JPS62210429A - Optical scanner - Google Patents

Abstract

PURPOSE:To reduce the size and weight of an optical scanner, to eliminate the need for adjustments after assembly, and to obtain high-level reliability, etc., by providing an optical deflection part with an electrode which excites a surface acoustic wave and further equipping its driving circuit with a control circuit which changes the scanning motion of an image forming light spot into equal-speed linear motion. CONSTITUTION:Deflected light beams are refracted upward through a projection-side waveguide type lens 26 at right angles to the film surface of an optical waveguide 22 and converged on the image formation surface 34 of a photosensitive body 33. In this case, the driving circuit 30 is put in operation so as to form the image forming spot of the deflected light beams on the image formation surface 34 of the photosensitive body 33 in the equal-speed linear scanning state; and an acoustic wave frequency at this time is controlled accurately by a control circuit 32 and a scanning waveform correcting circuit 31. The angle of deflection of the light beams are proportional to variation in the driving frequency of a transducer 28 and variation in the frequency is controlled by varying an input voltage. For the purpose, the input voltage is controlled by a control circuit 32 to obtain the equal-speed linear scanning state of the image forming spot of the deflected light and the relation between the acoustic wave frequency and input voltage is controlled accurately by the scanning waveform correcting circuit 31 connected to the control circuit 32.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 1 The present invention relates to an acousto-optic optical scanner with integrated high resolution.

r Conventional Technology - An optical scanner used in router printers, copying machines, etc. includes a rotating polygon mirror that deflects light from a light source, and a photoreceptor, photoreceptor, etc. that deflects the light reflected by the polygon mirror. There is one that is constructed with an fO lens that converts constant angular velocity motion into uniform linear motion and focuses light on the imaging plane (surface) of .

In the case of such an optical scanner, each mechanical part is independent, and a predetermined interval between the mechanical parts is also required, which complicates assembly and precise adjustment and increases the size of the device.

In order to solve the above-mentioned drawbacks, a thin film waveguide type optical scanner using the acousto-optic effect shown in FIG. 5 has been proposed.

As is clear from FIG. 5, this optical scanner is
A laser diode 2 that emits guided light is provided at one end of the thin-film optical waveguide 1, and a collimator 3 that converts the guided light into parallel light extends from one end (light source side) to the other end of the guided waveguide l, and a collimator 3 that converts the guided light into parallel light. 5AW (Surf) that performs acousto-optic deflection
ace Acoustic Wave) transducer 4 and an imaging lens 5 for condensing guided light.

In FIG. 5, 6 is the optical deflection section of the leading waveguide 1, and 7 is the SA
W drive circuit; 8 is a sawtooth wave generation circuit; S is a photoreceptor (photoreceptor) arranged at a certain distance from the output end of the optical waveguide 1; 10 is an imaging plane (surface) of the photoreceptor 3; It is.

Note that the optical waveguide l is made of ZnO, LiNb0:+, LiT
The imaging lens 5 is made of a crystalline material such as a(h), and a thin film lens such as a mode index lens, a geodesic lens, or a Lunebrook lens is used as the imaging lens 5.

``Problems to be Solved by the Invention'' In the conventional optical scanner described above, the thin film lens described above is used as the imaging lens 5 that focuses light onto the imaging surface 1G of the photoreceptor 9, The locus of the image plane focal point on the image plane 10 is curved.

When the optical scanning band is narrow, the influence of the curvature phenomenon can be ignored, but when the optical scanning band is wide, the defocus becomes large.

In order to solve the problem of such a curvature phenomenon, in the optical scanner described above, the output end face 11 of the guiding waveguide 1 is processed into a circular shape. , it is difficult to curve the leading waveguide l itself, and since the sawtooth wave generating circuit 8 is used as the scanning control circuit of the optical deflection unit 8, the scanning movement of the optical imaging point is a function of the deflection angle Δθ. It changes non-linearly due to

Therefore, when a conventional optical scanner requires constant-velocity linear scanning interlocking, such as for a laser printer, special lenses such as the f-theta lens 13 are also required in addition to the cylindrical lens 12, but thin-film integration of these lenses is Due to this difficulty, it is difficult to miniaturize the entire device, and adjustments after assembly are unavoidable.

In view of the above-mentioned problems, the present invention has been devised to provide an assembly that satisfies the requirements of small size and light weight, no need for adjustment after assembly, and a high degree of reliability.
The aim is to provide a type of optical scanner.

In order to achieve the intended purpose, the optical scanner according to the present invention includes, from one end of the thin film optical waveguide to the other end, a waveguide lens for incidence, an optical deflection section, A waveguide lens for output is provided, a light source is coupled to the end of the thin film guide waveguide having the waveguide lens for input, and an electrode for exciting a surface acoustic wave is provided in the light deflection section. It is characterized in that the drive circuit is provided with a control circuit for making the scanning motion of the imaging light spot a uniform linear motion.

rEmbodiment j Hereinafter, one embodiment of the optical scanner of the present invention will be described with reference to one drawing.

In FIGS. 1 and 2 (A) and (B), 21 is a substrate;
22 is a thin S-type optical waveguide.

The optical waveguide 22 includes ZnO, LiNbO3, LiTa
Acousto-optic materials such as O3 are used.

For example, when ZnO is used as an acousto-optic material for an optical waveguide, the guiding waveguide 22 uses a glass plate or a sapphire plate as the substrate 21, and the optical waveguide layer is made of ZnO grown as a polycrystal or single crystal with C-axis orientation. (Waveguide film) 23
is formed on the substrate 21.

Reference numeral 24 denotes a light source consisting of, for example, a laser diode, and this light source 24 is coupled to one end of the optical waveguide 22 via a bonding means.

As another optical coupling method between the light source 24 and the optical waveguide 22, a method of making laser light from the outside enter the optical waveguide 22 via a grating coupler or the like can also be adopted.

Reference numeral 25 denotes an input waveguide lens provided at one end of the optical waveguide 22. The input waveguide lens 25 is made of an arbitrary lens such as a mode index lens, a geodesic lens, or a diffraction type lens. It has the function of collimating the light waves from 24 in parallel.

Reference numeral 26 denotes an output waveguide lens (imaging lens) provided at the other end of the optical waveguide 22. The output lens 28 is made of, for example, a hologram lens, and directs the guided light onto a spatial plane. It has the function of concentrating light.

The hologram lens in this case may be either a refractive index modulation type or a relief type.

27 denotes double waveguide lenses 25 and 26 in the optical waveguide 22.
This optical deflection section 27 is mainly composed of a transducer 28, and an ultrasonic absorber 29 is combined with this.

The transducer 28 has a function of exciting surface acoustic waves, and the ultrasonic absorber 29 has a function of canceling the influence of SAW reflection. A line segment connecting these transducer 28 and the ultrasonic absorber 29 makes a Bragg angle with the optical axis of the optical waveguide 22.

The entire upper surface of the optical waveguide layer 23 is covered with a transparent buffer material 40 having a refractive index lower than that of the optical waveguide layer 23, as shown in FIG. 2(A), or as shown in FIG. 2(B). , only the portion through which light passes is covered with a transparent buffer material 40.

Note that the waveguide lens (diffraction type) 25 and the waveguide lens 26 may be formed directly within the optical waveguide layer 23, but in such a relief type, an acousto-optic material (ZnO
, LiNbO3, etc.), a relief-type cladding lens 25.2B may be formed in the buffer layer portion on the surface of the optical waveguide layer.

30 is a drive circuit for the optical deflection section 27, 31 is a control circuit correction circuit (scanning waveform correction circuit), and 32 is a control circuit consisting of an arctangent wave generation circuit.

In the figure, 33 is a photoreceptor (photoreceptor) in a laser printer, a copying machine, etc., and 34 is an image forming surface of the photoreceptor 33.

In the embodiments shown in FIGS. 1 and 2 (A) and (B) described above, the light emitted from the light source 24 is incident on the leading waveguide 22, collimated in parallel by the incident waveguide lens 25, Thereafter, the light passes through the light deflection section 27 and the waveguide lens 26 on the output side, and then reaches the image forming surface 34 of the photoreceptor 33.

At this time, when an RF multiplied signal is applied to the transducer 28 of the optical deflection section 27, the SAW is excited due to the piezoelectric effect, and the SAW is caused to extend through the periodic structure 35 in the direction perpendicular to the electrode in the optical waveguide layer 23 due to the photoelastic effect. Creates a refractive index distribution.

Therefore, the light collimated in parallel by passing through the waveguide lens 25 is deflected in an angular direction that satisfies the Bragg condition by the refractive index distribution of the periodic structure 35, and the deflected light is directed toward the exit side. The light is bounced up in a direction perpendicular to the film surface of the optical waveguide 22 by the waveguide lens 2B, and is focused on the imaging surface 34 of the photoreceptor 33.

At this time, the drive circuit 30 is operated so that the imaging spot of the deflected light is in a constant speed linear scanning state on the imaging surface 34 of the photoreceptor 33, and the sonic frequency at this time is controlled by the control circuit 32. Accurate control is performed by the scanning waveform correction circuit 31.

As is known, the deflection angle Δθ of the light is proportional to the drive frequency change Δfs of the transducer 28, and the frequency change can be controlled by changing the input voltage.

Therefore, if the input voltage is controlled by the control circuit 32 consisting of an arctangent wave generating circuit, a constant velocity linear scanning state of the imaging spot by the polarized light can be obtained.

Furthermore, a scanning waveform correction circuit 31 connected to the control circuit 32
Accordingly, the relationship between the sound wave frequency fS and the input voltage V can be accurately controlled.

The scanning motion at the optical imaging point in this case will be considered below.

When the optical deflection angle is Δθ, the position y of the optical imaging point is given by the following equation (1).

V = fotanΔ(+ −−−−−−−−(1) f
o: Focal length of the imaging lens y: Distance from the optical imaging point to the optical axis When driven by a conventional sawtooth wave, the scanning movement dy/dt of the optical imaging point is as shown in equation (2) below. Become.

dy/dtsf osec2 Δ0 * d Δθ/d
t --------(2) Therefore, 5e in formula (2)
If C2Δθ·dΔθ/dt is set to a constant value, two uniform speed linear scans can be obtained.

In this case, the optical deflection angle Δθ is given by Δθ−tan−1(At).

If a scanning waveform circuit is configured such that the sound wave frequency ΔfS satisfies the following (3), the optical imaging point can be scanned in a straight line at a constant velocity.

ΔfS chant-/input eΔ0=Vs/λ・jan-1(At)” ” ” ” (3)
vs: Sound velocity input: Light wavelength in medium A: Constant t: Due to time or more, light passing through the optical waveguide 22
Light is simultaneously focused in directions parallel to and perpendicular to 2.
The light is focused into a substantially spot shape on the imaging plane 34.

FIG. 4 shows scanning waveforms corresponding to changes in sound wave frequency in the present invention and the conventional example, where the solid line in the figure is the present invention and the dotted line in the figure is the conventional example.

In addition, when increasing the scanning speed mentioned above, it is sufficient to combine a plurality of optical scanners in parallel with each other, and in such a case, the width of the light beam is reduced.

FIG. 3 shows a specific example of this case.

In the embodiment of FIG. 3, four laser diodes are used as the light source 24, but this may also be a laser diode array or a combination of a single laser diode and an optical splitter.

In the embodiment shown in FIG. 3, it is necessary to accurately set the signal for modulating each laser diode according to the propagation delay time of SAw of each transducer in order to bring adjacent scanning ranges closer together. Moreover, it is also necessary to adjust the period of the scanning waveform depending on the light emitted from each laser diode.

In this embodiment, by controlling the temperature of the entire optical scanner, fluctuations in the oscillation wavelength of the laser diode, fluctuations in the waveguide lens, etc. can be suppressed.

r) A light effect J As explained above, according to the present invention, a high-speed, high-resolution 11 optical scanner can be constructed compactly, lightweight, and inexpensively using a single thin-film waveguide, and moreover, it can be constructed using a special lens such as an f-theta lens. Since no adjustment is required after assembly, the 81-type structure exhibits a high degree of reliability.

[Brief explanation of drawings]

Figure 1 is a water-saving plan view of the optical scanner of the present invention, Figure 2 (A)
(B) is a water-saving side view of different embodiments of the optical scanner of the present invention, FIG. 3 is a water-saving plan view of another embodiment of the optical scanner of the present invention, and FIG. 4 is a scanning waveform corresponding to a change in sound wave frequency. The explanatory diagram, FIG. 5, is a water-saving plan view of a conventional optical scanner. 21・φ・Substrate 22... Optical waveguide 23... Optical waveguide layer (waveguide m> 24... Light source 25... Waveguide type lens (incidence side) 2B... Waveguide type lens (output side) side) 27...Light deflection section 28...Transducer 29...Ultrasonic absorber 30...Drive circuit 31 of the light deflection section...Control circuit correction circuit 32...Control circuit 33. ... Photoreceptor 34 ... Image forming surface 35 ... Periodic structure agent Patent attorney Yoshio Saito Figure 1

Claims (1)

[Claims] An input waveguide lens, an optical deflection section, and an output waveguide lens are provided from one end of the thin film optical waveguide to the other end, and an end portion of the thin film optical waveguide having the input waveguide lens. is coupled to a light source, the light deflection section is equipped with an electrode for exciting surface acoustic waves, and the drive circuit is equipped with a drive circuit for making the scanning motion of the imaging light spot a uniform linear motion. An optical scanner characterized by being provided with a control circuit.