Scanner

Abstract

To provide a scanner that has a high degree of freedom in design, can prevent reflection of illumination light, and can increase reading accuracy.SOLUTION: A scanner has an imaging unit, a light source, and a protective plate. The imaging unit picks up an image of a reading target located in an imaging area inside an imaging visual field. The light source is arranged outside the imaging area, and irradiates the reading target with illumination light. The protective plate is arranged between the reading target and the light source and across the imaging area, has a surface that is on an imaging unit side in a space between the surface and a boundary line on a light source side of the imaging visual field and has an angle on the imaging area side larger than 90°, and can transmit the illumination light and reflected light from the reading target.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a scanner that reads, for example, a barcode on a product. [Background technology]

[0002] A scanner that reads product barcodes includes a light source for illuminating the barcode and an image sensor for capturing the barcode. Examples of such scanners include a fixed scanner in a point-of-sale (POS) terminal used for transaction processing, or a handheld scanner connected to the POS terminal via a cable.

[0003] The scanner is equipped with a transparent protective plate to protect the image sensor, etc., and the light source and image sensor are housed within a housing covered by the protective plate. In other words, illumination light emitted from the light source passes through the protective plate and is irradiated onto the surface of the product with the barcode, and the reflected light passes through the protective plate and is received by the image sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-80551 Summary of the Invention [Problem to be solved by the invention]

[0005] If the light source and image sensor are located inside the protective plate, there is a possibility that the illumination light reflected by the inner surface of the protective plate will be received by the image sensor, which may cause a problem known as glare. If glare occurs, the accuracy of reading the barcode will decrease.

[0006] To prevent reflections, methods such as placing the light source close to the protective plate or placing the light source outside the protective plate can be considered, but both methods impose restrictions on the placement of the light source, reducing design freedom.

[0007] The problem to be solved by the embodiments of the present invention is to provide a scanner that has a high degree of freedom in design, can prevent glare of illumination light, and can improve reading accuracy. [Means for solving the problem]

[0008] A scanner according to one embodiment includes an imaging unit, a light source, and a protective plate. The imaging unit captures an image of a target object located in an imaging area within an imaging field of view. The light source is disposed outside the imaging area and irradiates the target object with illumination light. The protective plate is disposed between the target object and the light source and across the imaging area, and has a flat surface that forms an angle of greater than 90° between the imaging unit side and the imaging area side of the light source-side boundary line of the imaging field of view, and is capable of transmitting the illumination light and light reflected from the target object. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing a main part of a scanner according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing a scanner according to a first modified example. [Figure 3] FIG. 3 is a schematic diagram showing a scanner according to a second modified example. [Figure 4] FIG. 4 is a schematic diagram showing a scanner according to a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment will be described with reference to the drawings. 1 is a cross-sectional view of scanner 10 taken along a plane including the optical axis of illumination light (described later). In the following description, the cross section of FIG. 1 will be referred to as the central plane. The components of scanner 10 have a plane-symmetrical structure with respect to the central plane.

[0011] The scanner 10 has a housing 1 with an opening 2. Inside the housing 1 are a light-transmitting protective plate 3, a light source 4 that emits illumination light, a reflecting mirror 5, and an imaging unit 6. The scanner 10 is a hand scanner that connects to, for example, a POS terminal via a cable. The configuration of this embodiment can also be applied to a fixed scanner. The object to be read by the scanner 10 is, for example, a barcode attached to a product.

[0012] The imaging unit 6 includes an imaging element 61, such as a CCD (Charge Coupled Device) area sensor. The imaging unit 6 has a predetermined imaging field of view angle. The imaging field of view angle represents the range of the field of view that can be captured by the imaging unit 6. The imaging unit 6 can capture an image of a target to be read (not shown) that exists in an imaging area S inside the imaging field of view angle. In this embodiment, the imaging field of view angle is narrowed by the edge of the opening 2 of the housing 1 that houses and arranges the imaging unit 6, and the imaging area S is defined by a boundary surface that passes through the edge of the opening 2 and leads to the imaging unit 6 (the cross section of which is shown by a two-dot chain line in FIG. 1 ).

[0013] The light source 4 is disposed within the housing 1 and is located outside the imaging area S captured by the imaging unit 6. The light source 4 is, for example, an LED (Light Emitting Device) and emits illumination light. The protective plate 3 is located within the housing 1 on the opening 2 side of the light source 4 and the imaging unit 6. The illumination light emitted from the light source 4 passes through the protective plate 3 and is emitted through the opening 2. The protective plate 3 is disposed across the imaging area S. The illumination light is irradiated onto an imaging surface (not shown) on which the object to be read is located, illuminating the object to be read. The illumination light is, for example, diffused light, the boundary of which intersects with the central plane being indicated by a dashed line in FIG. 1.

[0014] The reflecting mirror 5 reflects light that passes inside the imaging field of view and is reflected by the imaging surface where the read target is located, toward the imaging element 61. In this embodiment, the reflecting mirror 5 is disposed at a position where at least a portion of the reflecting mirror 5 is interposed between the light source 4 and the imaging element 61. This results in a layout in which a portion of the illumination light emitted from the light source 4 is blocked by the reflecting mirror 5, preventing the illumination light emitted from the light source 4 from directly entering the imaging element 61. By providing the reflecting mirror 5, the optical system of the scanner 10 can be made compact.

[0015] In the scanner 10 having the above structure, it is possible that illumination light emitted from the light source 4 is reflected by the surface of the protective plate 3 and directly incident on the imaging element 61 of the imaging unit 6. In this embodiment, to prevent such reflection of the light source 4, the mounting angle of the protective plate 3 with respect to the housing 1 and the position of the light source 4 are set as follows. Note that, for ease of understanding, auxiliary lines that do not actually exist have been added to Figure 1.

[0016] First, the protective plate 3 was fixed to the housing 1 at an angle such that the surface of the protective plate 3 was approximately perpendicular to a boundary line (line AB) where the boundary on the light source 4 side of the imaging field of view of the imaging unit 6 intersects with the center plane. The protective plate 3 is, for example, an acrylic plate with a uniform thickness of about 1.5 mm, and therefore its surface includes a flat first surface 31 on the light source 4 side and a flat second surface 32 on the read target side. In other words, the surface of the protective plate 3 referred to here is at least one of the first surface 31 and the second surface 32.

[0017] The light source 4 is arranged outside the boundary line (line AB) of the imaging area S in the imaging unit 6. By arranging the light source 4 on the opposite side of the imaging area S across the boundary line (line AB) that is approximately perpendicular to the surface of the protection plate 3 in this way, it is possible to prevent the illumination light reflected on the surface of the protection plate 3 from entering the imaging element 61. In this case, the light source 4 may be arranged anywhere outside the boundary line (line AB).

[0018] Note that the surface of the protection plate 3 does not necessarily need to be perpendicular to the boundary line (line AB), and there is an appropriate range for the mounting angle of the protection plate 3. First, from the perspective of preventing reflections, the angle θ1 of ∠BDC on the imaging unit 6 side and imaging area S side of the surface 31 of the protection plate 3 with respect to the boundary line (line AB) should be greater than 90°. However, if the angle θ1 is made too large, the tilt angle of the protection plate 3 with respect to the imaging area S becomes undesirably large, adversely affecting the captured image. For example, if the angle θ1 is made too large, the barcode may become distorted and become unreadable. Therefore, it can be said that the angle θ1 is optimal at 90°.

[0019] In this embodiment, the protection plate 3 is attached to the housing 1 at an angle such that the angle θ2 of ∠BFD between the surface of the protection plate 3 and another boundary line (BE line) on the center plane opposite the light source 4 in the imaging field of view is greater than a predetermined angle. This angle is the minimum angle at which distortion does not occur in the read image, and is related to the imaging field of view. To read the target object well, it is ideal to attach the protection plate 3 at an angle where θ1 = θ2, but to prevent the above-mentioned reflection, θ1 needs to be greater than 90°.

[0020] As described above, according to the scanner 10 of this embodiment, by attaching the protective plate 3 at a predetermined angle to the imaging area S of the imaging unit 6 and arranging the light source 4 outside the imaging area S, it is possible to prevent reflection of the illumination light and improve reading accuracy. Furthermore, if the above conditions are satisfied, the layout of the light source 4 can be freely changed, thereby increasing the degree of freedom in design.

[0021] 2 is a schematic diagram showing the optical system of scanner 100 according to the first modified example. Scanner 100 has the same structure as scanner 10 of the above-described embodiment, except that it is provided with light-shielding members 101 and 102 near imaging unit 6. Therefore, components that function similarly to those of scanner 10 of the above-described embodiment are denoted by the same reference numerals, and their description will be omitted.

[0022] The light-shielding members 101 and 102 block undesired noise light from entering the image sensor 61 of the imaging unit 6. In this case, the noise light is illumination light that is directly incident from the light source 4, light reflected by components inside the housing 1, etc., and is light that becomes noise in the captured image. Unlike the above-described embodiment, in cases where the reflecting mirror 5 is not disposed between the image sensor 61 and the light source 4, the light-shielding members 101 and 102 of this modified example function effectively.

[0023] The scanner 100 according to the first modification can achieve the same effects as the above-described embodiment, and can further increase the degree of freedom in design, such as the layout of the reflecting mirror 5.

[0024] 3 is a schematic diagram showing the optical system of a scanner 200 according to a second modified example. Scanner 200 has the same structure as scanner 10 of the above-described embodiment, except that it does not have reflective mirror 5. Therefore, components that function similarly to scanner 10 of the above-described embodiment are denoted by the same reference numerals, and their description will be omitted. Scanner 200 according to this modified example can be applied to a fixed scanner in a POS terminal, for example.

[0025] This modification also has the same effects as the above-described embodiment.

[0026] 4 is a schematic diagram showing the optical system of scanner 300 according to the third modified example. Scanner 300 has substantially the same structure as scanner 200 according to the second modified example described above, except that it is provided with light-shielding members 301 and 302 near imaging unit 6. Therefore, here too, components that function in the same way as scanner 200 according to the second modified example are denoted by the same reference numerals, and their description will be omitted.

[0027] The light blocking members 301 and 302 block unwanted noise light from entering the image capturing element 61 of the image capturing unit 6. The scanner 3000 according to the third modified example can achieve the same effects as those of the above-described embodiment, and can obtain a better captured image.

[0028] As described above, the embodiments and their modifications of the present invention have been described. However, the above-described embodiments and their modifications are presented as examples and are not intended to limit the scope of the invention. The above-described embodiments and their modifications can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The above-described embodiments and their modifications are included within the scope of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. [Explanation of symbols]

[0029] 1...housing, 2...opening, 3...protective plate, 31...first surface, 32...second surface, 4...light source, 5...reflecting mirror, 6...imaging section, 61...imaging element, 10...scanner, 101, 102, 301, 302...light-shielding member, S...imaging area.

Claims

1. an imaging unit that captures an image of a reading target in an imaging area inside the imaging viewing angle; a light source disposed outside the imaging area and configured to irradiate the object to be read with illumination light; a protection plate disposed between the object to be read and the light source and across the imaging area, the protection plate having a flat surface with an angle of greater than 90° between the light source side boundary line of the imaging field of view and the imaging unit side and the imaging area side, and capable of transmitting the illumination light and the light reflected from the object to be read; A scanner having

2. the flat surface of the protection plate is at least one of a first surface of the protection plate on the light source side and a second surface of the protection plate on the read object side; The scanner of claim 1 .

3. a reflection mirror between the protection plate and the imaging unit, the reflection mirror reflecting the light reflected from the object to be read; The scanner of claim 1 .

4. At least a part of the reflecting mirror is located between the light source and the imaging unit. The scanner of claim 3 .

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