JPH11219687A - Fluorescent lamp, solid image pickup element and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lamp capable of reading invisible information by sealing gas in a tubular transparent member, and coating the inner face of the transparent member with a mixed phosphor mixed with an ultraviolet phosphor luminescing in an ultraviolet ray band and a visible light phosphor luminescing in a visible light band. SOLUTION: The inner face of a circular tube is coated with a phosphor 64 at a uniform thickness. The light in the prescribed wavelength range is generated by sealed gas 63 via a discharge between two electrodes 62, the light stimulates the phosphor 64, and the phosphor 64 generates the light corresponding to its component. The phosphor 64 is mixedly constituted of phosphors emitting the light of B, G, R, U respectively via the luminescence of the sealed gas 63. The luminescent energy characteristics of the B, G, R, U phosphors are already known, and various combinations can be made. A light transmitting material is preferably made of a material easily transmitting ultraviolet rays to guide the generated ultraviolet rays to a line sensor more effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a fluorescent lamp and a solid-state image pickup device used in a copying machine, a scanner, and the like, and an image reading apparatus such as a copying machine or a scanner provided with the same.

[0002]

2. Description of the Related Art Some fluorescent lamps for illuminating a document in a color copying machine or a color scanner use a single phosphor which emits white light (a wide emission wavelength band). The thing using the phosphor which mixed the body is also used. The latter phosphor is mixed with phosphors that respectively emit blue (B), green (G), and red (R) light.

[0003]

However, in recent years, as disclosed in JP-A-7-30696, a recording method for embedding coded digital information in image data and a recording method using the same have been developed. ing. To print data recorded in this manner, the image data is reproduced with visible toner or ink, and the coded digital information reflects visible light and ultraviolet light to maintain the quality of the visible image. It is desirable to reproduce with an invisible toner or ink that absorbs. However, it has not been possible to read printed matter printed in this manner.

The present invention has been made in view of the above circumstances, and has as its object to provide a fluorescent lamp, a solid-state imaging device, and an image reading device capable of reading invisible information.

[0005]

In order to solve the above-mentioned problems, a fluorescent lamp according to the present invention comprises a tubular transparent member, a gas sealed in the transparent member, an ultraviolet phosphor emitting light in an ultraviolet band, and a visible light. And a mixed phosphor mixed with a visible light phosphor that emits light in an optical band and coated on an inner surface of the transparent member. Thus, not only visible light but also ultraviolet light can be emitted from the same fluorescent lamp.

In this fluorescent lamp, light in an ultraviolet band equal to or higher than the light transmission frequency of a light transmitting member disposed in an optical path from the phosphor in the fluorescent lamp to a reading element for reading light emitted from the fluorescent lamp is transmitted. The ultraviolet phosphor may emit light. In an image reading apparatus, a light transmitting member such as a platen glass, an infrared absorption filter, and an imaging lens is generally disposed in an optical path between a light source and a reading element. In a fluorescent lamp as a light source, the mixed phosphor is applied to an inner surface of the transparent member as a light transmitting member. The light emitted from the ultraviolet phosphor does not reach the reading element unless it passes through these light transmitting members. Light transmitting members that can be mass-produced industrially are more difficult to transmit as ultraviolet light having a shorter wavelength. Therefore, it is preferable that the ultraviolet phosphor emits light in the ultraviolet band equal to or higher than the light transmission frequency of the light transmitting member. In order to efficiently transmit the ultraviolet light to the reading element through the light transmitting member efficiently, it is preferable that the emission wavelength of the ultraviolet fluorescent material is 300 nm or more. Further, it is more preferable that the emission wavelength of the ultraviolet fluorescent material is 350 nm or more. Further, because of the irradiation of ultraviolet rays in a wide wavelength band, the half-value width across the emission wavelength peak of the ultraviolet phosphor is 2
It is preferable that it is 0 nm or more.

A solid-state image pickup device according to the present invention is characterized in that a plurality of photosensitive pixels capable of reading visible light and a plurality of photosensitive pixels capable of reading ultraviolet light are arranged. Thereby, not only visible light but also ultraviolet light can be read by the same solid-state imaging device.

Further, an image reading apparatus according to the present invention includes the above-mentioned fluorescent lamp, and the above-mentioned solid-state imaging device which reads light reflected by a document from light emitted from the above-mentioned fluorescent lamp. With the above structure, information provided by invisible toner or ink that absorbs ultraviolet light can be read.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1. First Embodiment 1-1: Outline of Image Reading Device FIG. 1 shows an image reading device provided with a fluorescent lamp according to an embodiment of the present invention. Cabinet 1 of this image reading device
A platen glass 2 having a flat plate shape is provided at the upper part of the document, and the original 3 is placed on the platen glass 2 with its image surface facing downward. A known platen cover (not shown) presses the document 3 toward the platen glass 2.

Inside the cabinet 1, a full rate carriage 4 and a half rate carriage 5 are arranged so as to be movable in the horizontal direction. The full-rate carriage 4 has a fluorescent lamp 6 for irradiating the original 3 and a reflecting mirror 7 mounted thereon, and the half-rate carriage 5 has two reflecting mirrors 8 and 9.
Is installed. The fluorescent lamp 6 and the reflecting mirrors 7, 8, and 9 extend in a direction perpendicular to the plane of FIG.

An original reading unit 10 is arranged at a fixed position inside the cabinet 1. The document reading unit 10 includes an infrared absorption filter 11, an imaging lens 12, a line sensor 13 composed of a number of photosensitive pixels, and a unit housing 14 containing these.
Is provided.

The light emitted from the fluorescent lamp 6 passes through the platen glass 2 and is reflected on the lower surface of the document 3. The reflected light from the original 3 is transmitted through the platen glass 2, reflected by the reflecting mirrors 7 to 9, and further transmitted by the imaging lens 12 to the line sensor (solid-state imaging device) 13 extending in the direction perpendicular to the plane of FIG. 1. Form an image. In this process, a long wavelength infrared component is removed from the reflected light by passing through the infrared absorption filter 11. FIG. 2 shows the spectral transmittance characteristics of the infrared absorption filter 11. The full-rate carriage 4 moves in the horizontal direction so that the entire surface of the document 3 is illuminated by the fluorescent lamp 6, and the half-rate carriage 5 moves at half the speed of the full-rate carriage 4 so that the line sensor The length of the reflected light path reaching 13 is kept constant.

The line sensor 13 is a CCD. As shown in FIG. 3, four types of photosensitive pixels 13B, 13G, and 13 are provided.
R and 13U are arranged in a large number with regularity. The horizontal direction in FIG. 3 corresponds to the direction perpendicular to the plane of FIG. Each of the photosensitive pixels is provided with one of four types of color filters. The photosensitive pixel 13B reads blue, the photosensitive pixel 13G reads green, the photosensitive pixel 13R reads red, and the photosensitive pixel 13U reads ultraviolet light.

In FIG. 3, the photosensitive pixels 13B, 13G, 13
The photosensitive pixels are arranged in four columns so that one of R and 13U is assigned to one column. However, the mutual arrangement of the photosensitive pixels 13B, 13G, 13R, and 13U is not limited to the four rows as shown in the drawing as long as there is regularity. For example, all of these four types may be arranged in one row, or four types may be arranged in two rows as shown in FIG.

A gate 30 is located near the line sensor 13.
B, 30G, 30R, 30U and CCD register 31
B, 31G, 31R, and 31U are arranged. The electric charge generated in the photosensitive pixel 13B is transferred to the corresponding CCD register 31B through the corresponding gate 30B. Similarly, electric charges generated in the photosensitive pixels 13G, 13R, and 13U are transferred to the corresponding CCD registers 31G, 31R, and 31U through the corresponding gates 30G, 30R, and 30U.

The CCD registers 31B, 31G, 31R,
Of the 31Us, those of the same type constitute a series of register channels 33B, 33G, 33R, 33U. The register channels 33B, 33G, 33R, 33U have amplifiers 34B, 34G, 34R, which amplify charges generated from the corresponding photosensitive pixels 13B, 13G, 13R, 13U.
34U are respectively connected.

The image of the original is read by the line sensor 13 as follows. First, the reflected light from the original 3 enters the photosensitive pixels 13B, 13G, 13R, and 13U. Next, after the charge for one line in the main scanning direction is integrated, the photosensitive pixels 13B, 13G, 13R, and 13U are integrated.
Gates 30B, 30G, 30R, 30
U and the corresponding CCD registers 31B, 31G,
Transferred to 31R, 31U. Thereafter, control clock pulses are applied to the register channels 33B, 33G, 33.
R, 33U CCD registers 31B, 31G, 31R,
31U are applied in a predetermined order. Then, each amplifier 3
4B, 34G, 34R and 34U, each photosensitive pixel 13
The charges of B, 13G, 13R, and 13U are output in parallel in the main scanning direction. Thus, reading in the main scanning direction is performed.

The reading in the sub-scanning direction is completed by repeating the reading in the main scanning direction during the scanning of the carriages 4 and 5. Thus, the reading of the entire surface of the document is performed.

Each photosensitive pixel 13B, 1 of the line sensor 13
Each color filter provided in 3G, 13R, and 13U has characteristics shown in FIG. The curves (broken lines, two-dot chain lines, one-dot chain lines, and solid lines) indicated by B, G, R, and U in the figure are the spectral transmittances of the filters of the photosensitive pixels 13B, 13G, 13R, and 13U, respectively, that is, the photosensitive pixels 13B, 13G, 13
R and 13U represent the respective spectral sensitivities. In FIG. 5, the peak of the spectral sensitivity of the photosensitive pixel 13R having the highest peak is 1
Relativized as 00%. Thus, the line sensor 1
No. 3 is capable of reading a wide wavelength band from ultraviolet to visible light to near infrared.

FIG. 6 shows a part of an image processing system for color image data read by the line sensor 13. The imaging optical system 23 in the drawing is a concept including the reflecting mirrors 7, 8, and 9, the infrared absorption filter 11, and the imaging lens 12. As shown in FIG. 6, four types (B, G, R, U) of read image signals generated by the line sensor 13 are amplified by an amplifier 20, and then are converted into four types of digital signals by an A / D converter 21. It is converted to an image signal. The digital image signal is supplied to the correction processing unit 22, and the correction processing unit 22 performs a predetermined correction process on the digital image signal. Thereafter, the digital image signal is transmitted to the outside.

This image reading apparatus may be a stand-alone scanner or may be attached to a copying machine. In the case of a stand-alone system, a digital image signal is transmitted to a computer (not shown), which performs analysis and correction while displaying the image on the display, and records the digital image signal on a storage medium such as a floppy disk or digital versatile disk. Or you can. In this way, display, analysis, correction and recording of a color image including an ultraviolet image can be realized.

When the image reading apparatus is attached to a copying machine, the above four types of digital image signals are supplied to an image forming signal generating section. In this image forming signal generation unit, B, G, R
The digital image signal of black (B)
k), yellow (Y), magenta (M), cyan (C)
, Or three types of image forming signals of Y, M, and C, while digital image signals related to ultraviolet (U) are not converted.

If the copying machine is an electrophotographic system, Bk,
Five types of signals of Y, M, C, and U or four types of signals of Y, M, C, and U are sent from the image forming signal generation unit to the latent image writing device (R
The ROS irradiates light onto the surface of an image carrier such as a photosensitive drum to write a latent image in response to these signals. These latent images are visualized by five kinds of toners Bk, Y, M, C and U or four kinds of toners of Y, M, C and U supplied from a developing device, and the visualized images are transferred to a sheet. Is done.

If the copying machine is an ink type, Bk, Y,
Five kinds of signals of M, C, U or four kinds of signals of Y, M, C, U are supplied to a controller of the copying machine, and the controller operates an ink supply unit to generate Bk, Y, M, C ,
An image is formed on a sheet using five types of U or four types of inks of Y, M, C, and U. Thus, a color image including an ultraviolet image is formed.

1-2. Phosphor of Fluorescent Lamp In order to read an ultraviolet image with the photosensitive pixels 13U of the line sensor 13 as described above, it is essential that the fluorescent lamp 6 as a light source emits ultraviolet light. Next, the fluorescent lamp 6 used in this embodiment will be described.

As shown in FIGS. 7 and 8, the fluorescent lamp 6 comprises a circular tube 60 made of a transparent material, specifically, glass or quartz, and a base 61 for sealing both ends of the circular tube 60 in a gas-tight manner. And electrodes 62 respectively provided on the base 61
(Only one of the two is shown). A sealing gas 63 that is an inert gas such as argon or xenon or a mercury gas is sealed in the inside of the circular tube 60.

The inner surface of the circular tube 60 is coated with a phosphor 64 with a uniform thickness. Due to the discharge between the two electrodes 62, light in a predetermined wavelength range is generated in the sealing gas 63, and this light stimulates the phosphor 64, whereby the phosphor 64 generates light corresponding to the component.

The phosphor 64 is formed by mixing phosphors which emit B, G, R, and U light at a predetermined ratio by the light emission of the above-described filling gas 63. B,
The emission energy characteristics of each of the phosphors G, R, and U are shown in FIGS. 9 is blue (B), FIG. 10 is green (G),
FIG. 11 corresponds to red (R), and FIG. 12 corresponds to ultraviolet (U). The phosphor shown in FIG. 13 may be used instead of or in addition to the phosphor U shown in FIG. The phosphor of FIG. 12 has a peak of emission energy at a wavelength of about 370 nm, and the half width across the peak is about 20 nm, whereas the phosphor of FIG. 13 has a peak of emission energy at a wavelength of about 350 nm. Yes, the half width around the peak is about 5
0 nm.

In general, glass is difficult to transmit ultraviolet light, but ordinary glass can transmit ultraviolet light having a wavelength of 350 nm or more, and special glass and the like can transmit even lower ultraviolet light. Circle tube 6 of fluorescent lamp 6
0 is made of glass, and as shown in FIG.
The platen glass 2 and the imaging lens 12 are disposed in the optical path from the light source to the line sensor 13, and the ultraviolet light shown in FIGS. 2 and imaging lens 12)
Can be transmitted to the line sensor 13 even if it is ordinary glass.

In order to allow the generated ultraviolet rays to reach the line sensor 13 more effectively, it is preferable that these light transmitting members are made of a material that easily transmits the ultraviolet rays. For example, the lower limit of the transmission wavelength of special glass containing less than 0.01% of iron oxide is 200 nm, and that of special quartz is 160 n.
m.

As shown in FIG. 2, the infrared absorption filter 1
In No. 1, the transmittance at a wavelength of 300 nm is about 50%, and the light emitted from the fluorescent lamp 6 can be transmitted. Further, as shown in FIG.
The transmittance at 0 nm is 30% or more. In view of these,
The emission wavelength of the U phosphor is preferably 300 nm or more, and more preferably 350 nm or more. The phosphor of U shown in FIGS. 12 and 13 satisfies these conditions.

FIG. 15 shows the emission energy characteristics of the fluorescent lamp 6 coated with the phosphor 64 obtained by mixing the phosphors of FIG. 9B, FIG. 10G, FIG. 11R, and FIG. Show. Mercury was used as the filling gas 63. In FIG.
The peak of the highest light emission energy was set to 100% and relativized. As is apparent from FIG. 5, the fluorescent lamp 6 has energy in the ultraviolet wavelength band.

For comparison, FIGS. 16 to 19 show emission distribution characteristics of a conventional fluorescent lamp. 16 and 17
Each of the phosphors shown in FIG. 2 is a mixture of B, G, and R phosphors. FIGS. 18 and 19 show the characteristics of a single phosphor having a very wide emission band. FIG.
6, mercury was used as the filling gas in the measurements of FIGS. 18 and 19, and xenon was used as the filling gas in the measurements of FIG. In FIGS. 16, 18 and 19, about 310 n in the ultraviolet band due to the emission of mercury gas.
There are emission energy peaks at m and about 370 nm. Compared with the emission energy peaks of the B, G, and R phosphors, the ultraviolet light peak is small, the ultraviolet light emission wavelength band is very narrow, and the energy is small. .

On the other hand, as shown in FIG. 15, in the phosphor 64 of the present embodiment, an ultraviolet light emission peak equivalent to the visible light emission energy peak is obtained at a wavelength of about 370 nm. Also, the wavelength band of ultraviolet light emission is wide,
The curve of that band is also gentle.

In the measurements of FIGS. 16, 18 and 19, mercury gas which emits light in the ultraviolet band is used.
The fluorescent lamp 6 of the present embodiment used for the measurement in FIG. 15 has a higher characteristic than the conventional fluorescent lamp because the peak of ultraviolet rays is large, the emission wavelength band is wide, and the energy is large as described above. .

As is apparent from the above description, the fluorescent lamp 6 according to the present embodiment using the phosphor emitting ultraviolet light.
To illuminate the original 3 with the use of a photosensitive pixel 1 for sensing ultraviolet rays
By reading the reflected light with the line sensor 13 having 3U, it is possible to read information provided on the document 3 with an invisible toner or ink that absorbs ultraviolet light. In the present embodiment, mercury is used as the sealing gas 63, but the present invention is not limited to this, and another sealing gas such as xenon or argon may be used.

The emission wavelength characteristic can be changed by changing or adding a phosphor that emits ultraviolet light.
For example, in the fluorescent lamp 6 of the present embodiment used for the measurement of FIG. 15, since the phosphor of U of FIG. 12 is used, the peak of the emission energy in the ultraviolet band is about 370 nm.
On the other hand, since the phosphor of U in FIG. 13 has a peak of the emission energy at a wavelength of about 350 nm, if this phosphor is used for the fluorescent lamp 6, the peak of the emission energy in the ultraviolet band is considered to be about 350 nm. FIG.
It is considered that the use of both U phosphors in FIG. 13 and FIG.

2. Second Embodiment Next, a second embodiment of the present invention will be described. The phosphor 64 of the fluorescent lamp 6 of the first embodiment is composed of four kinds of phosphors of B, G, R, and U, but in this embodiment, B, R, and A phosphor 64 obtained by adding a yellow-white (YW) phosphor to three kinds of U phosphors was used. YW
The purpose of adding the phosphor is to solve the following problems of the prior art.

In the emission of the conventional fluorescent lamp in the visible light band, the emission band may be narrow and the energy may be significantly lower at a specific wavelength. For example, in the fluorescent lamps shown in FIGS. 16 and 17, the emission energy is extremely low at a wavelength of 570 nm, the wavelength bands of green and red emission are extremely narrow, and the curves corresponding to those bands are sharp. Therefore, a remarkable difference may occur between the color of the document and the color reproduced by a color copying machine or a color scanner. These drawbacks were particularly noticeable in fluorescent lamps containing xenon.

Therefore, according to the technique described in Japanese Patent Application Laid-Open No. Hei 2-201439, B, G, and R phosphors each having a relatively wide emission wavelength band are selected, the mixing ratio of these phosphors is adjusted, and copying is performed. It improves the color reproducibility of machines and scanners. However, even with this technology, the curves corresponding to the wavelength bands of green and red light emission are sharp,
There is a limit in improving color reproducibility.

In a fluorescent lamp in which mercury is enclosed, a single phosphor having a wide emission wavelength band can be selected as shown in FIGS. 17 and 18. However, in a fluorescent lamp in which xenon is enclosed, xenon is used. Since there are few types of phosphors that emit light in accordance with the light emission, there is little room for selection of the emission peak wavelength and emission wavelength band. Therefore, the problem that the emission energy is extremely low at a specific wavelength, for example, 570 nm, cannot be solved.

Therefore, in this embodiment, not only the U phosphor capable of reading ultraviolet light but also the YW phosphor having the emission wavelength characteristic shown in FIG.
Light emission in a wide wavelength band was secured, and the curve of the emission wavelength distribution of the phosphor 64 was moderated. Thereby, the color reproducibility is improved as described later. Note that the overall configuration of the image reading apparatus is the same as that of the first embodiment.

As shown in FIG. 20, the phosphor emitting YW has the highest peak at 580 nm and 470 nm.
It has the second highest peak in nm. Specifically, this phosphor is composed of calcium halophosphate and trace amounts of Mn and Tb.

The mixing ratio of the B, R, YW and U phosphors is determined so as to satisfy the following two conditions. (1) Register channels 33U, 33B, 33G, 3 in line sensor 13 when phosphor 64 emits light.
The output voltage ratio from the 3R is a predetermined target value, for example, 1: 1:
1: 1 or 0.5: 0.8: 1: 0.8. (2) The colorimetric quality coefficient q becomes a target value. For example, each of the colorimetric quality coefficients qB, qG, qR by the photosensitive pixels 13B, 13G, 13R related to visible light should be close to 1.

Here, the colorimetric quality factor q is an index of the overall color reproducibility of an image reading apparatus including a light source, an optical system, and a sensor. The overall spectral sensitivity characteristic (A) of the image reading apparatus when reading light incident on the sensor via an optical system including an infrared absorption filter and an imaging lens is determined by natural light (color temperature of 50
It shows the degree of conformity with the spectral sensitivity characteristic (B) when (a light of a standard light source of 00K) is read by the naked eye of a human. For example, in a certain image reading apparatus, if the spectral sensitivity characteristics of B, G, and R match the overall spectral sensitivity characteristics that a human recognizes in the B, G, and R wavelength regions with respect to natural light, the colorimetric quality can be improved. Coefficients qB, qG, qR each become 1. It should be noted that ultraviolet light is invisible to humans and therefore has no relation to the colorimetric quality factor q.

The spectral sensitivity characteristic (A) of the image reading device is obtained as follows. First, the spectral sensitivity characteristic A _{Blue for} blue is the product of the spectral energy of light emission of the light source and the spectral reflectance and spectral transmittance of an optical system (including a light transmitting member such as an infrared absorption filter) for the blue wavelength band. It is obtained by multiplying by the spectral sensitivity of the blue photosensitive pixel 13B of the line sensor 13. Similarly, spectral sensitivity characteristics A _Green about green
Is the product of the spectral energy of light emission of the light source, the spectral reflectance and spectral transmittance of an optical system (including an infrared absorption filter) relating to the green wavelength band, and the spectral sensitivity of the green photosensitive pixel 13G of the line sensor 13. It is obtained by multiplying. Further, the spectral sensitivity characteristic A _{Red for} red is a product of the spectral energy of light emission of the light source, the spectral reflectance or spectral reflectance of an optical system (including an infrared absorption filter) for the red wavelength band, and the red color of the line sensor 13. Is multiplied by the spectral sensitivity of the photosensitive pixel 13R.

On the other hand, the spectral sensitivity characteristic (B) of the human naked eye can be obtained as follows. First, the spectral sensitivity characteristic B _Blue regarding blue is the product of the spectral energy of light emission of the standard light source and the spectral sensitivity (stimulus value) of the human naked eye to blue light emission. Similarly, the spectral sensitivity characteristic B for green
_Green is the product of the spectral energy of the emission of the standard light source and the spectral sensitivity of the human eye to the green emission. Also,
The spectral sensitivity characteristic B _Red for red is the product of the spectral energy of light emission of the standard light source and the spectral sensitivity of the human naked eye to red light emission.

The spectral sensitivity to be evaluated is defined as S (λ),
F ₁ (λ), F ₁ (λ)
Assuming ₂ (λ) and F ₃ (λ), the colorimetric quality factor q can be obtained from the following equation.

(Equation 1) Here, the definite integration (∫ _vis ) is performed in the visible wavelength range.

It is ideal that the colorimetric quality coefficients qB, qG, qR be 1. However, since it cannot be realized by an actual image reading apparatus, it is desirable that the colorimetric quality coefficients be 0.8 or more. The phosphor 64 mixed so as to satisfy these conditions is applied to the inner surface of the circular tube 60 through a general process.

FIG. 21 shows the emission characteristics of the fluorescent lamp 6 using the phosphor 64 obtained by mixing the above-mentioned phosphors of B, G, R, YW and U at a predetermined ratio. The U phosphor of the phosphor 64 corresponds to FIG. Xenon was used as the filling gas 63. Regarding the phosphor 64, the phosphor 64
The ratio of output voltages from the register channels 33U, 33B, 33G, and 33R in the line sensor 13 when the light was emitted was 0.5: 0.8: 1: 0.8. As can be seen from the figure, in this embodiment, the emission energy is distributed over the entire visible light region, and there is no wavelength with a remarkably low energy. And the curve with visible light is gentle,
The peak energy is also relatively small.

FIG. 22 is a table showing the colorimetric quality factor q of the conventional fluorescent lamp showing the emission energy characteristics shown in FIG. 17 and FIG. 23 is a table showing the colorimetric quality factor q of the fluorescent lamp 6 of the present embodiment. It is a table shown. Conventionally, qG and qR
Was below 0.8, and the reproducibility of green and red was poor. On the other hand, according to the present embodiment, all the colorimetric quality coefficients qB, qG, and qR exceed 0.85, indicating very good characteristics. For the above reasons, according to the fluorescent lamp 6 of the present embodiment, it is possible to improve color reproducibility.

As is clear from FIG. 21, the phosphor 64 of the present embodiment also has an ultraviolet emission peak equivalent to the visible light emission energy peak at a wavelength of about 370 nm. Further, the wavelength band of ultraviolet light emission is wide, and the curve of the band is gentle. Therefore, similarly to the first embodiment, it is possible to read information provided on the document 3 with an invisible toner or ink absorbing ultraviolet rays.

In this embodiment, the line sensor 1
3, the components of the phosphor 64 were adjusted so that the output voltage ratio became 0.5: 0.8: 1: 0.8. However, the present invention is not limited to this, and the functions and properties of the image reading apparatus In response to,
It may be changed as appropriate. The output voltage ratio of the line sensor 13 can be changed by adjusting the mixing ratio of the phosphors 64.

[0054]

As described above, according to the present invention,
It is possible to read information provided by invisible toner or ink that absorbs ultraviolet light.

[Brief description of the drawings]

FIG. 1 is a side view showing an image reading apparatus according to the present invention.

FIG. 2 is a graph showing a spectral transmittance characteristic of an infrared filter of the image reading apparatus of FIG.

FIG. 3 is a diagram illustrating an example of a line sensor that is a solid-state imaging device used in the image reading device of FIG. 1;

FIG. 4 is a diagram illustrating another example of the line sensor used in the image reading apparatus of FIG. 1;

FIG. 5 is a graph showing spectral sensitivity characteristics of each photosensitive pixel of the line sensor.

FIG. 6 is a block diagram illustrating a reading system of the image reading apparatus of FIG. 1;

FIG. 7 is a partially cutaway side view showing a fluorescent lamp according to the present invention.

FIG. 8 is a sectional view of the fluorescent lamp of FIG. 7;

FIG. 9 is a graph showing emission energy characteristics of a blue phosphor mixed with the phosphor of the fluorescent lamp according to the first embodiment of the present invention.

FIG. 10 is a graph showing emission energy characteristics of a green phosphor mixed with the phosphor.

FIG. 11 is a graph showing emission energy characteristics of a red phosphor mixed with the phosphor.

FIG. 12 is a graph showing emission energy characteristics of an example of an ultraviolet phosphor mixed with the phosphor.

FIG. 13 is a graph showing emission energy characteristics of another example of an ultraviolet phosphor mixed with the phosphor.

FIG. 14 is a graph showing a spectral transmittance characteristic of an imaging lens of the image reading device of FIG. 1;

FIG. 15 is a graph showing emission energy characteristics of the phosphor according to the first embodiment in which the phosphors of FIGS. 9 to 12 are mixed.

FIG. 16 is a graph showing emission energy characteristics of a conventional mixed phosphor.

FIG. 17 is a graph showing emission energy characteristics of another conventional mixed phosphor.

FIG. 18 is a graph showing emission energy characteristics of a conventional single phosphor having a wide emission wavelength band.

FIG. 19 is a graph showing emission energy characteristics of another conventional single phosphor having a wide emission wavelength band.

FIG. 20 is a graph showing emission energy characteristics of a yellow-white phosphor mixed with a phosphor of the fluorescent lamp according to the second embodiment of the present invention.

FIG. 21 is a graph showing emission energy characteristics of the phosphor according to the second embodiment in which the phosphors of FIGS. 9, 11, 12 and 20 are mixed.

FIG. 22 is a table showing a colorimetric quality factor q of an image reading apparatus using a conventional mixed phosphor.

FIG. 23 is a table showing a colorimetric quality factor q of the image reading apparatus using the mixed phosphor according to the second embodiment of the present invention.

[Explanation of symbols]

3 original, 6 fluorescent lamp, 7, 8, 9 reflector, 10 mirror
Document reading unit, 11 ... infrared absorption filter, 12 ...
Imaging lens, 13 ... Line sensor, 13B, 13G, 13
R, 13U: photosensitive pixel, 60: circular tube. 62 ... electrode, 63
... filled gas, 64 ... phosphor

Claims (6)

[Claims] 1. A tubular transparent member, a gas sealed in the transparent member, an ultraviolet phosphor emitting in an ultraviolet band and a visible light phosphor emitting in a visible light band are mixed, and an inner surface of the transparent member is mixed. And a mixed phosphor applied to the fluorescent lamp. 2. An ultraviolet fluorescent light having a frequency equal to or higher than a light transmission frequency of a light transmitting member disposed in an optical path from the phosphor in the fluorescent lamp to a reading element for reading light emitted from the fluorescent lamp. The fluorescent lamp according to claim 1, wherein the body emits light. 3. An emission wavelength of the ultraviolet phosphor is 300 n.
The fluorescent lamp according to claim 1, wherein the distance is at least m. 4. A plurality of photosensitive pixels capable of reading visible light,
A solid-state imaging device, wherein a plurality of photosensitive pixels capable of reading ultraviolet rays are arranged. 5. The fluorescent lamp according to claim 1, wherein light emitted from the fluorescent lamp is reflected by a document and read.
An image reading apparatus comprising: the solid-state imaging device according to claim 4. 6. The ultraviolet phosphor emits light in an ultraviolet band equal to or higher than a light transmission frequency of a light transmission member disposed in an optical path from the phosphor in the fluorescent lamp to the solid-state imaging device. The image reading device according to claim 5, wherein