JPH0746180B2 - Optical information generating method and device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an optical information generating method and device, and more particularly to an optical information generating method and device suitable for application to an optical recording device such as a laser printer.

[Background of the Invention]

Conventionally known laser printers use a rotating polygon mirror, and thus it has been difficult to miniaturize and solidify. Therefore, a device that is downsized by using a spatial modulator has been proposed (Proceedings of SPIE (The Society of Ph.
oto-Optical Instrumentation Engineers) 388, page 46). The operating principle of the device will be described with reference to FIGS. 8, 9 and 10.

FIG. 8 shows an electrode wire pattern formed on the LiNbO ₃ crystal l, and the electrode wire pattern is composed of a plurality of electrode wires 2.

FIG. 9 is a side view of the electrode wire 2 of FIG. 8. By applying a (+) voltage or a (−) voltage to each electrode wire 2, a leakage electric field 8 is generated in the crystal surface. Occurs. When the adjacent electrode lines 2 have the same potential, no electric field is generated.
The crystal part between the electrode lines 2 is an information constituent part. In FIG. 9, information "101" is generated between the electrode lines 2 depending on whether or not the leakage electric field 8 is generated. To be done.

10 (a) and 10 (b) are a plan view and a side view of a conventional spatial light modulator.

When the incident laser light 3 passes through the crystal l, it undergoes phase modulation through the electro-optical effect due to the leakage electric field shown in FIG. The information generated by the crystal l is formed on the screen 6 by the imaging lens 4. By the way, since the information generated in the crystal 1 is formed as a light phase pattern, it is necessary to convert the light phase pattern into a light intensity pattern. Therefore, in FIGS. 10 (a) and 10 (b), a Schlieren optical system is used. That is, the laser light passing through the information component having no leakage electric field is shielded by the shielding plate 5, but the laser light passing through the portion having the leakage electric field is subjected to the phase modulation, so that the imaging lens 4 is formed. On the focal plane of, the light spot spreads, and the light protruding from the shielding plate 5 reaches the screen 6.

However, in the spatial modulation device in FIG. 10, the position adjustment of the shield plate 5 and the shape of the shield plate largely depend on the signal-to-noise ratio of information formation on the screen 6. That is, even if the shielding plate 5 is moved back and forth and left and right even for a minute distance, light leaks and the shape and size of the shielding plate 5 have a great influence on information formation.

[Object of the Invention]

An object of the present invention is to improve such conventional problems and to provide a compact and highly reliable optical information generating method and apparatus without using a shielding plate.

[Outline of Invention]

The above object of the present invention is to arrange a plurality of electrode wires on an electro-optic crystal having an optical waveguide layer with at least two of them short-circuited, and to horizontally inject on the crystal surface of each electro-optic crystal. The passing light beam is spatially phase-modulated by the electrode wire, and a part of the light distribution expanded by the diffraction of the phase-modulated light beam is provided in the slit of the aperture of the optical system or the convergence position of the light beam. The light having a minimum unit of multiples of the minimum interval between the electrode lines, which is blocked by the aperture due to the above, forms an image of the light passing through the aperture, and converts the phase modulation of the light flux into the intensity modulation of the imaging light. An optical information generating method characterized by generating information, and an electro-optic crystal having an optical waveguide layer in which a plurality of electrode wires are arranged on the surface by shorting at least two of them, Light passing through an electro-optic crystal An electro-optic crystal that spatially phase-modulates the electro-optic effect by a voltage applied to the electrode line, an optical system that forms a phase-modulated light beam from the electro-optic crystal, and the phase-modulated light beam. The aperture of the optical system that shields a part of the light distribution expanded by the diffraction of, or aperture means by a slit arranged at the convergence position of the light flux, and the phase of the light flux is changed by the light passing through the aperture means. This is achieved by an optical information generating device characterized by generating optical information having a minimum unit of a plurality of minimum intervals between the electrode lines, which is obtained by converting modulation into intensity modulation of imaging light.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of an optical information generating system device showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of an optical information generating operation in FIG.

In FIG. 1, 8 is a Y-cut LiNbO ₃ crystal, 9 is an optical waveguide layer by Ti diffusion on the crystal surface, 10 is an electrode wire, 11 is a slit, and 12 is a lens.

When the X, Y, and Z directions are defined in space as shown in the figure, the laser light 7 polarized parallel to the Z direction is guided to the optical waveguide layer 9 on the surface of the crystal 8. Conventionally, as shown in FIG. 10 (b), the crystal 8 is incident on the crystal surface at a certain angle, and the light reflected by the surface is projected toward the lens 4. On the other hand, in the present embodiment, as shown in FIG. 1, laser light is made to enter the crystal surface horizontally.

A plurality of electrode lines 10 are arranged on the crystal surface with the Z direction as the arrangement direction, and a pattern is formed by two lines. That is, as shown in FIG. 8, the conventional electrode wires 2 are arranged alone, whereas the electrode wires 10 of this embodiment are arranged such that two end wires are short-circuited at each end. Therefore, a voltage is applied to the two lines, and a leak electric field is generated between the adjacent electrode lines 10 on both sides of the two lines as a unit.

The operating principle of these electrode wires 10 will be described with reference to FIG. In this case, an example in which twice the minimum distance d between the electrode lines 10 is used as one bit of generated information is shown. That is, a case where m = 2 is shown as a parameter m described later. The light 13 that passes through the pattern of the electrode lines 10 is phase-modulated by the voltage applied to the electrode lines 10 by the electro-optical effect. Electrode wire 10
When the distance between them is d, the length of the electrode wire 10 is l, and the applied voltage is V, the electric field E _Z generated by the applied voltage V is approximately given by the following equation.

Here, α is a constant.

Further, the phase of light passing through the electrode wire 10 is given by the following equation.

Here, λ is the wavelength of light, ne is the extraordinary refractive index, and r ₃₃ is the electro-optic constant.

As will be described later, the phase is set so that the contrast ratio on the screen or the light utilization efficiency is maximized, and is set to π here. At this time, the length l of the electrode wire 10 is given by the following equation from the above equation (2).

FIG. 2 (b) shows the phase distribution of light after passing through the electrode line pattern when the length l of the electrode line 10 set according to the above equation (3) is used. As shown in FIG. 2 (a),
When voltage V is applied to the two pairs of electrode wire patterns in the center,
Leakage electric fields in opposite directions are generated at the left end and the right end, and the laser light has a phase distribution of π on the left side of the voltage application electrode line 10, −π on the right side, and 0 at other positions. In FIG. 1, the second
The emitted light 13 having the phase distribution shown in FIG.
And passes through lens 12 to reach screen 6. Here, g represents the distance between the electrode wire pattern and the slit 11. The lens 12 is a lens for focusing the phase distribution obtained by the electrode line pattern on the screen 6. When all the phase-modulated outgoing light 13 reaches the screen 6, the screen 6 loses the phase-modulated information and only bright lines are obtained on the screen 6. In the present embodiment, the slit 11 is used to convert the phase-modulated light pattern into a light intensity pattern on the screen 6. The slit 11 is placed at a position sufficiently distant from the width d of the electrode line pattern, that is, a position regarded as a far field. The width a of the slit 11 is set as follows. That is, the light diffracted at the electrode line pattern interval d is sufficiently blocked, and is twice the electrode line pattern interval d, that is,
The light diffracted by 2d is set to pass sufficiently. Approximately, it becomes the following formula.

However, here, m = 2. Further, γ and δ are 0
It is a constant from 1 to 1 and is determined by strict analysis of the contrast ratio, light utilization efficiency, and the like.

When the slit 11 is set in this way, a light pattern of "1010" is formed on the screen 6, as shown in FIG. 2 (c). That is, the electrode wire with the leakage electric field
Light passing through the interval of 10 is diffracted at the interval d of the pattern, and is blocked by the slit 11. On the other hand, light passing through the interval of the electrode wire 10 having no leakage electric field is diffracted at twice the pattern interval d. To pass the slit 11 sufficiently. Therefore, on the screen 6, the information "1" is a bright point and the information "0" is a dark point.

Although FIG. 1 shows an example using the slit 11,
Even if the slit 11 is not used, the same effect can be obtained by setting the diameter of the lens 12 to be approximately the same as the width a of the slit.

FIG. 3 is a perspective view of an optical information generating apparatus according to another embodiment of the present invention.

Although the slit 11 is arranged in front of the lens 12 in the embodiment shown in FIG. 1, the slit 11 may be arranged at the focal plane of the lens 12 as shown in FIG. f is the focal length of the lens, m
= 2, the size of the width a of the slit 11 is given by the following equation instead of the equation (4).

The arrangement and configuration other than the slit 11 in FIG. 3 are the same as those in FIG.

FIG. 4 and FIG. 5 are explanatory views of electrode line patterns showing still another embodiment of the present invention.

In FIGS. 1 and 3, the minimum distance d of the electrode line pattern is 2
Although double is set as one bit of the configuration information, in FIGS. 4 and 5, a method of setting three times the minimum electrode line interval d, that is, m = 3, and four times, that is, m = 4 is one bit, respectively. Is shown.

The electrode line pattern 14 of FIG. 4 is formed by short-circuiting one end of two electrode lines at an interval twice the minimum interval d, and a large number of patterns 14 are arranged at intervals d.

Now, when a voltage V is applied to two adjacent electrode line patterns 14, the potentials at both ends have opposite polarities and a leak electric field is generated between the electrode line patterns 14 on both sides, so that the incident laser beam 15 is phase-modulated. , Its phase distribution becomes π at the position of the leakage electric field, and becomes 0 at the other positions. Light having a phase of π or −π is diffracted at the minimum distance d, so
The light having the phase of 0 which is blocked by is diffracted at three times the minimum distance d, passes through the slit 11 and becomes the configuration information "1010" on the screen.

In the electrode line pattern 17 of FIG. 5, a device in which two electrode lines having a minimum distance d are short-circuited at one end and two electrode lines having a distance d connected to the ground potential are sandwiched between them are arranged in a large number of sets. Composed.
When the voltage V is applied to the short-circuit element, leak electric fields in opposite directions are generated between the ground electrode lines on both sides of the short-circuit element, so that the incident laser beam 18 is phase-modulated to π, −π, 0.

In the case of FIGS. 4 and 5, the width a of the slit 11 can be derived by substituting 3, 4 for m in the above equation (4).

FIG. 6 is a perspective view of an optical information generating apparatus showing still another embodiment of the present invention, and FIG. 7 is an explanatory view of the optical principle of FIG.

In the embodiment shown in FIG. 6, the slit used in the embodiment shown in FIG.
11, instead of lens 12, gradient index rod lens array 2
0 is used.

The gradient index rod lens array 20 has a large number of fibers.
An array of lenses that distributes the laser light with a predetermined refractive index by each fiber lens.

FIG. 7 (a) shows an optical system in which the lens 12 of FIG. 1 is used. When the lens radius is a / 2 and the distance from the electrode line pattern to the lens is g, the lens NA (Nume
rical Aperture) is given at a / 2g. Therefore, a lens of NA = a / 2g may be used by using a / g determined by the above equation (4). On the other hand, in the gradient index rod lens array 20, as shown in FIG. 7C, the light from each part of the electrode line pattern is combined through a small lens, and the phase-modulated light pattern is displayed on the screen 6. Form an image. Therefore, the distance between the electrode line pattern and the screen 6 may be extremely short, and the optical information generator can be downsized.
NA (Num of the optical system consisting of the slit 11 and the lens 12 in FIG. 1)
ERical aperture) is given by a / 2g, the NA of the gradient index rod lens 20 may be a gradient index rod lens determined by the following equation derived from the equation (4).

The optical information generators shown in FIGS. 1 and 6 show the case where the laser light passes through the optical waveguide layer 9 on the surface of the LiNbO ₃ crystal 8 as shown in FIG. 7 (b). As shown in FIG. 10 (b), it is also possible to use an optical system that totally reflects inside the crystal 8.

〔The invention's effect〕

As described above, according to the present invention, the information is generated by using the aperture of the optical system without using the shielding plate and passing the light flux phase-modulated by the electrode line pattern through the aperture, so that a small device Therefore, highly reliable optical information can be generated.

[Brief description of drawings]

FIG. 1 is a perspective view of an optical information generating apparatus showing an embodiment of the present invention, FIG. 2 is an explanatory view of the optical information generating operation in FIG. 1, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a perspective view of an optical information generating apparatus, FIG. 4 is an explanatory view of an electrode line pattern showing another embodiment of the present invention, and FIG. 6 is a light showing another embodiment of the present invention. FIG. 7 is a perspective view of the information generating apparatus, FIG. 7 is an explanatory view of the optical principle of FIG. 6, FIG. 8 is a view showing a conventional electrode wire pattern, and FIG. 9 is a side view of the electrode wire of FIG. FIG. 10 is a plan view and a side view of a conventional spatial light modulator. 7: Laser light, 8: LiNbO ₃ crystal, 9: Optical waveguide layer, 2, 10, 14, 1
7: electrode line pattern, 11: slit, 12: lens, 20: gradient index rod lens array, 6: screen.

Claims (4)

[Claims] 1. A plurality of electrode wires are arranged on an electro-optic crystal having an optical waveguide layer, at least two of which are short-circuited, and are horizontally incident on the crystal surface of each electro-optic crystal and pass therethrough. The light beam to be spatially phase-modulated by the electrode wire, and a part of the light distribution expanded by the diffraction of the phase-modulated light beam is provided by an aperture of an optical system or a slit arranged at the convergence position of the light beam. Optical information with a minimum unit of multiples of the minimum interval between the electrode lines, which is obtained by forming an image of the light passing through the aperture and converting the phase modulation of the light flux into the intensity modulation of the imaging light. A method for generating optical information, which comprises: 2. An electro-optical crystal having an optical waveguide layer in which a plurality of electrode lines are arranged by short-circuiting at least two of the electrode lines on a surface, and a light flux passing through the electro-optical crystal is passed through the electrode line. An electro-optic crystal spatially phase-modulated by an electro-optic effect due to a voltage applied to the optical system, an optical system for forming an image of a phase-modulated light beam from the electro-optic crystal, and a diffraction of the phase-modulated light beam to spread the light. The optical system has an aperture of an optical system that shields a part of the distributed light or an opening means by a slit arranged at the convergence position of the light flux, and the phase modulation of the light flux is imaged by the light passing through the opening means. An optical information generating device, which generates optical information having a minimum unit of a plurality of minimum intervals between the electrode lines, which is converted into light intensity modulation. 3. An optical information generating apparatus according to claim 2, wherein a gradient index rod lens array is used as the optical system and the aperture means of the optical system. 4. The optical information generating apparatus according to claim 2, wherein the plurality of electrode lines are arranged in units of an electrode line pattern having two shorted ends.