JPH10285341A - Light source and image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve color reproducibility. SOLUTION: A fluorescent material with luminescent colors blue B, red R, green G and a fluorescent material with a luminescent color yellow Y are blended at a prescribed ratio, and the blended material is coated on an inner wall face of a fluorescent lamp 3. An active phosphorous vanadate with dysprosium -Y(P,V)O4 : Dy- is adopted for the fluorescent material with a luminescent color yellow Y, where a peak exists around a wavelength of 570 nm. The colorimetric quality coefficients qB, qG, qR are all 0.8 or over, since the result and the color reproducibility is improved. A light emitted from the fluorescent lamp 3 is emitted onto an original face. The light, reflected in the original face forms its image on a color linear image sensor 9 through a 1st reflecting mirror 4 to a 3rd reflecting mirror 6, an infrared ray elimination filter 7 and a lens 8. The formed image is converted into an electric signal and fed to a processing system of the post-stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a light source and an image reading apparatus formed by mixing phosphors having a plurality of emission colors.

[0002]

2. Description of the Related Art Conventionally, in a scanner for reading a color original, a copying machine for copying a color original, and the like, red (red) R, green (green) G, blue (blue) A) A fluorescent lamp formed by mixing phosphors (plurality) having the emission color of B is used. In such an image reading apparatus such as a scanner or a copying machine, the spectral distribution of the spectral energy characteristic that determines the emission color of the fluorescent lamp as a light source is an important factor for more faithfully reproducing the color of a color original. It has been known. Therefore, how to control the emission color of the fluorescent lamp, that is, what kind of spectral distribution of the spectral energy characteristic is a point for improving the color reproducibility.

[0003]

FIG. 12 is a view showing the spectral energy characteristics of a conventional three-wavelength fluorescent lamp in which mercury is sealed, and FIG. 13 is a conventional xenon fluorescent lamp in which xenon gas is sealed. FIG. 4 is a diagram illustrating spectral energy characteristics of a lamp. As shown in FIGS. 12 and 13, none of the fluorescent lamps emit light having a wavelength near 570 nm. The spectral characteristics of red (red) R and green (green) G have sharp spectral characteristics with a narrow band. Therefore, when this is used as a light source, there is a problem that a color shift occurs between a color reproduced when a color original is read and reproduced and the color of the original color original. This is because, in the fluorescent lamp of the prior art, the phosphor (blue B) having a narrow bandwidth and having the spectral energy characteristic shown in FIG. 14A and the phosphor (red) having the spectral energy characteristic shown in FIG. R) and a phosphor (green G) having the spectral energy characteristic shown in FIG. 14 (c).

Therefore, for example, Japanese Patent Application Laid-Open No. 2-201439
In this publication, a fluorescent substance having a spectral energy characteristic having a relatively wide bandwidth is used so that the spectral energy characteristic of the fluorescent lamp matches the spectral sensitivity characteristic of the naked eye, and the fluorescent light for each of blue B, red R and green G is used. A technique for improving color reproducibility by setting the mixture ratio of the body to a predetermined value is disclosed. However, in the above prior art, the peak wavelength or the bandwidth for each of blue B, red R, and green G cannot be freely selected, so that there is a limit in improving color reproducibility, and as a result, the wavelength is 570 nm.
There is a problem that it is not possible to increase light emission in the vicinity. Further, since the conventional phosphor has sharp peaks in the wavelength region of green G and the wavelength region of red R, when this is used as a light source, the reproduced color when reading and reproducing a color document and the original color document can be obtained. There is a problem that a color misregistration occurs between the color and the color.

The wavelength 57 in the spectral energy characteristic
In order to increase the light emission near 0 nm, for example, FIG.
It is conceivable that the position or the bandwidth of the peak wavelength of the green phosphor shown in FIG. 14C or the red R phosphor shown in FIG. However, in particular, in a xenon fluorescent lamp, there is no known phosphor having a wide bandwidth among phosphors having a red R emission color. 147 nm of xenon gas
There is no known green G phosphor which is excited by the energy ray and has an emission peak near 550 nm and does not have a sharp peak. For this reason, even if the phosphor of green G is changed to a phosphor having a wider bandwidth, at least in the currently known range, the spectral energy characteristic finally obtained is as shown in FIG. There is a problem that the emission near 570 nm cannot be sufficiently increased.

The present invention has been made in view of the above circumstances, and has as its object to provide a light source and an image reading device capable of improving color reproducibility.

[0007]

According to the first aspect of the present invention, there is provided a transparent member in which an inert gas is sealed, and a transparent member provided in the transparent member, wherein red and green are provided. Three phosphors that emit fluorescent colors corresponding to each of blue, and a fluorescent light that is provided inside the transparent member and emits a fluorescent color that increases at least one of the red, green, and blue colorimetric coefficients. And a color coefficient improving phosphor.

[0008] According to the second aspect of the present invention, in the first aspect,
The light source as described above, wherein the colorimetry enhancing phosphor has a yellow fluorescent color.

According to the third aspect of the present invention, the first aspect is provided.
The light source according to claim 1, wherein the inert gas is xenon gas.

[0010] According to the fourth aspect of the present invention, in the first aspect,
In the light source described above, the colorimetric coefficient improving phosphor is a dysprosium-activated phosphor vanadate phosphor, Y (P, V)
O ₄ : Dy ”.

Further, according to the invention described in claim 5, according to claim 1,
The light source as described above, wherein the colorimetric coefficient improving phosphor has a peak emission wavelength at least in a range of 560 to 590 nm.

In order to solve the above-mentioned problems,
According to a sixth aspect of the present invention, there is provided a fluorescent lamp for irradiating an original with light emitted from a phosphor, and reading means for reading an image of the original illuminated by the fluorescent lamp, wherein the fluorescent lamp is red or green. And three phosphors that emit blue fluorescent color and a colorimetric coefficient improving phosphor that emits a fluorescent color that increases at least one of the red, green, and blue colorimetric coefficients. Features.

Further, according to the present invention, a transparent member filled with an inert gas, a fluorescent member provided inside the transparent member and emitting a fluorescent color corresponding to blue and a fluorescent member corresponding to yellow are provided. A mixed phosphor obtained by mixing two or more phosphors including a phosphor emitting a color so as to increase at least one of the red, green, and blue colorimetric coefficients. .

Further, according to the invention described in claim 8, according to claim 7,
In the light source described above, the phosphor emitting a fluorescent color corresponding to the yellow color has a peak emission wavelength of 545 nm to 58 nm.
It is in the range of 5 nm and has a half width of 90 nm to 150 nm.
nm.

According to the ninth aspect of the present invention, the seventh aspect of the present invention is provided.
In the light source described above, the phosphor that emits a fluorescent color corresponding to yellow has a wavelength on the short wavelength side at which 50% of the spectral energy peak value is 500 nm to 550 nm.

According to a tenth aspect of the present invention, in the light source of the seventh aspect, the inert gas is xenon gas.

According to another aspect of the present invention, the fluorescent lamp includes a fluorescent lamp for irradiating an original with light emitted from a phosphor, and reading means for reading an image of the original illuminated by the fluorescent lamp. Converts two or more phosphors including a phosphor emitting a fluorescent color corresponding to blue and a phosphor emitting a fluorescent color corresponding to yellow into at least one colorimetric coefficient of red, green, and blue. Characterized by having a mixed phosphor mixed so as to increase the

According to the present invention, three phosphors that emit red, green, and blue fluorescent colors are provided, and red, green, and blue phosphors are provided.
When an original is irradiated with light emitted from a fluorescent lamp having a colorimetric coefficient improving phosphor that emits a fluorescent color that increases at least one of the blue colorimetric coefficients, the reading unit reflects the reflected light. To read the image of the original. Alternatively, two or more phosphors including a phosphor that emits a fluorescent color corresponding to blue and a phosphor that emits a fluorescent color corresponding to yellow are converted into at least one of red, green, and blue colorimetric coefficients. When the document is illuminated with light emitted from a fluorescent lamp having a mixed phosphor mixed so as to be raised, a reading unit reads an image of the document by reflected light of the emitted light. Thus, by increasing at least one of the red, green, and blue colorimetric coefficients,
Color reproducibility can be improved.

[0019]

Embodiments of the present invention will now be described with reference to the drawings.

A. First embodiment A-1. Configuration of Image Reading Device FIG. 1 is a block diagram showing a configuration of an image reading device according to a first embodiment of the present invention. In the figure, reference numeral 1 denotes a platen glass on which a document is placed, and 2 denotes a reference white plate for color correction. The reference white plate 2 is read prior to reading an image of a document, and an image signal obtained by reading the reference white plate 2 is used as correction data in shading correction described later.

Reference numeral 3 denotes a fluorescent lamp in which at least four types of phosphors 3a, 3b, 3c and 3d to be described later are mixed at a predetermined ratio and applied to the inner wall of a transparent glass tube 3e filled with an inert gas. . In this embodiment, xenon gas is used as the inert gas. The phosphor 3a is
The phosphor 3b emits a blue B fluorescent color, the phosphor 3b emits a green G fluorescent color, and the phosphor 3c emits a red R fluorescent color. Furthermore, the phosphor 3d
Emits a fluorescent color of yellow Y newly adopted in the present invention. The light emitted from the fluorescent lamp 3 is
The reflected light emitted to the original surface via the original platen glass 1 and reflected on the original surface is guided to the first reflecting mirror 4 via the original platen glass 1.

The first reflecting mirror 4 guides the reflected light to the second reflecting mirror 5, and the second reflecting mirror 5 further guides the reflected light to the third reflecting mirror 6.
The third reflecting mirror 6 guides the reflected light to the infrared absorption filter 7. The infrared absorption filter 7 has a spectral transmittance characteristic as shown in FIG. 3, removes long-wave infrared light from the reflected light, and guides the light to the lens 8. The lens 8 transmits the reflected light from which the infrared rays have been removed to a color linear image sensor (for example,
An image is formed on a color CCD 9. The color linear image sensor 9 has spectral sensitivity characteristics shown in FIG. 4 for each wavelength (blue B, green G, red R), and converts an image formed according to the spectral sensitivity characteristics into an electric signal. (Hereinafter, referred to as an image signal), and then supplied to a processing system described later. The fluorescent lamp 3 and the first reflecting mirror 4
Are arranged along the main scanning direction of the document, and move in the sub-scanning direction of the document to obtain a color image of the entire document.

A-2. FIG. 2 is a block diagram showing an image processing system (part) of color image data read by the above-described image reading apparatus. Note that the same reference numerals are given to portions corresponding to FIG. In the figure, an amplifier 10 amplifies an image signal supplied from a color linear image sensor 9 to a predetermined level and supplies the image signal to an A / D converter 11.
The A / D converter 11 converts the image signal into a digital signal (hereinafter, referred to as image data) and supplies the digital signal to the switch 12. The image data for the document is Di, and the image data for the reference white plate 2 is Ri.

Next, the switch 12 supplies the image signal for the reference white plate 2 to the correction data storage circuit 13 while the image signal of the original is supplied to the shading correction circuit 14.
The image signal is switched so as to supply the image signal. The correction data storage circuit 13 stores an image signal for the reference white plate 2 and supplies it to the shading correction circuit 14 at a predetermined timing. Also, the shading correction circuit 14
Performs shading correction on the image data Di for the original with the image data Ri for the reference white plate 2, and then sends the shading correction to a subsequent circuit (not shown).

A-3. Next, the above-described fluorescent lamp 3 will be described. As described above, the fluorescent lamp 3 used in the present embodiment has a structure shown in FIG.
In addition to the phosphors 3a, 3b, and 3c having emission colors of blue B, red R, and green G having the spectral energy characteristics shown in FIGS. 4A to 4C, the fluorescent light having the spectral energy characteristics shown in FIG. The body 3d is mixed at a predetermined ratio and applied to the inner wall surface. The added phosphor 3d
Has a peak value near a wavelength of 570 nm as shown in FIG. 5, and emits yellow Y light. In the present embodiment, the phosphor 3d for increasing the luminous energy of a wavelength near 570 nm, dysprosium with Katsurin vanadate _{-Y (P, V) O 4} : Dy- was used.

The phosphors 3a to 3d for the blue B, red R, green G, and yellow Y have the same output voltage ratio (blue B, green G, red R) in the color linear image sensor 9. That is, the output voltage ratio of each of the blue B, green G, and red R channels of the color linear image sensor 9 is set to a predetermined target value (for example, 0.1: 1).
8: 1: 0.8) and a ratio that satisfies the condition that a value (described later) serving as an index of color reproducibility becomes a target value is mixed through a general process. Is applied to the inner wall of the transparent glass tube 3e of the fluorescent lamp 3. Note that the method of manufacturing the fluorescent lamp 3 itself (coating of the phosphor) is performed by a conventional method, and a description thereof is omitted here.

A-4. Next, FIG. 6 shows four types of phosphors 3a, 3b, 3 corresponding to blue B, green G, red R, and yellow Y, respectively.
It is a figure showing the spectral energy characteristic of fluorescent lamp 3 when c and 3d are mixed. The illustrated spectral energy characteristics indicate that the output voltage ratio of each of the blue B, green G, and red R channels of the color linear image sensor 9 is 0.
8: 1: 0.8, and each of blue B, green G, red R, and yellow Y such that the colorimetric quality coefficient q, which is an index of color reproducibility, becomes 0.8 or more. This is a characteristic of the fluorescent lamp 3 when four types of corresponding phosphors 3a to 3d are mixed. As shown in the figure, in the fluorescent lamp 3 according to the present embodiment, the emission energy near the wavelength of 570 nm increases.

It should be noted that the spectral energy characteristic of the phosphor 3d with respect to yellow Y does not necessarily need to be the same as that shown in FIG. The energy may be increased, and the peak wavelength of the phosphor for yellow Y is shifted from the wavelength of 575 nm to the wavelength of 56 nm.
It may be in the range of 0-590 nm, and the bandwidth may be wider than the example shown.

A-5. Next, the method for evaluating the fluorescent lamp according to the present embodiment will be described. In the present embodiment, the fluorescent lamp was evaluated using the colorimetric quality factor q. The colorimetric quality coefficient q is an index indicating to what extent the integrated device spectral sensitivity characteristics of the image reading device match the human naked eye spectral sensitivity characteristics. For example, in the device spectral sensitivity characteristics and the visual spectral sensitivity characteristics,
If each of Blue B, Green G and Red R is equal,
The image reading apparatus can recognize that the image reading apparatus has the same characteristics as human eyes. In this case, the colorimetric quality coefficient q is “1”.

The apparatus spectral sensitivity characteristic is represented by the spectral characteristic Eλ of the light source of the image reading apparatus × the spectral characteristic of the optical system (including the infrared absorption filter) Oλ × the spectral sensitivity characteristic SBλ, SGλ, SRλ of each channel of the color linear image sensor. expressed. That is, the device spectral sensitivity characteristics for each of blue B, green G, and red R are as follows: Blue = Eλ × Oλ ×
SBλ, Green = Eλ × Oλ × SGλ, Red = Eλ
× Oλ × SRλ.

The spectral sensitivity characteristic of the naked eye is represented by the spectral characteristic ESTDλ of the standard light source × the spectral sensitivity characteristic (tristimulus value) SVBλ, S for each of the blue B, green G, and red R of the naked eye.
VGλ and SVRλ. That is, the visual spectral sensitivity characteristics for each of blue B, green G, and red R are B
lue = ESTDλ × SVBλ, Green = ESTDλ × SVG
λ, Red = ESTDλ × SVRλ.

Ideally, the above-described colorimetric quality coefficient q is "1" for each of blue B, green G, and red R, but cannot be realized by an actual image reading apparatus. , Green G, and red R, the colorimetric quality coefficients qB, qG, and qR are each desirably 0.8 or more.

Here, FIG. 7A shows the colorimetric quality coefficient qB, for each wavelength of the above-described conventional fluorescent lamp.
FIG. 7B is a table showing qG and qR. FIG. 7B shows the colorimetric quality coefficients qB and qB for each wavelength of the fluorescent lamp according to the present embodiment.
It is a table | surface figure which shows qG and qR. In the conventional fluorescent lamp, as shown in FIG. 7A, the colorimetric quality coefficients qB, qG, qR
Are 0.99, 0.79, and 0.69, respectively, and are less than 0.8 except for the colorimetric quality coefficient qB. On the contrary,
In the fluorescent lamp according to the present embodiment, as shown in FIG. 7B, the colorimetric quality coefficients qB, qG, and qR are each 0.9.
3, 0.88, 0.81 and all become 0.8 or more. Thus, in the fluorescent lamp 3 according to the present embodiment,
The color reproducibility could be improved by increasing the emission energy near the wavelength of 570 nm.

B. Second Embodiment The second embodiment is the same as the first embodiment except for the phosphor applied to the inner wall of the fluorescent lamp 3. Specifically, in the first embodiment, four types of phosphors 3a, 3b, 3c, 3
On the other hand, in the second embodiment, the phosphor 3a emitting a blue B fluorescent color and the phosphor 3x emitting a yellow Y fluorescent color are mixed at a predetermined ratio. Used. Note that the configuration of the image reading apparatus and the configuration of the image processing system according to the second embodiment are the same as the configuration of the first embodiment, and a description thereof will not be repeated.

B-1. FIG. 8 is a cross-sectional view of a fluorescent lamp 3 according to the second embodiment. The fluorescent lamp 3 is filled with an inert gas.
On the inner wall of the transparent glass tube 3e, a phosphor 3a emitting a blue B fluorescent color and a phosphor 3 emitting a yellow Y fluorescent color are provided.
A mixed phosphor in which x is mixed at a predetermined ratio is applied.
In this embodiment, xenon gas is used as the inert gas.

Here, the spectral energy characteristics of the phosphor 3a are the same as those shown in FIG. On the other hand, FIG. 9 shows the spectral energy characteristics of the phosphor 3x. From this figure, the spectral energy of the phosphor 3x gradually increases from 460 nm, reaches 50% of the peak value at 520 nm, and reaches 570 n
m, and when the wavelength becomes longer, 6
It can be seen that the peak value reaches 50% at 40 nm and becomes almost 0% near 800 nm.

The phosphors 3a and 3x for each of the blue B and yellow Y are provided by a color linear image sensor 9 respectively.
, The output voltage ratio of each of the blue B, green G, and red R channels becomes the same value (that is, 1: 1: 1), or each of the blue B, green G, and red R channels of the color linear image sensor 9 Satisfies the condition that the output voltage ratio becomes a predetermined target value (for example, 0.65: 1: 0.65) and a value (described later) serving as an index of color reproducibility becomes the target value. After being mixed in an appropriate ratio, the mixture is applied to the inner wall of the transparent glass tube 3e of the fluorescent lamp 3 through a general process. Note that the method of manufacturing the fluorescent lamp 3 itself (coating of the phosphor) is performed by a conventional method, and a description thereof is omitted here.

B-2. Example of Spectral Energy Characteristics of Fluorescent Lamp Next, FIG. 10 is a diagram illustrating spectral energy characteristics of the fluorescent lamp 3 when two types of phosphors 3a and 3x corresponding to blue B and yellow Y are mixed. The spectral energy characteristics shown in the drawing represent color reproduction while maintaining the output voltage ratio of each of the blue B, green G, and red R channels of the color linear image sensor 9 to be 0.65: 1: 0.65. This is a characteristic of the fluorescent lamp 3 when two types of phosphors 3a and 3x respectively corresponding to blue B and yellow Y are mixed such that a colorimetric quality factor q as an index of sex becomes 0.8 or more. . As shown in the figure, in the fluorescent lamp 3 according to the present embodiment, there is no region having no energy over the entire visible wavelength region, and there is no sharp peak over the entire visible wavelength region.

It should be noted that the spectral energy characteristics of the phosphor 3x for yellow Y do not necessarily have to be the same as those shown in FIG. It is only necessary that there is no area that is short, and that there is no sharp peak over the entire visible area. For example, the peak wavelength of the emission energy of the phosphor 3x with respect to yellow Y is 545n.
m to 585 nm, and the half width is 90 nm to 1
It may be in the range of 50 nm. Also, for the phosphor 3x for yellow Y, 50% of the spectral energy peak
May be in the range of 500 nm to 550 nm.

B-3. Next, a method for evaluating a fluorescent lamp according to the second embodiment will be described. In the second embodiment, the fluorescent lamp was evaluated using the colorimetric quality coefficient q as in the first embodiment. The colorimetric quality coefficient q is an index indicating to what extent the integrated device spectral sensitivity characteristics of the image reading device match the human naked eye spectral sensitivity characteristics. Specifically, the colorimetric quality factor q
Is the total device spectral sensitivity characteristic A when illuminated by the light source of the image reading device and read by the sensor via the optical system.
Is a spectral sensitivity characteristic B when illuminated with natural light (for example, a standard light source with a color temperature of 5000 K) and read by the naked human eye.
To the extent that

For example, if the spectral sensitivity characteristic A of the apparatus and the spectral sensitivity characteristic B of the naked eye are the same for each of blue B, green G, and red R, the image reading apparatus is illuminated with natural light and the total spectral reading when read by the naked human eye. It has the same characteristics as the sensitivity characteristics. In this case, the colorimetric quality coefficients qB, qG,
qR is “1”.

The spectral sensitivity characteristic of the apparatus is represented by the spectral characteristic Eλ of the light source of the image reading apparatus × the spectral characteristic of the optical system (including the infrared absorption filter) Oλ × the spectral sensitivity characteristic SBλ, SGλ, SRλ of each channel of the color linear image sensor. expressed. That is, the device spectral sensitivity characteristics for each of blue B, green G, and red R are as follows: Blue = Eλ × Oλ ×
SBλ, Green = Eλ × Oλ × SGλ, Red = Eλ
× Oλ × SRλ.

The spectral sensitivity characteristics of the naked eye are represented by the spectral characteristics ESTDλ of the standard light source × the spectral sensitivity characteristics (tristimulus values) SVBλ, SV for the blue B, green G, and red R of the naked eye.
VGλ and SVRλ. That is, the visual spectral sensitivity characteristics for each of blue B, green G, and red R are B
lue = ESTDλ × SVBλ, Green = ESTDλ × SVG
λ, Red = ESTDλ × SVRλ.

Ideally, the above-described colorimetric quality coefficient q is "1" for each of blue B, green G, and red R. However, since it cannot be realized by an actual image reading apparatus, generally, blue B , Green G, and red R, the colorimetric quality coefficients qB, qG, and qR are each desirably 0.8 or more.

Here, FIG. 11A shows a colorimetric quality coefficient q for each wavelength of the above-described conventional fluorescent lamp.
FIG. 11B is a table showing the colorimetric quality coefficients qB, qG, and qR for each wavelength of the fluorescent lamp according to the present embodiment. In a conventional fluorescent lamp, as shown in FIG.
G and qR are 0.99, 0.79 and 0.69, respectively, and are less than 0.8 except for the colorimetric quality coefficient qB. In contrast, in the fluorescent lamp according to the present embodiment, FIG.
As shown in (b), the colorimetric quality coefficients qB, qG, qR are:
Each becomes 0.93, 0.96, 0.88, and all become 0.85 or more, and the quality is greatly improved. Thus, in the fluorescent lamp 3 according to the present embodiment, blue B,
The color reproducibility is improved by mixing the yellow Y phosphors 3a and 3x to eliminate the region where there is no energy over the entire visible wavelength range, and not to have sharp peaks over the entire visible wavelength range. I was able to.

B-4. Next, a specific example of the fluorescent lamp according to the second embodiment will be described. Comparative Example First, for comparison, FIG. 16 shows the spectral energy characteristics of a conventional halogen fluorescent lamp, and FIG. 17 shows the colorimetric quality factor and the output voltage ratio of the color linear image sensor. As shown in FIG. 16, the conventional halogen fluorescent lamp has a characteristic that the relative spectral energy increases as the wavelength increases. The colorimetric quality factor q of this halogen fluorescent lamp is qB = 0.8 as shown in FIG.
7, qG = 0.99 and qR = 0.86.

Incidentally, the quality of an image read by an image reading apparatus is affected not only by various characteristics but also by the quality of an image signal input to an AD converter. The signal component S of the image signal is the output voltage vB, vG, v of each channel (B, G, R).
Determined by R. On the other hand, the noise component N of the image signal is
These are noise of each channel (B, G, R) of the color image sensor and noise caused by various analog circuits (for example, the amplifier 10 shown in FIG. 2) from the color image sensor to the AD converter. Here, the noise component N is a fixed amount determined for each device, and it is not easy to reduce this. Therefore, it is desirable that the minimum output voltage among the channels of the color image sensor is large. Therefore, as shown in this example, each voltage vB, v of the B, G, R image signals output from the color image sensor.
When the ratio of G and vR can be changed relatively freely, it is desirable that the voltages vB, vG and vR are balanced.

In the halogen fluorescent lamp of the comparative example,
When the ratio of the output voltages vB, vG, vR is 0.33: 1: 0.
It is 61. Here, when the saturation output voltage of the color image sensor is 2 V, and the maximum value of the actually used voltage is designed to be 1.5 V (vG in this example), the output voltage vB becomes 0.5 V. With such a difference in the output voltage ratio, the SN ratio does not deteriorate. In Examples 1 to 5 described below, the output voltage ratio is based on 0.33.

<Embodiment 1> Next, a phosphor 3x having a peak wavelength of 545 nm and a half width of 90 nm is used as the phosphor 3x that emits a yellow Y fluorescent color, and a phosphor 3a that emits a blue B fluorescent color is used as the phosphor 3x. The mixed fluorescent lamp will be described. The tendency of the spectral energy characteristics of the phosphor 3x is as follows.
This is almost the same as that shown in FIG. 9, and this peak wavelength is shifted to 545 nm.
The waveform is slightly sharpened in nm.

FIG. 18 is a diagram showing the spectral energy characteristics of the fluorescent lamp according to the first embodiment. From this figure, the wavelength of the first peak P1 is approximately 440 nm, and the second peak P2
Is approximately 545 nm. Here, the mixing ratio (weight ratio) between the phosphor 3a and the phosphor 3x is distributed so that each output voltage of the color image sensor is most balanced. FIG. 19 shows the colorimetric quality factor q of the fluorescent lamp, the output voltage v of the color image sensor, and the mixing ratio of the phosphors according to the first embodiment.

As shown in FIG. 19, this fluorescent lamp is coated on its inner surface with a phosphor obtained by mixing phosphor 3a and phosphor 3x at a ratio of 1: 2.35. The colorimetric quality coefficients are qB = 0.94, qG = 0.95, qR = 0.95.
It has become. When these values are compared with the comparative example, the colorimetric quality coefficient qG is reduced by 0.04, but the colorimetric quality coefficient qB is increased by 0.07 and the colorimetric quality coefficient qR is increased by 0.09. . Therefore, as a whole, Embodiment 1
Are improved.

Next, the output voltage ratio of the color image sensor is vB: vG: vR = 0.33: 1: 0.33, which is the same as the voltage ratio 1: 0.33 shown in the comparative example. Has become. In this case, the peak wavelength of the phosphor 3x is set to 545.
If it is shorter than nm, the voltage ratio of vB or vR to vG decreases, making it difficult to obtain a good SN ratio. The same problem occurs when the half width of the phosphor 3x is shorter than 90 nm. From these facts, the peak wavelength of the phosphor 3x is set to 545 nm, and the half value width is set to 90n.
Setting to m can be grasped as a limit value for obtaining a good SN ratio.

<Embodiment 2> Next, a phosphor 3x emitting a blue B fluorescent color is used as the phosphor 3x emitting a yellow Y fluorescent color, having a peak wavelength of 585 nm and a half width of 90 nm. The mixed fluorescent lamp will be described. The tendency of the spectral energy characteristics of the phosphor 3x is as follows.
This is almost the same as that shown in FIG. 9, the peak wavelength is shifted to 585 nm, and the half width is
The waveform is slightly sharpened in nm.

FIG. 20 is a diagram showing the spectral energy characteristics of the fluorescent lamp according to the second embodiment. From this figure, the wavelength of the first peak P1 is approximately 440 nm, and the second peak P2
Is approximately 585 nm. Here, the mixing ratio (weight ratio) between the phosphor 3a and the phosphor 3x is distributed so that each output voltage of the color image sensor is most balanced. In this example, the phosphor 3a and the phosphor 3
x is mixed 1: 1. FIG. 21 shows the colorimetric quality factor q of the fluorescent lamp, the output voltage v of the color image sensor, and the mixing ratio of the phosphors according to the second embodiment.

As shown in FIG. 21, the output voltage ratio of the color image sensor is vB: vG: vR = 1: 0.87:
1 and the voltage ratio vB: vG: v shown in the comparative example.
The balance is better than R = 0.33: 1: 0.61. When the colorimetric quality coefficient q is compared with that of the comparative example, the value of qB is changed from 0.87 to 0.94, and the value of qR is set to 0.9.
From 86 to 0.91, respectively. However, the colorimetric quality coefficient qG is reduced from 0.99 to 0.79, but since the colorimetric quality coefficient q may be about 0.8 or more,
It doesn't matter.

In this case, the peak wavelength of the phosphor 3x is 58
If it is longer than 5 nm, the colorimetric quality factor qG decreases,
The read image quality does not reach the target value. The same problem occurs when the half width of the phosphor 3x is shorter than 90 nm. From these facts, setting the peak wavelength of the phosphor 3x to 585 nm and its half-value width to 90 nm can be understood as a limit value for obtaining a good colorimetric quality coefficient q.

<Embodiment 3> Next, a fluorescent substance 3x that emits a fluorescent color of yellow Y has a spectral energy peak value of 50%.
The fluorescent lamp in which the wavelength on the short wavelength side of which is% is 500 nm and the phosphor 3a which emits the blue B fluorescent color is mixed with this will be described.

FIG. 22 is a diagram showing the spectral energy characteristics of the fluorescent lamp according to the second embodiment. From this figure, the wavelength of the first peak P1 is approximately 440 nm, and the second peak P2
Is approximately 545 nm. Also,
P50 indicates a position on the short wavelength side where the second peak P2 is 50%, and the wavelength is 500 nm. Here, the mixing ratio (weight ratio) of the phosphor 3a and the phosphor 3x is
The output voltages of the color image sensors are distributed so as to be most balanced. In this example, the phosphor 3a and the phosphor 3x are mixed at a ratio of 1: 2.2. FIG. 23 shows the third embodiment.
3 shows the colorimetric quality factor q of the fluorescent lamp, the output voltage v of the color image sensor, and the mixing ratio of the phosphors.

As shown in FIG. 23, the colorimetric quality coefficient is qB
= 0.94, qG = 0.98, and qR = 0.92. When these values are compared with the comparative example, the colorimetric quality coefficient qG is reduced by 0.01, but the colorimetric quality coefficient qG is reduced.
B is increased by 0.07, and the colorimetric quality coefficient qR is increased by 0.06. Accordingly, as a whole, the colorimetric quality factor q of the third embodiment is improved.

Next, the output voltage ratio of the color image sensor is vB: vG: vR = 0.36: 1: 0.36, which is the same as the voltage ratio 1: 0.33 shown in the comparative example. Has become. In this case, if the wavelength of the short wavelength side which is 50% of the spectral energy peak value of the phosphor 3x is shorter than 500 nm, the voltage ratio of vB or vR to vG decreases, and a good SN ratio can be obtained. Becomes difficult. From these facts, setting the wavelength on the short wavelength side, which is 50% of the spectral energy peak value of the phosphor 3x, to 500 nm can be grasped as a limit value for obtaining a good SN ratio.

<Embodiment 4> Next, as the fluorescent substance 3x which emits a fluorescent color of yellow Y, a spectral energy peak value of 50% is obtained.
%, A fluorescent lamp having a wavelength on the short wavelength side of 550 nm and a phosphor 3a emitting a blue B fluorescent color mixed therewith will be described.

FIG. 24 is a diagram showing the spectral energy characteristics of the fluorescent lamp according to the fourth embodiment. From this figure, the wavelength of the first peak P1 is approximately 440 nm, and the second peak P2
Is approximately 590 nm. Also,
P50 indicates the position on the short wavelength side where the second peak P2 is 50%, and the wavelength is 550 nm. Here, the mixing ratio (weight ratio) of the phosphor 3a and the phosphor 3x is
The output voltages of the color image sensors are distributed so as to be most balanced. In this example, the phosphor 3a and the phosphor 3x are mixed at a ratio of 1: 0.84. FIG. 25 illustrates the colorimetric quality factor q of the fluorescent lamp, the output voltage v of the color image sensor, and the mixing ratio of the phosphors according to the fourth embodiment.

As shown in FIG. 25, the output voltage ratio of the color image sensor is vB: vG: vR = 1: 0.8: 1.
And the voltage ratio vB: vG: vR shown in the comparative example.
= 0.33: 1: 0.61. Further, the colorimetric quality coefficient q exceeds all the target values of 0.8.

In this case, if the shorter wavelength, which is 50% of the spectral energy peak value of the phosphor 3x, is longer than 550 nm, the colorimetric quality factor qG decreases,
The read image quality does not reach the target value. From these facts, regarding the phosphor 3x, the spectral energy peak value of 5
Setting the wavelength on the short wavelength side of 0% to 550 nm can be understood as a limit value for obtaining a good colorimetric quality coefficient q.

<Embodiment 5> Next, as the phosphor 3x that emits a yellow Y fluorescent color, a phosphor having the spectral energy characteristic shown in FIG. 9 is used, and a phosphor 3a that emits a blue B fluorescent color is mixed with the phosphor 3x. Will be described. In the fifth embodiment, the mixing ratio between the phosphor 3a and the phosphor 3x is set to a)
1: 0.5, b) 1: 0.75, c) 1: 1.05,
d) 1: 1.5 and e) 1: 2. FIG. 26 shows the spectral energy characteristics of the fluorescent lamp at the mixing ratios a) to e). Assuming that the energy level of the second peak P2 is 100%, as shown in FIG.
Increases, the first peak P1 decreases.

FIG. 27 shows the colorimetric quality factor q of the fluorescent lamp, the output voltage v of the color image sensor, and the mixing ratio of the phosphor according to the fifth embodiment. As shown in this figure, the colorimetric quality coefficient q does not change significantly even when the mixture ratio is changed. On the other hand, the output voltage ratio of the color image sensor changes as the mixing ratio of the phosphor 3x increases, and in particular, the ratio of vB to vG decreases. However, even when the mixing ratio e) is 1: 2, the ratio of vB to vG is 0.38, which exceeds the target value of 0.33.

From this, it can be said that even if the mixing ratio of the phosphor 3a and the phosphor 3x is changed, the effect on the colorimetric quality factor q is small and the effect on the output voltage ratio of the color image sensor is large.

C. Modifications The present invention is not limited to the embodiments described above,
For example, various modifications described below are possible. In each of the embodiments described above, the fluorescent lamp is applied to the image reading device. However, the present invention is not limited to this, and the fluorescent lamp may be used for a general indoor lighting fixture. Therefore, the light source may be a xenon fluorescent lamp or a mercury-containing fluorescent lamp (for example, a three-wavelength type).

In the first embodiment described above, four types of phosphors are used. However, the present invention is not limited to this.
If the spectral energy near 70 nm is to be increased, five or more kinds of phosphors may be used. In the above-described second embodiment, two types of phosphors are mixed and used. However, if there is no region having no energy over the entire visible wavelength region, and if there is no sharp peak over the entire visible wavelength region, the present invention is not limited to this. For example, three or more kinds of phosphors may be used.

In the second embodiment described above, in order to shift the peak wavelength in the wavelength region relating to blue B,
A third phosphor may be mixed. In this case, as the third phosphor, for example, a Sian C phosphor having a peak at 500 nm is suitable.

In the second embodiment described above, the output voltage ratio of each of the blue B, green G, and red R channels of the color linear image sensor 9 is 0.65: 1: 0.
However, in order to make the output voltage ratio of each channel 0.8: 1: 0.8, a small amount of the red R phosphor shown in FIG. 14B may be mixed. In this case, since a slightly sharp peak is generated in the red R wavelength range, the colorimetric quality coefficient qR is slightly deteriorated. However, the balance of the output voltage ratio between the blue B, green G, and red R channels of the color linear image sensor 9 is obtained. Is improved. As a result,
It is possible to improve the quality of a comprehensively read image.

[0072]

As described above, according to the present invention, three phosphors emitting red, green, and blue fluorescent colors are provided, and at least one of the red, green, and blue colorimetric coefficients is provided. The document is illuminated with light emitted from a fluorescent lamp having a colorimetric coefficient improving phosphor that emits a fluorescent color that raises the colorimetric coefficient, and the reading means reads the image of the original with reflected light of the irradiated light. By increasing at least one of the red, green, and blue colorimetric coefficients, the color reproducibility can be improved.

Further, two or more phosphors including a phosphor emitting a fluorescent color corresponding to blue and a phosphor emitting a fluorescent color corresponding to yellow are combined with at least one of red, green and blue colorimetric coefficients. Since the fluorescent lamp including the mixed phosphor mixed to increase the colorimetric coefficient is used, the quality of the read image can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating an image processing system of the image reading apparatus according to the embodiment.

FIG. 3 is a diagram showing a spectral transmittance characteristic of an infrared absorption filter of the image reading apparatus according to the embodiment.

FIG. 4 is a diagram showing a spectral sensitivity characteristic of the color linear image sensor of the image reading apparatus according to the embodiment.

FIG. 5 is a diagram showing a spectral energy characteristic of dysprosium-activated phosphorus vanadate added as a phosphor of the fluorescent lamp according to the same embodiment.

FIG. 6 is a diagram showing spectral energy characteristics of the fluorescent lamp according to the same embodiment.

FIG. 7 is a table showing colorimetric quality coefficients qB, qG, qR for each wavelength of a fluorescent lamp according to the prior art, and colorimetric quality coefficients qB, qG, qR for each wavelength of a fluorescent lamp according to the first embodiment. FIG.

FIG. 8 is a sectional view of a fluorescent lamp according to a second embodiment.

FIG. 9 is a diagram showing spectral energy characteristics of a phosphor 3x according to the same embodiment.

FIG. 10 is a diagram showing spectral energy characteristics of the fluorescent lamp according to the embodiment.

FIG. 11 is a table showing colorimetric quality coefficients qB, qG, and qR with respect to each wavelength of a fluorescent lamp according to the prior art;
FIG. 4 is a table showing colorimetric quality coefficients qB, qG, and qR for each wavelength of the fluorescent lamp according to the embodiment.

FIG. 12 is a diagram showing spectral energy characteristics of a conventional fluorescent lamp (containing mercury).

FIG. 13 is a diagram showing spectral energy characteristics of a conventional xenon fluorescent lamp.

FIG. 14 is a diagram showing spectral energy characteristics of a phosphor for each color B, R, and G used in a conventional xenon fluorescent lamp.

FIG. 15 shows a conventional xenon fluorescent lamp,
FIG. 4 is a diagram showing spectral energy characteristics of a xenon fluorescent lamp when a phosphor having a wide bandwidth is used.

FIG. 16 is a diagram showing spectral energy characteristics of a conventional halogen fluorescent lamp.

FIG. 17 is a diagram showing a colorimetric quality coefficient of a conventional halogen fluorescent lamp and an output voltage ratio of a color linear image sensor.

FIG. 18 is a diagram illustrating a spectral energy characteristic of the halogen fluorescent lamp according to the first embodiment.

FIG. 19 is a diagram showing a colorimetric quality factor of a halogen fluorescent lamp, an output voltage of a color image sensor, and a mixing ratio of phosphors according to the embodiment.

FIG. 20 is a diagram illustrating spectral energy characteristics of the halogen fluorescent lamp according to the second embodiment.

FIG. 21 is a diagram showing a colorimetric quality factor of a halogen fluorescent lamp, an output voltage of a color image sensor, and a mixing ratio of phosphors according to the embodiment.

FIG. 22 is a diagram showing a spectral energy characteristic of the halogen fluorescent lamp according to the third embodiment.

FIG. 23 is a diagram showing a colorimetric quality coefficient of a halogen fluorescent lamp, an output voltage of a color image sensor, and a mixing ratio of phosphors according to the example.

FIG. 24 is a diagram showing a spectral energy characteristic of the halogen fluorescent lamp according to the fourth embodiment.

FIG. 25 is a diagram showing a colorimetric quality factor of a halogen fluorescent lamp, an output voltage of a color image sensor, and a mixing ratio of phosphors according to the example.

FIG. 26 shows a phosphor 3a and a phosphor 3x in the fifth embodiment.
FIG. 7 is a diagram showing spectral energy characteristics when the mixing ratio of the light-emitting elements is changed.

FIG. 27 is a diagram showing a colorimetric quality coefficient of a halogen fluorescent lamp, an output voltage of a color image sensor, and a mixing ratio of phosphors according to the example.

[Description of Signs] 3 Fluorescent lamp 3e Transparent glass tube (transparent tube) 3a, 3b, 3c Phosphor (three phosphors) 3d Phosphor (phosphor with improved colorimetric coefficient) 3x phosphor (fluorescent color corresponding to yellow) 4 First reflecting mirror 5 Second reflecting mirror 6 Third reflecting mirror 7 Infrared elimination filter 8 Lens 9 Color linear image sensor (reading means)

Claims (11)

[Claims] 1. A transparent member filled with an inert gas, three phosphors provided inside the transparent member and emitting fluorescent colors corresponding to red, green, and blue, respectively, and inside the transparent member. And a colorimetric coefficient improving phosphor that emits a fluorescent color that increases at least one of the red, green, and blue colorimetric coefficients. 2. The light source according to claim 1, wherein the colorimetric coefficient improving phosphor has a yellow fluorescent color. 3. The light source according to claim 1, wherein said inert gas is xenon gas. 4. The phosphor for improving a colorimetric coefficient may be a dysprosium-activated phosphor vanadate phosphor, Y (P, V) O ₄ :
The light source according to claim 1, wherein the light source is "Dy". 5. The light source according to claim 1, wherein the colorimetric coefficient-enhancing phosphor has a peak wavelength of an emission wavelength thereof in a range of at least 560 to 590 nm. 6. A fluorescent lamp for irradiating an original with light emitted from a phosphor, and reading means for reading an image of the original illuminated by the fluorescent lamp, wherein the fluorescent lamp has a red, green, and blue color. It is characterized in that it comprises three phosphors that emit fluorescent colors and a colorimetric coefficient improving phosphor that emits a fluorescent color that increases at least one of the red, green, and blue colorimetric coefficients. Image reading device. 7. A transparent member filled with an inert gas, a phosphor provided inside the transparent member and emitting a fluorescent color corresponding to blue, and a phosphor emitting a fluorescent color corresponding to yellow. A light source, comprising: a mixed phosphor obtained by mixing the above phosphors so as to increase at least one of the red, green, and blue colorimetric coefficients. 8. The phosphor that emits a fluorescent color corresponding to yellow has a peak emission wavelength of 545 nm to 585 nm.
8. The light source according to claim 7, wherein the half-width is in a range of 90 nm to 150 nm. 9. The phosphor according to claim 7, wherein the short-wavelength side of the phosphor that emits a fluorescent color corresponding to yellow has a spectral energy peak value of 50% at a wavelength of 500 nm to 550 nm. light source. 10. The light source according to claim 7, wherein said inert gas is xenon gas. 11. A fluorescent lamp for illuminating an original with light emitted from a phosphor, and reading means for reading an image of the original illuminated by the fluorescent lamp, wherein the fluorescent lamp has a fluorescent color corresponding to blue. Mixed fluorescent light in which at least one of red, green, and blue colorimetric coefficients is increased by mixing two or more fluorescent substances including a fluorescent substance that emits fluorescent light and a fluorescent substance that emits a fluorescent color corresponding to yellow. An image reading device comprising a body.