JPS61112289A - Bar code reader - Google Patents

Abstract

PURPOSE:To increase the area of irradiation to obtain a sufficient quantity of irradiating light and also to avoid the deterioration of the image resolution even though the scanning direction has more inclination than the orthogonal position to the bars of a bar code, by forming an irradiating spot of a light beam into a diamond shape which is long in the rectangular direction. CONSTITUTION:The bar B of a bar code is scanned by shifting an irradiated spot P of a light beam toward an arrow head. A state where an adjacent bar code never gets inside the spot P is always secured even in case the scanning direction is tilted by theta, where the vertical angle and the length of a shorter diagonal line of a diamond shape of the spot P are set at 2theta and (b) respectively. As a result, the image resolution has no deterioration. The angle theta is set at about >=10 deg. and preferably in a range of 20-40 deg.. Furthermore it is preferably set at the minimum value 0.24mm of less of the bar code for the width of the spot P (also available enough with about 0.3mm).

Description

[Detailed description of the invention] B Industrial application field The present invention relates to self-scanning barcode readers.

The conventional self-scanning type barcode reader' uses a scanning means (1) to swing a light beam to scan the barcode recording surface with the light beam, but in order to obtain the necessary resolution, It is necessary to focus the light beam onto a sufficiently small spot on the scanned surface. Also, from the perspective of signal processing, it is desirable to obtain a read signal with as high a S/N ratio as possible.
Therefore, the larger the amount of light beam, the better. Needless to say, one way to converge a large amount of light onto a minute spot on the scanned surface is to use a high-intensity light source, and from this point of view a laser is suitable as a light source. - Mankumoto When using a light source that emits light from a surface such as a light emitting diode, it is sufficient to increase the weight of the irradiated light, and for this purpose, it is possible to increase the irradiation area of the light beam on the surface to be scanned.

The resolution of the barcode reader is good only in the direction perpendicular to the bars of the barcode, and resolution is not required in the direction parallel to the bars, so the irradiation area of the light beam can be increased (
ζ In order not to reduce the resolution, it is best to make the cross section of the light beam rectangular (and make the longitudinal direction perpendicular to the scanning direction, that is, parallel to the bar code bar). This is disclosed in Japanese Patent Application Laid-open No. 140467/1983.

This proposal attempts to obtain a rectangular beam spot using a rectangular cavity or a laser emitting aperture in a laser diode, thereby obtaining higher resolution than a circular subbot with the same amount of irradiation light.

In summary, if the irradiation spot of the light beam on the scanned surface is made into a rectangle that is one length longer in the direction parallel to the bar code bar, a high SZN ratio can be obtained even if the illuminance of the irradiation spot is low, and it is possible to select a usable light source. This means that the range becomes wider, and when a light source such as a laser is used, higher resolution can be obtained with the same amount of irradiation light.

C. Problems to be Solved by the Invention The method of making the irradiation spot of the light beam rectangular as described above has the following problems.

In FIG. 4, the hatched band B is the bar code bar, and the rectangular frame P is the irradiation spot of the light beam. Further, the arrow indicates the scanning direction by the light beam, and FIG. 4A shows the case where the scanning direction is correctly orthogonal to the bars of the bar code, and FIG. 4B shows the case where the scanning direction is tilted. As is clear from this figure, when the scanning direction is tilted, the effective spot of the light beam is expanded from a to b, and the resolution is reduced.

However, it is difficult to set the Neue code in the correct direction for the barcode reader, especially when placing a handheld barcode league against the side of the product to read the barcode. It is practically impossible to regulate the relative relationship with the league. For this reason, the idea of making the irradiation spot of the light beam rectangular has some concerns in ensuring the accuracy of reading.

The present invention aims to elongate the irradiation spot of the light beam so that the resolution does not deteriorate even if the scanning direction is tilted from the direction perpendicular to the bars of the bar code.

2. Means for Solving Problems In the present invention, the irradiation spot of the light beam is shaped into an elongated rhombus.

E action
) Figure 1 provides a detailed explanation of the invention.

In this figure, B is a bar code bar, and P is a light beam irradiation spot. The arrow indicates the scanning direction, and the figure a shows the case where the scanning direction is correct, and the figure shows the case where the scanning direction is tilted.

If the apex angle of the rhombus of all irradiation spots P is 20, and the length of the shorter diagonal is 2, even in the case of Figure 1' where the scanning direction is tilted by θ, the adjacent barcode will not enter the irradiation spot. The state is guaranteed to exist, and no resolution loss occurs.

Therefore, the value of θ can be set to an angle that is slightly larger than the end of the range, so that if a person is a little careful, the variation in the scanning direction can be easily settled within this range, and the rough estimate of θ is 1.
00 or higher and preferably in the range of 20° to 400°, and in a hand-held type, it is hardly effective at 5° or less. Further, the width of the irradiation spot is desirably equal to or less than the minimum width of the barcode, 0.24 mm, but it may be slightly larger, and about 0.3 mm is sufficient.

EXAMPLE FIG. 2 shows one example of the present invention. 1 is the light emission of the light source
2 is a lens that converges the light from the light source 1 onto the surface to be scanned, 3 is a polygon mirror of the scanning means that swings the light beam, F is the surface to be scanned, and 4 is the lens that converges the light from the surface to be scanned. It is a light receiving element that receives light. 5 is an electrical recorder stored in the grip of the barcode reader, and 6 is a motor that rotates the polygon mirror 3. In Figure 6, the scanning direction of the light beam L is perpendicular to the plane of the figure. The irradiation spot of the light beam β on the scanned surface F has a rhombic shape that is 1ζ long in the direction parallel to the plane of the drawing.

Figure 3 shows the light emission of the light source 1 used in the above embodiment.
Indicates an iode. n is N type L p is P type layer and the light emission is P-
This is done at the N-junction and the light is extracted through the P-type layer. P
A light-shielding film S is formed on the surface of the mold layer, and a diamond-shaped aperture A is provided in the light-shielding film, and this aperture serves as an optical light source. It is formed on the scanned surface F.

G. Effect Since the barcode reader of the present invention has the above-described configuration, and the irradiation spot of the light beam is long in the shape of a rhombus in the direction perpendicular to the scanning direction, the irradiation surface area can be widened, making it easy to obtain a sufficient amount of irradiation light. Even if the direction is more or less similar to the bar of the bar code than perpendicular to it, the resolution does not deteriorate, and signal processing becomes easier and more reliable. Specifically, the SZN ratio of the barcode reading signal is improved, the signal level difference between the black and white portions of the barcode becomes large, and the falling edge of the boundary between black and white becomes steeper, making signal processing easier. Become. Furthermore, since it is easy to obtain a sufficient amount of illumination light, the degree of freedom in selecting a light source increases, and it becomes possible to design an inexpensive and compact barcode reader.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the present invention in detail, Fig. 2 is a longitudinal cross-sectional side view of a barcode reader of the -* company example of the present invention, and Fig. 3 is a diagram showing the main components of the light emitting diode of the light source used in the same embodiment. FIG. 4, an enlarged perspective view of a portion □□□, is a diagram illustrating the problems of the conventional example. Agent: Patent Attorney Kosuke Mai 1st RM

Claims (1)

[Claims] It has a light source, a lens that focuses the light beam on the surface to be scanned, and a light beam scanning means that swings the light beam, and the irradiation spot of the light beam on the surface to be scanned has a long diamond shape in the direction orthogonal to the scanning direction. A barcode reader characterized by: