JPH0444182A - Optical system for bar code scanner - Google Patents

Abstract

PURPOSE:To read a bar code even at the time of scanning it with a ball lens slightly floated from the bar code face by constituting an optical system of the ball lens and a convex lens and taking a relatively deep focal depth. CONSTITUTION:The lens in a light condensing and reading part of a bar code scanner 1 consists of a ball lens 15 which scans the bar code face and a convex lens 19 provided a prescribed length apart from the ball lens on the optical axis of the ball lens 15. Since the optical system consisting of the ball lens 15 and the convex lens 19 can take a relatively deep focal depth, the bar code can be read even at the time of roughly scanning it with the ball lens slightly floated from the bar code face, emitted illuminating light is thrown to a wide area of the bar code face with a high brightness through the ball lens 15, and much reflected light is returned by the convex lens 19, and therefore, it can be sufficiently received by a photo transistor.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an optical system for a barcode scanner.

(Prior Art) Barcode scanners are broadly classified into sapphire type and convex lens type.

In the sapphire method, as shown in Figure 3, the barcode surface 5
Since the refractive index of the sapphire ball lens 53 that scans 1 is large, when parallel illumination light is applied to this ball lens 53, it is focused on the surface of the ball lens 53. Therefore, when scanning the barcode surface with this ball lens 53, the image spreads on the ball lens-cup and there is a lot of reflected light.
An optical system can be formed independently without being combined with other lenses. This reflected light is received by a light receiving portion of a phototransistor 57 provided on the optical axis 2 of the ball lens 53 and converted into a signal. Further, a light shielding plate 59 is provided at the back of the light emitting section 55 to block the light from the light emitting section 55 and to receive only the reflected light from the barcode surface 51.

As shown in FIG. 4, the convex lens method is basically the same principle as photography, in which illumination light is emitted from a light emitting part 61 of a light emitting diode provided close to the barcode surface 51 to the barcode surface 51. The reflected light from the barcode surface 51 is imaged by a convex lens 63 onto a slit portion 65 with a diameter of 01 to 0.2 mm, and a portion of the image is extracted by a light receiving portion of a potdiode provided on the optical axis of the convex lens 63 and converted into a signal. ing. Further, a protective glass 69 is provided at the barcode abutting portion that directly touches the barcode surface 51, and the light emitting portion 61 and the convex lens 63 are provided with a protective glass 69.
In between, the light from the light emitting part 61 is blocked, and the barcode surface 5
A light shielding plate 71 is provided to receive only the reflected light from 1.

(Problem to be Solved by the Invention) However, although the sapphire method has a simple optical system and does not require much precision and is easy to assemble, the sapphire ball lens 53 has a shallow depth of focus, so it is one inch from the barcode surface 51. However, if you move away, the focus will deteriorate and the reading accuracy will deteriorate.

Furthermore, since the illumination light is also focused close to the surface of the ball lens 53, it tends to become a pin spot, making it difficult to align the light receiving axis with the illumination point.

In the convex lens method, the depth of focus of the optical system is deep, so the protective glass 69 at the barcode contact area is 2 mm from the barcode surface.
Although the barcode surface 51 can be read sufficiently even when the barcode surface 51 is far away or the barcode surface 51 has a large inclination when applied to the barcode surface 51, and the decomposition performance is good, this method has the following drawbacks.

Since there is nothing to condense the illumination light from the light emitting part 61 and the illumination light is weak, the light emitting part 61 is brought close to the barcode surface 51.
In addition, in order to obtain the precision of the slit 65, a high degree of skill is required for processing and assembly.

(Means for Solving the Problems) In order to solve the above problems, the optical system of the present invention has the following features: It consists of convex lenses arranged at predetermined intervals on the optical axis of the lenses.

(Function) According to the above means, since the optical system composed of the ball lens and the convex lens can have a relatively wide depth of focus,
Even rough scans where the barcode surface is slightly lifted can be read satisfactorily. In addition, the emitted illumination light passes through a ball lens and illuminates a wide area of the barcode surface with high brightness.
Since much reflected light is returned by the convex lens, the phototransistor can receive sufficient light.

(Example) Next, embodiments of the present invention will be described based on the attached drawings.

FIG. 1 is a perspective view of the barcode scanner of the present invention with the main parts cut away, and FIG. 2 is a diagram showing the optical system.

The barcode scanner 1 has a pen-like shape, and is screwed into two approximately cylindrical cases 3.5 that engage each other and have a thick base and a thin tip. and a conical tip 7. A cord 9 for connecting to the main body of a barcode scanner (not shown) extends from the base of the case 3.5, and a cord 9 is provided at the border between the base and the tip of the case 3.5 so that it can be easily grasped when held. Curved part 1
1 is formed.

A hole 13 having a diameter of 6 mm is provided at the tip of the pliers 7, and a ball lens 15 is fitted into the hole 13 and fixed therein. On the back of the ball lens 15, light emitting sections 17 each consisting of a light emitting diode are provided on both sides of the optical axis m of the ball lens 15.

As shown in FIG. 2, the light emitting section 17 is installed at an angle such that the optical axes p and q of the emitted illumination light are focused on the optical axis m near the surface of the tip of the ball lens 15. Further, on the optical axis m of the ball lens 15 on the back of the light emitting part 17, a lens with an effective aperture of 3 mm is placed at a predetermined interval from the ball lens 15.
A convex lens 19 is provided. Further behind this convex lens 19, on the optical axis m, there is provided a light receiving section 23 consisting of a phototransistor in which a light receiving element 21 is installed.

At the back of the light receiving unit 23, there is an IC board 2 for amplifying and processing signals converted from light to electrical signals by the light receiving unit 23.
5 is provided. Further, the IC board 25 is covered with a foldable shield plate 27 to prevent noise.

In this barcode scanner 1, when a barcode surface 29 shown in FIG.
The light receiving section 23 converts it into an electrical signal. At this time, even if the user rubs the barcode surface 29 strongly, since the ball lens 15 is soft, there will hardly be any streaks or irregularities on the barcode surface 29 that would make it unreadable.

In the barcode scanner 1 of the present invention described above, since the optical system is composed of the ball lens 15 and the convex lens 19, the depth of focus can be relatively wide, and the ball lens 15 is slightly lifted from the barcode surface 29. It can be read even if it is scanned in the same state. Furthermore, since the light from the light emitting section 17 passes through the ball lens 15 and is irradiated onto the barcode surface 29, the illumination area is wide and the light condensing property is high, so that high-intensity illumination is possible. Furthermore, by adding the convex lens 19, a large amount of reflected light returns, so that the light can be received by a phototransistor without the need for an expensive photodiode. Furthermore, since special precision is not required during processing and assembly, the optical axis of the optical system can be aligned at the level of a molded product using a mold, and therefore assembly is easy and does not require special skill.

(Effects of the Invention) As described in detail above, the present invention is inexpensive, easy to assemble, and allows correct reading without damaging the barcode surface even if the user handles it somewhat roughly.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the barcode scanner of the present invention with the main parts cut away, FIG. 2 is a diagram showing the optical system, FIG. 3 is a diagram showing the sapphire optical system, and FIG.
The figure shows a convex lens type optical system. In the drawings, 1 is a barcode scanner, 15 is a ball lens, 19 is a convex lens, 29 is a barcode surface, and m is an optical axis of the ball lens.

Claims (1)

[Claims] A barcode scanner characterized in that the lens of the light condensing and reading section is composed of a ball lens that scans the barcode surface and a convex lens provided at a predetermined interval on the optical axis of the ball lens. Code scanner optical system.