Optical glass, optical element, optical system, interchangeable lens, and optical apparatus

Abstract

To provide an optical glass having a high refractive index, low dispersibility and devitrification resistance at a high level and capable of stably producing a large-sized glass gob.SOLUTION: A Si4 + content of 5% or more and 20% or less, a B3 + content of 0% or more and 5% or less, a Al3 + content of 18% or more and 35% or less, a total content of La3 +, Y3 +, and Gd3 + of 15% or more and 50% or less, a Zr4 + content of 2% or more and 15% or less, a Ta5 + content of 8% or more and 30% or less, and a Gd3 + content of 0% or more and 10% or less, in terms of mol% of cations.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to optical glass, optical elements, optical systems, interchangeable lenses, and optical devices. This invention claims priority from Japanese Patent Application No. 2019-106096, filed on June 6, 2019, and the contents of that application are incorporated by reference into this application in designated states where incorporation by reference of documents is permitted. [Background technology]

[0002] Optical glass is used in a variety of optical elements and optical devices, and for example, Patent Document 1 discloses halide glass for use in the ultraviolet to infrared region. In order to increase the degree of freedom in designing the optical systems used in optical devices, there is a demand for the development of optical glass with a high refractive index. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 07-081973 Summary of the Invention

[0004] The first aspect of the present invention is a compound having, in mole percent of cations, Si 4+ The content of Al is 5-20%. 3+ The content of La is 18-35%. 3+ , Y 3+ and Gd 3+ The total content of Zr is 15-50%. 4+ The content of Ta is 2 to 15%. 4+ The content of is 8 to 30%, and Si 4+ and Al 3+ Al content in relation to the total content 3+ Ratio of content of (Al 3+ / (Si 4+ +Al 3+ )) is 0.5 to 0.85.

[0005] A second aspect of the present invention is an optical element made of the above-mentioned optical glass.

[0006] A third aspect of the present invention is an optical system using the optical element described above.

[0007] A fourth aspect of the present invention is an interchangeable lens comprising the optical system described above.

[0008] A fifth aspect of the present invention is an optical device comprising the optical system described above. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a multiphoton microscope equipped with an optical element using optical glass according to this embodiment. [Figure 2] FIG. 2 is a perspective view of an imaging device equipped with an optical element using the optical glass according to this embodiment. [Figure 3] FIG. 3 is a front view of another example of an imaging device equipped with an optical element using the optical glass according to this embodiment. [Figure 4] FIG. 4 is a rear view of the imaging device of FIG. [Figure 5] FIG. 5 is a schematic diagram of the overall configuration of a gas jet type levitation furnace. [Figure 6] Figure 6 is an enlarged schematic diagram of the pedestal on the stage of the gas jet levitation furnace. [Figure 7] FIG. 7 is a graph plotting the optical constants of each example and each comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described. The present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content.

[0011] <Optical glass> The optical glass according to this embodiment contains, in terms of cation molar percentage, Si4+ The composition is 5-20% Al 3+ The components are 18-35%, La 3+ , Y 3+ and Gd 3+ The total amount of components is 15-50%, Zr 4+ The components are 2-15%, Ta 4+ The composition is 8 to 30%, and Al 3+ / (Si 4+ +Al 3+ ) is 0.5 to 0.85. In this specification, unless otherwise specified, the content of each component is expressed in mole percent of the cation. The form of each cation is not particularly limited, but it may be contained in the optical glass in the form of, for example, an oxide.

[0012] The optical glass according to this embodiment is a novel optical glass that can be vitrified even with a low content of cations that constitute network-forming oxides such as SiO2 and B2O3. The optical glass according to this embodiment can combine a high refractive index, low dispersion (wavelength dependence of refractive index), and high resistance to devitrification. Furthermore, the composition according to this embodiment allows for the stable production of large glass gobs.

[0013] First, each component of the optical glass according to this embodiment will be described.

[0014] Si 4+ The component is included as SiO2 in the oxide equivalent composition, and is a component that constitutes a network-forming oxide. 4+ The component is a component that can enhance high meltability and devitrification resistance. If the content is less than 5%, the glass is prone to devitrification, and if it exceeds 20%, sufficient meltability cannot be obtained. From this perspective, the content is 5 to 20%. From the perspective of further improving these effects, the lower limit of the content is preferably 6%, more preferably 7%, and the upper limit of the content is preferably 15%, more preferably 10%.

[0015] Al 3+The component is, for example, a component contained as Al2O3 in the oxide-equivalent composition. 3+ is a component that can improve the component stability during the production of optical glass and the devitrification resistance of optical glass. If this content is less than 18%, the glass will be more susceptible to devitrification, and if it exceeds 35%, the component stability during the production of optical glass will decrease, making manufacturing defects more likely to occur. From these perspectives, this content is 18 to 35%. From the perspective of further improving these effects, the lower limit of this content is preferably 19%, more preferably 20%, and the upper limit of this content is preferably 30%, more preferably 25%.

[0016] La, a rare earth element 3+ , Y 3+ , Gd 3+ are components that can increase the refractive index without impairing low dispersion, and are included as La2O3, Y2O3, and Gd2O3, respectively, in oxide-equivalent compositions. 3+ , Y 3+ , and Gd 3+ The total amount (La 3+ +Y 3+ +Gd 3+ If the total amount of La is too small, the above-mentioned effects are insufficient, and if the total amount of La exceeds 50%, the glass is prone to devitrification. 3+ +Y 3+ +Gd 3+ is 15 to 50%. From the viewpoint of further improving these effects, the lower limit of the total amount thereof is preferably 25%, more preferably 35%, and the upper limit of the total amount thereof is preferably 45%, more preferably 40%.

[0017] La 3+ is a component that is contained as La2O3 in terms of oxide composition. 3+ has the effect of increasing the refractive index without impairing low dispersion, and can also maintain the devitrification resistance of the glass. From these viewpoints, the content of this element is preferably 0 to 50%. The upper limit is more preferably 47%, and even more preferably 45%.

[0018] Y 3+ is a component contained as Y2O3 in the oxide equivalent composition. 3+ is a component that can increase the refractive index without impairing low dispersion, and La 3+ By having La coexist in the glass, it is possible to further improve devitrification resistance. From this viewpoint, the content is preferably 0 to 50%. The upper limit is more preferably 10%, and even more preferably 5%. 3+ and Y 3+ It is preferable to contain both of these.

[0019] Gd 3+ is a component contained as Gd2O3 in terms of oxide composition. 3+ is a component that can increase the refractive index without impairing low dispersion, and La 3+ By having La coexist in the glass, it is possible to further improve devitrification resistance. From this viewpoint, the content is preferably 0 to 50%. The upper limit is more preferably 10%, and even more preferably 5%. 3+ and Gd 3+ It is preferable to contain both of these.

[0020] Zr 4+ is a component contained as ZrO2 in the oxide equivalent composition. 4+ has the effect of improving resistance to devitrification while maintaining low dispersibility. If the content is less than 2%, dispersibility will be high, and if it exceeds 15%, the glass will be more susceptible to devitrification. From this perspective, the content is 2 to 15%. From the perspective of further improving these effects, the lower limit of the content is preferably 5%, more preferably 8%, and the upper limit of the content is preferably 13%, more preferably 12%.

[0021] Ta 5+ is a component that is contained as Ta2O5 in the oxide equivalent composition. 5+has the effect of improving resistance to devitrification while maintaining low dispersibility. If the content is less than 8%, dispersibility becomes high, and if it exceeds 30%, the glass becomes more susceptible to devitrification. From this perspective, the content is 8 to 30%. From the perspective of further improving these effects, the lower limit of the content is preferably 9%, more preferably 10%, and the upper limit of the content is preferably 20%, more preferably 15%.

[0022] The optical glass according to this embodiment is Al 3+ / (Si 4+ +Al 3+ ) satisfies the relationship of 0.5 to 0.85. By blending so as to satisfy this relationship, it is possible to achieve both high levels of meltability and devitrification resistance. From the viewpoint of further improving these effects, Al 3+ / (Si 4+ +Al 3+ The lower limit of ) is preferably 0.6, more preferably 0.7, and the upper limit is preferably 0.8, more preferably 0.75.

[0023] The optical glass according to this embodiment further contains an alkaline earth metal, Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ It is preferable that the alkaline earth metal oxide R contains at least one component selected from the group consisting of: 2+ (R represents one or more of Mg, Ca, Sr, and Ba) is, for example, a component contained as RO in the oxide-equivalent composition. These may be used alone or in combination of two or more. By further containing such a component, the meltability of the glass can be further improved.

[0024] In order to further improve the above-mentioned effects, Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ The total amount of the components is preferably 0 to 15%, and the upper limit of this total amount is more preferably 10%, and even more preferably 5%.

[0025] Ti 4+ is a component that is contained as TiO2 in the oxide equivalent composition. 4+ can further improve low dispersion. From the viewpoint of such effects and the contents of rare earth elements and transition metal elements, this content is preferably 0 to 10%. The upper limit of this content is more preferably 7%, and even more preferably 4%.

[0026] Nb 5+ is a component contained as Nb2O5 in the oxide equivalent composition. 5+ can further improve the low dispersion of the glass. From the viewpoint of further improving this effect, the content is preferably 0 to 30%. The lower limit of the content is more preferably 3%, and even more preferably 5%, and the upper limit of the content is more preferably 20%, and even more preferably 10%.

[0027] B 3+ is included as B2O3 in the oxide equivalent composition, and is a component that constitutes the network-forming oxide. 5+ is included as P2O5 in the oxide equivalent composition, and is a component that constitutes a network-forming oxide. It can easily improve the glass-forming ability. On the other hand, B 3+ YaP 5+ 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, making striae more apparent. 3+ YaP 5+ Vitrification is possible even with a reduced content or even without the inclusion of any of these elements, and excellent physical properties can be imparted.

[0028] From the above perspective, B 3+ The content of B is preferably 0 to 5%, more preferably 0 to 3%, and even more preferably 0%. 3+It is preferable that the component is substantially not contained. In this specification, the term "substantially not contained" means that the component is not actively added, and does not exclude the component being unavoidably contained.

[0029] In addition, from the above perspective, P 5+ The content of P is preferably 0 to 5%, more preferably 0 to 3%, and even more preferably 0%. 5+ It is preferable that the compound is substantially free of

[0030] Alkali metal M + (Li + , Na + , K. + , Cs + ) are included as MO in terms of oxide composition, for example, and are components that constitute network-forming oxides. On the other hand, these alkali metals M are highly volatile components, and if they are introduced in excess, this can lead to fluctuations in the composition of the glass during production, and can make striae more apparent. The optical glass according to this embodiment does not contain these alkali metals M + Vitrification is possible even with a reduced content or even without the inclusion of any of these elements, and excellent physical properties can be imparted.

[0031] From the above perspective, Li + , Na + , K. + , Cs + The total content of Li is preferably 0 to 5%, more preferably 0 to 3%, and even more preferably 0%. + , Na + , K. + and Cs + It is preferable that the compound is substantially free of

[0032] The optical glass according to this embodiment may further contain other optional components as long as they do not interfere with the achievement of the object.

[0033] Next, the physical properties of the optical glass according to this embodiment will be described.

[0034] The optical glass according to this embodiment has a crystallization peak temperature (T p ) and glass transition temperature (T g ) difference (ΔT=T p -T g ) is preferably 130°C or higher, more preferably 160°C or higher, even more preferably 170°C or higher, and even more preferably 180°C or higher. ΔT can be used as an index of devitrification resistance. Generally, a high ΔT means that the glass has high devitrification resistance. In this embodiment, the crystallization peak temperature (T p ) and glass transition temperature (T g ) can be measured by differential thermal analysis.

[0035] The optical glass according to this embodiment can be suitably used for the high refractive index region. From this viewpoint, the refractive index (n d ) is preferably 1.95 to 2.05. From this viewpoint, the lower limit is more preferably 1.97, and even more preferably 1.99, and the upper limit is more preferably 2.03, and even more preferably 2.01.

[0036] The optical glass according to this embodiment has low dispersion (Abbe number (ν d The optical glass according to this embodiment has a high Abbe number (ν d ) is preferably 25 to 40. From this viewpoint, the lower limit is more preferably 27, and even more preferably 29, and the upper limit is more preferably 37, and even more preferably 35.

[0037] The optical glass according to this embodiment can be a thick optical glass. Specifically, the maximum thickness of the optical glass according to this embodiment is preferably 6 mm or more, more preferably 6.2 mm or more, and even more preferably 6.4 mm or more. Here, the "maximum thickness" refers to the maximum value in the thickness direction in the case of a lens shape, and to the diameter value in the case of a substantially spherical shape.

[0038] The optical glass according to this embodiment is suitable as an optical element, such as a lens, for use in optical devices such as cameras and microscopes. Examples of such optical elements include mirrors, lenses, prisms, and filters. Examples of optical systems that include these optical elements include objective lenses, condenser lenses, imaging lenses, and interchangeable camera lenses. These can be used in imaging devices such as interchangeable-lens cameras and non-interchangeable-lens cameras, and microscopes such as multiphoton microscopes. Optical devices are not limited to the imaging devices and microscopes described above, but also include video cameras, teleconverters, telescopes, binoculars, monoculars, laser rangefinders, projectors, and the like. Examples of these devices are described below.

[0039] <Multiphoton microscope> FIG. 1 is a block diagram showing an example of the configuration of a multiphoton microscope equipped with an optical element using optical glass according to this embodiment.

[0040] The multiphoton microscope 1 includes an objective lens 106, a condenser lens 108, and an imaging lens 110. At least one of the objective lens 106, the condenser lens 108, and the imaging lens 110 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 1.

[0041] The pulsed laser device 101 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 101 is generally linearly polarized in a predetermined direction.

[0042] The pulse splitting device 102 splits the ultrashort pulsed light, increases the repetition frequency of the ultrashort pulsed light, and emits it.

[0043] The beam adjusting unit 103 has functions such as adjusting the beam diameter of the ultrashort pulsed light incident from the pulse splitter 102 to match the pupil diameter of the objective lens 106, adjusting the focusing and divergence angles of the ultrashort pulsed light to correct on-axis chromatic aberration (focus difference) between the wavelength of the multiphoton excitation light emitted from the sample S and the wavelength of the ultrashort pulsed light, and a pre-chirp function (group velocity dispersion compensation function) that imparts inverse group velocity dispersion to the ultrashort pulsed light to correct the pulse width of the ultrashort pulsed light that widens due to group velocity dispersion while passing through the optical system.

[0044] The repetition frequency of the ultrashort pulsed light emitted from the pulsed laser device 101 is increased by the pulse dividing device 102, and the above-mentioned adjustment is performed by the beam adjusting unit 103. The ultrashort pulsed light emitted from the beam adjusting unit 103 is then reflected by the dichroic mirror 104 toward the dichroic mirror 105, passes through the dichroic mirror 105, and is collected by the objective lens 106 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).

[0045] 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") with a wavelength shorter than that of the ultrashort pulsed light, which is an infrared wavelength.

[0046] Observation light emitted from the sample S in the direction of the objective lens 106 is collimated by the objective lens 106 and is either reflected by or transmitted through the dichroic mirror 105 depending on its wavelength.

[0047] The observation light reflected by the dichroic mirror 105 enters the fluorescence detection unit 107. The fluorescence detection unit 107 is configured with, for example, a barrier filter, a PMT (photomultiplier tube), etc., receives the observation light reflected by the dichroic mirror 105, and outputs an electrical signal according to the amount of light. Furthermore, the fluorescence detection unit 107 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.

[0048] Meanwhile, the observation light transmitted through the dichroic mirror 105 is descanned by a scanning means (not shown), transmitted through the dichroic mirror 104, collected by the condenser lens 108, passed through a pinhole 109 provided at a position approximately conjugate with the focal position of the objective lens 106, transmitted through an imaging lens 110, and incident on a fluorescence detection unit 111. The fluorescence detection unit 111 is composed of, for example, a barrier filter, a PMT, etc., and receives the observation light imaged on the light receiving surface of the fluorescence detection unit 111 by the imaging lens 110, and outputs an electrical signal according to the amount of light. Furthermore, the fluorescence detection unit 111 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.

[0049] It is also possible to remove the dichroic mirror 105 from the optical path so that all of the observation light emitted from the sample S in the direction of the objective lens 106 is detected by the fluorescence detection unit 111 .

[0050] Furthermore, observation light emitted from the sample S in the direction opposite to the objective lens 106 is reflected by the dichroic mirror 112 and enters the fluorescence detection unit 113. The fluorescence detection unit 113 is composed of, for example, a barrier filter, a PMT, etc., and receives the observation light reflected by the dichroic mirror 112 and outputs an electrical signal according to the amount of light. Furthermore, the fluorescence detection unit 113 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.

[0051] The electrical signals output from the fluorescence detection units 107, 111, and 113 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.

[0052] <Imaging device> The optical element using the optical glass according to this embodiment can also be suitably used in imaging devices such as digital single-lens reflex cameras and digital still cameras.

[0053] FIG. 2 is a perspective view of an imaging device equipped with an optical element using the optical glass according to this embodiment.

[0054] The imaging device 2 is a so-called digital single-lens reflex camera (interchangeable lens camera), and the photographing lens 203 (optical system) is equipped with an optical element whose base material is the optical glass according to this embodiment. A lens barrel 202 is detachably attached to a lens mount (not shown) of a camera body 201. Light passing through a lens 203 of the lens barrel 202 forms an image on a sensor chip (solid-state image sensor) 204 of a multi-chip module 206 arranged on the rear side of the camera body 201. This sensor chip 204 is a bare chip such as a so-called CMOS image sensor. The multi-chip module 206 is, for example, a COG (Chip On Glass) type module in which the sensor chip 204 is bare-chip mounted on a glass substrate 205.

[0055] FIG. 3 is a front view of another example of an imaging device equipped with an optical element using the optical glass according to this embodiment, and FIG. 4 is a rear view of the imaging device of FIG.

[0056] This imaging device CAM is a so-called digital still camera (lens non-interchangeable camera), and the taking lens WL (optical system) is equipped with an optical element whose base material is the optical glass according to this embodiment.

[0057] When the power button (not shown) of the imaging device CAM is pressed, the shutter (not shown) of the taking lens WL is opened, and light from the subject (object) is collected by the taking lens WL and formed into an image on an imaging element arranged on the image plane. The subject image formed on the imaging element is displayed on an LCD monitor LM arranged behind the imaging device CAM. After the photographer decides the composition of the subject image while looking at the LCD monitor LM, 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).

[0058] The image pickup device CAM is provided with an auxiliary light emitting section EF that emits auxiliary light when the subject is dark, a function button B2 used to set various conditions for the image pickup device CAM, and the like.

[0059] Optical systems used in such digital cameras and the like are required to have higher resolution, be lighter in weight, and be smaller in size. To achieve these, it is effective to use glass with a high refractive index in the optical system. From this perspective, the optical glass according to this embodiment is suitable as a component of such optical devices.

[0060] <Optical glass manufacturing method> 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.

[0061] FIG. 5 is a schematic diagram showing the overall configuration of a gas jet levitation furnace, and FIG. 6 is an enlarged schematic diagram of a pedestal on a stage of the gas jet levitation furnace.

[0062] In the gas jet type levitation furnace 3, raw material M is placed on a pedestal 302 on a stage 301. Then, laser light L emitted from a laser light source 303 is irradiated onto raw material M via mirrors 304 and 305. The temperature of raw material M heated by irradiation with laser light L is monitored by a radiation thermometer 306. Based on the temperature information of raw material M monitored by radiation thermometer 306, the output of laser light source 303 is controlled by a computer 307. In addition, the state of raw material M is imaged by a CCD camera 308, and the image is output to a monitor 309 (see FIG. 5). Note that, for example, a carbon dioxide laser can be used as the laser light source.

[0063] In the gas jet type levitation furnace 3, the raw material M is levitated by the gas sent to the pedestal (see FIG. 6). The flow rate of the gas sent to the pedestal is controlled by a gas flow regulator 310. For example, gas can be sprayed from a nozzle with a conical hole, and the raw material M can be levitated and then heated non-contact with laser light L. When the raw material M melts, it takes on a spherical or ellipsoidal shape due to its own surface tension and remains levitated in that state.

[0064] Thereafter, when the laser light L is shut off, the molten raw material is cooled, and transparent glass is obtained. The type of gas is not particularly limited, and any known gas can be used as appropriate, such as oxygen, nitrogen, carbon dioxide, argon, and air. The shape of the nozzle and the heating method are also not particularly limited, and any known method can be used as appropriate.

[0065] Conventionally, when optical glass is produced using a container such as a crucible, it has been necessary to enhance glass-forming ability by adding a large amount of network-forming oxides such as SiO2, BO3, PO5, and GeO2. Therefore, when a glass composition containing a large amount of non-network-forming oxides and a low content of the above-mentioned network-forming oxides is used, crystallization (heterogeneous nucleation) originating from the container-melt interface often occurs, 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.

[0066] 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 a high Abbe number. Because the optical glass according to this embodiment has many advantages, it can be used as a high-refractive-index, low-dispersion glass material or a broadband transmission material. [Example]

[0067] Next, the following examples and comparative examples will be described, but the present invention is not limited to the following examples in any way.

[0068] (Preparation of Optical Glass for Each Example) The optical glass of each example was produced using a gas-jet levitation furnace 3 shown in Figures 5 and 6 according to the following procedure. First, raw materials selected from oxides, hydroxides, carbonates, nitrates, sulfates, etc. were weighed to achieve the desired chemical composition and mixed in an alumina mortar. The raw materials were uniaxially pressed at 20 MPa to form cylindrical pellets. The resulting pellets were fired in an electric furnace at 1000-1300°C in air for 6-12 hours to produce sintered bodies. The resulting sintered bodies were roughly crushed, and 500-600 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 oxygen gas. The melted raw materials took on 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, allowing the raw materials to cool and obtain glass spheres with a diameter of 6 mm. In the glasses of the respective Examples, no visible volatilization was observed during melting, and no bubbles or devitrification were observed.

[0069] (Preparation of Optical Glasses of Comparative Examples) The optical glasses of the comparative examples were also produced using the gas jet type levitation furnace 3 shown in FIGS. 5 and 6, in the same manner as in the above examples.

[0070] (Creating a glass gob) In each example and comparative example, if a roughly spherical glass gob with a diameter of 6 mm was produced, it was recorded as "vitrified," and if the components were not sufficiently melted due to crystallization, it was recorded as "devitrified."

[0071] (Crystallization peak temperature (T p ), glass transition temperature (T g ), and the temperature difference (ΔT) Crystallization peak temperature (T p ) 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 p -T g was defined as the temperature difference (ΔT).

[0072] (Measurement of refractive index and Abbe number) The refractive index of glass was measured using a prism coupler (Metricon, model "2010 / M"). The glass sample was polished, and the polished surface was attached to a single crystal rutile prism. The refractive index was determined by measuring the angle of total reflection when light of the measurement wavelength was incident. Measurements were taken five times 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 measured values ​​were fitted using the Drude-Voigt dispersion equation below by the least squares method to determine the refractive index 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.

[0073]

number

[0074] (n: refractive index, m: electron mass, c: speed of light, e: elementary charge, N: number of molecules per unit volume, f: oscillator strength, λ0: characteristic resonance wavelength, λ: wavelength)

[0075] Also, the Abbe number (ν d ) is defined by the following formula:

[0076]

number

[0077] (n d : refractive index at d line, n F : refractive index at F line, n C : refractive index at C line)

[0078] The compositions and physical properties of each example and comparative example are shown in the tables below. Unless otherwise specified, the content of each component is based on cation %.

[0079] FIG. 7 is a graph plotting the optical constants of each example and each comparative example.

[0080] [Table 1]

[0081] [Table 2]

[0082] [Table 3]

[0083] [Table 4]

[0084] [Table 5]

[0085] From the above, it was confirmed that the optical glasses of the examples combine high refractive index, low dispersion and resistance to devitrification at high levels, and that large glass gobs can be stably produced. [Explanation of symbols]

[0086] 1... multiphoton microscope, 101... pulse laser device, 102... pulse splitter, 103... beam adjustment unit, 104, 105, 112... dichroic mirror, 106... objective lens, 107, 111, 113... fluorescence detection unit, 108... condenser lens, 109... pinhole, 110... imaging lens, 2... imaging device, 201... camera body, 202... lens barrel, 203... lens, 204... sensor chip, 205... glass substrate, 206... Multi-chip module, 3...gas levitation furnace, 301...stage, 302...base, 303...laser light source, 304, 305...mirror, 306...radiation thermometer, 307...computer, 308...CCD camera, 309...monitor, 310...gas flow regulator, L...laser light, M...raw material, S...sample, CAM...imaging device, WL...photographing lens, EF...fill-in light emitter, LM...liquid crystal monitor, B1...release button, B2...function button

Claims

1. In mole percent of cations, Si ４＋ The content is 5 to 20%, Al ３＋ The content is 18 to 35%, La ３＋ , Y ３＋ and Gd ３＋ The total content is 15 to 50%, Zr ４＋ The content is 2 to 15%, Ta ４＋ The content of is 8 to 30%, and Si ４＋ and Al ３＋ Al content relative to the total content ３＋ The ratio of the content of (Al ３＋ / (Si ４＋ +Al ３＋ ) is 0.5 to 0.85; Optical glass.

2. Furthermore, in mole % of cation, Mg ２＋ , Ca ２＋ , Sr ２＋ and Ba ２＋ The total content is 0 to 15%. The optical glass according to claim 1 .

3. Furthermore, in mole % of cation, Ti ４＋ The content of is 0 to 10%.

3. The optical glass according to claim 1.

4. Furthermore, in mole % of cation, Nb ５＋ The content of is 0 to 30%. The optical glass according to any one of claims 1 to 3.

5. B ３＋ and P ５＋ Substantially free of The optical glass according to any one of claims 1 to 4.

6. Li ＋ , Na ＋ , K. ＋ and Cs ＋ Substantially free of 6. The optical glass according to claim 1.

7. Crystallization peak temperature (T ｐ ) - glass transition temperature (T ｇ ) is 130 ° C or more, 7. The optical glass according to claim 1.

8. Refractive index at d line (n ｄ ) is 1.95 to 2.05; The optical glass according to any one of claims 1 to 7.

9. Abbe number (ν ｄ ) is 25 to 40, The optical glass according to any one of claims 1 to 8.

10. The maximum thickness is 6 mm or more. The optical glass according to any one of claims 1 to 9.

11. An optical element made of the optical glass according to any one of claims 1 to 10.

12. An optical system using the optical element according to claim 11.

13. An interchangeable lens comprising the optical system according to claim 12.

14. An optical device comprising the optical system according to claim 12.

Images