JPS6353513A - Optical deflector - Google Patents

Abstract

PURPOSE:To reduce the size, weight, cost, and power consumption of an optical deflector and, at the same time, to make high-speed scanning with the deflector, by deflecting light by using an oscillating type reflecting mirror and causing the deflected light to form an image on a recording section after it is reflected by a fixed reflecting mirror having a two-dimensionally curved reflecting surface. CONSTITUTION:An optical beam 3 from a light source 2 of a semiconductor laser, etc., is deflected by an oscillating type reflecting mirror 5 after it is condensed by an image forming lens system 4. The deflected optical beam 6 forms an image at one point on a recording section 1 after it is reflected by a fixed reflecting mirror 7 having a two-dimensionally curved reflecting surface and information is printed on the recording section 1. The oscillating type reflecting mirror 5 is constituted of an oscillating shaft 5a and plane mirror 5b which is fixed to the oscillating shaft 5a and makes oscillating motions around the shaft 5a. Concretely, for example, a galvano-mirror, resonating type reflecting mirror, etc., can be used as the plane mirror 5b. The oscillating shaft 5a of the galvano-mirror is mad of a rigid body and the plane mirror 5b is revolved by turning the whole shaft 5a by means of an electromagnetic driving means. The revolving angle can be changed optionally by means of instruction signals from the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical deflection device that scans a scanned medium while focusing a light beam on the medium, and particularly relates to an optical deflection device that scans a scanned medium while focusing a light beam on the medium. The present invention relates to an optical deflection device suitable for use in a recording/reproducing device or a laser printer.

[Conventional technology]

For example, in "Laser Research" Volume 11, No. 8 (August 1988), Sections 11 to 22, "Recent Laser Printer Technology J (R, A
, Sprague et al.),
A light beam from a light source is deflected by a rotating polygon mirror called a polygon mirror, and scanned over the recording section in a flat or linear manner.

Furthermore, when a light beam is deflected and scanned in a flat or linear manner, the distance from the light source of the light beam to the light beam irradiation point on the recording section differs depending on the deflection angle (because from the light source (This is because even if the distance to the deflection point of the light beam is the same, the distance from the deflection point to the light beam irradiation point on the recording section differs depending on the deflection angle.) Therefore, in this conventional technology, In order to ensure that the light beam is irradiated in the most converged state at any irradiation point, an fθ lens that can change the focal length of the light beam according to the deflection angle is used. is irradiated onto the recording section through the fθ lens.

Other related devices of this type include Japanese Patent Application Laid-open No. 32-135747.

[Problem that the invention seeks to solve]

The above conventional technology uses a polygon mirror, so it has the advantage that the return time of the light beam (the time from when the light beam finishes scanning a scanning line to when it starts scanning the next scanning line) is short. However, since the polygon mirror has a rotating part, there are inherently unstable factors such as friction and rolling, and shaft wobbling is likely to occur. Further, in order to reduce surface tilt (angular error of each mirror surface with respect to the rotational axis direction), the polygon mirror itself needs to have high processing accuracy, and is therefore expensive. Furthermore, the size of the polygon mirror itself is quite large (about 5cI11 in diameter), and to rotate it at high speed, a motor of about the same size is required. In order to rotate at ,
In either case, it will be more expensive.

Furthermore, when trying to increase the scanning speed as described above, it becomes impossible to obtain a large deflection angle, so in order to obtain a predetermined scanning width (i.e., the length of the scanning line), it is necessary to change the deflection point of the light beam. It is necessary to take a long distance from the recording section to the light beam irradiation point on the recording section, which poses a problem in that the overall size of the apparatus increases.

Furthermore, the fθ lens used in this prior art also has a complicated lens surface shape in order to perform the above-mentioned function, so it is not easy to design and manufacture, and is therefore expensive.・There is also the problem that it is difficult to reduce the weight.

The purpose of the present invention is to solve the problems of the prior art described above,
It is an object of the present invention to provide an optical deflection device that is small, lightweight, inexpensive, consumes little power, and is capable of high-speed scanning.

[Means for solving problems]

In order to achieve the above object, the present invention deflects a light beam from a light source using a galvanometer mirror or an oscillating reflector such as a resonant reflector, and a two-dimensionally curved reflecting surface. The configuration is such that the image is formed on the recording section after being reflected by a fixed reflecting mirror.

Here, the two-dimensional curved surface mentioned above is a curved line (for example,
A curved surface formed by the locus of a curved line when the curved line is moved along a direction perpendicular to a plane containing circular arcs, high-order curves, etc.

[Effect]

In the optical deflection device according to the present invention, the above-mentioned oscillating reflecting mirror has a plane mirror fixed on the oscillating axis. For example, in a resonant reflecting mirror, the oscillating axis is supported elastically and electromagnetically Driven. Therefore, unlike conventional devices, there are no unstable factors such as friction and rolling caused by rotation, and shaft wobbling does not occur. Also, since it is not a polygonal mirror, there is less surface tilting and optical axis tilting caused by processing and assembly accuracy. Also,
In the fixed reflecting mirror, for example, a first focal point of each ellipse is a reflection point of the swinging reflecting mirror, and a second focal point of each ellipse is a different arbitrary irradiation point on the recording section. , and since a group of ellipses with the same major axis length is prepared, and the surface along one envelope of the ellipse group is used as a reflective surface, even if the light beam is deflected, the light source and the recording unit will not be connected to each other. optical distance does not change.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a perspective view schematically showing an embodiment in which the present invention is applied to a laser printer.

In FIG. 1, 1 is a recording section, 1b is a scanning line on the recording section 1, 2 is a light source, 3 is a light beam from the light source 2, 4 is an imaging lens system, 5 is an oscillating reflector, and 5a is a 5b is a plane mirror, 6 is a deflected light beam, and 7 is a fixed reflecting mirror. In this embodiment, a photosensitive drum is used as the recording section 1.

As shown in FIG. 1, a light beam 3 from a light source 2 such as a semiconductor laser is focused by an imaging lens system 4, and then
It is deflected by an oscillating reflecting mirror 5. The deflected light beam 6 is passed through a fixed reflecting mirror 7 having a two-dimensional curved reflecting surface as described later.
The light is reflected by the beam, and is imaged at one point on the recording section 1, thereby printing information on the recording section 1.

Next, the configuration and operation of each part will be explained in more detail.

First, the light source 2 and the imaging lens system 4 are well-known devices, so their explanation will be omitted.

Next is the oscillating reflecting mirror 5, which consists of a oscillating shaft 5a and a plane mirror 5b fixed on the oscillating shaft 5a, as shown in FIG.
The plane mirror 5b is configured to swing around a swing shaft 5a. Specifically, commonly known examples include GENERAL 5C.
As described in the ANNING INC catalog (distributor [Nippon Laser J GSr 859-08), there is a galvanomirror-1 resonant reflector.

In the galvano mirror, the swing shaft 5a is made of a rigid body, and the entire swing shaft 5a is rotated by electromagnetic driving means to rotate the plane mirror 5.
Rotate b. The rotation angle of the plane mirror 5b, in other words, the deflection angle of the light beam can be arbitrarily changed by an external instruction signal.

On the other hand, in the resonant reflecting mirror, the swing shaft 5a is made of an elastic body, and the plane mirror 5b is rotated using torsional vibration at the resonance point of the swing shaft 5a. Energy is supplied by electromagnetic means, but because it utilizes resonance phenomena, it is possible to obtain large vibrations with a very small supply of energy.

The light beam 3 is deflected by hitting the rotating plane mirror 5b of the oscillating reflecting mirror 5 configured as described above and reflecting it.

Next, the fixed reflecting mirror 7 will be explained.

The reflecting surface of the fixed reflecting mirror 7 shown in FIG. 1 is formed as follows.

FIG. 2 is an explanatory diagram for explaining a specific example of the fixed reflecting mirror in FIG. 1.

In FIG. 2, the axis SL corresponds to the scanning line 1a of the recording section 1 shown in FIG.
Each point above. Further, point G corresponds to the reflection point of the oscillating reflecting mirror 5, that is, the deflection point of the light beam 6.

First, if an ellipse with major axis length A is drawn with point G and point P1 as focal points (focal points of the ellipse), an ellipse E1 is obtained. Considering the properties of an ellipse, the sum of the distances from any point on the ellipse El to the two focal points G and PL is equal to the length A of the major axis.

Therefore, we now draw the ellipse E along the direction perpendicular to the paper surface of Figure 2.
Consider a curved surface consisting of the locus of the ellipse E1 that is created when 1 is moved (hereinafter referred to as a curved surface along the ellipse E1), and further,
Consider a reflector whose inside curved surface is a reflective surface.

If we use a reflector along such an ellipse E1, it is obvious that a light beam traveling in any direction from point G will reach point P1 after being reflected by the ellipse reflector, and will also be reflected from point G. The optical path length to point P1 is always equal to A.

Next, by drawing an ellipse with major axis length A using points P2 and G as focal points (focal points of the ellipse), an ellipse E2 is obtained. In this case as well, the optical path length from point G to point P2 is always A. Point P
The same goes for 3 to P7, and the optical path length from point G is always A.
It is possible to obtain ellipses E3 to E7.

Next, consider the envelope of the ellipse group consisting of these ellipses E1-E7. Two envelopes are drawn, each touching each of the ellipses E1 to E7 in turn.

Therefore, in this specific example, we select one of the envelopes, that is, the curve T-T', and from the locus of the curve T-T' that is created when the curve T-T' is moved along the direction perpendicular to the page. Considering a curved surface (hereinafter referred to as a curved surface along the curve T-T'), a reflecting mirror whose concave side of the curved surface is a reflective surface is defined as the fixed reflecting mirror 7 shown in FIG.

When such a reflecting mirror is used as the fixed reflecting mirror 7, the point G
By changing the direction of the light beam from
By reflecting the light beam on a curved surface along ', the imaging point of the light beam can be sequentially moved on the scanning line la of the recording section 1, and the distance between each point on the scanning line la and the light source 2 (the optical path long)
can be kept constant regardless of the deflection angle. Therefore, by simply using a lens system that gives the light beam a constant focal length as the imaging lens system 4, it is possible to irradiate the light beam in the most converged state at any point on the scanning line 1a. There is no need to use conventional optical means for focal length correction, such as an fθ lens.

Next, FIGS. 3(a) and 3(b) are explanatory diagrams for explaining other specific examples of the fixed reflecting mirror in FIG. 1, respectively.

In FIG. 3, the ellipse E1 is similar to the specific example shown in FIG.
Obtain an ellipse group consisting of ~E7.

In FIG. 3(a), consider a curve T-T' inscribed in ellipses E1 and El corresponding to ends P1 and P7 of the scanning line 1a among this ellipse group, and A fixed reflecting mirror 7 is a reflecting mirror whose reflecting surface is a concave curved surface.

On the other hand, in FIG. 3(b), a curve T-T' circumscribing the ellipses E1 and El is similarly considered, and a reflecting mirror whose reflecting surface is the convex side of the curved surface along this curve T-T' is fixed. Reflector 7 is used.

In the two specific examples shown in FIGS. 3(a) and (b),
Although some error occurs in the optical path length from the light source 2 to each point on the recording section 1, it is within an allowable range.

Furthermore, when comparing these two specific examples, Fig. 3(b)
In the specific example shown in FIG. 3(a), the above-mentioned error can be made smaller than in the specific example shown in FIG. 3(a). This is because, as is clear from the figure, the intersection of ellipses E1 and El is located at the intersection of another ellipse E.
Since it is located inside each of ellipses 2 to E6 (inside the ellipse), the curve circumscribing the ellipses E1 and El can approach other ellipses E2 to E6 as much as possible, as shown in Figure 3 (b). , the error can be reduced, but in the case of an inscribed curve as shown in Figure 3(a), it cannot be drawn outside the intersection of El and El, so other ellipses E2 to E can be drawn within a certain distance.
6, and the error cannot be reduced to less than that certain distance.

However, in these two specific examples, if it is absolutely necessary to correct the above-mentioned errors, it is sufficient to provide a correction optical system in the optical path, and as can be easily inferred, a simple single lens is used as the correction optical system. Can be configured.

By the way, the curve T inscribed or circumscribed in the ellipse E1 and El
-T' can be drawn in any number, so it is possible to create a reflective surface of any size. Therefore, in these two specific examples, by making the reflecting surface of the fixed reflecting mirror 7 smaller, the deflection angle of the oscillating mirror 5 can be made smaller, making it easier to ensure deflection accuracy. At the same time, the shape of the fixed reflecting mirror 7 is also reduced, which is economical.

In the manner described above, the reflecting surface of the fixed reflecting mirror 7 shown in FIG. 1 is formed. Since the reflecting surfaces of the fixed reflecting mirror 7 are all two-dimensional curved surfaces, they can be easily created when actually manufactured.

As explained above, in this embodiment, since the oscillating projection mirror 5 is used, there are no unstable factors such as friction and rolling caused by rotation, unlike polygon mirrors in conventional devices.
There is no chance of shaft wobbling, and there is little surface tilt or optical axis tilt caused by machining or assembly accuracy. Also,
By using the oscillating mirror 5, it is possible to reduce the size and weight, consume less power, and perform high-speed scanning.

Further, in this embodiment, as described above, the optical path length does not change even if the optical beam is deflected by the fixed reflecting mirror 7, so the correction optical system fθ lens for controlling the optical path length is not required. When the reflecting surface of the fixed reflecting mirror 7 is small, the deflection angle of the oscillating forming projection mirror 5 may be small, so that a highly accurate oscillating forming projecting mirror can be manufactured at low cost.

Furthermore, in this embodiment, the optical path from the deflection point (point G on the oscillating projection mirror 5) to the light beam irradiation point of the recording section 1 is bent by the fixed reflecting mirror 7, so the entire apparatus can be made compact. It is possible to convert

As described above, according to this embodiment, high-speed recording is possible with a simple configuration, so a small, lightweight, and inexpensive laser printer can be realized.

In this embodiment, the plane mirror 5b in the swing-forming projection mirror 5 performs the oscillating motion as described above, so the angular velocity of the plane mirror 5b is constantly changing. Therefore, the scanning speed of the light beam 6 deflected by the oscillating projection mirror 5 may not be constant. In such a case, in the recording unit 1, the irradiation time and irradiation amount of the light beam will vary depending on the scanning position, so the printing quality may deteriorate, but this is due to the modulation pulse width of the light beam 3. This can be easily handled by controlling the pulse height.

In addition, since the oscillating mirror 5 is used, the scanning direction in the recording section 1 can be both left and right, as shown by the scanning line 1a in FIG. 1, but data is recorded only when scanning in the left direction. By recording data not only when scanning in the right direction, but also when scanning in the right direction, processing speed can be increased.

Next, FIG. 4 is a perspective view schematically showing an embodiment in which the present invention is applied to an optical tape device.

In FIG. 4, a light beam from a light source 2 passes through an optical system 10, is deflected by an oscillating mirror 5, is reflected by a fixed reflector 7 explained in FIG. 2 or 3, and is then reflected onto an optical tape. 11.

The optical system 10 includes an imaging lens system such as a collimating lens and a condensing lens, a means for separating reciprocating light, a reproducing optical means, a photodetector, and the like.

With such a configuration, it is possible to realize an optical tape device that is small, lightweight, and consumes little power.

〔Effect of the invention〕

As explained above, according to the present invention, by using an oscillating projection mirror, it is possible to achieve a reduction in size and weight, consume less power, and perform high-precision and high-speed scanning. . In addition, by using a fixed reflector, the optical path length does not change even if the optical beam is deflected, so there is no need for a correction optical system fθ lens to control the optical path length. Since the optical path is bent, it is possible to downsize the entire device.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining a fixed reflector used in the present invention, and FIG. 3 is a perspective view showing another specific example of the fixed reflector according to the present invention. FIG. 4 is a perspective view showing another embodiment of the present invention. Explanation of symbols 1...Recording section, 2...Light source, 3, 6...Light beam, 4...Imaging lens system, 5...Obcillating reflector, 7...
・・Fixed reflector agent Patent attorney Akio Namiki ft51 Needle correction, previous

Claims (1)

[Scope of Claims] 1. In an optical deflection device that deflects a light beam from a light source to scan a scanned medium, an imaging lens system that focuses the light beam and forms an image on the scanned medium; an oscillating reflector that deflects the light beam by reflecting the light beam with a first reflecting surface that performs an oscillating motion about a certain predetermined axis;
a fixed reflecting mirror that reflects the deflected light beam on a second reflecting surface and irradiates it onto the scanned medium, the second reflecting surface of the fixed reflecting mirror being directed from the light source to the scanning medium An optical deflection device characterized in that the optical path length to the irradiation point on the medium is formed by a two-dimensional curved surface that is substantially constant regardless of the deflection angle of the light beam by the oscillating reflecting mirror. 2. In the optical deflection device according to claim 1, the second reflecting surface of the fixed reflecting mirror has a first focal point of each ellipse as a reflecting point of the oscillating reflecting mirror, and each Prepare a group of ellipses in which the two foci of the ellipse are different arbitrary irradiation points on the scanned medium, and each ellipse has the same major axis length, and one envelope of the ellipse group is defined as 1. An optical deflection device, characterized in that the light deflection device is moved along a direction perpendicular to a plane containing an envelope, and has a curved surface formed by the locus of the envelope. 3. In the optical deflection device according to claim 1, the second reflecting surface of the fixed reflecting mirror has a first focal point as the reflecting point of the swinging reflecting mirror, and a second focal point as the reflecting point of the oscillating reflecting mirror. a first ellipse having one end point of the irradiation points on the scanned medium; a first ellipse having the same first focal point and the same major axis length as the ellipse; A second ellipse with one end point is prepared, and a circular arc or a higher-order curve that is inscribed or circumscribed in both the first and second ellipse is drawn in a direction perpendicular to the plane containing the arc or higher-order curve. An optical deflection device characterized in that it is a curved surface consisting of a locus created by moving the optical deflection device along the . 4. In the optical deflection device according to claim 1, 2, or 3, the light beam at the light source is modulated according to the angular velocity of the first reflecting surface in the oscillating reflecting mirror. An optical deflection device characterized in that the width and height can be changed.