JP2006128896A - Illumination device and image input device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device capable of obtaining uniform illumination light without color unevenness.
An LED chip 400R provided on an LED substrate emits R light, an LED chip 400G emits G light, and an LED chip 400B emits B light to a reflection optical system 402, respectively. The B light is reflected toward the incident surface 410 of the light guide panel 41 by the dichroic mirror 407B of the reflective optical system 402. The G light passes through the dichroic mirror 407B, is reflected by the dichroic mirror 407G, passes through the dichroic mirror 407B again, and is emitted toward the incident surface 410. The R light passes through the dichroic mirrors 407B and 407G, is reflected by the total reflection mirror 408, passes through the dichroic mirrors 407B and 407G again, and is emitted toward the incident surface 410. As a result, the optical axes of R light, G light, and B light are aligned on the same axis, and are incident on the same position on the incident surface 410, respectively.
[Selection] Figure 3

Description

  The present invention relates to an illumination device that performs surface illumination, and an image input device including the illumination device.

  In an image input device such as a liquid crystal display device or a scanner of a portable electronic device, a light guide panel is used to perform surface illumination (see, for example, Patent Document 1). For example, in an image input device, an original is illuminated by an illumination device, and light transmitted through the original is read by a photoelectric conversion element such as a CCD. When an area CCD is used for the photoelectric conversion element, the entire reading area is generally illuminated using a light guide panel.

  In such an illuminating device, the LED light source is disposed on the end surface of the light guide panel, the LED light is incident from the panel end surface, reflected and diffused inside the light guide panel, and the illumination light is emitted from the surface facing the document. . The LED light source is provided with a single color LED chip that generates red (R) light, green (G) light, and blue (B) light. These LED chips are turned on sequentially or simultaneously, and each color component transmitted through the document is read by the CCD area sensor. In reading a transparent original, a high brightness of the light source is advantageous for the reading speed and S / N ratio, so that a plurality of single-color LED chips are generally used.

Japanese Patent Laid-Open No. 2002-210045

  However, in the above-described conventional apparatus, since the R, G, B single color LED chips are arranged in the thickness direction of the light guide panel, the incident points on the light guide panel for each color light are different. become. For this reason, the reflection path of each color light in the light guide panel is not the same, and there is a case where a phenomenon that the color is partially different or a difference in brightness occurs. Furthermore, if each single-color LED chip is increased to increase the amount of light in order to increase the brightness, the distance between the respective color lights becomes larger and uniform illumination light cannot be obtained.

The invention of claim 1 is applied to an illumination device that performs surface illumination by sequentially or simultaneously entering a plurality of colored lights on the side surface of the light guide panel and emitting illumination light formed by the colored light from the emission surface of the light guide panel. A light source that emits a plurality of colored lights having different optical axes, and an optical that causes each of the plurality of colored lights emitted from the light sources to enter the side surfaces of the light guide panel with the respective optical axes aligned on the same axis System.
According to a second aspect of the present invention, in the illumination device according to the first aspect, the light source emits first, second and third color lights, respectively, and the optical system reflects the first color light on the same axis. A first dichroic mirror to be aligned, a second dichroic mirror that is disposed in parallel with the first dichroic mirror at a first predetermined interval, reflects the second color light, and aligns on the same axis, and the first dichroic The mirror includes a mirror and a reflecting mirror that is arranged in parallel at a second predetermined interval and reflects the third color light so as to be aligned on the same axis.
According to a third aspect of the present invention, in the illuminating device according to the first or second aspect, a plurality of sets of light sources that respectively emit a plurality of colored lights are provided.
According to a fourth aspect of the present invention, there is provided an image input device comprising: the illumination device according to any one of the first to third aspects; and an imaging unit that detects an image of a document by detecting light from the document illuminated by the illumination device. It is characterized by providing.

  According to the present invention, since a plurality of color lights are incident on the side surface of the light guide panel with their optical axes aligned on the same axis, uniform illumination light with reduced color unevenness can be obtained. .

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an image input device using an illumination device according to the present invention. FIG. 1 is a block diagram illustrating a schematic configuration of an image input apparatus. The image input apparatus 1 includes a main body 2 having a reading optical system 4, and an adapter unit 3 that holds a document 30 and is attached to and detached from the main body 2. Consists of. There are several types of adapter unit 3 depending on the type of document 30, and various documents 30 can be read by replacing them.

  The reading optical system 4 includes a light source unit 40, a light guide panel 41, a reading sensor 42 such as a CCD area sensor, a mirror 43 and a lens 44 for projecting light transmitted through the document 30 onto the reading sensor 42. Is provided. The light source unit 40 is controlled to be turned on via the illumination drive circuit 22 according to an instruction from the CPU 21. Illumination light emitted from the light source unit 40 in the left direction in the figure enters the light guide panel 41 from the side surface of the light guide panel 41.

  As will be described later, the light source section 40 has a plurality of LED chips that generate R light, G light, and B light, and the illumination drive circuit 22 lights these LED chips sequentially or simultaneously according to the conditions of the reading operation. . For example, when the reading sensor 42 is a monochrome CCD sensor, the color image data of one screen is obtained by sequentially turning on R, G, and B and reading them. Details of the light source unit 40 and the light guide panel 41 will be described later.

  The illumination light incident on the light guide panel 41 is reflected and diffused inside the light guide panel 41, and the illumination light is emitted from the lower surface facing the document 30 toward the document 30. The illumination light passes through the document held by the adapter unit 3, and its optical path is bent 90 degrees rightward by the mirror 43, and a document image is formed on the reading sensor 42 by the lens 44.

  The photoelectric conversion output of the reading sensor 42 is input to the signal processing circuit 23 as an analog image signal, where processing such as amplification, correlated double sampling, shading correction, and dark current correction is performed. The processed image signal is converted into a digital signal by an A / D converter (not shown), and the image information converted into the digital signal is sent to the CPU 21 and temporarily stored in the memory 24.

  Thereafter, the image information stored in the memory 24 is transmitted to the host computer 5 via the external interface 25. The host computer 5 includes an arithmetic processing unit, a storage device such as a hard disk, an input device such as a keyboard and a mouse, and a display device such as a CRT and a liquid crystal display. Dedicated driver software is incorporated in the host computer 5, and various functions of the image reading system including image reading are supported by the driver software.

  Focusing of the reading optical system 4 with respect to the document 30 is performed by an AF motor 26 that rotationally drives a lead screw 27. The lead screw 27 is screwed with a nut 28 provided at the lower portion of the reading optical system 4, and when the lead screw 27 is rotationally driven by the AF motor 26, the entire reading optical system 4 is moved in the optical axis direction (vertical direction in the drawing). Move up and down. The AF motor 26 is driven and controlled by an AF motor driving circuit 29 based on an instruction from the CPU 21.

  2 is a perspective view showing the light source unit 40 and the light guide panel 41, and FIG. 3 is a cross-sectional view taken along the line AA of FIG. The light source unit 40 is provided at a position facing the incident surface 410 of the light guide panel 41, and includes an LED substrate 401 on which the LED chips 400B, 400G, and 400R are disposed and a reflective optical system 402. Although not shown in FIG. 2, the other surfaces of the light guide panel 41 other than the entrance surface 410 and the exit surface 411 are surrounded by a white reflecting member 413 as shown in FIG. 3.

  FIG. 4 is a plan view of the LED substrate 401 as viewed from the reflective optical system 402 side. A plurality of sets of light sources are provided along the longitudinal direction of the LED substrate 401. The light source sets are a set of the LED chip 400B for B light, the LED chip 400G for G light, and the LED chip 400R for R light. In FIG. 4, four sets of light sources are provided. However, the light source unit 40 may be provided with a higher luminance by arranging more than four sets. In addition, the space | interval of each LED chip 400B, 400G, and 400R located in the upper and lower sides in the drawing is set to d.

  As shown in FIG. 3, in a state where the LED substrate 401 is fixed to the fixing portion 403, the row of LED chips 400 </ b> B is disposed so as to be closest to the incident surface 410 of the light guide panel 41. The surface formed by the emission surface of each LED chip 400B, 400G, 400R forms an angle of 90 degrees with respect to the incident surface 410 of the light guide panel 41. Therefore, the emission directions of the B light, the G light, and the R light emitted from the LED chips 400B, 400G, and 400R are emitted downward in the drawing parallel to the incident surface 410.

  As shown in FIG. 3, the reflective optical system 402 is obtained by bonding parallel transparent members 404 and 405 made of optical glass or the like, and a G light wavelength is applied to the bonding surface between the parallel transparent member 404 and the parallel transparent member 405. A dichroic mirror 407G that reflects (wavelength of about 560 nm or less) is formed. Further, a dichroic mirror 407B that reflects only the B light wavelength (wavelength of about 490 nm or less) is formed on the surface of the parallel transparent member 404, and a total reflection mirror 408 is formed on the surface of the parallel transparent member 405. The reflective optical system 402 is arranged such that B light, G light, and R light are incident on the dichroic mirror 407B at an angle of 45 degrees.

  FIG. 5 is a diagram for explaining the operation of the reflection optical system 402. The incident angles of B light, G light, and R light are 45 degrees, and the interval between the incident positions is L. As described above, since the distance between the LED chips 400B, 400G, and 400R is d, the distance L is “L = √2 · d”. The B light emitted from the LED chip 400B is totally reflected by the dichroic mirror 407B. As a result, as shown in FIG. 3, the optical path of the B light is bent 90 degrees toward the light guide panel 41.

Similarly, the G light emitted from the LED chip 400G enters the reflection optical system 402 at an incident angle of 45 degrees, travels through the parallel transparent member 404 after passing through the dichroic mirror 407B. If the refractive indexes of the parallel transparent members 404 and 405 with respect to the G light wavelength are n _G , the refraction angle θ _G is given by the following equation (1).
sinθ _G = 1 / (√2 · n _G ) (1)

The G light incident on the parallel transparent member 404 is totally reflected by the dichroic mirror 407G, passes through the dichroic mirror 407B, and is emitted at an angle of 45 degrees from the same position as the incident position of B light (= reflection position). For this purpose, the interval t1 between the dichroic mirror 407B and the dichroic mirror 407G may be set so that the following expression (2) is satisfied.
t1 = L / (2sinθ _G ) (2)

On the other hand, LED chips R light emitted from the 400R is incident on the reflective optical system 402 at an incidence angle 45 °, travels parallel transparent member 404 at a refraction angle theta _R after passing through the dichroic mirror 407B. If the refractive indexes of the parallel transparent members 404 and 405 regarding the R light wavelength are n _R , the refraction angle θ _R is given by the following equation (3).
sinθ _R = 1 / (√2 · n _R ) (3)

The R light incident on the parallel transparent member 404 passes through the dichroic mirror 407G, travels in the parallel transparent member 405, and is totally reflected by the total reflection mirror 408. Further, the R light totally reflected by the total reflection mirror 408 is transmitted again through the dichroic mirror 407G, travels in the parallel transparent member 404, passes through the dichroic mirror 407B, and is incident on the B light (= reflection position). The light is emitted from the same position at an angle of 45 degrees. In order for the R light to be emitted from the same position as the incident position of the B light, the interval t between the dichroic mirror 407B and the reflection mirror 408 may be set so that the following expression (4) is satisfied.
t = L / sinθ _R (4)

  By setting the reflective optical system 402 as in the above formulas (2) and (4), B light and G light emitted from a set of LED chips 400B, 400G, and 400R arranged in the vertical direction of FIG. When the R light and the R light are emitted from the reflection optical system 402, their optical axes are aligned on the same axis (see FIG. 5). These R light, G light, and B light are perpendicularly incident on the incident surface 410 of the light guide panel 41 as shown in FIG.

  The light guide panel 41 is formed of a transparent acrylic resin or the like, and has a wedge-shaped cross section whose thickness decreases as the distance from the incident surface 410 increases. In other words, the exit surface 411 is parallel to the document, but the back surface 412 is inclined downward to the left in the figure. A plurality of fine recesses 412a are formed on the back surface 412 over the entire region. These concave portions 412a are provided for reflecting and diffusing the R, G, and B light incident from the incident surface 410, and the distribution density of the concave portions 412a is such that the emitted light is uniform. It gets denser as you move away from it.

  The R light, G light, and B light incident from the incident surface 410 are reflected and diffused by the concave portion 412a, and emitted from the emission surface 411 to the document 30 (see FIG. 1). As described above, the side surface and the back surface 412 except the incident surface 410 of the light guide panel 41 are surrounded by the white reflecting member 413, and light leaking from these surfaces is incident on the light guide panel 41 again. To improve efficiency.

  As described above, in the present embodiment, the respective optical axes of the R light, the G light, and the B light are made to coincide with each other and enter the light guide panel 41 by the reflection optical system 402, so that the light is reflected and diffused. The incident conditions (incident position and incident direction) of the R light, G light, and B light with respect to the recess 412a are the same. The action of the reflection optical system 402 that aligns the optical axes of the three color lights into one works for each set shown in FIG. As a result, the occurrence of color unevenness can be prevented and uniform illumination light can be obtained.

  On the other hand, in the conventional apparatus, as shown in FIG. 6, since the LED substrate 401 is disposed so as to face the incident surface 410 of the light guide panel 41, the G light emitted from the LED chip 400G is incident on the incident surface 410. The B light emitted from the LED chip 400B enters a region near the upper end of the incident surface 410, and conversely, the R light emitted from the LED chip 400R is close to the lower end of the incident surface 410. It will enter the region. As described above, when the incident positions of the R light, the G light, and the B light are vertically different, the optical paths from the incident positions of the R, G, and B lights to the concave portions 412a are different for each color light. As a result, each of the R, G, and B light reflected and diffused by the concave portions 412a is different, and uneven illumination light with uneven color is emitted.

  Further, since the LED chips 400B, 400G, and 400R are arranged in the thickness direction of the light guide panel 41 as shown in FIG. 6, there is a drawback that the light guide panel 41 becomes thick. Further, when the LED chips 400B, 400G, and 400R having high luminance are used, the size of each chip increases, so that the light guide panel 41 becomes thicker. Generally, the light guide panel 41 is formed by resin molding. However, as the thickness of the light guide panel 41 increases, high-precision molding becomes difficult.

  However, in the present embodiment, as shown in FIG. 3, since the optical axes of the R light, G light, and B light are aligned and made incident on the light guide panel 41, the optical path from the incident position to each recess 412a is changed. R light, G light, and B light are all the same, and uniform illumination light without color unevenness can be obtained.

  Further, since the optical axes of the respective color lights are aligned, it is not necessary to increase the incident surface 410 in the vertical direction in FIG. 3, and one LED chip 400B, 400G, 400R arranged in three stages as shown in FIG. A thickness corresponding to is sufficient. Therefore, the thickness of the light guide panel 41 can be reduced, and downsizing and cost reduction can be achieved. Further, even if large LED chips 400B, 400G, and 400R are used to increase the luminance, it is not necessary to increase the thickness of the light guide panel 41, and the luminance of the lighting device can be easily increased. .

  In this embodiment, the three color lights of R light, G light, and B light have been described. However, the present invention is also applied to an illumination device that forms mixed color illumination light by entering a plurality of color lights into the light guide panel 41. The invention can be applied. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired. For example, in the above-described embodiment, the illumination device of the image input device has been described as an example. However, the present invention is not limited to the image input device, and can be applied to a backlight illumination device of a liquid crystal display device.

  In correspondence between the embodiment described above and the elements of the claims, the LED chips 400R, 400G, and 400B constitute a light source, the reflective optical system 402 constitutes an optical system, and the reading sensor 42 constitutes an imaging means.

It is a figure which shows one Embodiment of the image input device using the illuminating device by this invention. It is a perspective view which shows the light source part 40 and the light guide panel 41. FIG. It is AA sectional drawing of FIG. It is a top view of LED board 401. FIG. It is a figure explaining the effect | action of the reflective optical system. FIG. 4 is a diagram showing a case where an LED substrate 401 is disposed opposite to an incident surface 410 of a light guide panel 41.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image input device 2 Main body part 3 Adapter part 4 Reading optical system 30 Original 40 Light source part 41 Light guide panel 42 Reading sensor 400R, 400G, 400B LED chip 401 LED board 402 Reflecting optical system 404,405 Parallel transparent member 407B, 407G Dichroic Mirror 408 Total reflection mirror 410 Incident surface 411 Output surface 412 Back surface 412a Concave portion

Claims (4)

In the illumination device that performs surface illumination by sequentially or simultaneously entering a plurality of color lights on the side surface of the light guide panel and emitting illumination light formed by the color light from the exit surface of the light guide panel,
A light source that respectively emits the plurality of colored lights having different optical axes;
An illumination apparatus comprising: an optical system that causes each of the plurality of color lights emitted from the light sources to enter the side surfaces of the light guide panel with their optical axes aligned on the same axis. The lighting device according to claim 1.
The light sources emit first, second and third color lights, respectively;
The optical system is disposed in parallel with the first dichroic mirror that reflects the first color light and aligns on the same axis, the first dichroic mirror at a first predetermined interval, and the second dichroic mirror. A second dichroic mirror that reflects colored light and aligns on the same axis; and a first dichroic mirror that is arranged in parallel at a second predetermined interval to reflect the third colored light and that are on the same axis. And a reflection mirror aligned with the illumination device. The lighting device according to claim 1 or 2,
An illumination apparatus comprising a plurality of sets of the light sources that respectively emit the plurality of colored lights. The lighting device according to any one of claims 1 to 3,
An image input apparatus comprising: an imaging unit configured to detect light from a document illuminated by the illumination device and capture an image of the document.

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