JPH0672980B2 - Optical scanning device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an optical scanning device which scans a laser beam or the like by rotating a mirror.

BACKGROUND OF THE INVENTION In general, an image recording apparatus modulates laser light oscillated from a laser oscillator with a modulator such as an acousto-optic modulator (AOM), and modulates the modulated laser light into light from a galber mirror or a rotating polygon mirror. It is deflected in the main scanning direction by the scanning device, and an image is formed on the recording member via an imaging lens such as an fθ lens.

[Problems of Background Art] A galver mirror as an optical scanning device deflects laser light by rotating the mirror back and forth.

Since the galber mirror deflects the laser light using only one surface of the mirror, it is easy to correct the surface tilt error of the mirror, and there is an advantage that the optical scanning device can be made small, lightweight and inexpensive.

However, on the other hand, since the mirror is reciprocally rotated to deflect the laser light, the scanning cycle is slow, and as the scanning cycle increases, the inertia and the air resistance received on the mirror surface increase, which imposes a burden on the mirror drive section, and therefore the scanning cycle naturally occurs. You will be limited.

Further, during reciprocating rotation, air resistance causes dust to adhere to both ends of the mirror surface, which affects the reflectance.

Therefore, recently, in order to speed up the scanning cycle, a rotary polygon mirror is used instead of the galver mirror.

The rotary polygonal mirror is formed into a right-angled prism whose end face is flat and has a regular polygonal shape, and the side face serves as a reflecting surface, which deflects the laser light as it rotates.

However, it is necessary to correct the surface tilt error of each reflecting surface of the rotating polygon mirror, and to set the optical system such as a cylindrical lens in order to correct the surface tilt error, or to enter the reflecting surface of the rotating polygon mirror. A correction means or the like for correcting the incident angle of the laser light for each reflecting surface is required.

In addition, as in the case of the galber mirror, due to the air resistance received by each reflecting surface, dust adheres to both ends of each reflecting surface or both ends are damaged, which affects scanning, and the rotating polygon mirror itself. Has a problem that it is heavy, difficult to handle, and expensive.

[Object of the Invention] An object of the present invention is to provide an optical scanning device capable of performing stable scanning while reducing the air resistance received on the anti-slope during rotation, enabling high-speed rotation.

SUMMARY OF THE INVENTION The present invention is a cylindrical optical member having a rotation axis substantially at the center of a circle, wherein a reflective layer is provided on a cross section parallel to the rotation axis of the optical member and along the diameter of the circle. The present invention provides an optical scanning device, characterized in that the reflective layer is a reflective layer that uses a total reflection effect with a small interval.

[Embodiment of the Invention] FIG. 1 is a schematic view illustrating an example of a manufacturing process of a conventional optical scanning device.

As shown in FIG. 1A, a cylindrical transparent optical member 1 is cut along a diameter 2.

Then, as shown in FIG. 1 (b), at least one cut surface of the optical members 3 and 4 cut into two is vapor-deposited with a reflective material such that all laser light incident on the cut surface is reflected,
Alternatively, by attaching a reflective thin film sheet to the reflective layer 5
To form.

Then, as shown in FIG. 1C, the optical scanning devices 6 having the reflective layer 5 therein are formed by aligning the cut surfaces of the optical members 3 and 4, respectively.

In this way, the optical scanning device 6 is rotated in one direction by the rotating shaft provided at the center of the circle, so that the optical scanning device 6 has a columnar shape as compared with a rotating polygon mirror or the like. The scanning device 6 can be rotated at a high speed without being affected by the air resistance, and further, stable scanning can be performed without dust and the like being attached.

FIG. 2 is a block diagram showing an example of an image recording apparatus using the optical scanning device 6.

In the figure, 6 is the optical scanning device described in FIG. 1, 11 is a drive unit for driving the optical scanning device 6, 12 is a semiconductor laser oscillator, 13 and 14 are cylindrical lenses, 15 is an imaging lens such as an fθ lens, Reference numeral 16 is a mirror, and 17 is a recording member.

The case where a semiconductor laser is used as the laser light source will be described, but a gas laser or the like may be used. However, in this case, an acousto-optic modulator (AOM) and an optical system for beam shape shaping are required as appropriate.

Laser light oscillated from the semiconductor laser oscillator 12 enters the optical scanning device 6 via the cylindrical lenses 13 and 14.

The laser light passes through the optical member of the optical scanning device 6 and is reflected by the reflection layer 5.
Reflect on. Then, the laser light forms an image on the recording member 17 via the imaging lens 15 and the mirror 16.

3 (a) and 3 (b) are a plan view and a side view showing a beam cross-sectional shape (hatched portion in the drawing) in the image recording apparatus shown in FIG. For the sake of explanation, the drawing after the reflective layer 5 is shown in a linear development.

In the plan view of FIG. 3 (a), a semiconductor laser oscillator
Laser light emitted from 12 with a predetermined spread angle enters a cylindrical lens 13.

However, since it can be considered that the cylindrical lens 13 does not act as a lens at all, the laser beam goes straight as it is, diverges by the cylindrical lens 14, and enters the side surface of the optical scanning device 6.

Since the optical scanning device 6 is composed of a cylindrical optical member, it functions as a kind of cylindrical lens and is deflected by the optical scanning device 6 as parallel laser light.

After that, the laser light has a circular cross section and is imaged on the recording member 17 by the imaging lens 15.

Further, in the side view of FIG. 3B, the laser light oscillated from the semiconductor laser oscillator 12 becomes parallel laser light by the cylindrical lens 13 and enters the optical scanning device 6 via the cylindrical lens 14.

Cylindrical lens 14 and optical scanning device 6 on the side surface
Does not act as a lens at all, the laser light is incident on the imaging lens 15 while being parallel and is imaged on the recording member 17.

In FIG. 3, the cross-sectional shape of the laser light emitted from the optical scanning device 6 is circular, but if the laser light emitted from the optical scanning device 6 is parallel light, the cross-sectional shape of the laser light may be arbitrary. You can

Thereby, the cross-sectional shape of the laser beam on the recording member 17 can be arbitrarily changed by appropriately passing the optical system.

Next, an embodiment of the optical scanning device according to the present invention will be described with reference to FIG. 4 showing an example of the manufacturing process thereof.

As shown in FIG. 4A, the cylindrical optical member 1 is cut along the diameter 2.

Then, as shown in FIG. 4 (b), the spacer 7 having a thickness p formed in a frame shape to have a predetermined space is sandwiched by the cut surfaces of the transparent optical members 3 and 4 which are cut into two, and they are matched with each other. To do.

Thus, as shown in FIG. 4C, the spacer 7 having the thickness p is formed.
The cut surfaces of the optical members 3 and 4 separated by are used as the reflection layer 8.

The reflection layer 8 of the optical scanning device 9 deflects laser light by utilizing the total reflection effect of light.

That is, if the critical angle in the reflective layer 8 is θ ₂ ,
When the angle of incidence on the reflective layer 8 of the laser beam D as shown in FIG. (A) is _{0~θ 1 (θ 1 <θ 2} ), the laser beam D passes through the reflective layer 8, 5 ( As shown in b), when the incident angle of the laser beam D on the reflective layer 8 is θ ₂ or more, the laser beam D is totally reflected by the reflective layer 8.

The critical angle is changed by appropriately changing the substance (air in the above example) that forms the interval of the thickness p formed on the spacer 7.

As a result, in the case of the optical scanning device 6 of FIG. 1 in which the reflective layer 5 is formed by depositing a reflective material or attaching a reflective thin film as shown in FIG. On the other hand, since the origin detector 25 which detects the writing timing of the image is scanned by the irradiation of the laser light, the actual scanning length becomes longer than the scanning length L, and the imaging lens 15 has the diameter l ₁ which allows the scanning. It becomes a lens.

On the other hand, by using the optical scanning device 9 shown in FIG. 4, when the incident angle of the laser light D on the reflective layer 8 is equal to or less than the critical angle as shown in FIG. The origin detector 25 is arranged at a position where the laser beam D passes through 7, and when the origin detector 25 is no longer irradiated with the laser beam D due to total reflection and the writing timing is measured, the imaging lens 26 scans the origin. Since a lens having a diameter l ₂ (<l ₁ ) that allows the above is sufficient, the entire optical system can be downsized.

It should be noted that the spacer 7 may have a cover-like shape that covers the minute gap instead of the spacer as long as it can prevent dust from adhering within the minute gap provided for total reflection.

Next, another manufacturing process of the optical scanning device of FIGS. 1 and 4 described above will be described with reference to FIG.

In the cylindrical optical member 1 as shown in FIG. 7 (a), cuts 20 having a distance m along the diameter 2 of the circle are made as shown in FIG. 7 (b).

Then, as shown in FIG. 7 (c), if the notch 20 is filled with a reflective material to form a reflective layer 21, an optical scanning device 22 similar to the optical scanning device 6 shown in FIG. 1 is formed. can do.

Further, by inserting a spacer 23 into the notch 20 as shown in FIG. 7D, the optical scanning device 9 described in FIG.
An optical scanning device 24 similar to can be formed.

[Advantages of the Invention] As described above, the optical scanning device of the present invention includes (1). By forming the reflective layer on the cross section of the cylindrical transparent optical member along the diameter of the circle, it is possible to rotate at high speed because it does not receive air resistance during rotation.

(2). Since it is possible to prevent dust or the like from directly adhering to the reflecting surface, it is possible to maintain the reflectance.

(3). Since the number of reflecting surfaces is smaller than that of the rotary polygon mirror, it is possible to easily correct an error due to surface tilt.

(4). The imaging lenses used in combination can be downsized, and the entire optical system can be made compact.

(5). The sea angle can be changed according to the substance forming the minute interval.

And so on.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a manufacturing process of a conventional optical scanning device, FIG. 2 is an external view showing an example of an image processing device using the optical scanning device of the present invention, and FIG. Explanatory drawing, 4th
5 and 7 are schematic views showing another manufacturing method of the present invention, and FIG.
6 and 6 are explanatory views of FIG.

Claims (1)

[Claims] 1. A cylindrical optical member having a rotation axis substantially at the center of a circle, which is parallel to the rotation axis of the optical member, and
An optical scanning device, wherein a reflection layer is formed on a cross section along a diameter of a circle, and the reflection layer is a reflection layer which utilizes a total reflection effect with a minute interval.