JPH01129205A - Hologram deflector - Google Patents

Abstract

PURPOSE:To enable the nonmechanical control of a deflection angle by projecting the beam from a wavelength variable laser to a hologram module which is radially disposed with holograms and emitting the beam deflected by the holograms to a prescribed direction. CONSTITUTION:Four sheets of the flat plate holograms 15A-15D are diagonally embedded into a rectangular parallelepiped glass body. The laser light is diffracted successively spirally downward by the respective holograms 15A-15D and is emitted outward from the last hologram if the laser light from the semiconductor laser 13 is projected thereto from diagonal above. The exit beam can be scanned in a direction A like arrows 101 103 by changing the wavelength of the semiconductor laser 13 at this time. The nonmechanical deflector which is capable of controlling the deflection angle simply by changing the oscillation wavelength is thereby obtd.

Description

[Detailed Description of the Invention] [Summary] Regarding an optical deflection device using a hologram, an object of the present invention is to provide a non-mechanical deflection device that can obtain a large deflection angle simply by changing the wavelength of a laser light source. , which has a wavelength tunable laser and a hologram module in which holograms are arranged radially about the central axis of the polygonal transparent body, and the transparent body has an entrance part that allows the beam from the wavelength tunable laser to enter the inside, and a hologram module. An output section is formed to output the beam deflected by the beam in a predetermined direction, and the deflection control is performed by changing the wavelength of the laser beam incident on the input section.

[Industrial application field]

The present invention relates to an optical deflection device, and particularly to a hologram deflection device that can control the deflection angle by simply changing the wavelength on the light source side without moving the lens.

[Conventional technology]

The light deflection device is generally a rotating polygon mirror, a vibrating mirror, or the like, which is operated by mechanically displacing the mirror using a motor or the like. There are also devices that use hologram scanners, but these are similar in that they mechanically move the hologram using a motor.

[Problem that the invention seeks to solve]

Deflection devices with such mechanically movable parts not only become larger in size, but also have problems with wear and lubrication of the movable parts, and control of the deflection angle depends on the mechanical precision of the mechanically movable parts. There are limits to how much improvement can be made.

Apart from this, deflection devices using solid-state elements such as acousto-optic elements have also been put into practical use, but there is a problem in that the deflection angle is small and their applications are limited.

The problem to be solved by the present invention is to eliminate the idea of moving a lens or mirror (mechanical deflection) and to realize a deflection device that can control the deflection angle non-mechanically.

Means for Solving Problem C] In order to achieve the above-mentioned problems, the deflection device according to the present invention includes a wavelength tunable laser and a hologram module in which holograms are arranged radially about the central axis of the polygonal transparent body. The transparent body is formed with an entrance part that allows the beam from the wavelength tunable laser to enter therein, and an exit part that allows the beam deflected by the hologram to exit in a predetermined direction,
The structural feature is that deflection control is performed by changing the wavelength of the laser beam incident on the incident section.

[For production]

Simply by deflecting the wavelength of the laser, the diffraction grating of the water gullogram changes, thereby making it possible to easily control the deflection angle of the laser beam by the hologram.

〔Example〕

FIG. 11 shows the diffraction characteristics of a hologram, which is the premise of the present invention, and is basically composed of a hologram lens 11 whose focal length is wavelength dependent and a wavelength variable laser 13. The hologram lens 11 is a well-known lens that condenses light using the diffraction effect of light, and has a large wavelength dependence. The hologram lens 11 is arranged to be inclined at a predetermined angle θ with respect to the optical axis X of the wavelength tunable laser beam 3. Therefore, by changing the wavelength of the laser beam incident on the hologram lens 11, the deflection angle of the hologram lens changes as shown in the figure.

The focal point can be scanned on the image plane M in the direction of the arrow. By utilizing the properties of the hologram lens in this manner, the present invention can realize a beam scanner by simply controlling the wavelength on the light source side without moving the hologram lens 11 at all. Note that if the present invention is simply applied as a deflection device and there is no need for convergent beam scanning, the hologram lens II does not need to be a lens, and may be a normal flat plate hologram with a plane wave grating (i.e., does not have a light focusing property). ) is fine.

The deflection angle is determined by the hologram placement angle θ,
In reality, a sufficient deflection angle cannot be obtained with a single hologram lens. Therefore, as shown in FIG. 12, the applicant of the present application previously arranged several flat holograms 15 (that is, not lenses) in a spiral shape, and created an optical system that enlarges the deflection angle each time the flat holograms 15 are passed. system (Japanese Patent Application No. 62-21892).

The present invention is directed to how to concretely realize a deflection device as shown in FIG. By embedding it in a unique arrangement, we succeeded in realizing a compact single hologram module (unit).

Figure 1.2.3 shows the basic structure of the present invention.

In FIG. 1, four flat plate (plane wave) holograms 15A to 15D are diagonally embedded in a rectangular glass body 21. By irradiating this with laser light from the semiconductor laser 13 from diagonally above, the laser light is sequentially diffracted downward into a spiral shape by each of the holograms 15A to 15D (
In the embodiment of FIG. 1, the light is emitted outward from the last hologram (hologram 15B in the embodiment of FIG. 1). At this time, by changing the wavelength of the semiconductor laser 13, the emitted beam can be scanned in the direction of arrow A as shown by 101→103.

This will be explained in more detail with reference to FIG. 2.3.

In FIG. 2, holograms 15A to 15 are orthogonally arranged.
Only D is extracted and shown. One hologram, for example, the hologram 15A, has an entrance part (non-hologram part) 31 in which no hologram is formed, and on the other hand,
The hologram 15C also has an output section 33 formed as a non-hologram portion. Preferably, the entrance part 31 is formed at the upper end of the hologram 15A, and the exit part 33 is formed at the lower end of the hologram 15C.

Incident part (non-hologram part) 3 of the first hologram 15A
A laser beam that is incident on the second hologram 15B from diagonally above the hologram 1 is first diffracted by the second hologram 15B toward the third hologram 15C (diffraction angle θ
, ), where it is diffracted by the fourth hologram 15D (diffraction angle θ2) and then diffracted by the fourth hologram 15D toward the first hologram 15A. Thereafter, diffraction is repeated in the same way. Each time the laser beam is diffracted, it travels downward in a spiral pattern, and in the illustrated embodiment, it is emitted from the emitting part (non-hologram part) 33 of the third hologram 15C after about two and a half turns. At this time, by changing the wavelength of the incident laser beam, the diffraction angle at each hologram changes, and the output beam can be scanned from 101 to 103.

Incidentally, instead of making the laser beam incident obliquely from above, at least one hologram, for example, the grating (diffraction grating) of hologram 15A, is formed by tilting at a predetermined angle Δθ with respect to the axis of symmetry (the central axis of the four holograms). You can.

By tilting the grating in this way, laser light that is perpendicularly incident on the end face of the rectangular parallelepiped is diffracted downward.

Note that the hologram that tilts the grating by Δθ may be any hologram, but preferably the hologram that first diffracts the incident beam (in the illustrated embodiment, the second hologram 15B0). (The grating of the first hologram 15A is shown tilted so that it can be clearly displayed) is preferable.

Figure 4.5 shows an example of a concrete hologram module.

In FIG. 4, four right-angled prisms 50 (right-angled triangular cross section) each having a height of 20 fins and a side of 0 fins are prepared, and hologram material is applied to two of them on surfaces that are at right angles to each other. Although PVCz (polyvinylcarbazole) is used as the hologram material, it is not limited to this material. A dragon grating 53 of f = 27.38 pieces/dragon was formed on this by holographic ink exposure. This is He-Cd
Two-beam interference (26,4
degree) or 441.6t+m of He −Cd
It was created using a laser (37.2° equicoherent). At this time, for one of the two right angle prisms forming the grating 53, the upper part of the grating surface is
11, and the lower part of the other grating surface is 5. T3 grating is not formed, and the entrance part 31 and the exit part 3
3 (Figure 5).

Next, the remaining two rectangular prisms 50 that do not form a hologram are sandwiched between the four prisms 50, as shown in FIG. 4, and the four prisms 50 are joined with adhesive to complete a rectangular parallelepiped hologram module.

6 shows a modified embodiment of FIG. 4, in which one hologram 53 is formed on one surface of each right-angle prism 50 forming a right angle. That is,
In the embodiment shown in FIG. 6, by joining four identical rectangular prisms 50 in the same manner as in FIG. 4, a hologram module completely equivalent to that in FIG. 4 can be obtained.

A laser beam having a diameter of 4 mm is incident on the hologram module shown in FIG. 4 (FIG. 7). The light source has a wavelength of 780n
A semiconductor laser whose wavelength can be changed by ±5 nm depending on the driving power source is used.

so that it first passes through the incident part 31 without a hologram,
Collimated light is incident at an angle of 22.8° to the vertical line X.

The beam is refracted by the glass (refractive index: 1.51) surface of the prism, and the beam is directed at an angle of 14.9° within the glass.

The beam within the glass is diffracted by the first hologram. In general, the angle θ diffracted by the mth hologram
6 is sinθ, =f(λ/n
) −cosθ---■ is given.

The diffraction angle changes θ,′ with respect to the wavelength fluctuation Δλ, and θ1=π
/4+θ5', the above equation can be approximated to the following equation.

Here, f (λ/n)=(T. From this, N is obtained.

Finally, when emitting light from the end face of the glass, the exit angle θ is θ = 5in-' (n sin θ1') according to Snell's law.
■It becomes.

For example, if a hologram is diffracted 8 times, Δ
λ=5nm; θ=5.9 as λ=78On+n
゜θ#8.9゜ is obtained.

The wavelength tunable laser 3 itself is well known. Although various wavelength tunable lasers (tunable lasers) are known, a semiconductor laser is used in this embodiment.

FIG. 8 shows another embodiment in which the present invention is applied to, for example, a laser printer. In the figure, a wavelength tunable laser light source 13
The emitted light beam from the hologram module 4 according to the present invention
0 is scanned along the recording drum 57 of the laser printer via the f-theta lens 55. Furthermore, f−θ
As is well known, the lens 55 is used to form a planar image of the scanning beam, which would normally form an arc as shown at 110. To obtain the deflection angle θ=60° from formulas ■ and ■, 0M'''19.3' = 0.34rnd −
Lt Therefore Δλ=16nm For N=12, Δλ=
When the thickness is 11 nm and N=16, the thickness may be 8.2 nm. Here, as N becomes larger, the efficiency for first use (η) deteriorates, but 1
Since efficiency of over 95% can be obtained with one hologram, N=
8, sufficient light efficiency can be obtained with η=66% or more.

FIG. 9 shows an embodiment in which a collimated beam is made incident on the hologram module 40 by a collimating lens 59, and the f-θ lens is omitted. In this case, the actual scanning line becomes an arc as described above, but by using an appropriate additional hologram, it is also possible to correct the arc-shaped imaging point as necessary and form a plane image. In FIG. 9, the hologram has a beam focusing function.

In FIG. 8, uniform speed scanning can be achieved by varying the amount of change in wavelength per time as shown in FIG. 10, that is, by controlling the wavelength sweep over time.

In addition to the above laser printer, the present invention can also be applied to barcode leagues, optical heads, etc.

〔Effect of the invention〕

As described above, according to the present invention, a non-mechanical deflection device can be obtained in which the deflection angle can be easily controlled simply by changing the oscillation wavelength. Also, since it is non-mechanical, there is no deterioration of the motor, etc. Holograms are easy to create and inexpensive hologram scanners can be obtained.

[Brief explanation of the drawing]

゛Fig. 1 is a diagram showing the basic configuration of the hologram deflection device according to the present invention, Fig. 2 is a diagram showing the basic principle of the invention, Fig. 3 is a diagram showing the deflection state of Fig. 2, and Fig. 4 is a diagram showing the deflection state of Fig. 2. FIG. 5 is an exploded plan view of the hologram module used in the present invention, FIG. 5 is an illustrative perspective view showing one right-angle prism, FIG. 6 is a view showing a modified embodiment of FIG. 4, and FIG. 7 is the same as FIG. FIG. 8 is a diagram showing an embodiment in which the present invention is applied to a laser printer. FIG. 9 is a diagram showing a modified embodiment of FIG. 8. FIG. 10 is a diagram showing a modified embodiment of FIG. FIG. 3 is a diagram showing an example of wavelength sweeping for constant velocity scanning. FIG. 11 is a diagram showing the basic principle of a hologram deflection device which is the premise of the present invention, and FIG. 12 is a diagram showing a hologram deflection device according to an earlier application by the applicant. 13... Tunable semiconductor laser, 15A, 15B, 15c, 15D... Hologram, 31... Incoming part, 33... Outgoing part, 40... Hologram module.

Claims (1)

[Claims] It has a wavelength tunable laser and a hologram module (40) in which holograms (15A to 15D) are arranged radially in a polygonal transparent body about its central axis, and the transparent body has a beam from the wavelength tunable laser inside. An entrance part (31) for making the laser beam enter the laser beam and an exit part (33) for making the beam deflected by the hologram go out in a predetermined direction are formed, and the deflection can be controlled by changing the wavelength of the laser beam incident on the entrance part. A hologram deflection device.