JPH02100202A - Point light source device - Google Patents

Abstract

PURPOSE:To enable obtaining a point light source device emitting a beam of high light intensity by containing a phosphor emitting fluorescent light in the core part of an optical fiber wound about a light source. CONSTITUTION:The title in the device comprises a rod-shaped light source 31 such as a fluorescent lamp and many turns of an optical fiber 32 wound spirally about the aforesaid light source 31. The optical fiber 32 has a core 32A covered with a clad 32B having a refraction factor lower than the core 32A. Also, a phosphor mainly emitting the fluorescent light of 630nm wave length upon receipt of light 33 mainly having 480nm wave length and emitted from the light source 31 is diffused and contained within the core 32A. Much of fluorescent light emitted from the phosphor repeats total reflection on the interface of the cope part 32A and the clad 32B and propagates to the side of the edge of the optical fiber 32. As a result, fluorescent light is emitted from the edge of the optical fiber 32 in high intensity and like a spot. According to the aforesaid construction, it is possible to obtain a beam of extremely high light intensity at enough low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a point light source device that generates a high-intensity light beam with a small spot diameter.

(Prior art) When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), a part of the energy of this radiation is accumulated in the phosphor. It is known that when this phosphor is then irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the stored energy. (stimulable phosphor).

Using this stimulable phosphor, radiation image information of a subject such as a human body is transferred to a sheet having a layer of stimulable phosphor (hereinafter referred to as a ``stimulable phosphor sheet'' or simply ``sheet''). This stimulable phosphor sheet is irradiated with excitation light such as a laser beam to generate stimulated luminescent light, and the resulting stimulated luminescent light is read photoelectrically to obtain an image signal. A radiation image information recording and reproducing system has been proposed that processes the radiation image to obtain a radiation image of a subject that is suitable for diagnosis (for example, Japanese Patent Laid-Open Nos. 55-12429 and 55-11).
No. 6340, No. 55-163472, No. 56-113
No. 95, No. 56-104645, etc.).

Conventionally, specifically, semiconductor lasers and gas lasers such as He-Ne have been often used as excitation light sources for generating excitation light in the above-mentioned systems.

(Problems to be Solved by the Invention) Semiconductor lasers have advantages such as being smaller and cheaper to form than gas lasers, and consuming less power. On the other hand, however, this semiconductor laser currently has a problem in that its optical output is low, at most several tens of milliwatts (mW) when continuously driven. In addition, excitation light of various wavelengths may be required depending on the case to match the characteristics of the stimulable phosphor sheet and the characteristics of the photodetector that detects the stimulated luminescence light. The problem is that most of the wavelengths are in a relatively long wavelength region, and the degree of freedom in wavelength selection is low.

On the other hand, gas lasers such as He-Ne can obtain higher optical output than semiconductor lasers, and have a wide range of oscillation wavelengths from the ultraviolet to infrared regions, so they have a high degree of freedom in wavelength selection. Compared to semiconductor lasers, they have disadvantages of being expensive and large.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a point light source device that can be formed at low cost, has a high degree of freedom in wavelength selection, can generate a beam with high light intensity, and can be suitably used as an excitation light source as described above. That is.

(Means for Solving the Problems) The point light source device of the present invention includes a light source and an optical fiber wound around the light source multiple times. It is characterized by containing a phosphor that emits fluorescence.

(Function) Most of the fluorescence emitted from the above-mentioned phosphor is repeatedly totally reflected at the interface between the core portion and the cladding of the optical fiber, and travels toward one end surface of the fiber. Therefore, from the end face of this optical fiber, fluorescent light is emitted in a dotted form with high intensity, in the form of a collection of the energy of the light emitted by the light source.

Further, by selecting the emission wavelength of the light source and the above-mentioned phosphor according to the emission wavelength, light of a desired wavelength can be emitted from the optical fiber.

As a light source device that performs wavelength conversion using a phosphor, a combination of a light source and a light-concentrating plastic sheet containing a phosphor for wavelength conversion is known (see Japanese Patent Laid-Open No. 63-151261 by the present applicant). (see publication). However, this light source device is a linear light source device in which wavelength-converted light is emitted linearly from the end surface of the sheet, and as described in the above publication, when this linear light source device is used as an excitation light source for the above system, requires a pixel-divided line sensor as a photodetector to detect stimulated luminescence light.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 shows a point light source device 30 according to a first embodiment of the present invention, and FIG. 2 shows a radiation image information reading device using this point light source device 30 as an excitation light source. As shown in FIG. 1, this point light source device 30 includes: - a rod-shaped light source 31 such as a fluorescent lamp;
The optical fiber 32 is spirally wound many times around the periphery of the optical fiber 32. As shown in an enlarged view in FIG. 3, this optical fiber 32 has a core 32A made of plastic, for example, covered with a cladding 32B having a lower refractive index than the core 32A. It mainly receives light 33 with a wavelength of 480 nm and mainly receives light with a wavelength of 630 nm.
A phosphor that emits fluorescence of 13 nm is dispersed and contained.

Examples of the above-mentioned phosphors include dimethyl sulfoxide. Note that as the optical fiber 32, it is also possible to use one whose core is made of so-called scintillation glass containing phosphor. Further, the optical fiber 32 may be placed in close contact with the outer surface of the light source 31, or may be placed a little apart from it.

As shown in FIG. 2, the optical fiber 32 is arranged such that one end 32C thereof faces the optical deflector 14 such as a galvanometer mirror, and the other end 32C of the optical fiber 32
A photodetector 34 such as a photodiode is coupled to D. When reading radiation image information from the stimulable phosphor sheet IO, the light source 31 is turned on. Thereby,
As mentioned above, the phosphor in the core 32A mainly has a wavelength of 630
It emits fluorescence of 13 nm.

Most of this fluorescence 13 is caused by the core 32A as shown in FIG.
It undergoes repeated total reflection at the interface between the fiber and the cladding 32B and travels toward the fiber end faces 32C and 32D. The light beam (fluorescence) 13 emitted from the fiber end face 32C is converted into a parallel beam by the collimator lens 12.

As described above, this light beam 13 is emitted from the fiber end face 32C in a form in which the energy of the light 33 emitted from the light source 31 is concentrated, so that it can have extremely high light intensity. For example, if the light output of the light source 31 is 20W,
Even if the utilization efficiency is 1%, a light beam 13 of 200 mW can be obtained.

On the other hand, the stimulable phosphor sheet 10, on which radiographic image information of the subject is accumulated and recorded, for example by irradiating radiation that has passed through the subject, is transferred to the stimulable phosphor sheet 10 for sub-scanning with excitation light by a sheet transport means 11 such as an endless belt. It is transported in the direction of arrow Y. The light beam 13 is deflected by a light deflector 14 such as a galvanometer mirror, and main scans the stimulable phosphor sheet 10 in a direction X substantially perpendicular to the sub-scanning direction Y. Stimulated luminescent light 15 is emitted from the portion of the stimulable phosphor sheet 10 irradiated with the light beam 13 in an amount corresponding to the radiation image information stored and recorded.

This stimulated luminescence light 15 is detected by a long photomultiplier tube 17. The output S1 of the photomultiplier tube 17 indicating the amount of stimulated luminescence light 15 is input to the reading circuit 20, where it is amplified and
It undergoes processing such as logarithmic transformation. Further, this output S1 is subjected to integration processing at predetermined period intervals based on a synchronization signal S2 synchronized with the scanning of the light beam 13, and as a result, the reading circuit 20 outputs a pixel-divided time-series analog read image signal S3. Ru. This read image signal S3 is digitized by an A/D converter 21, for example, and then digitized by an image processing circuit 22.
After undergoing signal processing (image processing) such as gradation processing and frequency processing, the image reproduction device 2 such as a CRT or printer
3, and is used to reproduce the radiation image recorded on the stimulable phosphor sheet IO.

The elongated photomultiplier tube 17 is, for example, disclosed in Japanese Patent Application Laid-Open No. 1986-
16666, etc., and a stimulable phosphor sheet l is placed on a cylindrical main body 17A made of glass or the like.
The adapter 17 has an elongated light-receiving surface extending along the main scanning line of the light beam on O, and is mounted on the light-receiving surface.
B, the stimulated luminescence light 15 is photoelectrically detected via the filter 17c and the light guide 17D. That is, the stimulated luminescent light 15 enters into the light guide 17D from the elongated entrance surface 17d of the light guide 17D, and is guided therein to the light receiving surface side of the main body 17A.

The filter 17c allows the stimulated luminescence light 15 to pass therethrough, but absorbs the light beam 13 as excitation light reflected on the stimulable phosphor sheet 10 and does not allow it to enter the light-receiving surface.

Note that when the light source 31 is turned on with an alternating current of 50 Hz or 60 Hz, for example, a modulation component of this frequency may be superimposed on the output S1 of the photomultiplier tube 17.
It is preferable to use high frequency lighting or direct current. Furthermore, the light intensity of the fluorescence emitted from the end face 32D of the optical fiber 32 is proportional to (usually approximately equal to) the light intensity of the light beam 13 emitted from the end face 32C.
The intensity of the light beam 13 can be detected using a photodetector 34.

By doing so, fluctuations in the intensity of the light beam 13 can be monitored, and when the light source 31 is turned on with variable output, the output of the photodetector 34 is fed back to the light source lighting control circuit to stabilize the light output. It can also be controlled.

In addition to having a core 32A and a separate cladding 32B, the optical fiber 32 may be made of a refractive index gradient optical material in which the central portion has a relatively high refractive index and the surrounding portion has a relatively low refractive index. It is also possible to use the central portion as the core and the surrounding portion as the cladding.

Furthermore, the shape of the light source and the way of winding the optical fiber in the point light source device of the present invention are not limited to those in the above embodiments. For example, the point light source device 50 of the second embodiment shown in FIG.
For example, a substantially spherical light source 51 may be used, and an optical fiber 52 may be wound around it in the meridian shape of the earth. Further, the outer part of the optical fiber 52 wound in this way is provided with the light 53 emitted from the light source 51 into the optical fiber 52.
By providing a spherical reflecting plate 54 on the second side, it is possible to improve light utilization efficiency. This also applies to the embodiments described above.

The light source used in the point light source device of the present invention may be any light source as long as it emits light with a wavelength shorter than the emission wavelength of the phosphor contained in the core portion of the optical fiber. Specific examples thereof include: In addition to the above-mentioned fluorescent lamps, examples include mercury lamps, sodium lamps, electroluminescent panels, and the like.

In addition to the above-mentioned phosphors, the phosphor to be contained in the core of the optical fiber is disclosed in JP-A-56-36549, JP-A-56-104987, and JP-A-58-11.
Coumarin derivatives and thioxanthin derivatives described in JP-A No. 1886, JP-A-59-89302, etc.
Examples include organic phosphors such as perylene derivatives and boron complexes. As this phosphor, it is desirable to use a phosphor that exhibits little self-absorption of emitted fluorescence, that is, a phosphor that has a large so-called Stokes shift.

In the above, an embodiment has been described in which a stimulable phosphor sheet is irradiated with excitation light to emit stimulated luminescence light. It is also required in recording devices and the like, and the point light source device of the present invention can be applied to such devices as well.

In particular, the point light source device of the present invention can record light beams of three colors because the emission wavelength of the light source can be converted to obtain light of a desired wavelength depending on the selection of the phosphor contained in the core portion of the optical fiber. It can also be suitably used in a color image scanning and recording device that scans a material.

(Effects of the Invention) As explained in detail above, the point light source device of the present invention has a configuration in which the wavelength of the light emitted from the light source can be converted by the phosphor contained in the core portion of the optical fiber wound around the light source. Therefore, a light beam of a specific wavelength can be obtained freely. Furthermore, with the above configuration, light is emitted from the end face of the optical fiber in a form in which the energy of the light emitted by the light source is concentrated, so this point light source device makes it possible to obtain a light beam with extremely high light intensity. can. Furthermore, the point light source device of the present invention has an extremely simple configuration as described above.
Since a general and inexpensive light source such as a fluorescent lamp can be used as a light source, it can be formed at a sufficiently low cost.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a point light source device according to a first embodiment of the present invention. FIG. 2 is a schematic perspective view showing an example of a radiation image information reading device using the point light source device according to the first embodiment. FIG. 3 is a side view showing in detail the optical fiber of the point light source device of the first embodiment, and FIG. 4 is a partially cutaway plan view showing the point light source device of the second embodiment of the present invention. 13... Fluorescence 30.50... Point light source device 31, 51... Light source 32.52.
...Optical fiber 33.53...Light emitted by a light source 5
4...Reflector plate

Claims (1)

[Claims] A point light source device comprising a light source and an optical fiber that contains a phosphor in its core portion that emits fluorescence upon receiving the light emitted by the light source, and is wound multiple times around the light source.