JP2588000B2 - Light beam scanning device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a light beam scanning device, and more particularly to a light beam scanning device suitable for use in a bar code reader.

2. Description of the Related Art Bar code readers are increasingly being used as input terminals for point of sales (POS) or as device terminals for product management automation in factory automation (FA).

Some of the above barcode readers scan a barcode attached to a product at a relatively distant position with a laser beam, and receive and read reflected light from the barcode with a sensor.
A light beam scanning device is used for such a bar code reader.

As an optical beam scanning device for laser light, a rotating hologram plate diffracts the laser light to form a scanning light that is focused at a constant focus and changes its direction gradually, and the scanning light is made incident on a mirror to amplify the scanning angle. What you do is common.

[Problems to be Solved by the Invention] By the way, since the conventional light beam scanning device has a fixed focal length, if the distance of the bar-coded object changes, the light beam incident on the bar code is narrowed. However, there was a problem that reading was erroneous.

The present invention has been made in view of the above problems, and provides a means for solving the problem, and provides a light beam scanning device having a plurality of focal lengths and enabling accurate reading regardless of a change in the distance of an object. Is what you do.

[Means for Solving the Problems] The configuration of the present invention will be described with reference to FIG. 1. A light beam scanning device comprises a light beam output means 1 for emitting a linearly polarized beam L.
And a polarization direction changing means 2 for changing the polarization direction of the incident linearly polarized light beam L in accordance with the external signal 6a. The polarization direction changing means 2 converts the incident linearly polarized light beam having a different polarization direction. Beam angle changing means 3 which emits light at different predetermined angles, and linearly polarized beams L, L 'incident at different angles from the beam angle changing means 3,
Diffractive surface 4a for focusing and scanning at different focal positions FA and FB
And the diffraction means 4 formed with.

[Operation] The linearly polarized light beams incident at different angles are diffracted and focused to different focal positions by the diffractive means and scanned. When the direction of polarization of the linearly polarized beam is changed by the external signal, the angle of incidence of the light beam on the diffraction means is changed, and scanning is performed at different focal positions.

Thus, even if the position of the object changes, the scanning of the light beam is performed at the focal position corresponding to the change, so that a good bar code or the like can always be read.

First Embodiment FIG. 1 shows the overall configuration of a light beam scanning device, wherein 1 is a laser oscillator for emitting a P-polarized linearly polarized beam L, and 2 is a liquid crystal plate. The liquid crystal plate 2 changes the arrangement of the liquid crystal molecules by applying a voltage. When the voltage is applied, the incident light is transmitted as P-polarized light as it is. When no voltage is applied, the incident P-polarized light is converted into S-polarized light whose polarization direction is orthogonal.

31 is a polarization beam splitter, 32 is a condenser lens, and 33 is a mirror, which constitute the beam angle changing means 3. That is, the polarizing beam splitter 31 passes or reflects the incident polarized beam L according to the polarization direction of the polarized beam L. That is, the P-polarized light is reflected by the polarization beam splitter 31.
Pass through the condenser lens 32 and converge on the mirror 33,
The light is reflected obliquely upward from the focal point. On the other hand, the S-polarized light beam is reflected by the polarization beam splitter 31, and is transmitted upward (L 'in the figure).

Above the beam angle changing means 3, a disc-shaped hologram plate 4 is arranged, and the hologram plate 4 is rotated by a motor 41 supporting the center. The diffraction surface 4a of the hologram plate 4 is formed by double exposure.

This will be described with reference to FIGS. 3 to 6. First, as shown in FIG. 3, the reference light Lr of the parallel light beam and the object light Lb diverging from one point are set at angles α and α ′, respectively. Exposure is performed by causing incident interference. Thereafter, as shown in FIG. 4, the reference light Lr converging at one point P behind the hologram plate 4 and the object light Lb diverging from one point are incident at angles β and β ′, respectively, and are exposed.

Thus, the diffraction surface 4a formed by the double exposure
When parallel reproduction light having an angle α is incident, it is converted to an angle α ′.
Then, the object light is emitted so as to be converged at the same position FA as the emitted light (FIG. 5). When the reproduction light having an angle β diverging from one point P is incident, the reproduced light is angled β ′ and The light is emitted so as to be focused at the same position FB as the light was emitted (FIG. 6).

When the P-polarized light beam L or the S-polarized light beam L 'enters the same point on the hologram plate at angles α and β, respectively, they are emitted at angles α' and β ', respectively, as shown in FIG. At this time, with the rotation of the hologram plate 4, the emitted light beam rotates along the conical surface having the emission (incident) point X as the vertex.

Above the hologram plate 4, a plurality of mirrors 5 are circumferentially disposed so as to cross the conical surface. A light beam emitted from the hologram plate 4 is reflected by the mirror 5, and
Focus on the distance between points A and FB. And the hologram plate 4
With the rotation of the mirror, the mirror on which the light beam enters is switched, and the light beam converging to the distance between the point FA and the point FB is scanned by the change in the angle of incidence of the light beam on each mirror.

The hologram plate 4 is provided with a mark at one place on the outer peripheral surface (not shown), and a photoelectric detector 7 is provided facing the outer peripheral surface, and emits a signal every time the mark passes. . The mark passing signal is input to the liquid crystal controller 6, and the liquid crystal controller 6 alternately outputs or stops the voltage signal 6a to the liquid crystal 2 every time the signal is received.

In the light beam scanning device having the above-described structure, when the voltage signal 6a is not input to the liquid crystal plate 2, the P-polarized beam emitted from the laser oscillator 1 is directly input to the polarizing beam splitter 31, and passes therethrough. Then, the light is reflected by the mirror 33, and further converged at a distance of the focal point FB via the hologram plate 4 and the mirror 5 and scanned.

When the hologram plate 4 makes one rotation and the mark passing signal is input to the liquid crystal controller 6, a voltage signal 6a is output, and the P-polarized beam input to the liquid crystal plate 2 is converted into an S-polarized beam and Enter 31. Then, the light is reflected right above, focused through the hologram plate 4 and the mirror 5 to the distance of the focal point FA, and scanned.

Thus, each time the hologram plate 4 makes one rotation,
The focal position of the scanned light beam is changed, and as a result,
Even if the position of the bar-coded object changes, good reading can always be performed by the light beam focused to a focal point close to the position.

[Second embodiment] Fig. 7 shows a second embodiment of the present invention, and the same components as those in the first embodiment are denoted by the same reference numerals. In the present embodiment, the laser oscillator 1 outputs a randomly polarized beam, and a polarizer 8 is provided between the laser oscillator 1 and the liquid crystal plate 2 in front of the laser beam so as to be linearly polarized.

Further, an ultrasonic or optical distance measuring device 9 is provided to detect the distance to the object. The liquid crystal controller 6 outputs or stops a voltage signal to the liquid crystal plate 2 so as to switch to a polarized beam that focuses on a focus closer to the detected distance.

In each of the above embodiments, if a plurality of sets of liquid crystal plates and beam angle changing means are provided and a large number of polarized beams are used, a multifocal device can be obtained.

[Effects of the Invention] As described above, the light beam device of the present invention changes the polarization direction of a polarized beam according to an external signal, and causes a light beam having a different polarization direction to be different on a diffraction surface by a beam angle changing unit. The light is incident at an angle and focused at different focal positions, so that a bar code or the like can always be read well even if the position of the object changes.

[Brief description of the drawings]

1 to 6 show a first embodiment of the present invention.
FIG. 2 is a schematic perspective view showing the overall configuration of the apparatus, FIG. 2 is a schematic side view thereof, FIGS. 3 and 4 are schematic side views showing an exposure state of the hologram plate, and FIGS. 5 and 6 are hologram plates. FIG. 7 is a schematic side view showing a reproducing state of the second embodiment of the present invention.
FIG. 1 is a schematic perspective view illustrating an entire configuration of an apparatus according to an embodiment. DESCRIPTION OF SYMBOLS 1 ... Laser oscillator (light beam output means) 2 ... Liquid crystal plate (polarization direction changing means) 3 ... Beam angle changing means 31 ... Polarization beam splitter 32 ... Condensing lens 33 ... Mirror 4 ... Hologram plate (Diffraction means) 4a Diffraction surface 5 Mirror 6 Liquid crystal controller 7 Photoelectric detector 8 Polarizer 9 Distance measuring device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Taguchi 14 Iwatani, Shimowasumi-cho, Nishio-shi, Aichi Prefecture Inside the Japan Automobile Parts Research Institute (72) Inventor Sadahisa Onuma 14 Iwatani, Shimowasumi-cho, Nishio-shi, Aichi Japan Inside the Automotive Parts Research Laboratory (72) Inventor Yasuhiko Koike 1-1-1 Showa-cho, Kariya, Aichi

Claims (1)

(57) [Claims] 1. A light beam output means for emitting a linearly polarized light beam, a polarization direction changing means for changing a polarization direction of the incident linearly polarized light beam according to an external signal, and a different polarization direction from the polarization direction changing means. Beam angle changing means for emitting linearly polarized light beams incident at different predetermined angles, and diffraction for focusing and scanning linearly polarized light beams incident at different angles at different focal positions by the beam angle changing means. A light beam scanning device comprising: a diffraction unit having a surface formed thereon.