JPH04257821A - Optical scanner - Google Patents

Abstract

PURPOSE:To increase the scanning angle and scanning width of a light beam without increasing the amplitude of an elastic deformation part as to the optical scanner which turnes a scanning part at a certain angle of turning by utilizing the vibration of resonance frequency of the elastic deformation part provided to a plate and irradiates the mirror surface of the scanning part with the light beam for scanning. CONSTITUTION:The scanning part 3 provided at one end of the elastic deformation part 2 is provided with the mirror surface 4 and a reflecting mirror 15 is arranged opposite the mirror surface 4. The scanning part 3 is turned at the angle theta by vibrating an excitation part 5 and the mirror surface 4 is irradiated with the light beam alpha; and the light beam is reflected by the reflecting mirror 15 and reflected again by the mirror surface 4, thereby making a scan with the light beam alpha projected from the optical scanner at the scanning angle 4 theta.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical scanners. Specifically, the present invention relates to an optical scanner that scans a light beam in, for example, a laser printer or a barcode scanner.

0002

2. Description of the Related Art FIG. 8 shows a schematic diagram of a conventional optical scanner 31 used in a laser printer. This is an optical scanner 31 using a polygon mirror 32, and each outer peripheral surface of the polygon mirror 32 having a regular polygonal shape has a mirror surface 3.
3, 33, . . . are formed, and the polygon mirror 32 is rotated at a constant angular velocity by a servo motor. The laser beam α emitted from the semiconductor laser device 34 is irradiated onto the mirror surface 33 of the polygon mirror 32. The laser beam α reflected by the mirror surface 33 passes through the intermediate optical system 35 and is irradiated onto the surface of the photosensitive drum 36, for example. Here, when the polygon mirror 32 is rotating at a constant angular velocity, the angle of the mirror surface 33 that reflects the laser beam α changes, so the emission direction of the laser beam α reflected by the polygon mirror 32 changes, For example, the surface of the photosensitive drum 36 is scanned with the laser beam α.

[0003] Furthermore, in the optical scanner 31, it is necessary to detect the timing of the start and end of scanning of the laser beam α. element 37,
38 is arranged so that the start point of one scan is detected when the laser beam α is incident on one of the light receiving elements 37, and the end point of one scan is detected when the laser beam α is incident on the other light receiving element 38. It had become.

0004

[Problems to be Solved by the Invention] However, since these types of optical scanners use polygon mirrors, motors, etc., it has been difficult to make them compact and downsized. Furthermore, the scanning direction of the laser beam is limited to only one direction, and the scanning angle of the laser beam is constant, making it impossible to vary the scanning width.

Furthermore, in the above optical scanner, light receiving elements are placed at both ends of the scanning range of the laser beam in order to detect the timing of the start and end of laser beam scanning. There was a problem that the width) became smaller. Further, it is only possible to detect the timing of the start and end of scanning, but it is not possible to know the scanning position of the light beam in the area between the start and end of the operation. Therefore, it is necessary to improve the scanning accuracy of the optical scanner and the scanning reproducibility within the scanning range, which increases the cost of polygon mirrors, drive motors, etc.

The present invention has been made in view of the drawbacks of the conventional examples described above, and its objects are to provide a compact optical scanner with a variable scanning area, and an optical scanner that can change the intermediate scanning position in the scanning area. An object of the present invention is to provide an optical scanner that is capable of detection and has a large effective scanning width.

[0007]

[Means for Solving the Problems] A first optical scanner of the present invention includes an elastic deformation section having at least one elastic deformation mode, an excitation section provided at one end of the elastic deformation section, and the elastic deformation section. a driving source for applying vibrations at a resonant frequency to the elastic deformation mode to the vibrating section; a scanning section arranged to cause the elastic deformation section to vibrate elastically, and capable of rotating in at least one direction by the elastic vibration of the elastic deformation section;
It is characterized by consisting of a mirror surface provided in the scanning section and a reflecting mirror provided at a position facing the mirror surface of the scanning section.

Further, the second optical scanner of the present invention includes an elastic deformation section having at least one elastic deformation mode, an excitation section provided at one end of the elastic deformation section, and an elastic deformation mode of the elastic deformation section. a driving source for applying vibrations at a resonant frequency to the vibrating part; A scan section arranged to vibrate elastically and can rotate in at least one direction by the elastic vibration of the elastic deformation section, a mirror surface provided on the scan section, and a mirror surface provided at a position facing the mirror surface of the scan section. A semi-transmissive plate that reflects a part of the light beam and transmits a part of the light beam, and a light beam detection unit that detects either the light beam reflected by the semi-transmissive plate or the transmitted light beam. It is characterized by consisting of means.

[0009]

[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 vibrates elastically 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.

[0010] The scanning section, the elastic deformation section, and the excitation section can be formed into plate shapes, and a small actuator such as a piezoelectric vibrator can be used as the driving source, and a reflecting mirror can be added to this. The optical scanner can be made ultra-small. In addition, the scanning direction can be changed by applying vibrations with resonance frequencies of different elastic deformation modes to the vibrating part, and furthermore, if the amplitude of the vibrating part is changed by the drive source, the elastic vibration in the elastic deformation part can be changed. The amplitude (scan angle) of the light beam can be changed, and the scanning width of the light beam can also be adjusted.

Furthermore, in the first optical scanner, since the reflecting mirror is placed opposite to the mirror surface of the scanning section, the light beam reflected by the mirror surface is reflected by the reflecting mirror.
The light beam can be reflected more than once on the mirror surface,
As a result, it is possible to obtain a wide scan angle that is four times or more the rotation angle of the elastically deformable portion, and it is possible to provide a large scanning width.

In addition, in the second optical scanner, the light beam reflected by the mirror surface is partially transmitted and partially reflected by the semi-transparent plate, so that one of the transmitted light and reflected light is used for scanning. The other light beam can be used for scanning position detection. Therefore, by monitoring the direction of the light beam for scanning position detection, the scanning position can be accurately determined even in the intermediate region between the start and end of scanning with the light beam. Further, unlike the conventional example in which a light beam is directly detected by a light receiving element, the effective scanning width does not have to be made small, and a wide effective scanning width can be provided.

Furthermore, in the second optical scanner, the light beam reflected by the semi-transparent plate is reflected again by the mirror surface, and the light beam reflected twice or more by the mirror surface is used for scanning. If the light beam detection means detects the light receiving position of the transmitted light from the plate, the scanning light beam can be provided with a wide scanning width while the scanning position is monitored by the light beam detection means. Conversely, if the light beam reflected by the semi-transmissive plate and the mirror surface is detected by the light beam detection means and the transmitted light of the semi-transmissive plate is used for scanning, the detection accuracy or resolution of the scanning position can be improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows an optical scanner 1 according to an embodiment of the present invention. This optical scanner 1 includes a thin plate 7 and a small drive source 6 that generates minute vibrations such as a piezoelectric vibrator or a magnetostrictive vibrator.
It is composed of. The plate 7 is shown in FIGS.
), a vibrating part 5 for applying vibrations from a drive source 6 is integrally provided at the lower end of the long narrow elastic deforming part 2, and a , a scanning section 3 for scanning a laser beam is integrally provided. Here, the elastic deformation section 2 has two modes: a torsional deformation mode in which the elastic deformation section 2 undergoes twisting deformation around the axis P, as shown in FIG. 3(a), and a bending deformation mode 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 fB. 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. A reflecting mirror 15 is arranged and fixed at a position facing this mirror surface 4 so as to face each other. 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.

[0015] High frequency vibration (for example, several hundred
A drive source 6, such as a piezoelectric vibrator, which applies Hz) is controlled by a drive circuit, and is excited to vibrate at a resonance frequency fT in a torsional deformation mode or a resonance frequency fB in a bending deformation mode. What is shown in FIG. 5 is an example of this drive circuit 9, which includes an oscillator 10 that continues to output a voltage signal of a frequency that matches the resonance frequency fT of the torsional deformation mode,
An amplifier 11 that amplifies the voltage signal output from the oscillator 10, an oscillator 12 that continues to output a voltage signal with a frequency that matches the resonance frequency fB of the bending deformation mode, and a voltage signal that is output from the oscillator 12. and a switch 14 for switching between the output voltage of frequency fT and the output voltage of frequency fB from both amplifiers 11 and 13 and applying the same to the drive source 6. Furthermore, by switching the switch 14, both amplifiers 11
, 13 and the voltage signal of frequency fT output from
A mixing signal on which the voltage signal B is superimposed may be applied to the drive source 6. In addition, the switch 14
If it is placed between both oscillators 10, 12 and the amplifier, one amplifier can be used.

Since the optical scanner 1 according to the present invention is configured as described above, the driving circuit 9 vibrates the driving source 6 at a certain frequency, and this vibration is applied to the vibrating section 5 to generate the image 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 f of the bending deformation mode determined by the spring stiffness, moment of inertia, etc. of the elastic deformation section 2.
If it matches B, the elastic vibration of the relevant mode will cause the elastic deformation part 2
is amplified, and the scanning unit 3 is rotated greatly. That is, the rotation angle of the scanning unit 3 in the torsional deformation mode (rotation angle around the axis P in FIG. 3(a)) θT or the rotation angle in the bending deformation mode (the rotation angle in FIG. 3(b)) The relationship with the rotation angle (angle of rotation around the axis Q) θB is as shown in FIG. 4, for example. FIG. 4 shows the relationship between the drive frequency f of the drive source 6 and the rotation angles fT and fB in two directions of the scanning unit 3 when the two resonance frequencies fT<fB, and the horizontal axis represents the drive frequency. f, the vertical axis indicates the rotation angle θT in the twisting deformation mode or the rotation angle θB in the bending deformation mode of the scanning section 3. As described above, the rotation angle θT 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 θB in the bending deformation mode reaches a maximum when the driving frequency f is equal to fB, and rapidly attenuates on both sides thereof.

Therefore, even if the driving source 6 is a piezoelectric vibrator that can only produce minute vibrations, by driving it at a frequency equal to the resonance frequency fT or fB of each elastic deformation mode, the mirror surface 4 can be 3(a), or around the axis Q as shown in FIG. 3(b). Furthermore, 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 fB of the bending deformation mode are superimposed, the elastic deformation part 2 Since both vibrations in the torsional deformation mode and the bending deformation mode are amplified at the same time, in the scanning unit 3, vibrations at a rotation angle θT around the axis P and vibrations at a rotation angle θB around the Q direction are combined. Moreover, if the amplitude X of the vibrating part 5 is changed by adjusting the voltage applied to the driving source 6 while keeping the driving frequency f applied to the vibrating part 5 from the driving source 6 at one of the resonance frequencies, Rotation angle θT of scanning section 3
Alternatively, θB can be controlled. That is, the curve shown by the broken line in FIG. 4 is the case where the vibrating part 5 is vibrated with a larger amplitude X than the curve shown by the solid line, and as the amplitude x of the vibrating part 5 increases, the scanning part 3 rotation angle θT
, θB also increases.

Now, as shown in FIG.
When a point is irradiated with a laser beam α, the laser beam α reflected at a point A on the mirror surface 4 enters a point B on the opposing reflecting mirror 15, and the laser beam α reflected by the reflecting mirror 15 returns to the mirror surface 4. Suppose that the light is guided and reflected at point C. At this time, as shown in FIG. 1, when the elastic deformation section 2 is vibrated in one of the above deformation modes and the scanning section 3 is rotated at a rotation angle of Δθ, the light is reflected at point A on the mirror surface 4. The laser beam α is scanned at a scan angle 2Δθ, which is twice the rotation angle Δθ of the scanning unit 3, and the laser beam α reflected at point B of the reflecting mirror 15 is scanned at an angle of 2Δθ, and is again scanned at a point C on the mirror surface 4. The laser beam α reflected by is scanned at an angle of 4Δθ. That is, the scan angle 4 is twice the scan angle 2Δθ when the reflector 15 is not used.
Δθ can be obtained, and the scan angle can be easily amplified with a simple configuration of just adding the reflecting mirror 15.

Furthermore, since the elastic deformation section 2 has a thin shaft shape as shown in FIG. 1, if the amplitude of the elastic deformation section 2 is too large and the scan angle is increased, the elastic deformation section 2 will be destroyed. However, in the present invention, the scanning angle can be optically increased using a reflecting mirror, so the amplitude of the elastic deformation section 2 can be suppressed to an appropriate level, and the durability of the optical scanner can be improved. can improve sex.

Although the laser beam α is reflected twice by the mirror surface 4 in FIG. 2, the number of reflections is not limited to two. For example, if the laser beam α is reflected three times on the mirror surface 4 using the reflecting mirror 15, then 4×2Δ
If a scan angle of θ is obtained and it is reflected 4 times, 8×2Δ
A scan angle of θ can be obtained, and the number of reflections can be set arbitrarily. Furthermore, although the method for fixing or supporting the reflecting mirror is not illustrated, there is no particular limitation as long as the object of the present invention can be achieved, and any suitable structure may be adopted depending on the usage conditions. can. Furthermore, the same applies to the material, shape, number, etc. of the reflecting mirrors.

Although not shown, as a different embodiment of the present invention, the reflecting mirror may be made movable so that its relative position with respect to the mirror surface can be adjusted. By adjusting the relative position of the reflector, the direction of the scan center axis (laser beam emission direction when not being scanned) can be changed, so the scan direction can be adjusted without changing the orientation of the optical scanner. This is effective, for example, in adjusting the optical axis.

FIG. 6 shows an optical scanner 1 according to another embodiment of the present invention.
6 is shown. In this optical scanner 16, a semi-transmissive plate 17 is disposed at a position facing the mirror surface 4 of the scanning unit 3, and transmits a part of the laser beam α and reflects a part of the laser beam α.
A optical position detection device (PSD) 18 is arranged in the transmission direction of the laser beam from the semi-transparent plate 16.

Now, as shown in FIG.
Suppose that a point is irradiated with a laser beam α. Mirror surface 4
The laser beam α reflected at point A of
7, a part of the light passes through the semi-transparent plate 17 and enters the optical position detection element 18 as monitor light α2, and the light receiving position is detected by the optical position detection element 18. Further, a part of the laser beam α incident on point B of the semi-transmissive plate 17 is reflected by the semi-transmissive plate 17, guided to the mirror surface 4 again, and reflected again at point C. At this time, as shown in FIG. 6, the elastic deformation section 2 is vibrated in one of the deformation modes, and the scanning section 3
is rotated at a rotation angle of Δθ, the angle of A of the mirror surface 4 is
The laser beam α reflected at the point has a rotation angle Δ of the scanning unit 3.
The laser beam α scanned at a scan angle 2Δθ which is twice that of θ, reflected at the point B of the semi-transmissive plate 17, is scanned at an angle of 2Δθ, and the laser beam α1 reflected again at the point C of the mirror surface 4 has a scanning angle of 4Δθ. scanned at an angle. If this laser beam α is used for scanning, a wide scanning width can be obtained. Further, the monitor light α2 transmitted through the semi-transparent plate 17 changes its emission direction at an angle of 2Δθ, and furthermore,
Since it is synchronized with the scanning direction of the scanning laser beam α1, the light receiving position of this monitor light α2 is detected by the optical position detecting element 18, and the change in the light receiving position is detected by the optical position detecting element 18.
By outputting the voltage as a voltage output, it is possible to know the arbitrary scanning position of the scanning laser beam α1 as an electric signal.

Furthermore, in the above embodiment, the optical position detection element detects the light beam transmitted through the semi-transparent plate.
On the contrary, the light beam transmitted through the semi-transmissive plate is used for scanning, and the light beam reflected by the semi-transmissive plate and then reflected again on the mirror surface is used for monitoring and detected by an optical position detection element. good. In this way, the change in the light receiving position on the optical position detection element can be increased, so even if the optical position detection element is brought close to the mirror surface, high scanning position detection accuracy can be obtained, and the optical scanner can be made compact.

In the embodiments shown in FIGS. 6 and 7 as well, the reflected light from the semi-transmissive plate may be used to cause the light to be reflected three or more times on the mirror surface. In this case, since the transmitted light from the semi-transparent plate is obtained from multiple locations, it is sufficient to provide an optical position detection element at one of the locations. Further, the shape, material, transmittance, etc. of the semi-transparent plate are not particularly limited as long as they can achieve the purpose of the present invention. Further, the light beam detection means may be any device as long as it can detect the light receiving position or incident position, and is not limited to the above-mentioned optical position detection element, but may also include a multi-division photodiode or a charge-coupled device (CCD).
) etc. may be used. Further, the mounting position and direction of the light beam detection means are not particularly limited, and can be determined as appropriate depending on the usage conditions.

It should be noted that the optical scanner of the present invention is not limited to the above-mentioned 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 having a mirror surface formed thereon may be adhered to the surface of the scanning section. In addition to the piezoelectric vibrator and the magnetostrictive vibrator, the drive source may be any actuator capable of high-speed microvibration; for example, an actuator that generates microvibration using electrostatic force may be used. Furthermore, in the above embodiment, the two resonance frequencies fT and fB were different from each other, but these resonance frequencies fT and fB can be changed arbitrarily depending on the spring stiffness of the elastic deformation part, the magnitude of the moment of inertia, the shape of the plate, etc. , and the values of both resonance frequencies fT and fB may be made to match.

Further, in the above embodiment, an optical scanner of a type that scans a laser beam in two directions has been described, but the present invention is disclosed in, for example, Japanese Patent Application No. 2-209803 (filing date: August 7, 1990). It can also be applied to a type of optical scanner that scans a light beam in only one direction, such as the one for which a patent application has been filed.

[0028]

According to the present invention, it is possible to manufacture an ultra-miniaturized optical scanner that can change the scanning direction and scanning width (or scan angle) of a light beam.

Furthermore, in the first optical scanner, the scan angle of the light beam can be amplified by the reflecting mirror, and a wide scan angle that is more than four times the rotation angle of the elastic deformation part can be obtained, and a large scan angle can be obtained. The light beam can be scanned across the width.

In addition, in the second optical scanner, a part of the light beam is reflected by a semi-transmissive plate and a part is transmitted, dividing the light beam into one for scanning and one for detecting the scanning position. It is possible to accurately detect the scanning position even in any region between . Therefore, an optical scanner with high precision and good reproducibility is not required, and costs can be reduced. Furthermore, the effective scanning width of the light beam is not narrowed, and the scanning range of the optical scanner can be utilized to the fullest.

Furthermore, in the second optical scanner, if the light beam reflected twice or more on the mirror surface is used for scanning, and the light transmitted through the semi-transparent plate is used for detecting the receiving position, the scanning position can be continuously changed. Not only can it be monitored, but also the scanning width of the light beam can be widened. On the other hand, if the light beam reflected twice or more on the mirror surface is used for detecting the light receiving position and the light transmitted through the semi-transparent plate is used for scanning, the detection accuracy or resolution of the scanning position can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an optical scanner according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation of the above embodiment.

FIG. 3(a) is a perspective view showing a torsional deformation mode of the plate in the above embodiment, and FIG. 3(b) is a perspective view showing a bending deformation mode of the plate.

FIG. 4 is a diagram showing the relationship between the driving frequency and the rotation angle of the scanning section.

FIG. 5 is a block diagram showing a drive circuit for driving a drive source in the embodiment.

FIG. 6 is a perspective view showing another embodiment of the invention.

FIG. 7 is an explanatory diagram of the operation of the above embodiment.

FIG. 8 is a schematic plan view showing a conventional example.

[Explanation of symbols]

2 Elastic deformation part 3 Scan section 4 Mirror surface 5 Vibration part 6 Drive source 15 Reflector 17 Semi-transparent plate 18 Optical position detection element

Claims (2)

[Claims] 1. An elastic deformation section having at least one elastic deformation mode; an excitation section provided at one end of the elastic deformation section; a driving source for applying the elastic deformation; and a drive source provided at the other end of the elastic deformation section, 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; The scanner comprises a scanning section that can rotate in at least one direction by elastic vibration of the scanning section, a mirror surface provided on the scanning section, and a reflecting mirror provided at a position facing the mirror surface of the scanning section. Features an optical scanner. 2. An elastic deformation section having at least one elastic deformation mode; an excitation section provided at one end of the elastic deformation section; a driving source for applying the elastic deformation; and a drive source provided at the other end of the elastic deformation section, 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; A scanning section that can rotate in at least one direction by elastic vibration of the scanning section, a mirror surface provided in the scanning section, and a part of the light beam provided at a position facing the mirror surface of the scanning section. A light beam characterized by comprising a semi-transmissive plate that reflects and partially transmits the light, and a light beam detection means that detects either the light beam reflected by the semi-transmissive plate or the transmitted light beam. scanner.