JPH08307608A - Transparent original lighting device - Google Patents

Abstract

PURPOSE: To attain reading of a transparent original with a small size and light weight by using a transparent light transmission flat plate, providing a reflection sheet in parallel with the light transmission plate at the rear side of the light transmission plate, and providing red, green and blue linear light sources to the end of the light transmission plate along the end face of the light transmission plate in parallel. CONSTITUTION: The light made incident onto a light transmission plate 1 is propagated while repeating reflection between a rear side 1a being an upper side of the light transmission plate 1 and a lower side 1b. Furthermore, the light reaching the rear side 1a is reflected partly to be returned to the inside of the light transmission plate 1 and transmitted partly through the rear side 1a and reaches a reflection sheet 2. The light reaching the reflection sheet 2 is diffused and reflected in the surface of the reflection sheet 2, part of the light reflected in the reflection sheet 2 transmits through the light transmission plate 1 and reaches a diffusion sheet 7 and is transmitted through the diffusion sheet 7 and emitted from the lower side of the light transmission plate 1. Thus, when a red light 3 being a linear light source is lighted, the red light is led to the light transmission plate 1 and emitted from the entire face of the sheet 7. The behavior of the light is similar also in the case of green and blue lights. Thus, an entire original 8 placed to a lower side is lighted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document illuminating device used in an image reading device that captures an image of a transparent document as electronic image data into a computer, and color separation is performed from the image of the transparent document using a reading head equipped with a line sensor. The present invention relates to a document illuminating device that illuminates a transparent document to obtain an image.

[0002]

2. Description of the Related Art Today, not only is it possible to take an image of a reflective original document into a computer for image processing, but also to take an image of a transparent original document such as film into the computer. When the image of the transparent original is read by the image reading device, a white surface light source is arranged on, for example, the upper surface of the transparent original, a reading head having a line sensor is arranged below the transparent original, and the reading head is sequentially moved. When reading a color image, the reading head is provided with a color separation filter to read the red image data,
Three types of image data, green image data and blue image data, are to be read.

Further, when reading a color image, an illumination block which moves in synchronization with a reading head arranged below the transparent original is arranged above the transparent original, and a red light, a green light and a blue light are arranged in this illumination block. A red light, green image data, and blue image data is read by providing a light and moving at least the position of the document in synchronization with the illumination block and the reading head, and sequentially lighting the red light, green light, and blue light. Some are designed to be read by the head.

[0004]

As described above, in the image reading apparatus in which the reading head is provided with the color separation filter, it is difficult to switch the color separation filter mechanically at high speed, and therefore the image reading time is reduced. It is difficult to shorten the length, and the reading head becomes large, which makes the reading device large.

Further, in the case where the color separation filter is fixed and the line sensor for the red image, the line sensor for the green image and the line sensor for the blue image are provided, the number of line sensors becomes plural, and the image reading device is It had the drawback of being expensive. An image reading apparatus that uses an illumination block that moves in synchronization with the reading head requires an expensive and complicated mechanism to move the illumination apparatus, and the illumination apparatus becomes large in size to accommodate this mechanism. As a result, the weight of the image reading apparatus increases, and the image reading apparatus becomes large.

The present invention provides an illuminating device which eliminates such drawbacks, can read a color image, and can be a small-sized, lightweight and low-cost transparent original reading device.

[0007]

According to the present invention, a transparent flat light guide plate is used, a reflection sheet is provided on the back side of the light guide plate in parallel with the light guide plate, and red, green, and blue are provided at the ends of the light guide plate. The linear light sources are provided in parallel along the end surface of the light guide plate. Further, the illuminance distribution correction pattern may be printed on at least one of the back surface of the light guide plate and the front surface of the reflection sheet.

Further, a transparent sheet on which an illuminance distribution correction pattern is printed may be arranged between the light guide plate and the reflection sheet. As the illuminance distribution correction pattern, a plurality of patterns may be used as a red light correction pattern, a green light correction pattern, and a blue light correction pattern.

[0009]

[Operation] According to the present invention, since red, green, and blue linear light sources are arranged at the ends of the light guide plate, red light, green light, and blue light can be incident on the light guide plate. Since the reflection sheet is provided on the back surface of the, the light guide plate can be used as the red, green, and blue surface light sources.

Therefore, by sequentially turning on the red light, the green light, and the blue light, the transparent original can be illuminated with red, green, and blue, and it is not necessary to provide a color separation filter on the reading apparatus main body. Since this illumination is a surface light source, it is not necessary to provide a mechanism for moving it like an illumination block. Further, by printing the illuminance distribution correction pattern on the back surface of the light guide plate or the surface of the reflection sheet, it is possible to average the brightness of each part of the light guide plate and reduce the uneven illumination of the original.

Further, even when a transparent film on which the illuminance distribution correction pattern is printed is arranged between the light guide plate and the reflection sheet, it is possible to eliminate the illumination unevenness of the original and to insert the film on which the predetermined pattern is printed. Therefore, it is possible to easily mass-produce the illumination device having the illuminance distribution correction pattern. If the illuminance distribution correction pattern is a plurality of patterns for red light, green light, and blue light, the optimum illuminance distribution correction for each color is applied to the linear light source arranged at the end of the light guide plate. You can

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first embodiment of the transmissive original illuminating device according to the present invention, as shown in FIG. 1, three fluorescent tubes 3, 4, 3 are arranged at both ends of the light guide plate 1, respectively. Reflective sheet 2 on top of
A diffusion sheet 7 is provided on the lower surface, and a reflecting mirror 6 is provided so as to cover the fluorescent tubes 3, 4, and 5.

The light guide plate 1 is made of glass or synthetic resin having high transparency, and has a rectangular flat plate shape, and each surface is an extremely smooth flat surface. Also, of the four sides of the rectangle of the light guide plate 1, three fluorescent tubes 3, 4 are provided in parallel with the end faces of the two sides facing each other, one of which is a red lamp.
3, one of which is a green light 4 and the other one is a blue light 5, and as shown in FIGS. 1 and 2, they are arranged so as to be surrounded by a reflecting mirror 6.

FIG. 2 is a sectional view of the lighting device shown in FIG. Then, a reflection sheet 2 is provided on the upper surface of the light guide plate 1 in parallel with the light guide plate 1, and the reflection sheet 2 is white.
Further, a diffusion sheet 7 having a property of diffusing light is provided on the lower surface of the light guide plate 1 in parallel with the light guide plate 1. Therefore, one of the red, green, and blue lamps 3, 5
When 3, 4 and 5 are turned on, the light is partly directly from the end of the light guide plate 1 to the inside of the light guide plate 1 and partly reflected by the reflecting mirror 6 to the end of the light guide plate 1. The light is incident on the inside of the light guide plate 1.

The light incident on the light guide plate 1 is
The surface 1b, which is the upper surface, and the surface 1b, which is the lower surface, are repeatedly reflected and proceed. Further, of the light reaching the back surface 1a, a part is reflected back to the inside of the light guide plate 1, a part is transmitted through the back surface 1a to reach the reflection sheet 2, and the light reaching the reflection sheet 2 is reflected. A part of the light reflected by the surface of the sheet 2 is diffused and reflected, and a part of the light reflected by the reflection sheet 2 passes through the light guide plate 1 to reach the diffusion sheet 7, and then passes through the diffusion sheet 7 and is radiated from the lower surface of the light guide plate 1. Will be.

Therefore, when the red light 3 which is a linear light source is turned on, the red light is guided to the light guide plate 1 and emitted from the entire surface of the diffusion sheet 7 to the lower side of the lighting device. When the green light 4 which is a linear light source is turned on, green light is emitted from the entire surface of the diffusion sheet 7. When the blue light 5 which is a linear light source is turned on, blue light is emitted from the entire surface of the diffusion sheet 7. In this way, the transparent original 8 placed below the illumination device
The entire area can be illuminated.

The three fluorescent tubes 3 used as the linear light source,
The spectral emission characteristics of the red lamp 3 at 4 and 5 have a peak in the vicinity of about 660 nm as shown in FIG. 3, and the spectral emission characteristic of the green lamp 4 is at about 530 nm as shown in FIG.
As shown in FIG. 5, the blue lamp 5 has a peak in the vicinity of about 450 nm, as shown in FIG.

As described above, the red light 3, the green light 4, and the blue light 5, which are three linear light sources, are provided at both ends of the light guide plate 1, and the red light is provided.
By sequentially illuminating the green light 4, the green light 4, and the blue light 5, the entire surface of the transparent original 8 can be illuminated by sequentially emitting red light, green light, and blue light from the entire surface of the diffusion sheet 7. Red image data by the reading head placed below,
It is possible to obtain green image data and blue image data.

By the way, the uniform thickness of the light guide plate 1
Alternatively, when a reflection sheet 2 having a constant reflection characteristic and a diffusion sheet 7 having a constant diffusion characteristic are used, when a linear light source is arranged at both ends of the light guide plate 1 to turn on the light, the diffusion sheet 7 The illuminance due to the light emitted from the red light 3 or green light
The light guide plate 1 provided with the fluorescent tubes 3, 4, such as 4 is large near the end and slightly lower in the center, and when illuminating the transparent original 8, the illuminance in the central portion of the original is the lowest. . Further, the illuminance distribution for each color also differs depending on the arrangement of the red light 3, the green light 4, and the blue light 5, as shown in FIG.

Therefore, as a second embodiment of the present invention, an illuminance distribution correction pattern is printed on the back surface 1a of the light guide plate 1, and the light reflected by the back surface 1a of the light guide plate 1 is printed by this illuminance distribution correction pattern. A part of the light is diffused and reflected, and the amount of light transmitted through the surface 1b of the light guide plate 1 and the diffusion sheet 7 is adjusted. In this illuminance distribution correction pattern, a dot pattern is formed on the back surface 1a of the light guide plate 1 using an ink that easily diffuses and reflects light.
The central portion is densely arranged, and the rough dots are provided near both ends where the fluorescent tubes 3, 4, and 5 are arranged, so that the light from the back surface 1a of the light guide plate 1 near the central portion is lighted. Is increased to increase the amount of light emitted below the light guide plate 1 near the central portion.

The illuminance distribution correction pattern may be printed on the surface of the reflection sheet 2 provided above the light guide plate 1. Further, a transparent sheet on which the illuminance distribution correction pattern is printed is reflected from the light guide plate 1. It may be provided between the seat 2 and the seat 2. When the transparent sheet on which the illuminance distribution correction pattern is printed is inserted and used, a predetermined dot pattern is separately printed on the transparent sheet.
It is easier to print the dot pattern than it is to print on, and the transparent sheet on which the dot pattern is printed is inserted into the back surface 1a of the light guide plate 1, so it is easy to manufacture an illumination device with corrected illuminance distribution. Becomes

Further, when the illuminance distribution correction pattern is provided, it is not limited to the case where dots are formed using ink that reflects visible light of all wavelengths substantially uniformly, and the vicinity of about 660 nm shown in FIG. Around 530 nm shown in
Each of the inks shown in FIG. 5 having a high reflectance at a wavelength around 450 nm is used. And as shown in FIG. 7, about 450
The area of the dot formed by the ink that reflects well the light (blue light) in the wavelength range of about nm is the largest in the central portion, and is about 66
The area of the dot of the ink that reflects light with a wavelength near 0 nm (red light) well is increased in the central portion while being smaller than the ink for blue light, and the area of light with a wavelength near 530 nm (green light) is reduced. The area of the well-reflected ink dots may be maximized in the central portion and smaller than the areas of other inks.

As described above, the red light correction pattern, which is the illuminance distribution correction pattern for adjusting the illuminance of the light from the red light 3 according to the wavelength of the light source provided at the end of the light guide plate 1, and the green light 4 A green light correction pattern, which is an illuminance distribution correction pattern for adjusting the illuminance of light, and a blue light correction pattern, which is an illuminance distribution correction pattern for adjusting the illuminance of light from the blue light 5, are formed. The illuminance distribution correction pattern using the red light correction pattern, the green light correction pattern, and the blue light correction pattern can further optimize the illuminance distribution of each color light.

As another embodiment, as shown in FIG. 8, two fluorescent tubes are arranged at the end of the light guide plate 1, and fluorescent tubes having wavelengths having the lowest illuminance among the three primary colors are arranged. Assuming that two fluorescent tubes are provided at each end of the light guide plate 1 and one fluorescent tube that emits light of the other two colors is used at each end of the light guide plate 1. To do. For example, one blue light 5 is provided at each end of the light guide plate 1, and one red light 3 and one green light 4 are provided.
May be arranged at one end of the light guide plate 1.

Thus, by disposing two fluorescent tubes at each end of the light guide plate 1, it is possible to form a surface light source of red light, green light, and blue light by the diffusion sheet 7 and make the lighting device thin. You can In this case, in the illuminance distribution correction pattern, the dots of the ink that well reflect the wavelength of about 450 nm are dense in the center, and the dots of the ink that well reflect the wavelength of about 660 nm and the wavelength of about 530 nm are well defined. The well-reflected ink dots should be dense at the ends farther from the fluorescent tubes and coarser toward the ends closer to the fluorescent tubes.
The correction pattern for the red light and the correction pattern for the green light are dense in opposite directions.

Furthermore, when arranging the fluorescent tubes 3, 4, 5, which are linear light sources, at the ends of the light guide plate 1, the red light 3, the green light 4, and the blue light 5 are dispersed on the three sides of the light guide plate 1, respectively. And place it,
By using one fluorescent tube 3, 4 provided in parallel to the end surface of the light guide plate 1, each lighting device can be made thinner.
Further, when one fluorescent tube 3, 4 is provided at each end of the light guide plate 1, the red lamp 3 and the green lamp 4, which are the fluorescent tubes having high brightness, are provided on the long side of the light guide plate 1 in the light guide plate 1. One blue lamp 5 which is a fluorescent tube with low brightness is provided on each of the two short sides, and one fluorescent tube 3, 4 may be provided on each of the four sides around the light guide plate 1. .

Even when the fluorescent tubes 3, 4 are arranged on the four sides of the light guide plate 1 one by one, the correction pattern for the red lamp and the green lamp are arranged in accordance with the fluorescent tubes 3, 4, 5 of each color. Distribution correction pattern and the illuminance distribution correction pattern in which the blue light correction pattern is formed, the illuminance distribution can be obtained with each color as an optimum condition.

[0028]

The present invention is a transparent original illuminating device in which a reflective sheet is provided on the back surface of a transparent flat plate-shaped light guide plate and red, green, and blue linear light sources are arranged at the ends of the light guide plate. Therefore, by sequentially turning on the red, green, and blue linear light sources, the entire transparent original can be sequentially illuminated with red, green, and blue, and the illumination device can be provided without a mechanical movable portion. It can be small and lightweight. In addition, since the entire transparent original is sequentially illuminated with red, green, and blue, the red image data, the green image data, and the blue image data are read into the image reading device by the reading head using a single line sensor without a filter. It is possible to form color image data with a small and inexpensive image reading device.

Further, in the illumination device in which the illuminance distribution correction pattern is printed on the back surface of the light guide plate or the back surface of the reflection sheet, the illumination of the transparent original can be made uniform, and the image can be read by the image reading device without deteriorating the image quality of the transparent original. it can. Further, the illuminating device in which the transparent film on which the illuminance distribution correction pattern is printed is disposed between the light guide plate and the reflecting sheet, can illuminate the transmissive original evenly, and facilitates the assembling and manufacturing of the illuminating device. be able to.

The illumination device in which the illuminance distribution correction pattern is formed separately for the red light, the green light, and the blue light can irradiate the transparent original with the light of each color in an optimum state, and the image quality is high. The image can be read by the image reading device without damaging the image quality of the transparent original.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a first embodiment of the present invention.

FIG. 3 is a diagram showing a spectral emission characteristic of a red lamp.

FIG. 4 is a diagram showing a spectral emission characteristic of a green lamp.

FIG. 5 is a diagram showing a spectral emission characteristic of a blue lamp.

FIG. 6 is a diagram showing an example of an illuminance distribution characteristic by the lighting device according to the present invention.

FIG. 7 is a diagram showing a characteristic example of an illuminance distribution correction pattern.

FIG. 8 is a diagram showing another embodiment of the lighting device according to the present invention.

[Explanation of symbols]

 1 Light guide plate 1a Light guide plate back surface 1b Light guide plate surface 2 Reflective sheet 3 Red light 4 Green light 5 Blue light 6 Reflecting mirror 7 Diffusion sheet 8 Transparent original

Claims (4)

[Claims] 1. A transparent flat plate-shaped light guide plate, a reflection sheet parallel to the light guide plate on the back side of the light guide plate, and red, green, and blue linear light sources at the ends of the light guide plate. A transparent original illuminating device, characterized in that each of the light guide plates is parallel to each other along an end face of the light guide plate. 2. The transparent original illuminating device according to claim 1, wherein an illuminance distribution correction pattern is printed on at least one of the back surface of the light guide plate and the front surface of the reflection sheet. 3. The transparent original illuminating device according to claim 1, wherein a transparent sheet on which an illuminance distribution correction pattern is printed is arranged between the light guide plate and the reflection sheet. 4. The illuminance distribution correction pattern is a plurality of patterns including a red light correction pattern, a green light correction pattern, and a blue light correction pattern. The transparent original illuminating device described.