Illumination apparatus, image reading apparatus, image forming apparatus, inspection apparatus, and illumination method

Abstract

To improve irradiation efficiency to a reading object without performing complicated processing to a light guide body.SOLUTION: And a second light source unit that is disposed to face the first light source unit and irradiates the region to be irradiated with light, in which the region to be irradiated has a region in which light irradiated in a direction of a main optical axis by the first light source unit and light irradiated in the direction of the main optical axis by the second light source unit overlap each other, and the light irradiated to the region by the first light source unit and the light irradiated to the region by the second light source unit have different wavelengths.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an illumination device, an image reading device, an image forming device, an inspection device, and an illumination method. [Background technology]

[0002] In the illumination devices of conventional image reading devices, there are known technologies for ensuring sufficient light intensity by arranging multiple light-emitting diodes (LEDs) in an array, and for irradiating light of multiple wavelengths by alternately mounting two types of LEDs on the same board.

[0003] Patent Document 1 discloses a configuration in an illumination device for an image reading device in which multiple types of LEDs are arranged in two rows in an array to ensure a sufficient amount of light, and the shape of the exit surface of a light guide is curved to change the exit angle of the light emitted from the light guide, thereby irradiating the object to be read with light evenly. Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the conventional technology, there were issues such as poor illumination efficiency on the target because the irradiation direction of each of the two rows of LED arrays was tilted relative to the target, and the need for complex processing of the light guide, which increased manufacturing costs.

[0005] The present invention has been made in view of the above, and has an object to efficiently irradiate a target object with light of different wavelengths without performing complex processing on a light guide. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a light source device is provided which includes a first light source unit which irradiates light onto an irradiated area, and a second light source unit which is arranged opposite the first light source unit and irradiates light onto the irradiated area, wherein the irradiated area has an area where the light irradiated by the first light source unit in the direction of the main optical axis and the light irradiated by the second light source unit in the direction of the main optical axis overlap, and the light irradiated onto the area by the first light source unit and the second light source unit have mutually different wavelengths. [Effects of the Invention]

[0007] According to the present invention, it is possible to efficiently irradiate light of different wavelengths onto an object to be read without performing complex processing on a light guide. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side view showing an outline of an image reading device provided with an illumination device according to a first embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of the lighting device according to the first embodiment. [Figure 3] FIG. 3 is a diagram illustrating the arrangement positions of light sources in the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating the effects of the configuration of the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating another effect of the configuration of the first embodiment. [Figure 6] FIG. 6 is a diagram showing how reading is performed when either of the two types of light emitting elements is unevenly arranged in each light source section. [Figure 7] FIG. 7 is a diagram showing how reading is performed when two types of light emitting elements are alternately arranged in an array on each light source unit. [Figure 8] FIG. 8 is a diagram showing an example of a common light source unit and a lighting device. [Figure 9] FIG. 9 is a diagram showing another example of the configuration of the lighting device according to the first embodiment. [Figure 10]FIG. 10 is a diagram illustrating an example of the configuration of a lighting device according to the second embodiment. [Figure 11] FIG. 11 is a diagram illustrating the arrangement positions of light sources in the second embodiment. [Figure 12] FIG. 12 is a diagram illustrating the effect of the configuration of the second embodiment. [Figure 13] FIG. 13 is a diagram illustrating the effect of reading in the image reading device according to the second embodiment. [Figure 14] FIG. 14 is a diagram illustrating another effect of reading in the image reading device according to the second embodiment. [Figure 15] FIG. 15 is a diagram illustrating an example of the configuration of a lighting device according to the third embodiment. [Figure 16] FIG. 16 is a diagram illustrating the effects of the configuration of the third embodiment. [Figure 17] FIG. 17 is a schematic cross-sectional view showing an example of the configuration of a mechanism of an image forming apparatus according to the fourth embodiment. [Figure 18] FIG. 18 is a diagram showing an example of the configuration of an illumination device included in an inspection device according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an illumination device, an image reading device, an image forming device, an inspection device, and an illumination method will be described in detail with reference to the accompanying drawings.

[0010] (First embodiment) 1 is a side view showing an overview of an image reading device 30 equipped with an illumination device 13 according to this embodiment. The image reading device 30 is, for example, a sheet-through type, and includes a reading unit 10 (flatbed scanner) and an automatic document feeder (ADF) 20.

[0011] The reading unit 10 includes a contact glass 11, a reference white plate 12, an illumination device 13, a first carriage 14, a second carriage 15, a lens 16, a sensor board 17, a scanner motor 18, and a reading window 19. The sensor board 17 includes a line sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor).

[0012] The ADF 20 is provided above the reading unit 10 and automatically feeds and transports the originals 22. The ADF 20 includes an original tray 21, a transport drum 23, a paper discharge roller 24, a paper discharge tray 25, and a background unit 26. The background unit 26 also serves to hold down the transported originals 22 when they are read. The originals 22 are transported one by one by the ADF 20, and are exposed to light by the illumination device 13 when they pass the reading position of the reading window 19. The reflected light from the exposed originals 22 is reflected by the mirrors of the first carriage 14 and the second carriage 15, passes through the lens 16, and forms a reduced image on the light receiving surface of the line sensor on the sensor board 17.

[0013] Also, in flatbed reading, in which the original 22 is fixed on the contact glass 11 and scanned by the first carriage 14 and second carriage 15, the original 22 placed on its surface is exposed to light by the illumination device 13 located below the contact glass 11. Light reflected from the original 22 is reflected by the mirrors of the first carriage 14 and second carriage 15, passes through the lens 16, and is reduced and imaged on the light-receiving surface of the line sensor on the sensor board 17. At this time, the first carriage 14 moves at a speed V along the longitudinal direction of the original 22, and simultaneously, in conjunction with this, the second carriage 15 moves at a speed V / 2, half that of the first carriage 14, to read the entire longitudinal direction of the original 22.

[0014] 2 is a diagram showing an example of the configuration of illumination device 13 according to this embodiment. Illumination device 13 is configured with a pair of light source units (first light source unit 1301 and second light source unit 1302), each including a first light source unit 1311 and a second light source unit 1312 for irradiating light onto illuminated surface 220 of document 22. Furthermore, first light source unit 1311 is disposed in the longitudinal direction of first light source unit 1301, and second light source unit 1312 is disposed in the longitudinal direction of second light source unit 1302. Hereinafter, first light source unit 1301 and second light source unit 1302 may be referred to as respective light source units, and first light source unit 1311 and second light source unit 1312 may be referred to as respective light source units.

[0015] The illuminated area 221 is an area onto which each light source unit is irradiated by the illumination device 13, and corresponds to an image reading line (a line at a reading position) when the image reading device 30 reads an image using a line sensor. The longitudinal direction of the illuminated area 221 is the main scanning direction of image reading. Note that FIG. 2 is a view of each light source unit and the original 22 viewed obliquely from above, and the surface on which each light source unit is mounted for each light source unit and the surface of the original 22 opposite to the reading surface are visible. Also, although the illuminated surface 220 is located on the underside of the original 22, the position of the illuminated area 221 is not limited to the underside of the original 22. For example, the illuminated area 221 may be an area having a width extending from above to below the original 22.

[0016] The light source units are arranged to face each other across a perpendicular line 222 to the surface of the irradiated region 221. The surface of the irradiated region 221 is a surface parallel to the irradiated surface 220 in the irradiated region 221. This surface may be the irradiated surface 220 in the irradiated region 221, a surface parallel to the irradiated surface 220 in the irradiated region 221 and positioned above the irradiated surface 220, or a surface parallel to the irradiated surface 220 in the irradiated region 221 and positioned below the irradiated surface 220 in the irradiated region 221. The perpendicular line 222 extends from each position in the longitudinal direction (image reading line) of the irradiated region 221. The main optical axes of light from each light source unit irradiated from positions facing each other across the perpendicular line 222 are configured to face the irradiated region 221. In other words, the light source units are arranged so that the main optical axes of light irradiated from positions facing each other across the perpendicular line 222 intersect at the irradiated region 221. Here, the main optical axis is the optical center axis of each light source unit and is the radiation direction in which the luminous intensity of the light emitted by each light source unit is maximum. Furthermore, the opposing positions across the perpendicular line 222 are the first position in the first light source unit and the second position closest to the first position in the second light source unit, and are positions where the line connecting the respective positions is perpendicular to the perpendicular line 222.

[0017] Each light source unit has a light-emitting element A and a light-emitting element B that emit light of different wavelengths. The light emitted from each light source unit from positions facing each other across a perpendicular line 222 has different wavelengths. While FIG. 2 shows an example in which point light sources, light-emitting element A and light-emitting element B, are alternately arranged in an array in each light source unit, each light source unit may be configured in any way as long as it satisfies the following conditions (1) and (2). (1) The main optical axes of light irradiated from opposing positions across the perpendicular line 222 intersect in the irradiated region 221. That is, the irradiated region 221 has an area where the light irradiated from each light source unit in the direction of the main optical axis overlaps. (2) The light beams emitted from opposing positions across the perpendicular line 222 have different wavelengths. That is, the light beams emitted from the light source units onto the overlapping region have different wavelengths.

[0018] In FIG. 2, the light-emitting element A of the first light source unit 1311 and the light-emitting element B of the second light source unit 1312 are disposed at positions facing each other across the perpendicular line 222, and their main optical axes intersect at the irradiated region 221, thereby satisfying the above-mentioned condition (1). Furthermore, the light-emitting element A and the light-emitting element B emit light of different wavelengths, thereby satisfying the above-mentioned condition (2). As described below, the light-emitting element may be mounted on each light source unit, or may be mounted at a position away from each light source unit, and light may be emitted from the position of each light source unit using a light guide or the like, as in a light guide system. Furthermore, the positions facing each other across the perpendicular line 222 may be equidistant from the perpendicular line 222. In this case, the angles that the main optical axes of the light irradiated from each position make with respect to a plane parallel to the irradiated surface 220 in the irradiated region 221 are the same.

[0019] 3 is a diagram illustrating the arrangement of light sources in this embodiment. Each diagram shows the first light source unit 1311 and the second light source unit 1312 as viewed from the illuminated area 221. The dotted line between the light source units in each diagram indicates the center line of the illuminated area 221 in the main scanning direction, and the foot of a perpendicular line 222 extending from each main scanning position (each position on the image reading line) is located on this dotted line. Furthermore, the wavelength of light emitted from the light source indicated by light spots is different from the wavelength of light emitted from the light source indicated by dark spots.

[0020] 3(a) indicate positions where light is emitted from the first light source unit 1311, and irradiation positions 2-1, 2-2, . . . , 2-n indicate positions where light is emitted from the second light source unit 1312. Irradiation positions 1-m (m = 1, 2, . . . , n) and irradiation position 2-m are opposite positions across a perpendicular line 222, and the line connecting irradiation positions 1-m and 2-m is perpendicular to the perpendicular line 222. In this example, light-emitting elements may be mounted at each irradiation position, or light-emitting elements may be mounted at positions away from each light source unit, and light may be emitted from each irradiation position using a light guide or the like.

[0021] 3(b) shows an example in which two types of light-emitting elements A and B are alternately arranged in an array at each irradiation position in FIG. 3(a), and is similar to the first light source unit 1311 and the second light source unit 1312 shown in FIG. 2. With this configuration, a light guide is not required, and adjustment of the light guide position of the light guide is also not required, so the effects of this embodiment can be achieved without increasing the processing costs of the light guide or the number of mounting steps. In both FIGS. 3(a) and 3(b), the light source units are arranged so that the optical axes of light irradiated from opposing positions across the perpendicular line 222 intersect in the irradiation area 221.

[0022] FIG. 4 illustrates the effects of the configuration of this embodiment. FIG. 4(a) shows the configuration and illuminance distribution of a conventional light source unit, and FIG. 4(b) shows the configuration of the light source unit of this embodiment and the illuminance distribution of each light-emitting element. Here, the solid line in the graph represents the illuminance distribution by light-emitting element A (or B) in the illuminated area 221 (the image reading line when a line sensor is used), the vertical axis of the graph represents illuminance, and the horizontal axis represents the main scanning position (the coordinate in the main scanning direction on the image reading line). In FIG. 4(a), graph (aA) represents the illuminance distribution by light-emitting element A of the conventional light source unit, and graph (aB) represents the illuminance distribution by light-emitting element B of the conventional light source unit. In FIG. 4(b), graph (bA) represents the illuminance distribution by light-emitting element A of the light source unit of this embodiment, and graph (bB) represents the illuminance distribution by light-emitting element B of the light source unit of this embodiment. In addition, the dotted lines in graphs (bA) and (bB) represent the contribution of the first light source unit 1311 to the illuminance distribution, and the dashed lines represent the contribution of the second light source unit 1312 to the illuminance distribution.

[0023] Conventional light source units can only emit light from one type of light-emitting element at the ends of the main scanning position (the left or right end of the illuminance distribution graph). In addition, the illuminance of one light-emitting element peaks at the main scanning position corresponding to the main optical axis of the light-emitting element, and decreases the further away from that position it is. Therefore, as shown in Figure 4(a), the illuminance of each light-emitting element decreases at the ends of the main scanning position. In addition, because there is a gap in the pitch interval between each light-emitting element, it is not possible to ensure a flat illuminance distribution for each light-emitting element.

[0024] On the other hand, as shown in FIG. 4(b), in the light source unit of this embodiment, light-emitting elements A and B are arranged to irradiate light of different wavelengths from positions facing each other across a perpendicular line 222. The light irradiated from the light-emitting element A (or B) of each light source unit overlaps in the irradiated region 221, resulting in an illuminance distribution as shown in the graph indicated by the solid line in FIG. 4(b). As described above, in this embodiment, even at the end of the main scanning position, light from the light-emitting element A (or B) of the first light source unit 1311 and light from the light-emitting element B (or A) of the second light source unit 1312 are irradiated, thereby alleviating the problem of reduced illuminance of each light-emitting element. Furthermore, in this embodiment, light-emitting elements of the same type are arranged opposite the gaps between the light-emitting elements A (or B), which solves the problem of insufficient flatness due to large pitch intervals between the light-emitting elements.

[0025] 5A and 5B are diagrams illustrating other effects of the configuration of this embodiment. FIG. 5A shows the relationship between a conventional light source unit and an irradiated surface 220, and FIG. 5B shows the relationship between the light source unit and an irradiated surface 220 of this embodiment. In this example, each light source unit is composed of a first light source unit 1311 and a second light source unit 1312. The arrows indicate light emitted from positions facing each other across a perpendicular line 222, with solid arrows indicating light in the direction of the main optical axis and dotted and dashed arrows indicating light in directions different from the main optical axis. The intensity of the irradiated light is strongest in the direction of the main optical axis, weaker in the direction of the dotted line, and weakest in the direction of the dashed line.

[0026] In a conventional light source unit, as shown in Fig. 5(a), the main optical axes of the first light source unit 1311 and the second light source unit 1312 are perpendicular to the irradiated surface 220, so attenuated light is irradiated onto the irradiated area 221. On the other hand, in this embodiment, as shown in Fig. 5(b), the main optical axes of the first light source unit 1311 and the second light source unit 1312 intersect at the irradiated area 221, so light with the maximum intensity is irradiated onto the irradiated area 221, and it can be seen that irradiation efficiency is good.

[0027] Next, the effect of arranging two types of light-emitting elements that emit light of different wavelengths alternately in an array on each light source unit will be described with reference to Figures 6 and 7. Such an arrangement of light-emitting elements corresponds to the example shown in Figure 2 and Figure 3(b).

[0028] FIG. 6 illustrates a reading process when two types of light-emitting elements are unevenly arranged in each light source unit. In this example, the two types of light-emitting elements are light-emitting element A, which emits visible light, and light-emitting element B, which emits invisible light. The first light source unit 1311 is equipped with only light-emitting element A, and the second light source unit 1312 is equipped with only light-emitting element B. FIG. 6(a) is a schematic diagram of the object to be read, such as a document 22, and the optical path of visible light when the leading edge of the object to be read passes the reading position in the background unit 26. FIG. 6(b) illustrates a read image of the object to be read obtained by a visible light sensor. In this configuration, the light-emitting element A, which emits visible light, is mounted only in the first light source unit 1311. This creates a problem in that visible light is blocked in an area (a shadow of visible light) at the downstream end of the object to be read in the conveyance direction, as shown in FIGS. 6(a) and 6(b). In contrast to the above, when reading using an invisible light sensor, there is a problem in that a portion where the invisible light is blocked (a shadow of the invisible light) occurs at the upstream end of the reading target in the conveyance direction.

[0029] FIG. 7 is a diagram showing a reading process when two types of light-emitting elements are alternately arranged in an array in each light source unit. As in the example of FIG. 6, the two types of light-emitting elements are light-emitting element A that emits visible light and light-emitting element B that emits invisible light, but the light-emitting elements A and B are alternately arranged in an array in both the first light source unit 1311 and the second light source unit 1312. In this configuration, since the light-emitting element A that emits visible light is mounted in the first light source unit 1311 and the second light source unit 1312, no visible light shadow is cast on the downstream end of the reading target in the conveying direction, as shown in FIGS. 7(a) and 7(b). Similarly, since the light-emitting element B that emits invisible light is mounted in the first light source unit 1311 and the second light source unit 1312, no invisible light shadow is cast on the upstream end of the reading target in the conveying direction.

[0030] In this way, by arranging two types of light-emitting elements that emit light of different wavelengths alternately in an array in each light source unit, light of one wavelength is not emitted unevenly from only one light source unit, and the occurrence of areas where light of one wavelength is blocked (shadows of light of one wavelength) can be suppressed.

[0031] Next, an example of realizing the lighting device 13 using a common light source unit for the first light source unit 1301 and the second light source unit 1302 will be described. FIG. 8 is a diagram showing an example of a common light source unit and the lighting device 13. As shown in FIG. 8, the light source unit 1300 has a light source section 1310 in which light-emitting elements A and light-emitting elements B are alternately arranged in an array. Furthermore, the first light source unit 1301 and the second light source unit 1302 constituting the lighting device 13 both have the light source unit 1300, which is a common light source unit. Here, the arrangement of the light source unit 1300 in the second light source unit 1302 is rotated 180 degrees from the arrangement of the light source unit 1300 in the first light source unit 1301.

[0032] In other words, in this embodiment, the illumination device 13 is realized using a common light source section. That is, in the illumination device 13 shown in Fig. 8, a common light source section, that is, a light source section 1310, is used for the first light source section 1311 included in the first light source unit 1301 and the second light source section 1312 included in the second light source unit 1302. Here, the arrangement of the light source sections 1310 in the second light source section 1312 is rotated 180 degrees from the arrangement of the light source sections 1310 in the first light source section 1311.

[0033] In this way, the above conditions (1) and (2) can be achieved by using a common light source unit (or light source section). As a result, the first light source unit 1301 (or first light source section 1311) and the second light source unit 1302 (or second light source section 1312) can be configured using the same parts, which eliminates the need to manufacture different parts and reduces management costs and parts costs.

[0034] FIG. 9 is a diagram showing another example of the configuration of the illumination device 13 according to this embodiment. In the illumination device 13 of this embodiment, as shown in FIG. 9, one of the two types of light-emitting elements can be a white light source and the other a near-infrared light source. In this example, in the arrangement of FIG. 3(b), a white light source is provided as light-emitting element A and a near-infrared light source is provided as light-emitting element B, and the effects shown in FIG. 3(b) are achieved. Therefore, with the configuration as shown in FIG. 9, it is possible to provide an illumination device 13 that can irradiate white light and near-infrared light with little reduction in illuminance distribution at the edges, good flatness of illuminance distribution, and good irradiation efficiency in the irradiated area.

[0035] As described above, in this embodiment, by providing two light source units and configuring them to satisfy the above-mentioned conditions (1) and (2), it is possible to efficiently irradiate light of different wavelengths onto the object to be read without performing complex processing on the light guide.

[0036] (Second embodiment) In the second embodiment, the first light source unit 1311 and the second light source unit 1312 are configured to have only either the light-emitting element A or the light-emitting element B. In the following description of the second embodiment, the description of the parts that overlap with the first embodiment will be omitted, and only the parts that differ from the first embodiment will be described.

[0037] Fig. 10 is a diagram showing an example of the configuration of an illumination device 13 according to this embodiment. The illumination device 13 shown in Fig. 10 is configured such that each light source section is equipped with only one of light-emitting elements A and light-emitting element B. Note that Fig. 10 shows an example in which point light-source-like light-emitting elements are arranged in an array in each light source section, but as will be described later, it is also possible to configure the illumination device 13 so that the light-emitting surface of a light guide is arranged at the position of each light-emitting element, and light guided from the end of the light guide is irradiated from the light-emitting surface.

[0038] 11 is a diagram illustrating the arrangement of light sources in this embodiment. Each diagram shows the first light source unit 1311 and the second light source unit 1312 as viewed from the illuminated region 221. The dotted line between the light source units in each diagram indicates the center line of the illuminated region 221 in the main scanning direction, and the foot of a perpendicular line 222 extending from each main scanning position is located on this dotted line. Furthermore, the wavelength of light emitted from the light source indicated by light spots is different from the wavelength of light emitted from the light source indicated by dark spots.

[0039] 11(a), irradiation positions 1-1, 1-2, . . . , 1-n (n is a natural number) indicate positions where light is emitted from the first light source unit 1311, and irradiation positions 2-1, 2-2, . . . , 2-n indicate positions where light is emitted from the second light source unit 1312. Furthermore, irradiation position 1-m (m=1, 2, . . . , n) and irradiation position 2-m are opposite positions across the perpendicular line 222. In this example, a light-emitting element may be mounted at each irradiation position, or a light-emitting element may be mounted at a position away from each light source unit, and light may be emitted from each irradiation position using a light guide or the like.

[0040] 11(b) shows an example in which light-emitting element A or B is disposed at each irradiation position in FIG. 11(a), and is similar to the first light source unit 1311 and second light source unit 1312 shown in FIG. 10. With this configuration, a light guide is not required, and adjustment of the light guide position of the light guide is also not required. Therefore, the effects of this embodiment can be achieved without increasing the processing cost of the light guide or the number of mounting steps. In both FIGS. 11(a) and 11(b), the light source units are disposed so that the optical axes of light irradiated from opposing positions across the perpendicular line 222 intersect in the irradiated region 221.

[0041] FIG. 12 is a diagram illustrating the effects of the configuration of this embodiment. FIG. 12(a) shows an example in which the pitch interval between light-emitting elements is wide in the second light source unit 1312 of FIG. 3(b). For example, if the light-emitting intensity of light-emitting element B in the second light source unit 1312 is weak and the amount of current to light-emitting element B cannot be increased, it is possible to increase the light-emitting intensity by narrowing the pitch interval between light-emitting elements B and mounting them densely. Therefore, if the same light source unit (second light source unit 1312) includes light-emitting elements A and B and light-emitting elements B are mounted densely as shown in FIG. 12(a), the illuminance distribution of light-emitting element B will be as shown in graph (bB) in FIG. 12(b). Here, the solid line indicates the illuminance distribution of light-emitting element B, and the dashed line indicates the contribution of each light-emitting element B to this distribution. As such, even if light-emitting elements A and B are mounted densely while light-emitting elements B are mixed, the pitch interval between light-emitting elements B will not be uniform, and the illuminance will have a valley at the position indicated by the arrow. Therefore, the flatness of the illuminance distribution of light-emitting element B cannot be ensured.

[0042] On the other hand, if the same light source unit has only one type of light-emitting element as in Figure 11, even if the light-emitting elements are densely mounted as needed, the pitch intervals of the light-emitting elements B can be made equal as in Figure 12(c), thereby solving the problem of flatness of the illuminance distribution. In graph (cB) in Figure 12(c), the solid line shows the illuminance distribution of the light-emitting element B, and the dashed line shows the contribution of each light-emitting element B to this. In this way, the arrangement in Figure 11 makes it possible to adjust the pitch intervals of the light-emitting elements according to the light-emitting intensity while avoiding the problem of not being able to ensure flatness of the illuminance distribution, thereby enabling an increase in illuminance and an improvement in the illuminance distribution in the irradiated area 221.

[0043] Note that, when the light-emitting intensity of light-emitting element B is weak and the light-emitting intensity of light-emitting element A is sufficient, the arrangement shown in Fig. 11 may be realized by densely mounting light-emitting elements B, but not densely mounting light-emitting elements A. For example, a light-emitting surface of a light guide may be disposed at the position of light-emitting element A, and one light-emitting element A may irradiate light from the light-emitting surfaces of multiple light guides. In this way, an optimal number of light-emitting elements that do not need to be densely mounted can be mounted, thereby preventing increases in costs.

[0044] In addition, in the configuration of Figure 11, the type of light emitting element mounted on one light source unit can be limited to one type, so it is possible to adopt a light guide that matches the optical characteristics of each light emitting element. In this way, by adopting a light guide that matches the characteristics of each type of light emitting element, it is possible to further improve the irradiation efficiency and illuminance distribution.

[0045] 13 is a diagram illustrating the effect of reading in the image reading device 30 according to this embodiment. The illumination device 13 used in the image reading device 30 includes a white light source as a light-emitting element A of a first light source unit 1311, and includes a light-emitting element other than a white light source (for example, a near-infrared light source) as a light-emitting element B of a second light source unit 1312. The first light source unit 1311 is disposed upstream in the conveying direction of a sheet-through document (document) by the ADF 20.

[0046] Fig. 13(a) is a schematic diagram of the original and the optical path of the white light when the leading edge of the original approaches the reading position. Of the light source units, the first light source unit 1311, which is equipped with only a white light source, is located upstream in the transport direction, and as shown in Fig. 13(a), part of the white light is blocked by the original at the leading edge of the original, causing a shadow to appear downstream in the transport direction from the reading position. For this reason, in the image read using this configuration, a shadow is likely to appear at the leading edge of the original, as shown in Fig. 13(b).

[0047] Meanwhile, in the technical field aimed at detecting skew in a scanned image of a document, a method is known in which the leading edge of the document is detected by a shadow that appears at the leading edge of the document in order to distinguish the document from the background. In the example of Fig. 13, a shadow is likely to appear at the leading edge of the document, so by configuring this embodiment as shown in Fig. 13(a), the leading edge of the document is detected by using the shadow of the leading edge of the document as shown in Fig. 13(b), thereby improving the accuracy of skew detection.

[0048] 14 is a diagram illustrating another effect of reading in the image reading device 30 according to this embodiment. The illumination device 13 used in the image reading device 30 is arranged so that the first light source unit 1311 includes a light emitting element other than a white light source (for example, a near-infrared light source) as the light emitting element A, and the second light source unit 1312 includes a white light source as the light emitting element B. The first light source unit 1311 is arranged downstream in the conveying direction of the sheet-through document by the ADF 20.

[0049] FIG. 14(a) shows a schematic diagram of the document and the optical path of the white light when the leading edge of the document approaches the reading position. Of the light source units, the second light source unit 1312, which is equipped with only a white light source, is located downstream in the transport direction. As shown in FIG. 14(a), the white light is not partially blocked by the document at the leading edge of the document, so no shadow is generated at the reading position. Therefore, in the image read using this configuration, no shadow is present even at the leading edge of the document, as shown in FIG. 14(b). Therefore, by configuring this embodiment as shown in FIG. 14(a), it is possible to read an image without a shadow at the leading edge of the document, as shown in FIG. 14(b).

[0050] As described above, in this embodiment, by providing two light source units and configuring the light guide to satisfy the above-mentioned conditions (1) and (2), it is possible to efficiently irradiate light of different wavelengths onto the reading target without performing complex processing on the light guide. Furthermore, in this embodiment, it is possible to improve the illuminance in the irradiated area 221 by adjusting the pitch interval of the light emitting elements according to the light emission intensity while ensuring the flatness of the illuminance distribution.

[0051] (Third embodiment) In the third embodiment, a first light source unit 1311 and a second light source unit 1312 are configured to have light-emitting elements A and B, which are surface light sources. In the following description of the third embodiment, the description of parts that overlap with the first embodiment will be omitted, and only parts that differ from the first embodiment will be described.

[0052] Fig. 15 is a diagram showing an example of the configuration of the lighting device 13 according to this embodiment. As shown in Fig. 15, this embodiment uses a surface light source such as an organic EL (Electro Luminescence) as the light emitting element mounted in each light source unit.

[0053] FIG. 16 is a diagram illustrating the effects of the configuration of this embodiment. FIG. 16(a) shows the illuminance distribution (illuminance at each main scanning position) in the illuminated region 221 when point light sources are used as the light-emitting elements A and B as in FIG. 11 and the pitch interval between the light-emitting elements is inappropriate. The illuminance of each light-emitting element peaks at a position corresponding to the main optical axis of the light-emitting element, as indicated by the dotted line in graph (aA) and the dashed line in graph (aB), and decreases with increasing distance from that position. Therefore, the illuminance distribution of the light irradiated from the first light source unit 1311 and the second light source unit 1312 is as indicated by the solid line in graph (aA) and graph (aB), respectively. Therefore, an example such as that shown in FIG. 16(a) has the problem that the flatness of the illuminance distribution cannot be ensured.

[0054] On the other hand, when a surface light source is used as the light-emitting element as shown in Fig. 15, the illuminance distribution in the illuminated region 221 is ensured to be flat, as shown in Fig. 16(b). Here, graph (bA) shows the illuminance distribution of light irradiated from the first light source unit 1311, and graph (bB) shows the illuminance distribution of light irradiated from the second light source unit 1312. When a surface light source is used as shown in Fig. 15, the inappropriate pitch interval that was the cause of the problem in Fig. 16(a) does not occur. Therefore, with the configuration of Fig. 15, flatness is ensured, as shown in Fig. 16(b).

[0055] As described above, in this embodiment, by providing two light source units and configuring the light guide to satisfy the above-mentioned conditions (1) and (2), it is possible to efficiently irradiate light of different wavelengths onto the reading target without performing complex processing on the light guide. Furthermore, when a point light source is used, multiple light-emitting elements are arranged in an array, which increases the number of mounted parts, whereas with the configuration of this embodiment, only one light-emitting element is required for each light source unit, which reduces the number of mounted parts and makes it possible to reduce the number of mounting steps.

[0056] (Fourth embodiment) In the fourth embodiment, an image forming apparatus is provided with an image reading device 30 using the illumination device 13 according to the first embodiment. In the following description of the fourth embodiment, explanations of parts that overlap with the first embodiment will be omitted, and only parts that differ from the first embodiment will be described.

[0057] 17 is a schematic cross-sectional view showing an example of the configuration of the mechanism of an image forming apparatus 100 according to this embodiment. The image forming apparatus 100 (for example, a digital copier) is basically composed of an image reading device 30, a paper feed unit 103, and an image forming apparatus main body 104. The image reading device 30 also includes a reading unit 10 and an ADF 20, and has the same configuration as in the first embodiment.

[0058] The image forming device main body 104 includes a tandem imaging unit 105, a registration roller 108 that supplies recording paper from the paper feed unit 103 to the imaging unit 105 via a conveying path 107, an optical writing device 109, a fixing and conveying unit 110, and a double-sided tray 111.

[0059] The image forming unit 105 has four photosensitive drums 112 arranged in parallel corresponding to the four colors YMCK, and image forming elements including a charger, a developing unit 106, a transfer unit, a cleaner, and a static eliminator are arranged around each photosensitive drum 112. In addition, an intermediate transfer belt 113 is arranged between the transfer unit and the photosensitive drum 112, and is stretched between a drive roller and a driven roller while being sandwiched in the nip between them.

[0060] In the tandem image forming apparatus 100 configured in this manner, optical writing is performed for each of the YMCK colors onto the photosensitive drums 112 corresponding to each color, the toner for each color is developed in the developing device 106, and the image is primarily transferred onto the intermediate transfer belt 113 in the order of Y, M, C, and K, for example. Then, the full-color image in which the four colors are superimposed by the primary transfer is secondarily transferred onto the recording paper, which is then fixed and discharged, forming the full-color image on the recording paper.

[0061] As described above, the image forming apparatus 100 of this embodiment includes the image reading device 30 described in the first embodiment, and therefore can efficiently irradiate light of different wavelengths onto the reading target without performing complex processing on the light guide by using the image reading device 30. Specifically, it is possible to provide an image forming apparatus 100 that includes an image reading device 30 that can read an image using white light and near-infrared light, has no reduction in illuminance distribution at the edges, has a good flatness of illuminance distribution, and has good irradiation efficiency in the irradiated area.

[0062] (Fifth embodiment) In the fifth embodiment, the illumination device 13 according to the first embodiment is used in an inspection device. In the following description of the fifth embodiment, the description of the parts that overlap with the first embodiment will be omitted, and only the parts that differ from the first embodiment will be described.

[0063] FIG. 18 is a diagram showing an example of the configuration of the illumination device 13 included in the inspection device according to this embodiment. The differences from the first embodiment are that the illumination device 13 illuminates an inspection target (e.g., food) transported by a conveyor belt or other conveying device 40 disposed below the illumination device 13, and that inspection is performed using light reflected from the inspection target at a sensing position. Here, the sensing position refers to the position where the inspection device according to this embodiment reads the light reflected from the inspection target. Note that FIG. 18 is a view of each light source unit and the conveying device 40 viewed obliquely from above, showing the surface behind the surface on which each light source unit is mounted, and the conveying path on the top surface of the conveying device 40. Furthermore, the illuminated surface 220 and the illuminated area 221 are located on the top surface of the conveying device 40.

[0064] In food manufacturing factories, food products transported on a conveyer belt or the like are sometimes inspected before shipping to check for foreign matter, defects, etc., using not only visible light but also invisible light. In this manner, the illumination device 13 according to this embodiment can be applied to inspection processes in which inspections are performed using a plurality of wavelengths.

[0065] 18, in this embodiment, the upper surface of the transport device 40 is the irradiated surface 220, and the sensing position of the inspection object is the irradiated area 221. That is, the first light source unit 1311 and the second light source unit 1312 of the illumination device 13 are arranged so that the irradiated area 221 onto which each light source unit irradiates light becomes the sensing position of the inspection object. In addition, the arrangement of each light source unit and the arrangement of the light-emitting elements in each light source unit are configured to satisfy the conditions etc. described in the first embodiment.

[0066] As described above, according to this embodiment, the illumination device 13 can be applied to the inspection of food and the like conveyed by the conveying device 40, and the efficiency of illumination of the inspection object can be improved without complex processing of the light guide. Specifically, it is possible to provide an inspection device equipped with the illumination device 13 that is capable of inspection using, for example, white light and near-infrared light, has no reduction in illuminance distribution at the edges, has a good flatness of illuminance distribution, and has good illumination efficiency in the irradiated area.

[0067] Although various embodiments of the present invention have been described above, the above-described embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These novel embodiments and modifications thereof are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, components from different embodiments and modifications may be combined as appropriate.

[0068] For example, aspects of the present invention are as follows. <1> a first light source unit that irradiates light onto an irradiated area; a second light source unit disposed opposite the first light source unit and irradiating the irradiated region with light; Equipped with the irradiated region has a region where light emitted from the first light source unit in the direction of the main optical axis and light emitted from the second light source unit in the direction of the main optical axis overlap, The lighting device is characterized in that the light emitted to the region by the first light source unit and the second light source unit has different wavelengths. <2> a first light-emitting element of the first light source unit and a second light-emitting element of the second light source unit that is adjacent to the first light-emitting element are disposed at positions that face each other across a perpendicular line of a plane that is parallel to the irradiated surface of the irradiated region; <1> 1 is a lighting device according to the first embodiment. <3> two types of light emitting elements emitting light of different wavelengths are alternately arranged in an array in the first light source unit; The two types of light emitting elements are alternately arranged in an array in the second light source unit. <1> or <2> 1 is a lighting device according to the first embodiment. <4> a common light source unit is used for the first light source unit and the second light source unit, The arrangement of the common light source units in the second light source unit is obtained by rotating the arrangement of the common light source units in the first light source unit by 180 degrees. <3> 1 is a lighting device according to the first embodiment. <5> the first light source unit has only one of two types of light-emitting elements that emit light of different wavelengths, the second light source unit has only the other of the two types of light-emitting elements; <1> or <2> 1 is a lighting device according to the first embodiment. <6> The light emitting element is a surface light source. <5> 1 is a lighting device according to the first embodiment. <7> The light emitted from the first light source unit and the second light source unit from positions facing each other across a perpendicular line to a plane parallel to the irradiated surface of the irradiated region is light emitted from a white light source, and the other is light emitted from a near-infrared light source. <1> ~ <6> 10. The lighting device according to claim 9, wherein: <8> The aforementioned <1> ~ <7> and a lighting device according to any one of the above items. and a sensor that reads light that is irradiated onto the illuminated area by the first light source unit and the second light source unit of the illumination device and reflected from the illuminated area. <9> The aforementioned <5> an illumination device according to a sensor that reads light that is irradiated onto the illuminated area by the first light source unit and the second light source unit of the lighting device and reflected from the illuminated area; Equipped with one of the first light source unit and the second light source unit is disposed upstream in a conveying direction of a sheet-through document; The image reading device has a light emitting element of the light source unit arranged on the upstream side that is a white light source. <10> The aforementioned <5> an illumination device according to a sensor that reads light that is irradiated onto the illuminated area by the first light source unit and the second light source unit of the lighting device and reflected from the illuminated area; Equipped with one of the first light source unit and the second light source unit is disposed downstream in a conveying direction of a sheet-through document; The light source unit disposed downstream has a light emitting element that is a white light source, and is an image reading device. <11> The aforementioned <8> An image forming apparatus is provided with the image reading device described above. <12> The aforementioned <1> ~ <7> and a lighting device according to any one of the above items. a transport device that transports the inspection object; Equipped with The first light source unit and the second light source unit of the illumination device are an inspection device that are arranged so that the illuminated region is a sensing position for the inspection object transported by the transport device. <13> a first light source unit that irradiates light onto an irradiated area; a second light source unit disposed opposite the first light source unit and irradiating the irradiated region with light; A lighting method for a lighting device comprising: the irradiated region has a region where light emitted from the first light source unit in the direction of the main optical axis and light emitted from the second light source unit in the direction of the main optical axis overlap, The illumination method is characterized in that the light emitted to the region by the first light source unit and the second light source unit has different wavelengths. [Explanation of symbols]

[0069] 10 Reading unit 13 Lighting equipment 17 Sensor Board 20 Automatic Document Feeder (ADF) 22 Manuscript 30 Image reader 40 Conveyor 100 Image forming device 220 Irradiated surface 221 Irradiated area 222 Perpendicular 1301 First light source unit 1302 Second light source unit 1311 1st light source section 1312 Second light source section [Prior art documents] [Patent documents]

[0070] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-081074

Claims

1. a first light source unit that irradiates light onto an illuminated region; a second light source unit disposed opposite the first light source unit and configured to irradiate the irradiated region with light; Equipped with the irradiated region has a region where light emitted from the first light source unit in the direction of the main optical axis and light emitted from the second light source unit in the direction of the main optical axis overlap, The lighting device according to claim 1, wherein the first light source unit and the second light source unit irradiate the region with light having different wavelengths.

2. 2. The lighting device according to claim 1, wherein a first light-emitting element of the first light source unit and a second light-emitting element of the second light source unit that is adjacent to the first light-emitting element are arranged in opposing positions across a perpendicular line to a plane parallel to the irradiated surface of the irradiated region.

3. two types of light emitting elements emitting light of different wavelengths are alternately arranged in an array in the first light source unit; The lighting device according to claim 1 , wherein the two types of light-emitting elements are alternately arranged in an array in the second light source section.

4. a common light source unit is used for the first light source unit and the second light source unit, The lighting device according to claim 3 , wherein the arrangement of the common light source units in the second light source unit is rotated by 180 degrees from the arrangement of the common light source units in the first light source unit.

5. the first light source unit has only one of two types of light-emitting elements that emit light of different wavelengths, The lighting device according to claim 1 , wherein the second light source unit has only the other of the two types of light-emitting elements.

6. 6. The lighting device according to claim 5, wherein the light emitting element is a surface light source.

7. 2. The lighting device according to claim 1, wherein the light emitted from the first light source unit and the second light source unit from positions facing each other across a perpendicular line to a plane parallel to the irradiated surface of the irradiated region is light emitted from a white light source, and the other is light emitted from a near-infrared light source.

8. A lighting device according to any one of claims 1 to 7; an image reading device comprising: a sensor that reads light that is irradiated onto the illuminated area by the first light source unit and the second light source unit of the illumination device and reflected from the illuminated area;

9. The lighting device according to claim 5 ; a sensor that reads light that is irradiated onto the illuminated area by the first light source unit and the second light source unit of the lighting device and reflected from the illuminated area; Equipped with one of the first light source unit and the second light source unit is disposed upstream in a conveying direction of a sheet-through document; The image reading device, wherein the light source unit disposed on the upstream side has a light emitting element that is a white light source.

10. The lighting device according to claim 5 ; a sensor that reads light that is irradiated onto the illuminated area by the first light source unit and the second light source unit of the lighting device and reflected from the illuminated area; Equipped with one of the first light source unit and the second light source unit is disposed downstream in a conveying direction of a sheet-through document; The light source unit disposed downstream has a light emitting element that is a white light source.

11. An image forming apparatus comprising the image reading device according to claim 8.

12. A lighting device according to any one of claims 1 to 7; a transport device that transports the inspection object; Equipped with An inspection apparatus in which the first light source unit and the second light source unit of the illumination device are arranged so that the illuminated area is a sensing position of the inspection object transported by the transport device.

13. a first light source unit that irradiates light onto an illuminated region; a second light source unit disposed opposite the first light source unit and configured to irradiate the irradiated region with light; A lighting method for a lighting device comprising: the irradiated region has a region where light emitted from the first light source unit in the direction of the main optical axis and light emitted from the second light source unit in the direction of the main optical axis overlap, An illumination method, characterized in that the light emitted from the first light source unit and the second light source unit onto the region has different wavelengths.

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