Optical glass, optical element, optical system, cemented lens, objective lens for microscope, interchangeable camera lens, and optical device

Abstract

The optical glass has the following, indicated in mole%: a content of SiO2 of at least 15% and not more than 55%; a content of Al2O3 of at least 7% and not more than 42%; a total content of TiO2 and Nb2O5 (TiO2 + Nb2O5) of at least 0% and not more than 21%; a total content of La2O3, Y2O3, ZrO2, and Ta2O5 (La2O3 + Y2O3 + ZrO2 + Ta2O5) of at least 15% and not more than 55%; and a total content of Al2O3, TiO2, ZrO2, Nb2O5, and Ta2O5 (Al2O3 + TiO2 + ZrO2 + Nb2O5 + Ta2O5) of at least 32% and not more than 65%.

Description

Optical glass, optical elements, optical systems, cemented lenses, objective lenses for microscopes, interchangeable lenses for cameras, and optical devices

[0001] The present invention relates to optical glass, optical elements, optical systems, cemented lenses, microscope objective lenses, interchangeable camera lenses, and optical devices. This invention claims priority to Japanese Patent Application No. 2023-217061 filed on December 22, 2023, and the contents of that application are incorporated by reference into this application in designated states where incorporation by reference of documents is permitted.

[0002] Optical glass is used in a variety of optical elements and optical devices. For example, Patent Document 1 discloses optical glass used in various lenses.

[0003] Japanese Patent Application Laid-Open No. 2006-219365

[0004] The first aspect of the present invention is a composition containing, in mol %, SiO ２ Content: 15% or more and 55% or less, Al ２ O ３ Content rate: 7% or more and 42% or less, TiO ２ and Nb ２ O ５ The total content of (TiO ２ +Nb ２ O ５ ): 0% or more and 21% or less, La ２ O ３ , Y ２ O ３ , ZrO ２ and Ta ２ O ５ Total content (La ２ O ３ +Y ２ O ３ + ZrO ２ +Ta ２ O ５ ): 15% or more and 55% or less, Al ２ O ３ , TiO ２ , ZrO ２ , Nb ２ O ５ and Ta ２ O ５ The total content of Al ２ O ３+ TiO ２ + ZrO ２ +Nb ２ O ５ +Ta ２ O ５ ): 32% or more and 65% or less.

[0005] Another aspect of the present invention is an optical element using the above-mentioned optical glass.

[0006] Another aspect of the present invention is an optical system including the optical element described above.

[0007] Another aspect of the present invention is an objective lens for a microscope, which includes an optical system including the optical element described above.

[0008] Another aspect of the present invention is an interchangeable lens for a camera, which includes an optical system including the optical element described above.

[0009] Another aspect of the present invention is an optical device including an optical system including the optical element described above.

[0010] Another aspect of the present invention is a cemented lens having a first lens element and a second lens element, at least one of the first lens element and the second lens element being made of the optical glass described above.

[0011] Another aspect of the present invention is an optical system including the cemented lens described above.

[0012] Another aspect of the present invention is an objective lens for a microscope, which includes an optical system including the cemented lens described above.

[0013] Another aspect of the present invention is an interchangeable lens for a camera, which includes an optical system including the cemented lens described above.

[0014] Another aspect of the present invention is an optical device including an optical system including the above-described cemented lens.

[0015] FIG. 1 is a perspective view showing an example in which the optical device according to the present embodiment is used as an imaging device; FIG. 2 is a schematic view showing another example in which the optical device according to the present embodiment is used as an imaging device, and is a front view of the imaging device; FIG. 3 is a schematic view showing another example in which the optical device according to the present embodiment is used as an imaging device, and is a rear view of the imaging device; FIG. 4 is a block diagram showing an example of the configuration of a multiphoton microscope according to the present embodiment; FIG. 5 is a schematic view showing an example of a cemented lens according to the present embodiment; FIG. 6 is a schematic view showing the overall configuration of a gas jet type levitation furnace according to the present embodiment; FIG. 7 is an enlarged schematic view of a pedestal on a stage of the gas jet type levitation furnace according to the present embodiment; ｄ -P ｇ，Ｆ ) is plotted. The dotted line indicates P ｇ,Ｆ = -0.00204 × ν ｄ +0.657 and P ｇ,Ｆ = -0.00204 × ν ｄ +0.640. The optical constants (ν ｄ -n ｄ ) is a graph plotting the optical constants (ν ｄ -λ ５ ) is plotted. The dotted line indicates λ ５ = -5.625 × ν ｄ +535 and λ ５ = -5.625 × ν ｄ Indicates +542.

[0016] An embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described below. The present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be practiced with appropriate modifications within the scope of its gist.

[0017] Unless otherwise specified, the content of each component in this specification is expressed as mol % (mol percentage) relative to the total number of moles of the glass in terms of oxides. Note that the oxide-equivalent composition referred to here is a composition in which each component contained in the glass is expressed as 100 mol %, assuming that the oxides, composite salts, etc. used as raw materials for the glass constituent components of this embodiment are all decomposed and converted to oxides during melting.

[0018] The expression "not containing Q component" means that the Q component is substantially not contained, and indicates that the content of this component is at or below the impurity level. At or below the impurity level, for example, means less than 0.01%.

[0019] The expression "devitrification resistance" refers to the resistance of glass to devitrification. Here, "devitrification" refers to a phenomenon in which glass loses transparency due to crystallization or phase separation that occurs when the temperature of glass is raised to or above its glass transition temperature or when the temperature is lowered from a molten state to or below its liquidus temperature.

[0020] <Optical Glass> The optical glass according to this embodiment contains, in mol %, SiO ２ Content: 15% or more and 55% or less, Al ２ O ３ Content rate: 7% or more and 42% or less, TiO ２ and Nb ２ O ５ The total content of (TiO ２ +Nb ２ O ５ ): 0% or more and 21% or less, La ２ O ３ , Y ２ O ３ , ZrO ２ and Ta ２ O ５ Total content (La ２ O ３ +Y ２ O ３ + ZrO ２ +Ta ２ O ５ ): 15% or more and 55% or less, Al ２ O ３ , TiO ２ , ZrO ２ , Nb ２ O ５ and Ta ２ O ５ The total content of Al ２ O ３ + TiO ２ + ZrO ２ +Nb ２ O ５ +Ta ２ O ５): 32% or more and 65% or less.

[0021] The optical glass according to this embodiment contains La as a high refractive index, high transmittance component. ２ O ３ YaTa ２ O ５ and the like, and as a low specific gravity stabilizing component, SiO ２ and Al ２ O ３ The optical glass according to this embodiment has a high refractive index, high ultraviolet transmittance, low specific gravity, and high thermal stability (T ｘ -T ｇ ) and can stably produce large glass gobs using the levitation melting method.

[0022] First, each component of the optical glass according to this embodiment will be described.

[0023] SiO ２ is a component that maintains a low specific gravity and improves stability against devitrification, but also reduces the refractive index. It also constitutes a network-forming oxide and is a component that can improve melting properties. SiO ２ If the content of SiO is too low, the viscosity will decrease, and if it is too high, the refractive index will decrease. ２ The content of is 15% or more and 55% or less in mole percent. The lower limit of this content is preferably 18%, more preferably 22%, and even more preferably 27%. The upper limit of this content is preferably 50%, more preferably 42%, and even more preferably 35%.

[0024] Al ２ O ３ is a component that maintains a low specific gravity and enhances stability against devitrification, but is also a component that reduces the refractive index, partial dispersion ratio, and meltability. ２ O ３ If the content of Al is too low, the melt stability will decrease, and if it is too high, the refractive index will decrease. ２ O ３The content of is 7% or more and 42% or less in mole percent. The lower limit of this content is preferably 10%, more preferably 15%, and even more preferably 19%. The upper limit of this content is preferably 35%, more preferably 30%, and even more preferably 27%.

[0025] TiO ２ is a component that can increase the refractive index and maintain a low specific gravity, but it is also a component that reduces the transmittance. ２ If the content of TiO is too low, the specific gravity becomes high, and if it is too high, the transmittance decreases. ２ The content of is 0% or more and 5% or less in mole %. The upper limit of this content is preferably 3%, more preferably 2%, and even more preferably 1%.

[0026] Nb ２ O ５ is a component that increases the refractive index, but also decreases the transmittance and dispersion. ２ O ５ If the content of Nb is too low, the refractive index will be low, and if it is too high, the transmittance will be low. ２ O ５ The content of is 0% or more and 21% or less in mole %. The upper limit of this content is preferably 15%, more preferably 10%, and even more preferably 5%.

[0027] La ２ O ３ is a component that increases the refractive index and transmittance without impairing the devitrification resistance stability, but it is also a component that increases the specific gravity. ２ O ３ If the content of La is too low, the transmittance will decrease, and if it is too high, the specific gravity will increase. ２ O ３ The content of is 0% or more and 33% or less in mole percent. The lower limit of this content is preferably 5%, more preferably 9%, and even more preferably 13%. The upper limit of this content is preferably 30%, more preferably 26%, and even more preferably 22%.

[0028] Y ２ O ３ is a component that increases the refractive index and transmittance. ２ O ３ If the content of Y is too low, the refractive index will be low, and if it is too high, the melting property will be reduced. ２ O ３ The content of is 0% or more and 10% or less in mole %. The upper limit of this content is preferably 6%, more preferably 3%, and even more preferably 1%.

[0029] ZrO ２ is a component that increases the refractive index and transmittance, and also increases the stability against devitrification. ２ If the content of ZrO is too low, the melting property will be reduced, and if it is too high, the stability against devitrification will be reduced. ２ The content of is 0% or more and 23% or less in mole percent. The lower limit of this content is preferably 3%, more preferably 7%, and even more preferably 11%. The upper limit of this content is preferably 20%, more preferably 18%, and even more preferably 17%.

[0030] Ta ２ O ５ is a component that increases the refractive index and transmittance, but is also a component that increases the specific gravity and stability against devitrification. ２ O ５ If the content of Ta is too low, the refractive index will decrease, and if it is too high, the specific gravity will increase. ２ O ５ The content of is 0% or more and 25% or less in mole percent. The lower limit of this content is preferably 5%, more preferably 8%, and even more preferably 10%. The upper limit of this content is preferably 21%, more preferably 18%, and even more preferably 16%.

[0031] BaO is a component that reduces dispersion while maintaining the devitrification resistance of optical glass. However, if the BaO content is too low, the devitrification resistance decreases, and if it is too high, the melting property decreases. From this perspective, the BaO content is 0% or more and 25% or less in mol %. The lower limit of this content is preferably 1%, more preferably 5%, and even more preferably 12%. The upper limit of this content is preferably 23%, more preferably 19%, and even more preferably 15%.

[0032] B ２ O ３ is a component for forming a network-forming oxide. ２ O ３ Since B is a highly volatile component, if it is incorporated in excess, it may cause fluctuations in the composition of the glass during production, and may make striae more apparent. ２ O ３ The content of B is 0% or more and 5% or less in mole %. The upper limit of this content is preferably 3%, more preferably 2%, and even more preferably 1%. Most preferably, B ２ O ３ Does not contain.

[0033] TiO ２ and Nb ２ O ５ The total content of (TiO ２ +Nb ２ O ５ ) is 0% or more and 21% or less. The upper limit of this total content is preferably 15%, more preferably 10%, and even more preferably 5%. ２ and Nb ２ O ５ The total content of (TiO ２ +Nb ２ O ５ By setting the value of (a) to be within this range, a decrease in transmittance can be suppressed and high transmittance can be obtained.

[0034] Al ２ O ３ , TiO ２ , ZrO ２ , Nb ２ O ５ and Ta２ O ５ The total content of Al ２ O ３ + TiO ２ + ZrO ２ +Nb ２ O ５ +Ta ２ O ５ ) is 32% or more and 65% or less. The lower limit of this total content is preferably 37%, more preferably 40%, and even more preferably 43%. The upper limit of this total content is preferably 59%, more preferably 55%, and even more preferably 52%. ２ O ３ , TiO ２ , ZrO ２ , Nb ２ O ５ and Ta ２ O ５ The total content of Al ２ O ３ + TiO ２ + ZrO ２ +Nb ２ O ５ +Ta ２ O ５ By setting the content of α-to-β-block copolymer in this range, it is possible to improve the stability against devitrification during melting, and to simultaneously achieve a high refractive index and a high transmittance.

[0035] La ２ O ３ , Y ２ O ３ , ZrO ２ and Ta ２ O ５ Total content (La ２ O ３ +Y ２ O ３ + ZrO ２ +Ta ２ O ５ ) is 15% or more and 55% or less. The lower limit of this total content is preferably 20%, more preferably 25%, and even more preferably 30%. The upper limit of this total content is preferably 50%, more preferably 45%, and even more preferably 40%. ２ O ３ , TiO ２ , ZrO２ , Nb ２ O ５ and Ta ２ O ５ The total content of Al ２ O ３ + TiO ２ + ZrO ２ +Nb ２ O ５ +Ta ２ O ５ ) in this range, the refractive index and transmittance can be increased.

[0036] SiO ２ and Al ２ O ３ The total content (SiO ２ +Al ２ O ３ ) is 42% or more and 75% or less. The lower limit of this total content is preferably 44%, more preferably 47%, and even more preferably 50%. The upper limit of this total content is preferably 70%, more preferably 65%, and even more preferably 60%. SiO ２ and Al ２ O ３ The total content (SiO ２ +Al ２ O ３ By setting the specific gravity within this range, it is possible to suppress a decrease in the refractive index while maintaining a low specific gravity.

[0037] In addition, if necessary, suitable amounts of known clarifiers, colorants, defoamers, fluorine compounds, and other components may be added to the glass composition for the purpose of clarifying, coloring, decoloring, fine-tuning of optical constants, etc. Furthermore, other components may be added in addition to the above components, as long as the effects of the optical glass according to this embodiment can be obtained.

[0038] It is preferable to use high-purity raw materials with low impurity content. A high-purity product is one that contains 99.85 mass% or more of the component in question. The use of high-purity raw materials reduces the amount of impurities, which tends to increase the internal transmittance of the optical glass.

[0039] Next, the physical properties of the optical glass of this embodiment will be described.

[0040] The optical glass according to this embodiment preferably has a high internal transmittance. In light of this situation, the wavelength (λ ) at which the internal transmittance per 10 mm of the optical glass according to this embodiment is 5% is ５ ) is 352 nm or less. ５ The lower limit of the wavelength (λ) is, for example, 259 nm. ５ The upper limit of the thickness of the optical fiber 100 is preferably 310 nm, more preferably 300 nm, and even more preferably 285 nm.

[0041] From the viewpoint of thinning the lens, the optical glass according to this embodiment has a high refractive index (refractive index (n ｄ However, in general, the refractive index (n ｄ In view of this situation, the refractive index (n ｄ The refractive index (n ｄ The lower limit of the refractive index (n ｄ The upper limit of the ratio (R) is preferably 1.87, more preferably 1.85, and even more preferably 1.84.

[0042] The Abbe number (ν ｄ ) is 28 or more and 47 or less. ｄ The lower limit of the Abbe number (ν ｄ The upper limit of the molecular weight is preferably 37, more preferably 36, and even more preferably 35.

[0043] The optical glass according to this embodiment has a refractive index (n ｄ ) and Abbe number (ν ｄ ) is a refractive index (n ｄ ) is in the range of 1.80 to 1.87, and the Abbe number (ν ｄ) is in the range of 33 to 37. The optical glass according to this embodiment, which has such properties, can be combined with other optical glasses, for example, to design an optical system in which chromatic aberration and other aberrations are well corrected.

[0044] From the viewpoint of correcting aberrations in the lens, the optical glass according to this embodiment has a small partial dispersion ratio (P ｇ , Ｆ In view of this situation, it is desirable that the optical glass according to this embodiment has a partial dispersion ratio (P ｇ , Ｆ ) is expressed by the following formula (1): P ｇ,Ｆ <-0.00204 × ν ｄ +0.657 (1) It is preferable to satisfy the following formula (2): −0.00204×ν ｄ +0.640<P ｇ,Ｆ <-0.00204 × ν ｄ It is more preferable that the following expression is satisfied: +0.657 (2).

[0045] From the viewpoint of ultraviolet or visible light transmittance of the optical system, the wavelength (λ ) at which the internal transmittance per 10 mm of the optical glass according to this embodiment is 5%. ５ ) is expressed by the following formula (3): λ ５ <-5.625 × ν ｄ +542 (3) It is preferable to satisfy the following formula (4): −5.625×ν ｄ +535<λ ５ <-5.625 × ν ｄ It is more preferable that the following expression is satisfied: +542 (4).

[0046] ΔT can be used as an index of devitrification resistance stability. Generally, a high ΔT means that the glass has high devitrification resistance stability. In this embodiment, the glass transition temperature (T ｇ ) and crystallization initiation temperature (T ｘ ) can be measured by differential thermal analysis. In light of this situation, the optical glass according to this embodiment has a glass transition temperature (T ｇ ) and crystallization initiation temperature (T ｘ ) temperature difference (ΔT = T ｘ -Tｇ ) is 73°C or higher and 259°C or lower. The lower limit of the difference is preferably 150°C, more preferably 180°C, and even more preferably 200°C. The upper limit of the difference is preferably 250°C, more preferably 230°C, and even more preferably 220°C.

[0047] The optical glass according to this embodiment has a diameter (D) of 10 mm or more. The lower limit of the diameter (D) is preferably 11.0 mm, more preferably 12.5 mm, and even more preferably 13.5 mm. The upper limit of the diameter (D) is, for example, 14.3 mm. The term "diameter" as used herein refers to the maximum value in the diameter direction of the glass gob, and in the case of a substantially spherical glass gob, refers to the diameter value.

[0048] The optical glass according to this embodiment has a thickness (T) of 5.03 mm or more. The lower limit of the thickness (T) is preferably 5.20 mm, more preferably 5.40 mm, and even more preferably 5.50 mm. The upper limit of the thickness (T) is, for example, 5.94 mm. The term "thickness" as used herein refers to the height in the direction perpendicular to the maximum diameter (diameter (D)) of the glass gob, and in the case of a substantially spherical glass gob, refers to the diameter value.

[0049] The optical glass according to this embodiment has a weight of 1700 mg or more. The lower limit of the weight is preferably 1900 mg, more preferably 2000 mg, and even more preferably 2200 mg. The upper limit of the weight is, for example, 3600 mg.

[0050] The specific gravity (S ｇ ) is 4.2 or more and 5.8 or less. ｇ The lower limit of the specific gravity (S) is preferably 4.3, more preferably 4.6, and even more preferably 4.7. ｇ The upper limit of the saturation temperature is preferably 5.6, more preferably 5.4, and even more preferably 5.3.

[0051] Next, applications of the optical glass of this embodiment will be described.

[0052] From the above perspective, the optical glass according to this embodiment can be suitably used, for example, as an optical element provided in an optical instrument. Examples of such optical elements include mirrors, lenses, prisms, filters, and the like. Examples of optical systems that use the optical elements include objective lenses, condenser lenses, imaging lenses, and interchangeable lenses for cameras. These optical systems can be suitably used in various optical devices, such as imaging devices, such as interchangeable-lens cameras and non-interchangeable-lens cameras, and microscopes, such as fluorescence microscopes and multiphoton microscopes. Such optical devices are not limited to the imaging devices and microscopes described above, but also include, but are not limited to, telescopes, binoculars, laser rangefinders, projectors, defect inspection devices, and the like. Examples of these optical devices are described below.

[0053] <Imaging Device> FIG. 1 is a perspective view showing an example of an imaging device using the optical device according to this embodiment. The imaging device 1 is a so-called digital single-lens reflex camera (interchangeable lens camera), and the taking lens 103 (optical system) includes an optical element whose base material is the optical glass according to this embodiment. A lens barrel 102 is detachably attached to a lens mount (not shown) of a camera body 101. Light passing through the lens 103 of the lens barrel 102 forms an image on a sensor chip (solid-state image sensor) 104 of a multi-chip module 106 disposed on the rear side of the camera body 101. This sensor chip 104 is a bare chip such as a so-called CMOS image sensor, and the multi-chip module 106 is, for example, a COG (chip-on-glass) type module in which the sensor chip 104 is bare-chip mounted on a glass substrate 105.

[0054] 2 and 3 are schematic diagrams showing another example in which the optical device according to the present embodiment is used as an imaging device. Fig. 2 shows a front view of the imaging device CAM, and Fig. 3 shows a rear view of the imaging device CAM. The imaging device CAM is a so-called digital still camera (a camera with a non-interchangeable lens), and the taking lens WL (optical system) includes an optical element whose base material is the optical glass according to the present embodiment.

[0055] When the power button (not shown) of the imaging device CAM is pressed, the shutter (not shown) of the taking lens WL is opened, light from the subject (object) is collected by the taking lens WL, and an image is formed on the imaging element located on the image plane. The subject image formed on the imaging element is displayed on the liquid crystal monitor M located behind the imaging device CAM. After the photographer decides the composition of the subject image while looking at the liquid crystal monitor M, he or she presses the release button B1 to capture the subject image with the imaging element, which is then recorded and saved in memory (not shown).

[0056] The image pickup device CAM is provided with an auxiliary light emitting unit EF that emits auxiliary light when the subject is dark, a function button B2 that is used to set various conditions for the image pickup device CAM, and the like.

[0057] Optical systems used in such digital cameras and the like are required to have higher resolution, lower chromatic aberration, and smaller size. To achieve these, it is effective to use glasses with different dispersion characteristics in the optical system. In particular, glasses with medium or high dispersion but low partial dispersion ratios (P ｇ , Ｆ ) is in high demand. From this perspective, the optical glass according to this embodiment is suitable as a component of such optical equipment. Note that optical equipment to which this embodiment can be applied is not limited to the imaging device described above, but also includes, for example, projectors. The optical element is also not limited to a lens, but also includes, for example, a prism.

[0058] <Microscope> Figure 4 is a block diagram showing an example of the configuration of a multiphoton microscope 2 according to this embodiment. The multiphoton microscope 2 includes an objective lens 206, a condenser lens 208, and an imaging lens 210. At least one of the objective lens 206, the condenser lens 208, and the imaging lens 210 includes an optical element whose base material is the optical glass according to this embodiment. The following description will focus on the optical system of the multiphoton microscope 2.

[0059] The pulsed laser device 201 emits ultrashort pulsed light, for example, with a near-infrared wavelength (approximately 1000 nm) and a pulse width in femtosecond units (e.g., 100 femtoseconds). The ultrashort pulsed light immediately after being emitted from the pulsed laser device 201 is generally linearly polarized in a predetermined direction.

[0060] The pulse splitting device 202 splits the ultrashort pulsed light, increases the repetition frequency of the ultrashort pulsed light, and emits it.

[0061] The beam adjusting unit 203 has functions such as a function to adjust the beam diameter of the ultrashort pulsed light incident from the pulse splitting device 202 to match the pupil diameter of the objective lens 206, a function to adjust the focusing and divergence angles of the ultrashort pulsed light in order to correct axial chromatic aberration (focus difference) between the wavelength of the light emitted from the sample S and the wavelength of the ultrashort pulsed light, and a pre-chirp function (group velocity dispersion compensation function) to impart reverse group velocity dispersion to the ultrashort pulsed light in order to correct the pulse width of the ultrashort pulsed light being widened by group velocity dispersion while passing through the optical system.

[0062] The repetition frequency of the ultrashort pulsed light emitted from the pulsed laser device 201 is increased by the pulse dividing device 202, and the above-mentioned adjustment is performed by the beam adjusting unit 203. The ultrashort pulsed light emitted from the beam adjusting unit 203 is then reflected by the dichroic mirror 204 in the direction of the dichroic mirror, passes through the dichroic mirror 205, and is collected by the objective lens 206 to be irradiated onto the sample S. At this time, the ultrashort pulsed light may be scanned over the observation surface of the sample S by using a scanning means (not shown).

[0063] For example, when observing the fluorescence of a sample S, the fluorescent dye with which the sample S is stained undergoes multiphoton excitation in the area of ​​the sample S irradiated with the ultrashort pulsed light and in its vicinity, emitting fluorescence (hereinafter referred to as "observation light") having a wavelength shorter than that of the ultrashort pulsed light, which is an infrared wavelength.

[0064] Observation light emitted from the sample S in the direction of the objective lens 206 is collimated by the objective lens 206 and is reflected by or transmitted through the dichroic mirror 205 depending on its wavelength.

[0065] The observation light reflected by the dichroic mirror 205 enters the fluorescence detection unit 207. The fluorescence detection unit 207 is composed of, for example, a barrier filter, a PMT (photomultiplier tube), etc., receives the observation light reflected by the dichroic mirror 205, and outputs an electrical signal corresponding to the amount of light. Furthermore, the fluorescence detection unit 207 detects the observation light across the observation surface of the sample S as the ultrashort pulsed light scans the observation surface of the sample S.

[0066] It is also possible to remove the dichroic mirror 205 from the optical path so that all of the observation light emitted from the sample S in the direction of the objective lens 206 is detected by the fluorescence detection unit 211. In this case, the observation light is descanned by a scanning means (not shown), transmitted through the dichroic mirror 204, collected by the collecting lens 208, passed through a pinhole 209 provided at a position approximately conjugate with the focal position of the objective lens 206, transmitted through an imaging lens 210, and incident on the fluorescence detection unit 211.

[0067] The fluorescence detection unit 211 is configured with, for example, a barrier filter, a PMT, etc., receives the observation light imaged on the light receiving surface of the fluorescence detection unit 211 by the imaging lens 210, and outputs an electrical signal according to the amount of light. Furthermore, the fluorescence detection unit 211 detects the observation light across the observation surface of the sample S as the ultrashort pulsed light scans the observation surface of the sample S.

[0068] It is also possible to remove the dichroic mirror 205 from the optical path so that all of the observation light emitted from the sample S in the direction of the objective lens 206 is detected by the fluorescence detection unit 211 .

[0069] Furthermore, observation light emitted from the sample S in the direction opposite to the objective lens 206 is reflected by the dichroic mirror 212 and enters the fluorescence detection unit 213. The fluorescence detection unit 213 is composed of, for example, a barrier filter, a PMT, etc., and receives the observation light reflected by the dichroic mirror 212 and outputs an electrical signal according to the amount of light. Furthermore, the fluorescence detection unit 213 detects the observation light across the observation surface of the sample S as the ultrashort pulsed light scans the observation surface of the sample S.

[0070] The electrical signals output from the fluorescence detection units 207, 211, and 213 are input, for example, to a computer (not shown), which can generate an observation image based on the input electrical signals, display the generated observation image, and store the data of the observation image.

[0071] <Cemented Lens> Fig. 5 is a schematic diagram showing an example of a cemented lens according to this embodiment. The cemented lens 3 is a compound lens having a first lens element 301 and a second lens element 302. At least one of the first lens element and the second lens element uses the optical glass according to this embodiment. The first lens element and the second lens element are cemented together via a cementing member 303. A known adhesive or the like can be used as the cementing member 303. Note that the term "lens element" refers to each of the lenses that make up a single lens or a cemented lens.

[0072] The cemented lens according to this embodiment is useful from the viewpoint of correcting chromatic aberration, and can be suitably used in the optical elements, optical systems, optical devices, and the like described above. Furthermore, optical systems including cemented lenses can be particularly suitably used in interchangeable lenses for cameras, optical devices, and the like. While the above-described embodiment has been described as a cemented lens using two lens elements, this is not limiting, and a cemented lens using three or more lens elements may also be used. When a cemented lens using three or more lens elements is used, it is sufficient that at least one of the three or more lens elements is formed using the optical glass according to this embodiment.

[0073] Next, a method for manufacturing the optical glass of this embodiment will be described.

[0074] The optical glass according to this embodiment can be manufactured using, for example, a levitation furnace. Levitation furnaces include electrostatic, electromagnetic, sonic, magnetic, and gas jet types, and are not particularly limited. However, it is preferable to use a gas jet type levitation furnace for levitation melting of oxides. Below, a manufacturing method using a gas jet type levitation furnace will be described as an example.

[0075] FIG. 6 is a schematic diagram showing the overall configuration of a gas jet levitation furnace, and FIG. 7 is an enlarged schematic diagram of a pedestal on a stage of the gas jet levitation furnace.

[0076] In the gas jet type levitation furnace 4, the raw material U is placed on a pedestal 402 on a stage 401. Then, laser light L emitted from a laser light source 403 is irradiated onto the raw material U via mirrors 404 and 405. The temperature of the raw material U heated by the irradiation of the laser light L is monitored by a radiation thermometer 406. Based on the temperature information of the raw material U monitored by the radiation thermometer 406, the output of the laser light source 403 is controlled by a computer 407. In addition, the state of the raw material U is imaged by a CCD camera 408, and the image is output to a monitor 409 (see FIG. 6 ). Note that, for example, a carbon dioxide laser, a semiconductor laser, a fiber laser, a YAG laser, etc. can be used as the laser light source.

[0077] In the gas jet levitation furnace 4, the raw material U is levitated by the gas sent to the pedestal (see FIG. 7). The flow rate of the gas sent to the pedestal is controlled by a gas flow regulator 410. For example, gas can be sprayed from a nozzle with a conical hole, and the raw material U can be levitated while being heated non-contact with a laser beam L. When the raw material U melts, it takes on a spherical or ellipsoidal shape due to its own surface tension and levitates in that state.

[0078] Thereafter, when the laser light L is shut off, the raw material U in a molten state is cooled, and transparent glass is obtained. The type of gas is not particularly limited, and known gases can be used as appropriate, such as oxygen, nitrogen, carbon dioxide, argon, and air. The nozzle shape and heating method are also not particularly limited, and known methods can be used as appropriate. External pressure may be applied to the raw material U in a molten state to form it into a desired thickness and size. The optical glass obtained in this manner can be processed into a desired shape as needed, and polished or otherwise processed to form a desired optical element.

[0079] Conventionally, when optical glass is manufactured using a container such as a crucible, SiO ２ , B ２ O ３ , P２ O ５ , GeO ２ It has been necessary to enhance glass-forming ability by including a large amount of a network-forming oxide such as ZnO. Therefore, when a glass composition containing a large amount of a material that is not a network-forming oxide and a small amount of the above-mentioned network-forming oxide is used, crystallization (heterogeneous nucleation) originating from the container-melt interface occurs, often making vitrification impossible. Furthermore, glass gobs are sometimes used as materials for optical lenses in various optical instruments, and it is desirable to be able to stably produce large glass gobs.

[0080] In this regard, in this embodiment, for example, when optical glass is produced by the method using the levitation furnace described above, there is no contact between the container and the melt, so heterogeneous nucleation can be minimized. As a result, glass formation from the melt is greatly promoted, making it possible to vitrify compositions that contain little or no network-forming oxides, which are impossible to produce by crucible melting. By adopting this production method, optical glass of the composition according to this embodiment, which could not be vitrified in the past, can be produced. Furthermore, large glass gobs such as those described above can also be produced. In addition, the optical glass according to this embodiment has a high refractive index and high ultraviolet transmittance. Because the optical glass according to this embodiment has many advantages, it can be used as a high-refractive-index glass material or a broadband-transmitting material.

[0081] Next, examples of the present invention will be described, but the present invention is not limited to these examples.

[0082] <Preparation of Optical Glass> The optical glass according to each example was prepared using a gas-jet levitation furnace 4 shown in FIGS. 6 and 7 according to the following procedure. First, glass raw materials selected from oxides were weighed to obtain the composition (mol %) listed in each table. The glass raw materials may also be selected from hydroxides, carbonates, nitrates, and sulfates. Next, the weighed raw materials were mixed in an alumina mortar. These raw materials were uniaxially pressed at 20 MPa to form cylindrical pellets. The resulting pellets were fired in an electric furnace at 1000 to 1300°C in air for 6 to 12 hours to produce sintered bodies. The resulting sintered bodies were roughly crushed, and 50 to 3500 mg of each were placed in a pedestal nozzle. The raw materials were then melted by irradiating them from above with a carbon dioxide laser while injecting air gas. The melted raw materials formed a spherical or ellipsoidal shape due to their own surface tension and were suspended in a levitation state due to the gas pressure. When the raw materials were completely melted, the laser output was shut off to cool the raw materials and obtain gobs (glass spheres). For the glasses of each example, no visible volatilization was observed during melting, and no bubbles or devitrification were observed.

[0083] <Evaluation of Physical Properties> FIGS. 8 and 10 are graphs plotting the optical constants of each example, and FIG. 9 is a graph plotting the optical constants of each example.

[0084] Crystallization initiation temperature (T ｘ ), glass transition temperature (T ｇ ), and the temperature difference (ΔT) is measured. ｘ ) and glass transition temperature (T ｇ ) were measured by differential thermal analysis during the temperature rise process (temperature rise rate: 10°C / min), and T ｘ -T ｇ was defined as the temperature difference (ΔT).

[0085] Diameter (D) and Thickness (T) The diameter (D) and thickness (T) of each sample were measured with an electronic caliper.

[0086] Specific gravity (S ｇ ) Specific gravity of each sample (S ｇ The specific gravity was measured using a dry density meter (Shimadzu Corporation; "Accupyk II 1340"). The specific gravity value was rounded to three decimal places.

[0087] Refractive index (nｄ ) and Abbe number (ν ｄ The sample was processed into a 90-degree prism, and the refractive index was measured by the V-block method using a refractive index measuring instrument (KPR-3000 manufactured by Kalnew Optical Co., Ltd.), and the Abbe number, partial dispersion ratio, and anomalous dispersion were calculated.

[0088] In the prism coupling method, a glass sample was polished, the polished surface was attached to a single crystal rutile prism, and the angle of total reflection was measured when light of the measurement wavelength was incident to determine the refractive index. Five measurements were taken at each of three wavelengths: 473 nm, 594.1 nm, and 656 nm, and the average value was used as the measured value. Furthermore, the obtained measured values ​​were fitted using the least squares method using the following Drude-Voigt dispersion equation, and the refractive indexes at the d-line (587.562 nm), F-line (486.133 nm), and C-line (656.273 nm), as well as the Abbe number (ν ｄ ) was calculated.

[0089]

[0090] (n: refractive index, m: electron mass, c: speed of light, e: elementary charge, N: number of molecules per unit volume, f: oscillator strength, λ ０ : characteristic resonance wavelength, λ: wavelength)

[0091] n ｄ indicates the refractive index of glass for light of 587.562 nm. ｄ ) was calculated using the following formula (5): Ｃ , n Ｆ indicate the refractive index of the glass for light with wavelengths of 656.273 nm and 486.133 nm, respectively. ｄ = (n ｄ −1) / (n Ｆ -n Ｃ ) (5) The refractive index value was rounded to six decimal places.

[0092] Partial dispersion ratio (P ｇ , Ｆ ) The partial variance ratio (P ｇ , Ｆ ) is the primary variance (n Ｆ -n Ｃ ) partial variance (n ｇ -n Ｆ) and was calculated using the following formula (6): ｇ indicates the refractive index of the glass for light with a wavelength of 435.835 nm. ｇ , Ｆ The values ​​of P are rounded to six decimal places. ｇ , Ｆ = (n ｇ -n Ｆ ) / (n Ｆ -n Ｃ ) ... (6)

[0093] Internal transmittance The internal transmittance of each sample was measured using a spectrophotometer (Hitachi High-Tech Science Corporation; "Ultraviolet-Visible-Infrared Spectrophotometer UH4150") to measure the transmittance of a 4-9 mm thick parallel-polished product at wavelengths of 200 to 700 nm, and then the refractive index measurement data was used to remove and correct the contribution to the transmittance due to the reflectance at each wavelength, and the value was converted to the transmittance for a 10 mm thickness. Fitting was performed using the following dispersion curve equation by the least squares method from the refractive index data obtained by the V-block method for 10 emission lines of h, g, F', F, e, d, C', C, r, and t rays.

[0094]

[0095] The refractive index value n at each wavelength λ calculated using the dispersion curve equation λ The transmittance T is calculated by taking into account the surface reflectance R of each wavelength and the multiple reflections of the incident light on the front and back surfaces, assuming that there is no internal light absorption. ｔｈ The external transmittance measured value T at a thickness of t mm was calculated using the following formula. eｘｐ and T ｔｈ Using the internal transmittance T (ｔｍｍ) was calculated.

[0096]

[0097] The internal transmittance T at the thickness t mm calculated above (ｔmm) Using this, the transmittance value T (10mm) was calculated using the following formula:

[0098]

[0099] The transmittance value T of the 10 mm thickness calculated above （１０ｍｍ） The wavelength (λ) at which the internal transmittance per 10 mm of the optical glass becomes 5% is determined using ５ ) was sought.

[0100] The compositions and physical properties of the examples are shown in the tables below. Unless otherwise specified, the content of each component is expressed in mole percent.

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108] From the above, it was found that the optical glasses of the examples had high transmittance in the medium dispersion, high refractive index region, and that large glass gobs could be stably produced.

[0109] 1...imaging device, 101...camera body, 102...lens barrel, 103...lens, 104...sensor chip, 105...glass substrate, 106...multi-chip module, CAM...imaging device (non-interchangeable lens camera), WL...taking lens, M...liquid crystal monitor, EF...fill-in light emitting unit, B1...release button, B2...function button, 2...multiphoton microscope, 201...pulse laser device, 202...pulse splitting device, 203...beam adjustment unit, 204, 205, 212...dichroic mirror, 206... Objective lens, 207, 211, 213... fluorescence detection unit, 208... condenser lens, 209... pinhole, 210... imaging lens, S... sample, 3... cemented lens, 301... first lens element, 302... second lens element, 303... cemented member, 4... gas levitation furnace, 401... stage, 402... base, 403... laser light source, 404, 405... mirror, 406... radiation thermometer, 407... computer, 408... CCD camera, 409... monitor, 410... gas flow regulator, L... laser light, U... raw material

Claims

1. In mole percent, SiO ２ Content rate: 15% or more and 55% or less, Al ２ O ３ Content rate: 7% or more and 42% or less, TiO ２ and Nb ２ O ５ The total content of TiO ２ +Nb ２ O ５ ): 0% or more and 21% or less, La ２ O ３ , Y ２ O ３ , ZrO ２ and Ta ２ O ５ Total content (La ２ O ３ +Y ２ O ３ + ZrO ２ +Ta ２ O ５ ): 15% or more and 55% or less, Al ２ O ３ , TiO ２ , ZrO ２ , Nb ２ O ５ and Ta ２ O ５ Total content of Al ２ O ３ + TiO ２ + ZrO ２ +Nb ２ O ５ +Ta ２ O ５ ): 32% or more and 65% or less.

2. In mole percent, La ２ O ３ Content rate: 0% or more and 33% or less, Y ２ O ３ Content rate: 0% or more and 10% or less, ZrO ２ Content rate: 0% or more and 23% or less, Ta ２ O ５ 2. The optical glass according to claim 1, wherein the content is 0% or more and 25% or less.

3. The optical glass according to claim 1 or 2, wherein the BaO content, expressed in mol %, is 0% or more and 25% or less.

4. In mole percent, B ２ O ３ The optical glass according to any one of claims 1 to 3, wherein the content is 0% or more and 5% or less.

5. In mole percent, Nb ２ O ５ Content rate: 0% or more and 21% or less, TiO ２ The optical glass according to any one of claims 1 to 4, wherein the content is 0% or more and 5% or less.

6. In mole percent, SiO ２ and Al ２ O ３ Total content (SiO ２ +Al ２ O ３ 6. The optical glass according to claim 1, wherein the refractive index is 42% or more and 75% or less.

7. The wavelength (λ) at which the internal transmittance per 10 mm is 5% ５ 7. The optical glass according to claim 1, wherein the optical transmittance is 352 nm or less.

8. Refractive index for d line (n ｄ 8. The optical glass according to claim 1, wherein the refractive index is 1.75 or greater and 1.97 or less.

9. Abbe number (ν ｄ 9. The optical glass according to claim 1 , wherein n is 28 or more and 47 or less.

10. The partial dispersion ratio (P ｇ，Ｆ ) is represented by the formula (1) P ｇ,Ｆ <-0.00204 × ν ｄ 10. The optical glass according to claim 1, which satisfies the following expression: +0.657 (1).

11. The wavelength (λ) at which the internal transmittance per 10 mm of the optical glass is 5% ５ ) is expressed by the formula (3) λ ５ <-5.625 × ν ｄ The optical glass according to any one of claims 1 to 10, which satisfies the following expression: +542 (3).

12. Specific gravity (S ｇ 12. The optical glass according to claim 1, wherein the refractive index is 4.2 or more and 5.8 or less.

13. The glass transition temperature (T ｇ ) and crystallization initiation temperature (T ｘ ) temperature difference (ΔT = T ｘ -T ｇ 13. The optical glass according to claim 1, wherein the temperature of melting is 73° C. or higher and 259° C. or lower.

14. The optical glass according to any one of claims 1 to 13, wherein the diameter (D) of the optical glass is 10 mm or more.

15. An optical element using the optical glass according to any one of claims 1 to 14.

16. An optical system comprising the optical element according to claim 15.

17. An objective lens for a microscope, comprising the optical system according to claim 16.

18. An interchangeable lens for a camera, comprising the optical system according to claim 16.

19. An optical device comprising the optical system of claim 16.

20. A cemented lens comprising a first lens element and a second lens element, at least one of the first lens element and the second lens element being made of the optical glass according to any one of claims 1 to 14.

21. An optical system comprising the cemented lens according to claim 20.

22. An objective lens for a microscope comprising the optical system of claim 21.

23. An interchangeable lens for a camera, comprising the optical system according to claim 21.

24. An optical device comprising the optical system of claim 21.

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