WO2003023338A1

WO2003023338A1 - Infrared-visible conversion member and infrared detector

Info

Publication number: WO2003023338A1
Application number: PCT/JP2002/009232
Authority: WO
Inventors: Itaru Mizuno; Minoru Kondo; Atsushi Onoda; Kyozo Mizutani
Original assignee: Hamamatsu Photonics K.K.
Priority date: 2001-09-10
Filing date: 2002-09-10
Publication date: 2003-03-20
Also published as: JP2003083809A

Abstract

An infrared-visible conversion member which is disposed on the light receiving surface of a photodetector having a sensitivity to a visible light, and which comprises a substrate disposed on a visible light receiving surface and being transparent to a visible light, and a phosphor layer disposed on the substrate, containing an up-conversion phosphor for converting an infrared ray into a visible light, and having a film thickness of 5-120 μm. Accordingly, a high-level trade-off between a visible light emission intensity and resolution is enabled, and an excellent infrared detecting element can be implemented because an image by a visible light converted from an infrared ray can be detected with high sensitivity and high resolution.

Description

Itoda

Infrared-visible conversion member and infrared detector

The present invention relates to an infrared-visible conversion member and an infrared detector, and more particularly, to an infrared-visible conversion member that converts infrared light into visible light using a phosphor, and an infrared detection device using the member. Things.

Background art

In recent years, with the development of optical communication technology, the demand for an element that visually detects infrared light (for example, near-infrared light having a wavelength of 1.5 μm) is increasing. As such an infrared light detecting element, an image intensifier having an S-1 photocathode, an infrared vidicon, an InGaAs solid-state element, and the like are known. However, it is not always sufficient and has the disadvantage that the price is high. Therefore, development of an inexpensive infrared detecting element having high conversion efficiency and sensitivity is desired.

Against this background, the application of phosphors that convert infrared light to visible light (up-conversion phosphors) to infrared detectors is being studied. For example, an inorganic material containing a specific rare earth element has the property of converting infrared light into ultraviolet light by multiphoton excitation of rare earth ions, and is relatively inexpensive. Promising

(Japanese Unexamined Patent Application Publication No. Hei 6 — 256661, Japanese Unexamined Patent Application Publication No. 6_1-25050, Japanese Unexamined Patent Application Publication No. 6-247 741, Japanese Unexamined Patent Application Publication No. — No. 2 9 8 1 9 and Tokuhei Hei 8 — 6 9 0 25).

Disclosure of the invention

However, when the above up-conversion phosphor is applied to an infrared detector, sufficient characteristics can be obtained in terms of visible light emission intensity and resolution. However, such an infrared detecting element has not yet been practically used.

The present invention has been made in view of the above-mentioned problems of the related art, and has a sufficiently high visible light emission intensity and a high resolution when converting infrared light into visible light, and is an inexpensive infrared-visual conversion member. It is an object of the present invention to provide a sensitive and inexpensive infrared detector.

In order to achieve the above object, a first infrared-visible conversion member of the present invention comprises: an infrared-visible conversion member disposed on a light receiving surface of a photodetector having sensitivity to visible light; A substrate which is disposed on a surface and has transparency to visible light; and an upcoming phosphor which is disposed on the substrate and converts infrared light into visible light and has a film thickness of 5 to 12 And a phosphor layer having a thickness of 0 μm.

In the first infrared-visible conversion member of the present invention, when the phosphor layer is irradiated with infrared light, infrared rays are absorbed by an infrared exci- table phosphor (IEP) and visible light is re-emitted. . At this time, by setting the film thickness of the phosphor layer to 5 to 120 tm, it is possible to achieve both a high level of visible light emission intensity and high resolution. Therefore, by arranging the first infrared-visible conversion member such that the side closer to the light receiving surface of the photodetector is the substrate and the far side is the phosphor layer, the visible light converted from the infrared light is converted to the substrate. Since the image is transmitted to the light receiving surface of the photodetector via the optical sensor and the image of the visible light is detected with high sensitivity and high resolution, an excellent infrared detecting element can be realized.

The first infrared-visible conversion member of the present invention preferably further includes a visible light shielding layer that transmits infrared light and reflects or absorbs visible light, on the phosphor layer. This prevents visible light from entering the phosphor layer and allows infrared light to selectively enter the phosphor layer. As a result, the phosphor layer Since the visible light is substantially only the visible light emitted from the up-conversion phosphor, the resolution of the image detected by the photodetector can be improved.

Further, the first infrared-visible conversion member of the present invention is formed by integrating the substrate in a state where a plurality of optical fibers are bundled, and a plurality of cores for transmitting visible light incident from the phosphor layer. Preferably, the fiber optic plate has a lower refractive index than the core, and has a cladding covering each outer peripheral portion of the core. As a result, the absorption of infrared light by the substrate is suppressed, so that the sensitivity for detecting visible light by the photodetector can be improved.

In the first infrared-visible conversion member of the present invention, when the substrate is a fiber optic plate, the average particle size of the gap-compared phosphor is 1 Z 2 or less of the distance between adjacent cores. It is preferred that As a result, when the visible light from the up-conversion phosphor enters a predetermined core, the visible light is more reliably prevented from being incident on another core adjacent to the core. The sensitivity at the time of detection with a detector can be improved.

Further, the first infrared detection device of the present invention includes a photodetector having sensitivity to visible light, and the first infrared-visible conversion device of the present invention arranged on a light receiving surface of the photodetector. And a member. In the first infrared detection device of the present invention, by arranging the first infrared-visible conversion member of the present invention on the light-receiving surface of the photodetector, the first infrared-visible conversion member of the present invention can be used to convert infrared light into visible light. Both the light emission intensity and the resolution are compatible at a high level, and it is possible to detect an image by the converted visible light with high sensitivity and high resolution.

Further, the second infrared-visible conversion member of the present invention includes a substrate having transparency to infrared light, and an up-conversion member disposed on the substrate for converting infrared light into visible light. A phosphor layer containing an impregnated phosphor and having a film thickness of 5 to 120 m, wherein the phosphor layer is disposed on a light receiving surface of a photodetector having sensitivity to visible light. It is characterized by the following.

In the second infrared-visible conversion member of the present invention, by setting the thickness of the phosphor layer containing the up-compensation phosphor to 5 to 120 μιη, both the visible light emission intensity and the resolution are improved. It is the same as the first infrared-visible conversion member described above in that the compatibility can be achieved at a high level. Furthermore, the second infrared-visible conversion member is arranged such that the side closer to the light receiving surface of the photodetector is the phosphor layer and the far side is the substrate, so that the infrared light transmitted through the substrate is converted into visible light by the phosphor layer. After being converted to the light, the light is directly transmitted to the light receiving surface of the photodetector, so that deterioration of the image due to visible light can be sufficiently prevented. Further, since the substrate prevents the phosphor layer from being damaged, the above-mentioned excellent characteristics can be stably obtained over a long period of time.

The infrared-visible conversion member of the present invention preferably further includes, on the phosphor layer, a visible light shielding layer that transmits infrared light and reflects or absorbs visible light. This prevents visible light from entering the phosphor layer and allows infrared light to selectively enter the phosphor layer. As a result, the visible light from the phosphor layer is substantially only the visible light emitted from the up-compared phosphor, so that the resolution of the image detected by the photodetector can be improved. Further, the infrared detection device of the present invention comprises: a light detector having sensitivity to visible light;

And the above-mentioned second infrared-visible conversion member of the present invention, which is arranged on the light receiving surface of the photodetector.

In the infrared detector of the present invention, by arranging the second infrared-visible conversion member of the present invention on the light receiving surface of the light detector, the visible light emission intensity and the infrared light conversion at the time of conversion from infrared light to visible light are improved. Both resolutions are compatible at a high level and can be converted It is possible to detect an image by visual light with high sensitivity and high resolution. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic configuration diagram showing an infrared detector according to the first embodiment. FIG. 2 is a graph showing the correlation between the thickness of the phosphor layer and the light intensity.

FIG. 3 is a graph showing the correlation between the thickness of the phosphor layer and the resolution.

FIG. 4 is a graph showing the correlation between the thickness of the phosphor layer and the relative luminance. Fig. 5 is a graph showing the infrared absorption spectrum of water glass.

FIG. 6 is a schematic sectional view showing an example of a fiber optic plate. FIG. 7 is a schematic configuration diagram showing an infrared detector according to the second embodiment. FIG. 8 is a schematic sectional view showing an infrared-visible conversion member according to the third embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a schematic configuration diagram showing a first embodiment according to the infrared-visible conversion member of the present invention. Fig. 1 shows an infrared detector equipped with a CCD image sensor as an image sensor. An infrared-visible conversion member 2 a is arranged on the light receiving surface of the light of the CCD image sensor 1. The driver 5 is electrically connected to the CCD image sensor 1.

The infrared-visible conversion member 2 a is obtained by laminating a phosphor layer 3 containing an upcomparation phosphor on a fiber optic plate (FOP) 4. The thickness of the phosphor layer 3 is set in the range of 5 to 12. The phosphor layer 3 is disposed farther from the light receiving surface of the CCD image sensor 1 and the FOP 4 is disposed closer to the light receiving surface. The up-conversion phosphor contained in the phosphor layer 3 absorbs infrared light and re-emits visible light. This conversion from infrared light to visible light does not require pre-excitation. Such up-conversion phosphors include, for example, rare earth elements or compounds thereof, more specifically, erbium (Er), yttrium (Y), ytterbium (Yb), and dysprosium.

(Dr), thulium (Tm), samarium (Sm), and inorganic materials containing these halides (fluoride, chloride). By using these inorganic materials, infrared light of a specific wavelength (eg, 1.5 m) can be converted to visible light of a specific wavelength (eg, 550 nm, 660 nm). One of the above up-conversion phosphors may be used alone, or two or more may be used in combination.

Here, the correlation between the thickness of the phosphor layer 3 and the visible light emission intensity is shown in Fig. 2, the correlation between the thickness of the phosphor layer 3 and the resolution is shown in Fig. 3, and the correlation between the thickness of the phosphor layer 3 and the relative luminance is shown. The correlation is shown in FIG. As shown in FIGS. 2 and 3, the visible light emission intensity and the resolution show different dependencies on the thickness of the phosphor layer 3. In the present embodiment, by setting the thickness of the phosphor layer 3 to 5 to 120; zm, both the visible light emission intensity and the resolution can be compatible at a high level. Thus, a sufficiently high relative luminance can be achieved as shown in FIG. If the thickness of the phosphor layer 3 exceeds 120 μm, at least one of the visible light emission intensity and the resolution becomes insufficient, while the thickness of the phosphor layer 3 is less than 5 μm In the case of (1), it becomes difficult to form a uniform phosphor layer, and in any case, the above effects cannot be obtained.

The phosphor layer 3 can be formed by, for example, a centrifugal sedimentation method. In other words, a predetermined amount of the fine particles of the up-conversion phosphor corresponding to the thickness of the phosphor layer 3 is added to a water glass solution to form a suspension, and this suspension is placed on a predetermined surface of the FOP 4. Apply. Sedimentation of the up-conversion phosphor in the suspension After being deposited on the FOP 4, the phosphor layer 3 is obtained by sucking and drying the water glass solution by suction or the like.

The phosphor layer 3 thus obtained may contain water glass. Figure 5 shows the infrared absorption spectrum of water glass. As shown in the figure, water glass shows almost no absorptivity to infrared light, so that it can be used as a binder for binding the up-compensation phosphor. The binder of the phosphor layer 3 is not particularly limited as long as it transmits infrared light, and an organic binder or the like may be used in addition to the water glass. The visible light from the phosphor layer 3 is transmitted to the CCD image sensor 1 by the FOP4. FIG. 6 is a cross-sectional view of the FOP 4 perpendicular to the optical path direction. The FOP 4 includes a plurality of cores 11 made of a core glass having a high refractive index, a clad 12 made of a clad glass having a lower refractive index than the core glass, and covering each outer peripheral portion of the core 11, An absorber 13 made of an absorber glass exhibiting absorptivity to visible light and disposed between the cores 11.

The visible light that has entered the FOP 4 repeats total reflection within the core 11 and is transmitted from the light receiving surface to the emission surface. At this time, light (stray light) leaking from the core 11 without total reflection may be generated. However, such stray light is absorbed by the absorber 13 to prevent the stray light from entering the other cores 2. Thus, the FOP 4 allows the visible light from the phosphor layer 3 to be transmitted to the CCD image sensor 1 with a sufficiently high resolution.

Here, it is preferable that the average particle diameter of the up-compensation phosphor contained in the phosphor layer 3 is not more than の of the distance d between the adjacent cores 11. For example, when the distance d between the cores is 6 Aim, the average particle size of the up-conversion phosphor is preferably 3 μm or less (more preferably, 2 μm or less). The average particle size of the upcomparation phosphor is If it exceeds 1/2, when visible light from the upcoming phosphor enters the predetermined core, the visible light is also likely to enter other cores adjacent to the core, and the CCD image sensor The resolution of the image detected in step 1 tends to decrease.

As described above, in the first embodiment, by setting the thickness of the phosphor layer 3 including the up-conversion phosphor to 5 to 120; m, the up-conversion phosphor absorbs infrared light and becomes visible. When light is re-emitted, both visible light emission intensity and resolution can be compatible at a high level. Further, by transmitting the visible light from the infrared-visible conversion member 2a to the CCD image sensor 1 by the FOP 4, the resolution of the image by the visible light is maintained at a high level. Can be detected with high sensitivity.

For example, in the infrared detector of the first embodiment, when the thickness of the phosphor layer 3 is 5 μμπι, and infrared light having an intensity of 156.7 W is incident thereon, a peak of 797 counts is obtained. Was detected (gamma value: 1.4). This result indicates that the infrared detector has sufficient sensitivity for detecting the position of the laser beam.

Note that the first embodiment is not limited to this. For example, the apparatus shown in FIG. 1 has a CCD image sensor 1 as an image sensor, but a MOS image sensor may be used instead of the CCD image sensor 1. Thereby, an image with visible light from the infrared-visible detection member 2 can be detected with high sensitivity.

In the present embodiment, an organic film (for example, polyparaxylylene) may be further provided on the phosphor layer 3. This prevents the phosphor layer 3 from being damaged, so that the above excellent characteristics can be obtained for a long period of time. FIG. 7 is a schematic configuration diagram showing a second embodiment according to the present invention. Figure 7 shows an infrared detector equipped with a Si photodiode as a photodetector.The phosphor layer 3 is placed on the light receiving surface of the Si photodiode 6 and a glass plate 7 that transmits infrared light. The infrared-visible conversion member 2b is formed by laminating in order, and the thickness of the phosphor layer 3 is set within a range of 5 to 120 μιη.

As described above, also in the second embodiment, when the thickness of the phosphor layer 3 is set to 5 to 120 m, the up-conversion phosphor absorbs infrared light and re-emits visible light. Thus, both the visible light emission intensity and the resolution can be compatible at a high level, and the visible light can be detected with high sensitivity by the S 1 photodiode 6. Further, in the second embodiment, by disposing the phosphor layer 3 and the glass plate 7 on the light receiving surface of the Si photodiode 6 in this order, the infrared light transmitted through the glass plate 7 is After being converted into visible light by the light source, the light is directly transmitted to the light receiving surface of the Si photodiode 6, so that light attenuation can be sufficiently prevented. Further, since the glass plate 7 prevents the phosphor layer 3 from being damaged, the above-mentioned excellent characteristics can be stably obtained over a long period of time.

Note that the second embodiment is not limited to this. For example, a CCD image sensor or a MOS type image sensor may be used as an image pickup device instead of the Si photodiode 6 which is a photodetector. In the case of using an image sensor, the deterioration of the resolution can be prevented by disposing the phosphor layer 3 on the light receiving surface of the image sensor, whereby the image by the visible light from the infrared-visible conversion member 2 can be highly sensitive. Can be detected.

FIG. 8 is a schematic configuration diagram showing a second embodiment according to the present invention. In FIG. 8, a phosphor layer 3 having a thickness of 5 to 12 μm and a visible light shielding layer 8 are laminated in this order on the FOP 4 to constitute an infrared-visible conversion member 2. ing Visible light blocking layer 8 is composed of a S i O ₂ layer and T i 0 ₂ layers are stacked in a plurality alternately on the planarization layer 9 formed on the phosphor layer 3 dielectric multilayer reflection film, a fluorescent Approximately 90% of infrared light incident on the body layer 3 is transmitted, while 90% or more of visible light incident on the phosphor layer 3 is reflected. It should be noted that a dielectric multilayer reflective film formed on a flat substrate that absorbs visible light and transmits infrared light may be bonded to the phosphor layer 3.

In the third embodiment, by setting the thickness of the phosphor layer 3 containing the up-compensation phosphor to 5 to 120 μππ, the up-compensation phosphor absorbs infrared light and regenerates visible light. It is the same as in the first and second embodiments that both the emission intensity of visible light and the resolution can be compatible at a high level when emitting. In addition, in the third embodiment, a visible light shielding layer 8 is further provided on the phosphor layer 3 to suppress the incidence of visible light on the phosphor layer and to select infrared light for the phosphor layer 3. Since it is possible to make the incident light incident, the resolution of the image by the visible light converted from the infrared light can be further improved.

Note that the third embodiment is not limited to this. For example, the visible light shielding layer 8 only needs to reflect or absorb visible light and transmit infrared light. Instead of the multilayer reflective film, the visible light shielding layer 8 absorbs visible light and transmits infrared light. An Si substrate can also be used.

Further, although the image sensor is not shown in FIG. 8, as in the first embodiment, the infrared-visible conversion member 2 is subjected to force coupling so that the surface on the FOP 4 side is on the light receiving surface of the image sensor. By doing so, an infrared detector can be obtained. In addition, any of a CCD image sensor, a MOS image sensor, and a Si photodiode may be used as such an image sensor. Industrial applicability As described above, according to the infrared-visible conversion member of the present invention, by setting the thickness of the phosphor layer to 5 to 120 m, both the visible light emission intensity and the resolution can be achieved at a high level. Becomes possible. Therefore, by arranging the infrared-visible conversion member of the present invention on the light-receiving surface of a photodetector having sensitivity to visible light, an image formed by the visible light converted from the infrared light has high sensitivity and high resolution Therefore, an excellent infrared detecting element can be realized.

Claims

Scope of Word

1. In the infrared-visible conversion member arranged on the light receiving surface of a photodetector having sensitivity to visible light,

A substrate disposed on the light receiving surface and having transparency to visible light; and an upcomparation phosphor for converting infrared light to visible light, which is disposed on the substrate and having a film thickness of 5 A phosphor layer having a thickness of ~ 120 //; m.

2. The infrared-visible conversion member according to claim 1, further comprising a visible light shielding layer that transmits infrared light and reflects or absorbs visible light, on the phosphor layer.

3. The substrate is

A plurality of cores formed by integrating a plurality of optical fibers in a bundled state, and a plurality of cores for transmitting visible light incident from the phosphor layer;

A clad having a lower refractive index than the core and covering each outer peripheral portion of the core;

The infrared-visible conversion member according to claim 1, which is a fiber optic plate having:

4. The infrared-visible conversion member according to claim 3, wherein the average particle diameter of the gap-compared phosphor is 1 to 2 or less as the distance between adjacent cores.

5. a photodetector sensitive to visible light;

The infrared-visible conversion member according to claim 1, which is disposed on a light receiving surface of the photodetector.

An infrared detection device comprising:

6. a substrate having a transmittance to infrared light;

A phosphor layer which is disposed on the substrate, contains an up-conversion phosphor for converting infrared light into visible light, and has a film thickness of 5 to 120 μm; An infrared-visible conversion member, wherein the phosphor layer is disposed on a light receiving surface of a photodetector having sensitivity to visible light.

7. The infrared-visible conversion member according to claim 6, further comprising a visible light shielding layer that transmits infrared light and reflects or absorbs visible light on the phosphor layer.

8. a photodetector sensitive to visible light;

The infrared-visible conversion member according to claim 6, which is disposed on a light receiving surface of the photodetector,

An infrared detection device comprising: