Optical glass, optical elements, optical systems, interchangeable lenses and optical devices

Abstract

To provide a high-dispersion, low-specific-gravity optical glass for use in imaging devices equipped with image sensors with a high number of pixels. The composition is, in mass%, a P2O5 component: 24.5 to 41%, a Na2O component: 6 to 17%, a K2O component: 5 to 15%, an Al2O3 component: more than 0% and 7% or less, a TiO2 component: 8 to 21%, and a Nb2O5 component: 5 to 38%, and the partial dispersion ratio (P g,F ) is 0.634 or less.

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. 2018-224548, filed on November 30, 2018, 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] Known examples of optical glass that can be used in imaging devices and the like include the glass described in Patent Document 1. In recent years, imaging devices and the like equipped with image sensors with a high number of pixels have been developed, and optical glasses for use therein are required to have high dispersion and low specific gravity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-219365 Summary of the Invention

[0004] The first aspect of the present invention is a ceramic composition having, in mass %, a P2O5 component of 24.5 to 41%, a Na2O component of 6 to 17%, a K2O component of 5 to 15%, an Al2O3 component of more than 0% and 7% or less, a TiO2 component of 8 to 21%, and a Nb2O5 component of 5 to 38%, and a partial dispersion ratio (P g,F ) is 0.634 or less.

[0005] A second aspect of the present invention is an optical element using the optical glass described above.

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

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

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

[0009] [Figure 1] FIG. 1 is a perspective view of an imaging device equipped with an optical element using the optical glass according to this embodiment. [Figure 2] FIG. 2 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 3] FIG. 3 is a rear view of the imaging device of FIG. [Figure 4] FIG. 4 is a block diagram showing an example of the configuration of a multiphoton microscope according to this embodiment. [Figure 5] FIG. 5 is a graph plotting the optical constants of each example. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] 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 oxide composition. The oxide 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 components of this embodiment are all decomposed and converted to oxides during melting, with the total mass of the oxides being 100 mass%.

[0012] The optical glass according to this embodiment contains, in mass %, a P2O5 component of 24.5 to 41%, a Na2O component of 6 to 17%, a K2O component of 5 to 15%, an Al2O3 component of more than 0% and 7% or less, a TiO2 component of 8 to 21%, and an Nb2O5 component of 5 to 38%.g,F ) is 0.634 or less.

[0013] Conventionally, attempts have been made to achieve high dispersion by increasing the content of components such as TiO2 and Nb2O5. However, increasing the content of these components tends to result in a decrease in transmittance and an increase in specific gravity. In this regard, the optical glass according to this embodiment can achieve a low specific gravity while maintaining high dispersion, thereby enabling the lens to be made lighter.

[0014] First, each component of the optical glass according to this embodiment will be described.

[0015] P2O5 is a component that forms a glass skeleton, improves devitrification resistance, and reduces the refractive index and chemical durability. If the P2O5 content is too low, devitrification tends to occur more easily. On the other hand, if the P2O5 content is too high, the refractive index and chemical durability tend to decrease. From these perspectives, the P2O5 content is 24.5% or more and 41% or less. The lower limit of this content is preferably 25% or more, more preferably 28% or more, and the upper limit of this content is preferably 40% or less, more preferably 37% or less. By setting the P2O5 content within this range, it is possible to improve devitrification resistance and chemical durability while achieving a high refractive index.

[0016] Na2O is a component that improves meltability and reduces chemical durability. If the Na2O content is too low, meltability tends to decrease. From this perspective, the Na2O content is 6% or more and 17% or less. The lower limit of this content is preferably 7% or more, more preferably 8% or more, and the upper limit of this content is preferably 15% or less, more preferably 14% or less.

[0017] K2O is a component that improves meltability and reduces chemical durability. If the K2O content is too low, meltability tends to decrease. From this perspective, the K2O content is 5% or more and 15% or less. The lower limit of this content is preferably 6% or more, more preferably 7% or more, and the upper limit of this content is preferably 13% or less, more preferably 12% or less.

[0018] Al2O3 is a component that improves chemical durability and reduces devitrification resistance. If the Al2O3 content is too low, chemical durability tends to decrease. From this perspective, the Al2O3 content is more than 0% and not more than 7%. The lower limit of this content is preferably 0.5% or more, more preferably 1% or more, and the upper limit of this content is preferably 6.5% or less, more preferably 5% or less, and even more preferably 4% or less.

[0019] TiO2 is a component that increases the refractive index and decreases the transmittance. A high TiO2 content tends to decrease the transmittance. From this perspective, the TiO2 content is 8% or more and 21% or less. The lower limit of this content is preferably 9% or more, more preferably 10% or more, and the upper limit of this content is preferably 20% or less, more preferably 19.5% or less, and even more preferably 19% or less.

[0020] Nb2O5 is a component that increases the refractive index and dispersion and decreases the transmittance. If the Nb2O5 content is low, the refractive index tends to decrease. On the other hand, if the Nb2O5 content is high, the transmittance tends to decrease. From this perspective, the Nb2O5 content is 5% or more and 38% or less. The lower limit of this content is preferably 6% or more, more preferably 7% or more, and the upper limit of this content is preferably 36% or less, more preferably 34% or less.

[0021] Furthermore, the optical glass according to this embodiment may further contain one or more elements selected from the group consisting of SiO2, B2O3, Bi2O3, MgO, Li2O, CaO, BaO, SrO, ZnO, ZrO2, Y2O3, La2O3, Gd2O3, WO3, and Sb2O3.

[0022] SiO2 is a component effective for adjusting constants, and from the viewpoint of further improving devitrification resistance, the upper limit of the content is preferably 3.5% or less, and more preferably 2% or less.

[0023] B2O3 is a component effective for adjusting constants, and from the viewpoint of further improving devitrification resistance, the upper limit of the content is preferably 10% or less, more preferably 7% or less.

[0024] Bi2O3 is a component that is effective in improving devitrification resistance, but is also a component that deteriorates transmittance performance. From the viewpoint of not deteriorating transmittance performance, the upper limit of the Bi2O3 content is preferably 5% or less, more preferably 3% or less.

[0025] MgO is an effective component for increasing the refractive index, and from the viewpoint of further improving resistance to devitrification, the upper limit of the content is preferably 2% or less.

[0026] Li2O is a component that improves meltability and increases the refractive index. From the viewpoint of further improving devitrification resistance, the upper limit of the content of Li2O is preferably 3.5% or less, and more preferably 2% or less.

[0027] CaO is an effective component for increasing the refractive index, and from the viewpoint of further improving the devitrification resistance, the upper limit of the CaO content is preferably 9.5% or less, and more preferably 8% or less.

[0028] BaO is an effective component for increasing the refractive index, and from the viewpoint of further improving the devitrification resistance, the upper limit thereof is preferably 9% or less, and more preferably 8.5% or less.

[0029] The SrO component is an effective component for increasing the refractive index, and from the viewpoint of further improving the devitrification resistance, the upper limit thereof is preferably 1.5% or less, and more preferably 0.5% or less.

[0030] ZnO is a component effective in increasing the refractive index and dispersion, and from the viewpoint of further improving devitrification resistance, the upper limit of the content is preferably 5% or less, more preferably 4% or less.

[0031] ZrO2 is a component effective in increasing the refractive index and dispersion, and from the viewpoint of further improving resistance to devitrification, the upper limit of the content is preferably 6% or less, more preferably 4% or less.

[0032] Y2O3 is a component effective in increasing the refractive index, and from the viewpoint of further improving the devitrification resistance, the upper limit of the content is preferably 1.5% or less, and more preferably 0.5% or less.

[0033] La2O3 is a component effective in increasing the refractive index, and from the viewpoint of further improving devitrification resistance, the upper limit of the content is preferably 1.5% or less, and more preferably 0.5% or less.

[0034] Gd2O3 is a component effective in increasing the refractive index, and from the viewpoint of further improving the devitrification resistance, the upper limit of the Gd2O3 content is preferably 2% or less, and more preferably 0.5% or less.

[0035] The content of WO3 is an effective component for increasing the refractive index and dispersion, but since it is an expensive raw material, the upper limit of the content is preferably 3% or less, and more preferably 2% or less.

[0036] Although Sb2O3 is effective as a defoaming agent, if it is contained in an amount exceeding a certain level, it deteriorates the transmittance performance of the glass. In order to improve the transmittance performance of the glass, the upper limit of the Sb2O3 content is preferably 0.4% or less, and more preferably 0.2% or less.

[0037] The optical glass according to this embodiment is excellent in terms of raw material costs, since it is possible to reduce the content of Ta2O5, which is an expensive raw material, or even to not contain it at all.

[0038] Suitable combinations of these include SiO2 component: 0-3.5%, B2O3 component: 0-10%, Bi2O3 component: 0-5%, MgO component: 0-2%, Li2O component: 0-3.5%, CaO component: 0-9.5%, BaO component: 0-9%, SrO component: 0-1.5%, ZnO component: 0-5%, ZrO2 component: 0-6%, Y2O3 component: 0-1.5%, La2O3 component: 0-1.5%, Gd2O3 component: 0-2%, WO3 component: 0-3%, and Sb2O3 component: 0-0.4%.

[0039] In addition, the following are further preferred examples of the combination and proportion of each component.

[0040] The total content of P2O5 and B2O3 (P2O5 + B2O3) is preferably 28 to 43%. The lower limit of the total content is more preferably 30% or more, and the upper limit of the total content is more preferably 39%. By keeping P2O5 + B2O3 in this range, the refractive index can be increased.

[0041] The ratio of B2O3 to P2O5 (B2O3 / P2O5) is preferably 0 or more and 0.24 or less. The lower limit of this ratio is more preferably 0.015 or more, and the upper limit of this ratio is more preferably 0.21 or less. By setting B2O3 / P2O5 in this range, it is possible to improve devitrification resistance and increase the refractive index.

[0042] The ratio of TiO2 to P2O5 (TiO2 / P2O5) is preferably 0.3 or more and 0.7 or less. The lower limit of this ratio is more preferably 0.4 or more, and the upper limit of this ratio is more preferably 0.6 or less. By setting TiO2 / P2O5 in this range, it is possible to improve devitrification resistance and increase the refractive index.

[0043] The ratio of Nb2O5 to P2O5 (Nb2O5 / P2O5) is preferably 0.1 or more and 1.3 or less. The lower limit of this ratio is more preferably 0.2 or more, and the upper limit of this ratio is more preferably 1.2 or less. By setting Nb2O5 / P2O5 in this range, the refractive index can be increased.

[0044] The total content of Li2O, Na2O, and K2O (Li2O + Na2O + K2O) is preferably 14% or more and 25% or less. The lower limit of the total content of these elements is more preferably 15% or more, and the upper limit of the total content of these elements is more preferably 23% or less. By keeping Li2O + Na2O + K2O within this range, it is possible to improve the melting property without reducing the chemical durability.

[0045] 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 clarification, coloring, decolorization, fine adjustment of optical constants, etc. In addition to the components described above, other components may also be added within the range in which the effects of the optical glass of this embodiment can be obtained.

[0046] The method for producing the optical glass according to this embodiment is not particularly limited, and known methods can be employed. Furthermore, the production conditions can be appropriately selected from known conditions. One suitable example is a method including the steps of selecting, as glass raw materials, one selected from oxides, hydroxides, phosphate compounds (phosphates, orthophosphates, etc.), carbonates, nitrates, etc., corresponding to the above-mentioned raw materials, mixing them, melting them at a temperature of 1100 to 1400°C, stirring and homogenizing them, and then cooling and shaping them.

[0047] More specifically, a manufacturing method can be used in which raw materials such as oxides, carbonates, nitrates, and sulfates are mixed to achieve the target composition, melted at preferably 1100 to 1400°C, more preferably 1100 to 1300°C, and even more preferably 1100 to 1250°C, homogenized by stirring, bubble-removal, and then cast into a mold. The optical glass obtained in this manner can be processed into the desired shape by reheat pressing or other processes as needed, and polished to obtain the desired optical glass or optical element.

[0048] Furthermore, the optical glass composition according to this embodiment is easy to melt, and therefore easy to stir and homogenize, resulting in excellent production efficiency. That is, when 50 g of raw materials for the optical glass are heated at a temperature of 1100 to 1250°C, the time it takes for the raw materials to melt is preferably less than 15 minutes, more preferably 13 minutes or less, and even more preferably 10 minutes or less. Here, the "time until melting" refers to the time from the start of heating and holding the raw materials necessary for forming the optical glass until these raw materials have melted and are no longer visible near the liquid surface.

[0049] In the temperature range of 1100 to 1250°C, the glass frits are melted in a short time as described above, so that the remaining glass frits can be prevented from being mixed into the glass. Furthermore, if the remaining glass frits are forcibly melted by heating at a high temperature or by maintaining the heat for a long time, this can cause a decrease in the production efficiency of the glass and a deterioration in the transmittance, but according to this embodiment, such problems do not occur.

[0050] Furthermore, it is preferable to use high-purity raw materials with low impurity content. A high-purity product is one that contains 99.85% or more by mass of the relevant component. The use of high-purity products reduces the amount of impurities, which tends to increase the internal transmittance of the optical glass.

[0051] Next, various physical properties of the optical glass of this embodiment will be described.

[0052] The optical glass according to this embodiment has a partial dispersion ratio (P g,F) is 0.634 or less. In addition, the optical glass according to this embodiment has a large partial dispersion ratio (P g,F ), which is effective for correcting lens aberrations. From this perspective, the partial dispersion ratio (P g,F The lower limit of the partial dispersion ratio (P g,F ) is more preferably 0.632 or less.

[0053] 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 higher the refractive index, the greater the specific gravity. In light of this situation, the refractive index (n d ), and the refractive index (n d The lower limit of the refractive index (n d ) is more preferably 1.80 or less.

[0054] The Abbe number (ν d ) is preferably in the range of 22 to 32. d The lower limit of the Abbe number (ν d ) is more preferably 29 or less, and even more preferably 28 or less.

[0055] The refractive index (n d ) and Abbe number (ν d ) is a preferred combination of refractive index (n d ) is 1.66 to 1.81, and the Abbe number (ν d ) is 22 to 32. The optical glass according to this embodiment, which has such properties, can be combined with other optical glasses and used as a convex lens in a group of concave lenses, making it possible to design an optical system in which chromatic aberration and other aberrations are well corrected.

[0056] From the viewpoint of reducing the lens weight, it is desirable that the optical glass according to this embodiment has a low specific gravity. However, generally, the lower the specific gravity, the lower the refractive index tends to be. In light of this situation, the optical glass according to this embodiment preferably has a specific gravity in the range of 2.8 to 3.4, with a lower limit of 2.8 and an upper limit of 3.4.

[0057] The value indicating anomalous dispersion (ΔP g,F ) is preferably 0.0190 to 0.0320. The upper limit is more preferably 0.0315 or less, and even more preferably 0.0310 or less, and the lower limit is more preferably 0.0200 or more, and even more preferably 0.0210 or more. ΔP g,F is an index of anomalous dispersion, and can be determined in accordance with the method described in the Examples below.

[0058] From the above viewpoint, the optical glass according to this embodiment has low raw material costs, a low specific gravity, and high dispersion (Abbe number (ν d ) is small). Also, the value indicating anomalous dispersion (ΔP g,F ) and partial dispersion ratio P g,F The optical glass according to this embodiment is suitable for use as an optical element such as a lens included in an optical device such as a camera or a microscope. Such optical elements include mirrors, lenses, prisms, filters, etc. Examples of optical systems including these optical elements include objective lenses, condenser lenses, imaging lenses, and interchangeable lenses for cameras. These can be used in imaging devices such as interchangeable lens cameras and non-interchangeable lens cameras, and microscopes such as multiphoton microscopes. Note that 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, etc. Examples of these devices are described below.

[0059] <Imaging device> FIG. 1 is a perspective view of an imaging device equipped with an optical element using the optical glass according to this embodiment.

[0060] The imaging device 1 is a so-called digital single-lens reflex camera (interchangeable lens camera), and the taking lens 103 (optical system) is equipped with 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 a 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.

[0061] FIG. 2 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. 3 is a rear view of the imaging device of FIG.

[0062] 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.

[0063] 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).

[0064] 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.

[0065] The optical systems used in digital cameras and other devices require higher resolution, lighter weight, and smaller size. To achieve these, it is effective to use glass with a high refractive index. In particular, glass with a high refractive index and a low specific gravity (S g ) and has high press formability, there is a 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.

[0066] <Multiphoton microscope> FIG. 4 is a block diagram showing an example of the configuration of a multiphoton microscope 2 equipped with an optical element using optical glass according to this embodiment.

[0067] 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.

[0068] 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 (for example, 100 femtoseconds). The ultrashort pulsed light immediately after being emitted from the pulsed laser device 201 is generally linearly polarized in a predetermined direction.

[0069] The pulse splitting device 202 splits the ultrashort pulsed light, increases the repetition frequency of the ultrashort pulsed light, and emits it.

[0070] 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 splitter 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 the axial 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 an inverse 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.

[0071] 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. Then, the ultrashort pulsed light emitted from the beam adjusting unit 203 is 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).

[0072] 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.

[0073] Observation light emitted from the sample S in the direction of the objective lens 206 is collimated by the objective lens 206 and is either reflected by or transmitted through the dichroic mirror 205 depending on its wavelength.

[0074] The observation light reflected by the dichroic mirror 205 enters the fluorescence detection unit 207. The fluorescence detection unit 207 is configured with, 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 according 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.

[0075] On the other hand, the observation light that has passed through the dichroic mirror 205 is descanned by a scanning means (not shown), passes through the dichroic mirror 204, is focused by the focusing lens 208, passes through a pinhole 209 located at a position approximately conjugate with the focal position of the objective lens 206, passes through an imaging lens 210, and enters the fluorescence detection unit 211.

[0076] 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.

[0077] 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 .

[0078] 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 configured, for example, with 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.

[0079] 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. [Example]

[0080] Next, the following examples and comparative examples will be described, but the present invention is not limited to the following examples in any way.

[0081] <Production of optical glass> The optical glasses according to the examples and comparative examples were produced 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 1300°C for about 70 minutes, and stirred to homogenize. After bubbles were removed, the mixture was cooled to an appropriate temperature, poured into a mold, slowly cooled, and molded to obtain each sample.

[0082] 1. Refractive index (n d ) and Abbe number (ν d ) The 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-2000). d indicates the refractive index of glass for d-line light (wavelength 587.562 nm). d was calculated using the following formula (1): C , n F indicate the refractive index of the glass for the C line (wavelength 656.273 nm) and the F line (wavelength 486.133 nm), respectively. ν d =(n d -1) / (n F -n C )···(1)

[0083] 2. Partial dispersion ratio (P g,F ) The partial variance ratio (P g,F ) is the principal variance (n F -n C ) for partial variance (n g -n F ) and was calculated using the following formula (2): g indicates the refractive index of glass for the g-line (wavelength 435.835 nm). P g,F =(n g -n F ) / (n F -n C )···(2)

[0084] 3. Value indicating anomalous dispersion (ΔP g,F ) The value indicating the anomalous dispersion of each sample (ΔP g,F ) was determined in accordance with the method shown below.

[0085] (1) Creating a reference line First, as normal partial dispersion glass, the Abbe number (ν d ) and partial variance ratio (P g,F Two glasses, "F2" and "K7", having the same Abbe number (ν d ) and the vertical axis is the partial variance ratio (P g,F ) and the line connecting the two points corresponding to the two reference materials was used as the reference line. Characteristics of Glass "F2": ν d =36.33, P g,F =0.5834 Characteristics of glass "K7": ν d =60.47, P g,F =0.5429

[0086] (2)ΔP g,F Calculation of Next, the horizontal axis is the Abbe number (ν d ), and the vertical axis is the partial variance ratio (Pg,F ) on a graph (see FIG. 5), the values ​​corresponding to the optical glasses of the examples were plotted, and the Abbe number (ν d ) and its vertical axis value (P g,F ) is the value indicating anomalous dispersion (ΔP g,F ) was calculated. The partial variance ratio (P g,F ) is above the reference line, ΔP g,F has a positive value, and the partial variance ratio (P g,F ) is below the reference line, ΔP g,F has a negative value.

[0087] 4. Specific gravity (S g ) The specific gravity (S g ) was calculated from the mass ratio to the same volume of pure water at 4°C.

[0088] 5.Melting time of glass raw materials The melting time of the glass raw materials means the time from when 50 g of the glass raw materials are thoroughly mixed and placed in a platinum crucible, and when heating is started at a temperature of 1100 to 1250° C. until the glass raw materials are melted. In this example, it was determined that the glass raw materials were melted when the remaining glass raw materials could no longer be visually confirmed on the glass liquid surface in the platinum crucible.

[0089] The compositions and physical properties of each example and comparative example are shown in each table. Unless otherwise specified, the content of each component is expressed in mass %.

[0090] FIG. 5 is a graph plotting the optical constants of each example.

[0091] [Table 1]

[0092] [Table 2]

[0093] [Table 3]

[0094] [Table 4]

[0095] [Table 5]

[0096] The optical glass of this example has a high dispersion, a low specific gravity, and a large ΔP g,F and P g,F It was confirmed that the glass had excellent values. Furthermore, it was confirmed that the production efficiency was excellent because the time required to melt the glass raw materials during glass production was short. Note that, in Comparative Examples 1 to 4, it was impossible to measure various physical property values ​​due to devitrification. [Explanation of symbols]

[0097] 1 imaging device, 101 camera body, 102 lens barrel, 103 lens, 104 sensor chip, 105 glass substrate, 106 multi-chip module, 2 multiphoton microscope, 201 pulse laser device, 202 pulse splitter, 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, CAM imaging device, WL imaging lens, EF auxiliary light emitter, LM liquid crystal monitor, B1 release button, B2 function button

Claims

1. An optical glass comprising P 2 O 5 , Na 2 O, K 2 O, Nb 2 O 5 and TiO 2 , In mass%, P ２ O ５ Content percentage: 24.5% to 41% B 2 O 3 content: 0% or more and 7% or less, SiO 2 content: 0% or more and 3.5% or less, Nb ２ O ５ Content rate: 5% or more TiO ２ Content rate: below 21% Optical glass.

2. Na 2 O content: 6% or more, K 2 O content: 12% or less; The optical glass according to claim 1 .

3. K 2 O content: 5% or more and 10.72% or less, 3. The optical glass according to claim 1.

4. Na 2 O content: 15.83% or more, The optical glass according to any one of claims 1 to 3.

5. In mass %, MgO content: 0% or more and 2% or less, CaO content: 0% or more and 9.5% or less, BaO content: 0% or more and 9% or less, SrO content: 0% or more and 1.5% or less; 5. The optical glass according to claim 1.

6. In mass %, Y 2 O 3 content: 0% or more and 1.5% or less, La 2 O 3 content: 0% or more and 1.5% or less, Gd 2 O 3 content: 0% or more and 2% or less; 6. The optical glass according to claim 1.

7. In mass %, ZnO content: 0% or more and 5% or less, Bi 2 O 3 content: 0% or more and 5% or less, ZrO 2 content: 0% or more and 6% or less, WO 3 content: 0% or more and 3% or less, Sb 2 O 3 content: 0% or more and 0.4% or less; 7. The optical glass according to claim 1.

8. In mass %, The total content of P 2 O 5 and B 2 O 3 (P 2 O 5 +B 2 O 3 ): 28% or more and 43% or less; The optical glass according to any one of claims 1 to 7.

9. In mass %, the ratio of the B 2 O 3 content to the P 2 O 5 content (B 2 O 3 / P 2 O 5 ): 0 or more and 0.24 or less; The optical glass according to any one of claims 1 to 8.

10. The specific gravity (Sg) is 2.8 or more and 3.4 or less. The optical glass according to any one of claims 1 to 9.

11. The value (ΔP g,F ) indicating anomalous dispersion is 0.0190 or more and 0.0320 or less. The optical glass according to any one of claims 1 to 10.

12. When 50 g of the raw material of the optical glass is heated at a temperature of 1100°C or higher and 1250°C or lower, the time until the raw material melts is less than 15 minutes. The optical glass according to any one of claims 1 to 11.

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

14. An optical system including the optical element described in claim 13.

15. An interchangeable lens comprising the optical system described in claim 14.

16. An optical device comprising the optical system described in claim 14.

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