JPH0591255A - Picture input device - Google Patents

Abstract

PURPOSE:To obtain the picture input device employing a lighting device in which a shadow of a color hardly takes place even when a picture having a step difference is read. CONSTITUTION:A lighting device comprising a cathode 4 emitting thermoelectrons into an enclosed vacuum cavity through heating, an anode 7 applying a voltage to the cathode 4, and a phosphor 8 coated closely to the anode 7 and emitting at least one kind of luminous color or more is fitted to part of a light guide member. An opening 5 is formed to the other part of the light guide member to form a light emission face.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an image scanner used when reading an image into a computer,
The present invention relates to an image input device such as a digital copying machine and a facsimile.

[0002]

2. Description of the Related Art An image input device generally comprises an illumination device for illuminating an input image, an image forming system such as a lens, and a photoelectric conversion element. Image scanners, digital copiers, fax machines, etc. have the same components necessary for scanning, 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 reduction system lens of about 1: 7 as an image forming system, and a one-dimensional array CCD as a photoelectric conversion element. Color separation methods for reading a color image mainly include a color separation method using a light source and a color separation method using a color filter. The former is a method of sequentially irradiating an image using three three-primary-color fluorescent lamps to perform color separation, and is known as the cheapest method for realizing a color correction function.

[0003]

However, in the conventional method, the diameter of each fluorescent lamp is usually 5 to 15 mm.
Therefore, it was difficult to irradiate the image from the same direction due to the spatial limitation of the three fluorescent lamps. As a result, when reading an image such as a cut-and-pasted image having a step difference or an image in which the inclination of the image such as an opening in a book changes abruptly, a shadow of a color that does not exist actually occurs.

Therefore, the present invention solves such a problem, and an object of the present invention is to provide an image input device using an illuminating device in which a color shadow is less likely to occur even when reading an image having a step. To provide.

[0005]

In order to solve the above-mentioned problems, the present invention provides a cathode which emits thermoelectrons by heating in a closed vacuum cavity, and an anode which applies a voltage to the cathode. It is characterized in that it is provided with an illuminating device made of a fluorescent substance which is in close contact with the anode and is applied, the illuminating device being attached to a part of the light guide member, and the other part being a light emitting surface.

[0006]

According to the above construction of the present invention, the thermoelectrons emitted from the heated cathode are accelerated by the voltage applied between the cathode and the anode and then enter the phosphor. The electrons excite the phosphor to emit visible light. This light passes through the light guide member and is collected and emitted on the light emitting surface.

[0007]

Embodiments will be described in detail below with reference to the drawings. FIG. 1 is a front view of a lighting device showing a first embodiment according to the present invention. First, the structure of the arc tube 1 will be described. In FIG. 1, a phosphor 8 is formed inside the opening 5 of the glass tube 2. Further, a conductive thin film such as aluminum is vacuum-deposited on it to form an anode 7. The cathode 4 is projected from the electrode base 6 toward the anode 7. The cathode 4 is a thin wire made of, for example, tungsten and having a diameter of 5 to 15 microns, and its tip 9 is covered with an electron emitting substance 9 such as LaBb. In addition, a grid 3 was installed between the cathode 4 and the anode 7 in order to control the flow of electrons from the cathode 4 to the anode 7. The inside of the arc tube 1 is evacuated to a vacuum degree of 10 ⁻³ to 10 ⁻⁸ Torr and then sealed by an electrode base 6 to form a vacuum cavity. The electrodes 4a and 4b of the electrode base 6 are connected to each other, and a voltage can be applied from the outside. 7-a is connected to the anode 7 and 3-a is connected to the grid.

Next, the operation until light emission will be described step by step. FIG. 2 is a lighting circuit diagram of the first embodiment according to the present invention. When power is supplied to the cathode 4 by the power source Ea in the circuit of FIG. 2, the cathode 4 heated by Joule heat is
The electron emitting substance 9 applied to the tip is heated to 400 to 800 degrees. When the switch S is closed and the voltage of the power source Eb is applied to the anode 7, thermoelectrons are emitted from the electron emitting material 9 toward the anode 7. Since the inside of the arc tube 1 is maintained at a vacuum degree of 10 ⁻³ to 10 ⁻⁸ Torr as described above, the thermoelectrons are accelerated toward the anode 7 without being scattered. Then, the accelerated thermoelectrons penetrate through the anode 7 and hit the phosphor 8 to excite it, thereby emitting visible light. The voltage of the power source Eb needs to be 5 to 30 kV in order to increase the luminous efficiency, but optimally about 10 kV.

The phosphor 8 can be selected according to the emission color used. Specific examples of phosphors include Y ₂ O ₂ S: Eu as a red phosphor, ZnS: Ag as a blue phosphor, and ZnS: C as a green phosphor.
u, Al, etc. are mentioned. When white light is required, it can be realized by mixing and applying these in consideration of the emission luminance balance of the red, blue and green phosphors. Further, here, as the example of the phosphor layer 8, a zinc sulfide-based or rare earth-based phosphor for high voltage application is used, but a low voltage is applied by using a zinc oxide-based phosphor for low voltage light emission. The same result can be obtained by emitting light.

The illuminating device according to the present invention uses light emission by exciting a phosphor with an electron beam. (1) Instantaneous light emission is possible.

(2) There is almost no fluctuation in the light quantity due to the ambient temperature.

(3) The amount of light increases in proportion to the input power.

(4) It is possible to perform pulse lighting in a few microseconds.

(Not possible with halogen lamps) (5) Luminous efficiency is as high as about 80 lm / W.

It has the following advantages.

Here, the function of the light guide member will be described. When the thermoelectrons emitted from the cathode 4 hit the anode 7, they emit light. The light is emitted in all directions, but since the anode 7 made of an aluminum thin film is formed inside the phosphor, the light is reflected toward the opening 5 by the anode 7. As a result, light comes out from the opening 5 which is the light guide member. That is, no light is emitted from other than the opening 5.

FIG. 3 is a perspective view of a usage example of the illuminating device according to the first embodiment of the present invention in FIG. 1, and FIG. 4 is a front view seen from the direction A in FIG. In the illuminating device shown in FIG. 1, by changing the phosphor 8, a red illuminating device 1-R, a blue illuminating device 1-B, and a green illuminating device 1-G are produced, and the dichroic mirror 10 shown in FIG. The opening 5 of each lighting device is attached. Then, the glass rod 11, which is a light guide member, is attached to the remaining one surface. Here, the glass rod 11 will be described. As shown in FIG. 3, a reflecting plate 13 is attached to the end surface facing the lighting device, and the side opposite to one side of the longitudinal direction of the cylindrical glass on which light is irradiated has a width of 0.1 to 10 mm and a thickness of 0.1. A white stripe 12 having a size of about 1 μm to 1 mm is formed. Here, the glass rod 11
Has the function of converting the light emitted from the lighting device, which can be regarded as a point light source, into the light which can be regarded as a line light source. Further, the white stripe 12 has a function of diffusing the light totally reflected in the glass rod 11 when the light hits the white stripe 12 and emitting the light toward the irradiation surface. The material of the rod is glass such as quartz glass, transparent ceramics, colored or colorless transparent plastic such as silicone resin, and the material of the white stripe 12 is barium sulfate, oxides of titanium or magnesium, and the like. Be done.
When the glass rod 11 is attached to the dichroic mirror 10, if the dichroic mirror 10 and the glass rod 11 are joined as shown in FIG. 4, a gap 14 is created and light escapes to the outside. Therefore, an aluminum thin film is formed in the gap 14. So that the light does not escape.

According to this embodiment, red,
There is an advantage that light of three types, blue and green, can be emitted by switching.

The illuminating device shown in FIG. 3 can be used as a light source of a liquid crystal television projector by placing liquid crystal in the joint portion 15. That is, color display can be performed by irradiating from the back of one monochrome liquid crystal panel with the lighting device according to the present embodiment and performing high-speed lighting of the three primary colors and switching of the liquid crystal panel in chronological order.

FIG. 5 is a perspective view showing an embodiment of an image input device using the illuminating device according to the present invention, and FIG. 6 is a sectional view of the vicinity of the carriage 18 shown in FIG. Less than,
The operation for reading an image will be described with reference to FIG. An illuminating device 21 equivalent to the above-described embodiment of the present invention is mounted in the carriage 18, and a part of the row L of the image 17 placed on the glass table 16 is irradiated via the light guide member.
Then, the reflected and scattered light is imaged through the mirror 22 by the reduction lens 23 onto the CCD 24 which is a photoelectric conversion element. The CCD 24 is a one-dimensional image sensor, and one line of image data can be read by an electronic circuit (not shown). The carriage 18 to which the illumination device 21, the mirror 22, the reduction lens 23, and the CCD 24 are fixed is moved in the direction of the arrow in FIG. 5 by the drive device 20 via the timing belt 19 by a distance corresponding to the reading resolution. By repeating the above operation, the entire surface of the image 17 can be read.

By using the illuminating device according to the present invention, the starting property of the light source is excellent, and a stable light amount is obtained at the same time as starting, so that it is possible to obtain an output faithful to the density value of the image to be read, and to eliminate the step difference. The problem that a colored shadow is generated in the step portion when reading the image having the same is eliminated, and it becomes possible to faithfully read the image having the unevenness.

[0022]

As described above, according to the present invention, there is an effect that it is possible to obtain an illuminating device whose light quantity is stable regardless of the ambient temperature. Further, the image input device using the illuminating device according to the present invention has an effect that the starting property and the light amount stability are good regardless of the operating environment temperature, the performance is high, and the image having unevenness can be faithfully read. ..

[Brief description of drawings]

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

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

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

4 is a front view seen from the direction of arrow A in FIG.

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

6 is a cross-sectional view of a portion near a carriage 17 shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide member 8 Cathode 9 Electron emission substance 10 Phosphor 11 Anode 20 Lighting device

Claims (2)

[Claims] 1. A lighting device comprising a cathode that emits thermoelectrons when heated, an anode that applies a voltage to the cathode, and a phosphor that is in close contact with and applied to the anode, in a sealed vacuum cavity. In the image input device used, the illuminating device is attached to a part of a light guide member, and the other part of the light guide member serves as a light emitting surface. 2. The image input device according to claim 1, wherein at least two or more kinds of phosphors having different emission colors are applied.