JP5546905B2 - Light source unit and image reading apparatus using the same - Google Patents

Description

  The present invention relates to a light source unit in an image reading apparatus such as a scanner device, a copying machine, or a facsimile, and relates to an improvement of a light source mechanism that irradiates a reading surface.

  In general, a light source unit in an image reading apparatus such as a scanner device or a copying machine irradiates light from a light source to a reading platen as disclosed in, for example, Patent Document 1 and collects reflected light by a photoelectric conversion sensor. It is widely known as a device for photoelectric conversion.

  As this light source unit, a light source lamp is disposed on a scanning carriage that moves along a platen as disclosed in Patent Document 2, and reflected light of light emitted from the light source lamp is converted into a photoelectric conversion sensor by a condenser lens. An image is formed. The photoelectric conversion sensor is composed of a line sensor, and the image on the platen is read in line order while moving the scanning carriage in the sub-scanning direction.

  In the image reading apparatus having such a configuration, the light source unit is required to emit uniform light in the main scanning direction (line sensor arrangement direction). For this reason, conventionally, a rod-like light emitter such as a fluorescent lamp (cold cathode tube) or an LED array is used as a light source lamp, or a rod light source that diffuses a point light source along a reading line and emits it from a predetermined angle is used. .

  For example, in Patent Document 3, as shown in FIG. 14A, a light source unit in which a rod-shaped light guide body in which a light scattering surface and a light emission surface are arranged opposite to each other in the longitudinal direction is provided, and a light source is arranged on an end surface of the light guide body. Has been proposed. A light source mechanism is known in which light incident from a light source is scattered between a light scattering surface and a light emitting surface, guided in the longitudinal direction, and irradiated with light rays within a predetermined critical angle to the outside from the light emitting surface. .

JP 2007-074019 A JP 2005-234297 A JP 2000-048616 A

  As described above, a light source unit structure in which a light guide is provided along a reading line and light is introduced from a light emitting body such as an LED when the image reading surface is irradiated with uniform linear light is disclosed in the above patent. It is known from Document 3 and the like. In this case, conventionally, light from one light emitter enters the light guide from the end face of the light guide, or light enters a light guide from a plurality of light emitters having different wavelengths.

  The light guide is configured to irradiate with a uniform amount of light indicated by a dotted line in FIG. 14B as a linear light beam along the reading line of the reading surface, and the reflected light from the reading surface is collected by a condensing lens. The image is formed on the line sensor. In this case, the condenser lens is composed of one or a plurality of lens units (convex lens configuration). At this time, the light that has passed through the lens unit due to the characteristics of the condensing lens has a light amount of light that has passed through the periphery of the lens, as shown by a solid line in FIG. It is known to decay.

  This is generally known as the cosine fourth law (the illuminance after incidence is proportional to the cosine fourth power when the incident angle incident on the lens is θ). For this reason, even if the linear light that irradiates the reading surface is evenly configured in the main scanning direction, the amount of light that is photoelectrically converted by the line sensor is the sensor output value for light that has passed through the center of the lens and light that has passed through its periphery. It will be different. This state is shown in FIG. 14B, where the sensor output value is high at the center of the lens and low at the periphery.

  In order to solve such a problem of lens characteristics, conventionally, as shown in FIG. 15B, the amount of light emitted from the light guide to the reading surface is set so that both ends of the reading line are high and the center is low. For example, the scattering surface is devised. When using a light guide like the above-mentioned Patent Document 3, for example, as shown in FIG. 15A, first, the scattering surface is inclined as shown in order to increase the amount of light at the light guide central part, The amount of light at both ends can be increased by adjusting the pitch width of the reflection surface protrusions formed on the scattering surface and reducing the pitch width P1 at both ends compared to the pitch width P2 at the central portion of the light guide to increase the reflected light. Has been done.

  In this way, when the light amount is adjusted by the shape of the scattering surface of the light guide, there are problems such as shrinkage spots at the time of molding due to the shape (thickness etc.) of the scattering surface and changes in diameter of the light guide. Usually, the light guide is made of a highly transparent resin material (for example, a thermoplastic resin such as an acrylic resin or a polycarbonate resin), and may be deformed by heat or deterioration with time.

  Therefore, the present inventor pays attention to a light source that introduces light into the end face of the light guide, and the light source is configured by a plurality of chip-shaped light emitters, and a plurality of lights are incident on the light guide from different height positions. This led to the idea that the amount of linear light can be made large at both ends and small at the center.

The present invention provides a light source unit that can emit light with a light amount suitable for the characteristics of a reading optical system when irradiating a reading surface with linear light, has a simple structure, and can be manufactured at low cost. That is the issue.
It is another object of the present invention to provide a light source unit that is free from unevenness of light when light is introduced from a plurality of light emitters into a light guide that generates linear light, and at the same time is suitable for light amount characteristics.

  To achieve the above object, the present invention provides a light guide having a light scattering surface that scatters light in a line direction along a reading surface, and a light emitting surface that emits light from the light scattering surface toward the reading surface. A light source disposed on at least one end surface of the light guide. Therefore, this light source is composed of at least two light emitters, and the first and second light emitters are incident on the light guide from different positions and spaced apart from each other in the direction of the outgoing light path from the light exit surface. It is characterized by being arranged in. With such a configuration, the light emitters arranged vertically in the emission direction have the light from the light emitter (first light emitter) located close to the scattering surface concentrated on both ends of the linear light to increase the amount of light. Will be allowed to.

  Further, the configuration will be described in detail. The light source unit scatters and reflects light from the light source (9) to irradiate the reading surface (R) with linear light, and scatters the light in the line direction along the reading surface. And a light guide (30) having a light scattering surface (32) for emitting light from the light scattering surface toward the reading surface, and at least one end surface (31R) of the light guide. And a light source (9) arranged at the same time. The light source is composed of at least two light emitters (41, 42), and the first light emitter (41) and the second light emitter (42) enter the light guide from different positions. At the same time, they are arranged at a distance in the direction of the outgoing light path (hx) from the light exit surface to the reading surface.

  In this case, the first light emitter and the second light emitter are composed of light emitting elements having substantially the same wavelength, such as a white LED (Light Emitting Diode). The first and second light emitters are not limited to one light emitting element, but are composed of a plurality of light emitting elements. In this case, for example, the plurality of light emitting elements constituting the second light emitter are arranged symmetrically about the outgoing light path (normal line of the light scattering surface). By configuring in this way, it becomes possible to reduce the amount of unevenness of the linear light.

  Moreover, the light source arrange | positioned at the end surface of a light guide is arrange | positioned at the both end surfaces of a light guide, or arrange | positions in the one. When arrange | positioning at both end surfaces, arrange | position so that right and left may become a symmetry completely. Moreover, when arrange | positioning to one end surface, a reflective member is provided in an other end surface, and a virtual light source is formed.

  In the present invention, the light source disposed on the end face of the light guide is composed of at least two light emitters, and the first and second light emitters are incident on the light guide from different positions and are emitted from the light exit surface. Since they are arranged at a distance in the vertical direction of the light emission path, the following effects can be obtained.

  According to the present invention, a light guide disposed in a line direction along a reading surface is such that light from a light emitter at a distance close to the scattering surface in the direction of the outgoing light path (normal direction of the scattering surface) is linear light. Light is reflected relatively densely at both ends, and light from the light emitter at a distance far from the scattering surface reflects light relatively densely at the center of the linear light, and both ends have a large amount of light.

  As described above, the light irradiated from the exit surface of the light guide to the reading surface has a large amount of light at both ends in the reading line direction and a small amount of light at the central portion, and has a light amount characteristic. Accordingly, by setting the incident positions of the first and second plurality of light emitters to the optimum values, it is possible to irradiate the reading surface with the light amount characteristic suitable for the characteristic (mainly the lens characteristic or the sensor characteristic) of the reading optical system. It becomes possible.

  Further, the present invention adjusts the amount of light by setting the relative position of the light emitters arranged on the end face of the light guide, so that it is optimal for the device specifications such as resolution, reading line width, scanning speed, etc. High usage characteristics can be set easily. Compared with the case where the conventional light guide structure is individually adapted to the device specifications (light guide production), this feature only needs to be adjusted (substrate production) when mounting the light emitting element on the substrate, for example. It is possible to easily produce small quantities of other varieties at low cost.

  Furthermore, the present invention improves the optical performance of the initial characteristics by replacing the substrate on which the light emitting body is mounted without replacing the light guide which is relatively expensive in the case where problems such as light intensity unevenness and deterioration in light intensity occur in the process of use. It can be repaired.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 2 is an explanatory diagram illustrating a configuration of a reading carriage that reads a document image in the apparatus of FIG. 1. FIG. 2 is an external perspective view of a carriage in the apparatus of FIG. 1. FIG. 4 is a partially exploded perspective view of the carriage shown in FIG. 3. Explanatory drawing explaining the arrangement | positioning relationship between the light source of a light source unit in this invention, and a light guide. (A) thru | or (f) The layout which demonstrates the light source arrangement | positioning state in the carriage shown in FIG. The graph which shows the light emission characteristic in the light source arrangement | positioning of FIG. (A) thru | or (c) The schematic diagram which shows the light quantity characteristic in the light source arrangement | positioning of FIG. (A) thru | or (c) The schematic diagram which shows the light quantity characteristic in the light source arrangement | positioning of FIG. FIG. 3 is an explanatory plan view illustrating a configuration of a carriage. The block diagram of the light source unit in the apparatus of FIG. Explanatory drawing explaining the arrangement | positioning relationship of the light source and light guide of a light source unit in 6th Embodiment. The schematic diagram which shows the light quantity characteristic of the light source unit of FIG. (A) The conventional general light source unit block diagram, (b) The characteristic figure explaining the relationship between the optical reduction type light source characteristic and the light reception characteristic. (A) The light source unit block diagram corresponding to the conventional general light quantity adjustment is shown, (b) The characteristic diagram explaining the relationship between the optical reduction type light source characteristic and the light receiving characteristic.

  FIG. 1 shows a configuration of an image reading apparatus A incorporating a light source unit 9 according to the present invention. The apparatus shown in FIG. 1 includes an image reading apparatus A and a document feeding unit B mounted thereon. Hereinafter, the image reading apparatus A and the light source unit 9 incorporated therein will be described in this order.

[Image reading device]
An image reading apparatus A according to the present invention includes a first platen 3 and a second platen 2 in an apparatus housing 1 as shown in FIG. The first and second platens 3 and 2 are formed of a transparent material such as glass and are fixed to the top of the apparatus housing 1. The first platen 3 is formed to have a size size for placing and setting the document, and the second platen 2 is formed to have a width size so as to read the document moving at a predetermined speed. The first and second platens 3 and 2 are arranged side by side as shown in FIG. An image reading mechanism is built in the apparatus housing 1.

  An example of the image reading mechanism will be described with reference to FIG. 2 (enlarged view of the main part of FIG. 1). A carriage 6 is disposed in the apparatus housing 1 so as to be movable between the first platen 3 and the second platen 2. At the same time, the carriage 6 is supported by a guide rail 12 described later so as to reciprocate along the first platen 3.

  The carriage 6 has a light source unit 9 (first light source unit 9a and second light source unit 9b described later) and a reflection mirror 10 (first mirror) for deflecting reflected light from a document on a unit frame 11 made of heat-resistant resin. 10a, the second mirror 10b, the third mirror 10c), the condensing lens 7 that condenses the light from the reflecting mirror 10, and the line sensor 8 that is disposed in the image forming section formed by the condensing lens 7. Is installed. The image data output as an electrical signal from the line sensor 8 is electrically connected to an image processing unit (data processing board; not shown) by a data transfer cable so as to transfer the image data to the image processing unit.

[Carriage configuration]
The carriage 6 is supported by a guide rail 12 disposed in the apparatus frame so as to reciprocate along the guide rail 12. The carriage 6 is connected to a carriage motor (not shown) via a winding member such as a wire, and reciprocates in the left-right direction in FIG. The pair of left and right guide rails 12 are arranged in parallel with the first platen 3 and are configured to reciprocate the carriage 6 stably.

  As shown in FIG. 2, the first platen 3 and the second platen 2 are arranged on substantially the same plane, and the carriage 6 positioned below the first platen 3 and the second platen 2 is a guide rail that can be moved to a position directly below the first and second platens 3 and 2. 12 is selectively moved by a carriage motor. In the process of moving along the first platen 3, the carriage 6 scans the document set on the first platen 3 and reads an image with the line sensor 8. At the same time, the carriage 6 is configured to move from the first platen 3 directly below the second platen 2 and to read an image of a document moving at a predetermined speed on the second platen while being stationary at this position. .

  The carriage 6 is equipped with a light source unit 9 (to be described later) and a reflection mirror (plate glass, prism, etc.) 10 for deflecting reflected light of light emitted from the light source unit 9 in a predetermined reading optical path direction. The apparatus shown in FIG. 2 deflects reflected light from the reading surface R (first platen R1, second platen R2) by the first mirror 10a, and deflects the light by the second mirror 10b and the third mirror 10c. Show. The light from the third mirror 10 c is imaged on the line sensor 8 by the condenser lens 7.

  The condenser lens 7 is composed of one or a plurality of lenses, and forms a convex lens as a whole. The line sensor 8 is composed of a photoelectric conversion element such as a CCD, and the illustrated one is composed of an RGB color sensor array. Although the condenser lens 7 and the line sensor 8 are mounted on the carriage 6, they may be mounted on, for example, the bottom chassis of the apparatus housing 1. In addition, the carriage 6 may be composed of first and second carriages, a light source unit and a reflection mirror are mounted on the first carriage, and a condensing lens and a line sensor are mounted on the second carriage.

  A light source unit 9 that irradiates light onto the reading surface R is mounted on the carriage 6. The light source unit 9 irradiates a reading line on the reading surface R (a reading width in the main scanning direction orthogonal to the reading surface R shown in FIG. 2) with linear light. The light source unit 9 can employ a configuration that irradiates one linear light and a configuration that irradiates two linear lights. For example, the former is configured to mount only the first light source unit 9a shown in FIG. 2, and the latter is configured to mount the first light source unit 9a and the second light source unit 9b shown in FIG.

  In addition, although not shown, the first light source unit 9a may be mounted on the carriage 6 and the second light source unit 9b may be fixedly disposed on the apparatus housing 1 so as to irradiate the second platen 2 with light. The purpose of providing the first and second light source units 9a and 9b in this manner is to increase the amount of light emitted from the reading surface R to enable high-speed reading, and to change the amount of light emitted from the second platen 2 to the first platen 3. This is because the document speed traveling on the second platen 2 can be read at a high speed by making it larger.

[Light source unit]
The present invention is characterized in that the light source unit 9 mounted on the carriage 6 or the light source unit 9 fixedly disposed on the second platen 2 is configured as follows. FIG. 2 shows a case where the first and second light source units 9 a and 9 b are mounted on the carriage 6. The carriage 6 configured in an appropriate shape is provided with a light source accommodating portion (light guide support frame) 13, and this accommodating portion 13 is configured at two locations, a first accommodating portion 13 a and a second accommodating portion 13 b, respectively. The light source units 9a and 9b described below are accommodated. Reference numeral 14 shown in FIG. 3 is a heat radiating fin (heat sink; heat radiating member) for radiating heat from a light source (light emitting body) 40 described later.

  FIG. 4 shows an assembly exploded view of the main part (light emitting part) of the light source unit 9 shown in FIG. 3, and the light source unit 9 of the present invention is composed of a light guide 30 and a light emitter 40. In addition, since the 1st light source unit 9a and the 2nd light source unit 9b are the same structures, the same code | symbol is attached | subjected and the structure is demonstrated about the 1st light source unit 9a.

  As shown in FIGS. 4 and 5, the light guide 30 is composed of a rod-shaped light transmitting member having a length corresponding to the reading width (reading line width) W of the reading surface R. The light guide 30 is made of a material having high translucency such as transparent acrylic resin and epoxy resin, and its cross-sectional shape is rectangular or fan-shaped as shown in the figure, and is formed on the left and right end surfaces 31L and 31R. The light emitter 40 is arranged. The light guide 30 has a light scattering surface 32 and a light emitting surface 33 disposed so as to face each other.

  That is, as shown in FIG. 5, the light scattering surface 32 and the light emitting surface 33 are arranged to face each other with a length of the reading line width W substantially in parallel with a distance Ld. The light scattering surface 32 is subjected to surface processing so as to diffusely reflect the light that is formed on the concavo-convex surface by painting, etching, molding or the like. Further, the light emitting surface 33 is surface-finished like a lens surface with high translucency.

  Therefore, the light introduced into the light guide 30 is diffused in a predetermined direction by the light scattering surface 32, and the light introduced into the light emitting surface 33 is reflected inside when the angle is equal to or larger than a predetermined critical angle, and when the angle is equal to or smaller than the critical angle. It is emitted to the outside. The light indicated by the arrow ha in FIG. 5 is reflected in the light guide 30 and dispersed in the reading line width W direction, and the light indicated by the arrow hb is emitted from the light emitting surface 33 to the reading surface R. Although not shown, light is incident in a spherical direction (360-degree direction; the illustrated one is a 60-degree wide-angle direction) from a light emitter 40, which will be described later, and irradiates the light scattering surface 32 and the light emitting surface 33.

  The light emitter 40 will now be described. The light emitter 40 is disposed on at least one end surface of the light guide 30. FIG. 5 shows a case where the light sources are arranged on the left and right end surfaces 31L and 31R, and the light sources on the left and right end surfaces are configured to have left and right symmetry. Although not shown, the light emitter 40 is disposed on one of the left and right end surfaces, and a reflecting member (mirror member) is disposed on the other side. The reflecting member at this time is configured so that the virtual light source is symmetrical with the light emitter 40.

[Embodiment of luminous body]
The light emitter 40 includes at least two light emitters 41 and 42 (first embodiment), or includes three light emitters 41, 42, and 43 (second embodiment), and light emitters 41, 42a, and 42b. It is configured (third embodiment), or is configured by four light emitters 41, 42, 43a, 43b (fourth embodiment), and is configured by light emitters 41a, 41b, 42a, 42b (fifth embodiment).

  In this case, the first light emitter 41 and the second light emitter 42 enter light from the left end surface 31L of the light guide 30 from different positions between the light scattering surface 32 and the light emitting surface 33. At the same time, the first light emitter 41 and the second light emitter 42 are arranged at a distance in the direction of the outgoing light path from the light emitting surface 33 toward the reading surface R (indicated by an arrow hx in FIG. 5).

  That is, the first light emitter 41 is arranged at a distance Ld1 and the second light emitter 42 is arranged at a distance Ld2 (Ld1 <Ld2) with respect to the scattering surface 32. The outgoing light path direction hx of the illustrated light guide 30 is configured to coincide with the normal direction of the light scattering surface 32. And each light-emitting body 41,42,43 is comprised by the planar light emitting element, and is comprised by white LED.

  FIG. 6A shows a layout structure (first embodiment) in which the light emitter 40 includes two light emitting elements, a first light emitter 41 and a second light emitter 42. A first light emitter 41 and a second light emitter 42 are arranged along the normal line (outgoing light path direction) hx of the light scattering surface 32. The first light emitter 41 is disposed at a distance Ld1 from the light scattering surface 32, and the second light emitter 42 is disposed at a distance Ld2. An offset amount dx is formed between the light emitters 41 and 42.

  As described above, the light scattering surface 32 is formed in a band shape along the reading line, and the emission direction is set in the direction perpendicular to the center (1/2 of the sub-scanning direction; point O in the figure). Has been. The first and second light emitters 41 and 42 are arranged on this normal line.

  FIG. 6B shows a layout structure (second embodiment) in which the light emitter 40 includes three light emitting elements of a first light emitter 41, a second light emitter 42, and a third light emitter 43. The first light emitter 41 is disposed at a distance Ld1 from the light scattering surface 32, the second light emitter 42 is disposed at a distance Ld2, and the third light emitter 43 is disposed at a distance Ld3. An offset amount dx is formed between the light emitters. This embodiment is also arranged on the normal line (exit optical path direction) hx described above.

  FIG. 6C shows a layout structure (third embodiment) in which the light emitter 40 is composed of a first light emitter 41 and a second light emitter 42, and the second light emitter is composed of two light emitting elements. The first light emitter 41 is disposed at a distance Ld1 from the light scattering surface 32, and the second light emitters 42a and 42b are both disposed at a distance Ld2 from the light scattering surface 32. The second light emitters 42a and 42b adjacent to the light emitting surface 33 are arranged at positions symmetrical with respect to the normal line hx.

  In this embodiment, the second light emitter 42 arranged at a position close to the light emitting surface 33 is constituted by two light emitting elements, and these two light emitting elements are arranged symmetrically in the outgoing light path direction (normal line) hx. It is characterized by doing.

  In FIG. 6D, a light emitting body 40 is composed of a first light emitting body 41, a second light emitting body 42, and a third light emitting body 43, and a third light emitting body is composed of two light emitting elements 43a and 43b. 4th Embodiment) is shown. The first light emitter 41 is disposed at a distance Ld1 position from the light scattering surface 32, the second light emitter 42 is disposed at a distance Ld2 position, and the third light emitter 43 is disposed at a distance Ld3 position. The first light emitter 41 and the second light emitter 42 are arranged on the normal line hx, and the light emitting elements 43a and 43b of the third light emitter 43 are arranged at positions symmetrical with respect to the normal line hx.

  In this embodiment, the third light emitter 43 disposed at a position close to the light emitting surface 33 is constituted by two light emitting elements, and these two light emitting elements are disposed symmetrically in the outgoing light path direction (normal line) hx. It is characterized by doing.

  In FIG. 6E, the light emitter 40 is composed of a first light emitter 41 and a second light emitter 42, the first light emitter is composed of two light emitting elements 41a and 41b, and the second light emitter is composed of two light emitting elements. The layout structure (5th Embodiment) comprised by element 42a, 42b is shown. The two light emitting elements constituting the first and second light emitters 41 and 42 are arranged at positions that are symmetrical about the normal line hx.

  In this embodiment, the first light emitter 41 disposed at a position close to the light scattering surface 32 and the second light emitter 42 disposed at a position close to the light emitting surface 33 are each constituted by two light emitting elements. These two light emitting elements are arranged symmetrically in the outgoing optical path direction (normal line) hx.

  In FIG. 6 (f), the light emitter 40 is composed of a first light emitter 41, a second light emitter 42, and a third light emitter 43, and the first light emitter 41 is composed of one light emitting element 41 and the second light emission. The layout structure (6th Embodiment) which comprises the body 42 by two light emitting element 42a, 42b and the 3rd light emitting body 43 by two light emitting element 43a, 43b is shown. The light emitting element constituting the first light emitter 41 has a normal line hx, and the two light emitting elements constituting the second and third light emitters 42 and 43 have an outgoing optical path direction (normal line) hx. They are arranged at symmetrical positions in the center.

  In this embodiment, the first light emitter 41 arranged at a position close to the light scattering surface 32 is one light emitting element, and the third light emitter 43 arranged at a position close to the light emitting surface 33 is two The light emitting element (43a, 43b) includes the second light emitting element 42 arranged at a position close to the first light emitting element 41, 43 and the two light emitting elements (42a, 42b). Two light emitting elements constituting the second and third light emitters 42 and 43 are arranged symmetrically in the outgoing optical path direction (normal line) hx.

  8 and 9 show an embodiment in which the light emitters 40 in the first to sixth embodiments described above are arranged at both ends of the light guide 30 as shown in FIG. As described above, a reflecting member (mirror member) may be disposed instead of one of the light emitters 40, and a virtual light source equivalent to the light emitter 40 may be configured by the reflecting member.

  In the present invention, as described above, the light source incident on the light guide 30 is composed of a plurality of light emitters 40 having substantially the same wavelength, and the incident position from the first light emitter 41 and the incident light from the second light emitter 42. It is characterized in that the position is set at a position that is separated from the light guide 30 in the direction of the outgoing light path (normal direction of the light scattering surface) hx.

  In this way, by arranging two or more light emitters at a distance in the direction of the outgoing light path, the linear light from the light guide 30 toward the reading surface R is matched (complementary) with the characteristics of the condenser lens. Is possible. Therefore, the light emission characteristics of the light emitter 40 in the above-described first to sixth embodiments will be described.

  FIG. 7 shows the light emission characteristics in the above-described fourth embodiment (four light-emitting element configurations). The X axis indicates the distance position in the reading line direction (main scanning direction of the line sensor), and the Y axis indicates illuminance. In the figure, LED1 indicates the light from the first light emitter 41, LED2 indicates the light from the second light emitter 42, and (LED3 + LED4) indicates the combined light from the third light emitter 43a and the light emitter 43b. . In the figure, Total indicates the total amount of light.

  Therefore, the light from the first light emitter 41 located closest to the light scattering surface 32 (near 15 mm in the figure) has a high main scanning direction end (left and right ends in FIG. 7) and gradually toward the central part in the main scanning direction. An illuminance curve that decays is formed. Next, the light from the second light emitter 42 located in the middle from the light scattering surface 32 is slightly higher from the end in the main scanning direction (near 20 mm in the figure) and gradually attenuates toward the center in the main scanning direction. Form an illuminance curve. The light from the third light emitters 43a and 43b located farthest from the light scattering surface 32 is high from the end in the main scanning direction toward the center (near 40 mm in the figure) and gradually attenuates toward the center in the main scanning direction. An illuminance curve is formed.

  Thus, when the height position (Ld1, Ld2, Ld3) of the light emitting body 40 in the outgoing light path direction hx is close to the light scattering surface 32, the amount of light emitted from the surface wave light emitting element is irradiated to the end portion in the main scanning direction. Becomes larger. This is because the light from the light emitting element is emitted in all directions with equal distribution, so that the light from the first light emitter 41 at a height position close to the light scattering surface 32 has a large amount of light applied to the end in the main scanning direction. This is because the amount of light emitted from the third light emitter 43 at a distant height is increased near the center of the main scanning direction.

  Therefore, as shown in FIG. 7, the total amount of light has a large illuminance at the end in the main scanning direction and attenuates toward the center. Therefore, light sources having the same structure are arranged on the right end surface 31R and the left end surface 31L of the light guide 30, respectively, and thus a light amount characteristic is obtained in which the light amount at both ends is large in the main scanning direction and the light amount at the central portion is small. This light quantity characteristic is designed to match (complement) the characteristic of the condenser lens 7.

  In this case, as shown in FIG. 5, the light quantity characteristics described above can be corrected by adjusting the light emitters 41 and 42 by an angle θ with respect to the normal direction hx of the light scattering surface 32. That is, the light emitters 41 and 42 shown in FIG. 5 are mounted on the circuit board 16, and when the mounting angle of the board 16 is tilted by plus θ clockwise, the light quantity at both ends in the main scanning direction increases, and conversely, it decreases minus counterclockwise. When θ is inclined, the amount of light at both ends in the main scanning direction is reduced, and this angle adjustment can easily match the characteristics of the condenser lens 7. Note that an optimum value for the mounting angle is 3 °.

  8 and 9 show the light quantity characteristics in the first to sixth embodiments described above. Since the light quantity difference can be understood from the principle described with reference to FIG. In the present invention, as described above, a plurality of light emitting elements are arranged at a distance in the direction of the outgoing light path, and at the same time, the light emitting body 40 that is close to the light emitting surface 33 is composed of two light emitting elements (the aforementioned third light emitting element) 4th, 5th, and 6th embodiment), and both of the light emitting elements are also arranged at symmetrical (line symmetrical) positions around the normal line hx. In this way, it is possible to prevent unevenness in the amount of light by combining the light from the plurality of light emitting elements with the light emitter close to the light emitting surface 33.

  FIG. 10 shows the mounting structure of the light emitters 41, 42, and 43 in the first to sixth embodiments described above. In the carriage 6, the first light source unit 9a and the second light source unit 9b are accommodated in the first accommodating portion 13a and the second accommodating portion 13b, respectively. A heat radiating member 14 is integrally formed on the unit frame 11 of the carriage 6. A circuit board 16 is fixed to the heat radiating member 14 via a heat-resistant sheet (heat-resistant resin plate) 15. Reference numeral 17 shown in the figure denotes a backup plate that supports the circuit board 16.

  Therefore, the circuit board 16 is integrally attached to the heat radiating member (heat sink) 14 by the backup plate 17, and the end face 31 of the light guide 30 is fixed to the backup plate 17. The above-mentioned light emitters 41 to 43 are mounted on the circuit board 16 with a planar light emitting element (the LED light emitting element in the drawing). The circuit board 16 on which the light emitting element is mounted is disposed with a gap d between the light emitting surface and the end surface 31L (31R) of the light guide 30. The optimum value of the gap d is 0.25 mm, and a range from 0.25 mm to 0.50 mm is set as an allowable value in an actual process.

[Explanation of Sixth Embodiment]
12 and 13 detail the sixth embodiment. The difference from the first embodiment described above with reference to FIG. 5 is that the gap d (0. 25 mm), the light emitting body 40 is disposed, and the other end 31R of the light guide 30 is in surface contact with the reflecting surface MR1 of the reflector MR (mirror). Naturally, the light quantity of the light emitter 40 is attenuated in the process of propagating through the light guide 30, and the light quantity on the other end 31R side of the light guide 30 is reduced, so that the reflector is in contact with the other end 31R of the light guide 30. The contact angle λ of MR is adjusted appropriately. The mount structure of the light emitters 41, 42 and 43 constituting the light emitter 40 has an arrangement relationship shown in FIG.

  Actually, FIG. 13 is a schematic diagram showing the light quantity characteristics according to the sixth embodiment, and the other end of the light guide 30 with respect to the inclination angle θ1 of the light emitter 40 facing the one end 31L of the light guide 30 is 2 °. The inclination angle λ1 of the reflecting surface MR1 of the reflector MR that contacts 31R is set and adjusted to an angle different from 3 °.

[Light source control configuration]
The control of the light source unit 9 will be described with reference to FIG. 2. The first light source 9a and the second light source 9b irradiate the reading surface R of the first platen 3 and the second platen 3 with light as shown in FIG. The light source unit 9a (9b) is not necessarily composed of two light sources as shown in the figure, and may be composed of one or three or more light sources. In this case, in the document feeding unit B described later, the speed of the document traveling on the second platen 2 is set higher than the speed at which the carriage 6 moves along the first platen 3.

  That is, the reading speed of the second platen 2 is higher than the reading speed of the first platen 3. For this reason, it is preferable to make the second platen 2 higher than the first platen 3 with respect to the amount of light applied to the document.

  Such light amount adjustment is possible by adopting one of the following methods. (1) The power supplied to the light source unit 9 mounted on the carriage 6 is adjusted in level. For example, a power supply circuit that supplies power to the light source unit 9 is provided with a supply voltage or supply current switching unit, and a light amount adjustment unit that adjusts the power supplied to the lamp. Since this light amount adjusting means is widely known as PWM control, its detailed description is omitted.

  In the next method, (2) light amount adjusting means for selectively lighting the first and second and at least two light source units 9a and 9b mounted on the carriage 6 is provided. The apparatus shown in FIG. 2 has a first light guide 30a and a second light guide 30b mounted on the carriage 6, and supplies power to the first light guide 30a when irradiating the original on the first platen 3 with light. Then, when irradiating light on the original on the first platen 3 and irradiating light on the original on the second platen 2, power is supplied to the first light guide 30a and the second light guide 30b, and the second The document on the platen 2 is configured to irradiate light.

  In such a configuration, when the carriage 6 is positioned on the first platen 3, the first light guide 30a is turned on, and when the carriage 6 is positioned on the second platen 2, the first light guide 30a and the second light guide 30b are turned on. This makes it possible to adjust the amount of light applied to the document, and the switching circuit for turning the supply power “ON” and “OFF” constitutes the light amount adjusting means.

[Configuration of Document Feed Unit]
As shown in FIG. 1, the document feeding unit B is disposed above the first and second platens 3 and 2 so as to cover the first and second platens 3 and 2, and a lead roller (document feeding) for feeding a document sheet to the second platen 2. Feeding means) 21 and a carry-out roller 22. Further, on the upstream side of the read roller 21, a paper feed stacker 23 for stacking and storing document sheets, a paper feed roller 24 for stacking and feeding the sheets one by one, separated and fed. A registration roller pair 25 for correcting the skew of the front end of the sheet is disposed. 26 is a paper feed path for guiding a document sheet from the paper feed stacker 23 to the second platen 2, and S1 is a lead sensor for detecting the leading edge of the document reaching the platen.

  In the illustrated apparatus, a backup roller 27 for guiding the document sheet is disposed above the second platen 2. This backup roller 27 rotates at the same peripheral speed as the lead roller 21 to fit the original sheet on the second platen 2, and a backup guide may be arranged above the platen without providing this backup roller 27.

  A paper discharge roller 28 and a paper discharge stacker 29 are disposed on the downstream side of the carry-out roller 22. As shown in FIG. 2, the paper discharge stacker 29 is arranged vertically below the paper feed stacker 23, and a platen cover 5 for pressing and supporting the original sheet on the first platen 3 is provided at the bottom. Yes.

  The document feeding unit B configured as described above is installed in the apparatus housing 1 of the image reading unit A so as to be freely opened and closed. The original sheet is placed and set with the first platen 3 opened, and the original is covered with the platen cover 5 of the original feeding unit B.

  On the other hand, when the document feeding unit B is opened and closed, the frame of the document feeding unit B has a first platen so that the distance (document transport gap) between the first platen 3 and the backup roller 27 (or backup guide) does not change. 3 is provided with a positioning projection (stopper member; not shown).

2 Second platen 3 First platen 6 Carriage 7 Condensing lens 8 Line sensor 9 Light source unit 9a First light source unit 9b Second light source unit A Image reading device W Reading line width 13 Light source accommodating portion (light guide support frame)
13a 1st accommodating part 13b 2nd accommodating part 14 Heat radiation member 15 Heat-resistant sheet 16 Circuit board 30 Light guide 30a 1st light guide 30b 2nd light guide 31L Left end surface 31R Right end surface 32 Light scattering surface 33 Light output surface 40 Light emitter 41 First light emitter 42 Second light emitter 43 Third light emitter hx Normal direction

Claims (5)

A light source unit that scatters and reflects light from a light source and irradiates a reading surface with linear light,
A light guide having a light scattering surface that scatters light in a line direction along the reading surface, and a light emitting surface that emits light from the light scattering surface toward the reading surface;
A light emitter having a light emitting surface disposed on at least one end surface of the light guide;
With
The light emitting surface is spaced apart from the end surface of the light guide and is inclined at a predetermined angle with respect to the normal line of the light scattering surface . The light guide is composed of a translucent member having a light scattering surface and a light exit surface having a length corresponding to the reading line width,
The light emitting surface of the light emitter is disposed on one end surface of the light guide, and the other surface of the light guide is disposed with a reflective surface that reflects light from the light emitting surface. The light source unit according to claim 1, wherein The light source unit according to claim 2 , wherein the light emitting surface and the reflecting surface are inclined at different angles with respect to a normal line of the light diffusing surface . The distance between the light emitting surface of the light emitter and the end surface of the light guide is 0.25 mm, and the inclination angle between the light emitting surface and the normal of the light scattering surface is set to 3 degrees. The light source unit according to claim 1. Wherein the light emitting surface of the light emitting element and the reflecting surface of the light guide, according to claim 2 or 3, characterized in that it is inclined at a predetermined angle toward the center of the reading line width of the light guide Light source unit.

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