JPH1032680A - Image reading device and fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent S/N deterioration by color and to prolong the life of a lamp by previously applying early deteriorating one of fluorescent materials by a little more quantity in consideration of the difference in the deterioration characteristic of the light emitting intensity of the fluorescent materials of three colors in a three-wavelength type fluorescent lamp, so as to nearly equalize the life due to the deterioration of the fluorescent materials of the three colors to nearly equalize the RGB output level of CCD. SOLUTION: Plural kinds of fluorescent materials are applied to the inside of the fluorescent lamp of a light source for a copier. At the time of using three-wavelength type fluorescent materials as the fluorescent materials, the deteriorating characteristic of the radiating intensity of the fluorescent materials is different depending on its kind. In the attenuating characteristic of an RGB output signal to an accumulated lighting time in a rated lamp current, if the minimum value of an output signal is 50%, e.g. with respect to an initial value at the time of securing the S/N of the output signal of CCD, the ratio of the applying quantity of the fluorescent material of a large deterioration characteristic is previously made high so as to nearly equalize time for R1101, G1102 and B1103 to amount to the 50%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading an image on a document and a fluorescent lamp used for the same.

[0002]

2. Description of the Related Art In a conventional image reading apparatus in which a document image is illuminated by a light source and the reflected light is read by a CCD image sensor, a halogen lamp is used as a light source. However, the halogen lamp has a very low ratio of the amount of radiation intensity of visible light to the input power, that is, the luminous efficiency, and is generally said to be 7 to 8%.
In other words, most of the energy is consumed as heat energy, and the heat generated has had a considerable effect on the quality characteristics of peripheral electric components and mechanical components. In addition, since halogen lamps have a peak of the radiation intensity in the infrared region,
When a three-color signal of red, green and blue is to be obtained as a color image reading device, a filter for blocking unnecessary infrared light is required.

[0003] Furthermore, in consideration of environmental problems, which have recently become a problem, laws and regulations for power saving have been enforced, and the use of light sources having higher luminous efficiency has been desired. As such a light source, for example, there is a fluorescent lamp whose luminous efficiency is generally said to be 20%. Some fluorescent lamps are coated with a plurality of types of phosphors to realize a white light source color.

[0004]

However, the emission intensity spectrum emitted from the phosphor has a unique characteristic having a peak emission intensity in a certain wavelength range depending on the type of the phosphor, and is uniform over the entire visible light range. It does not have a good spectrum. (Details will be described later.) Therefore, in general, the application amounts of a plurality of types of phosphors are determined so that a person feels good in color rendering.

Therefore, when an original image irradiated by such a fluorescent lamp is read by a CCD image sensor, the respective color components of the output three primary color signals are not aligned.
There has been a problem that image quality defects such as deterioration of S / N of a signal of a small color component and deterioration of color linearity occur. In addition, the phosphor has the characteristic that the radiation intensity is gradually attenuated as the cumulative lighting time increases, and the attenuation characteristics differ depending on the type of the phosphor. There is a problem that the life of the camera is determined.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in the image reading apparatus according to the first aspect, a fluorescent lamp coated with a plurality of color phosphors is provided.
A sensor for converting light from a subject illuminated by the fluorescent lamp into image signals of a plurality of colors, wherein an integral value of a product of a radiation characteristic of the phosphor and a sensitivity characteristic of the sensor becomes substantially equal to a predetermined value. As described above, the application amount of the phosphor is set for each color.

According to a fifth aspect of the present invention, there is provided a fluorescent lamp which is constituted by applying a phosphor of a plurality of colors and which can be used in an image reading apparatus having a sensor for converting light from a subject into an image signal. The application amount of the phosphor is set for each color such that the integral value of the product of the radiation characteristic of the body and the spectral sensitivity characteristic of the sensor is substantially equal to a predetermined value.

According to a ninth aspect of the present invention, there is provided an image reading apparatus comprising: a fluorescent lamp coated with a plurality of types of phosphors; and a sensor for converting light from a subject illuminated by the fluorescent lamp into an image signal and outputting the image signal. The application amount of each phosphor is set according to the deterioration characteristics of the phosphor.

According to a thirteenth aspect of the present invention, in the fluorescent lamp which is constituted by applying a plurality of kinds of phosphors and which can be used in an image reading apparatus, each of the phosphors is applied in accordance with the deterioration characteristics of the phosphor. The amount is set.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a side view of a fluorescent lamp of a light source for a copying machine according to a first embodiment of the present invention, and FIG. 2 is a sectional view thereof. In FIG. 1, a mercury gas and a rare gas 201 are sealed in a glass tube 101 by caps 202 at both ends of the glass tube 101. Further, at both ends of the glass tube 101, electrodes 203 of a tungsten coil coated with an electron emitting material are supported by a stem 204, and an electric current is supplied through a conductive portion 205 provided on the base 202.

A reflection film 104 for reflecting and diffusing generated light is applied to the inside of the glass tube 101, and a plurality of types of phosphors 103 are applied to the inside of the reflection film 104. Since the reflective film or the phosphor 103 is not applied to the aperture (optical opening) on the side of the glass tube,
Light passes through the aperture section 105.

When a current flows through the electrode 203, the electrode 203
The electrons emitted from the semiconductor collide with mercury atoms, and the mercury atoms are excited to emit ultraviolet rays. The emitted ultraviolet light excites a substance constituting the phosphor inside the discharge tube, and is converted into visible light having a wavelength specific to the phosphor. The light generated inside the glass tube in this way is repeatedly reflected internally by the reflection film 104, and strong light is emitted from the aperture 105 in the direction of the arrow in FIG.

FIG. 3 shows a radiation intensity spectrum of light generated when a three-wavelength phosphor is used as the phosphor. The phosphor having a red wavelength region 301 as a main emission spectrum is shown in FIG. (Hereinafter, referred to as a red phosphor), a phosphor having a green wavelength region 302 as a main emission spectrum (hereinafter, referred to as a green phosphor), and a phosphor having a blue wavelength region 303 as a main emission spectrum. (Hereinafter, referred to as a blue phosphor).

FIG. 4 shows a configuration diagram of an optical system of an image reading apparatus using a fluorescent lamp according to the present embodiment. Light emitted from the aperture 105 of the fluorescent lamp 401 is:
First focusing reflector 402, second focusing reflector 403
Then, the light is reflected to the vicinity of the reading line 406 of the original 405 on the platen glass 404. The reflected light of the original is transmitted to a first mirror 407, a second mirror 408, and a third mirror 409.
And a CCD image sensor 411 by the lens 410
It is led to.

Here, a light shielding plate 412 is provided so that light emitted from the back of the fluorescent lamp 401 does not directly irradiate the original 405. In addition, the fluorescent lamp 401, the first condenser reflector 402, the second condenser reflector 403, and the light shielding plate 4
Reference numeral 12 moves as one scanner unit 413 along the document surface. In accordance with the movement of the scanner unit 413, the second mirror 408 and the third mirror 409 also move so that the optical path length from the reading line 406 to the CCD 411 is kept constant.

FIG. 5 is a peripheral view of the fluorescent lamp 401. In FIG. 5, a fluorescent lamp 401 is connected to a socket 50.
1 and a current is supplied from a pin on the socket 501. The fluorescent lamp 401 is provided with the aperture 105 as described with reference to FIG. 2, and outputs strong light in the direction of the arrow in FIG. 5 and relatively weak light in the opposite direction.

A light amount sensor 502 is provided on the opposite side of the aperture 105 for measuring the light amount of the fluorescent lamp. A photodiode or the like is used as the light amount sensor 502, and outputs a current proportional to the light amount of the fluorescent lamp. The light amount measurement value obtained by the light amount sensor 502 is feedback-controlled so that the light amount emitted from the fluorescent lamp becomes constant.

FIG. 6 is a block diagram of the light quantity control of the fluorescent lamp 401, and FIG. 7 is a timing chart for explaining its operation. 6, a light amount signal output from a light amount sensor 502 is converted into a voltage value by an amplifier 601 and amplified. A comparator 602 compares a voltage corresponding to the observed light amount with a desired light amount value and outputs the result to a light amount controller. I do. Then, the light amount controller 603 performs synchronization (SY
NC), and outputs a pulse width modulation (PWM) signal synchronized with the phase of the signal. The light amount controller 603 controls the duty ratio of the PWM signal to decrease when the observed light amount is larger than the desired light amount as shown in FIG.
When the observed light quantity is smaller than the desired light quantity, control is performed so that the duty ratio increases.

P output from the light intensity controller 603
The WM signal is input to the inverter 604, and the inverter 604 operates at a higher frequency (about 10 to 100 times) than the PWM signal when the input PWM signal is at “H” level.
Is supplied to the fluorescent lamp to turn on the fluorescent lamp, and when the lamp is at the "L" level, the lamp current is cut off and the fluorescent lamp is turned off. This on / off control is repeated at the cycle of the PWM signal. As described above, the light amount of the fluorescent lamp 401 can be kept constant by controlling the duty of the ON / OFF cycle.

Next, an example of the configuration of the CCD 411 is shown in FIG.
The photoelectric conversion units 801, 805, and 809 include photodiodes 801-a, b, c, d, 805-a, b, c, d,
809-a, b, c, and d. Red, green, and blue color filters are formed on the upper layers, respectively, to separate incident light into red, green, and blue. Photoelectric conversion unit 80
At 1,805 and 809, electrons are excited according to the amount of incident light and the respective spectral sensitivity characteristics, and are accumulated as signal charges. FIG. 9 shows the spectral sensitivity characteristics of the photoelectric conversion units 801, 805, and 809 in which the color filters are formed as described above. Reference numeral 901 denotes a photoelectric conversion unit 801 in which a red (R) filter is formed; Reference numeral 902 denotes a photoelectric conversion unit 805 having a green (G) filter formed thereon, and 903 denotes a blue (B) filter.
3 shows the characteristics of the photoelectric conversion unit 809 in which the filters of FIG. The accumulated signal charges are transferred to the transfer gate 80.
2, 806, 810, and periodically transfer units 803, 8
07, 811 and further transferred sequentially in the arrangement direction of the photoelectric conversion pixel columns, that is, in the main scanning direction, and the image signals of one scanning line are amplified by the output amplifiers 804, 808, 812, and then the three primary color signals R, G and B signals are output.

By the way, the light quantity of the above-mentioned fluorescent lamp is
In order to depend on the amount of radiant intensity of visible light that is photoexcited from the phosphor by ultraviolet rays emitted from mercury atoms in the tube,
Under the same conditions, the amount of light is substantially proportional to the amount of phosphor applied. Here, in the present embodiment, a product obtained by multiplying the emission intensity spectrum 301 of the red phosphor shown in FIG. 3 by the spectral sensitivity characteristic 901 of the photoelectric conversion unit 801 having the red filter shown in FIG. The integration value of the spectral sensitivity characteristic of the R signal, the emission intensity spectrum 302 of the green phosphor shown in FIG. 3, and the integration value of the spectral sensitivity characteristic 902 of the photoelectric conversion unit 805 provided with the green filter shown in FIG. 3
Multiplied by the emission intensity spectrum 303 of the blue phosphor shown in FIG. 9 and the spectral sensitivity characteristic 903 of the photoelectric conversion unit 809 having the blue filter shown in FIG. 9, that is, the integral value of the spectral sensitivity characteristic of the B signal. The application amounts of the three types of phosphors are set so that the three integrated values are substantially equal. This means that the RGB signals when a blank sheet is read are almost equal.

In this embodiment, since the coating amount of the phosphor is determined as described above, the S / N differs depending on the color,
It is possible to prevent color linearity from deteriorating due to different amounts of light at which the amount of accumulated charge is saturated in each photoelectric conversion unit. Further, as shown in FIG. 3, the phosphor of each color has almost no emission intensity in the infrared wavelength region other than around 1000 nm, and the spectral sensitivity characteristics of the CCD become considerably low near 1000 nm. Therefore, it is hardly affected by infrared light. Therefore, there is no need for an infrared cutoff filter or the like that has been required when a halogen lamp is used as a light source.

As described above, in the present embodiment,
The application amounts of the three types of phosphors are set so that the RGB signals are substantially equal. However, the application amounts may be set, for example, in accordance with the standard relative luminous efficiency characteristics. That is, the integrated value of the spectral sensitivity characteristics of each of the RGB signals is set to 0.30: 0.59: 0.1.
By setting to 1, a signal matching the sensitivity of human eyes can be obtained, and as a result, S / S
N can be set highest. A similar effect can be obtained even if the ratio is not so strict, for example, by setting the ratio to 0.25: 0.5: 0.25.

(Second Embodiment) It is generally known that the degradation characteristics of the radiation intensity of a phosphor differ depending on the type. FIG. 10 shows an example of the deterioration characteristic, showing the attenuation characteristic of the RGB output signal with respect to the cumulative lighting time at the rated lamp current, where 1001 is the G signal characteristic, and 1002 is the R signal characteristic.
A signal characteristic 1003 indicates the characteristic of the B signal. Here, an example is shown in which the application amount of the phosphor is set so that the RGB signals at the initial stage are equal, as in the first embodiment, and each signal output when the cumulative lighting time is zero in FIG. At almost the same level. Assuming that the minimum signal output value is, for example, 50% of the initial value in securing the S / N of the CCD output signal, the B signal first reaches the 50% level in 400 hours. Next, it can be seen that the G signal reaches 600 hours and the R signal reaches 800 hours. In this case, when the B signal reaches 50%, that is, 400 hours, the lamp life expires, and the lamp needs to be replaced.

Therefore, in this embodiment, as shown in FIG. 11, the ratio of the amount of the phosphor applied is increased in advance for those having a large deterioration characteristic so that the time to reach 50% becomes almost the same for RGB. . That is, when the coating amount of each phosphor shown in FIG. 10 is 100%, the green phosphor is approximately 96%,
By making the red phosphor about 85% and the blue phosphor about 119%, all the RGB signals can be reached in about 554 hours. By setting the application amount of the phosphor of each color in this manner, the lamp life can be greatly extended.

[0026]

As described above, in the image reading apparatus according to the first aspect, the fluorescent lamp coated with the phosphors of a plurality of colors and the light from the subject illuminated by the fluorescent lamps are used as image signals of the plurality of colors. And a coating amount of the phosphor is set for each color such that an integrated value of a product of a radiation characteristic of the phosphor and a sensitivity characteristic of the sensor becomes substantially equal to a predetermined value. According to a fifth aspect of the present invention, there is provided a fluorescent lamp which can be used in an image reading apparatus having a sensor for converting light from a subject into an image signal by applying a plurality of colors of phosphors. The application amount of the phosphor was set for each color such that the integral value of the product of the radiation characteristic of the sensor and the spectral sensitivity characteristic of the sensor became substantially equal to a predetermined value.

With this configuration, a high-quality image signal can be obtained when the fluorescent lamp is used for image reading without changing the S / N depending on the color or deteriorating the linearity of the color. It became so.
In addition, by using a fluorescent lamp having a higher luminous efficiency than a halogen lamp, power consumption was significantly reduced. Further, when a halogen lamp is used, an infrared cutoff filter, which has been required, is not required, so that the configuration of the apparatus can be simplified and the cost can be reduced.

The image reading apparatus according to the ninth aspect has a fluorescent lamp coated with a plurality of types of phosphors, and a sensor for converting light from a subject illuminated by the fluorescent lamp into an image signal and outputting the image signal. Then, the application amount of each phosphor was set according to the deterioration characteristics of the phosphor. The fluorescent lamp according to claim 13, wherein a plurality of types of phosphors are applied, and in a fluorescent lamp usable for an image reading apparatus, the amount of each phosphor applied according to the deterioration characteristics of the phosphor. It was set.

With such a configuration, the life of the fluorescent lamp is greatly extended, and the S / N differs depending on the color even if the accumulated use time of the fluorescent lamp is prolonged and the applied phosphor deteriorates. High-quality image signals can be obtained without destroying the color linearity.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fluorescent lamp according to an embodiment.

FIG. 2 is a side view of the fluorescent lamp in the embodiment.

FIG. 3 is a radiation intensity spectrum diagram of the fluorescent lamp in the embodiment.

FIG. 4 is a configuration diagram of an optical system in the image reading apparatus according to the embodiment.

FIG. 5 is a diagram showing a peripheral portion of the fluorescent lamp according to the embodiment.

FIG. 6 is a block diagram of a dimming circuit in the image reading device according to the embodiment.

FIG. 7 is a timing chart illustrating the dimming circuit of FIG. 6;

FIG. 8 is a configuration diagram of a CCD linear image sensor according to the embodiment.

FIG. 9 is a spectral sensitivity characteristic diagram of the CCD linear image sensor of FIG.

FIG. 10 is a graph showing a deterioration characteristic of a radiation intensity of a phosphor.

FIG. 11 is a graph showing a deterioration characteristic of the radiation intensity of the phosphor in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Glass tube 103 Fluorescent substance 202 Base 203 Electrode 205 Conductive part

Claims (16)

[Claims] A fluorescent lamp coated with phosphors of a plurality of colors; and a sensor for converting light from a subject illuminated by the fluorescent lamps into image signals of a plurality of colors. The image reading apparatus according to claim 1, wherein an application amount of the phosphor is set for each color such that an integral value of a product of the sensitivity characteristics of the sensor is substantially equal to a predetermined value. 2. The method according to claim 1, wherein an integral value of a product of a radiation characteristic of the phosphor and a sensitivity characteristic of a sensor that outputs an image signal of the same color as the emission color of the phosphor has a predetermined value. An image reading apparatus wherein the amount of each color phosphor applied is set. 3. The image reading device according to claim 1, wherein the fluorescent lamp is formed by applying a luminous body that emits red, green, and blue light. 4. The image reading apparatus according to claim 1, wherein the sensor converts light from the subject into red, blue, and green image signals. 5. A fluorescent lamp which can be used in an image reading apparatus having a sensor for converting light from an object into an image signal by applying a phosphor of a plurality of colors and a radiation characteristic of the phosphor and a spectrum of the sensor. A fluorescent lamp characterized in that the application amount of the phosphor is set for each color so that the integral value of the product of the sensitivity characteristics becomes substantially equal to a predetermined value. 6. The system according to claim 5, wherein an integral value of a product of a radiation characteristic of the phosphor and a sensitivity characteristic of a sensor that outputs an image signal of the same color as the emission color of the phosphor has a predetermined value. A fluorescent lamp characterized in that the amount of the phosphor applied is set. 7. The fluorescent lamp according to claim 5, wherein a luminous body having at least red, green, and blue luminescent colors is applied. 8. The fluorescent lamp according to claim 5, wherein the sensor converts light from the subject into red, blue, and green image signals. 9. A fluorescent lamp having a plurality of types of phosphors applied thereto, and a sensor for converting light from a subject illuminated by the fluorescent lamp into an image signal and outputting the image signal, wherein a deterioration characteristic of the phosphor is provided. An image reading apparatus, wherein an application amount of each phosphor is set according to the setting. 10. The image reading apparatus according to claim 9, wherein the amount of the rapidly deteriorating phosphor is larger than the amount of the slowly deteriorating phosphor. 11. The method according to claim 9, wherein the application amount of each phosphor is set so that the amount of deterioration of each phosphor becomes substantially the same when the cumulative lighting time of the fluorescent lamp elapses a predetermined time. Characteristic image reading device. 12. An image reading apparatus according to claim 9, wherein said fluorescent lamp is coated with a luminous body that emits at least red, green, and blue light. 13. A fluorescent lamp which is constituted by applying a plurality of types of phosphors and which can be used in an image reading apparatus, wherein the amount of each phosphor applied is set in accordance with the deterioration characteristics of the phosphors. Fluorescent lamp. 14. The fluorescent lamp according to claim 13, wherein the amount of the rapidly deteriorating phosphor is larger than the amount of the slowly deteriorating phosphor. 15. The fluorescent light according to claim 13, wherein the amount of application of each phosphor is set so that the amount of deterioration of each phosphor becomes substantially the same when the accumulated lighting time has passed a predetermined time. lamp. 16. A fluorescent lamp according to any one of claims 13 to 15, wherein a luminous body having at least luminescent colors of red, green and blue is applied.