JPH11351819A - Optical scanning device with scanning position detecting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical scanning device which can detect a scanning position with high resolution and high precision and has simple and inexpensive constitution as an optical scanning device which uses a resonance type deflecting means. SOLUTION: The optical scanning device which scans an observed body 15 by deflecting the light beam from a light source means 11 for scanning by a resonance type galvanomirror 13 projects the light from a light source 31 for position detection on a 1st Ronchi grating 32 and projects the image of the Ronchi grating on a 2nd Ronchi grating 35 through a zoom lens 33, the reverse surface of the galvanomirror 13, and a lens 34 so as to detect the scanning position. Moire fringes are formed by making slightly different the grating pitch of the 2nd Ronchi grating 35 and the grating pitch of the 1st Ronchi grating 33 and the movement of the moire fringes is detected by 1st to 4th photodetectors 36A to 36D. The moire fringes increase the movement quantity of the galvanomirror 13, so high resolution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device for scanning by periodically deflecting a light beam emitted from a light source, and more particularly to a scanning light source for emitting a scanning light beam. The present invention relates to an optical scanning device including a resonance type light deflecting unit for deflecting the scanning light beam and projecting the scanning light beam on a scanning surface, and having a function of detecting a position scanned by the scanning light beam.

[0002]

2. Description of the Related Art Various types of optical scanning devices have been proposed in which scanning is performed by periodically deflecting a scanning light beam. For example, there has been proposed an optical scanning device in which a laser beam emitted from a laser light source is passed through a photo-acoustic deflecting element, and a sawtooth drive signal is supplied to the element to deflect the beam. In such an optical scanning device,
Information on the scanning position by the light beam can be extracted from the sawtooth drive signal for driving the photo-acoustic conversion element. However, an optical scanning device using such a photo-acoustic deflection element has a problem in that the usable wavelength is limited. For example, those using lead molybdate or tellurium dioxide have extremely low transmittance for light with wavelengths shorter than 450 nm and 380 nm, and those using quartz transmit light with shorter wavelengths, but have a very low figure of merit. There is a problem. Further, there is a problem that fluctuations due to temperature changes of the photo-acoustic deflection element and its driving circuit are large.

On the other hand, there has also been proposed a mechanical optical scanning device which receives a light beam emitted from a light source and vibrates and deflects a reflecting mirror which reflects the light beam toward a predetermined scanning surface. In an optical deflector using such a reflection mirror, the scanning speed is not constant over the scanning range, but is generally slow at both ends of the scanning range and fastest at the center. When there is such scanning unevenness, when a grid pattern as shown in FIG. 1A is scanned, when an image signal obtained by scanning is displayed, the pitch of the grid is shifted from the edge of the screen toward the center as shown in FIG. 1B. Will be smaller. In order to eliminate such scanning unevenness, the angular position of the reflection mirror is electrically detected by, for example, a sliding resistor having an arm attached to the output shaft of a servomotor, and servo control is performed based on the electrical detection. In this way, scanning is performed accurately. However, in such an optical scanning device, the repetition frequency of scanning is limited to about several hundred Hz from the viewpoint of the response speed of servo control, and it is not possible to perform scanning at a higher speed.

Further, a so-called resonance type galvano scanner has been proposed as an optical scanning device capable of performing high-speed scanning. In such an optical scanning device, for example, a sinusoidal drive signal from an oscillator is caused to flow through a coil of an electromagnetic drive element constituting a mechanical resonance system together with a torsion bar, and a mirror fixed to the torsion bar is periodically moved. I make it vibrate. In this resonance type galvano scanner, servo control is not performed.
Hz high-speed scanning is possible. However, since the phase of the drive signal and the vibration position do not match, even if the drive signal is processed, the scanning position cannot be known, and the scanning unevenness described above with reference to FIG. 1 cannot be eliminated.

[0005]

In the above-mentioned resonance type galvano scanner, various mechanisms have been proposed for extracting scanning position information by a light beam. FIG. 2 shows an example of a conventional optical scanning device having such a scanning position detecting function. The scanning light beam emitted from the light source means 11 is reflected by a galvanomirror 13 oscillated at a predetermined frequency by an electromagnetic driving means 12 and is projected on an object 15 to be observed by a condenser lens 14. Scanning. This scanning is usually called main scanning,
The sub-scanning in the direction orthogonal to the main scanning direction can be performed, for example, by moving a stage that holds the object 15 to be observed.

The light beam transmitted through the object under observation 15 is made incident on a photodetector 17 by an objective lens 16, and a signal representing the optical characteristics of the object under observation is output from the photodetector. For example, an image signal representing video information of the observed object 15 is written to a frame memory 19 via an amplifier 18. As described above, in such a resonance type galvano scanner, the scanning speed by the light beam is not uniform over the entire main scanning width, but is changing. Needs to correspond to the scanning position of the object 15 to be observed, and for that purpose, it is necessary to detect the scanning position by the light beam.

In the conventional scanning apparatus shown in FIG. 2, in order to detect a scanning position by a light beam, a light source means 20 for emitting a light beam for scanning position detection is provided, and this light beam is applied to a galvanomirror. The light is reflected by the rear surface of the Ronchi grating 13 and is incident on a Ronchi grating 21. The light beam transmitted through the Ronchi grating is received by a light receiver 22. In the Ronchi grating 21, the width of the opening is equal to the width of the light shielding portion. Therefore, the amount of light transmitted through the Ronchi grating 21 is changed according to the deflection of the scanning position detecting light beam by the galvanomirror 13. It will change almost sinusoidally. The light beam for detecting the scanning position is reflected by the galvanomirror 13, and its deflection state corresponds to the deflection state of the scanning light beam projected on the observed object 15 in a one-to-one correspondence. Therefore, by processing the output signal of the light receiver 22 by the signal processing means 23 including the waveform shaping circuit, it is possible to detect information indicating the scanning position of the scanning light beam. By generating a write signal for the frame memory 19 based on this scanning position information, it is possible to write an image signal at a predetermined pixel position while compensating for fluctuations in the vibration speed of the galvanometer mirror 13.
By displaying the image signal read out from the monitor 9 on the monitor 24, it is possible to display an accurate image which is not affected by uneven scanning of the galvanomirror 13.

The conventional optical scanning apparatus shown in FIG. 2 has the advantage that the accuracy of the position detection signal is high, but has the problems that the resolution of position detection is low and the direction of change in the scanning position cannot be determined. Here, in order to improve the resolution of position detection, it is conceivable to multiply a pulse signal obtained by processing the output signal of the light receiver 22, but the period of this pulse signal is reduced due to the aforementioned scanning unevenness. Since it changes, it is troublesome to perform accurate multiplication, and a complicated circuit is required.

FIG. 3 shows another example of a conventional optical scanning device using a resonance type deflecting means. The same parts as those of the optical scanning device shown in FIG. Is omitted. In this conventional example, in order to detect the scanning position information of the light beam, the light beam for scanning position detection emitted from the light source means 20 is reflected by the back surface of the galvanometer mirror 13 and then constituted by a semiconductor element. To a position detecting device (PSD: Position Sensing Device) 25, which supplies an output signal from the position detecting device to an analog operation unit 26, and outputs an output signal from the analog operation unit to a signal including an A / D converter. The write address signal is supplied to the processing unit 27 and compensated by the scanning position information of the light beam, and the timing of writing the image signal to the frame memory 19 is controlled based on the write address signal.

In such a conventional optical scanning device,
By using a high-precision position detection device 25, the resolution of position detection can be increased to some extent and the direction of change in the scanning position can be known. However, there is a problem that the detection accuracy of the scanning position of the light beam is extremely low due to the influence of the temperature change. Although the problem of such a temperature change can be solved by providing the constant temperature means, the configuration of the entire optical scanning device becomes complicated, large, and expensive.

An object of the present invention is to solve the above-mentioned problems of the conventional optical scanning device, to obtain a high resolution and high accuracy, to have a simple structure, and to provide an optical scanning device having a scanning position detecting function which can be inexpensive. It is intended to provide a device.

[0012]

According to the present invention, there is provided an optical scanning apparatus having a scanning position detecting function, comprising: a scanning light source for emitting a scanning light beam; A resonance type light deflecting unit for projecting, a position detecting light source unit for emitting periodic position detecting light, and the position detecting light via the light deflecting unit or a unit vibrating integrally therewith. Lens means for projecting the light onto a predetermined image forming surface, moiré fringe forming means having at least two openings arranged at a predetermined pitch on the predetermined image forming surface and forming moiré fringes, Light receiving means for receiving moiré fringes formed by the fringe forming means; signal processing means for processing an output signal of the light receiving means to detect a position of a scanning light beam deflected by the light deflecting means; To equip It is an butterfly.

In a preferred embodiment of the optical scanning device according to the present invention, the light receiving means is provided with n (n is an integer of 2 or more) light receivers in the moving direction of the moire fringes, and these light receivers are The moiré fringes are arranged at equal intervals from each other by 1 / n of the period of the moiré fringes. Further, a first Ronchi grating is provided for the position detecting light source means for emitting the position detecting light, and a second Ronchi grating is provided for the moiré fringe forming means, and the first and second Ronchi gratings are provided. It is preferable to provide an optical system for projecting the image of the first Ronchi grating on the second Ronchi grating in the optical path to be connected.

In such an optical scanning device, the pitch of the image of the first Ronkey grating projected on the second Ronchi grating is different from the pitch of the second Ronchi grating, and the two are parallel to each other. And the n number of light receivers are spaced apart in a direction orthogonal to the extending direction of the Ronchi grating, or the image of the first Ronchi grating is projected on the second Ronchi grating. The pitch and the pitch of the second Ronchi grating can be made equal and slightly inclined with respect to each other, so that the n light receivers can be spaced apart in a direction parallel to the extending direction of the second Ronchi grating. .

In particular, in the case of adopting the former configuration, a zoom lens is provided in the optical system, and the size of the first Ronchi grating projected onto the second Ronchi grating by adjusting the magnification thereof, therefore The pitch can be finely adjusted. In this case, the first and second Ronchi gratings have the same pitch, the zoom lens is adjusted, and the size of the image of the first Ronchi grating projected on the second Ronchi grating is adjusted. It is preferable to make these grating pitches slightly different. Further, in a preferred embodiment of the scolding scanning device of the present invention, a plurality of light receivers are provided and the signal processing means detects the position of the scanning light beam and also detects the moving direction of the scanning light beam. The configuration is as follows.

[0016]

FIG. 4 is a diagram showing the configuration of an embodiment of an optical scanning device having a scanning position detecting function according to the present invention, which is the same as the conventional optical scanning device described above with reference to FIGS. The parts are denoted by the same reference numerals, and detailed description thereof will be omitted. Also in this example, the configuration of the optical scanning mechanism is exactly the same as the conventional one. In this example, in order to detect information on the scanning position of the light beam, a light source unit 31 that emits light for scanning position detection is provided, and light emitted from this light source unit is made incident on the first Ronchi grating 32, The light transmitted through the first Ronchi grating is projected on the second Ronchi grating 35 through the zoom lens 33, the back surface of the galvanometer mirror 13, and the fixed focus lens. In this way, the image of the first Ronchi grating 32 is projected onto the second Ronchi grating 35.

In this embodiment, the pitch of the first Ronchi grating 32 is made slightly different from the pitch of the second Ronchi grating 35, and these gratings are arranged in parallel to each other. Therefore, as shown in FIG. 5, the grating pitch of the projected image 32I of the first Ronchi grating 32 is slightly different from the grating pitch of the second Ronchi grating 35, and extends in the extending direction of the grating. Thus, moiré fringes moving in a direction perpendicular to the direction in which the grating extends are formed. In this example, in order to photoelectrically detect the movement of the moire fringes, the first to fourth light receivers 36A to 36D are separated in the moving direction of the moire fringes by an interval of 1/4 of the pitch of the moire fringes. And place it.

The above-described first to fourth light receivers 36A to 36A
The output signal of D is supplied to a signal processing circuit 37 including a waveform shaping circuit. Here, information indicating the moving amount and the moving direction of the moiré fringe is detected. As is well known, the moiré fringes are obtained by enlarging the relative movement amount of the two gratings. Therefore, by detecting the movement amount of the moiré fringes, the rotation position of the galvanomirror 13, that is, the scanning position, is increased. It can be detected with a resolution. Therefore, the signal processing circuit 37
Generates a write address signal that compensates for scanning unevenness due to the galvanomirror 13. Based on this address signal, an image signal is written to the frame memory 19, whereby an image compensated for scanning unevenness due to the galvanomirror 13 is obtained. Obtainable.

In this embodiment, since the zoom lens 33 is provided in the optical system for projecting the image of the first Ronchi grating 32 on the second Ronchi grating 35, the projection magnification is adjusted by changing the magnification. be able to. Therefore,
For example, first and second Ronchi gratings 32 and 35
Of the same pitch as the zoom lens 33
Can be adjusted so that the pitch of the first Ronchi grating 32 projected on the second Ronchi grating 35 is different from the pitch of the second Ronchi grating. In this case, the first
The adjustment work for adjusting the pitch of the moire fringes to the interval between the fourth light receivers 36A and 36B can also be performed by adjusting the zoom lens 33.

FIG. 6 is a diagram showing a configuration of a Ronchi grating of another embodiment of the optical scanning device having a scanning position detecting function according to the present invention. In this example, the grating pitch of the image 32I of the first Ronchi grating 32 projected on the second Ronchi grating 35 is equal to the grating pitch of the second Ronchi grating 35, and these are inclined with respect to each other. It is. When such a combination of gratings is used, the moiré fringes extend in a direction perpendicular to the extending direction of the Ronchi grating and move in a direction parallel to the extending direction of the Ronchi grating. 4
Are arranged to be separated from each other in the extending direction of the Ronchi grating. Also in this case, the first
The fourth light receivers 36A to 36D have a pitch of one of the moire fringes.
Separated by a distance of / 4.

The present invention is not limited only to the above-described embodiment, and many modifications and variations are possible. For example, in the above-described embodiment, the four light receivers 36A to 36D are arranged at a distance of 1/4 of the pitch of the moire fringes to detect the movement of the moire fringes. Can be arranged at a distance of 1/4 of the pitch of the moire fringes. Further, according to the present invention, one light receiver can be arranged, or five or more light receivers can be arranged. In particular, when three or more light receivers are arranged, these light receivers can be arranged at equal intervals within one pitch of the moire fringes. According to the present invention, the resolution of scanning position detection can be improved as the number of light receivers is increased as described above.
It is limited by the size and arrangement of the aperture of the light receiver.

Further, in the above-described embodiment, two Ronchi gratings are used. For example, instead of using the first Ronchi grating, a laser beam radiated from a light source 41 is expanded as shown in FIG. It is also possible to generate a plurality of light spots 44-1 to 44-m by enlarging the light at 42 and making it incident on the diffraction pattern generator 43. Also,
Instead of using such a diffraction pattern generator 43,
A laser array in which a plurality of semiconductor lasers are arranged can also be used.

In the above-described embodiment, the light for detecting the scanning position is reflected on the back surface of the galvanomirror. However, if it can be distinguished from the scanning light beam, the light on the surface of the galvanomirror can be recognized. The light can be reflected, and further, can be reflected by a separate reflecting mirror that vibrates integrally with the galvanometer mirror.

[0024]

In the optical scanning device having the scanning position detecting function according to the present invention described above, in the optical scanning device using the resonance type optical deflecting means such as a galvanomirror, the light for periodic position detection is transmitted to the optical scanning device. The light is projected onto a predetermined image plane through a deflecting unit or a unit that vibrates integrally with the deflecting unit.
A moiré fringe is formed by moiré fringe forming means having a plurality of openings, and the moiré fringe is received by a light receiving means to detect the movement of the moiré fringe. Can be detected. Since moire fringes have the effect of increasing the amount of movement, the scanning position can be detected with high resolution. Further, since the position detecting device and the analog arithmetic unit which are sensitive to the temperature change as shown in FIG. 3 are not used, the detection of the scanning position is not affected by the temperature change, and the detection can be performed with high accuracy.
Moreover, since no constant temperature means is required, the configuration is simple and the cost is low. Further, the scanning direction can be detected by detecting the moving direction of the moiré fringes, so that useful information on the scanning position and the scanning direction can be obtained.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams for explaining scanning unevenness in scanning by a resonance type optical deflecting unit. FIGS.

FIG. 2 is a diagram showing a configuration of an example of a conventional optical scanning device having a scanning position detection function.

FIG. 3 is a diagram showing the configuration of another example of a conventional optical scanning device having a scanning position detection function.

FIG. 4 is a diagram showing a configuration of an embodiment of an optical scanning device having a scanning position detecting function according to the present invention.

FIG. 5 is a diagram showing the configuration of the first and second Ronchi gratings and the arrangement of the photodetectors.

FIG. 6 is a diagram showing a configuration of first and second Ronchi gratings and an arrangement of light receivers in another embodiment of the optical scanning device having a scanning position detecting function according to the present invention.

FIG. 7 is a diagram showing a configuration of a light source means for detecting an operation position of still another example of the optical scanning device having a scanning position detection function according to the present invention.

[Explanation of symbols]

11 scanning light source means, 12 electromagnetic drive means, 13
Resonant galvanometer mirror, 14 condenser lens,
15 object to be observed, 16 objective lens, 17 photodetector, 18 amplifier, 19 frame memory,
24 monitor, 31 light source means for scanning position detection, 32
The first Ronchi grating, 32I The image of the first Ronchi grating, 33 zoom lens, 34 lens, 35
2nd Ronchi grating, 36A-36D 1st-4th
, 37 signal processing circuit, 41 laser light source, 42 beam expander, 43 diffraction pattern generation element, 44-1 to 44-m beam spot

Claims (7)

[Claims] A scanning light source for emitting a scanning light beam; a resonance type light deflecting unit for deflecting the scanning light beam and projecting the scanning light beam on a scanning surface; Light source means for detecting a position to radiate; lens means for projecting the light for position detection onto a predetermined image forming surface via the light deflecting means or means vibrating integrally therewith; and the predetermined image forming surface , A moire fringe forming means having at least two openings arranged at a predetermined pitch and forming moire fringes; a light receiving means for receiving moire fringes formed by the moire fringe forming means; An optical scanning device having a scanning position detection function, comprising: a signal processing unit that processes the output signal of (a) and detects a position of the scanning light beam deflected by the optical deflection unit. 2. The light receiving means is provided with n (n is an integer of 2 or more) light receivers in the direction of movement of the moire fringes, and these light receivers are mutually separated by a distance of 1 / n of the period of the moire fringes. The optical scanning device having a scanning position detection function according to claim 1, wherein the optical scanning device is arranged at regular intervals. 3. A first Ronchi grating is provided in the position detecting light source means for emitting the position detecting light, and a second Ronchi grating is provided in the moiré fringe forming means. The first in the optical path connecting the Ronchi gratings
3. The optical scanning device according to claim 2, further comprising an optical system for projecting the image of the Ronchi grating on the second Ronchi grating. 4. The method according to claim 1, wherein the pitch of the image of the first Ronchi grating and the pitch of the second Ronchi grating are different from each other and are arranged in parallel with each other. 4. The optical scanning device having a scanning position detecting function according to claim 3, wherein the light receivers are arranged apart from each other in a direction orthogonal to the extending direction of the Ronchi grating. 5. The optical scanning device according to claim 4, wherein a zoom lens is provided in the optical system. 6. The method according to claim 1, wherein the pitch of the image of the first Ronchi grating and the pitch of the second Ronchi grating are projected on the second Ronchi grating and equal to each other and slightly inclined with respect to each other. 4. The optical scanning device having a scanning position detecting function according to claim 3, wherein the photodetectors are spaced apart in a direction parallel to a direction in which the second Ronchi grating extends. 7. A light receiving means for receiving the moiré fringes is provided with a plurality of light receivers, and the signal processing means detects a position of the scanning light beam and also detects a moving direction of the scanning light beam. Claim 1 characterized by the above-mentioned.
7. An optical scanning device having the scanning position detection function according to any one of 6.