JP3337942B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus using an image pickup means (reading means) in which a plurality of light receiving elements such as CCDs are arranged in a one-dimensional direction. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus that reads image information of a mold original, a non-transmissive photographic print, and the like with high accuracy.

[0002]

2. Description of the Related Art In recent years, an information era using multimedia such as video, text, sound, etc. has entered, and image reading apparatuses for converting image information of photographic films and originals into image signals have been actively studied.

FIG. 14 is a conceptual diagram of such an image reading apparatus.
Shown in In FIG. 14, when reading the image of the transmission original 9, the transmission original 9 is illuminated with a light beam from the light source 8,
An image is formed on a line sensor 11 composed of a photoelectric conversion element by an imaging optical system 10. Then, the light amount distribution of the transmitted light for one line at a certain position is read by the line sensor 11 as the main scanning direction, and then the line sensor 11 or the transmissive original 9 is relatively moved and scanned in the sub-scanning direction. The entire area of the document 9 is read.

A cathode ray tube as an example of a light source used in this image reading apparatus will be described with reference to FIGS. 15, 16 and 17. FIG. FIG. 15 is a front view, and FIG. 16 is a cross-sectional view.

[0005] In Figs. 15 to 17, 1 is a flat glass, 2 is a trough-shaped glass, 3 is hollow, a fluorescent material is applied to the inner wall, and sealed from a gas inlet 4. The filled gas is full. 6 is a connection part. 13 is a white diffusion plate, and 12 is a proximity dielectric as a trigger plate.

This rectangular cathode tube has a light emitting function similar to that of a fluorescent lamp, and a flat glass 1 and a tub-shaped glass 2 are brought into close contact with each other.
The inside is evacuated, mercury and a rare gas are injected from the gas inlet 4 to seal the electrodes, electrodes are arranged at both ends in the longitudinal direction, and connection portions 6 are formed.
Connected to an AC power supply. By supplying an alternating current to the electrodes, the mercury and the rare gas between the electrodes are activated, and ultraviolet rays are emitted, and the ultraviolet rays cause the internal phosphor to emit light. The white diffuser 13 on the back surface of the tub-shaped glass 2 reflects and diffuses the fluorescent illumination, and the proximity dielectric 12 of the trigger plate has a function of attracting the positive column of the flow of electrons, thereby effectively causing the nearby phosphor to emit light. be able to. The light emission of the phosphor from the flat glass 1 illuminates a transmission type original placed in front.

Conventionally, this cathode ray tube is incorporated as a light source of an image reading apparatus as shown in FIG. 14 to read an image.

Next, a schematic configuration diagram of a reflection type image reading apparatus will be described with reference to FIG. In FIG. 18, a light beam from a light source 16 of a cylindrical fluorescent lamp having a long depth in the figure illuminates a reflection original 3 on an original platen glass 2, and the reflected light is reflected by a first mirror 4, a second mirror 5, and a third mirror 3. An image is formed on one line of the reading unit 8 whose main scanning direction is the depth direction on the drawing by the imaging lens 7 via the mirror 6, and the reading unit 8
And outputs an image signal.

When performing the reading operation, the cylindrical light source 16 and the first mirror 4 are integrally scanned in the sub-scanning direction, and reflected light is obtained while illuminating the reflecting original 3. In conjunction with this, the second mirror 5 and the third mirror 6 move integrally, and maintain a constant optical path length from the reflection surface of the document 3 to the reading means 8.

FIG. 19 is an external view of the light source 16 for illumination.
FIG. 20 shows the illuminance distribution in the longitudinal direction of the light source 16. At this time, the illuminance distribution obtained by the cylindrical light source 16 has a mountain shape with a peak near the center as shown in FIG. Due to this illuminance distribution, the reading unit 8 becomes a high-level image signal at the center of the document 3 in the main scanning direction, and becomes a low-level image signal at the end in the main scanning direction. S / N
Was not constant, and the contrast deteriorated.

[0011]

However, in the above-described transmission type image reading apparatus, a hole is formed in the inner wall of a portion corresponding to the gas charging port of the rectangular cathode tube which is a light source for gas charging, and a fluorescent light is emitted. Since there is a portion where the body is not applied, the light amount near the gas filling port is reduced, and a uniform light amount cannot be obtained. When the light amount distribution deviates from the extremely uniform distribution, the operating environment such as temperature and humidity changes, and the reading position of the line sensor shifts. Is displaced, the brightness changes in one captured image, and the image quality may be degraded.

In a reflection type image reading apparatus,
Since the illuminance distribution by the cylindrical light source 16 as shown in FIG. 19 is a mountain distribution as shown in FIG. 20, as described above, when the document is illuminated, the center in the longitudinal direction is bright and darkens toward both ends. For this reason, density unevenness corresponding to the read image occurs.

In order to avoid this, a member for shielding the center of the light beam and reducing the amount of light must be inserted into the optical path to make it uniform. Further, since this image reading apparatus is intended to read image information of a small reflective original such as a photographic print, the apparatus main body is small and many driving parts are provided. Is also difficult.

A first object of the present invention is to alleviate the influence of a portion of a light source on which a phosphor is not applied. A second object according to the present invention is to reduce the influence of the light intensity of the uncoated portion of the phosphor on the total light intensity of the cathode tube. Further, a third object of the present invention is to further reduce the influence of the light intensity due to the phosphor-uncoated portion of the gas filling port due to the synergistic effect achieved by achieving the first and second objects.

A fourth object of the present invention is to provide an illumination having a flat illuminance distribution in the longitudinal direction by using a cathode tube having a gas inlet substantially at the center in the longitudinal direction, particularly in the case of a reflection type. It is an object of the present invention to provide an image reading apparatus. A fifth object of the present invention is to provide an image reading apparatus capable of efficiently illuminating by using a cathode ray tube having a flat document facing surface. Further, a third object according to the present invention is to provide an image reading apparatus in which the close proximity conductor plate is in close contact with the cathode tube, so that the cathode tube is smoothly turned on. Further, a fourth object of the present invention is to provide an image reading device capable of more efficient illumination by providing a white diffuser plate in close contact with a cathode tube.

[0016]

In order to achieve the above object, the present invention provides a transmission type original, a light source for irradiating the original, an imaging lens for condensing the transmitted light transmitted through the original,
In an image reading apparatus provided with a line sensor for photoelectrically converting the condensed transmitted light, a light source is provided with a cathode tube, and a proximity dielectric of the cathode tube is placed closer to the center of a surface opposite to a light emitting surface of the cathode tube. It is characterized by being arranged at a position shifted in a direction away from the gas filling port. As a result, the positive column generated when the cathode tube is discharged can be drawn in a direction away from the gas filling port, thereby reducing the influence of the phosphor-uncoated portion. Further, in a cathode tube in which a plate-shaped glass is in close contact with a lid of the trough-shaped glass, and a gas sealing port for sealing gas used for light emission is provided at a central portion of a longitudinal side surface of the trough-shaped glass, A proximity dielectric is disposed outside a side surface of the trough-shaped glass opposite to a side surface on which the gas filling port is provided. Further, the present invention provides
An image reading apparatus comprising: a light source for irradiating a placed document with light; an imaging lens for converging transmitted light transmitted through the document; and a line sensor for photoelectrically converting the collected transmitted light. As a plate-like glass is tightly attached as a lid of a trough-shaped glass, and a gas sealing port for sealing gas used for light emission is located at the center of a longitudinal side surface of the trough-shaped glass.
A cathode tube provided in a portion thereof, wherein a cathode dielectric is disposed outside a side surface of the trough-shaped glass opposite to a side surface on which the gas sealing port is provided. Still further, the invention includes a light source for irradiating the placed document with light, an imaging lens for condensing transmitted light transmitted through the document, and a line sensor for photoelectrically converting the collected transmitted light. In the image reading apparatus, as the light source, a plate-shaped glass is tightly adhered as a lid of a trough-shaped glass, and a gas filling port for filling gas used for light emission is provided at a center of a longitudinal side surface of the trough-shaped glass. A cathode tube provided on a portion , wherein a white diffuser plate is disposed outside a side surface of the trough-shaped glass opposite to a side surface provided with the gas filling port and a bottom surface of the trough-shaped glass. It is characterized by the following. Further, according to the present invention, there is provided an image including a light source for irradiating a placed document with light, an imaging lens for converging transmitted light transmitted through the document, and a line sensor for photoelectrically converting the collected transmitted light. In the reading device, as the light source, a plate-shaped glass is closely adhered as a lid of a trough-shaped glass, and a gas sealing port for sealing gas used for light emission is a central portion of a longitudinal side surface of the trough-shaped glass. In the cathode tube provided in, a white diffuser plate is disposed outside the side surface of the trough-shaped glass opposite to the side surface where the gas sealing port is provided and the bottom surface of the trough-shaped glass, A cathode tube is used in which a proximity dielectric is disposed outside the white diffusion plate on a side surface opposite to a side surface on which a gas filling port is provided.

According to a second aspect of the present invention, in the above image reading apparatus, the white diffuser plate of the cathode tube is displaced from the center of the surface of the cathode tube opposite to the light emitting surface in a direction away from the gas filling port. It is characterized by being arranged. From this, of the light flux that escapes to the back surface of the cathode tube, reflects the light beam that escapes from the portion that is distant from the gas filling port, and returns to the front side of the cathode tube,
By increasing the amount of light at the portion of the gas inlet that is less affected by the uncoated portion of the phosphor, the effect of the amount of light at the uncoated portion of the phosphor on the total amount of light is reduced. Also plate-like
The glass serves as a lid for the trough-shaped glass,
The gas filling port for filling the gas used is the trough-shaped glass
The cathode tube provided on the side surface of
A side surface opposite to a side surface on which the gas filling port is provided;
A white diffuser is placed outside the bottom of the trough glass.
It is characterized by that.

In a third aspect of the present invention, in the above image reading apparatus, the proximity dielectric of the cathode tube and the white diffuser are arranged in a direction away from the gas inlet than the center of the surface of the cathode tube opposite to the light emitting surface. It is characterized by being arranged at a shifted position. As a result, due to the synergistic effect of the first and second aspects of the present invention, the influence of the amount of light due to the non-coated portion of the gas filling port on the phosphor is reduced. Also, the sheet glass serves as a lid for the trough glass.
Gas that is used for light emission
The sealing hole is provided in the cathode tube provided on the side of the trough-shaped glass.
The gas filling port of the trough-shaped glass is provided
Outside the side opposite to the side and the bottom of the trough-shaped glass
A white diffusing plate is arranged, and the gas filling of the trough glass is performed.
Of the white diffusion plate on the side surface opposite to the side surface where the mouth is provided
It is characterized in that a proximity dielectric is disposed outside.

According to a fourth aspect of the present invention, there is provided an original document, a light source for irradiating the original document, an imaging lens for converging light reflected by the original document, and a line sensor for photoelectrically converting condensed transmitted light. And a cathode tube having a gas filling port substantially at the center in the longitudinal direction of the light source. As a result, illumination having a flat illuminance distribution in the longitudinal direction becomes possible, and a good image can be obtained without a light shielding member. In addition, the original
A light source that irradiates the original with light and the transmitted light that has passed through the original.
Focusing imaging lens and photoelectrically convert collected transmitted light
An image reading apparatus comprising: a line sensor;
A cathode tube according to any one of 1 to 3, wherein the light source is
It is characterized by being used.

Further, a fifth invention is characterized in that, in the fourth invention, the document tube facing surface of the cathode ray tube is flat. As a result, efficient illumination can be performed without a reflection member such as a reflection shade.

According to a sixth aspect, in the fifth aspect, the proximity conductor plate is closely attached to the cathode tube. As a result, the proximity conductor plate serves as an auxiliary electrode, and it is possible to quickly raise light emission during lighting.

Further, a seventh invention is characterized in that, in the fifth and sixth inventions, a white diffusion plate is in close contact with the cathode tube. As a result, light passing through the back surface can be efficiently returned to the flat glass side, and brighter illumination can be obtained.

In an eighth aspect based on the fourth aspect, the cathode tube is formed by closely attaching a plate glass and a trough glass, and the gas filling port is formed on a side surface of a bottom surface of the trough glass. The proximity dielectric is adhered to the outside of the bottom surface of the trough-shaped glass, and further, a white diffuser plate is formed on the side of the trough-shaped glass opposed to the side where the gas filling port is arranged and on the outside of the proximity dielectric. It is characterized by being in close contact. Thus, the effects of the fourth to seventh inventions can be synergistically obtained.

According to a ninth aspect of the present invention, there is provided an illuminating device for use in the image reading apparatus, comprising: a light source for irradiating an original from which an image signal is read; and an imaging lens for converging light reflected by the original. In the illumination device provided with the above, a cathode tube having a gas filling port substantially at the center in the longitudinal direction of the light source is used as the light source. Further, the cathode tube is formed by closely attaching a plate glass and a trough glass, the gas filling port is disposed on a side surface of the bottom surface of the trough glass,
A proximity dielectric is adhered to the outside of the bottom surface of the trough glass,
Further, a white diffuser plate is in close contact with a side surface of the trough-shaped glass opposite to a side surface on which the gas filling port is arranged and the outside of the proximity dielectric. In this way, it is possible to effectively irradiate the reflected light of the document to the photosensitive member.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIGS. 1 and 2 are schematic views of a main part of a light source of an image reading apparatus according to the present invention. In both figures, 1 is a flat glass and 2 is a trough-shaped glass, which forms a gas filled portion of a portion 3 surrounded by the flat glass 1 and the trough-shaped glass 2. Further, a phosphor emitting white light similar to, for example, a general fluorescent lamp is applied to the entire inner wall of the inner wall of the gas sealing portion 3. Reference numeral 4 denotes a gas seal which is arranged inside the close contact portion between the flat glass 1 and the trough-shaped glass 2 and at the central portion in the longitudinal direction, and which fills the gas filling portion 3 with a mixed gas of mercury or a rare gas. An entrance 5 is a proximity dielectric fixed on the outer side of the side of the trough-shaped glass 2 on the side opposite to the gas filling port 4, and is closer to the gas-sealing port 4 than the center of the trough-shaped glass 2 on the short side section. It is located at a position shifted in the direction away. Also, 6
Is a connection part which is a part of the sealing between the flat glass 1 and the tub-shaped glass 2 and is connected to electrodes disposed at both ends in the longitudinal direction inside the connection. Power is supplied from, for example, an inverter circuit or the like. .

FIG. 3 shows a conventional light source for a transmission type (FIG. 15, FIG.
16 and 17), and FIG. 4A shows the corresponding luminance distribution of the light source described in the present embodiment according to the present invention. For reference, FIGS. 4B and 4C show luminance distributions in the longitudinal direction by the light sources described in a second embodiment and a third embodiment described later. That is, the gas filling port 4 is arranged at the center in the longitudinal direction,
The proximity dielectric is applied and adhered to the side surface of the trough-shaped glass 2 opposite to the gas filling port 4, so that when the cathode tube having the flat glass 1 and the trough-shaped glass 2 as an outer casing discharges, The generated positive column can be drawn in a direction away from the gas charging port 4, whereby the influence of the gas charging port 4, which is a portion where the phosphor is not applied, can be reduced.

A conceptual diagram of an image reading apparatus using a light source as a cathode ray tube according to the present embodiment will be described again with reference to FIG. In FIG. 14, reference numeral 8 denotes a light source which is the cathode ray tube described in the present embodiment, 9 denotes a transmissive document emitted from the light source 8, 11 denotes a line sensor which is a photoelectric conversion element for one line in the depth in the drawing, and 10 denotes a line sensor. An image forming optical system forms an image of transmitted light transmitted through the transparent original 9 on the line sensor 11.
The line sensor 11 scans the transmitted light for one line in a time-series manner in the main scanning direction to read and output an image signal. At this time, the relative position between the transparent document 9 and the line sensor 11 is changed in the sub-scanning direction, and the two-dimensional image information of the transparent document 9 is sequentially read by the line sensor 11. Although not shown in the figure, a folding mirror is provided between the transparent document 9 and the line sensor 11 to reduce the length in the horizontal direction in the figure.

Next, a light source which is a feature of the present embodiment will be described in detail. In a hollow gas sealing portion 3 formed by the flat glass 1 and the trough-shaped glass 2, first, air is evacuated to create a vacuum, and usually mercury gas, argon gas, xenon gas, or the like is sealed from a gas sealing port 4. When a silver halide film or the like is used as a transmissive original, the light source may be warped and deformed if a heating element is present in the vicinity of the original due to the characteristics of the material of the original. A cold-cathode tube, which generates a small amount of heat from the tube, can be arranged close to the document, and has high illumination efficiency, is used.

On the outside of the trough-shaped glass 2 of the cathode-ray tube (the gas-filled portion 3 is defined as “inside”), a near dielectric 5 elongated in the longitudinal direction of the trough-shaped glass 2 has a short cross section of the trough-shaped glass 2. Above, it is arranged at a position shifted in a direction away from the gas filling port 4.

When the above-mentioned cathode ray tube is turned on, a current for effectively illuminating the phosphor is supplied from the connection portion 6. Then, thermoelectrons are emitted from the internal electrode (cathode) into the tube, and the thermoelectrons are attracted by the high pressure of the opposite electrode (anode) and move, so that a discharge starts, and a positive column, which is a collection of thermoelectrons, is generated. The flowing electrons collide with mercury atoms in the cathode tube to generate ultraviolet light, and the ultraviolet light excites a fluorescent substance applied in the gas sealing portion 3 to generate visible light.

Here, at the time of producing the above-mentioned cathode ray tube, the gas sealing portion 3 is formed by the flat glass 1 coated with the phosphor and the trough-shaped glass 2, and then the gas is sealed from the gas sealing portion 4. For this reason, the gas sealing portion 4 on the inner wall of the gas sealing portion 3
There is a portion where the phosphor is not applied only in the portion corresponding to.
Therefore, the luminance distribution in the longitudinal direction of the cathode tube is
The brightness is reduced only in the portion corresponding to (see FIG. 3).

Therefore, in the present invention, as described above, the proximity dielectric 5 is arranged at a position shifted away from the gas filling port 4 on the short cross section outside the trough-shaped glass 2. Since the proximity dielectric has a function of attracting a positive column, which is a flow of electrons, the electrons collide with mercury atoms at a position distant from the gas filling port 4 to generate ultraviolet rays, and the phosphor in the vicinity is excited. Generates visible light. This makes it possible to reduce the luminance drop in the phosphor-uncoated portion (FIG. 4).
(A)).

(Second Embodiment) FIGS. 5 and 6 show a second embodiment of a light source which is a cathode ray tube used in an image reading apparatus according to the present invention. 5 and 6, the same reference numerals as those in FIG. 1 have the same functions and description thereof will be omitted. In FIGS. 5 and 6, reference numeral 7 denotes a white diffuser, which is the bottom of the trough-shaped glass 2 and the gas filling port 4.
A white diffusing material is applied or affixed to the outside of the side surface opposite to.

In the present embodiment, a white diffuser plate 7 is arranged outside the trough-shaped glass 2 of the cathode ray tube at a position shifted in a direction away from the gas filling port 4 on a short cross section of the trough-shaped glass 2. As a result, the luminous flux escaping from the trough-shaped glass part 2 can be returned to the gas sealing part 4 side, and the luminous flux hardly affected by the light quantity fall due to the phosphor-uncoated portion near the gas sealing port 4 The amount of light can be increased (see FIG. 4B). The method of manufacturing the light source as the cathode ray tube, the method of lighting it, and the like are the same as in the first embodiment.

(Third Embodiment) FIGS. 7 and 8 show a third embodiment of a light source which is a cathode ray tube used in an image reading apparatus according to the present invention. Reference numerals 1 to 7 are as described in the first embodiment and the second embodiment, and the description is omitted.

In this embodiment, the proximity dielectric 5 and the white diffusion plate 7 are located outside the trough-shaped glass 2 of the cathode-ray tube at a position shifted away from the gas filling port 4 on the short cross-section of the trough-shaped glass 2.
Is arranged. That is, a white diffusing material is applied or affixed to the outside of the bottom surface of the trough-shaped glass 2 and the side surface facing the gas filling port 4, and the proximity dielectric 5 is placed outside the side surface facing the same gas filling port 4. Coated or affixed. As a result, the effects of the first embodiment and the second embodiment can be both obtained, and the influence of the light quantity fall due to the uncoated portion of the phosphor near the gas filling port 4 and the generation of the positive column generated in the cathode tube can be reduced. Thus, the original can be irradiated with a uniform amount of illumination light.

(Fourth Embodiment) FIG. 9 is a conceptual schematic diagram of a reflection type image reading apparatus according to the present invention. FIG. 9 is a diagram showing an outline of the apparatus, and FIG. 11 is a diagram showing an illuminance distribution obtained by FIG. In FIG. 9, 21 is a flat light source, 22
Denotes a platen glass, 23 denotes a small reflective original such as a photographic print, 24 denotes a first mirror, 25 denotes a second mirror, and 26 denotes a third mirror.
A mirror 27 is an imaging optical system, and 28 is a reading means such as a CCD. FIG. 10 is a view showing an external view of a light source which is a feature of the present invention, showing each part of the flat light source 1, 29 is a gas filling port, 30 is a Dumet wire, 31 is a light emitting section, 32
Indicates a flat glass, and 33 indicates a trough-shaped glass.

Next, the actual operation will be described. When reading the reflective original 23, the original 23 on the original platen glass 22 is illuminated by the flat light source 1, and the reflected light is received by the first mirror 24. The plane light source 21 and the first mirror 24 are integrated, and scan in the sub-scanning direction so as to read while illuminating the reflective original 23. The light beam reflected by the first mirror 24 is repeatedly reflected by the second mirror 25 and the third mirror 26 that operate integrally. At this time, the planar light source 21
The second mirror 25 and the third mirror 26 move together so that the entire optical path length becomes constant when the first mirror 24 and the first mirror 24 scan. The light beam reflected by the second mirror 25 and the third mirror 26 is
7 forms an image on a reading means 28 of a photoelectric conversion element such as a CCD for one line, is read, and is output as an image signal.

Next, the flat light source 21 will be described. The flat light source 21 is filled with a mercury gas, an argon gas, a xenon gas, or the like in a hollow formed by a gas charging port 29 located substantially at the center in the longitudinal direction of the flat glass. Since the tub-shaped glass 33 is used, at least the document-facing surface side of the light source is flat, so that unlike a conventional cylindrical light source, an auxiliary member such as a reflector is not required. FIG.
As shown in FIG. 1, the illuminance distribution in the longitudinal direction of the planar light source 21 is a flat distribution as compared with the illuminance distribution in the longitudinal direction of the conventional cylindrical light source 16 in FIG. This is because of the illuminance distribution because the gas filling port 29 is located substantially at the center of the flat light source 21 in the longitudinal direction. When manufacturing the lamp, the flat glass 32
The phosphor is applied to a portion of the gas filled portion of the glass 33 and the flat glass 32 and the glass 33
To form a gas-filled portion. Since the gas is filled from the gas filling port 29 later, the phosphor is not applied to the inner wall of the gas filling part corresponding to the gas filling port 29. As a result, the brightness of the portion corresponding to the gas filling port in the longitudinal direction of the flat light source 21 becomes lower than that of the other adjacent portions, and as a result, flat illuminance is obtained as shown in FIG.

As a result, it is possible to illuminate the reflective original with flat illuminance without separately providing a light-shielding member, and it is possible to obtain a good image even in a reflective original reading apparatus having fewer components.

(Fifth Embodiment) FIG. 12 is a sectional view of a fifth embodiment of a light source which is a cathode ray tube used in a reflection type image reading apparatus according to the present invention. It shows a cross section in the lateral direction. Reference numeral 34 in FIG. 12 denotes a proximity conductor.

By providing the proximity conductor 34 in the flat light source 1, the proximity conductor 34 functions as an auxiliary electrode, and the rising at the time of lighting becomes faster.

Thus, there is no need to have a spare time when reading a reflection original.

(Sixth Embodiment) FIG. 13 shows a sixth embodiment of a light source which is a cathode ray tube used in a reflection type image reading apparatus according to the present invention. It shows a cross section in the hand direction. In FIG. 13, 34 is a proximity conductor, and 35 is a white diffusion plate.

A proximity conductor 34 is provided on the outside of the bottom of the trough-shaped glass 33 in close contact with the flat glass 32 of the flat light source 2 to serve as an auxiliary electrode, so that the rise at the time of lighting is fast.
Further, by providing the white diffusing plate 35 behind the white diffusing plate 35, the white diffusing plate 35 plays a role of a reflection shade, and returns the luminous flux passing through the back surface to the document surface side. This makes it possible to obtain brighter illumination on the document surface.

[0046]

As described above, according to the first aspect of the present invention, it is possible to reduce the amount of light in the uncoated portion of the phosphor, to obtain a more flat illumination light beam, and to be resistant to changes in the operating environment. An image reading device can be obtained. Also, the second
According to the invention, it is possible to increase the light amount of the portion where the influence of the phosphor-uncoated portion is small, and to reduce the ratio of the light amount of the uncoated portion of the phosphor to the entire light amount. And an image reading apparatus that is resistant to changes in the operating environment due to efficient illumination can be obtained. Further, according to the third aspect, as in the first aspect, it is possible to reduce the amount of light in the uncoated portion of the phosphor, and to further reduce the ratio of the amount of light to the entire amount of light. This makes it bright and
Further, illumination that is more nearly flat can be obtained, and as a result, an image reading apparatus that is more resistant to changes in the operating environment due to efficient illumination can be obtained.

Further, according to the fourth aspect of the present invention, illumination having a flat illuminance distribution in the longitudinal direction becomes possible, so that a separate light-shielding member for obtaining a good image is not required, and cost reduction and downsizing are easy. Has the effect of becoming Also, the fourth
According to the invention, even if there is no reflection member such as a reflection shade, it is possible to perform efficient illumination, and it is advantageous in that cost reduction and downsizing become easy. Further, according to the fifth aspect, the rising of the light emission at the time of lighting is made quicker, and the preliminary time is not required, so that there is an effect that the reading time of the reflection original is shortened. According to the sixth aspect,
Since light that penetrates the back surface can be efficiently returned to the flat glass side and brighter illumination can be obtained, there is an effect that efficient illumination can be performed. Further, according to the seventh and eighth aspects, the power supply on / off operation of the illuminating means for irradiating the original can be performed at a high speed, the illuminance on the original surface is improved, and the contrast of the reflected light is also improved. The output level and S / N of the line sensor can be kept high.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a main part of a first embodiment according to the present invention.

FIG. 2 is an external view of a first embodiment according to the present invention.

FIG. 3 is a diagram showing a luminance distribution by a conventional light source.

FIG. 4 is a diagram showing a luminance distribution of a light source according to the present invention.

FIG. 5 is a schematic sectional view of a main part of a second embodiment according to the present invention.

FIG. 6 is an external view of a second embodiment according to the present invention.

FIG. 7 is a schematic sectional view of a main part of a third embodiment according to the present invention.

FIG. 8 is an external view of a third embodiment according to the present invention.

FIG. 9 is a schematic diagram of Embodiment 4 according to the present invention.

FIG. 10 is a partial explanatory view of a fourth embodiment according to the present invention.

FIG. 11 is an explanatory diagram of an effect of the fourth embodiment according to the present invention.

FIG. 12 is a partial explanatory view of a fifth embodiment according to the present invention.

FIG. 13 is a partial explanatory view of a sixth embodiment according to the present invention.

FIG. 14 is a schematic view of an image reading apparatus according to the present invention and the related art.

FIG. 15 is a schematic sectional view of a main part of a conventional image reading apparatus.

FIG. 16 is an external view (front view) of a conventional image reading apparatus.

FIG. 17 is an external view (back side) of a conventional image reading apparatus.

FIG. 18 is a schematic view of a conventional image reading apparatus.

FIG. 19 is a partial explanatory view of a conventional image reading apparatus.

FIG. 20 is a diagram illustrating the state of a conventional image reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat glass 2 Trough glass 3 Lamp gas filling part 4 Gas filling port 5 Proximity dielectric 6 Connecting part 7 White diffusion plate 8 Scattered light source 9 Transmissive original 10 Imaging optical system 11 Line sensor 12 Proximity dielectric 13 White diffusion plate 16 Conventional cylindrical light source 21 Planar light source 22 Original platen glass 23 Reflected original 24 First mirror 25 Second mirror 26 Third mirror 27 Imaging optical system 28 Reading means 29 Gas filling port 30 Dummet line 31 Light emitting unit 32 Flat glass 33 Oval shape Glass 34 Proximity dielectric 35 White diffuser

Claims (3)

(57) [Claims] A light source for irradiating the placed document with light, an imaging lens for focusing transmitted light transmitted through the document,
In an image reading apparatus including a line sensor that photoelectrically converts the condensed transmitted light, as the light source, a plate-shaped glass serves as a lid of a trough-shaped glass and is in close contact therewith, and seals a gas used for light emission. A gas inlet is a cathode tube provided at a central portion of a longitudinal side surface of the trough-shaped glass, and a proximity dielectric is disposed outside a side of the trough-shaped glass opposed to a side at which the gas fill port is provided. An image reading apparatus using a cathode tube as described above. 2. A light source for irradiating a placed original with light, an imaging lens for focusing transmitted light transmitted through the original,
In an image reading apparatus including a line sensor that photoelectrically converts the condensed transmitted light, as the light source, a plate-shaped glass serves as a lid of a trough-shaped glass and is in close contact therewith, and seals a gas used for light emission. A gas filling port is a cathode ray tube provided at a central portion of a longitudinal side face of the trough-shaped glass, and a side face and a bottom face of the trough-shaped glass facing the side face of the trough-shaped glass where the gas filling port is provided. An image reading apparatus using a cathode tube in which a white diffusion plate is arranged outside the image forming apparatus. 3. A light source for irradiating a placed document with light, an imaging lens for focusing transmitted light transmitted through the document,
In an image reading apparatus including a line sensor that photoelectrically converts the condensed transmitted light, as the light source, a plate-shaped glass serves as a lid of a trough-shaped glass and is in close contact therewith, and seals a gas used for light emission. A gas filling port is a cathode ray tube provided at a central portion of a longitudinal side face of the trough-shaped glass, and a side face and a bottom face of the trough-shaped glass facing the side face of the trough-shaped glass where the gas filling port is provided. A cathode diffuser in which a white diffusion plate is disposed outside the glass plate, and a proximity dielectric is disposed outside the white diffusion plate on a side surface of the trough-shaped glass opposite to a side surface on which the gas filling port is provided. Image reading device.