JPH04248246A - Lighting device and image input device - Google Patents

Abstract

PURPOSE:To provide a lighting device which is excellent in starting characteristics, temperature characteristics, and luminous energy stability, and is capable of reading the irregularities of an image. CONSTITUTION:A fluorescent film is formed on the surface of a glass bar 4 by coating the surface with red fluorescent material 6-R, blue fluorescent material 6-B and green fluorescent material 6-G, and an opening section 10 is provided on the bar 4. On the surface of the fluorescent film an aluminum thin film acting as an anode 5 is formed. Grids 7-R, 7-B and 7-G are provided above the respective fluorescent materials between a cathode 2 coated with electron radiating material 3 and the anode 5, so that current flow is controlled. A convex lens 8 is provided on a luminous tube in order that light coming out of the opening section 10 is not divergent, and the part other than the convex lens 8 is formed of aluminum thin film 9.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an image scanner mainly used for reading images into a computer;
The present invention relates to lighting devices for image input devices such as digital copying machines and facsimiles.

0002

2. Description of the Related Art An image input device generally includes an illumination device for illuminating an input image, an imaging system such as a lens, and a photoelectric conversion element. Image scanners, digital copiers, fax machines, etc. all require the same components for reading, and the following discussion will focus on image scanners. Generally, an image scanner uses a line light source such as a mercury fluorescent lamp or a line halogen lamp as an illumination device, a lens with a reduction ratio of about 1:7 as an image forming element, and a one-dimensionally arranged CCD as a photoelectric conversion element. Color separation methods for reading color images mainly include a color separation method using a light source and a color separation method using a color filter. The former method uses three three-primary-color fluorescent lamps to sequentially illuminate an image and perform color separation, and is known as the cheapest method for realizing a color correction function.

0003

[Problems to be Solved by the Invention] However, in the conventional method, the diameter of each fluorescent lamp is usually 5 to 15 m.
m, it was difficult to irradiate images from the same direction due to spatial arrangement restrictions of the three fluorescent lamps. As a result, when reading an image with steps such as a cut-and-paste photograph or an image in which the slope of the image changes suddenly, such as an opening in a book, the method has the disadvantage of producing shadows of non-existent colors.

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and its purpose is to provide an image input device using an illumination device that is less likely to cause color shadows even when reading images with steps. It is about providing.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the lighting device of the present invention includes a cathode that emits thermoelectrons when heated in a sealed vacuum cavity, and a voltage applied to the cathode. It is characterized by consisting of an anode and a phosphor coated in close contact with the anode. Further, an image input device according to the present invention is characterized in that it includes the lighting device.

[0006]

According to the above structure of the present invention, thermionic electrons emitted from the heated cathode are accelerated by the voltage applied between the cathode and the anode, and then rush into the phosphor. These electrons excite the phosphor to emit visible light. This light passes through the interior of the light guide member, is collected on the light emitting surface, and is emitted.

[0007]

Embodiments will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of a first embodiment according to the invention. glass rod 4
Three primary color phosphors, red phosphor 6-R, blue phosphor 6-B, and green phosphor 6-G, are coated so as to form an opening 10 through which light can emit light, and a phosphor film is formed. is forming. Then, an aluminum thin film is formed as an anode 5 on the surface of the phosphor film. An example of a method for forming the phosphor films 6-R, 6-G, and 6-B is electrophoresis. Cathode 2
Grids 7-R, 7-G, and 7-B are arranged between the cathode 2 and the anode 5 above the respective phosphors to control the flow of electrons from the cathode 2 to the anode 5. The cathode 2 is a curved line made of, for example, tungsten and has a diameter of 5 to 15 μm, and its circumference is coated with an electron emitting material 3 such as LaBb. Moreover, the inside of the arc tube 1 has a degree of vacuum of 10-3 to 10-7To.
Exhaust to rr. The light emitted from the phosphors 6-R, 6-G, and 6-B is collected by the central glass rod 4, and the light is concentrated and emitted from the opening 10.

Next, the operation up to emitting light will be explained step by step. FIG. 2 is a circuit diagram of the first embodiment. The lighting procedure will be explained with reference to FIG. When power is supplied to the cathode 2 by the power supply e1 in the circuit of FIG.
Heat to 600°C. At this time, since a voltage is applied between the cathode 2 and the anode 5 by the power source e3, thermoelectrons are emitted from the electron emitting material 3 toward the anode 5. The inside of the arc tube 1 is 10-3 to 10-7To as described above.
Since the degree of vacuum is maintained at rr, the above-mentioned thermoelectrons are accelerated toward the anode 5 without being scattered. These accelerated thermoelectrons then pass through the anode 5 and pass through the phosphors 6-R, 6-
When it hits G,6-B and excites it, visible light is emitted. The voltage of power supply e3 is 5 to 3 to increase luminous efficiency.
0 kV is required, but optimally it is about 10 kV.

[0009] Here, a case where the phosphor 6-R emits light will be explained as an example. First, the switch transistor 13-d is turned on by the lighting control means 11. At this time, the voltage of the power source e2 is applied to the grid 7-R. Then, an electric field is generated between the cathode 2 and the grid 7-R, and the electron emitting material 3 accelerates electrons toward the grid 7-R. Here, the grid 7-R has a lattice shape, and most of the thermoelectrons pass through and are further accelerated toward the anode 5. The thermoelectrons then reach the anode 5 and strike the phosphor 6-R, exciting it and emitting visible light. Other phosphor 6-
The light emission of lights G and 6-B can be similarly controlled by the lighting control means 11. By the way, the resistors 12-b, 12-c,
12-d are switch transistors 13-b and 1, respectively.
3-c, 13-d controls the operating current during operation.

The function of the glass rod 4, which is a light guide member, will be explained. Thermionic electrons emitted from the cathode 2 excite the phosphor and emit light. The light is emitted in all directions, but since the outside of the phosphor forms an anode 5 made of a thin aluminum film, the light is reflected toward the center of the glass rod 4 by the anode 5. Further, although not shown here, each end of the glass rod 4 is provided with a reflecting plate, and light emitted toward both ends of the glass rod is also reflected by the reflecting plate. In this way, the light is repeatedly reflected and scattered within the glass rod 4. As a result, light comes out from the opening 10 which is the light emitting surface of the glass rod 4 which is the light guiding member. In other words, no light is emitted from any other than this opening 10. At this time, since the light emitted from the opening 10 is likely to be scattered within the arc tube 1, the light emitted from the opening 10 is easily scattered.
A convex lens 8 is installed above the opening 10 so that the light converges as shown in FIG.

[0011] The phosphors 6-R, 6-G, and 6-B must be selected depending on the color of emitted light to be used. To give a specific example of a phosphor, Y2O2S:Eu is used as a red phosphor 6-R.
3+, ZnS:Ag as the blue phosphor 6-B, and ZnS:Cu, Al, etc. as the green phosphor 6-G. If white light is required, it can be achieved by mixing and coating the red, blue, and green phosphors in consideration of the luminance balance.

In this embodiment, a zinc sulfide-based or rare earth-based phosphor for high-voltage application was used for the phosphor layer 6, but a zinc oxide-based phosphor for low-voltage light emission was used to apply a low voltage. The same result can be obtained even if the light is emitted by

Furthermore, this embodiment has the advantage that three types of light, red, blue, and green, can be selectively emitted from the same opening.

FIG. 3 is a perspective view of a second embodiment of the illumination device according to the present invention. A glass rod 31, which is a light guiding member of the lighting device, is attached and used. As shown in the figure, a reflecting plate 14 is attached to the end face facing the lighting device. Also, one side of the cylindrical glass in the long axis direction has a width of 2~
A white stripe 15 of about 3 mm is formed and JP-A-60-1188
Optical components such as those shown in Japanese Patent No. 06 are used.

FIG. 4 is a cross-sectional view of the third embodiment. In the figure, a cavity 20 formed by an upper lid 19 made of transparent glass and a glass frame 17 has a vacuum degree of 10-3 to 10-1.
It is evacuated to 7 Torr. Further, in the cavity 20, a cathode 2 is formed by stretching a piece of tungsten coated with an electron emitting material 3 in an S-shape. glass frame 17
The inside of the opening 30 is coated with phosphors 32-R, 32-G, and 32-B that can emit light in three primary colors when excited by an electron beam, and a thin aluminum film is vacuum-deposited on the surface. This forms the anode 5. The grid 16-a is always at the same potential or negative potential as the cathode 2, and has the function of not directing the thermoelectrons emitted from the electron emitting material 3 in a direction other than the direction in which the phosphor is coated. There is. The grids 16-b, 16-c, and 16-d serve to control the flow of thermoelectrons similarly to the grids 7-R, 7-G, and 7-B in the first embodiment, and are available in three types. phosphor 32
-R, 32-G, and 32-B light emission can be switched. Furthermore, since aluminum is vapor-deposited inside the opening 30 to form the anode 5, light only comes out from the opening 30.

Furthermore, the illumination device shown in FIG. 3 can be used as a light source for a liquid crystal television projector by placing a liquid crystal in the joint 18. That is, color display is possible by irradiating one monochrome liquid crystal panel from behind with the illumination device according to the present embodiment and synchronously performing high-speed lighting of the three primary colors and switching of the liquid crystal panel in chronological order.

By using the illumination device according to the present invention, the light source has excellent starting performance, and a stable amount of light can be obtained at the same time as starting, making it possible to obtain an output that is faithful to the density value of the image to be read, and eliminating steps. This eliminates the problem of colored shadows appearing on stepped areas when loading images with uneven surfaces, and it becomes possible to faithfully load images with uneven surfaces.

FIG. 5 is a perspective view showing an embodiment of an image input device using the illumination device according to the present invention, and FIG. 6 is a sectional view of the vicinity of a portion of the carriage 23 shown in FIG.

The operation for reading an image will be explained below with reference to FIG. An illumination device 26 similar to the embodiment according to the present invention described above is mounted inside the carriage 23, and illuminates a part of the row L of the image 22 placed on the glass stand 21 through a light guide member. The reflected and scattered light is then imaged by a reduction lens 28 via a mirror 27 onto a CCD 29 which is a photoelectric conversion element. The CCD 29 is a one-dimensional image sensor, and can read one line of image data using an electronic circuit (not shown). Illumination device 26, mirror 27, reduction lens 28, CCD 29
A carriage 23 to which a set of are fixed is moved in the direction of the arrow in FIG. 5 via a timing belt 24 by a driving device 25 by a distance corresponding to the reading resolution. By repeating the above operations, the entire surface of the image 22 can be read.

[0020]

As described above, the present invention has the effect that it is possible to obtain a lighting device whose amount of light is stable regardless of the environmental temperature. Furthermore, the image input device using the illumination device according to the present invention has good start-up performance and light intensity stability regardless of the operating environment temperature, has high performance, and has the effect of being able to faithfully read even uneven images. It is.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of a lighting device according to the present invention.

FIG. 2 is a lighting circuit diagram of a first embodiment of the lighting device according to the present invention.

FIG. 3 is a perspective view showing a second embodiment of the lighting device according to the present invention.

FIG. 4 is a sectional view showing a third embodiment of the lighting device according to the present invention.

FIG. 5 is a perspective view showing an image input device according to the present invention.

FIG. 6 is a sectional view showing an image input device according to the present invention.

[Explanation of symbols]

1 Arc tube 2 Cathode 3 Electron emitting material 5 Anode 6. Phosphor 26. Lighting equipment 27 Mirror 28 Reduction lens 29 Photoelectric conversion element

Claims (3)

[Claims] Claim 1: A lighting device consisting of a cathode that emits thermoelectrons when heated, an anode that applies a voltage to the cathode, and a phosphor coated in close contact with the anode, in a sealed vacuum cavity. A lighting device, characterized in that a phosphor is formed on or near a part of the light guide member, and the other part of the light guide member is used as a light emitting surface. 2. The lighting device according to claim 1, wherein at least two types of phosphors emitting different colors are coated. 3. An image input device comprising the lighting device according to claim 1.