JPH0668582B2 - Optical scanning method - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an optical scanning method such as a hologram scanner.

BACKGROUND OF THE TECHNOLOGY Recently, in order to save labor in register operations in supermarkets and the like, a bar code reading device that reads a bar code printed on the exterior of a product and inputs it into a computer has come to be used. Since a hologram scanner that converges and scans a laser beam by using a hologram as a light converging element and a light polarizing element is suitable for this apparatus, this hologram scanner is used as an optical scanning unit in a barcode reading apparatus.

FIG. 1 is a diagram for explaining the basic configuration of a bar code reading apparatus. In FIG. 1, 1 is an outer casing, 2 is a light source, 3 is a beam expander, and 4 is a hologram disc having a plurality of facets 4a. 5 is the rotary drive motor, 6
Is a window opened on the scanning surface of the housing, 7 is scanning light, 8 is signal light, 9 is a perforated mirror for separating the scanning light and the signal light,
Reference numeral 10 is a condenser lens, 11 is a photodetector, and 12 is a bar code printed on the exterior of the product. The operation of this device is such that the light passing through the perforated mirror 9 is converged and deflected by the hologram disk 4 and the bar code 1
Scan 2. The signal light 8 modulated by the barcode 12 is converged again by the hologram disk 4, reflected by the perforated mirror 9, and then passed through the lens 10 to be detected by the photodetector 11. The upper limit of the light intensity of the scanning light is restricted by the laser safety standard in consideration of safety for the eyes of the operator.

2. Related Art and Problems In such an optical scanning device, the laser safety standard amount of scanning light is determined by the speed, period, and other factors of scanning light.

FIG. 2 is a diagram for explaining scanning light by facets in which two types of interference fringes have different directions. In FIG.
3 is a laser light source, 14 is a laser beam, 15 is a hologram disc, 16 and 16 'are facets, 17 and 17' are the directions of interference fringes, A and B are scanning beams, and arrow 19 is the rotation direction of the hologram disc. ing. A figure shows scanning light A by the facet 16 whose interference fringe direction is 17, and a b figure shows scanning light B by the facet 16 'whose interference fringe direction is 17'. Is also its output direction,
The scanning speed on the scanning plane is also different. In such cases third
As shown in the figure, the safety reference light amounts 20 and 21 are different, but in the past, they were emitted at a level not reaching the safety reference light amounts 20 and 21, and with the same light amount 22 of A and B. As described above, the conventional optical scanning device has a drawback in that the light intensity of all scanning light is equal, and the light amount of all scanning light is limited by the lowest light amount of the safety standard among the plurality of scanning lights.

SUMMARY OF THE INVENTION The present invention has been made in view of the above drawbacks of the prior art, and an object of the present invention is to provide an optical scanning method capable of setting the light intensities of a plurality of scanning lights in the vicinity of respective safety reference levels.

According to the present invention, the object of the present invention is to rotate a hologram disc having a plurality of facets in which the directions of interference fringes are different from each other, diffract the light from the light source through the facets, and emit light in different directions for each facet. In an optical scanning device that emits and scans, using a polarized laser as the light source, with respect to the interference fringe direction of the facet,
This is accomplished by providing a means for adjusting the polarization direction of the light incident on the facets, and adjusting the light quantity ratio of the scanning light of the plurality of facets.

Embodiments of the Invention Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 4 is a diagram for explaining an optical scanning method according to the present invention. In the figure, 30 is a light source, 31 is polarized laser light, 32 is a 1 / 2λ plate, 33 is a hologram disk, and 34, 3
Reference numeral 4'denotes facets, and 35 denotes scanning light.

In this embodiment, as shown in FIG. 4, a polarized laser is used as the light source 30, a λ / 2 plate 32 capable of rotation adjustment is inserted between the light source 30 and the hologram disk 33, and facets 34 having different interference fringe directions are provided. The light quantity ratio of the scanning light by 34 'is set to λ / 2 plate 3
It is adjusted by rotating 2 so that the light quantity of each scanning light approaches the safety reference light quantity. The adjustment of the light quantity ratio utilizes the fact that the light use efficiency changes depending on the polarization direction as shown in FIG. From the figure, it is understood that when the scanning lights A and B in FIG. 2 are orthogonal to each other, the light quantity ratio can be adjusted in a wide range by the polarization direction. Although the λ / 2 plate 32 is used for adjusting the polarization direction in the present embodiment, the same effect can be obtained by simply rotating the light source 30 without using this. FIG. 6 shows the reflectance of the glass plate with respect to the beam incident angle in the case of S-polarized light (shown by the curve S) and P.
Although the case of polarization (shown by the curve P) is shown, it is also possible to change the polarization direction and adjust the amount of emitted light by setting the beam incident angle to the point 40 where the difference between S polarization and P polarization is most noticeable. Is.

As described above, according to the present invention, by adjusting the polarization direction of the laser light, as shown in FIG.
2. The light quantity of the scanning light B is 22 '.
It is possible to increase the light intensity up to around 20 and 21.

Effects of the Invention As described above in detail, the optical scanning method of the present invention uses the polarized laser as the light source, and adjusts the polarization direction to adjust the light quantity ratio of the plurality of scanning lights to be close to the safety reference level. The effect is that it can be set.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a conventional bar code reader, FIG. 2 is a diagram for explaining scanning light by facets in which two types of interference fringes have different directions, and FIG. 3 is its safety reference level. FIG. 4 is a diagram for explaining the amount of scanning light, FIG. 4 is a diagram for explaining the optical scanning method according to the present invention, FIG. 5 is a diagram showing the relationship between the polarization direction and light use efficiency, and FIG. 6 is glass. It is a figure showing the reflectance of S polarization and P polarization to the beam incidence angle of the plate. In the drawings, 30 is a light source, 31 is a polarized laser beam, and 32 is
Is a λ / 2 plate, 33 is a hologram disk, 34 and 34 'are facets, and 35 is scanning light.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinya Hasegawa 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Masayuki Kato, 1015, Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited ( 72) Inventor Toshiyuki Ichikawa 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Hiroyuki Ikeda 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (1)

[Claims] 1. Light for performing scanning by rotating a hologram disk having a plurality of facets in which interference fringes have different directions, diffracting light from a light source through the facets, and emitting light in different directions for each facet for scanning. In the scanning device, a polarized laser is used as the light source, means for adjusting the polarization direction of the light incident on the facet with respect to the interference fringe direction of the facet is provided, and the light amount ratio of the scanning light of the plurality of facets is adjusted. An optical scanning method characterized by the above.