JPH0591256A - Picture input device - Google Patents

Abstract

(57) [Summary] [Purpose] Even when reading images with steps
To provide an image input device using an illuminating device in which color shadows are less likely to occur. The lighting device includes a cathode 8 that emits thermoelectrons by heating, an anode 11 that applies a voltage to the cathode 8 and at least two types of coating that are closely attached to the anode 11 in a sealed vacuum cavity. It is composed of the phosphors 10 having different emission colors.

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 m.
Since it is as large as m, it is difficult to irradiate an 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 image input device of the present invention comprises a cathode which emits thermoelectrons upon heating in a closed vacuum cavity, and a voltage applied to the cathode. The illuminating device is made up of an anode to be applied and a phosphor that is applied in close contact with this anode, the phosphor is formed on or near the surface of a part of the light guide member, and the other part of the light guide member is a light emitting surface. It is characterized by

[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. Figure 1
FIG. 3 is a perspective view of an illumination device of an embodiment according to the present invention. The glass rod 1 which is a light guide member of the lighting device is attached and used. Here, the glass rod 1 will be described. As shown in FIG. 1, a reflection plate 2 is attached to an end surface facing the portion A of the illuminating device, and a width of 0.1 to 10 m is provided on one side surface of the cylindrical glass in the major axis direction on the opposite side to be irradiated.
A white stripe 3 having a thickness of m and a thickness of about 0.1 μm to 1 mm is formed. Here, the function of the glass rod 1 is to convert 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 3 has a function of diffusing the light totally reflected in the glass rod 1 when the light hits the white stripe 3 and emitting the light toward the irradiation surface. The material of the rod 1 is glass such as quartz glass, transparent ceramics, colored or colorless transparent plastic such as silicone resin, and the material of the white stripe 3 is barium sulfate, oxides of titanium or magnesium, and the like. And so on.

FIG. 2 shows part A of the embodiment shown in FIG.
FIG. In FIG. 2, the cavity 7 formed by the upper lid 5 made of transparent glass and the glass frame 6 has a vacuum degree of 1
It is evacuated to 0 ^over 3-10 ^over 8 Torr. Inside the opening 24 from which light of the glass frame 6 is emitted, phosphors 10-R, 10-G, 1 capable of emitting light of three primary colors by excitation of an electron beam.
0-B is applied, and an aluminum thin film is vacuum-deposited on the surface thereof to form an anode 11. The cathode 8 is a fine wire made of, for example, tungsten and having a diameter of 5 to 15 μm, and the periphery thereof is covered with an electron emitting substance 9 such as barium oxide.

Next, the operation until light emission will be described step by step.

When electric power is supplied to the cathode 8, the cathode 8 heated by Joule heat heats the electron emitting material 9 applied around it to 400 to 800 ° C. to emit thermoelectrons. At that time, if the potential Vk (= 0 V) of the cathode 8 is constant and the distance between the cathode 8 and the back electrodes 13-a and 13-b is also constant, the thermoelectrons emitted from the cathode 8 are the voltage V _{AD of the} back electrode _. Position vertically. At this time, a voltage higher than the potential Vk of the cathode 8 must be applied to the back electrodes 13-a and 13-b. Further, the emitted amount of the thermoelectrons designated in the vertical position is controlled by the potential of the modulation electrode 12 on the back surface. That is, if the modulation electrode 12 has the same voltage as the potential Vk of the cathode 8, the amount of thermionic emission is slightly decreased, and the cutoff state is finally reached. This vertical position designation is performed, and the modulated thermoelectrons are transferred to the anode 11
It is focused and deflected with respect to the horizontal direction until it reaches. This focusing / deflecting is performed by a set of focusing / deflecting electrodes 14-a and 14-b on the left and right of the cathode 8 on the side of the anode 11. To give a concrete example, when it is desired to simultaneously turn on the three phosphors 10-R, 10-G, and 10-B, the focusing / deflecting electrodes 14-a and 14-b are not required. If no voltage is applied, the cathode 8 and the anode 11
Have been applied voltage 5~30kV between the cavity 7 is accelerated toward the anode 11 without aforementioned thermal electrons is scattered since maintained at a vacuum 10 ^{@ 3} to 10 ^{over 8} Torr Then, the phosphor 10-R, which penetrates the anode 11,
Visible light is emitted by exciting 10-G and 10-B. Next, when only the green phosphor 10-G is caused to emit light, an appropriate negative voltage is applied to the focusing / deflecting electrodes 14-a and 14-b to form an electrostatic lens on the front surface of the cathode 8. The thermoelectrons are focused in the L1 direction to cause only the green phosphor 10-G to emit light in the above process. Similarly, when only the red phosphor 10-R emits light, an appropriate negative voltage is applied to the focusing / deflecting electrodes 14-a and 14-b to form an electrostatic lens on the front surface of the cathode 8. Then, the thermoelectrons are focused in the L1 direction, and then the focusing / deflecting electrode 1
Electrostatic deflection is performed by superimposing a positive voltage on 4-a and a negative voltage on 14-b, and focused thermoelectrons are bent in the direction of L2, and only the red phosphor 10-R is described above. Light up in the process. Conversely, when only the blue phosphor 10-B emits light, a negative voltage is applied to the focusing / deflecting electrode 14-a.
-B by superimposing a positive voltage on it, the focused thermoelectrons are bent in the direction of L3 and the blue phosphor 10-B
Only the light is emitted in the above process.

The phosphors 10-R, 10-G, 10-B
Must be selected according to the emission color used. A specific example of the phosphor is Y ₂ as the red phosphor 10-R.
O ₂ S: Eu, ZnS: A as blue phosphor 10-B
Examples of the green phosphor 10-G include ZnS: Cu and Al. If you need white light, these red,
This can be achieved by mixing and applying the blue and green phosphors in consideration of the emission luminance balance.

In the present embodiment, a zinc sulfide-based or rare earth-based phosphor for high voltage application is used for the phosphor layer 10, but a low voltage is applied by using a zinc oxide-based phosphor for low voltage light emission. The same result can be obtained even when the light is emitted.

According to the present embodiment, red,
It has the advantage that it can be emitted by switching between three types of light, blue and green.

Further, the lighting device of FIG. 1 can be used as a light source of a liquid crystal television projector by placing liquid crystal in the joint portion 4. 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.

By using the illuminating device according to the present invention, the starting property of the light source is excellent, and a stable light quantity is obtained at the time of starting, so that it is possible to obtain an output faithful to the density value of the image to be read. Further, since the light of each spectrum is applied to the original through the same light guide, the light of each spectrum illuminates the original almost vertically, and the shadow is not generated. This eliminates the problem that a colored shadow is generated in the step portion when reading an image having a step difference, and it is possible to faithfully read an image having an unevenness.

FIG. 3 is a perspective view showing an embodiment of an image input device using the illuminating device according to the present invention, and FIG. 4 is a sectional view of the vicinity of the carriage 17 shown in FIG. Less than,
An operation for reading an image will be described with reference to FIGS. An illuminating device 20 equivalent to that of the above-described embodiment of the present invention is mounted in the carriage 17, and a part of rows L of the image 16 placed on the glass table 15 is irradiated via the light guide member. Then, the reflected and scattered light is passed through the mirror 21 by the reduction lens 22 and the CCD 2 which is a photoelectric conversion element.
Image on 3. The CCD 23 is a one-dimensional image sensor, and one line of image data can be read by an electronic circuit (not shown). Lighting device 2
The carriage 17 having a set of 0, the mirror 21, the reduction lens 22, and the CCD 23 is moved in the direction of arrow B in FIG. 3 by the drive device 19 via the timing belt 18 by a distance corresponding to the reading resolution. By repeating the above operation, the entire surface of the image 16 can be read.

[0017]

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 good startability and light amount stability regardless of the operating environment temperature, has high performance, and has an effect of being able to faithfully read uneven images. Is.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a portion A in FIG.

FIG. 3 is a perspective view showing an embodiment of an image input device using the lighting device according to the present invention.

FIG. 4 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. The image input device used is characterized in that the phosphor is formed on or near a surface of a part of a light guide member, and another part of the light guide member is used 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.