JPH0495917A - Optical scanner - Google Patents

Abstract

PURPOSE:To obtain at least two scanning directions by one optical scanner by varying the driving frequency of a driving source and changing excitation modes. CONSTITUTION:A driving circuit vibrates the driving source 6 at certain frequency and its vibration is applied to an excitation part 5, which is vibrated reciprocally in an (x) direction. Then and inertial force operates on the scanning part 3 and an elastic deformation part 2 deforms elastically in the application direction of the inertial force with the internal force to vibrate. One of resonance frequencies is selected as the driving frequency of the driving source 6 to select one of two orthogonal scanning direction and a voltage applied to the driving source 6 is controlled to adjust the amplitude (x) of an excitation part 5, thereby controlling a scanning angle 2thetaT or 2thetaB. Consequently, a light beam can be put in scanning motion in >=2 directions by one scanner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical scanner that linearly scans a light beam in, for example, a laser printer or a barcode reader.

[Background Art] FIG. 9 shows the structure of a conventional optical scanner. This is an optical scanner using a polygon mirror 31, and a mirror surface 31 is provided on the outer peripheral surface of the polygon mirror 31 having a regular polygonal shape.
a, 31a, . . . are formed, and the polygon mirror 31 is rotated at a constant angular velocity by a DC servo motor 32 controlled by a driver circuit 35. Then, the laser beam α emitted from the semiconductor laser device 36
is focused by the imaging lens 33, and the polygon mirror 3
The mirror surface 31a of No. 1 is irradiated with light. Then, the laser beam α reflected by the mirror surface 31a of the polygon mirror 31
The light passes through the beam scan lens 34 and is irradiated onto the surface of the photosensitive drum 37, for example. Here polygon mirror 3
1 rotates at a constant angular velocity, the angle of the mirror surface 31a that is irradiated with the laser beam α changes, so the emission direction of the laser beam α reflected by the polygon mirror 31 changes, and the laser beam α changes. For example, the surface of the photosensitive drum 37 is scanned.

[Problem to be solved by the invention] However, this type of optical scanner requires a polygon mirror and a DC servo motor for rotational drive, so it is difficult to miniaturize the optical scanner. However, there was a limit to making the horns into one type. In addition, in order to accurately obtain the scanning width and scanning speed using an optical scanner, the precision of the dimensions of each mirror surface of the polygon mirror and the angle between each mirror surface is strictly required, which increases processing costs and assembly adjustment costs. It was expensive, and it was difficult to reduce the cost. Furthermore, since the scan angle of the laser beam is determined by the number of faces of the polygon mirror, the scan angle of each optical scanner is constant, and it has been impossible to change the scan angle.

Furthermore, in conventional optical scanners, the scanning direction of the laser beam is only one direction, and it is not possible to switch the scanning direction or scan in two directions simultaneously with one optical scanner.

The present invention has been made in view of the drawbacks of the conventional slanted scanner, and its object is to provide a small and inexpensive optical scanner based on a novel principle.

[Means for Solving the Problems] An optical scanner of the present invention includes an elastic deformation section having at least two elastic deformation modes, an excitation section provided at one end of the elastic deformation section, and an excitation section provided at one end of the elastic deformation section. A drive source is provided at the other end of the elastic deformation section to apply vibrations at a resonance frequency corresponding to the deformation mode to the vibrating section, and the drive source is provided at the other end of the elastic deformation section to cause elastic deformation in at least one of the elastic deformation modes when vibration is applied to the vibration section. It is characterized by comprising a scanning section which is arranged so as to elastically vibrate the section and can be rotated in at least two directions by the elastic vibration of the elastically deformable section, and a mirror surface provided on the scanning section.

[Operation] When vibration at a resonance frequency corresponding to a specific elastic deformation mode of the elastic deformation section is applied to the vibrating section, the elastic deformation section elastically vibrates in the elastic deformation mode, and the scanning section rotates in a specific direction. Therefore, when the mirror surface of the scanning section is irradiated with a light beam, the light beam reflected by the mirror surface is scanned by the rotation of the scanning section.

Moreover, since the elastic deformation section has at least two elastic deformation modes, when the excitation mode is changed by changing the drive frequency of the drive source, the rotation direction of the scanning section changes, and the scanning direction of the light beam changes. can be changed. Therefore, at least two scanning directions can be achieved with one optical scanner.

In addition, the scanning section, elastic deformation section, and excitation section can be formed into plate shapes, and a small actuator such as a piezoelectric vibrator can be used as the drive source, making the optical scanner ultra-small. Take it by doing it. Moreover,
Since the structure is simple, manufacturing costs, assembly adjustment costs, etc. are also low, and a low-cost optical scanner can be provided.

Furthermore, if the amplitude of the vibrating part is changed depending on the driving source,
It is possible to change the amplitude of elastic vibration in the elastic deformation section (the rotation angle of the scanning section), and it is also possible to adjust the scanning angle of the light beam.

[Example code] Hereinafter, one embodiment of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 shows an embodiment of the present invention. The optical scanner 1 includes a thin plate 7 and a small drive source 8, such as a piezoelectric vibrator or a magnetostrictive vibrator, that generates minute vibrations. The plate 7 has a shape as shown in FIG. 2 and FIG.
A vibrating section 5 for applying vibration from above is integrally provided, and a scanning section 3 for scanning a laser beam is integrally provided at the upper end of the elastic deforming section 2.

Here, the elastic deformation section 2 has a torsional deformation mode in which it is twisted and deformed around the axis P as shown in FIG. 2, and a bending deformation mode in which it is bent and deformed along the axis P as shown in FIG. The elastic vibration in the torsional deformation mode has a resonant frequency of fT, and the elastic vibration in the bending deformation mode has a resonant frequency of fa. The scan section 3 is formed in an unbalanced shape with respect to the axis P of the elastically deformable section 2, and the weight section 8 is formed in a portion away from the axis P of the elastically deformable section 2. therefore,
The center of gravity of the scanning section 3 is located away from the axis P of the elastically deformable section 2, and is further located above the upper end of the elastically deformable section 2. Further, a mirror surface 4 for reflecting a laser beam is formed in the scanning section 3. This mirror surface 4 may be formed on the entire scanning section 3 or may be formed partially, but in the embodiment shown in FIG. 1, it is provided in a portion near the axis P. The vibrating section 5 is fixed to the drive source 6 such as a piezoelectric vibrator by adhesion or bonding to the drive source 6, and the scanning section 3 is freely supported by the elastic deformation section 2.

The above-mentioned plate 7 is made by performing fine processing by etching or the like on a thin plate member such as a silicon wafer or a glass wafer with a smooth surface and good surface precision, and it is possible to mass-produce ultra-small plates 7. . Further, the mirror surface 4 of the plate 7 is also formed by etching a silicon wafer or the like, and the mirror surface 4 can be produced at a lower cost than by mirror processing.

A drive source 6 such as a piezoelectric vibrator that applies high-frequency vibration (for example, several hundred Hz) to the vibrating part 2 is controlled by a drive circuit, and has a resonance frequency fT in a torsional deformation mode or a resonance frequency f in a bending deformation mode. vibration is excited. What is shown in FIG. 7 is an example of this drive circuit 9,
an oscillator 10 that continues to apply a voltage signal with a frequency that matches the resonance frequency fT of the torsional deformation mode;
an amplifier 11 that amplifies the voltage signal output from the
An oscillator 12 that continues to output a voltage signal with a frequency that matches the resonance frequency fa of the bending deformation mode, and this oscillator 1
2, and a switch 14 for switching between the output voltage at frequency fT and the output voltage at frequency fB from the stage width amplifier 11.13 and applying the same to the drive source 6. has been done. Further, by switching the switch 14, it may be possible to apply to the drive source 6 a mixing signal in which the voltage signal of the frequency fT and the voltage signal of the frequency fB output from the stage width transducer 11.13 are superimposed. Moreover, if the switch 14 is placed between both vibration generators 10 and 12 and the amplifier, one amplifier can be used for the same purpose.

Moreover, what is shown in FIG. 8 is another drive circuit 15,
Voltage setting section 1G, voltage/frequency converter 17 and amplifier 1
It consists of 8. Based on an arbitrarily set drive axis command signal, the voltage setting unit 16 outputs Vl (or V2
), the voltage signal is converted by the voltage/frequency converter 17 to the corresponding frequency fT (or
fB) and voltage amplified by an amplifier 18, a signal having a resonant frequency fT (or fB) is applied to the drive source 6.

Although a sine wave is shown as the frequency signal in FIGS. 7 and 8, the same effect can be obtained by using a rectangular wave or a triangular wave.

Since the optical scanner 1 according to the present invention is configured as described above, the drive circuit causes the drive source 6 to vibrate at a certain frequency, and this vibration is applied to the vibrator 5, as shown in FIG. When reciprocatingly vibrates in the X direction, an inertial force acts on the scanning section 3, and this inertial force causes the elastic deformation section 2 to elastically deform and vibrate in the direction in which the inertial force is applied. Moreover, the driving frequency f applied to the vibrating section 5 is the resonance frequency fT of the torsional deformation mode or the resonance frequency fB of the bending deformation mode determined by the spring stiffness, moment of inertia, etc. of the elastic deformation section 2.
When it matches, the elastic vibration of the mode is amplified by the elastic deformation section 2, and the scanning section 3 is driven at a large rotation angle.

That is, the relationship between the drive frequency f and the rotation angle θ1 in the torsional deformation mode or the rotation angle θ8 in the bending deformation mode of the scanning section 3 is as shown in FIG. 4, for example. Figure 4 shows
It shows the relationship between the drive frequency f of the drive source 6 and the rotation angle of the scanning unit 3 when the two resonance frequencies are ft<fa, where the horizontal axis is the drive frequency f and the vertical axis is the torsional deformation of the scanning unit. The rotation angle θ7 of the mode or the rotation angle θ8 of the bending deformation mode is shown. As described above, the rotation angle θ in the torsional deformation mode reaches a maximum when the driving frequency f is equal to fT, and rapidly attenuates on both sides thereof. On the other hand, the rotation angle θ8 in the bending deformation mode is determined by the drive frequency f being fa.
It reaches a maximum when it is equal to , and rapidly decays on both sides.

Therefore, even if the driving source 6 is a piezoelectric vibrator that can only produce minute vibrations, it is possible to rotate the mirror surface 4 by a large angle by driving it at a frequency equal to the resonance frequency of each elastic deformation mode. I can do it.

Therefore, the resonant frequency fT of the torsional deformation mode is applied to the vibrating section 5.
When it is vibrated at
It is rotated around the axis P at a rotation angle of . At this time, as shown in FIG. 1, if the mirror surface 4 is irradiated with the laser beam α, the reflected laser beam α will be scanned at a scan angle 2θ7, which is twice the rotation angle θa of the scanning unit 3. Ru.

Therefore, as shown in FIG. 5, when the screen 1θ is irradiated with the laser beam α reflected by the optical scanner 1, the laser beam α is scanned left and right as shown in FIG. 6(a).

Furthermore, when the vibration part 5 is vibrated at the resonance frequency fa in the bending deformation mode, the vibration in the bending deformation mode is amplified in the elastic deformation part 2, and the scanning part 3 is moved at a rotation angle of θ8 as shown in FIG. It is rotated around a direction Q perpendicular to the axis P.

At this time, if the mirror surface 4 is irradiated with the laser beam α, the reflected laser beam α will be reflected at the rotation angle θ of the scanning unit 3.
Scanning is performed at a scan angle 2θ8 which is twice as large as 8. Therefore, when the screen 19 is irradiated with the reflected laser beam α from the optical scanner 1, the laser beam α is scanned vertically as shown in FIG. 6(b).

Further, when the driving source 6 vibrates the vibrating part 5 in a vibration mode in which the vibration with the resonant frequency fT of the torsional deformation mode and the vibration with the resonant frequency fa of the bending deformation mode are superimposed, the elastic deformation part 2 Since both the vibrations in the torsional deformation mode and the bending deformation mode are amplified, the scanning unit 3 generates vibrations at a rotation angle θ7 around the axis 2 and a rotation angle θ around the Q direction.
When the screen 1θ is irradiated with the laser beam α which is reflected by the scanning unit 3, the laser beam α is scanned in a planar manner as shown in FIG. 6(C).

Moreover, if the amplitude X of the vibrating part 5 is changed by adjusting the voltage applied to the driving source e while keeping the driving frequency f applied to the vibrating part 5 from the driving source 6 at one of the resonance frequencies, The rotation angle θ7 or θ8 of the scanning section 3 can be controlled.

In other words, the curve shown by the broken line in FIG. Rotation angle θ7. θ8 also increases.

Therefore, this optical scanner 1 selects one of the two orthogonal scanning directions by selecting one of the resonant frequencies as the drive frequency f of the drive source 6, and controls the voltage applied to the drive source 6. and the amplitude X of the vibrating part 5
Alternatively, the drive frequency f may be slightly changed, etc.), and the scan angle 2θ7 or 2θ8 can be controlled.

Note that the optical scanner of the present invention is not limited to the above embodiments, and various design changes can be made without departing from the technical idea of the present invention.

For example, in the above embodiment, the surface of the scanning section itself is a mirror surface, but a separate mirror plate with a mirror surface formed thereon may be adhered to the surface of the scanning section.

Further, the materials of the scanning part and the mirror surface are not particularly limited as long as the desired function can be obtained, and are not limited to those using silicon wafers or glass wafers as described above. Further, the drive source may be any actuator other than a piezoelectric vibrator, a magnetostrictive vibrator, etc., as long as it is capable of high-speed microvibration; for example, an actuator that generates microvibration using electrostatic force may be used. Further, the illustrated shape of the plate is merely an example, and the plate is not limited to the illustrated shape as long as it can obtain two or more types of elastic deformation modes.

Furthermore, in the above embodiment, two resonance frequencies f? and fa
were different values from each other, but these resonant frequencies ft
, fa can be arbitrarily set depending on the spring rigidity of the elastic deformation portion, the magnitude of the moment of inertia, the shape of the plate, etc., and the values of both resonance frequencies fT and fa may be made to match.

[Effects of the Invention] According to the present invention, an optical scanner based on a novel principle can be provided. In other words, the vibration of a drive source such as a piezoelectric vibrator can be converted into rotational motion of the scanning section by the elastic deformation section, and if a light beam is irradiated onto the mirror surface of the scanning section, the light beam will be reflected by the mirror surface. The light beam is scanned.

Moreover, since the elastic deformation section has at least two elastic deformation modes, if the excitation section is excited at the resonance frequency of either mode, the elastic deformation section can be elastically vibrated in that mode. , the direction of rotation of the scanning section can be changed.

Therefore, it is possible to create an optical scanner having scanning directions of two or more axes, and it is possible to scan a light beam in two or more directions with one optical scanner.

Further, the optical scanner can be made into a standard shape, and an inexpensive optical scanner can be provided.

Furthermore, by adjusting the amplitude of the vibrating section, the rotating angle of the scanning section can be changed, and the light beam can be scanned at a free scanning angle with one optical scanner.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a perspective view showing the torsional deformation mode of the same plate, FIG. 3 is a perspective view showing the bending deformation mode of the same plate, and FIG. is a diagram showing the relationship between the driving frequency and the rotation angle of the scanning section,
FIG. 5 is a perspective view showing how a laser beam is irradiated onto a screen by the optical scanner of the present invention, and FIG.
) (b) (c) are diagrams showing the locus of the laser beam being scanned on the screen in each mode, Figure 7 is a block diagram showing the drive circuit for driving the same drive source, and Figure 8 is FIG. 9 is a block diagram showing the other side of the drive circuit for driving the same drive source as above, and FIG. 9 is a perspective view showing a conventional example. 2...Elastic deformation part 3...Scanning part 4...Mirror surface 5...Vibration part 6...Drive source patent applicant OMRON Co., Ltd. agent Patent attorney Masafusa Nakano Figure 5 No. 61!1 (b) (C) No. 7 No. 81!1 Figure a9 March 18, 1991

Claims (1)

[Claims] (1) an elastic deformation section having at least two elastic deformation modes; an excitation section provided at one end of the elastic deformation section; and a vibration at a resonant frequency for each elastic deformation mode of the elastic deformation section applied to the excitation section. a drive source provided at the other end of the elastic deformation section and arranged to elastically vibrate the elastic deformation section in at least one of the elastic deformation modes when vibration is applied to the vibrating section; An optical scanner comprising: a scanning section that can rotate in at least two directions by elastic vibration; and a mirror surface provided on the scanning section.