JP2000128569A - Low fluorescent optical glass and fluorescence microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the intensity of fluorescent light due to excitation by UV rays and to obtain high transmittance for rays in a UV region by incorporating a specified amt. of Yb2O3. SOLUTION: Yb2O3 which is effective to increase the refractive index and to decrease fluorescent light is incorporated by 1 to 50 wt.% as the essential components of an optical glass. If the amt. exceeds 50 wt.%, stability against devitrification decreases. The optical glass essentially composed of Yb2O3, B2O3 and La2O3 or the like is produced by using oxides, carbonates, nitrates, metaphosphates or the like as the source material corresponding to each component, weighing these compds. in desired proportions, and mixing enough in a powder or liquid state to prepare the source material. The prepared source material is introduced into a quartz or platinum crucible in an electric furnace heated to 1100 to 1400 deg.C for example, and the source material is molten, refined, stirred and homogenized, and then cast into a preliminarily heated iron casting mold, and slowly cooled. The obtd. optical glass is useful for the optical system of a fluorescent microscope or the like in which especially fluorescence in the optical glass causes problems concerning to the observation and measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical glass having a small fluorescence intensity when excited by ultraviolet light. Further, the present invention relates to a fluorescence microscope using the optical glass.

[0002]

2. Description of the Related Art In the fields of biology, medicine, and the like, a specimen (observation target) is irradiated with excitation light, such as ultraviolet rays, to observe biological tissues, cells, bacteria, and the like. The method of observing and measuring is often used. In recent years, techniques for detecting weak fluorescence from a very small amount of bacteria, cells, and the like have been actively studied. In an optical glass used for an objective lens or the like of a fluorescence microscope used in such a technique, fluorescence emitted from the optical glass due to excitation of ultraviolet rays becomes noise in observation and measurement, and is beginning to be regarded as a problem.

[0003] That is, there is an increasing demand for an optical glass having a small fluorescence intensity of the optical glass due to excitation of ultraviolet light, which causes noise during observation and measurement. 2. Description of the Related Art An optical system such as an objective lens, which is highly aberration-corrected, is composed of a plurality of optical glasses having various refractive indexes and dispersions. As a low refractive index low dispersion optical glass useful for aberration correction, a fluorophosphate optical glass is generally known. The fluorescent intensity of an optical glass having a fluorophosphate composition is low when excited by ultraviolet light.

For example, Japanese Patent Application Laid-Open No. 3-500162, entitled "Fluorophosphate Optical Glass Having Positive Anomalous Partial Dispersion and Method for Producing the Same" discloses that the positive anomalous partial dispersion ratio Δνe is +11.
Between 8 and +12.5, the refractive index ne is 1.53 and 1.55
And an Abbe number ve between 72.8 and 73.5 is disclosed.

[0005]

On the other hand, as high-refractive-index, high-dispersion optical glasses, various optical glasses which do not use PbO containing SiO ₂ , alkali metal oxide, and TiO ₂ as essential components have been developed. . However, sufficient consideration has not been given to fluorescence by ultraviolet excitation and light transmittance in the ultraviolet region, and it cannot be said that the optical system is suitable for an optical system for observing weak fluorescence from a specimen by excitation light in the ultraviolet region. . In response to this problem, research and development have been energetically advanced in recent years, and a low-fluorescent optical glass containing P ₂ O ₅ , Ta ₂ O ₅ , and Nb ₂ O ₅ as essential components has been disclosed in Japanese Patent Application No. 8-315146, “Low Fluorescent Optical glass ".

However, with regard to high-refractive-index low-dispersion glass containing B ₂ O ₃ and La ₂ O ₃ as main components, sufficient consideration has not been given to fluorescence by ultraviolet excitation and light transmittance in the ultraviolet region. It is hard to say that it is suitable for an optical system for observing weak fluorescence from a specimen due to ultraviolet excitation light. An object of the present invention is to provide a novel optical glass which has a low fluorescence intensity due to ultraviolet excitation and is particularly useful for an optical system such as a fluorescence microscope which has a problem of fluorescence from an optical glass.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional high-refractive-index, low-dispersion optical glass. The present inventors have conducted intensive studies to achieve the above object. As a result, the optical glass composition containing Yb ₂ O ₃ as an essential component has a low fluorescence intensity due to a desired ultraviolet excitation within a predetermined composition range. Further, the present inventors have found that high light transmittance in the ultraviolet region can be realized, and have accomplished the present invention.

That is, the present invention provides a weight ratio (hereinafter referred to as wt.
%), Wherein Yb ₂ O ₃ is contained in an amount of 1% by weight or more and 50% by weight or less, and an optical glass characterized by having a small fluorescence intensity by ultraviolet excitation. Such an optical glass is particularly useful for an optical system such as a fluorescence microscope where fluorescence from the optical glass poses a problem.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The above composition range has been found experimentally, and the reasons for limiting the composition range are as follows. Yb ₂ O ₃ is useful for increasing the refractive index and realizing low fluorescence, and is an essential component in the present invention.
However, if the content is less than 1 wt%, a sufficient effect cannot be obtained.
If the content exceeds wt%, the stability against devitrification decreases.
Preferably it is 1 to 50 wt%.

[0010]

EXAMPLES Next, examples of working compositions according to the present invention (numerical values are wt.
%) Are shown in Table 1 together with the optical constants (nd, νd) and the fluorescence intensity by ultraviolet excitation. For measurement of the fluorescence intensity, flint glass used as a standard sample in "Method for measuring the fluorescence of optical glass (JOGIS03-1975)" specified by the Japan Optical Glass Industrial Association was used as a standard. The optical glass prepared with the above working composition, the optical glass of the comparative example and the standard sample were processed into a size of 12 × 12 × 20 mm,
Three of the 20 mm surfaces were polished to obtain a fluorescence intensity measurement sample. Excitation light was incident on the opposing polished surfaces of these measurement samples, and the fluorescence emitted from the polished surface in a direction perpendicular to the excitation light was measured using a commercially available fluorescence spectrophotometer. The measurement sample is excited at a wavelength of 365 nm, and 400 to 700 n
The fluorescence spectrum in the wavelength range of m was measured, and the height of the highest fluorescence peak in this wavelength range was defined as the peak height of each glass. The evaluation is 365 for the standard sample.
Since the fluorescence intensity due to nm excitation was very large, the relative intensity ratio was set to 1/50 of the peak height of the standard sample.

The optical glass according to the present invention uses corresponding oxides, carbonates, nitrate metaphosphates and the like as raw materials of the respective components, weighs them in desired ratios, and thoroughly mixes them with powder or liquid. To form a blended raw material,
It was introduced into a quartz crucible or a platinum crucible in an electric furnace heated to 0 to 1400 ° C., melted, clarified, stirred and homogenized, cast into a pre-heated iron mold, and gradually cooled to produce.

[0012]

[Table 1]

According to this, when comparing the embodiment of the present invention and the comparative example having very similar components, it is understood that the fluorescence intensity of the optical glass of the embodiment of the present invention containing a specific amount of Yb ₂ O ₃ is extremely low.

[0014]

According to the present invention, the optical glass of the present invention containing Yb ₂ O ₃ as an essential component has a low fluorescence intensity,
An optical glass excellent in light transmittance in the ultraviolet region, chemical durability, and stability against devitrification, particularly a high-refractive-index low-fluorescent optical glass can be obtained. Furthermore, by using the optical glass of the present invention having a small fluorescence intensity due to ultraviolet excitation for a fluorescence microscope or the like, it becomes possible to solve the problem due to fluorescence.

Continued on the front page F term (reference) 2G043 AA03 BA16 CA03 DA06 EA01 FA02 GA02 GA04 GB28 HA01 LA01 LA05 MA01 2H052 AA09 AB01 AC12 2H087 KA09 UA00 4G062 AA04 BB08 DA01 DA02 DA03 DB01 DB02 DB03 DC04 DC05 DD01 DE01 EA01 EC01 ED01 ED02 ED03 EE01 EE02 EE03 EE04 EF01 EG01 EG02 EG03 FA01 FB01 FC01 FC02 FC03 FD01 FE01 FF01 FG01 FH01 FH02 FH03 FJ01 FJ02 FJ03 FJ04 FK03 FK04 FK05 FL01 GA01 GB01 H01 H01 H01 H01 H01 H01 H JJ07 JJ10 KK01 KK03 KK05 KK07 KK08 KK10 MM02 NN01 NN34 NN40

Claims (2)

[Claims] (1) Yb ₂ O ₃ is added at a weight ratio (hereinafter, wt%) of 1 w
An optical glass containing at least t% and not more than 50 wt% and having a low fluorescence intensity when excited by ultraviolet light. 2. A fluorescence microscope using the low-fluorescence optical glass according to claim 1.