JPS626230A - Optical deflecting device - Google Patents

Abstract

PURPOSE:To deflect parallel light passing through a light transmission medium by a specific angle and to converge it on one point by providing one group of electrodes which connect having the same strip axis with a Fresnel beltlike plate at right angles to the optical axis of homogeneous light on at least one surface of the light transmission medium. CONSTITUTION:When a voltage is applied to one of transparent electrode groups 20, 22, 24, 26, and 28, a part under the transparent electrodes of the one group have optical anisotropy different from that of any other part, so a beltlike Fresnel transmissivity distribution, i.e. refractive index distribution is formed in a substrate 16. Consequently, a laser beam 32 varies in light velocity at a different refractive index when passing through the part where said refractive index distribution is formed while propagated in the substrate 16, so the laser beam 32 is converged on a position on a screen 34 corresponding to the transparent electrode group applied with the voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an improvement in an optical deflection device for deflecting light.

BACKGROUND OF THE INVENTION Devices such as laser beam printers and bar code readers use optical deflection devices to deflect light to a desired angle. Polygon mirrors, hologram scanners, etc. are known as such optical deflection devices, but all of them are equipped with mechanically movable parts such as a rotation mechanism and its drive device, so the devices are complex and large. Moreover, sufficient durability was not necessarily obtained.

Means for Solving the Problems The present invention has been made against the background of the above circumstances, and its gist is (1) a monochromatic light source that emits monochromatic light; and (2) the monochromatic light source. (3) a first deflection element that changes the deflection angle of the monochromatic light emitted from the first deflection element in advance by an acousto-optic effect or an electro-optic effect; A light transmission medium having a switching action, and a group of electrodes arranged in a row on at least one surface of the light transmission medium and having a strip width similar to that of a Fresnel strip in a direction perpendicular to the optical axis of the monochromatic light, are arranged to transmit the monochromatic light. a second optical deflection element having at least one control electrode provided in the optical axis direction of the second optical deflection element;
It consists in including.

Operation and Effect of the Invention In this way, by applying a voltage to the group of electrodes of the second optical deflection element, a Fresnel strip-like transmittance distribution corresponding to the group of electrodes is created in the light transmission medium. is formed. Parallel light passing through the light transmission medium in which a Fresnel band-like transmittance distribution is formed has the effect of converging on one point after being deflected by a predetermined angle. Further, when the light incident on the second optical deflection element is deflected in advance by the first deflection element under a constant voltage application state to the control electrode, the focal point is moved accordingly. Therefore, when the voltage application state to the control electrode of the second light deflection element and the deflection state by the first light deflection element are changed, the focal point of the light is changed over a wide range. Therefore, there is no need for a rotation mechanism for deflecting light, a driving device for the rotation mechanism, etc., so that the device can be made smaller and have sufficient durability.

Preferably, the control electrode has a plurality of groups of electrodes in the direction of the optical axis of the monochromatic light, and each electrode constituting the group of electrodes is in contact with the corresponding electrode in the other group. They are arranged so as to be sequentially shifted by a certain distance in one direction perpendicular to the optical axis of the monochromatic light as the monochromatic light advances in the traveling direction of the monochromatic light. In this case, if a voltage is selectively applied to each group of electrodes, the light is converged at a position corresponding to the above-mentioned certain distance, and the deflection angle corresponding to the group of electrodes to which the voltage is applied is You can get it.

Embodiment FIG. 1 shows a light deflection device used in a laser printer or the like, in which a substrate 16 is fixed on a base 10 whose position is fixed. The substrate 16 is made of, for example, ferroelectric ceramic (
It is a light transmission medium made of an electro-optical material such as PLZT) and has a predetermined thickness.As shown in FIG. In the example, 5 groups) of transparent electrode groups 20.
22, 24, 26, and 28 are arranged in the direction of the optical axis X, respectively. The transparent electrode groups are constructed in the same way, for example, the transparent electrode group 20 includes individual electrodes 20a, 20b, 20 that are continuous in the direction perpendicular to the optical axis X and have a strip width similar to that of a Fresnel strip. c.
, 20d, 20e, etc.

As shown in FIG. 3, the individual electrodes constituting the transparent electrode group 20.22.24.26.28 are connected to corresponding electrodes in other adjacent groups in the direction of light propagation. In contrast, the transparent electrode groups 20, 22, 24, 26, and 28 are sequentially shifted by a slight dimension A, and the transparent electrode groups 20, 22, 24, 26, and 28 are wired so that a voltage can be applied to each group. Such transparent electrode group 20.22.24.26.28
The substrate 16 provided with the transparent electrode 18 constitutes the second optical deflection element of this embodiment.

A monochromatic light source 30 consisting of a semiconductor laser element or the like outputs a laser beam 32 via an optical fiber 36 and a fixed position substrate 38, and the laser beam 32 is directed to a condenser lens 3.
1, the light is focused on one point, that is, the condensing point 33, and then diffused again and made incident on one side of the substrate 16, and within the substrate 16, after being guided along the surface of the substrate 16. The light is emitted from the other side and is focused on a screen 34 consisting of a master drum of a laser printer or the like. As shown in FIG. 4, a cylindrical lens 40 for focus correction may be provided between the substrate 16 and the screen 34 as necessary, and other optical elements may be provided as appropriate. can be used.

The substrate 38 is made of a material having translucency and a piezoelectric effect, such as LiNbO3 crystal, and has a thickness of about 0.5 mm, and an optical waveguide is provided on its negative surface. This optical waveguide has a property of having a larger refractive index than other parts of the substrate 38 and confining light in the thickness direction, so that light can be guided suitably.
By diffusing Ti (titanium) from the surface, a relatively thin layer of approximately several micrometers is formed. and,
As shown in FIG. 5, the laser beam 32 incident from the end face of the optical fiber 36 is converged into parallel light in the light convergence section 42 while being guided through the optical waveguide, and is converged into parallel light in the light deflection section 44. It is deflected by the effect and is emitted from the other end face.

That is, the light converging section 42 is arranged in the plane direction of the substrate 38 and in the optical axis direction of the laser beam 32 . Its optical axis in the direction perpendicular to. By diffusing a diffusing material such as Ti such that the diffusion concentration increases as the distance approaches the optical axis L0, the refractive index of the optical waveguide increases as the distance approaches the optical axis L0, thereby providing a convex lens function. The optical deflection section 44 uses a surface acoustic wave (ultrasonic wave) 50 excited by a pair of comb-shaped electrodes 46. A periodic refractive index change is formed, and a laser beam passing through this is diffracted along the optical axis by Bragg diffraction. That is, when the wavelength of light is λ, the refractive index of the optical waveguide is n, and the wavelength of the surface acoustic wave 50 is 8, the diffraction angle 2θ8 due to Bragg diffraction is obtained according to the following equation (1).

2sin θ8=λ/nΔ (1) Then, when the frequency of the surface acoustic wave 50 is changed by Δr as the frequency of the voltage supplied to the comb-shaped electrodes 46 and 48 is changed, the following Laser beam 3 according to equation (2)
2 is changed by the deflection angle Δθ8. Therefore, in this embodiment, the substrate 38 provided with the comb-shaped electrodes 46 and 48 constitutes the first optical deflection element. Note that although the surface acoustic waves 50 cannot actually be seen with the naked eye, they are shown for ease of understanding. In this embodiment, since the substrate 38 is made of LiNbO2 that functions as a piezoelectric element, surface acoustic waves 50
However, an ultrasonic transducer made of PZT, ZnO, etc. may be attached to the end surface of the substrate 38.

2ΔθB#λ・Δf/v (2) However,
■ is the propagation velocity of surface acoustic waves.

The effects of this embodiment will be explained below.

When a voltage is applied to one of the transparent electrode groups 20.22.24.26.28, the portion located under the transparent electrode of the group exhibits a different optical anisotropy than the other portions.
Within the substrate 16, a Fresnel band-like transmittance distribution, that is, a refractive index distribution is formed. Therefore, when the laser beam 32 passes through a portion where a Fresnel strip-like refractive index distribution is formed while propagating within the substrate 16, the speed of light in the portion where the refractive index is different changes, which is essentially a Fresnel band-like refractive index distribution. A mask having a band-like transmittance distribution is irradiated with parallel light beams, and the laser beam 32 is focused on a position on the screen 34 corresponding to the transparent electrode group to which the voltage is applied. Then, when a voltage is applied to another group of transparent electrodes, the laser beam 32 is focused on a point corresponding to the group of transparent electrodes to which a voltage is newly applied according to the same effect as described above.

For example, if the light focusing position when a voltage is applied to the transparent electrode group 20 is set to point S3, the light will be focused at 82 points when a voltage is applied to the transparent electrode group 22. The interval between the S3 point and the 82nd point corresponds to the constant distance A. In this way, the transparent electrode groups 20, 22, 24.
26. The laser beam 32 is deflected to a desired angle in response to an alternative voltage applied to 28 to
The light is focused on any one of the points S6 to S6.

In the above state, when the frequency of the voltage supplied to the comb-shaped electrodes 46 and 48 is changed, the laser beam 32 before being incident on the end face of the substrate 16 is caused to move inside the substrate 38 according to the frequency change. Since the beam 32 is deflected according to equation (2), the focal point of the beam 32 is changed on the screen 34. For example, when a voltage is applied to the transparent electrode group 20, the convergence point of the laser beam 32 changes from the condensation points SI to Sz depending on the frequency of the voltage supplied to the comb-shaped electrodes 46.48. The position is determined within the point-to-point interval.

By controlling the frequency change of the voltage supplied to the comb-shaped electrodes 46 and 48 and the voltage applied to the transparent electrode groups 20 to 28, the laser beam is applied to any position within the area indicated by the broken line on the screen 34. While the beam 32 is focused, by controlling the screen 34 to move up and down, desired characters and the like can be drawn.

As described above, according to this embodiment, regarding the deflection of the laser beam 32, the substrate 16 is provided with a plurality of electrode groups on at least one surface having a strip width similar to that of a Fresnel strip, and the comb-shaped electrodes 46, 48 are used. Since the provided substrate 38 is used, the optical deflection device has no moving parts, is compact, and has extremely high reliability. That is, compared to the conventional case using a polygon mirror or a hologram scanner, a rotation mechanism and its driving device are not required, and the device becomes smaller and simpler, and its durability is improved. Furthermore, since the light convergence position can be changed by the light deflection action of the two deflection elements arranged in series, it is possible to move the light convergence point over a wider range.

Here, as shown in FIG. 6, the second optical deflection element may be composed of a substrate 16 and an analyzer 52 provided on the output side thereof. In this case, among the light that has passed through the refractive index distribution formed in the substrate 16, the light that has passed directly under the voltage-applied electrode has a different polarization state than the light that has passed through other parts, so the analyzer 52 Passage is obstructed at Therefore, a Fresnel strip-shaped mask corresponding to the transparent electrode group to which voltage is applied is substantially formed on the analyzer 52, and the laser beam 32 is directed to the transparent electrode group to which voltage is applied. It is deflected in a direction corresponding to the position.

Further, although the transparent electrode 18 is used in this embodiment, the electrode does not necessarily have to be transparent.

Furthermore, as shown in FIG. 7, a liquid crystal cell 54 may be used instead of the substrate 16. In this liquid crystal cell 54, a homogeneously arranged N-type nematic liquid crystal 60, for example, is sealed in a space of about ten-odd μm between a pair of glass plates 56 and 58. A plurality of groups of transparent electrodes each having a strip width similar to that of a Fresnel strip are arranged in the direction of the optical axis in the same way as described above. In the figure, a group of transparent electrodes 62 is shown, and this group of transparent electrodes 62 consists of a pair of upper and lower electrodes 62a and 62"a, 62b and 62"b.
, 62c and 62"C. According to this embodiment, for example, when a voltage is applied between the upper and lower electrodes of the transparent electrode group 62, the portion sandwiched between them becomes cloudy. Since a mask similar to a Fresnel strip is formed, the laser beam 32 is deflected by the same effect as described above.The liquid crystal 60 exhibits an electro-optic effect exhibiting optical anisotropy when a voltage is applied. In this case, the beam 32 is deflected according to the same effect as that of the substrate 16 described above.When the liquid crystal cell 54 is used as the second optical deflection element in this way, the liquid crystal 60 is the optical transmission medium. Configure.

Further, the first optical deflection element may be constructed from the substrate 64 shown in FIGS. 8 and 9. That is,
The substrate 64 is made of a material that has an electro-optic effect, and the laser beam emitted from the semiconductor laser element 66 fixed at the end face is converted into parallel light beams in the light converging section 68, and then converted into parallel light beams in the light deflecting section. It is deflected at 70 and ejected from the other end face. The light converging section 68 is similar to the light converging section 42, and has a refractive index distribution having a convex lens function due to diffusion. The optical deflection section 70 is composed of a pair of electrodes 72, 74 located on both sides of the optical axis L2, and an electrode 76 that intersects obliquely with the optical axis L2 between these electrodes 72, 74. This utilizes the effect of the material constituting 78 changing its refractive index in response to an electric field.

When a voltage is applied between the electrodes 72 and 74 and the electrode 76, the electric field E and the refractive index change Δn in the optical waveguide 78 on the A-A, B-B, and C-C lines of the optical deflection section 70 are as shown in FIG. , as shown in FIGS. 11 and 12.

Therefore, the laser beam traveling along the optical axis L2 experiences a different refractive index at each part of the light beam and is deflected according to the magnitude of the refractive index change Δn.
By temporally changing the voltage applied between electrode 74 and electrode 76, the deflection angle of the laser beam can be changed. Note that 80 is a thin film such as 5102, and is a buffer layer provided so that light propagates efficiently within the optical waveguide 78. Note that in FIGS. 10 to 12, the lower side in FIG. 8 is taken as the positive side, and the electrodes 72 are viewed from the right hand and the electrodes 74 are viewed from the left hand.

The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a perspective view illustrating an optical deflection device according to an embodiment of the present invention. FIG. 2 is an enlarged view of the second optical deflection element in FIG. 1. FIG. 3 is a diagram illustrating in detail the arrangement of electrodes of the second optical deflection element in FIG. 2. FIG. 4 is a diagram illustrating optical elements that can be used in the apparatus of FIG. 1. FIG. 5 is a diagram illustrating the configuration of the first optical deflection element in FIG. 1. FIG. 6 is a diagram showing a main part of a second optical deflection element in another embodiment of the present invention. FIG. 7 is a diagram showing a second optical deflection element in another embodiment of the present invention. FIG. 8 and FIG. 9 are a plan view and a side view showing a first optical deflection element in another embodiment of the present invention. 10, 11, and 12 are diagrams showing the electric field and refractive index changes on the lines AA, BB, and CC of the optical deflection section in FIG. 8, respectively. 30: Monochromatic light source Applicant: Brother Industries, Ltd. Figure 2 Figure 4 Figure 6 Figure 8 Figure 9

Claims (2)

[Claims] (1) A monochromatic light source that emits monochromatic light, a first deflection element that deflects the monochromatic light emitted from the monochromatic light source in advance by an acousto-optic effect or an electro-optic effect, and the first deflection element has a predetermined thickness. a light transmission medium that guides the monochromatic light through the light transmission medium and has an optical switching function; and at least one surface of the light transmission medium has a strip width similar to that of a Fresnel strip in a direction perpendicular to the optical axis of the monochromatic light. 1. A light deflection device comprising: a second light deflection element having a control electrode in which the group of electrodes connected in series includes at least one control electrode provided in the optical axis direction of the monochromatic light. (2) The control electrode of the second optical deflection element has a plurality of electrodes of the group in the optical axis direction of the monochromatic light, and each electrode constituting the group of electrodes is one of the electrodes of the other group. The light deflection device according to claim 1, wherein the light deflection device is sequentially shifted in one direction in a direction perpendicular to the optical axis of the monochromatic light as the direction of propagation of the monochromatic light increases with respect to the corresponding electrode of the monochromatic light. .