JPH03260614A - Optical scanner - Google Patents

Abstract

PURPOSE:To obtain this inexpensive optical scanner having a simple constitution without requiring an expensive optical system such as an lens by guiding light irradiating from a light source to a photosensitive drum by using a specific plane optical waveguide. CONSTITUTION:Since the plane optical waveguide 15 for guiding a laser beam irradiating from a laser diode 11 to the photosensitive drum 17 has step type, approximately quadratic function type and uniform refractive index distribution respectively in the thickness direction, one direction of the plane direction and other direction, a so-called convergent lens is formed. Since the length of the waveguide 15 having the refractive index distribution in the fixed direction is 1/4 period length or length obtained by adding natural number times the 1/4 period length to the 1/4 period length, the waveguide 15 has f-theta characteristic. Thereby, light deflected by a rotational inclined mirror 14 and moved at a constant angular velocity is made incident upon the incident terminal 15A of the waveguide 15, reflected and refracted in the waveguide 15 and linearly outputted from a projection terminal 15B at the constant speed.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical scanning device used in a laser printer or the like, and particularly relates to one using a guiding waveguide.

[Prior Art] Conventionally, an optical scanning device for a laser printer as shown in FIG. 4 has been proposed.

In the apparatus shown in FIG. 4, a laser beam from a semiconductor laser 80 is made into a parallel beam by a collimator lens 82, and then deflected by a polycon mirror 84 rotating at a constant speed. The reflected light from this polygon mirror is f-
The light passes through the θ lens 86, is reflected by the plane reflecting plate 88, and is scanned along a straight line parallel to the rotation axis of the photosensitive drum 90, which rotates at a constant speed.

However, in the conventional optical scanning device as shown in FIG. This required expensive optical systems such as lenses.

In order to solve this problem, a device as shown in FIG. 5 can be considered. In the apparatus of FIG. 5, the semiconductor laser 91
The laser beam is made into a parallel beam by a collimator lens 93, and then deflected by a polygon mirror 94 that rotates at a constant speed. The reflected light from the polygon mirror 94 passes through an optical fiber array 95 in which the input end of a large number of optical fibers is arranged in an arc shape and the output end thereof is arranged in a straight line. Scanning is performed along a straight line E parallel to the axis.

[Problems to be Solved by the Invention] 5 However, in the optical scanning device shown in FIG. However, there was a problem that the yield was low. Furthermore, since there is a cladding portion in the scanning direction of the incident surface of the optical fiber array, there is a time during one scanning in which light cannot be emitted, which causes a problem in that the effective coupling efficiency decreases. In addition, in such a device,
The upper limit of resolution is determined by the manufacturing precision of the optical fiber array. It has been difficult to manufacture optical fiber arrays as described above at high density, and it has been difficult to achieve high resolution. Furthermore, a spherical lens array is required to focus the light emitted from the optical fiber array, but there is a problem in that the above-mentioned spherical lens array is difficult to manufacture.

Furthermore, since the entrance surfaces of a large number of optical fibers are arranged side by side, the circumference of the entrance side end of the optical fiber array becomes long, and therefore it is necessary to increase the distance between the polygon mirror and the optical fiber array. Therefore, there were problems such as the polygon mirror and the optical fiber array requiring extremely high placement precision.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an optical scanning device that is inexpensive and has a simple structure. Another object of the present invention is to provide an optical scanning device that is easy to manufacture.

[Means for Solving the Problems] In order to achieve this objective, the optical scanning device of the present invention includes a light source that emits an optical signal, and a deflection device that is deflected so that the locus of the optical signal emitted from the light source moves at a constant angular velocity. a deflection means for causing the
a planar optical waveguide in which an incident surface is disposed on the locus of the optical signal deflected by the deflecting means, and a photoreceptor is disposed opposite to the output surface, and the planar optical waveguide has a step in the thickness direction. It has a substantially quadratic function type in one direction of the mold plane, and a uniform refractive index distribution in the other direction, and the length in the direction with the uniform refractive index distribution is 1/4 period length, or a natural periodic length. It has a length that is several times longer than that, and has an entrance surface at one end surface on the axis of symmetry of a substantially quadratic function type refractive index distribution.

[Function] In the present invention having the above configuration, the planar optical waveguide has a step type refractive index distribution in one direction of the thickness direction and a uniform refractive index distribution in the other direction. forming a lens. Also, the length of this leading waveguide in the direction where the refractive index distribution is constant is ]/4 period length, or the length obtained by adding a natural number times the period length to that length, so this leading waveguide has r-θ characteristics. . Therefore, light whose trajectory is deflected by the deflection means and moves at a constant angular velocity enters the input end of the planar optical waveguide, is reflected and refracted within the waveguide, and is output from the output end. At this time, the trajectory of the light output from the output end changes linearly at a constant speed.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings.

First, the configuration of the optical scanning device of this embodiment will be explained using FIG. In FIG. 1, a laser diode 11 is connected to a known drive circuit and outputs laser light modulated according to image information stored in a field memory. This laser diode 11 is fixed downward. In front of the light emitting part of this racer diode 11,
A collimator lens 12 is arranged. This collimator lens 12 shapes the laser beam irradiated from the laser diode 11 into a parallel beam. A condensing lens 13 is placed in the optical path of this shaped laser beam to condense the laser beam. The condensing lens 13 is an aspherical lens, and the condensing position is different in two perpendicular directions. The light focusing position will be described later. A rotating inclined mirror 14 is disposed on the optical path of the light transmitted through the condensing lens 13. This rotating inclined mirror 14 rotates with a period of 1/2 during which laser light corresponding to one line is output from the laser diode 11. However, after the laser diode 11 irradiates one line of laser light, it becomes in a stopped state for a period of time -.

Therefore, while the laser diode 11 irradiates N lines of laser light, the rotating inclined mirror 14 rotates N times.

The rotating inclined mirror 14 and the condensing lens 13 rotate in synchronization. The focusing lens 13 has different focal lengths in two perpendicular directions, and the direction in which light is focused near the lens is always the vertical direction after being reflected by the rotating inclined mirror 14. The incident end 15A of the planar optical waveguide 15 is placed at a position where the laser beam reflected by the rotating inclined mirror 14 is focused in the vertical direction by the action of the focusing lens 13. This planar waveguide 15 will be explained in detail later. The output end 15B of the planar optical waveguide 15 is arranged parallel to the direction in which the cylindrical lens 16 extends.

The position at which the light transmitted through the cylindrical lens 16 is condensed coincides with the horizontal condensation position by the condenser lens 13, and the photoreceptor tram 17 is disposed at this position. This photosensitive tram 17 rotates by one dot each time the laser diode 11 irradiates one line of laser light. A known charging corotron, developing machine, transfer corotron, etc. are arranged around the photosensitive drum 17. These devices can form an image on a medium corresponding to the electrostatic latent image formed on the photoreceptor drum 17 by a known operation.

Next, the configuration of the planar waveguide 15 will be explained. Second
Figure (a) is a cross-sectional view of the planar optical waveguide 15 viewed from the X direction in Figure 1, and has a structure in which a portion 22 of refractive index n is sandwiched between a portion 21 of refractive index n2. As will be described later, the refraction '$n changes in the direction perpendicular to the broad line, and if its minimum value is n min, n□l, ,>n2. Therefore, the laser light incident from the entrance port 15A propagates within this plane with low loss in the same manner as an optical fiber. In the direction of this cross section, by focusing the focusing lens 13 on the incident surface 15A as shown in FIG. 3(a), it becomes possible to efficiently input the laser beam.

On the other hand, FIG. 2(b) is a sectional view of the planar optical waveguide 15 viewed from the Y direction of FIG. Inlet port 15 as shown in the figure
The refractive index distribution nz=n+''・5ech2(αd) is very close to a quadratic function distribution centered on a certain part of A.For this reason, if the entrance aperture 15A is sufficiently medium, the trajectory of the incident light beam will be becomes a sine wave with an amplitude proportional to the angle of incidence.The length l of the planar optical waveguide 15 is:
Since the period is one fourth, the laser beam is emitted perpendicularly to the emitting surface 15B from a position proportional to the angle at which it is incident. Light propagates freely within the horizontal plane of the planar optical waveguide 15 in the drawing. Therefore, by aligning the other focus of the focusing lens 13 with the surface of the photoreceptor TRAMF, as shown in FIG.
It is possible to converge to a point. The above-described planar optical waveguide is manufactured, for example, by applying the method shown in the specification and drawings attached to the application of Japanese Patent Application No. 01-309233.

Next, the operation of the apparatus constructed as above will be described. The racer diode 11 scans the image stored in the field memory and emits a laser beam with an intensity corresponding to the scanned pixel. A laser beam emitted from the laser diode 11 is made into a parallel beam by a collimator lens 12 and enters a focusing lens 13 .

The laser light that has passed through the condensing lens is deflected by the rotating inclined mirror 14 that is rotating at a constant speed, and the convergence point of the laser light scans the incident end 15A of the planar optical waveguide 15 at a constant angular speed. For example, a laser beam emitted at a time corresponding to a pixel at the upper left end of an image is reflected by the rotating oblique mirror 14 and enters the approximately left end of the incident end 15A of the planar optical waveguide 15 (in this state, the rotating reflecting mirror 1
4 is the initial position). and a planar optical waveguide 15
The light propagates while being reflected and refracted, and is emitted from the left end of the emitting end 15B. This emitted light converges in the horizontal direction but is diffused in the vertical direction.The emitted light is also focused in the vertical direction by the cylindrical lens 16 and is irradiated onto the left end of the photoreceptor tram 17. .

By irradiating the laser beam, the charge on the photosensitive drum 17 is released, and dots of an electrostatic latent image are formed on the photosensitive drum 17. Every time the position on the image corresponding to the laser beam irradiated from the laser diode 11 shifts to the right, the rotary reflection mirror 14 rotates by a minute angle, and the photoreceptor tram 17
The irradiation position of the laser beam irradiated upward shifts to the right. At the time when the upper right end of the image stored in the field memory is scanned, the rotating inclined mirror 14 rotates approximately half a rotation, and the laser beam is irradiated onto the approximately right end of the photoreceptor drum 17. The rotating reflection mirror 14 rotates at a constant angular velocity, or if the refractive index of the planar optical waveguide 15 is configured as described above, the irradiation position of the laser beam irradiated onto the photoreceptor tram 17 is rotated at a constant angular velocity. Moving. Then, when the rotary inclined mirror 14 further rotates and returns to the initial position, the laser beam corresponding to the next line is irradiated. During this time, the photosensitive tram 17 rotates by one dot. In this way, an electrostatic latent image is formed line by line.

By repeating the above operations, an electrostatic latent image for one screen is formed on the photoreceptor drum 17. This electrostatic latent image is developed with toner by a developing device, visualized, and transferred onto a medium.

In the above embodiment, a rotating inclined mirror is used as the deflection means, but the present invention is not limited to this, and a polygon mirror may also be used. It can also be constructed by a rotating drum or the like having laser diodes, light emitting diodes, etc. provided on its circumferential surface. Various other modifications are possible without departing from the spirit of the invention.

[Effects of the Invention] As is clear from the detailed description above, the present invention eliminates the need for an expensive optical system such as an f-theta lens and the need to array a large number of optical fibers. . Furthermore, when it is necessary to focus the light emitted from the planar optical waveguide, an inexpensive lens such as a cylindrical lens can be used.

Therefore, the entire device can be constructed at low cost.

Furthermore, there is no restriction in resolution or reduction in effective coupling efficiency due to the presence of a crut in the scanning direction. Furthermore, since the entrance of the optical waveguide can be made small, the distance between the deflection means and the optical waveguide can be shortened, so that the precision required for their arrangement is relatively relaxed and manufacturing is easy.

[Brief explanation of drawings]

1 to 3 show embodiments embodying the present invention, FIG. 1 is a perspective view of the optical scanning device of the embodiment, and FIG. 2 is a planar optical waveguide used in the embodiment. FIG. 3 is a diagram illustrating the refractive index distribution of , and FIG. 3 is a diagram illustrating the propagation of light centered on the leading wavepath. Further, FIG. 4 is a diagram illustrating an example of a conventional optical scanning device, and FIG. 5 is a diagram illustrating another example of a conventional optical scanning device. In the figure, 11 is a laser diode, 14 is a rotating oblique mirror corresponding to a deflecting means, 15 is a plane optical waveguide corresponding to a plane waveguide, 15A is an input end thereof, and 15B is an output end thereof.

Claims (1)

[Claims] 1. A light source that emits an optical signal, a deflection means that deflects the trajectory of the optical signal emitted from the light source so as to move at a constant angular velocity, and an incident surface is disposed on the trajectory of the optical signal deflected by the deflection means, a planar optical waveguide in which a photoreceptor is disposed facing a surface, and the planar optical waveguide has a substantially quadratic refraction in one direction of the stepped plane in the thickness direction and a uniform refraction in the other direction. The length in the direction having a uniform refractive index distribution is approximately 1/4 period length of the meandering period of light due to the refractive index distribution, or a natural number times the period length. and has an exit surface perpendicular to the axis of symmetry of the substantially quadratic refractive index distribution, and has an entrance surface near a point intersecting the axis of symmetry on a surface opposite to the exit surface. Characteristic optical scanning device.