Two-dimensional image reader

Abstract

A two-dimensional image reader 10 comprises a light source that irradiates a reading object S with light, a light-condensing part that condenses light reflected from the reading object S, and a light-receiving part 14 that receives the light condensed by the light-condensing part. The light source comprises a plurality of line light sources 16 that emit linear light along a Y-axis direction. The light-condensing part comprises a plurality of rod lens arrays 18 each having a plurality of rod lenses arranged in the Y-axis direction. The rod lens arrays 18 and the line light sources 16 are disposed alternately at intervals in an X-axis direction orthogonal to the Y-axis direction.

Description

2D image reading device

[0001] The present invention relates to a two-dimensional image reading device capable of obtaining a two-dimensional image of a reading target.

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

[0003] Japanese Patent Application Publication No. 8-146343

[0004] However, in the case of the configuration disclosed in Patent Document 1, the lenses and light sources are sparsely arranged, which causes a problem of unevenness in the amount of light.

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a two-dimensional image reading device in which the unevenness in the amount of light is reduced.

[0006] In order to solve the above problems, one aspect of the present invention provides a two-dimensional image reading device including a light source that irradiates light onto an object to be read, a light collecting unit that collects light reflected from the object to be read, and a light receiving unit that receives the light collected by the light collecting unit, wherein the light source includes a plurality of line light sources that irradiate line-shaped light along a first direction, the light collecting unit includes a plurality of rod lens arrays each having a plurality of rod lenses arranged in the first direction, and the rod lens arrays and the line light sources are alternately arranged at intervals in a second direction perpendicular to the first direction.

[0007] Any combination of the above components and conversion of the present invention into a method, device, system, etc. are also valid aspects of the present invention.

[0008] According to the present invention, it is possible to provide a two-dimensional image reading device in which unevenness in the amount of light is reduced.

[0009] 1 is a schematic cross-sectional view of a two-dimensional image reading device according to an embodiment of the present invention; FIG. 2 is a schematic plan view of a light source and a light collecting unit; FIG. 3 is a diagram explaining the conditions for acquiring a two-dimensional image without any missing parts; FIG. 4 is a diagram explaining the conditions for arranging a line light source between rod lens arrays; FIG. 5 is a diagram showing two rod lens arrays arranged on an XY plane; FIG. 6 is a diagram showing an example of light intensity distribution in the longitudinal direction of the rod lens array; FIG. 7 is a diagram showing the calculation results of light intensity unevenness; FIG. 8 is a diagram showing two rod lens arrays arranged with a positional shift in the longitudinal direction; FIG. 9 is a diagram showing the calculation results of light intensity unevenness; FIG. 10 is a diagram showing an example in which the two-dimensional image reading device according to this embodiment is applied to a sole inspection device for diabetic patients.

[0010] The present invention will be described below based on preferred embodiments with reference to the drawings. The following configurations are for illustrative purposes only to facilitate understanding of the present disclosure, and the scope of the present disclosure is defined solely by the appended claims. Identical or equivalent components and parts shown in each drawing are designated by the same reference numerals, and redundant explanations will be omitted where appropriate. Furthermore, the dimensions of the components in each drawing are enlarged or reduced as appropriate to facilitate understanding. Furthermore, some components that are not important for explaining the embodiments in each drawing are omitted.

[0011] 1 is a schematic cross-sectional view of a two-dimensional image reading device 10 according to an embodiment of the present invention. Unlike scanning-type line reading devices used in scanners and the like, the two-dimensional image reading device 10 according to this embodiment is an image reading device that can acquire a two-dimensional image of a reading target S without scanning. 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 of a foot.

[0012] As shown in FIG. 1, the two-dimensional image reading device 10 includes a reading object placement section 12 on which the reading object S is placed, a light source that irradiates light onto the reading object S, a light focusing section that focuses light reflected from the reading object S, and a light receiving section 14 that receives the light focused by the light focusing section.

[0013] The read object placement section 12 may be a plate-like body. The observation object S is placed on an upper surface 12a of the read object placement section 12. The read object placement section 12 may be formed from a material such as glass or resin that transmits light from a light source. The read object placement section 12 is arranged so that the upper surface 12a is parallel to an XY plane that includes an X axis and a Y axis that is perpendicular to the X axis.

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

[0015] The two-dimensional image reading device 10 includes a plurality of line light sources 16 as light sources. The line light sources 16 emit linear light along the Y-axis direction. The line light sources 16 have a substantially uniform illuminance distribution in the longitudinal direction (Y-axis direction) (i.e., there is almost no unevenness in the amount of light in the longitudinal direction). The line light sources 16 have a light exit surface 16a extending in the Y-axis direction. The light exit surface 16a of the line light source 16 faces the lower surface 12b of the read object placement unit 12. The plurality of line light sources 16 are arranged at intervals in the X-axis direction, which is perpendicular to the Y-axis direction.

[0016] The two-dimensional image reading device 10 includes multiple rod lens arrays 18 as a light-focusing unit. Each rod lens array 18 has multiple rod lenses 20 arranged in a line in the Y-axis direction. The Y-axis direction corresponds to the longitudinal direction of the rod lens array 18. In the rod lens array 18, adjacent rod lenses 20 abut against each other. The rod lens array 18 may be a SELFOC® Lens Array (SLA), which integrates multiple rod lenses (gradient refractive index lenses) made of cylindrical glass rods with a refractive index distribution that increases the refractive index at the center. The multiple rod lens arrays 18 are spaced apart in the X-axis direction. Each rod lens 20 in the rod lens array 18 has a light incident surface 20a and a light exit surface 20b. The light incident surface 20a of the rod lens 20 faces the lower surface 12b of the read target placement unit 12. The light exit surface 20b of the rod lens 20 faces the light receiving surface of the light receiving unit 14.

[0017] 1 and 2, in the two-dimensional image reading device 10 according to this embodiment, 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 sources 16 are disposed alternately at intervals in the X-axis direction. Furthermore, in the two-dimensional image reading device 10 according to this embodiment, the rod lens arrays 18 and the line light sources 16 may be disposed so that the light incident surface 20a of the rod lens 20 and the light exit surface 16a of the line light source 16 are located on the same plane.

[0018] The 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 composed of a plurality of light receiving elements (photoelectric conversion elements) arranged two-dimensionally. The light receiving unit 14 is disposed so that the light receiving surfaces of the light receiving elements are positioned on the imaging plane of the rod lens array 18. The light receiving elements receive light imaged by the rod lens array 18 and output electrical signals.

[0019] In the two-dimensional image reading device 10 configured as described above, light from the line light source 16 is irradiated onto the read target S through the read target placement unit 12, and the light reflected from the read target S is collected by the rod lens array 18 and imaged on the light receiving unit 14, thereby reading the read target S. In the two-dimensional image reading device 10, the line light source 16, the rod lens array 18, and the light receiving unit 14 are arranged two-dimensionally, so two-dimensional images can be read without scanning the device. Since scanning is not required, two-dimensional images can be read in a short time, and vibrations during scanning do not pose any problems.

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

[0021] In the invention disclosed in the aforementioned Patent Document 1, the light sources and lenses are sparsely arranged on the same plane. When the light sources and lenses are sparsely arranged in this manner, unevenness in the amount of light is likely to occur. The rod lens array 18 and the line light source 16 used in the two-dimensional image reading device 10 according to this embodiment both have relatively little unevenness in the amount of light 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 can be realized in which unevenness in the amount of light in the longitudinal direction (Y-axis direction) is reduced.

[0022] An embodiment of the two-dimensional image reading device 10 will be described below.

[0023] 3 is a diagram illustrating the conditions for acquiring a two-dimensional image without any missing parts. In order to acquire a two-dimensional image without any missing parts, all parts must be within the field of view radius of the rod lens 20. Let D be the diameter of the rod lens 20, L be the distance between two adjacent rod lens arrays 18 (SLA distance), and X be the field of view radius of the rod lens 20. ０ Then, the condition for acquiring a two-dimensional image without any missing parts can be expressed as the following formula (1). By modifying equation (1), the following equation (2) can be obtained. Here, the parameters s and t are defined as in the following equations (3) and (4). Using the parameters s and t, equation (2) can be expressed as equation (5) below.

[0024] 4 is a diagram illustrating the conditions for arranging a line light source 16 between rod lens arrays 18. In order to arrange one line light source 16 between two adjacent rod lens arrays 18, the inter-SLA distance L must be greater than the lens diameter D. In other words, the following formula (6) must be satisfied: Both sides of equation (6) are expressed as the field of view radius X ０ Dividing by this gives the following equation (7). Using the parameters s and t, equation (7) can be expressed as equation (8) below.

[0025] From equations (6) and (8), the condition for arranging the line light source 16 between the rod lens arrays 18 and acquiring a two-dimensional image without any missing parts can be expressed as the following equation (9).

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

[0027] A gradient index lens is placed at the origin of the XY plane, and the amount of light at the center of the field of view is expressed as I ０ Then, the light intensity distribution I(x, y) of the gradient index lens alone can be expressed by the following equation (11).

[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 distance L between the SLAs 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 intensity distribution I(x, y) at coordinates (x, y) can be expressed as the following equation (12).

[0029] 6 shows an example of the light intensity distribution in the longitudinal direction of the rod lens array. For example, when the parameters s and t are certain values, the light intensity distribution in the longitudinal direction of the rod lens array 18 at x=a is as shown in FIG. 6. As shown in FIG. 6, the light intensity changes depending on the y coordinate position, and the maximum light intensity I ｍａｘ and minimum light intensity I ｍｉｎ Maximum light intensity I ｍａｘ and minimum light intensity I ｍｉｎ Using these, the light amount unevenness ΔI is expressed by the above formula (10).

[0030] Since ΔI varies depending on the x-coordinate position, the unevenness in the amount of light at the position x where ΔI is maximum is defined as ΔI ｍａｘ Using equation (12), ΔI ｍａｘ The value of the light intensity unevenness ΔI was calculated. ｍａｘ From the table shown in FIG. 7, when the parameters s=0.7 and t=1.4, for example, the light quantity unevenness ΔI ｍａｘ In the table shown in FIG. 7, the shaded area indicates the light intensity unevenness ΔI ｍａｘ represents a combination of parameters s and t for which the difference is 50% or less. The shaded area represents a combination of parameters s and t that does not satisfy the condition shown in the above formula (9).

[0031] In the table shown in FIG. 7, the shaded area indicates the light amount unevenness ΔI ｍａｘ This represents a combination of parameters s and t that satisfies the condition (i.e., equation (9)) for obtaining a two-dimensional image without any missing parts when the line light source 16 is disposed between the rod lens arrays 18. For simplicity, the area enclosed by the dashed line and shaded with dots in FIG. 7 is taken to be a suitable combination of parameters s and t. The area enclosed by the dashed line in FIG. 7 is expressed by the following equation (13). That is, the parameters s and t that satisfy the formulas (9) and (13) are used to determine the light amount unevenness ΔI ｍａｘ This is suitable for realizing a two-dimensional image reading device 10 in which the error is 50% or less.

[0032] Another embodiment will be described with reference to Fig. 8. In Fig. 8, a rod lens array 18B arranged at an SLA distance L is shifted in the longitudinal direction relative to a rod lens array 18A arranged on the Y axis. When multiple rod lens arrays 18 are arranged in the X axis direction, there is a possibility that the rod lens arrays 18 may be shifted in the longitudinal direction (Y axis direction) as shown in Fig. 8.

[0033] For each parameter s and t, the light intensity unevenness is calculated by changing the combination of the amount of deviation and the measurement position (x=a in FIG. 8), and the maximum value of the light intensity unevenness ΔI ｍａｘ FIG. 9 shows the light intensity unevenness ΔI ｍａｘ In the table shown in FIG. 9, the shaded area indicates the light intensity unevenness ΔI ｍａｘ The shaded area represents the combination of parameters s and t for which ΔI is 50% or less. The shaded area represents the combination of parameters s and t that does not satisfy the condition shown in the above formula (9). ｍａｘ Since the shift amount is set so that the maximum value is reached, the shift amount set varies depending on the parameters s and t. In addition, when the images of three or more rod lens arrays overlap, the light intensity unevenness ΔI ｍａｘ A different amount of deviation is set for each rod lens array so that the maximum value is reached.

[0034] In the table shown in FIG. 9, the shaded area indicates the light amount unevenness ΔI ｍａｘ is 50% or less, and satisfies the condition (i.e., equation (9)) for arranging the line light source 16 between the rod lens array 18 and acquiring a two-dimensional image without any missing parts. For simplification, the area enclosed by the dashed line and shaded with dots in Fig. 9 is taken as a suitable combination of parameters s and t. The area enclosed by the dashed line in Fig. 9 is expressed by the following equation (14). That is, the parameters s and t that satisfy the formulas (9) and (14) are used to determine the light amount unevenness ΔI ｍａｘ This is suitable for realizing a two-dimensional image reading device 10 in which the error is 50% or less.

[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 rows. As shown in Fig. 10, the rod lenses 20 are arranged in a bale-like fashion. The rod lens array 18A is arranged on the Y axis, and the rod lens array 18B is arranged at an SLA distance L. The SLA distance L is defined as the distance between nearby rod lenses in adjacent rod lens arrays.

[0036] Here, as in the above embodiment, the positional deviation of the rod lens array is taken into consideration, and the light intensity unevenness ΔI ｍａｘ FIG. 11 shows the light intensity unevenness ΔI ｍａｘ In the table shown in FIG. 11, the shaded area indicates the light intensity unevenness ΔI ｍａｘ represents a combination of parameters s and t for which the difference is 50% or less. The shaded area represents a combination of parameters s and t that does not satisfy the condition shown in the above formula (9).

[0037] In the table shown in FIG. 11, the shaded area indicates the light amount unevenness ΔI ｍａｘ is 50% or less, and satisfies the condition (i.e., formula (9)) for arranging the line light source 16 between the rod lens array 18 and acquiring a two-dimensional image without any missing parts. For simplification, the area enclosed by the dashed line and shaded with dots in FIG. 11 is taken as a suitable combination of parameters s and t. The area enclosed by the dashed line in FIG. 11 is expressed by the above formula (14). In other words, the parameters s and t that satisfy formulas (9) and (14) are used to reduce the light intensity unevenness ΔI ｍａｘ This is suitable for realizing a two-dimensional image reading device 10 in which the error is 50% or less.

[0038] FIG. 12 shows an example in which the two-dimensional image reading device 10 according to this embodiment is applied to a sole examination device for diabetic patients. In a sole examination device, it is important to observe changes in the shape of the sole across the width of the foot due to swelling or changes in hardness. As shown in FIG. 12, by aligning the longitudinal direction of the rod lens array 18 with the sole width, a high-quality image with less uneven light intensity across the sole width than conventional methods can be obtained. In this way, the two-dimensional image reading device 10 according to this embodiment can obtain an image that is more tailored to the purpose by aligning the direction with less uneven light intensity with the direction in which the object to be read needs to be viewed in detail.

[0039] The present invention has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications and changes are possible within the scope of the claims of the present invention, and that such modifications and changes also fall 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.

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

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

Claims

1. A two-dimensional image reading device comprising: a light source that irradiates light onto an object to be read; a light-collecting unit that collects light reflected from the object to be read; and a light-receiving unit that receives the light collected by the light-collecting unit, wherein the light source comprises a plurality of line light sources that irradiate line-shaped light along a first direction; the light-collecting unit comprises a plurality of rod lens arrays each having a plurality of rod lenses arranged in the first direction; and the rod lens arrays and the line light sources are arranged alternately at intervals in a second direction perpendicular to the first direction.

2. A two-dimensional image reading device according to claim 1, wherein the light incident surface of said rod lens and the light exit surface of said line light source are located on the same plane.

3. The field radius of the rod lens is X ０ , the diameter of the rod lens is D, the arrangement interval of the rod lens array is L, and the parameter s is s=D / X ０ , parameter t is L / X ０ Then, the following conditions:

3. The two-dimensional image reading device according to claim 1, wherein the following is satisfied:

4. The two-dimensional image reading device according to claim 3, further satisfying the following conditions: 0<s≦0.5 and 0<t≦1.9, 0.5<s≦0.8 and 0<t≦1.8, and 0.8<s≦1.1 and 0<t≦1.

6.

5. The two-dimensional image reading device according to claim 3, further satisfying 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, and 0.7<s≦0.9 and 0<t≦1.3.

Images