JPH07271890A - Data symbol reader - Google Patents

Abstract

PURPOSE:To execute proper reading by preventing a reading part from the projection of a light source image independently of the state of a reference face in a symbol reading area. CONSTITUTION:This data symbol reader is provided with an illuminating device 40, a reading part 4, a light source driving circuit, a signal processing circuit, and a communication driver. The device 40 is constituted of a light source 41 and a pair of prisms 46. Three faces of each prism 46 consist of an incident face 461, a reflection face 462 and a projection face 463. The incident face 461 if a diffusion face and the reading part 4 side of the projection face 463 is a light shielding face 464. Plural grooves 465 whose cross section is like a V shape are formed on both the projection faces 463 along the normal direction of a light receiving face of a CCD 43.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a data symbol reader for reading coded information such as two-dimensional data symbols.

[0002]

2. Description of the Related Art Today, a method and apparatus for converting product information into a bar code and reading the bar code with a bar code reader are widely used for application to, for example, a POS system. However, the bar code is one-dimensionally read by scanning with a laser beam in the array direction of the bar, and has a limited amount of information.

Therefore, in recent years, as a device capable of carrying more information, for example, a two-dimensional data symbol in which a black and white mosaic pattern is two-dimensionally arranged has been developed. An apparatus for reading this two-dimensional data symbol. There are almost no devices that use area sensors.

On the other hand, in developing such a data symbol reading apparatus, if a method of reading two-dimensional data symbols at the same time in a plane is adopted, the two-dimensional data symbols arranged in the reading area are made two-dimensionally uniform. Need to illuminate.

Further, in such an apparatus, when the light emitted from the light source is directly reflected in the reading area and reaches the CCD, the light source image is reflected on the CCD, and accurate reading cannot be performed.

In order to satisfy the above requirements and not to capture the light source image, the optical axis of the illumination light and 2 in the reading area.
The angle formed by the normal to the reference plane on which the dimensional data symbol is located needs to have a certain size.

However, when the inclination angle of the optical axis of the illuminating light is increased, the entire illuminating device must be widened in the lateral direction, and the entire reading device must be large.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to uniformly illuminate the inside of a symbol reading area and to downsize the apparatus, and to properly adjust the symbol reading area regardless of the state of the reference plane. Another object of the present invention is to provide a data symbol reading device capable of various readings.

[0009]

The above objects are achieved by the present invention described in (1) to (6) below.

(1) A data symbol reading device for reading a two-dimensional data symbol, comprising a light source for illuminating a symbol reading area, a reading section for receiving light from the symbol reading area, a reflecting surface and an emitting surface. And a prism that bends the light from the light source to a reference surface of the symbol reading area as desired and crosses the exit surface of the prism along the normal direction of the light receiving surface of the reading unit. A data symbol reading device having a plurality of V-shaped grooves arranged in parallel.

(2) Each of the grooves extends in a direction perpendicular to the normal line of the light receiving surface of the reading section, and both groove surfaces facing each other of the groove are in relation to the normal line of the emission surface. The data symbol reading device according to (1), wherein the data symbol reading devices are inclined in opposite directions.

(3) The data symbol reading device according to (1) or (2), wherein the grooves are continuously formed adjacent to each other.

(4) In the groove in the vicinity of the symbol reading area, at least the groove surface on the reference surface side of both groove surfaces facing each other is used as a diffusion surface. The data symbol reader according to any one of 1.

(5) In the groove located in a predetermined region from the end of the prism on the reference surface side, at least the groove surface on the reference surface side of both groove surfaces facing each other is a diffusion surface. The data symbol reader according to any one of (1) to (3).

(6) When the shape of the prism and the positional relationship between the prism and the light source are such that the normal line of the reference surface and the optical axis of the received light at the reading unit are parallel, The optical axis of the incident light on the reference plane is inclined by a predetermined angle with respect to the normal line of the reference surface, and the optical axis of the received light on the reading unit and the principal ray from the light source before entering the prism. When the angle formed by the optical axis of the above is α, and the angle at which the optical axis of the incident light is inclined with respect to the normal line of the reference plane is β, the relation of α <β is satisfied. )
The data symbol reader according to any one of (1) to (5).

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The data symbol reading apparatus of the present invention will be described below in detail with reference to the preferred embodiments shown in the accompanying drawings.
FIG. 1 is a sectional side view schematically showing a configuration example of a data symbol reading device. As shown in the figure, the data symbol reading device 1 has a casing 2, and in the casing 2, a lighting device 40 and a data symbol 3 are provided.
The reading unit 4 for reading 8 is installed in an integrated state.

A light source drive circuit 42 for lighting a pair of light sources 41 constituting the lighting device 40 is connected to the lighting device 40. As the light source 41, for example, a light emitting element such as an LED, a halogen lamp, a semiconductor laser, or the like can be used.

Between both light sources 41, a CCD (charge coupled device) 43 which is an area sensor and this CC
A reading unit 4 including an optical system 44 that guides reflected light in a symbol reading area 36 described below to form an image is installed at D43. In the CCD 43, a large number of pixels are arranged in rows and columns, and each pixel is configured to accumulate an electric charge according to the amount of light received and to sequentially transfer the electric charge at a predetermined time. This transferred charge is
It constitutes the image signal of the read image.

In this embodiment, the CCD 43
Is only required to be able to detect the brightness (luminance) of each part of the data symbol 38, but a CCD 43 for a color image can also be used depending on the configuration of the data symbol to be read. Further, the optical system 44 is configured by arbitrarily combining optical components such as various lenses, prisms, filters, and mirrors.

FIG. 2 is a plan view showing the symbol reading area 36. As shown in the figure, the symbol reading area (shown by the one-dot chain line in the figure) 36 is provided on the reference plane (the plane on which the data symbol 38 is located) 37, and the illumination device 40.
Is a region in which the light is emitted and the reflected light is received by the reading unit 4 and the data can be read.

In the illustrated configuration, the data symbols (symbol codes) 38 are composed of a black or white (or transparent) mosaic arranged in x rows × y columns (x, y is an integer of 2 or more). . The black or white color of this mosaic represents, for example, 0 or 1 in the binary system, and this combination specifies desired information. The data symbol 38 is not limited to the one having the illustrated configuration.

In the illuminating device 40 and the reading section 4 as described above, the light source driving circuit 42 turns on the light sources 41 arranged as described later, and the light emitted from each light source 41 is applied to the symbol reading area 36. The reflected light is imaged on the light receiving surface of the CCD 43 via the optical system 44, and an image signal (analog signal) corresponding to the received light amount is output.

The configuration of the lighting device 40 will be described in detail below. FIG. 3 is a side view showing a configuration example of the illumination device 40 and the reading unit 4, and FIGS. 4 and 5 are side views showing a configuration example of the prism 46 of the illumination device 40, respectively. As shown in FIG. 3, the lighting device 40 has a plurality of light sources 41 and a pair of prisms 46 installed below the light sources.

As shown in FIG. 2, in the apparatus of this embodiment,
Of the sides that define the symbol reading area 36, three light sources 41 are installed along a pair of parallel sides (along the long side in this embodiment). Hereinafter, the pair of light sources 41 that are arranged to face each other with the CCD 43 as a representative will be described, but the same applies to the other two pairs of light sources 41.

As shown in FIG. 3, the CCD 43 receives light from the CCD 43 when the illuminating device 40 and the reading unit 4 are parallel to the reference plane 37 in the symbol reading area 36 (hereinafter referred to as an appropriate state). The normal O of the reference surface 37 of the symbol reading area 36 is arranged so as to be orthogonal to the surface. In the proper state, the CCD 4
The optical axis of the received light entering 3 is parallel to the normal line O, and the optical axis of the principal ray immediately after being irradiated from the light source 41,
In other words, the light source 41 is arranged so that the optical axis of the principal ray immediately before entering the prism 46 is substantially parallel (α≈0) to the normal line O, that is, the optical axis of the light received by the CCD 43. Has been done.

Here, the "optical axis of the chief ray" means the chief ray having the highest light intensity. As shown in FIG. 3, the pair of prisms 46, 46 are located on the optical axis of the light emitted from the light source 41, and are arranged so that the exit surfaces 463 of the prisms 46, which will be described later, face each other. It is installed along the long side of the reading area 36.

In this prism 46, three surfaces constituting the prism 46 are an incident surface 461 and a reflection surface 46, respectively.
2, the emission surface 463, and the light source 4 on the emission surface 463
The first side (upper side in FIG. 3) is a light-shielding surface (light-absorbing surface) 46.
It is 4. In this case, the incident surface 461 is a diffusion surface. This diffusion surface is processed into a rough surface (rubbing surface), that is, a surface on which fine irregularities are formed. Further, the exit surface 463 is configured to be parallel to the optical axis of the principal ray from the light source 41 before entering the prism 46 when α≈0 described later.

As the material of the prism, for example, plastics such as acrylic and polycarbonate, and various glass materials can be used, and the refractive index thereof is 1.4 to 1.
It is good to use about 6 and preferably about 1.5.

The exit surface 463 of the prism 46 is along the light receiving surface of the reading section 4, that is, the normal direction of the light receiving surface of the CCD 43 (direction of the optical axis 91 of the principal ray from the light source 41 before entering the prism 46). Thus, a plurality of V-shaped grooves 465 having a horizontal cross section are juxtaposed.

In this case, as shown in FIG. 4, each groove 465 is
Extends in the direction perpendicular to the normal line of the light receiving surface of the CCD 43 (the optical axis 91 of the principal ray from the light source 41 before entering the prism 46), and the grooves 465 are continuously formed adjacent to each other. ing. As a result, on the emission surface 463, the surface 469
However, since the vertical surface can be eliminated and the entire surface can be inclined, the light emitted from the emission surface 463 to the reference surface 37 passes through the groove surface 466 without exception. That is, the groove 4
The amount of light passing through the groove surface 466 is increased as compared with the case where 65 are not formed adjacent to each other, so that the effect of the present invention is further improved.

Further, the groove surfaces 466 of the respective grooves 465 facing each other,
The lines 467 are inclined in directions opposite to each other with respect to the normal line 468 of the emission surface 463. Here, as shown in FIG. 4, the groove surface 46 on the reference surface 37 side with respect to the normal line 468 of the emission surface 463.
Each 6 and CCD43 side angle groove surface 467 (the light source 41 side) is inclined, when the theta ₁ and theta _2, the theta ₁ and theta ₂ are each inclined angle theta ₃ of the reflective surface 462 of the prism 46 It is appropriately determined according to various conditions such as.

In this case, the inclination angle θ ₃ is 15 to 30 °.
When the degree, theta ₁ and theta ₂ are respectively 30
It is preferably about 60 °. The width (= pitch) L ₁ of each groove 465 is not particularly limited, and the prism 46
Depending on various conditions such as dimensions,
It may be about 1 to 2 mm.

Further, from the end of the prism 46 on the side of the reference surface 37, each groove 465 in a predetermined area, that is, in this embodiment, the groove surface 466 of each groove 465 in the area 95 near the symbol reading area 36 and 467 and the surface 469 in the region 95 are diffusion surfaces. This diffusing surface is processed into a rough surface (rubbing surface), that is, a surface of the groove or surface 469 on which minute irregularities are formed.

In this case, in the area 95, the principal ray from the light source 41 is incident on the prism 46 and is emitted from the emission surface 463 of the prism 46 at the position on the emission surface 463 (the principal ray emitted from the emission surface 463). Is located on the symbol reading area 36 side from the intersection A) of the optical axis 91 and the groove surface 466. Here, the width L _{2 of the} region 95 is not particularly limited and may be appropriately determined depending on various conditions such as the size of the prism 46 and the inclination angle θ _3, but may be, for example, about 2 to 4 mm.

As shown in FIG. 3, a protective glass plate 45 is provided between both prisms 46 and near the boundary between the emission surface 463 and the light shielding surface 464. The protective glass plate 45 prevents foreign matter such as dust from entering the inside of the apparatus.

Next, the function of the prism 46 will be described. FIG. 6 is a graph showing the light distribution characteristics of the light source (light emitting diode) 41. The respective light sources 41 in this embodiment have substantially the same brightness, and the light distribution characteristics thereof are shown in FIG.

As shown in FIG. 3, the light emitted from the light source 41 is transmitted from the incident surface 461 of the prism 46 to the prism 46.
Is injected into the interior. In this case, as described above, the incident surface 46
Since 1 is a diffusion surface 461, the light from the light source 41 is diffused by the incidence surface 461 and is incident on the inside of the prism 46. That is, the incident surface 461 acts so as to widen the light distribution area of the light from the light source 41 passing therethrough, widen the irradiation area in the symbol reading area 36, and make the brightness in the irradiation area more uniform. In addition, in FIG. 3, the optical axis 91 of the principal ray is shown by a one-dot chain line, and a predetermined ray of the diffused light is shown by a two-dot chain line.

The light incident on the prism 46 is reflected by the reflecting surface 4
The light is reflected by 62 and emitted from the emission surface 463. In this case, the light shielding surface 464 prevents the light from the light source 41 and the diffused light diffused by the incident surface 461 from being directly applied to the symbol reading area 36.

As described above, the exit surface 463 has
Since the groove 465 is provided, as shown in FIG. 4, the light reflected by the reflecting surface 462 is reflected by the groove surface 466 of the groove 465.
Is incident on the groove surface 466 at an angle perpendicular or nearly perpendicular. Therefore, the reflected light from the reflecting surface 462 is not refracted when passing through the groove surface 466, or the groove 465 is not refracted.
Refraction is made at a smaller angle than that in the case where the reference surface 37 is not provided and the reference surface 37 is irradiated with the light.

In this embodiment, since the groove 465 is formed so that the groove surface 466 is perpendicular to the optical axis 91 of the principal ray reflected by the reflecting surface 462, as shown in FIG. In addition, when the light ray of the principal ray on the optical axis 91 is emitted from the groove surface 466 on the symbol reading area 36 side (reference surface 37 side), it goes straight to the symbol reading area 36 side. Further, the light beam distant from the optical axis 91 is refracted and emitted at a small angle even if it does not go straight.

Further, as shown in FIG. 4, since the surface in the area 95 is a diffusing surface, the reflecting surface 462 to the area 9 are used.
The light incident on the grooved surface 466 in 5 is further diffused by the grooved surface 466 and is applied to the reference surface 37.

Here, as shown in FIG.
In the case where the groove 465 is not provided on the emission surface 463 of No. 6, the light reflected by the reflection surface 462 is transmitted to the emission surface 463.
Since the light enters at an acute angle with respect to 63, it is largely refracted at the exit surface 463 and is irradiated onto the symbol reading area. That is, as compared with the case where the groove 465 is not provided, the incident angle of the light entering the symbol reading area 36 (the angle of the optical axis of the light with respect to the normal line of the reference plane 37 of the symbol reading area 36) becomes smaller, and the symbol reading area 36 becomes smaller. Is incident on the prism 46 side (end portion).

Therefore, when the reference surface 37 is inclined with respect to the reference surface 37 in the proper state (for example, when the reference surface 37 'is inclined about + 5 ° or -5 °), the light is emitted. The light emitted from the surface 463 is directly reflected in the symbol reading area 36 and reaches the CCD 43.
The light source image may appear on the image 3, which may make proper reading difficult.

On the other hand, according to the data symbol reading apparatus 1 of the present invention, since the groove 465 is provided in the exit surface 463 of the prism 46 as described above, as shown in FIG. Angle of incidence of a chief ray incident on (the normal line O of the reference plane 37 to the normal line O of the reference plane 37 of the symbol reading area 36 when the normal line O of the reference plane 37 and the optical axis of the received light in the reading unit 4 are parallel to each other). Angle β of the optical axis 91 of the groove 4 on the exit surface 463 of the prism 46.
The size can be increased as compared with the case where 65 is not provided.

Therefore, as shown in FIG. 3, not only when the reference surface 37 and the reading unit 4 are parallel to each other, but also when the reference surface 37 is inclined with respect to the reference surface 37 in the proper state ( For example, even in the case of the reference plane 37 ′ inclined about + 5 ° or −5 °), it is possible to reliably prevent the light source image from being captured on the CCD 43, and thus the reference plane of the symbol reading area 36. Proper reading can be performed regardless of the state (inclination) of 37.

Further, by increasing the incident angle β, the inside of the symbol reading area 36 can be illuminated uniformly. The incident angle β is preferably about 30 to 60 °, particularly about 40 to 50 °.

Further, according to the data symbol reading apparatus 1 of the present embodiment, as described above, the area 9 of the prism 46 is used.
Since the surface in 5 is a diffusion surface, the irradiation light concentrated at the end of the symbol reading area 36 can be diffused, and when reading a subject having strong reflection characteristics, the reference surface 37 ( The subject surface) can be illuminated uniformly.

In this embodiment, the reference surface 3 of the symbol reading area 36 is formed by bending the light from the light source 41 as desired.
Since the prism 46 is used as the light guiding optical system that guides the light to the optical guide 7, the number of parts can be reduced compared to the case where the light guiding optical system is configured by combining optical members such as mirrors.

Here, the position (irradiation center position) where the optical axis 91 of the chief ray emitted from the light source 41 is incident on the reference surface 37 of the symbol reading area 36 is from the long side to the side orthogonal to the side (short side). The distance is preferably 0.1 to 0.34 times the length of the side. Within this range, the overall luminance within the symbol reading area 36 can be made more uniform.

In the above structure, as shown in FIG. 5, when the normal line O of the reference surface 37 and the optical axis of the light received by the reading section 4 (light incident on the CCD 43) are parallel, The optical axis of the received light in the reading unit 4, that is, the normal line O of the reference surface 37 and the light source 41 before entering the prism 46
The angle α of the principal ray from the optical axis 91 is α≈0 °,
In other words, the light source 41 is installed so that they are substantially parallel to each other.

With such a configuration, CC
The light source 41 can be arranged close to the D43, and the illumination device 40 can be made compact as a whole.

In the present invention, it is preferable that α and β satisfy the relationship of α <β, and the shape of the prism 46, that is, the incident surface 461, the reflecting surface 462, and the emitting surface is satisfied so as to satisfy this relationship. The angle and positional relationship of 463 (groove surface) and the positional relationship between the prism 46 and the light source 41 are set.
In such a case, it is possible to reduce the size of the illumination device 40, and thus the data symbol reading device 1 as a whole. Note that α does not necessarily have to be α≈0 °, and may be set to be inclined.

As shown in FIG. 1, a signal processing circuit 5 for processing an image signal from the reading section 4 is provided in the casing 2 of the data symbol reading apparatus 1 having the illuminating device 40 having such a configuration. There is.

FIG. 7 is a block diagram showing a configuration example of the data symbol reading device 1. As shown in the figure, the signal processing circuit 5 in the data symbol reading device 1 mainly includes a CCD drive circuit 6, an amplification circuit 8, a binarization circuit 10, a memory 12, a control means (CPU) 15,
It is composed of a communication driver 16 and connection lines thereof.

Further, the control means 15 includes the light source drive circuit 4
2, and if necessary, a switch circuit, a display device (not shown) such as an LCD (liquid crystal display element) or a CRT, and the like are connected.

In the data symbol reader 1, reading is started by turning on the trigger switch,
The signal processing circuit 5 performs predetermined signal processing as described later. The signal processed by the signal processing circuit 5 is
Driver 1 for communication after being decoded into necessary data
6, the data is input to a computer 17 such as a personal computer or a workstation installed outside. In such a computer 17, the input data is stored and tabulated.

The light source drive circuit 42 is a circuit for supplying electric power to the light source 41 to turn it on, and is controlled by the control means 15. By turning on the main switch, the control means 15 activates the light source drive circuit 42, and the light source 41 is thereby turned on. Here, the lighting time of the light source 41 is set as desired by the light source drive circuit 42 or the control means 15.

When the main switch is turned on, the control means 15 operates the CCD drive circuit 6. CCD
A CCD horizontal drive pulse and a CCD vertical drive pulse are output from the drive circuit 6 to the CCD 43, and charge accumulation and transfer in the CCD 43 are controlled.

Further, the CCD drive circuit 6 generates a clock signal and sends a signal (composite clock signal) obtained by combining this signal with a horizontal synchronizing signal and a vertical synchronizing signal to the control means 15.

The image signals (analog signals) sequentially output from the CCD 43 of the reading section 4 are amplified by the amplifier circuit 8, A / D converted and input to the binarization circuit 10. In the binarization circuit 10, the digital image signal is compared with the threshold data and binarized. The binarized data output from the binarization circuit 10 is input to a predetermined address of the memory 12 by an address counter built in the control means 15. The address counter is driven by the composite clock signal input from the CCD drive circuit 6.

Data is sequentially read from the memory 12 in accordance with the address designated by the built-in address counter, and for one screen worth of data, for example, contour detection (for contour detection ( Image information processing such as extraction of only information about the data symbol 38), dropout correction, rotation, etc.
The decoder built in the unit decodes the data according to the data symbol system. The decoded data is output to the host computer 17 via the communication driver 16.

The data symbol reading apparatus of the present invention has been described above based on the illustrated configuration example, but the present invention is not limited to this. For example, in the present embodiment, the groove surfaces 466 and 477 of the groove 465 in the region 95 of the emission surface 463 of the prism 46 are diffusion surfaces, respectively, but in the present invention, for example, of the groove surfaces 466 and 477, Only the groove surface 466 on the reference surface 37 side may be used as the diffusion surface. Further, in the present invention, the diffusion surface may not be provided on the emission surface 463 (both the groove surfaces 466 and 477).

Further, in this embodiment, the incident surface 461 of the prism 46 is a diffusion surface, but in the present invention, the incident surface 4 is used.
Instead of using 61 as a diffusion surface, for example, a diffusion plate is used as the prism 46.
May be closely attached to or spaced apart from each other on the incident surface 461 of. Further, similarly to the above, in the present invention, the reflecting surface 462 and the light shielding surface 463 of the prism 46 may be changed to, for example, a reflecting plate and a light shielding plate, respectively.

Further, in the present invention, the light-shielding surface 463 of the prism 46 is not particularly limited to the light-absorbing surface as in the present embodiment, and other than this, for example, a reflecting surface (mirror surface), a half mirror, an optical element. It may be a filter (these transmittances are arbitrary) or the like.

Further, in the present embodiment, each groove 465 has the same shape, width, pitch, and angle (θ ₁ , θ ₂ ), but in the present invention, these are the same as the normal direction of the light receiving surface of the CCD 43. (To the optical axis 91 direction of the principal ray from the light source 41 before entering the prism 46).

Further, in the present invention, the reading section 4 may receive not only reflected light on the reference surface 37 but also transmitted light. In the present invention, the number of light sources and the irradiation center position are appropriately changed depending on the size of the symbol reading area, the light distribution characteristic of the light source, the brightness, and the like. Furthermore, the present invention is not limited to the above description, and the size of the symbol reading area may be different, or the shape of the area may be square.

Next, the present invention will be described in more detail with reference to specific examples. Using the lighting device 40 shown in FIG. 3, the symbol reading area 36 is horizontally (short side direction).
Was measured. All the six light emitting diodes used as the light source 41 had the same characteristics, and the light distribution characteristics were as shown in FIG. The size of the symbol reading area 36 is as follows: short side = 18.5 mm,
The long side = 24.5 mm. Other conditions were measured under the conditions described below.

FIG. 8 and FIG. 9 respectively show the luminance distribution in the horizontal direction (short side direction) of the symbol reading area 36 when the symbol reading area 36 shown in FIG. 2 is illuminated using a prism under the following conditions. It is a graph shown.

8 and 9, the vertical axis represents the level of the video signal (unit: IRE), and the horizontal axis represents the position of the symbol reading area 36 in the horizontal direction (short side direction). Further, the curves a ₁ and a ₂ respectively show the luminance distributions when illuminating the paper having good diffusivity, and the curves b ₁ and b ₂ respectively show the brightness distribution when illuminating the paper having strong reflection. It shows a luminance distribution. The flatter the curves a ₁ , b ₁ , a ₂ and b ₂ , the more uniform the illumination.

<Example 1>

The following prism whose emission surface is not a diffusion surface was used. Material of prism: Acrylic resin (refractive index = 1.5) Groove width L ₁ : 1 mm Angle θ ₁ : 45 ° Angle θ ₂ : 35 ° Angle θ ₃ : 22.5 ° Angle α: 0 ° Angle β: 45 ° Results are shown in FIG.

<Example 2>

Both groove surfaces 46 in the area 95 of the exit surface of the prism
The same prism as in Example 1 was used except that 6, 467 and the surface 469 were diffusion surfaces. Width L _{2 of} region 95: 4 mm The result is shown in FIG.

<Results>

As shown in FIG. 8, in Example 1 in which the prism whose emission surface is not a diffusing surface is used, when a sheet having good diffusibility is illuminated, the entire symbol reading area 36 is covered. It can be seen that the illumination is uniform. Further, it can be seen that even when the highly reflective paper is illuminated, it is uniformly illuminated except at the end of the symbol reading area 36.

Further, as shown in FIG. 9, in Example 2 in which the prism having the diffusion surface in the area 95 of the emission surface is used, the paper with good diffusivity and the paper with high reflectivity are illuminated. In each case, it can be seen that the entire area of the symbol reading area 36 is uniformly illuminated.

[0077]

As described above, according to the data symbol reading apparatus of the present invention, the installation position of the light source can be brought close to the reading section, the size of the entire apparatus can be made compact, and the symbol reading can be performed. The area can be illuminated uniformly.

In particular, regardless of the state of the reference surface of the symbol reading area, that is, not only when the reference surface of the symbol reading area is parallel to the reading section, but also when the reference surface is inclined. Even if there is, it is possible to surely prevent the direct reflected light from entering the reading unit, and thus it is possible to perform proper reading without performing accurate horizontal alignment with respect to the reference surface.

Further, when the vicinity of the symbol reading area on the exit surface of the prism is a diffusion surface, the symbol reading area can be uniformly illuminated regardless of the characteristics of the subject (reflection diffusion characteristics). As a result, it is possible to properly read the symbol reading area of a subject having a wide range of reflection and diffusion characteristics.

[Brief description of drawings]

FIG. 1 is a sectional side view schematically showing a configuration example of a data symbol reading device of the present invention.

FIG. 2 is a plan view showing a symbol reading area in the present invention.

FIG. 3 is a side view showing a configuration example of an illumination device and a reading unit according to the present invention.

FIG. 4 is a side view showing a configuration example of a prism in the present invention.

FIG. 5 is a side view showing a configuration example of a prism in the present invention.

FIG. 6 is a graph showing a light distribution characteristic of a light source (light emitting diode) according to the present invention.

FIG. 7 is a block diagram showing a configuration example of a data symbol reading device of the present invention.

FIG. 8 is a graph showing the luminance distribution in the horizontal direction (short side direction) of the symbol reading area according to the present invention.

FIG. 9 is a graph showing a luminance distribution in the horizontal direction (short side direction) of the symbol reading area in the present invention.

FIG. 10 is a side view showing a configuration example of a prism having no groove on the exit surface.

[Explanation of symbols]

 1 Data Symbol Reading Device 2 Casing 4 Reading Unit 40 Illumination Device 41 Light Source 42 Light Source Driving Circuit 43 CCD 44 Optical System 45 Protective Glass Plate 46 Prism 461 Incident Surface 462 Reflecting Surface 463 Emitting Surface 464 Light-Shielding Surface 465 Groove 466, 467 Groove Surface 468 Normal 469 Surface 5 Signal processing circuit 6 CCD drive circuit 8 Amplifying circuit 91 Optical axis 95 area 10 Binarization circuit (comparator) 12 Memory 15 Control means (CPU) 16 Communication driver 17 Host computer 36 Symbol reading area 37, 37 'Reference plane 38 data symbol

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[Procedure amendment]

[Submission date] February 24, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction content]

Here, as shown in FIG.
In the case where the groove 465 is not provided on the emission surface 463 of No. 6, the light reflected by the reflection surface 462 is transmitted to the emission surface 463.
Since the light enters at an acute angle with respect to 63, it is largely refracted at the exit surface 463 and is irradiated onto the symbol reading area. That is, as compared with the case where the groove 465 is provided, the incident angle of the light that enters the symbol reading area 36 (the angle of the optical axis of the light with respect to the normal line of the reference surface 37 of the symbol reading area 36) becomes smaller, and the symbol reading area 36 becomes smaller. Is incident on the prism 46 side (end portion).

Claims (6)

[Claims] 1. A data symbol reading device for reading a two-dimensional data symbol, comprising a light source for illuminating a symbol reading region, a reading unit for receiving light from the symbol reading region, a reflecting surface and an emitting surface. A prism for bending the light from the light source to a reference surface of the symbol reading area as desired, and a cross section along the normal line direction of the light receiving surface of the reading unit, at the exit surface of the prism. Is a data symbol reading device having a plurality of V-shaped grooves arranged in parallel. 2. Each of the grooves extends in a direction perpendicular to a normal line of the light receiving surface of the reading section, and both groove surfaces facing each other of the groove are opposite to each other with respect to a normal line of the emission surface. The data symbol reader according to claim 1, wherein the data symbol reader is inclined in the opposite direction. 3. The data symbol reading device according to claim 1, wherein the grooves are continuously formed adjacent to each other. 4. The groove in the vicinity of the symbol reading area, wherein at least the groove surface on the reference surface side of both groove surfaces facing each other is a diffusion surface. The described data symbol reader. 5. The groove in a predetermined region from an end of the prism on the reference surface side, wherein at least the groove surface on the reference surface side of both groove surfaces facing each other is a diffusion surface. 4. The data symbol reader according to any one of 1 to 3. 6. When the shape of the prism and the positional relationship between the prism and the light source are such that the normal line of the reference surface and the optical axis of the light received by the reading unit are parallel, the reference surface is moved to the reference surface. The optical axis of the incident light of
The angle between the optical axis of the received light at the reading unit and the optical axis of the principal ray from the light source before entering the prism is α The data according to any one of claims 1 to 5, wherein when the angle at which the optical axis of the incident light is inclined with respect to the normal line of the reference plane is β, the relationship α <β is satisfied. Symbol reader.