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

Abstract

An optical glass having, in mass%, a P2O5 content of 30-70%, a B2O3 content of 0-33%, a BaO content of 5-45%, and a MgO content of more than 0% and 15% or less, wherein the ratio (MgO / (Na2O+K2O)) of the content of MgO to the total content of Na2O and K2O is 4 or more.

Description

Optical glass, optical elements, optical systems, microscope objective lenses, interchangeable camera lenses, cemented lenses and optical devices

[0001] The present invention relates to optical glass, optical elements, optical systems, microscope objective lenses, interchangeable camera lenses, cemented lenses, and optical devices. This invention claims priority from Japanese Patent Application No. 2023-150292 filed on September 15, 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 with low dispersion and low specific gravity is required for microscope lenses, camera lenses, etc.

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

[0004] The first aspect of the present invention is a composition comprising, in mass%, P ２ O ５ Content rate: 30% or more and 70% or less, B ２ O ３ Content: 0% or more and 33% or less, BaO content: 5% or more and 45% or less, MgO content: more than 0% and 15% or less, Na ２ O and K ２ The ratio of the MgO content to the total O content (MgO / (Na ２ O+K ２ O): 4 or more.

[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; ｄ and ν ｄ This is a graph plotting

[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 mass % (mass percentage) of the total weight 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, 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, with the total mass of the oxides being 100 mass%.

[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 the glass transition temperature or when the temperature is lowered from a molten state to or below the liquidus temperature.

[0020] The optical glass according to this embodiment contains, in mass %, P ２ O ５ Content rate: 30% or more and 70% or less, B ２ O ３ Content: 0% or more and 33% or less, BaO content: 5% or more and 45% or less, MgO content: more than 0% and 15% or less, Na ２ O and K ２ The ratio of the MgO content to the total O content (MgO / (Na ２ O+K ２ O): 4 or more.

[0021] The optical glass according to this embodiment has a low refractive index, low dispersion (large Abbe number), and low specific gravity, which is advantageous for aberration correction and allows the realization of lightweight lenses. Conventional optical glasses, for example, tend to have a high refractive index, high dispersion, or a high specific gravity in order to avoid a decrease in devitrification resistance or chemical durability, and this presents a problem in that it is difficult to achieve both refractive index, dispersion performance, and specific gravity. In this regard, the optical glass according to this embodiment can solve this problem while maintaining a low refractive index, low dispersion, and low specific gravity.

[0022] The components of the optical glass according to this embodiment will be described below.

[0023] P ２ O ５ is a component that forms a glass skeleton, improves the stability against devitrification, and reduces the refractive index and chemical durability. ２ O ５ If the content of P is too low, devitrification tends to occur easily.２ O ５ If the content of P is too high, the refractive index and chemical durability tend to decrease. ２ O ５ The content of is 30% or more and 70% or less. The lower limit of this content is preferably 32%, more preferably 34%, and even more preferably 36%. The upper limit of this content is preferably 68%, more preferably 66%, and even more preferably 64%.

[0024] B ２ O ３ is a component for forming a network-forming oxide. ２ O ３ If the content of B is too low, devitrification tends to occur easily. ２ O ３ Since B is a highly volatile component, if it is added in excess, it may cause fluctuations in the composition of the glass during production, and striae may become apparent. ２ O ３ The content of is 0% or more and 33% or less. The lower limit of this content is preferably 1%, more preferably 2%, and even more preferably 3%. The upper limit of this content is preferably 32%, more preferably 31%, and even more preferably 30%.

[0025] P ２ O ５ and B ２ O ３ The total content of (P ２ O ５ +B ２ O ３ ) is preferably 45% or more and 73% or less from the viewpoint of refractive index and devitrification resistance stability. The lower limit of this total content is preferably 46%, more preferably 47%, and even more preferably 48%. The upper limit of this total content is preferably 72%, more preferably 71%, and even more preferably 70%.

[0026] BaO is a component that increases the refractive index. If the BaO content is too low, the refractive index tends to decrease. On the other hand, if the BaO content is too high, the devitrification resistance tends to decrease. From this viewpoint, the BaO content is 5% or more and 45% or less. The lower limit of this content is preferably 6%, more preferably 7%, and even more preferably 8%. The upper limit of this content is preferably 44%, more preferably 43%, and even more preferably 42%.

[0027] MgO is a component that improves the devitrification resistance stability without increasing the specific gravity. If MgO is not contained, the devitrification resistance stability decreases, making it difficult to achieve a low specific gravity. Furthermore, if the MgO content is too high, the refractive index tends to increase. From this perspective, the MgO content is greater than 0% and not more than 15%. The lower limit of this content is preferably 0.5%, more preferably 1.0%, and even more preferably 1.5%. The upper limit of this content is preferably 14%, more preferably 13%, and even more preferably 12%.

[0028] Na ２ O is a component that improves the melting property and decreases the refractive index. ２ If the O content is too low, the melting property tends to decrease. ２ If the O content is too high, the refractive index and chemical durability tend to decrease. ２ The O content is 0% or more and 3.75% or less. The lower limit of this content is preferably 0.3%, more preferably 0.5%. The upper limit of this content is preferably 3.5%, more preferably 3.2%.

[0029] K ２ O is a component that improves the melting property and lowers the refractive index. ２ If the O content is too low, the melting property tends to decrease. ２ If the O content is too high, the refractive index and chemical durability tend to decrease. ２The O content is 0% or more and 3.75% or less. The lower limit of this content is preferably 0.3%, more preferably 0.5%. The upper limit of this content is preferably 3.5%, more preferably 3.2%.

[0030] Na ２ O and K ２ Total O content (Na ２ O+K ２ From the viewpoints of meltability, refractive index, and chemical durability, the total content of 0 is greater than 0% and not more than 3.75%. The lower limit of this total content is preferably 0.3%, more preferably 0.5%, and even more preferably 0.8%. The upper limit of this total content is preferably 3.5%, more preferably 3.2%, and even more preferably 3.0%.

[0031] Na ２ O and K ２ The ratio of the MgO content to the total O content (MgO / (Na ２ O+K ２ The ratio MgO / (Na) is 4 or more. The lower limit of this ratio is preferably 5.0, more preferably 5.5, and even more preferably 6.0. The upper limit of this ratio is preferably 12, more preferably 11.5, and even more preferably 11. ２ O+K ２ By setting the content of O in this range, it is possible to achieve a low specific gravity without reducing the stability against devitrification.

[0032] The optical glass according to this embodiment further contains La ２ O ３ , Y ２ O ３ , SiO ２ , Al ２ O ３ , CaO, SrO, Sb ２ O ３ It may also contain other ingredients such as:

[0033] La ２ O ３ is a component that has the effect of increasing the refractive index without impairing low dispersion, and can also maintain the stability of the glass against devitrification. ２ O ３If the content of La is too low, the refractive index tends to decrease. ２ O ３ If the content of La is too high, the resistance to devitrification tends to decrease. ２ O ３ The content of is 0% or more and 8% or less. The lower limit of this content is preferably 0.1%, more preferably 0.2%, and even more preferably 0.3%. The upper limit of this content is preferably 7%, more preferably 6%, and even more preferably 5%.

[0034] Y ２ O ３ is a component that can increase the refractive index without impairing low dispersion. ２ O ３ If the content of Y is too low, the refractive index tends to decrease. ２ O ３ If the content of Y is too high, the resistance to devitrification tends to decrease. ２ O ３ The content of is 0% or more and 8% or less. The lower limit of this content is preferably 0.1%, more preferably 0.2%, and even more preferably 0.3%. The upper limit of this content is preferably 7%, more preferably 6%, and even more preferably 5%.

[0035] SiO ２ is a component that constitutes a network-forming oxide, and is a component that can improve the melting property and devitrification resistance stability, while at the same time maintaining a low specific gravity. ２ If the content is too low, the melting property tends to decrease. ２ If the content of SiO is too high, the refractive index and chemical durability tend to decrease. ２ The content of is 0% or more and 5% or less. The lower limit of this content is preferably 0.5%, more preferably 1.0%, and even more preferably 1.5%. The upper limit of this content is preferably 4.5%, more preferably 4.0%, and even more preferably 3.5%.

[0036] Al ２ O３ is a component that improves chemical durability. ２ O ３ If the content of Al is too low, the chemical durability tends to decrease. ２ O ３ If the content of Al is too high, the melting property tends to deteriorate. ２ O ３ The content of is 0% or more and 10% or less. The lower limit of this content is preferably 0.5%, more preferably 1.0%, and even more preferably 1.5%. The upper limit of this content is preferably 9.5%, more preferably 9.0%, and even more preferably 8.5%.

[0037] CaO is a component useful for adjusting the constants of glass. From this viewpoint, the CaO content is 0% or more and 15% or less. The lower limit of this content is preferably 0.5%, more preferably 1.0%, and even more preferably 1.5%. The upper limit of this content is preferably 14%, more preferably 13%, and even more preferably 12%.

[0038] SrO is a component useful for adjusting the constants of glass. From this viewpoint, the SrO content is 0% or more and 30% or less. The lower limit of this content is preferably 0.5%, more preferably 1.0%, and even more preferably 1.5%. The upper limit of this content is preferably 29%, more preferably 28%, and even more preferably 27%.

[0039] Sb ２ O ３ is a component that functions as a defoaming agent for fining glass. ２ O ３ If the content of Sb is too high, the transmittance tends to decrease. ２ O ３ The content is 0% or more and 1% or less. The lower limit of this content is preferably more than 0%, more preferably 0.02%, and even more preferably 0.03%. The upper limit of this content is preferably 0.5%.

[0040] From the viewpoint of adjusting the glass constants, the total content of BaO, CaO, and SrO (BaO + CaO + SrO) is preferably 10% or more and 46% or less. The lower limit of this total content is preferably 11%, more preferably 12%, and even more preferably 13%. The upper limit of this total content is preferably 45%, more preferably 44%, and even more preferably 43%.

[0041] The ratio of the MgO content to the total content of BaO, CaO, and SrO (MgO / (BaO+CaO+SrO)) is preferably greater than 0 and not greater than 0.4, from the viewpoints of adjusting the glass constants and devitrification resistance stability. The lower limit of this ratio is preferably 0.04, more preferably 0.08, and even more preferably 0.12. The upper limit of this ratio is preferably 0.36, more preferably 0.32, and even more preferably 0.28.

[0042] 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.

[0043] The method for producing the optical glass according to this embodiment is not particularly limited, and known methods can be employed. Furthermore, suitable production conditions can be selected as appropriate. For example, a production method can be employed in which raw materials such as oxides, carbonates, nitrates, and sulfates are blended to achieve a target composition, melted preferably at 1100 to 1400°C, homogenized by stirring, bubble-removing, and then poured into a mold for molding. The lower limit of the melting temperature mentioned above is more preferably 1200°C, and the upper limit is more preferably 1350°C, and even more preferably 1300°C. The optical glass thus obtained can be processed into a desired shape by, for example, reheat pressing, as necessary, and then polished to form a desired optical element.

[0044] It is preferable to use high-purity raw materials with low impurity content. A high-purity raw material 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.

[0045] Next, the physical properties of the optical glass of this embodiment will be described.

[0046] 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 1.59, more preferably 1.58, and even more preferably 1.57.

[0047] The Abbe number (ν ｄ ) is 64 or more and 70 or less. ｄ The lower limit of the Abbe number (ν ｄ The upper limit of the saturation temperature is preferably 69.5, more preferably 69, and even more preferably 68.5.

[0048] 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 1.53 to 1.60, and the Abbe number (ν ｄ ) is in the range of 64 or more and 70 or less. The optical glass according to this embodiment having such properties can be combined with, for example, other optical glasses to design an optical system in which chromatic aberration and other aberrations are well corrected.

[0049] The specific gravity (S ｇ ) is 2.6 or more and 3.5 or less. ｇ The lower limit of the specific gravity (S ｇ The upper limit of the saturation temperature is preferably 3.4, more preferably 3.3, and even more preferably 3.2.

[0050] From the above viewpoint, the optical glass according to this embodiment can be suitably used, for example, as an optical element. Examples of such optical elements include mirrors, lenses, prisms, and filters. Examples of optical systems that use the optical elements include objective lenses, condenser lenses, imaging lenses, and interchangeable camera lenses. 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 microscope devices, 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, and the like. Examples of these optical devices are described below.

[0051] <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.

[0052] 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.

[0053] 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 LCD monitor M located behind the imaging device CAM. After the photographer decides the composition of the subject image while looking at the LCD 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).

[0054] 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.

[0055] 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 low dispersion and a high partial dispersion ratio (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.

[0056] <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.

[0057] 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.

[0058] The pulse splitting device 202 splits the ultrashort pulsed light, increases the repetition frequency of the ultrashort pulsed light, and emits it.

[0059] 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 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) to impart reverse group velocity dispersion to the ultrashort pulsed light in order to correct the pulse width of the ultrashort pulsed light being broadened by group velocity dispersion while passing through the optical system.

[0060] 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).

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] <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.

[0069] 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.

[0070] Next, examples of the present invention and comparative examples will be described, but the present invention is not limited to these.

[0071] <Preparation of Optical Glass> The optical glasses according to each example and comparative example were prepared by the following procedure. First, glass raw materials selected from oxides, hydroxides, phosphate compounds (phosphates, orthophosphates, etc.), carbonates, nitrates, etc. were weighed out so as to obtain the composition (mass %) shown in each table. Next, the weighed raw materials were mixed and placed in a platinum crucible, melted at a temperature of 1100 to 1350°C, and stirred to be homogenized. After bubble removal, the mixture was cooled to an appropriate temperature and then cast into a mold, slowly cooled, and molded to obtain each sample.

[0072] <Physical property evaluation> FIG. 6 shows the n ｄ and ν ｄ This is a graph plotting

[0073] Refractive index (n ｄ ) and Abbe number (ν ｄ ) Refractive index (n ｄ ) and Abbe number (ν ｄ ) was measured and calculated using a refractive index measuring instrument (Shimadzu Device Manufacturing Co., Ltd.: KPR-3000). ｄ indicates the refractive index of glass for light of 587.562 nm. ｄ ) is rounded to six decimal places. ｄ was calculated from the following formula (1): Ｃ , n Ｆ , and represent 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 ) ... (1)

[0074] Specific gravity (S ｇ ) Specific gravity of each sample (S ｇ ) was measured by the Archimedes method as the mass ratio to the same volume of pure water at 4°C.

[0075] The compositions of the optical glasses of each example and comparative example, expressed in mass % based on the oxide content of each component, and the evaluation results of each physical property are shown in Tables 1 to 4. In comparative examples 1 and 3, optical glasses could not be obtained, and therefore the numerical values ​​of physical properties were "impossible to measure." In comparative example 2, a glass with a higher specific gravity than the glass of this embodiment was obtained.

[0076]

[0077]

[0078]

[0079]

[0080] From the above, it was confirmed that the optical glass of this example has a low refractive index, low dispersion, and excellent stability against devitrification. It was also confirmed that it has a low specific gravity, which contributes to weight reduction of the optical system.

[0081] REFERENCE SIGNS LIST 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 adjusting unit, 204, 205, 212...dichroic mirror, 206...objective lens, 207, 211, 213...fluorescence detecting unit, 208...condensing lens, 209...pinhole, 210...imaging lens, S...sample, 3...cemented lens, 301...first lens element, 302...second lens element, 303...cementing member

Claims

1. Mass %: P ２ O ５ Content rate: 30% or more and 70% or less, B ２ O ３ Content: 0% or more and 33% or less, BaO content: 5% or more and 45% or less, MgO content: more than 0% and 15% or less, Na ２ O and K ２ Total O content (Na ２ O+K ２ The ratio of the content of MgO to the content of Na ２ O+K ２ O) ): 4 or more.

2. Mass %: P ２ O ５ and B ２ O ３ Total content of (P ２ O ５ +B ２ O ３ 2. The optical glass according to claim 1, wherein the refractive index is 45% or more and 73% or less.

3. By mass%, La ２ O ３ Content rate: 0% or more and 8% or less, Y ２ O ３ 3. The optical glass according to claim 1, wherein the content is 0% or more and 8% or less.

4. By mass%, SiO ２ Content rate: 0% or more and 5% or less B ２ O ３ Content rate: 0% or more and 40% or less, Al ２ O ３ The optical glass according to any one of claims 1 to 3, wherein the content is 0% or more and 10% or less.

5. The optical glass according to any one of claims 1 to 4, having, by mass%, CaO content: 0% or more and 15% or less, and SrO content: 0% or more and 30% or less.

6. Sb (by mass%) ２ O ３ The optical glass according to any one of claims 1 to 5, wherein the content is 0% or more and 1% or less.

7. The optical glass according to any one of claims 1 to 6, wherein the total content of BaO, CaO and SrO (BaO + CaO + SrO) is 10% or more and 46% or less by mass.

8. The optical glass according to any one of claims 1 to 7, wherein the ratio of the content of MgO to the total content of BaO, CaO, and SrO (MgO / (BaO+CaO+SrO)) is greater than 0 and equal to or less than 0.4, in mass %.

9. Refractive index for d line (n ｄ 9. The optical glass according to claim 1, wherein the refractive index is 1.53 or greater and 1.60 or less.

10. Abbe number (ν ｄ 10. The optical glass according to claim 1, wherein n is 64 or more and 70 or less.

11. Specific gravity (S ｇ 11. The optical glass according to claim 1, wherein the refractive index is 2.6 or more and 3.5 or less.

12. An optical element using the optical glass according to any one of claims 1 to 11.

13. An optical system comprising the optical element according to claim 12.

14. An objective lens for a microscope, comprising the optical system according to claim 13.

15. An interchangeable lens for a camera, comprising the optical system according to claim 13.

16. An optical device comprising the optical system of claim 13.

17. 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 11.

18. An optical system comprising the cemented lens according to claim 17.

19. An objective lens for a microscope comprising the optical system according to claim 18.

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

21. An optical device comprising the optical system of claim 18.

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