JPS63137206A - Laser optical system - Google Patents

Abstract

PURPOSE:To evade dew condensation and to perform fine image recording by constituting an optical deflector in a laser optical system which includes a laser light source, the optical deflector, a lens, etc., and providing a heating mechanism which heats a mirror surface for reflecting a laser beam. CONSTITUTION:The laser optical system 10 includes a housing 12 nearly in the shape of a rectangular prism where a swelling part is formed, and the semiconductor laser 24, a collimator lens 26, a rotary polygon mirror 30, an ftheta lens 40, and a mirror 42 are arranged in the housing 12. A heater 36 is fitted to a casing 32 where the polygonal mirror 30 is stored. A dew condensation deciding circuit 44 is fed with the detection signals of a temperature detecting means 38 and a humidity detecting means 46 and a switching circuit 50 is turned on and off according to the temperature in the housing 12 and humidity outside the housing body 12 to control current supply to the heater 36. Thus, the mirror surfaces constituting the polygon mirror 30 are prevented effectively from entering a dew condensation state and the fine image recording is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser optical system, and more particularly to a laser light source and an optical member provided on the optical path of a laser beam emitted from the laser light source, in particular a laser constituting a rotating polygon mirror. This relates to a laser optical system configured to prevent dew condensation from forming on the beam reflecting surface, thereby preventing uneven density in the image itself when recording an image on film, etc. using a laser beam. be.

2. Description of the Related Art Conventionally, laser beam scanning devices that scan a laser beam by deflecting it with an optical deflector have been widely employed, for example, in various image scanning recording devices, image scanning reading devices, and the like. In such a laser beam scanning device, a laser oscillator or a light source such as a semiconductor laser, an optical deflector such as a galvanometer mirror or a rotating polygon mirror, and optical components such as lenses and mirrors are installed in a housing that houses the optical system. It is common to incorporate

By the way, if dew condensation occurs on this type of optical component during a laser beam scanning operation or during non-operation, the optical component will be discolored in accordance with the shape of the condensation. Therefore,
When the laser beam is transmitted or reflected through this burnt area and scanning is attempted, the area interferes with the normal transmission or reflection of the laser beam, resulting in a significant decrease in the performance of the optical system and the loss of convergence. This causes problems such as the beam shape being distorted and image unevenness occurring. For example, in an optical system such as a laser printer that uses a rotating polygon mirror to deflect and scan a laser beam, the variation in reflectance between the plurality of mirror bodies that make up the rotating polygon mirror is suppressed to 0.2% or less. There is a need. That is, as a result of dew condensation and discoloration occurring on the mirror bodies, the reflectance of the laser beam by the plurality of mirror bodies becomes 0.
This is because if the variation exceeds 2%, density unevenness will occur in the displayed image. In particular, when transporting a light beam scanning device or bringing it indoors for storage, the optical system may be unpacked (sometimes condensation may occur due to atmospheric temperature differences inside and outside the optical housing). Moreover, once dew condensation occurs on an optical component, striped marks remain on the surface of the component after the dew dries, causing the same deterioration in optical performance as described above.

The present invention has been made in order to overcome the above-mentioned disadvantages, and in addition to arranging an optical system including various optical components inside a housing, the present invention prevents dew condensation on a rotating polygon mirror that is likely to cause density unevenness. By providing a means for transporting and storing the optical system, the optical deflector disposed on the optical path of the laser beam inside the optical system during installation, operation after installation, and non-operation. Avoid condensation,
The object of the present invention is to provide a laser optical system that enables precise image recording.

To achieve the above object, the present invention comprises a laser light source;
In laser optical systems including optical deflectors and lenses,
At least a heating mechanism is provided for heating the mirror surface of the optical deflector for reflecting the laser beam, and the generation of dew condensation on the mirror surface of the optical deflector is avoided under the biasing action of the heating mechanism. It is characterized by configuring.

Next, preferred embodiments of the laser optical system according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral lO indicates a laser optical system,
This laser optical system 10 includes a substantially rectangular parallelepiped optical housing 12 in which a bulge is formed. In fact, the optical housing 12 includes a casing 14, a casing 16 bulging outward from one side of the casing 14, and a casing 14.16.
The cover member 18 integrally closes the opening of the cover. A slit-shaped opening 20 is provided at the bottom of the casing 14 for guiding the scanned laser beam to the outside. As can be easily understood from FIG. 1, the casing 14 and the casing 16 are in communication.

Next, a semiconductor laser 24 is disposed inside the casing 16. A laser beam exit of the semiconductor laser 24 faces a collimator lens 26 attached to the casing 14. On the optical axis of the collimator lens 26 is an optical deflector, that is, a rotating polygon mirror 30 connected to a rotational drive source 28.
will be placed. In this case, the rotating polygon mirror 30 is housed in a cylindrical casing 32 made of aluminum. An opening 34 is provided in the side surface of the casing 32 for allowing the laser beam emitted from the semiconductor laser 24 to enter and exit the rotating polygon mirror 30 .

Here, a casing 32 surrounding the rotating polygon mirror 30
A bulging portion 33 defining a chamber communicating with the inside of the casing 32 is formed on a side surface of the casing 32 , and a heater 36 for heating the inside of the casing 32 is attached to the bulging portion 33 . In this case, the heater 36 can be of any type, and in some cases, a rubber heater that goes around the side surface of the casing 32 may be attached instead of the bulge 33. In addition,
Temperature detection means 38 for controlling the energization of the heater 36
is arranged near the casing 32 inside the optical housing 12.

On the other hand, the semiconductor laser 2 is centered around the rotating polygon mirror 30.
An fθ lens 40 is disposed in a direction perpendicular to 4. Furthermore, a mirror 42 is provided substantially parallel to the fθ lens 40 and inclined at 45 degrees with respect to the vertical direction. The mirror 42 faces the opening 20 of the casing 14. Although not shown in the above configuration, for example, an optical modulator and a cylindrical lens are arranged between the semiconductor laser 24 and the rotating polygon mirror 30, and an fθ lens 40
It is preferable to dispose a different cylindrical lens between the mirror 42 and the mirror 42, since this makes it possible to correct the tilt of the rotating polygon mirror 30.

Next, the heater 36 and the dew condensation determination circuit 44 for energizing the heater 36 will be schematically explained below.

As shown in FIG. 2, the output sides of the temperature detection means 38 and the humidity detection means 46 disposed at predetermined positions outside the optical housing 12 are connected to the input side of the dew condensation determination circuit 44.

The output side of the dew condensation determination circuit 44 is connected to a switching circuit 50 that turns the power bag 248 on and off. In addition,
The power supply device 48 is connected to the heater 36. The power supply device 48 is illustrated to supply a predetermined current to the dew condensation determination circuit 44 and the heater 36 when there is no power such as when the laser optical system 10 is being transported, or during a power outage after the laser optical system 10 is installed. No auxiliary battery is installed inside.

The laser optical system according to the present invention is basically constructed as described above, and its operation and effects will be explained next.

First, the general operation of the laser optical system 10 is as follows. That is, the laser beam derived from the semiconductor laser 24 is turned into a parallel beam by the collimator lens 26, and the rotating polygon mirror 3 rotates under the action of the rotation drive source 28.
0. Next, the laser beam is deflected by the rotating polygon mirror 30, and the fθ lens 40
The laser beam L passing through the θ lens 40 is converged so as to scan a plane at a constant speed. This focused laser beam is reflected by the mirror 42 and the aperture 20
It is led out to the outside via. At this time, although not shown,
A sheet such as a film is conveyed below the opening 20, and image information and the like are recorded by the laser beam L scanning the scanned surface of this sheet. become.

In the laser optical system work 0 that performs the above-described actions, the dew condensation prevention mechanism according to the present invention provides the following actions to the rotating polygon mirror 30. In other words, if a laser scanning device containing such a laser optical system is brought in from outdoors and unpacked indoors, condensation may occur if the temperature of the laser optical system is lower than the indoor atmospheric temperature. . In this case, condensation on the outside of the laser optical system does not affect the optical performance, but condensation on the optical components inside the laser optical system, especially on the rotating polygon mirror 30, will significantly degrade the optical performance and cause the convergent beam to This causes shape distortion, image unevenness, etc.

Furthermore, when installing the laser optical system, the optical housing 12)
Alternatively, the semiconductor laser 24, collimator lens 26, rotating polygon mirror 30, f
If condensation forms on the θ lens 40, etc., even if the lens 40 dries out, condensation marks such as discoloration will remain, and during the next operation, the same optical performance degradation as mentioned above will occur due to these condensation marks. cause. In this case, since it is necessary to suppress the variation in reflectance between the plurality of mirror bodies constituting the rotating polygon mirror 30 to 0.2% or less, it is particularly required to avoid the occurrence of dew condensation on the rotating polygon mirror 30. .

[Door-□, Therefore, in the present invention, even if the heater 36 attached to the casing 32 in which the rotating polygon mirror 30 is housed is installed before or after the installation of the laser optical system 1.0, As a result, the rotating polygon mirror 30
is kept at a constant temperature at all times. That is,
A temperature detection signal and a humidity detection signal are sent from the temperature detection means 38 and the humidity detection means 46 to the dew condensation determination circuit 44, respectively.

Therefore, the dew condensation determination circuit 44 determines the temperature inside the optical housing 12;
The switching circuit 5 corresponds to the humidity outside the optical housing 12.
0 and controls the current supply to the heater 36. For example, when the inside of the optical housing 12 is below a predetermined temperature, or when the outside of the optical housing 12 is above a predetermined humidity, the condensation determination circuit 44 energizes the heater 36 according to the correlation, The inside is heated,
As a result, the rotating polygon mirror 30 is heated. Generally, when the humidity rises, first the outside of the optical housing 12 rises, and then the humidity inside the optical mirror body 12 rises. For this reason, the humidity detection means 46 is disposed outside the optical housing 12, that is, the humidity detection means 46 detects the increase in humidity inside the optical housing 12.
This is properly detected in advance, and the rotating polygon mirror 30 is immediately heated. As a result, dew condensation on the mirror surface constituting the rotating polygon mirror 30 is effectively prevented. Therefore, the laser optical system 10 including the rotating polygon mirror 30 without condensation can scan the desired laser beam L to record or read the desired image.

As described above, the present invention effectively prevents dew condensation from forming on the rotating polygon mirror constituting the laser scanning device, although it has an extremely simple configuration. Therefore, the laser beam derived from the semiconductor laser is always scanned by the rotating polygon mirror whose reflection efficiency is within the permissible value, resulting in the effect that images can be effectively recorded or read. In other words, by avoiding dew condensation on the mirror surface of the rotating polygon mirror, it does not adversely affect the convergence and directionality of the laser beam, and prevents discoloration on the mirror surface of the rotating polygon mirror, resulting in uneven image density. Various effects can be obtained, such as being able to avoid.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
For example, instead of turning the heater on and off under the detection action of temperature detection means and humidity detection means, it is possible to keep the heater in the ON state at a predetermined temperature at all times, thereby omitting the detection means. Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a first embodiment of the laser optical system according to the present invention, and FIG. 2 is a block circuit diagram of a heating mechanism in the laser optical system according to the present invention.

Claims (4)

[Claims] (1) In a laser optical system including a laser light source, an optical deflector, a lens, etc., at least a heating mechanism for heating a mirror surface for reflecting a laser beam that constitutes the optical deflector is provided, and the heating mechanism 1. A laser optical system characterized in that the laser optical system is configured to avoid the formation of dew condensation on a mirror surface of an optical deflector under the biasing action of. (2) In the laser optical system according to claim 1, the heating mechanism includes a heater, and the heater is constantly energized or heated by a detection signal from at least one of the temperature detection means and the humidity detection means. A controlled laser optical system. (3) A laser optical system according to claim 1 or 2, wherein the heater is disposed inside a bulge that communicates with a casing that houses an optical deflector. (4) In the laser optical system according to claim 2 or 3, the laser light source, optical deflector, lens, etc. are arranged inside an optical housing, and the humidity detection means is arranged outside the optical housing. The laser optical system is installed in the