JP2012142847A - Line illumination optical system, and image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a line illumination optical system which can be made compact while suppressing occurrence of unevenness in illumination distribution, and to provide an image reader equipped with the line illumination optical system.SOLUTION: The line illumination optical system comprises two illumination units 1 each consisting of a substrate 11 on which a plurality of LEDs 12 are arranged linearly in the main scanning direction, and a light guide member 13 which guides the light emitted from the LEDs 12 to an irradiated part 19. The emitting surface of the LEDs 12 in at least one illumination unit 1 is arranged to have an inclination angle θ in a fixed direction for the LED array direction so that the illumination light 17 from one illumination unit 1a in the irradiated part 19 has a deviation of the length equal to 0.5 times of the array pitch in the LED array direction for the illumination light 18 from the other illumination unit 1b. An image reader equipped with the line illumination optical system is also provided.

Description

  The present invention relates to a line illumination optical system and an image reading apparatus including the line illumination optical system.

  The line illumination optical system has a structure in which a light emitting element array is formed by linearly arranging a large number of light emitting elements such as LEDs (Light Emitting Diodes). The irradiated light from the light emitting element array is irradiated onto the irradiated portion, and a read image such as a document placed on the irradiated portion can be illuminated in a line.

  As an image reading apparatus including such a line illumination optical system, reading light that travels along the reading optical axis after being reflected by the irradiated portion is received by a CCD (Charge Coupled Device) or the like through a lens. An image formed on an image reading unit of an element and reading an image in a line shape is known.

  In the line illumination optical system, when the scanned image is illuminated from one direction, for example, when scanning a partially pasted paper or a wrinkled document, a shadow is generated on the image surface corresponding to the unevenness. As a result, a shadow is generated in the read image and the quality is deteriorated.

  On the other hand, by illuminating the read image from two directions, it is possible to prevent the occurrence of shadows due to minute irregularities, so two illumination units each including a substrate on which LEDs are mounted are arranged opposite to each other. A method of illuminating a document has been proposed (see, for example, Patent Documents 1 to 5).

  A line illumination optical system having a configuration in which a plurality of point light sources are arranged linearly in the main scanning direction (reading line direction) can directly irradiate the irradiation area of a document with light emitted from each point light source in the main scanning direction. There is a problem that illuminance ripple (a steep change in illuminance distribution with maximum and minimum values), which is uneven in illuminance distribution, occurs, and image density unevenness caused by illuminance ripple occurs when an image is formed according to the read image data. is there.

  With respect to this problem, in Patent Documents 1 and 3, in two illumination units arranged opposite to each other in the main scanning direction, the arrangement of LEDs mounted on the substrate is staggered on each of the opposite sides. It is described that the illuminance ripple is reduced.

  However, by shifting the arrangement pitch of the LEDs to make a staggered arrangement, the position of the LED at the outermost portion protrudes by 1/2 pitch, for example, each substrate is arranged to spread by 1/4 to both ends. End up. For this reason, by adopting the staggered arrangement, the illuminating device is enlarged in the main scanning direction, and there is a problem that it is impossible to meet the demand for downsizing.

  Therefore, an object of the present invention is to provide a line illumination optical system that can suppress the occurrence of unevenness in illuminance distribution and can be miniaturized, and an image reading apparatus including the line illumination optical system.

In order to solve the above problems, a line illumination optical system and an image reading apparatus according to the present invention are as follows.
[1] Two illumination units each including a substrate in which a plurality of LEDs are linearly arranged in the main scanning direction and a light guide member that guides light emitted from the LEDs to an irradiated portion,
At least so that the irradiation light from one of the illumination units in the irradiated portion has a deviation of 0.5 times the arrangement pitch in the LED arrangement direction with respect to the irradiation light from the other illumination unit. The line illumination optical system is characterized in that a surface orthogonal to the optical axis of the LED of one of the illumination units is arranged so as to have an inclination angle θ in a certain direction with respect to the LED arrangement direction.
[2] The line illumination optics according to [1], wherein the LED emission surfaces of both of the illumination units are arranged to have an inclination angle θ in a certain direction with respect to the LED arrangement direction. It is a system.
[3] The line illumination optical system according to [1] or [2], wherein the plurality of LEDs are arranged at unequal pitches.
[4] The line illumination optical system according to any one of [1] to [3], wherein the light guide member includes a plurality of mirrors.
[5] The line illumination optical system according to any one of [1] to [4], and a reading optical system, wherein image information of a document illuminated by the line illumination optical system is read. An image reading apparatus.

As an effect of the present invention, according to the invention of claim 1, a plurality of LEDs are linearly arranged in the main scanning direction, and a light guide member that guides light emitted from the LEDs to an irradiated portion. The illumination light from one of the illumination units in the irradiated portion is 0.5 times as long as the arrangement pitch in the LED arrangement direction with respect to the illumination light from the other illumination unit. A line illumination optical system in which a plane orthogonal to the LED optical axis of at least one of the illumination units is arranged so as to have an inclination angle θ in a certain direction with respect to the LED arrangement direction so as to have a deviation of Therefore, the emitted light from the LEDs can be shifted by 0.5 times the array pitch without shifting the actual phase position of the LEDs in the main scanning direction on the substrate and expanding the array range.
According to a second aspect of the present invention, in the line illumination optical system according to the first aspect, the emission surfaces of the LEDs of both of the illumination units have an inclination angle θ in a certain direction with respect to the LED arrangement direction. Since the same LED mounting substrate can be used in the two lighting units, the cost can be reduced.
According to the invention of claim 3, in the line illumination optical system according to claim 1 or 2, since the plurality of LEDs are arranged at an unequal pitch, the illuminance distribution in the main scanning direction is set as a desired distribution. For example, it is possible to reversely correct a decrease in the reading lens peripheral light amount in the image reading apparatus.
According to a fourth aspect of the present invention, in the line illumination optical system according to any one of the first to third aspects, since the light guide member is composed of a plurality of mirrors, high-efficiency illumination can be realized. it can.
According to a fifth aspect of the invention, there is provided an image reading system comprising the line illumination optical system according to any one of the first to fourth aspects and a reading optical system, wherein the image information of a document illuminated by the line illumination optical system is read. Since this is an apparatus, it is possible to provide an image reading apparatus that can suppress the occurrence of unevenness in illuminance distribution and can be miniaturized.

It is a schematic diagram of the cross section which shows an example of the line illumination optical system of this invention. It is a schematic diagram explaining the light irradiation by the 1st embodiment of the line illumination optical system of this invention. It is a schematic diagram explaining the light irradiation by the 2nd embodiment of the line illumination optical system of this invention. It is a schematic diagram explaining the light irradiation by the 3rd embodiment of the line illumination optical system of this invention. It is a schematic diagram explaining the light irradiation by the 4th embodiment of the line illumination optical system of this invention. It is a schematic diagram of the cross section which shows the other example of the line illumination optical system of this invention. It is a conceptual diagram which shows one embodiment of the image reading apparatus of this invention.

  A line illumination optical system and an image reading apparatus according to the present invention will be described below with reference to the drawings. It should be noted that the present invention is not limited to the embodiments of the examples shown below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art. Any aspect is included in the scope of the present invention as long as the operations and effects of the present invention are exhibited.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the line illumination optical system of the present invention.
As shown in FIG. 1, the line illumination optical system of the present invention includes a substrate 11 (11a and 11b) in which a plurality of LEDs 12 (12a and 12b) are linearly arranged in the main scanning direction, and light emitted from the LEDs 12. The light guide member 13 (13a and 13b) that guides the light to the irradiated portion 19 includes two illumination units 1 (1a and 1b) that are held by the holding member 10 (10a and 10b).

  The irradiation light 15 from one illumination unit (for example, 1a) is 0.5 times the array pitch in the LED array direction in the irradiation region of the irradiated portion 19 with respect to the irradiation light 16 from the other illumination unit (for example, 1b). The surface orthogonal to the optical axis 15 of the LED 12a of at least one lighting unit 1a is arranged so as to have a tilt angle θ in a certain direction with respect to the LED arrangement direction. That is, the LED 12a is arranged so that the irradiation area 17 of the irradiation area of one illumination unit 1a and the irradiation area 18 of the irradiation area of the other illumination unit 1b are shifted by 0.5 times the arrangement pitch in the main scanning direction. To do. Note that the inclination angle θ may all be the same angle, or may be different for each LED.

  Further, the emission surfaces of the LEDs 12 of both illumination units 1 can be arranged so as to have an inclination angle θ in a certain direction with respect to the LED arrangement direction. In the illumination units 1a and 1b, when the inclination angle θ of the LED 12 is set to be the same, the same LED mounting board can be used.

  Furthermore, the arrangement pitch of the plurality of LEDs 12 may be equal or unequal.

  In the line illumination optical system of the present invention, the LED 12 will be described as a side-view type LED element having a light emitting surface that emits light in parallel to the mounting surface of the substrate 11 (the light emitting surface faces the horizontal direction).

[First Embodiment]
FIGS. 2A to 2C are diagrams for explaining the first embodiment. FIG. 2A is a plan view of the illumination unit 1a viewed in the direction indicated by the arrow A in the line illumination optical system shown in FIG. ), A plan view of the illumination unit 1b viewed in the direction indicated by the arrow B is shown in (B), and a plan view of the irradiated portion 19 viewed in the direction indicated by the arrow C is shown in (C).

As shown in FIG. 2A, the pitches P1a of the plurality of LEDs 12a mounted on the substrate 11a of the lighting unit 1a are all constant (equal pitch), and the inclination angles θ of the LEDs 12a are all constant angles.
On the other hand, as shown in FIG. 2B, the pitches P1b of the plurality of LEDs 12b mounted on the substrate 11b of the lighting unit 1b are all constant (equal pitch). The LED 12b is not inclined and θ = 0 [°].

Assuming that the mounting pitch P1a of the LEDs 12a is 10 mm and the optical distance L from the emitting surface of the LED 12a to the irradiated surface (original surface) 19 is 20 mm, the angle at which the LED 12a is rotated to mount it, that is, the optical axis of the LED 12a The inclination angle θ with respect to the LED arrangement direction of the plane orthogonal to 15 is calculated by the following equation (1).
tan ⁻¹ (10/2/20) = 14 [°] (1)
Here, the optical distance L is not a physical distance, and is calculated as follows when the light guide member 13a is used.
The distance from the LED emission surface to the light guide member is L1,
The length of the light guide member is L2,
The refractive index of the light guide member is n,
When the distance from the light guide member exit surface to the illuminated surface is L3,
L = L1 + L2 / n + L3

  As shown in FIG. 2C, the illumination light 17 from the illumination unit 1a and the illumination light 18 from the illumination unit 1b are irradiated with a 0.5 pitch deviation on the irradiated surface (document surface) 19. The illuminance ripple in the main scanning direction is reduced.

[Second Embodiment]
FIGS. 3A to 3C are diagrams for explaining the second embodiment. FIG. 3A is a plan view of the illumination unit 1a viewed in the direction indicated by the arrow A in the line illumination optical system shown in FIG. ), A plan view of the illumination unit 1b viewed in the direction indicated by the arrow B is shown in (B), and a plan view of the irradiated portion 19 viewed in the direction indicated by the arrow C is shown in (C).

  As shown in FIG. 3A, the pitches P2a of the plurality of LEDs 12a mounted on the substrate 11a of the lighting unit 1a are all constant (equal pitch), and the inclination angles θ of the LEDs 12a are all constant angles. On the other hand, as shown in FIG. 3B, the pitches P2b of the LEDs 12b mounted on the substrate 11b of the lighting unit 1b are all constant (equal pitch), and the inclination angles θ of the LEDs 12b are all constant angles.

When the mounting pitch P2a of the LED 12a and the mounting pitch P2b of the LED 12b are 20 mm, and the optical distance L from the emitting surface of the LEDs 12a and 12b to the irradiated surface (original surface) 19 is 20 mm, the LED 12a and the LED 12b are inclined and mounted. The tilt angle θ with respect to the LED arrangement direction of the surface orthogonal to the optical axis of the LED 12 is calculated by the following equation (2).
tan ⁻¹ (10/4/20) = 7.1 [°] (2)
The optical distance L is calculated as follows.
L = L1 + L2 / n + L3
(However, the distance from the exit surface of the LED to the light guide member is L1, the length of the light guide member is L2, the refractive index of the light guide member is n, and the distance from the light guide member exit surface to the irradiated surface is L3. To do.)

  As shown in FIG. 3C, the illumination light 17 from the illumination unit 1a and the illumination light 18 from the illumination unit 1b are irradiated on the irradiated surface (document surface) 19 with a shift of 0.5 pitch. Therefore, the illuminance ripple in the main scanning direction is reduced.

[Third Embodiment]
FIGS. 4A to 4C are views for explaining the third embodiment. FIG. 4A is a plan view of the illumination unit 1a viewed in the direction indicated by the arrow A in the line illumination optical system shown in FIG. ), A plan view of the illumination unit 1b viewed in the direction indicated by the arrow B is shown in (B), and a plan view of the irradiated portion 19 viewed in the direction indicated by the arrow C is shown in (C).

  As shown in FIG. 4A, the pitches of the plurality of LEDs 12a mounted on the substrate 11a of the lighting unit 1a are unequal pitches, and the inclination angles θ of the LEDs 12a are also different angles. On the other hand, as shown in FIG. 4B, the pitch of the plurality of LEDs 12b mounted on the substrate 11b of the lighting unit 1b is also unequal, but is not inclined and θ = 0 [°]. .

  The unequal pitches of the LEDs 12a and 12b are, for example, the cosine of the lens when the line illumination optical system according to the present invention reads an object (such as an original) that is line-illuminated by a lens system such as an image reader (scanner). In order to reversely correct the peripheral light amount decrease due to the law, it is used to reduce the pitch toward the peripheral part.

Here, among the LEDs 12a shown in FIG. 4 (A), assuming that the pitch between the LED shown by C1 and the adjacent LED for C2 shown in FIG. 4 (B) corresponding to C1 is P3, The angle at which C1 is inclined to be mounted, that is, the inclination angle θ of the surface perpendicular to the optical axis 15 at C1 with respect to the LED arrangement direction is L, and the optical distance from the emitting surface of the LED 12 to the irradiated surface 19 is L. Then, it calculates with the following formula | equation (3).
tan ⁻¹ (P3 / 2 / L) (3)
The optical distance L is calculated as follows.
L = L1 + L2 / n + L3
(However, the distance from the exit surface of the LED to the light guide member is L1, the length of the light guide member is L2, the refractive index of the light guide member is n, and the distance from the light guide member exit surface to the irradiated surface is L3. To do.)

  According to the condition of the above formula (3), the LED light from C1 and the LED light from C2 are irradiated on the irradiated surface 19 with a shift of 1/2 the pitch P3 in the main scanning direction. . Note that the inclination angle θ of each of the LEDs 12a other than C1 can be selected by calculating in the same manner.

  By selecting the tilt angle as described above, the illumination light 17 from the illumination unit 1a and the illumination light 18 from the illumination unit 1b on the irradiated surface (document surface) 19 as shown in FIG. 4C. Irradiates with an offset of 0.5 pitch, so that the illuminance ripple in the main scanning direction is reduced.

[Fourth Embodiment]
FIGS. 5A to 5C are diagrams for explaining the fourth embodiment. FIG. 5A is a plan view of the illumination unit 1a viewed in the direction indicated by the arrow A in the line illumination optical system shown in FIG. ), A plan view of the illumination unit 1b viewed in the direction indicated by the arrow B is shown in (B), and a plan view of the irradiated portion 19 viewed in the direction indicated by the arrow C is shown in (C).

  As shown in FIG. 5A, the pitches of the plurality of LEDs 12a mounted on the substrate 11a of the lighting unit 1a are unequal pitches, and the inclination angles θ of the LEDs 12a are different angles. As shown in FIG. 5B, the pitches of the plurality of LEDs 12b mounted on the substrate 11b of the lighting unit 1b are also unequal pitches, and the inclination angles θ of the LEDs 12b are also different angles.

Here, among the LEDs 12a shown in FIG. 5 (A), assuming that the pitch between the LED shown by C3 and the adjacent LED for C4 shown in FIG. 5 (B) corresponding to C3 is P4, The angle at which C3 and C4 are rotated for mounting, that is, the tilt angle θ with respect to the plane perpendicular to the optical axis and the LED array direction, is L, where the optical distance from the emitting surface of the LED 12 to the illuminated surface 19 is L. Is calculated by the following equation (4).
tan ⁻¹ (P4 / 4 / L) (4)
The optical distance L is calculated as follows.
L = L1 + L2 / n + L3
(However, the distance from the exit surface of the LED to the light guide member is L1, the length of the light guide member is L2, the refractive index of the light guide member is n, and the distance from the light guide member exit surface to the irradiated surface is L3. To do.)

  According to the condition of the above formula (4), the LED light from C3 and the LED light from C4 are irradiated on the irradiated surface 19 with a shift of 1/2 the pitch P4 in the main scanning direction. . For the LEDs 12 other than C3 and C4, the inclination angle θ can be selected by calculating in the same manner.

  By selecting the inclination angle θ as described above, the illumination light 17 from the illumination unit 1a and the illumination light from the illumination unit 1b on the irradiated surface (document surface) 19 as shown in FIG. 5C. 18 irradiates with a 0.5 pitch shift, so that the illuminance ripple in the main scanning direction is reduced.

[Fifth Embodiment]
FIG. 6 is a schematic cross-sectional view showing another example of the line illumination optical system of the present invention.
As shown in FIG. 6, the light guide member 14 that guides the light emitted from the LED 12 to the irradiated portion 19 is composed of a plurality of mirrors.
If the light emitted from the LED 12 is reflected by the mirror 14, high-efficiency illumination can be performed. In addition, the direction of the optical axis can be greatly inclined.

[Image reading device]
FIG. 6 shows a schematic diagram of an example of the image reading apparatus of the present invention.
The image reading apparatus of the present invention includes the line illumination optical system 51 of the present invention and a reading optical system, and reads image information of a document 56 illuminated by the line illumination optical system 51.
Specifically, it has a line illumination optical system 51 of the present invention, a folding mirror 52, a reading lens 53, and a line sensor (CCD) 54, which are arranged below the contact glass 55, and is irradiated with line-shaped illumination. The reflected light of the original 56 is read by the line sensor 54 via the folding mirror 52 and the reading lens 53.

  Even if the number of LEDs is small, since the illuminance ripple in the main scanning direction is reduced, it is not necessary to increase the number of LEDs more than necessary, which is advantageous for further miniaturization and cost reduction.

  As described above, according to the line illumination optical system of the present invention, it is possible to suppress the generation of illuminance ripple in the main scanning direction and reduce the size without increasing the number of LEDs. The apparatus equipped with the line illumination optical system of the present invention is not limited to a multifunction peripheral (copy machine) equipped with the image reading apparatus as described above, but also an illumination optical system of an inspection apparatus, for example, a liquid crystal display device (liquid crystal television). The present invention can also be applied to line illumination for detecting dust on a glass substrate (mother glass).

1 Illumination unit 10 Holding member 11 Substrate 12 LED
13 Light guide member 19 Irradiated part

JP 2005-277779 A JP 2008-67276 A JP 2008-118246 A JP 2008-219511 A Japanese Patent Laid-Open No. 9-50510

Claims (5)

Two illumination units comprising a substrate in which a plurality of LEDs are linearly arranged in the main scanning direction and a light guide member that guides light emitted from the LEDs to an irradiated portion,
At least so that the irradiation light from one of the illumination units in the irradiated portion has a deviation of 0.5 times the arrangement pitch in the LED arrangement direction with respect to the irradiation light from the other illumination unit. A line illumination optical system, wherein a surface orthogonal to the optical axis of the LED of one of the illumination units is arranged so as to have an inclination angle θ in a certain direction with respect to the LED arrangement direction.   2. The line illumination optical system according to claim 1, wherein the emission surfaces of the LEDs of both of the illumination units are arranged so as to have an inclination angle θ in a fixed direction with respect to the LED arrangement direction.   The line illumination optical system according to claim 1, wherein the plurality of LEDs are arranged at unequal pitches.   The line illumination optical system according to claim 1, wherein the light guide member includes a plurality of mirrors.   An image reading apparatus comprising the line illumination optical system according to claim 1 and a reading optical system, and reading image information of a document illuminated by the line illumination optical system.

Images