JPS63306415A - Hologram scanner - Google Patents

Abstract

PURPOSE:To facilitate sepn. of a scanning beam of a scanner independently of setting of a Bragg angle by providing prescribed polarizing characteristics to holograms. CONSTITUTION:The respective holograms are formed of the holograms having the polarizing characteristics, for example, PBS holograms 31, 32. Laser light A is, therefore, diffracted in the lower holograms 31 to A' if said light is projected as, for example, S polarized light to this hologram. Since this diffracted light A' is the P polarized light to the upper hologram 32, most of said light transmits said hologram. On the other hand, the laser light B projected to the hologram 32 so as to be the S polarized light thereto is the P polarized light to the hologram 3 and, therefore, most of the light transmits the hologram 31 without being diffracted by said hologram. Easy sepn. of scanning lines is thereby executed and since the degree of dependency on the incident angle decreases, the margin of the incident angle widens.

Description

[Detailed Description of the Invention] [Summary] In a hologram window type hologram scanner that uses a plurality of intersecting band-shaped holograms in the window for emitting a scanning beam, the scanner can be To easily separate scanning beams without depending on the setting of a Bragg angle.

[Industrial application field]

The present invention relates to a hologram scanner, and particularly to a hologram scanner using a hologram window in which a plurality of band-shaped holograms are crossed.

Holograms are widely used in various scanners such as barcode league laser scanners and printer laser scanners.

[Conventional technology]

The applicant of the present application previously disclosed in Japanese Patent Application No. 61-239903 a hologram scanner constituted by a hologram window formed by laminating two band-shaped holograms in a crosswise manner. In view of the fact that conventional hologram scanners required a space of about 100+- between the hologram and the scanning pattern, which hindered the ability to make the device thinner, we developed two scanners by interposing a transparent substrate between them. The hologram scanner is made thinner by stacking holograms and eliminating the space between them. The feature is that the light diffracted at the intersection (center part) of the upper and lower stacked holograms passes through the other hologram with the Bragg angle condition removed. The central part is required to have high incidence angle selectivity (narrow incidence angle margin), while the non-intersecting part, that is, the peripheral part, has a wide incidence angle margin so that high efficiency can be obtained even if the incidence angle is slightly shifted. This is desirable.

Since the present invention is directed to improving such a hologram scanner, this hologram scanner will first be briefly described (see FIGS. 3 to 5).

The hologram window 3 shown in FIGS. 3 and 4 has two strip-shaped first and second holograms 1.2 that intersect diagonally, and are formed on respective transparent substrates 11.12. The two holograms 1 and 2 intersect, for example, at approximately right angles at their central portions. The hologram window has a function of receiving laser scanning light emitted by a rotating mirror (not shown) or the like and diffracting it in a predetermined direction to form a desired scanning pattern.

At this time, for the pattern near the center, beams corresponding to the upper and lower patterns are separated and selected based on the following principle.

First, reference is made to FIG. 5, which shows a general characteristic curve of diffraction efficiency and transmittance of a hologram versus incident angle. The diffraction efficiency shown by the solid line is maximum at a predetermined angle of incidence (Bragg angle) B, and the efficiency decreases as it deviates from the Bragg angle B. On the other hand, the transmittance shown by the broken line is conversely minimum at the Bragg angle B, and becomes thicker as it deviates from the Bragg angle B. Therefore, in Fig. 3.4, the transmittance is ) is set to match the scanning beam (b), the scanning beam (a) diffracted by the first hologram 1 below has an incident angle that deviates from the Bragg angle B, as shown in Figure 5. Most of the light passes through the hologram 2.Thus, the holograms 1.2 formed above and below can generate an intersecting scanning pattern without interfering with each other.

Therefore, the diffraction efficiency at the intersection near the center of the hologram window is as steep as possible in order to improve the selectivity (separability) between the diffraction of the scanning beam (b) and the transmission of the scanning beam (a). It is desirable that Δθ in the figure be small.On the other hand, since only one beam is incident on the non-intersecting part, as shown in the scanning beam (c) in Figure 3.4, the selectivity of transmission and diffraction as in the intersecting part is high. There is no need to have In this case, of course the scanning beam (c)
It is desirable to have a large margin for the error in the angle of incidence, and therefore Δθ in FIG. 5 should be as large as possible.

As mentioned above, in a hologram window, multiple scanning lines (
Separation (selection) of scanning lines is required at hologram intersections where laser beams intersect. Conventionally, this separation of the scanning lines has been carried out by varying the angle of incidence of the laser beam on each hologram 1.2, that is, by removing the Bragg angle, as described above. If the incident angle of the laser beam matches the Bragg angle, it will be diffracted, and if it deviates from the Bragg angle, most of it will pass through the hologram.

[Problem that the invention seeks to solve]

However, in the above method, as mentioned above, the performance of the hologram requires that the alternation angle between the zero-order light (transmitted light) and the first-order light (diffraction light) be small. It is very difficult, if not impossible, to create a fully satisfactory hologram. Another disadvantage is that the margin for the usage conditions of the hologram is small. In any case, as mentioned above, the required characteristics for the hologram are different between the intersecting part at the center of the hologram window and the non-intersecting part at the periphery, and it is very difficult to create a hologram using the conventional method that relies only on controlling the Bragg angle. It's difficult.

An object of the present invention is to utilize the polarization characteristics of the hologram in the hologram window type hologram scanner as described above, without depending on the angle of incidence (such as whether or not it deviates from the Bragg angle) to separate the scanning lines. The objective is to enable easier separation.

[Means for Solving the Problems] In order to achieve the above object, according to the present invention, the crossing hologram of the hologram window is replaced by a hologram having polarization characteristics (
PBS hologram, etc.).

[For production]

A hologram with polarization characteristics, that is, a polarized beam splitter (Polarized Beam 5plitter)
) (hereinafter referred to as a PBS hologram), as is well known, only a laser beam (linearly polarized light) in a specific direction, for example, an S wave, passes through, and a hologram that has a function of a laser beam (linearly polarized light) in a specific direction, for example, an S wave, passes through it, and a hologram that has a function of a laser beam (linearly polarized light) in a direction orthogonal to that, for example, a P wave, passes through it. reflects. Therefore, when two holograms are arranged orthogonally crossed, when an S wave is incident on one hologram, it becomes a P wave on the other hologram, and by using such polarization separation characteristics, Scanning lines can be easily separated (selected) without substantially depending on the incident angle of the laser beam, increasing the incident angle margin.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to FIG. 1.2.

FIG. 1 shows the basic configuration of a hologram scanner (hologram window) 3 according to the present invention. This hologram window is basically configured in the same manner as that shown in FIG. 3, but according to the features of the present invention. , each hologram is formed by a hologram having polarization properties, for example a PBS hologram 31,32.

As a result, when laser light A (corresponding to ray A in FIG. 3) is incident on the lower hologram 31 as, for example, S-polarized light, it is diffracted here and becomes A'. This diffracted light A' becomes P-polarized light toward the hologram 32 above, and most of it is transmitted therethrough. On the other hand, the laser beam B (corresponding to the mouth in FIG. 3) that is incident on the hologram 32 as S-polarized light becomes P-polarized light on the hologram 31, so most of the light is not diffracted by the hologram 31. It will pass through there.

According to the invention, the holograms 31, 32 thus facilitate the separation of the scanning lines as in FIG. 3.4.

The diffraction and transmittance characteristics of P-polarized light and S-polarized light are shown in FIG.

If the holograms 31 and 32 (their interference fringes) intersect each other at right angles as shown in the figure, the holograms 31 and 32 may be formed exactly the same, but if their intersecting angles are not at right angles, the polarization characteristics of the PBS hologram will change. It will be understood that substantially the same effect as described above can be achieved by designing the elements to be appropriately different.

In addition, a hologram with polarization characteristics (PBS hologram)
is easily realized, for example, by a surface relief hologram.

〔effect〕

As described above, according to the present invention, scanning lines can be easily separated (
selection), and the dependence on the incident angle is reduced, increasing the incident angle margin.

Therefore, it is less affected by variations in the Bragg angle due to hologram creation, and the operational reliability as a hologram scanner is improved.

[Brief explanation of drawings]

FIG. 1 is an illustrative perspective view showing an embodiment of a hologram scanner according to the present invention, FIG. 2 is a characteristic diagram of diffraction and transmission efficiency for P waves and S waves of the PBS hologram shown in FIG. Fig. 3 is a perspective view showing the basic structure of the hologram window which is the premise of the present invention, Fig. 4 is a cross-sectional view of the hologram window shown in Fig. 3, and Fig. 5 is the incident view of the hologram shown in Fig. 3.4. Characteristic diagram of diffraction efficiency and transmittance with respect to angle. 11.12...Transparent substrate, 31.32...PBS hologram. Perspective view of the hologram scanner of the present invention Fig. 1 Incident angle → diffraction and transmission efficiency characteristic diagram of PBS hologram Fig. 2 Perspective view of hologram window Cross-sectional view of hologram window Fig. 3 Fig. 4 (Bragg angle) Hologram diffraction efficiency Figure 5: Incident angle characteristics of

Claims (1)

[Claims] 1. A hologram scanner having a hologram window (3) with at least two band-shaped holograms intersecting each other, characterized in that the holograms are constituted by holograms (31, 32) having polarization characteristics. .