JPH0755010Y2 - Barcode reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an autofocus scanning device using a light beam, and more particularly to a bar code reader using a semiconductor laser as a light source.

(Prior Art) Laser light is suitable for scanning an object to be scanned with high resolution by forming a narrow beam by utilizing its good convergence property.
For example, when applied to a barcode reader, there are cases where it is desired to obtain a large reading depth (variation range of readable distance) with a small barcode symbol. In such a case, if the required resolution is d and the maximum read depth obtained is DOF, then DOF and d have the relationship given by the following equation.

DOF = 1.241d ² Therefore, if one beam is used and resolution is given,
The maximum reading depth that can be obtained is uniquely determined. Therefore, when trying to obtain the same maximum reading depth with higher resolution, until now the autofocus method that always focuses on the surface to be scanned or the multifocal method was adopted and the reading depth was divided to obtain the required maximum reading depth. Was done with one of the multifocal methods.

FIG. 2 shows an example of the automatic focusing method, in which the distance measuring means 25 measures the height of the scanned object 26 or 27,
The position adjusting mechanism 22 of the converging optical system 21 is controlled by the output signal of 25, and adjustment is performed so as to focus on the scanned object surface.
Reference numeral 20 is a laser light source, and 29 is a mounting table for an object to be scanned.

FIG. 3 shows an example of a multifocal system, which uses the hologram disc 31 shown in FIG. 3B and utilizes that each segment S1 to S8 is equivalent to a convex lens.
Each group is divided into two groups and each has a different focal length, and the required depth DOF1 is shared by DOF2 to DOF5 with a smaller beam diameter to obtain the maximum reading depth DOF1, as shown in FIG. 3 (c). . In FIG. 3A, 32 is a drive device for the hologram disk 31, and 30 is a light source.

(Problems to be Solved by the Invention) In the conventional scanning unit configuration shown in FIG. 2 that uses the automatic focusing system, the focusing optical system is mechanically moved to control the beam focus position. It will be on the order of several tens of msec, and depending on the application, the required performance of the system may not be satisfied. Further, in the multi-focus method, scanning beams with different focus positions are constantly scanning, so when applied to a barcode reader, even scanning beams with insufficient resolution will always be scanned, and a distorted signal will be obtained. Therefore, there is a risk of erroneous reading, and the number of effective scans is substantially the number divided by the number of divisions, and in some cases sufficient reading performance cannot be obtained.

(Means for Solving the Problem) Therefore, the bar code reader of the present invention is composed of a plurality of semiconductor lasers capable of high-speed switching, a converging optical system attached thereto, and one prism. Therefore, a plurality of semiconductor lasers are focused on different positions by respective focusing optical systems, and a beam is emitted from one emission point while switching at high speed.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1A shows an embodiment in which two semiconductor lasers are used as light sources 1 and 8 where the refractive index of light in air is n ₁ and the refractive index of a prism is n ₂ . A light beam 3 from the semiconductor laser light source 1 is given a necessary beam diameter and focus position by a converging optical system 2, enters a prism 4 at an incident angle φ1, and is internally refracted at a refraction angle φ2 to be an outgoing beam 5. Is emitted. φ
1 and φ2 have the following relationship.

n ₁ sin φ ₁ = n ₂ sin φ ₂ The light beam 6 from the other semiconductor laser light source 8 is given a focus position different from the beam diameter required by the converging optical system 7 and the focus position of the light beam 3, and then enters the prism 4. Incident vertically and totally reflected on the hypotenuse of the prism (φ2 = φ3),
It is emitted as an outgoing beam 5. The two semiconductor laser light sources 1 and 8 are driven so as not to overlap alternately in a time division manner. With this method, two beams having different focus positions can be switched at high speed to perform scanning under optimum conditions. In the embodiment of FIG. 1 (a), a triangular prism is used as a constituent element for combining, but if a polygonal prism is used, the same can be realized by using a larger number of semiconductor laser elements. is there.

FIG. 1 (b) shows four semiconductor laser light sources 10, 11 and 11 which radiate in the same direction with respect to the triangular prism 16 although the emission points are different.
This is an example when 12, 13 are used. FIG. 1 (c) shows that the emitted light 40a, 41a of the laser light source module 40, 41 for bar code reader having the structure as shown in FIG. 1 (a) is further combined by the prism 43, and the beam 44 is emitted from the same emitting point. Is a three-element configuration for radiating.

(Effect of the Invention) As described above, the bar code reader of the present invention does not receive an undesired distorted signal by using only the optimum scanning line at the time of scanning in the multifocal system, and has a high-speed response. Is also possible, which has the effect of making it possible to obtain the required maximum reading depth with a narrower beam.

[Brief description of drawings]

1 (a), (b), and (c) are schematic diagrams according to various embodiments of the present invention, and FIG. 2 is an optical system path diagram of a scanning unit of an optical scanning device according to a conventional autofocus system, and FIG. (A), (b), (c) is a figure which shows the prior art example by a multifocal system. 1,8 …… Semiconductor laser light source, 2,7 …… Convergence optical system, 5,1
4,15,44 …… Exit beam, 4,16,43 …… Prism, 40,41
...... Laser light source module.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 1/04 1/113 H04N 1/04 104 Z

Claims (1)

[Scope of utility model registration request] 1. A plurality of semiconductor laser light sources, focusing optical means attached to each of them, and one prism, wherein the plurality of semiconductor laser light sources and their associated focusing optical means have different focal points. It is configured to emit a laser beam having a position toward the prism, and semiconductor laser beams having different focus positions pass through the auxiliary converging optical means, and are refracted and reflected by each side of the prism. A bar code reader characterized in that the semiconductor laser light source, the converging optical means, and the prism are arranged so that they are respectively turned and emitted in the same direction on the beam emission side from the prism.