JPH0879446A - Image input device - Google Patents

Abstract

PURPOSE: To enable a color image input device miniaturizing/accelerating or energy saving/performance improving by considerably improving the irradiation efficiency of a light source without using a light shielding layer by using a convergent rod array lens array. CONSTITUTION: Concerning the image input device composed of an optical system 13 for picking up the image of an original plane 11, photoelectric converting element arranged on the image forming plane of this optical system 13 and light source 12 with which the original plane 11 is irradiated, the light source 12 arranging a light emitting body such as an LED or a fluorescent body on a base substrate 15 is arranged between the original plane 11 and the optical system (convergent rod lens array) 13 and the optical system 13 picks up the image of the original plane 11 through the gap with the light emitting body of the light source 12. The arrangement of the light emitting body is optimized from the light emitting efficiency of the light emitting body/the polarizing sensitivity of a solid-state imaging device 14/the distance from the original plane to the light emitting body or the like so that the most efficient arrangement can be provided out of the view field of the convergent rod lens array 13. Besides when a fluorescent display tube is used for the light source 12, dispersion in the quantity of light is reduced. Further, the base substrate 15 or cover glass can be used as a reading plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device, and more particularly to a color image input device.

[0002]

2. Description of the Related Art As a light source used in a reduction optical system image input device or a contact type image input device, an LED light source is generally used because of its small size, constant voltage, DC drive and high reliability. .

However, in recent years, there has been an increasing demand for miniaturization of image input devices due to the spread of portable devices or for color image input devices such as color image input devices such as color copiers and color scanners.

When a conventional LED light source is used, the light source illuminates the original surface at an angle of about 45 ° and an image is formed on a solid-state image pickup device by an optical system. In this case, since the light sources are arranged obliquely, it is necessary to expand in the lateral direction, which limits the miniaturization.

The color image input device generally introduced is (1) a device using a color photoelectric conversion element in which a color filter is formed on the photoelectric conversion element,
There are (2) a system in which color filters are mechanically switched, and (3) a system in which light sources of three colors are used.

In the method using the color filters of (1) and (2), the amount of light received by the solid-state image pickup element is attenuated by about 40 to 50% in the color filter, and therefore an optical system / light source that is brighter than usual must be used. Output and gradation will decrease. However, if the optical system is made large, the parts become large, and if the light source is made bright, the light source becomes large and heat is generated.

Further, since a color filter manufacturing process is added or a color filter switching mechanism is added, the productivity is low and the cost is high.

The reading device of the type (3) using a three-color light source does not use a color filter unlike the above-mentioned two types, so that the received light is not attenuated and the color can be switched by the light source. Although the mechanism can be a simple structure, since three light sources are used, the device becomes large, the amount of heat generated is large, and the cost is high.

Further, LE which consumes less power and can be miniaturized
Since D has insufficient blue emission brightness and cannot be put to practical use, a cold cathode tube or a fluorescent tube is used as a light source, but a high voltage of several hundred to 1 kV is required for its lighting voltage, and the lighting device becomes large and high voltage is applied. The control for is complicated.

In view of these problems, there is an example in which a fluorescent display tube provided with an aperture is combined with a roof mirror lens array as in Japanese Patent Publication No. 5-32943, for example.
Practical use due to the drawbacks that the device becomes large because it is combined with the Dach mirror lens array, the aperture width is narrow, and it must be accurately aligned with the optical axis of the imaging optical system, or that the aperture must be made inside the fluorescent display tube. Has not reached.

FIG. 5 shows an example in which this technique is applied to a reduction optical system image input device. 51 is a manuscript, 53 is red,
A fluorescent display tube capable of emitting three colors of blue and green, a reduction optical lens 52, a solid-state imaging device 54, a base substrate of the fluorescent display tube 55, a light shielding layer (aperture) 56, and a reflector 57. The surface of the document 51 illuminated by the light-emitting body is reflected by the reflection plate 57, reduced by the lens 52, and focused on the solid-state image sensor.

As a general example of the reduction optical system, if the object-image distance is 300 mm, the reduction ratio is 1: 9, and the document width is 216 mm, the inclusion angle is about 43.6 °. In the case of a reduction optical system, the reduction optical lens 52 captures an image in the main scanning direction of the solid-state image sensor 54 over a range equal to or larger than the document width. In this case, since the image pickup range in the sub-scanning direction is imaged in the range close to the inclusion angle of 43.6 °, the light emitter must be arranged within the image pickup range of the lens. When the light emitter is arranged within the image pickup range of the lens, light is directly emitted from the light emitter to the solid-state image pickup element 54 and affects the resolution, so that a light shielding layer (aperture) 56 must be arranged in the optical path. When arranging the light source, the position of the light shielding layer (aperture) 56 and the imaging position of the optical system must be adjusted, which is complicated. Further, the reduction optical system has a drawback that the entire apparatus becomes large.

[0013]

As described above, the conventional image input device has problems such as enlargement and colorization of the device (light source / productivity).

Therefore, the present invention solves the drawbacks of the prior art, and an object of the present invention is to provide an image input device which is small in size and light in weight, and which can easily cope with colors.

[0015]

[Means for Solving the Problems]

(Means 1) In an image input device including an optical system for picking up an image of a document surface, a photoelectric conversion element arranged on the image plane of the optical system, and a light source for illuminating the document surface, the optical system emits light from the light source. It is characterized by a converging rod lens array that captures an image of a document surface through the body.

(Means 2) The present invention is characterized in that the base substrate on which the luminous body of the light source is arranged serves as a document reading surface.

(Means 3) The light source is a fluorescent display tube,
The base substrate or the cover glass is used as a document reading surface.

[0018]

According to the present invention, the light source is arranged in parallel with the document surface and is combined with the rod lens array having a narrow visual field to efficiently illuminate the document surface. That is, the light source is arranged in parallel with the document surface to make the distance to the document surface as close as possible. At this time, if a rod lens array with a narrow field of view is used, the light-emitting body of the light source and the document surface can be brought close to each other without providing a light-shielding layer or aperture for avoiding stray light.

In particular, when a fluorescent display tube is used as a light source, the light-emitting body emits light uniformly, so that there is little variation in the amount of light, the base substrate or cover glass can be used as the reading surface, and color compatibility is possible. Suitable for the present invention.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a contact type image input device of the present invention. Reference numeral 11 is a document, 12 is a light source, 13 is a converging rod lens array (equal magnification erecting imaging lens array), and 14 is a solid-state image sensor. The converging rod lens array 13 is a light source 12
The surface of the original 11 illuminated by the image is imaged through the base substrate 15 on which the light emitter of the light source is arranged,
Image. The base substrate 15 of the light source 12 also serves as a document reading surface.

As the light-emitting body, one in which LEDs are arranged on the base substrate, or a fluorescent display tube in which a phosphor is arranged is used. For colorization, use a light source that emits red, green, and blue light.

FIG. 2 shows an example of a fluorescent display tube used as a light source of a color image input device as one embodiment of the present invention. 25 is a base substrate, 22R, 22G and 22B are red.
Green and blue phosphors (anode electrodes), 23 is a filament (cathode electrode), and 24 is a cover glass.

The red phosphor 22R has a wavelength range of 660 nm,
The green phosphor 22G has a wavelength range of 530 nm, and the blue phosphor 2
2B uses a phosphor in the wavelength region of 450 nm.

The solid-state image pickup device is the same as the solid-state image pickup device for black and white, and the solid-state image pickup device scans three times with respect to one scanning line on the document surface. During scanning three times, light of wavelengths of red, green, and blue are emitted from the light source onto the document. The scanning method can be either line sequential in which the light from the light source is switched line by line or surface sequential in which one surface is read by each color light source.

When the converging rod lens array 21 having an aperture angle of 15 ° and a fiber diameter of 0.86 mm is used, the field of view thereof is about 3.2 mm. This visual field 27 in FIG.
No illuminant is arranged in the range indicated by the broken line in the figure.
The light emitted from the light-emitting body from outside the field of view is not incident on the rod lens 21 because the incident angle on the converging rod lens 21 is 15 ° or more. That is, the light emitter 22
The light directly incident on the converging rod lens array is 15
Since the incident angle is not less than 15 °, it is not incident, and the field of view 27 of the converging rod lens array 21 is 15 ° or less.
Only the light enters the lens 21 and forms an image on the solid-state image sensor. Therefore, the luminous body is the field of view 2 of the focusing rod lens.
It is arranged outside the end of 7. For example, the field of view 3.2
mm, phosphor width 1.5 mm, gap between phosphors 0.2
If the distance is 5 mm, the phosphor is formed within a width of 9.7 mm, so the overall width is about 15 mm, the height is 25 mm (the distance between the image planes of the focusing rod lens), and the length is 230 mm (reading width). Can be stored in the device. This is less than half the volume of conventional color image input devices.

The arrangement of the light emitters of the light source is determined from the spectral sensitivity of the solid-state image pickup element and the luminous efficiency of the light emitters. A light-emitting body having a wavelength with good spectral sensitivity and good emission efficiency of the solid-state image pickup element is arranged on the outside, and a light-emitting body with wavelength having low spectral sensitivity of the solid-state image pickup element and poor emission efficiency is arranged inside. When an amorphous silicon photodiode is used as the solid-state image sensor and a fluorescent display tube is used as the light source, the solid-state image sensor has a low spectral sensitivity of blue and red, and the light emission efficiency of the light source is generally blue. . Therefore, blue and red are arranged inside so as to be close to the image pickup position of the lens to improve the irradiation efficiency. Green with good spectral sensitivity and good luminous efficiency is placed outside. Since green is far from the image pickup position of the lens, uneven light amount is likely to occur, and therefore irradiation is performed from both sides.

As is well known, in a fluorescent display tube, thermoelectrons emitted from a filament in a high vacuum are accelerated by a positive voltage of several volts to several tens of volts applied to the anode to excite the phosphor coated on the anode. And emit light. Therefore, the brightness of the fluorescent display tube depends on the luminous efficiency of the phosphor, the amount of thermoelectrons emitted from the filament, and the applied voltage. Therefore,
The filaments 23 of the fluorescent display tube are arranged so that two filaments 23G, 22R, 22B, 22G coated on the anode electrode are always opposed to each other, and the positional relationship between each filament 22 and the filament 23 is arranged. Are made equal.
As a result, the amount of thermoelectrons emitted from the filament becomes uniform with respect to each phosphor, and sufficient thermoelectrons can be emitted by disposing a plurality of filaments.

Lighting control of the phosphor fluorescent display tube is performed only by controlling the anode electrode, and the filaments that contribute to the phosphor to emit light are always energized. This is because it takes several seconds after the filament is energized to generate thermoelectrons, and the light source cannot be switched at high speed by controlling the filament (cathode electrode). If the filament is always energized and the light emission is controlled only by controlling the anode electrode, the light source can be switched on at a speed of 1 μsec or less, and high-speed switching of the light source required for line sequential reading or the like can be supported.

Further, the fluorescent substance of the fluorescent display tube is arranged longer than the effective reading width of the solid-state image pickup device by 1 mm or more so that the variation in the luminance at the end does not affect the output of the solid-state image pickup device. With this arrangement, the red, green, and blue colors efficiently irradiate the original from almost the same position and uniformly illuminate the effective reading range, and the unevenness of the light amount is 10%.
It is the following. Since the distance from the light emitter to the image pickup surface is very close to about 2 mm, the loss of the emitted light amount is small. This is a dramatic technical improvement as compared with the conventional LED light source in which the light amount nonuniformity is 15 to 20% and the irradiation position is 7 to 10 mm.

FIG. 3 shows another embodiment. The light source 32 shown in this embodiment may be a light source in which a light emitting body is arranged on a transparent base substrate 35 such as glass, or the light emitting body is arranged on an insulating base substrate in which a portion through which light passes is formed in a slit shape. It may be a light source. Alternatively, a plurality of light sources may be arranged in parallel with the document surface at a position avoiding the visual field of the converging rod lens array. Unlike the above-described embodiment, the base substrate 35 is arranged on the side of the focusing rod lens array 33. When the base substrate 35 is arranged on the side of the converging rod lens array 33, since the distance of the luminous body from the imaging surface becomes large, the irradiation efficiency of the luminous body is slightly lowered, but the visual field of the condensing rod lens array is narrow. The width of the light source can be reduced because it can be arranged at any position. In the image input device of the present invention, the light source is arranged in parallel to the document surface, so that the width dimension of the device is dominated by the width of the light source. Therefore, if the width of the light source is reduced, the size of the entire device can be reduced. For example, if the thickness of the base substrate on which the light emitters are arranged is 1.0 mm, the range that affects the field of view of the converging rod lens array is about 1.4 mm, which is smaller than the field of view 27 shown in FIG. Also, the width can be narrowed by 1.8 mm.

If a fluorescent display tube is used as the light source 32, the cover glass of the fluorescent display tube can also serve as the original reading surface, as shown in FIG. Fluorescent display tubes generally have a transparent conductor layer on the cover glass surface as a measure against static electricity. If the cover glass of the fluorescent display tube is used as the reading surface, it is possible to prevent the accumulation of paper powder due to static electricity generated when reading an original, and to prevent the destruction of the semiconductor element due to static electricity.

When an LED is used as the light emitting body, in the embodiment shown in FIG. 1, the distance between the original and the light emitting body is too close, and the illuminance difference between the vicinity of the light emitting body and the position away from the light emitting body is large, and the light amount is large. 3 is more preferable because the unevenness of 2 is too large.

Although the present invention has been described with respect to a color image input device whose demand will increase in the future, if the color of the light source is selected,
It can also be applied to a one-point color image input device of black and white (for example, white or green light source color) or only a few colors (for example, red or blue).

Further, the embodiment has been mainly described by taking the fluorescent display tube as an example for the reason that it can emit three colors as a light source, has a relatively low voltage, has high reliability, and has a fast response speed. Even if a light source in which LEDs, EL, etc. are arranged on the base substrate so as not to cover the field of view of the converging rod lens array is used as the body, the great effects of the present invention can be obtained.

[0035]

As described above, according to the present invention, the following great effects are brought about.

1) The light source is arranged between the document reading surface and the lens, and the document surface is imaged by the converging rod lens array, thereby reducing the size of the light source and the image input device.

2) Since the surface of the original can be efficiently irradiated with the light emitted from the light source, the dynamic range of the solid-state image pickup device can be widely used and the speed can be increased.

3) Further, since the light emission brightness of the light source can be reduced by increasing the illumination efficiency, it is possible to reduce the power consumption of the light source.

4) By using a fluorescent display tube,
A compact, high-brightness emission, uniform emission, and highly reliable color image input device can be obtained by emitting three colors of green and blue.

5) Since the converging rod lens array is used as a lens, it is possible to provide an image input device which achieves the above-mentioned effects without disposing a light shielding layer on the optical axis.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a contact image input device of the present invention.

FIG. 2 is a cross-sectional view of a fluorescent display tube used as a light source in the image input device of the present invention.

FIG. 3 is a sectional view of another contact-type image input device of the present invention.

FIG. 4 is a diagram showing the spectral sensitivity of an amorphous photodiode.

FIG. 5 is a cross-sectional view of a reduction optical system image input device.

FIG. 6 is a configuration diagram showing a conventional color image input device.

FIG. 7 is a configuration diagram showing a conventional contact-type image input device.

[Explanation of symbols]

 11. Manuscript 12. Light source 13. Focusing rod lens array 14. Solid-state image sensor 21. Focusing rod lens array 22. Anode electrode (phosphor) of fluorescent display tube 23. Cathode electrode (filament) of a fluorescent display tube 24. Cover glass 25. Base substrate 26. Terminal 31.51.61.71. Manuscript 32.53.62.72. Light source 33.73. Focusing Rod Lens Array 34.54.64.74. Solid-state image sensor 52.63. Reduction lens 56. Shading layer

Claims (3)

[Claims] 1. An image input device comprising an optical system for picking up an image of a document surface, a photoelectric conversion element arranged on an image forming surface of the optical system, and a light source for illuminating the document surface, wherein the optical system is the light source. An image input device, which is a converging rod lens array that captures an image of a document surface through a light emitter inside. 2. The image input device according to claim 1, wherein the base substrate on which the light emitter of the light source is arranged is a document reading surface. 3. The image input device according to claim 1, wherein the light source is a fluorescent display tube, and the base substrate or the cover glass serves as a document reading surface.