2D image reading device

Abstract

The two-dimensional image reading device 10 includes a light source that irradiates light onto a reading target S, a condensing unit that condenses the light reflected from the reading target S, and a light receiving unit 14 that receives the light condensed by the condensing unit. The light source includes a plurality of line light sources 16 that irradiate line-shaped light along the Y-axis direction. The condensing unit includes a plurality of rod lens arrays 18 having a plurality of rod lenses arranged in the Y-axis direction. The rod lens array 18 and the line light source 16 are alternately arranged at intervals in the X-axis direction orthogonal to the Y-axis direction.

Description

Technical Field

[0001] The present invention relates to a two-dimensional image reading device capable of acquiring a two-dimensional image to be read.

Background Art

[0002] Conventionally, as a two-dimensional image reading device, one in which a light source and a lens are arranged on the same plane is known (see, for example, Patent Document 1). By integrating the light source and the lens on the same plane, the device configuration can be miniaturized.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the case of the configuration disclosed in Patent Document 1, since the lenses and the light sources are sparsely arranged, there is a problem that uneven light amount occurs.

[0005] The present invention has been made in view of such circumstances, and an object thereof is to provide a two-dimensional image reading device with reduced uneven light amount.

Means for Solving the Problems

[0006] To solve the above problems, a two-dimensional image reading device according to an aspect of the present invention includes a light source that irradiates light onto a reading target, a condensing unit that condenses the light reflected from the reading target, and a light receiving unit that receives the light condensed by the condensing unit. The two-dimensional image reading device is characterized in that the light source includes a plurality of line light sources that irradiate line-shaped light along a first direction. The condensing unit includes a plurality of rod lens arrays each having a plurality of rod lenses arranged in the first direction. The rod lens arrays and the line light sources are alternately arranged with a gap in a second direction orthogonal to the first direction.

[0007] In addition, any combination of the above components, as well as those obtained by converting the expression of the present invention among methods, devices, systems, etc., are also effective as aspects of the present invention.

Advantages of the Invention

[0008] According to the present invention, a two-dimensional image reading device with reduced light quantity unevenness can be provided.

Brief Description of the Drawings

[0009]

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Embodiments for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The following configurations are for the purpose of exemplification for understanding the present disclosure, and the scope of the present disclosure is determined only by the appended claims. The same or equivalent components and members shown in each drawing are denoted by the same reference numerals, and repeated descriptions will be omitted as appropriate. In addition, the dimensions of the members in each drawing are shown enlarged or reduced as appropriate for easy understanding. Also, a part of the members that are not important for explaining the embodiments in each drawing is omitted and shown.

[0011] FIG. 1 is a schematic cross-sectional view of a two-dimensional image reading device 10 according to an embodiment of the present invention. The two-dimensional image reading device 10 according to the present embodiment is an image reading device capable of acquiring a two-dimensional image of a reading target S without performing scanning, unlike a scanning type line reading device used in a scanner device or the like. The reading target S is not particularly limited and may be a photograph, a document, or the like. Alternatively, the reading target S may be a part of the human body such as the sole.

[0012] As shown in FIG. 1, the two-dimensional image reading device 10 includes a reading target placement unit 12 on which the reading target S is placed, a light source that irradiates the reading target S with light, a condensing unit that condenses the light reflected from the reading target S, and a light receiving unit 14 that receives the light condensed by the condensing unit.

[0013] The placement unit 12 for the object to be read may be a plate-shaped body. The object S to be observed is placed on the upper surface 12a of the placement unit 12 for the object to be read. The placement unit 12 for the object to be read may be formed of a material such as glass or resin that transmits light from a light source. The placement unit 12 for the object to be read is arranged such that the upper surface 12a is parallel to the XY plane including the X-axis and the Y-axis orthogonal thereto.

[0014] A light source and a condensing unit are arranged below the placement unit 12 for the object to be read in the Z-axis direction. The Z-axis is an axis perpendicular to both the X-axis and the Y-axis. FIG. 2 is a schematic plan view of the light source and the condensing unit.

[0015] The two-dimensional image reading device 10 includes a plurality of line light sources 16 as light sources. The line light source 16 irradiates line-shaped light along the Y-axis direction. As the line light source 16, one having a substantially uniform illuminance distribution in the longitudinal direction (Y-axis direction) (that is, having almost no light quantity unevenness in the longitudinal direction) is used. The line light source 16 has a light emitting surface 16a extending in the Y-axis direction. The light emitting surface 16a of the line light source 16 faces the lower surface 12b of the placement unit 12 for the object to be read. The plurality of line light sources 16 are arranged at intervals in the X-axis direction orthogonal to the Y-axis direction.

[0016] The two-dimensional image reading device 10 includes a plurality of rod lens arrays 18 as condensing units. Each rod lens array 18 has a plurality of rod lenses 20 arranged in a row in the Y-axis direction. The Y-axis direction is the longitudinal direction of the rod lens array 18. In the rod lens array 18, adjacent rod lenses 20 are in contact with each other. The rod lens array 18 may be a self-focus (registered trademark) lens array (SLA) in which a large number of rod lenses (refractive index distribution type lenses) made of columnar glass rods having a refractive index distribution formed so that the refractive index of the central portion is high are arranged and integrated. The plurality of rod lens arrays 18 are arranged at intervals in the X-axis direction. Each rod lens 20 of the rod lens array 18 has a light incident surface 20a and a light emitting surface 20b. The light incident surface 20a of the rod lens 20 faces the lower surface 12b of the placement unit 12 for the object to be read. The light emitting surface 20b of the rod lens 20 faces the light receiving surface of the light receiving unit 14.

[0017] In the two-dimensional image reading device 10 according to this embodiment, as shown in FIGS. 1 and 2, one line light source 16 is disposed between two adjacent rod lens arrays 18. That is, the rod lens arrays 18 and the line light source 16 are alternately arranged at intervals in the X-axis direction. Further, in the two-dimensional image reading device 10 according to this embodiment, the rod lens array 18 and the line light source 16 may be arranged such that the light incident surface 20a of the rod lens 20 and the light emission surface 16a of the line light source 16 are located on the same plane.

[0018] A light receiving unit 14 is disposed below the rod lens array 18 and the line light source 16 in the Z-axis direction. The light receiving unit 14 is formed by arranging a plurality of light receiving elements (photoelectric conversion elements) in a two-dimensional manner. The light receiving unit 14 is arranged such that the light receiving surface of the light receiving element is located on the imaging surface of the rod lens array 18. The light receiving element receives the light imaged by the rod lens array 18 and outputs an electrical signal.

[0019] In the two-dimensional image reading device 10 configured as described above, the irradiation light from the line light source 16 is irradiated onto the reading target S through the reading target placement unit 12, and the reflected light from the reading target S is condensed by the rod lens array 18 and imaged on the light receiving unit 14, whereby the reading target S is read. In the two-dimensional image reading device 10, since the line light source 16, the rod lens array 18, and the light receiving unit 14 are arranged two-dimensionally, it is possible to read a two-dimensional image without scanning the device. Since scanning is not required, it is possible to read a two-dimensional image in a short time, and vibrations during scanning do not pose a problem.

[0020] In the two-dimensional image reading device 10 according to this embodiment, as described above, the rod lens array 18 and the line light source 16 are alternately arranged in the X-axis direction. By adopting such an arrangement, a compact two-dimensional image reading device can be realized.

[0021] In the invention disclosed in the above Patent Document 1, the light source and the lens are sparsely arranged on the same plane. When the light source and the lens are arranged sparsely in this way, uneven light quantity is likely to occur. Both the rod lens array 18 and the line light source 16 used in the two-dimensional image reading device 10 according to the present embodiment have relatively little uneven light quantity in the longitudinal direction. Therefore, by combining the rod lens array 18 and the line light source 16, a two-dimensional image reading device 10 with reduced uneven light quantity in the longitudinal direction (Y-axis direction) can be realized.

[0022] Hereinafter, an embodiment of the two-dimensional image reading device 10 will be described.

[0023] FIG. 3 is a diagram for explaining the conditions for acquiring a complete two-dimensional image. In order to acquire a complete two-dimensional image, it is necessary that all locations are within the viewing radius of the rod lens 20. Let the diameter of the rod lens 20 be D, the distance between two adjacent rod lens arrays 18 (distance between SLA) be L, and the viewing radius of the rod lens 20 be X0. Then, the conditions for acquiring a complete two-dimensional image can be expressed as the following formula (1).

Equation

Equation

Equation

Equation

Equation

[0024] FIG. 4 is a diagram for explaining the conditions for arranging the line light source 16 between the rod lens arrays 18. In order to arrange one line light source 16 between two adjacent rod lens arrays 18, the SLA distance L needs to be larger than the lens diameter D. That is, the following formula (6) must hold.

Equation

Equation

Equation

[0025] From formula (6) and formula (8), the conditions for arranging the line light source 16 between the rod lens arrays 18 and obtaining a complete two-dimensional image can be expressed as the following formula (9).

Equation

[0026] As described above, in the two-dimensional image reading device 10 according to the present embodiment, the line light source 16 and the rod lens array 18 are used. The line light source 16 has a substantially uniform illuminance distribution in the longitudinal direction and has almost no light quantity unevenness. On the other hand, since the rod lens array 18 is an element in which refractive index distribution type lenses are densely arranged, although the light quantity unevenness is reduced compared to the case where the lenses are arranged sparsely, there is a possibility that slight light quantity unevenness may occur in the longitudinal direction. Here, the conditions under which the light quantity unevenness in the longitudinal direction is 50% or less, which is the upper limit that can be corrected by image processing, will be described. In this specification, the maximum value of the light quantity is I max , the minimum value of the light quantity is I min , when defined as the light quantity unevenness ΔI is defined as the following formula (10).

Number

[0027] When a refractive index distribution type lens is placed at the origin of the XY plane and the amount of light at the center of the field of view is I0, the light amount distribution I(x, y) of the refractive index distribution type lens alone can be expressed by the following equation (11).

Number

[0028] Figure 5 shows two rod lens arrays arranged on the XY plane. As shown in Figure 5, one rod lens array 18A is arranged on the Y axis, and another rod lens array 18B is arranged at a position of SLA pitch L in the X axis direction from the origin (0, 0). Here, it is assumed that there is no misalignment of the rod lenses in the longitudinal direction (Y axis direction) of the rod lens array. In this case, the light amount distribution I(x, y) at the coordinates (x, y) can be expressed by the following equation (12).

Number

[0029] Figure 6 shows an example of the light amount distribution in the longitudinal direction of the rod lens array. For example, when the parameters s and t are certain values, it is assumed that the light amount distribution in the longitudinal direction of the rod lens array 18 at x = a is as shown in Figure 6. As shown in Figure 6, the light amount changes according to the y coordinate position, and the maximum light amount I max and the minimum light amount I min exist. Using the maximum light amount I max and the minimum light amount I min , the light amount unevenness ΔI is expressed by the above equation (10).

[0030] Since ΔI varies depending on the x coordinate position, the light amount unevenness at the position x where ΔI is maximum is defined as ΔI max . Using equation (12), the values of ΔI max for each parameter s and t were calculated. Figure 7 shows the light amount unevenness ΔI maxShows the calculation results. From the table shown in FIG. 7, for example, when the parameters s = 0.7 and t = 1.4, the light quantity unevenness ΔI max = 30% can be seen. In the table shown in FIG. 7, the area shaded with dots represents the combination of parameters s and t for which the light quantity unevenness ΔI max is 50% or less. Also, the area shaded with diagonal lines represents the combination of parameters s and t that deviate from the conditions shown in the above formula (9).

[0031] In the table shown in FIG. 7, the area shaded with dots represents the light quantity unevenness ΔI max is 50% or less, and represents the combination of parameters s and t that satisfy the condition (that is, formula (9)) for arranging the line light source 16 between the rod lens arrays 18 and obtaining a complete two-dimensional image. Here, for simplicity, the area within the region surrounded by the broken line and shaded with dots in FIG. 7 is set as the combination of suitable parameters s and t. The region surrounded by the broken line in FIG. 7 is represented by the following formula (13).

Equation

[0032] Referring to FIG. 8, another embodiment will be described. In FIG. 8, the rod lens array 18B arranged at the position of the SLA interval L is displaced in the longitudinal direction with respect to the rod lens array 18A arranged on the Y axis. When arranging the plurality of rod lens arrays 18 in the X-axis direction, as shown in FIG. 8, the rod lens arrays 18 may be displaced in the longitudinal direction (Y-axis direction).

[0033] For each parameter s and t, the light quantity unevenness is calculated by changing the combination of the displacement amount and the measurement position (x = a in FIG. 8), and the maximum value ΔI of the light quantity unevenness max is obtained. FIG. 9 shows the calculation results of the light quantity unevenness ΔI max In the table shown in FIG. 9, the area shaded with dots represents the light quantity unevenness ΔI maxrepresents the combination of parameters s and t for which it is 50% or less. Also, the hatched area represents the combination of parameters s and t that deviate from the conditions shown in the above formula (9). This time, since the deviation amount is set so that ΔI max becomes maximum, the deviation amounts set by each parameter s and t are different. Also, when images of three or more rod lens arrays overlap, different deviation amounts are set for each rod lens array so that the light quantity unevenness ΔI max becomes maximum.

[0034] In the table shown in FIG. 9, the area hatched with dots represents the combination of parameters s and t for which the light quantity unevenness ΔI max is 50% or less and which satisfies the condition (i.e., formula (9)) for arranging the line light source 16 between the rod lens arrays 18 and obtaining a complete two-dimensional image. Here, for simplicity, the area within the region surrounded by the broken line and hatched with dots in FIG. 9 is taken as the combination of suitable parameters s and t. The region surrounded by the broken line in FIG. 9 is represented by the following formula (14).

Equation

[0035] Another embodiment will be described with reference to FIG. 10. FIG. 10 shows rod lens arrays 18A and 18B having rod lenses 20 arranged in two columns. As shown in FIG. 10, the rod lenses 20 are arranged in a stack. The rod lens array 18A is arranged on the Y axis, and the rod lens array 18B is arranged at the position of the SLA interval L. The SLA interval L is defined as the distance between adjacent rod lenses of adjacent rod lens arrays.

[0036] Here too, similar to the above embodiment, the positional deviation of the rod lens array is taken into account, and the light quantity unevenness ΔI max is calculated. FIG. 11 shows the light quantity unevenness ΔI maxShows the calculation result. In the table shown in Fig. 11, the areas shaded with dots represent the combinations of parameters s and t for which the light quantity unevenness ΔI max is 50% or less. Also, the areas shaded with diagonal lines represent the combinations of parameters s and t that deviate from the conditions shown in the above formula (9).

[0037] In the table shown in Fig. 11, the areas shaded with dots are such that the light quantity unevenness ΔI max is 50% or less, and represents the combinations of parameters s and t that satisfy the condition (i.e., formula (9)) for arranging the line light source 16 between the rod lens arrays 18 and obtaining a complete two-dimensional image without missing parts. Here, for simplicity, the area within the region surrounded by the broken line and shaded with dots in Fig. 11 is taken as the combination of suitable parameters s and t. The region surrounded by the broken line in Fig. 11 is represented by the above formula (14). That is, the parameters s and t that satisfy formula (9) and formula (14) are suitable for realizing the two-dimensional image reading device 10 in which the light quantity unevenness ΔI max is 50% or less.

[0038] Fig. 12 shows an example in which the two-dimensional image reading device 10 according to the present embodiment is applied to a sole inspection device for diabetic patients. In the sole inspection device, it is important to observe the shape change in the sole width direction due to swelling and hardness change of the sole. As shown in Fig. 12, by aligning the longitudinal direction of the rod lens array 18 with the sole width direction, it is possible to obtain a high-quality image with less light quantity unevenness in the sole width direction than in the prior art. Thus, the two-dimensional image reading device 10 according to the present embodiment can obtain an image more suitable for the purpose by aligning the direction with less light quantity unevenness with the direction in which the object to be read is to be examined in detail.

[0039] As described above, the present invention has been described based on the embodiments. It is understood by those skilled in the art that these embodiments are illustrative, and various modifications and changes are possible within the scope of the claims of the present invention, and such modified examples and changes are also within the scope of the claims of the present invention. Therefore, the descriptions and drawings in this specification should be treated as illustrative rather than restrictive.

Industrial Applicability

[0040] The present invention can be used in a two-dimensional image reading device.

Explanation of Signs

[0041] 10 Two-dimensional image reading device, 12 Reading target placement unit, 14 Light receiving unit, 16 Line light source, 18 Rod lens array, 20 Rod lens.

Claims

1. A light source that irradiates light onto an object to be read, a condensing unit that condenses the light reflected from the object to be read, a light receiving unit that receives the light condensed by the condensing unit, A two-dimensional image reading device comprising: The light source includes a plurality of line light sources that irradiate line-shaped light along a first direction, The condensing unit includes a plurality of rod lens arrays each having a plurality of rod lenses arranged in the first direction, The two-dimensional image reading device is characterized in that the rod lens array and the line light source are alternately arranged at intervals in a second direction orthogonal to the first direction.

2. The two-dimensional image reading device according to claim 1, characterized in that a light incident surface of the rod lens and a light emitting surface of the line light source are located on the same plane.

3. Let the viewing radius of the rod lens be X ０ , the diameter of the rod lens be D, the arrangement interval of the rod lens array be L, and the parameter s be s = D / X ０ , and the parameter t be L / X ０ When this is the case, the following conditions: 【Number 1】 The two-dimensional image reading device according to claim 1 or 2, characterized by satisfying.

4. Furthermore, the following conditions: 0 < s ≤ 0.5 and 0 < t ≤ 1.9 0.5 < s ≤ 0.8 and 0 < t ≤ 1.8 0.8 < s ≤ 1.1 and 0 < t ≤ 1.6 The two-dimensional image reading device according to claim 3, characterized by satisfying.

5. Furthermore, the following conditions: 0 < s ≤ 0.3 and 0 < t ≤ 1.9 0.3 < s ≤ 0.5 and 0 < t ≤ 1.8 0.5 < s ≤ 0.7 and 0 < t ≤ 1.6 0.7 < s ≤ 0.9 and 0 < t ≤ 1.3 The two-dimensional image reading device according to claim 3, characterized by satisfying.

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