JPS61134727A - Optical scanner - Google Patents

Abstract

PURPOSE:To change the focusing position of a beam in the advancing direction of a scanning beam as desired by providing a light source which can vary the wavelength of exist light and a holographic laser scanner disposed with plural hologram lenses on a disk. CONSTITUTION:The light oscillated from a semiconductor laser 1 is collimated by a collimating lens 2 and is then focused by a cylindrical lens 3. A scanning plane 6 is scanned by the hologram lenses 5 of the holographic laser scanner 4. The distance up to the holographic laser scanner and an object which is the scanning plane is measured by a distance measuring sensor 7 for which, for example, an ultrasonic wave is used. The focal length of each hologram lens and wavelength are inversely proportional to each other. The focal length is determined by a control circuit 8 such as microcomputer having, for example, GP-IB interface and the oscillation wavelength of the semiconductor laser is calculated from the inverse proportional relation so that the light converges onto the measured object surface. The oscillation wavelength and injection current are in a proportional relation and therefore the injection current of the semiconductor laser is determined.

Description

DETAILED DESCRIPTION OF THE INVENTION (Axiom of Industrial Use) The present invention particularly relates to optical scanning devices such as holography and laser scanners.

(Prior Art and its Problems) As an optical scanning device, a disk-type optical scanning device using a hologram has been proposed in place of the conventional combination of a rotating polygon mirror and an f/θ lens.

In this method, a plurality of holograms are arranged along the circumference of a disk, and by rotating the disk, as many scanning lines as there are holograms on the disk are scanned per rotation of the disk. Conventional optical scanning devices only scan a scanning plane that is a predetermined distance away from the scanner because the beam convergence position is predetermined. Therefore, it is difficult to scan objects that change three-dimensionally or whose positions are not known in advance. Furthermore, even if the position N of the object is known, if it deviates from the beam convergence position, it is necessary to replace the holographic laser scanner with a suitable one, which poses the problem of poor operability.

(Object of the Invention) The present invention eliminates the above-mentioned drawbacks, allows the convergence position of the beam to be changed arbitrarily in the direction of travel of the scanning beam, and allows objects at any position to be easily scanned. The object of the present invention is to provide an optical scanning device with good operability.

(Structure of the Invention) An optical scanning device of the present invention includes a light source with a variable wavelength of emitted light, a holographic laser scanner in which a plurality of hologram lenses are arranged on a disk, and a holographic laser scanner that transmits monochromatic light emitted from the light source to the hologram. The configuration includes an optical system that guides the light to the lens, and a control device that controls the light source so that the wavelength of the light emitted from the light source changes.

(Operation and Principle of the Invention) In an optical scanning device such as a holographic laser scanner, several holograms are arranged and fixed on the circumference of a disk, and the holograms are rotated at high speed to scan light.

Holographic lenses use diffraction to clear the lens. For example, in the case of an Al Fresnel zone plate, which is one of the hologram lenses, its focal point li! The relationship between If and phase distribution is expressed as φ(γ)=πγ2/λf (1). Here, λ represents the reproduction wavelength.

In equation (1), the position where the right side is an integral multiple of 2π represents the position of the stripe on the zone plate. Therefore, the following relationship holds true: γ-f-Ryo...(2). However, n is a positive integer.

As can be seen from equation (2), in the same zone plate, the focal length f can be changed by changing the wavelength λ. Therefore, by using a light source with a variable wavelength, the scanning plane, which is the imaging position of the beam, can be changed.

(Embodiment) FIG. 1 shows the configuration of a first embodiment of the present invention. In this embodiment, the wavelength tunable light source 1 is a semiconductor K L, -f
't M''7° 1 In a semiconductor laser, the oscillation wavelength generally changes depending on the injection current.In particular, in a cleavage-coupled resonator semiconductor laser (Q8 laser), the variable wavelength width is 150 steps, and GHz modulation is possible. Since the oscillation output does not change due to the injection current, it is suitable for this application.This laser is described in the magazine [
Applied Fix Letter
Physics Letter), 1983, 65
The paper described on pages 0 to 652 [High-speed direct single-frequency modulation (H
igh -5peeddirect single-f
Requirement Qadulation with
arge tuning rate and freq
emptiness excursionin cleaved
-coupled-cavity semiconductor
ctorlasers) J. This laser beam divides a conventional semiconductor laser into two parts and uses one part as a laser and the other part as a modulator. By slightly shifting the mode spacing between the oscillation wavelengths of the two lasers, keeping the laser injection current constant, and changing the mode by changing the modulator injection current, the laser oscillates when the two modes match. do. Therefore, a discontinuous wavelength change corresponding to the mode difference between the laser and the modulator is possible. In the above paper, the wavelength change loLimA with respect to the injection current
, a variable wavelength width of 5oA, an oscillation wavelength of 13 μm, and a switching time of 118 ee. By utilizing this, three-dimensional scanning can be performed by adjusting the injection current to change the oscillation wavelength and change the scanning surface. The light emitted from the semiconductor laser 1 is collimated by the collimating lens 2, then converged by the cylindrical lens 3, and is then focused by the hologram lens 5 of the holographic laser scanner 4.
The scanning plane 6 is scanned by. The distance between the holographic laser scanner and the object, which is the scanning surface, is measured by a distance measuring sensor 7 that uses, for example, ultrasonic waves. From equation (2),
The focal length and wavelength of a hologram lens are inversely proportional. For example, GP-IB so that the light converges on the measured object surface.
A control circuit 8 such as a microcomputer having an interface determines the focal length and calculates the oscillation wavelength of the semiconductor laser from an inverse proportional relationship. Furthermore, since there is a proportional relationship between the oscillation wavelength and the injection current, the injection current of the semiconductor laser is determined. For example, a power supply 9 having an ink face such as GP-IP
The calculated current value is controlled to flow. It is also possible to directly specify the position of the scanning plane by the control circuit without using a distance sensor. In this embodiment, the control device is composed of a distance measurement sensor 7, a control circuit 8, and a power supply 9, but if the position of the scanning plane is known in advance, the distance measurement sensor is unnecessary and only the control circuit and electric current are required. .

FIG. 2 shows a second embodiment of the invention. In this example, by using a light source consisting of a plurality of lasers,
This makes it possible to use 14 wavelengths. Therefore, in this embodiment, the optical system includes a collimating lens 13, 14, a beam splitter 15, and a cylindrical lens 1.
It was composed of 6.

The light oscillated by the semiconductor laser 11 is collimated by the collimating lens 13 and then enters the polarizing beam splitter 15 . On the other hand, the light emitted by the semiconductor laser 12 having an oscillation wavelength different from that of the laser 11 is collimated by the collimating lens 14 and then combined with the light emitted from the laser 11 by the collimating lens 14 . These lights are converged by a cylindrical lens 16 and sent to a hologram scanner 17.
The scanning plane 19 is scanned by the hologram lens 18 . A distance sensor 20 measures the distance between the hologram scanner and an object, which is a scanning surface, and a control circuit 21 causes a current to flow through a laser having an oscillation wavelength corresponding to the distance.

Further, fine adjustment of the oscillation wavelength is achieved by controlling the currents 23 and 24 to change the injection current. In this case as well, the position of the scanning plane can be specified without using a distance measuring sensor.

(Effect of the invention) As a holographic laser scanner, wavelength 780
If a lens with a focal length of 100 mmK and a scanning magnification of 1.times. is used, the position of the scanning plane will move by 20 m111 with respect to a semiconductor laser with a variable wavelength width of 15 o.times.

Furthermore, by using two semiconductor lasers with a wavelength of 765 nm or 795 nm, the position of the scanning plane can be adjusted to 40 gt.
Can be moved.
As described above in detail, by using the optical scanning device of the present invention, it is possible to easily scan an object that changes three-dimensionally or an object whose position is not known in advance.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of the invention, and FIG. 2 is a diagram showing a second embodiment of the invention. In the figure, 1... Semiconductor laser, 2... Collimation scanning surface, 7... Distance sensor, 8... Control circuit, 9...
・Power supply, 11.12... Semiconductor laser, 13.14・
...Collimating lens, 15... Polarizing beam splitter, 16... Cylindrical lens, 17... Holographic scanner, 18... Hologram lens, 19
...Scanning surface, 20...Distance sensor, 21...Control circuit, 22.23...Power supply.

Claims (1)

[Claims] A light source with a variable wavelength of emitted light, a holographic laser scanner in which a plurality of hologram lenses are arranged on a disk, an optical system that guides monochromatic light emitted from the light source to the hologram lens, and light emitted from the light source. An optical scanning device comprising: a control device that controls a light source so that the wavelength of the light changes.