording material, the density of the thermosensitive recording material is changed. With this, it is possible to easily perform gradation while a constant laser power is output from the laser oscillation source.

Further, as the beam diameter adjusting means, an optical system which can move back and forth along the optical path direction can be provided.
By displacing this optical system to separate the focal position of the laser beam from the heat-sensitive recording material, the beam diameter of the laser beam on the heat-sensitive recording material becomes large.

Further, as the beam diameter adjusting means, it is possible to provide a light-shielding member which can advance and retreat with respect to the optical path. By displacing the light-shielding member to cut off a part of the laser beam, the heat-sensitive recording material can be formed. The beam diameter of the laser beam becomes large.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser beam irradiation mechanism of a thermal recording apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a thermal recording apparatus. The thermal recording apparatus 10 irradiates the thermal recording material S with a laser beam L in the main scanning direction (direction of arrow A) to obtain the thermal recording material. The laser beam irradiation mechanism 12 according to the first embodiment for applying a predetermined thermal energy to S to record an image and the like, and the thermal recording material S in a sub-scanning direction (arrow shown in FIG. 1) substantially orthogonal to the main scanning direction. And a sub-scanning transport mechanism 14 for transporting in the B direction).

The laser beam irradiation mechanism 12 includes a YAG laser (laser oscillation source) 16 which outputs a laser beam L,
Fθ that focuses this laser beam L on the thermal recording material S
A lens (condensing optical system) 18 and a beam diameter adjusting means 20 arranged between the YAG laser 16 and the fθ lens 18 and capable of changing the beam diameter of the laser beam L focused on the thermosensitive recording material S. With.

On the output side of the YAG laser 16, a collimator lens 22 for collimating the laser beam L, a first lens 28 and a second lens 30 (optical system) constituting a beam expander 26 are arranged. It The beam diameter adjusting means 20 includes the second lens 30 and the second lens 30.
A holder 32 to which is fixed, and an actuator for moving the holder 32 back and forth along the optical path direction of the laser beam L,
For example, the laminated piezoelectric element 34 is provided. The reflection mirror 36, the cylindrical lens 24, the polygon mirror 38 for deflecting the laser beam L, the fθ lens 18, and the cylindrical lens 24 cooperate with each other on the downstream side of the second lens 30 in the optical path direction. A cylindrical mirror 40 that corrects the surface tilt of 38 is arranged.

The sub-scan transport mechanism 14 comprises a motor 42 and a transport roller 44 connected to the motor 42 for transporting the thermal recording material S in the sub-scan direction in the direction of arrow B.

The YAG laser 16, the piezoelectric element 34, the polygon mirror 38, and the motor 42 are driven and controlled by the controller 46.

Next, the operation of the laser beam irradiation mechanism 12 according to the first embodiment will be described in relation to the thermal recording device 10.

First, when the motor 42 constituting the sub-scanning transport mechanism 14 is driven via the controller 46, the transport roller 44 connected to this motor 42 rotates in the direction of the arrow,
The thermal recording material S is conveyed in the direction of arrow B. On the other hand, the YAG laser 16 is driven via the control unit 46, and the YA
When the laser beam L is output from the G laser 16, the laser beam L is collimated by the collimator lens 22 and then introduced into the beam expander 26 to expand the beam diameter. Further, the laser beam L guided to the polygon mirror 38 through the reflection mirror 36 and the cylindrical lens 24 is reflected by the reflection surface of the polygon mirror 38 because the polygon mirror 38 is rotated at a high speed in the arrow direction, and then the fθ lens. 18 and the cylindrical mirror 40 to guide the heat-sensitive recording material S to the arrow B.
The thermosensitive recording material S which is sub-scanned and conveyed in the main scanning direction is main-scanned in the direction of arrow A. As a result, predetermined heat energy is applied to the heat-sensitive recording material S to record an image or the like.

When gradation of an image or the like recorded on the heat-sensitive recording material S is performed, the piezoelectric element 34 constituting the beam diameter adjusting means 20 is driven and the second lens 30 is integrated with the holder 32. It is moved on the optical path of the laser beam L in a predetermined direction. Therefore, as shown in FIG. 2, the focus position of the laser beam L on the thermosensitive recording material S moves from the position F to the position F1 (see the laser beam L1), and the position of the beam waist is from the thermosensitive recording material S. The size of the spot on the thermal recording material S increases as the distance increases. Therefore, as shown in FIG. 3, the intensity of the laser beam L1 is reduced due to the enlargement of the spot size, the thermal energy applied to the thermal recording material S is reduced, and a gradation image is formed on the thermal recording material S. Etc. will be recorded. If the focal position of the laser beam L is moved to the position F2, the spot size on the heat-sensitive recording material S will be considerably large, and the heat-sensitive recording material S will not be heated to the threshold value necessary for color development. A non-printed portion can be formed (see laser beam L2 in FIGS. 2 and 3).

As described above, in the first embodiment, the YAG
The piezoelectric element 3 constituting the beam diameter adjusting means 20 in a state where the laser power output from the laser 16 is maintained constant.
Under the action of 4, the modulation can be performed only by moving the holder 32 and the second lens 30 integrally in the optical path direction.
As a result, it is possible to obtain a desired gradation image or the like reliably and easily with a simple structure, as compared with a conventional device that directly modulates a laser oscillation source.

Further, in the low density region, the thermal recording material S
The spot size above is larger. Therefore, there is an advantage that a smooth low density portion can be obtained as a whole.

Next, a laser beam irradiation mechanism 60 according to the second embodiment of the present invention will be described with reference to FIG. The laser beam irradiation mechanism 1 according to the first embodiment
The same components as those in 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

The beam diameter adjusting means 62 constituting the laser beam irradiation mechanism 60 is provided with a slit member (light shielding member) 64 which can advance and retreat with respect to the optical path of the laser beam L.
The slit member 64 is connected to an actuator (not shown) such as a cylinder.

In the laser beam irradiation mechanism 60 according to the second embodiment constructed as described above, when the slit member 64 is moved toward the optical path of the laser beam L (direction of arrow C) under the action of an actuator (not shown). A part of the laser beam L is eclipsed by the slit member 64. Therefore, the laser beam L is focused on the thermosensitive recording material S via the fθ lens 18 in a state where the laser beam L is partially eclipsed, and the spot size on the thermosensitive recording material S becomes large. As is well known, this is because the beam diameter of the laser beam L incident on the fθ lens 18 and the laser beam L focused on the thermal recording material S via the fθ lens 18.
This is because the spot size (focal diameter) of is inversely proportional to.

For this reason, the spot size on the heat-sensitive recording material S is increased by projecting the slit member 64 on the optical path, and the spot size on the heat-sensitive recording material S is larger than that when the slit member 64 is not projected. Power density is reduced. As a result, the thermal energy applied to the heat-sensitive recording material S is reduced, and a gradation image or the like is recorded on the heat-sensitive recording material S, and the laser beam irradiation mechanism 12 according to the first embodiment described above is used. It has the same effect.

In the second embodiment, the beam diameter adjusting means 62 is provided with the slit member 64 as a light shielding member. However, before the laser beam L is incident on the f.theta. The slit member 64 may be replaced with a diaphragm member or the like.

[0030]

According to the laser beam irradiation mechanism of the thermal recording apparatus of the present invention, the following effects and advantages can be obtained.

When the beam diameter of the laser beam focused on the thermosensitive recording material is changed under the driving action of the beam diameter adjusting means while the laser beam is being output from the laser oscillation source, the printing on the thermosensitive recording material is performed. A change in concentration is triggered. With this, it is possible to easily and surely perform gradation with a constant laser power output from the laser oscillation source, and it is possible to easily simplify the entire configuration, which is inexpensive.

Further, as the beam diameter adjusting means, it is possible to provide an optical diameter capable of moving forward and backward along the optical path direction,
By displacing the optical diameter to separate the focal position of the laser beam from the heat-sensitive recording material, the beam diameter of the laser beam on the heat-sensitive recording material increases.

Further, as the beam diameter adjusting means, it is possible to provide a light-shielding member which can advance and retreat with respect to the optical path. By displacing the light-shielding member to cut off a part of the laser beam, a light-sensitive recording material can be formed. The beam diameter of the laser beam becomes large.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a thermal recording apparatus incorporating a laser beam irradiation mechanism according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of changing a focal position by the laser beam irradiation mechanism.

FIG. 3 is a diagram showing the relationship between the spot size of a laser beam and the intensity of the laser beam.

FIG. 4 is a schematic configuration diagram of a laser beam irradiation mechanism according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Thermal recording device 12 ... Laser beam irradiation mechanism 14 ... Sub scanning conveyance mechanism 16 ... YAG laser 18 ... f.theta. Lens 20 ... Beam diameter adjusting means 28, 30 ... Lens 32 ... Holder 34 ... Piezoelectric element 60 ... Laser beam irradiation mechanism 62 ... Beam diameter adjusting means 64 ... Slit member

Claims (3)

[Claims] 1. A laser beam irradiation mechanism of a thermal recording device for irradiating a thermal recording material with a laser beam to impart a predetermined thermal energy to the thermal recording material to record an image or the like, the laser beam being output. A laser oscillating source, a condensing optical system for condensing the laser beam on the thermosensitive recording material, and arranged between the laser oscillating source and the condensing optical system,
A laser beam irradiation mechanism of a thermal recording apparatus, comprising: a beam diameter adjusting unit capable of changing a beam diameter of a laser beam focused on the thermal recording material. 2. The laser beam irradiation mechanism according to claim 1, wherein the beam diameter adjusting means is arranged on the optical path of the laser beam and is movable back and forth along the optical path direction under the action of an actuator. A laser beam irradiation mechanism of a thermal recording device, comprising: 3. The laser beam irradiating mechanism according to claim 1, wherein the beam diameter adjusting means comprises a light-shielding member capable of advancing and retracting with respect to the optical path of the laser beam. mechanism.