Optical glass, optical element and optical device using optical glass

Abstract

To provide an optical glass which has a unique combination of anomalous dispersibility in a visible range with that in a near-infrared range. Provided is an optical glass containing respective components of SiO.sub.2 from 14 to 26% by mass, B.sub.2O.sub.3 from 9 to 16% by mass, and La.sub.2O.sub.3 from 10 to 42% by mass as essential components, and containing respective components of ZnO, Y.sub.2O.sub.3, ZrO.sub.2, Ta.sub.2O.sub.5, Li.sub.2O, and Na.sub.2O as optional components, and satisfying respective relationships of SiO.sub.2+B.sub.2O.sub.3 from 28 to 36% by mass, ZrO.sub.2+Ta.sub.2O.sub.5 from 6 to 16% by mass, La.sub.2O.sub.3+Y.sub.2O.sub.3+ZnO from 43 to 59% by mass, and Li.sub.2O+Na.sub.2O from 2 to 14% by mass.

Claims

1. An optical glass containing respective components of SiO.sub.2 from 14 to 26% by mass, B.sub.2O.sub.3 from 9 to 16% by mass, and La.sub.2O.sub.3 from 10 to 42% by mass as essential components, and containing respective components of ZnO, Y.sub.2O.sub.3, ZrO.sub.2, Ta.sub.2O.sub.5, Li.sub.2O, and Na.sub.2O as optional components, and satisfying respective relationships of SiO.sub.2+B.sub.2O.sub.3 from 28 to 36% by mass, ZrO.sub.2+Ta.sub.2O.sub.5 from 6 to 16% by mass, La.sub.2O.sub.3+Y.sub.2O.sub.3+ZnO from 43 to 59% by mass, and Li.sub.2O+Na.sub.2O from 2 to 14% by mass.

2. The optical glass according to claim 1, further containing respective components of ZnO from 0% by mass to 45% by mass, Y.sub.2O.sub.3 from 0% by mass to 20% by mass, ZrO.sub.2 from 0% by mass to 7% by mass, Ta.sub.2O.sub.5 from 0% by mass to 15% by mass, Li.sub.2O from 0% by mass to 8% by mass, Na.sub.2O from 0% by mass to 13% by mass, and Sb.sub.2O.sub.3 from 0% by mass to 1% by mass.

3. The optical glass according to claim 2, containing a component of Y.sub.2O.sub.3 from 0% by mass to 5% by mass.

4. The optical glass according to claim 1, wherein the optical glass has a refractive index (n.sub.d) from 1.68 to 1.75, and Abbe number (.sub.d) from 43 to 50.

5. The optical glass according to claim 1, wherein a value (P.sub.c,t) indicating anomalous dispersibility in a near-infrared range is 0.0100 or less.

6. The optical glass according to claim 1, wherein a value (P.sub.g,F) indicating anomalous dispersibility in a short wavelength visible range is 0.0075 or less.

7. The optical glass according to claim 1, wherein a value (P.sub.c,t) indicating anomalous dispersibility in a near-infrared range and a value (P.sub.g,F) indicating anomalous dispersibility in a visible range satisfy a relational expression represented by
P.sub.c,t5.Math.(P.sub.g,F+0.0075).

8. An optical element comprising the optical glass according to claim 1.

9. An optical device comprising the optical element according to claim 8.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a block diagram showing an example of the configuration of a multiphoton microscope including an optical element that uses an optical glass according to one embodiment of the present invention.

(2) FIG. 2 is a perspective view of an imaging device including an optical element that uses an optical glass according to an embodiment of the present invention.

(3) FIG. 3 is a graph obtained by plotting the values of P.sub.g,F and P.sub.c,t for examples.

DESCRIPTION OF EMBODIMENTS

(4) Embodiments of the present invention (hereinafter, referred to as the present embodiment) will be described below. The following embodiments are considered by way of example for explaining the present invention, and not intended to limit the present invention to the following description. The present invention can be modified and carried out appropriately within the scope of the invention.

(5) In addition, in the present specification, unless otherwise specified, the contents of respective components are all considered on a % by mass basis with respect to the total glass mass of the composition in terms of oxide. The composition in terms of oxide herein refers to assuming that all the oxides, complex salts, and the like used as raw materials for glass constituents according to the present embodiment are all decomposed into oxides upon melting, a composition where each component contained in the glass is represented with the total oxide mass regarded as 100% by mass.

(6) The optical glass according to the present embodiment is an optical glass of SiO.sub.2B.sub.2O.sub.3La.sub.2O.sub.3 type. Specifically, the optical glass is adapted to contain respective components of SiO.sub.2: 14 to 26%, B.sub.2O.sub.3: 9 to 16%, La.sub.2O.sub.3: 10 to 42% as essential components, and contains respective components of ZnO, Y.sub.2O.sub.3, ZrO.sub.2, Ta.sub.2O.sub.5, Li.sub.2O, and Na.sub.2O as an optional component. Further, the optical glass is adapted to contain the respective relationships of SiO.sub.2+B.sub.2O.sub.3: 28 to 36%, ZrO.sub.2+Ta.sub.2O.sub.5: 6 to 16%, La.sub.2O.sub.3+Y.sub.2O.sub.3+ZnO: 43 to 59%, and Li.sub.2O+Na.sub.2O: 2 to 14%. As long as these relationships are satisfied, the content of any of the optional components may be 0% by mass. The optical glass according to the present embodiment can be adapted to be an optical glass which has a unique combination of anomalous dispersibility in the visible range with that in the near-infrared range, thereby making it possible to broaden the degree of freedom for optical design than ever before.

(7) Regarding ordinary optical glass, it is known that a substantially linear relationship is established when the Abbe number and the partial dispersion ratio are respectively indicated on the horizontal axis and the vertical axis (normal partial dispersion), and the anomalous dispersibility is expressed by the degree of deviation from the foregoing straight line. The value (P.sub.g,F) indicating the anomalous dispersibility in the visible range can be obtained from the Abbe number (.sub.d) and the partial dispersion ratio (P.sub.g,F) in the visible range, based on the method mentioned in Examples as described later. Similarly, the value (P.sub.c,t) indicating the anomalous dispersibility in the near-infrared range can be obtained from the Abbe number (.sub.d) and the partial dispersion ratio (P.sub.c,t) in the near-infrared range, based on the method mentioned in Examples as described later. In general, as one of the value (P.sub.g,F) indicating the anomalous dispersibility in the visible range and the value (P.sub.c,t) indicating the anomalous dispersibility in the near-infrared range is larger, the other is smaller. However, in the optical glass according to the present embodiment, the value (P.sub.g,F) indicating the anomalous dispersibility in the visible range and the value (P.sub.c,t) indicating the anomalous dispersibility in the near-infrared range can be both small values. Such optical glass can be suitably used as a lens for correcting the chromatic aberration between the visible range and the near-infrared range in the optical system of the optical device. It is to be noted that in this specification, the fact that the value (P.sub.g,F) indicating the anomalous dispersibility in the visible range and the value (P.sub.c,t) indicating the anomalous dispersibility in the near-infrared range are both small values is described as a unique combination of anomalous dispersibility in the visible range with that in a near-infrared range.

(8) Details of compositions and properties will be described for each component of the optical glass according to the present embodiment.

(9) SiO.sub.2 is an essential component as a glass-forming oxide, which is effective for lowering the refractive index. However, the addition thereof in large amounts will increase P.sub.g,F. From the foregoing viewpoint, the content of SiO.sub.2 is 14 to 26%, preferably 14 to 24%, more preferably 14 to 22%.

(10) B.sub.2O.sub.3 is an essential component as a glass-forming oxide, which improves the devitrification resistance. In addition, B.sub.2O.sub.3 is effective for lowering the refractive index, P.sub.g,F. From the foregoing viewpoint, the content of B.sub.2O.sub.3 is 9 to 16%, preferably 10 to 16%, more preferably 11 to 16%.

(11) La.sub.2O.sub.3 is an essential component for achieving desired refractive index and Abbe number. However, the addition thereof in large amounts will decreases the devitrification resistance, thereby increasing P.sub.g,F and increasing n.sub.d. From the foregoing viewpoint, the content of La.sub.2O.sub.3 is 10 to 42%, preferably 13 to 39%, more preferably 16 to 36%.

(12) ZnO is an optional component which is effective for achieving desired refractive index and Abbe number. However, the addition thereof in large amounts will decreases the devitrification resistance, thereby increasing P.sub.g,F and slightly increasing n.sub.d. From the foregoing viewpoint, the content of ZnO is preferably 0 to 45%, more preferably 3 to 40%, further preferably 6 to 35%.

(13) Y.sub.2O.sub.3 is an optional component which is effective for achieving desired refractive index and Abbe number. However, the addition thereof in large amounts will decreases the devitrification resistance, thereby increasing P.sub.g,F and increasing n.sub.d. From the foregoing viewpoint, the content of Y.sub.2O.sub.3 is preferably 0 to 20%, more preferably 0 to 10%, further preferably 0 to 5%.

(14) ZrO.sub.2 is an optional component which is effective for lowering P.sub.g,F. However, the addition thereof in large amounts will significantly decrease the devitrification resistance, and also greatly increase n.sub.d. From the foregoing viewpoint, the content of ZrO.sub.2 is preferably 0 to 7%, more preferably 1 to 7%, further preferably 2 to 7%.

(15) Ta.sub.2O.sub.5 is an optional component which is effective for lowering P.sub.g,F, and also enhancing the devitrification resistance. However, the addition thereof in large amounts will greatly increase n.sub.d. From the foregoing viewpoint, the content of Ta.sub.2O.sub.5 is preferably 0 to 15%, more preferably 0 to 13%, further preferably 0 to 11%.

(16) Li.sub.2O is an optional component which is effective for lowering P.sub.g,F and n.sub.d. However, the addition thereof in large amounts will significantly decrease the devitrification resistance. From the foregoing viewpoint, the content of Li.sub.2O is preferably 0 to 8%, more preferably 0 to 6%.

(17) Na.sub.2O is an optional component which is effective for lowering P.sub.g,F and n.sub.d. However, the addition thereof in large amounts will significantly decrease the devitrification resistance. From the foregoing viewpoint, the content of Na.sub.2O is preferably 0 to 13%, more preferably 0 to 10%.

(18) Sb.sub.2O.sub.3 is an optional component which is effective for clarifying and homogenizing the glass. Therefore, Sb.sub.2O.sub.3 may be added as a defoaming agent. From the foregoing viewpoint, the content of Sb.sub.2O.sub.3 is preferably 0 to 1%.

(19) As a combination of the optional components mentioned above, it is preferable to further contain respective components of ZnO: 0 to 45%, Y.sub.2O.sub.3: 0 to 20%, ZrO.sub.2: 0 to 7%, Ta.sub.2O.sub.5: 0 to 15%, Li.sub.2O: 0 to 8%, Na.sub.2O: 0 to 13%, and Sb.sub.2O.sub.3: 0 to 1%.

(20) In order to improve the devitrification resistance of the optical glass, it is desirable to introduce sufficient amounts of B.sub.2O.sub.3 and SiO.sub.2, but when the amounts exceed a certain amount, P.sub.g,F will increase, thereby failing to achieve desired anomalous dispersibility. From the foregoing viewpoint, the sum of the SiO.sub.2 and B.sub.2O.sub.3 contents (abbreviated as SiO.sub.2+B.sub.2O.sub.3, the same applies hereinafter) is 28 to 36%, preferably 28 to 35%, more preferably 28 to 34%.

(21) In order to achieve a desired constant value/anomalous dispersibility, it is desirable to introduce ZrO.sub.2 and Ta.sub.2O.sub.5 in sufficient amounts. From the foregoing viewpoint, ZrO.sub.2+Ta.sub.2O.sub.5 is 6 to 16%, preferably 7 to 16%, more preferably 8 to 16%.

(22) It is desirable to introduce La.sub.2O.sub.3, Y.sub.2O.sub.3, and ZnO in sufficient amounts in order to achieve a desired constant value/anomalous dispersibility, but the excessive introduction thereof will make the glass more likely to devitrify easily. From the foregoing viewpoint, La.sub.2O.sub.3+Y.sub.2O.sub.3+ZnO is 43 to 59%, preferably 43 to 58%, more preferably 43 to 56%.

(23) When the sum of Li.sub.2O and Na.sub.2O exceeds a certain amount, the glass stability will be impaired. From the foregoing viewpoint, Li.sub.2O+Na.sub.2O is 2 to 14%, preferably 2 to 12%, more preferably 2 to 10%.

(24) Without limiting to the components mentioned above, any other optional components may be further added within a scope that does not interfere with achieving the object of the optical glass according to the present embodiment.

(25) Next, physical property values of the optical glass according to the present embodiment will be described.

(26) The optical glass according to the present embodiment is preferably related to a medium refractive index/medium dispersion region. From the foregoing viewpoint, the refractive index (n.sub.d) of the optical glass according to the present embodiment is preferably 1.68 to 1.75, more preferably 1.68 to 1.745, and further preferably 1.68 to 1.74. The Abbe number (.sub.d) of the optical glass according to the present embodiment is preferably 43 to 50, more preferably 43 to 49, and further preferably 43 to 48. It is particularly preferable for both the refractive index (n.sub.d) and the Abbe number (.sub.d) to satisfy the ranges mentioned above.

(27) From the viewpoint of the achromatic effect in the near-infrared range and the visible range, the value (P.sub.c,t) indicating anomalous dispersibility in the near-infrared range and the value (P.sub.g,F) indicating anomalous dispersibility in the visible range are each preferably small. From the foregoing viewpoint, the value (P.sub.c,t) indicating anomalous dispersibility in the near-infrared range is preferably 0.0100 or less, more preferably 0.0070 or less, further preferably 0.0050 or less. The value (P.sub.g,F) indicating anomalous dispersibility in the visible range is preferably 0.0075 or less, more preferably 0.0078 or less, further preferably 0.0081 or less. Furthermore, it is particularly preferable for both P.sub.c,t and P.sub.g,F to satisfy the ranges mentioned above.

(28) From the viewpoint mentioned above, it is preferable for P.sub.c,t and P.sub.g,F to satisfy the following relational expression.
P.sub.c,t5.Math.(P.sub.g,F+0.0075)

(29) Even when this relational expression is satisfied, P.sub.c,t is preferably 0.0100 or less, and P.sub.g,F is preferably 0.0075 or less.

(30) As described above, the optical glass according to the present embodiment is an optical glass which has unique anomalous dispersibility in the near-infrared range and the visible range. For example, in an optical system that uses such optical glass in combination with other optical glass, it is possible to correct the chromatic aberration between the near-infrared range and the visible range, thereby making it possible to broaden the degree of freedom for optical design than ever before.

(31) The optical glass according to the present embodiment is suitable as an optical element such as a lens of an optical device such as a camera or a microscope. As an optical device, above all, a multiphoton microscope is particularly suitable.

Multiphoton Microscope

(32) FIG. 1 is a block diagram illustrating an example of the configuration of a multiphoton microscope 1 according to an embodiment of the present invention. The multiphoton microscope 1 includes, as optical elements, an objective lens 106, a condenser lens 108, and an imaging lens 110. Hereinafter, the optical system of the multiphoton microscope 1 will be mainly described.

(33) The pulsed laser device 101 emits ultrashort pulsed light that has a pulse width of femtoseconds (for example, 100 femtoseconds), for example, with a near-infrared wavelength (about 1000 nm). The ultrashort pulsed light immediately after being emitted from the pulsed laser device 101 is generally linearly polarized light polarized in a predetermined direction.

(34) The pulse splitting device 102 splits the ultrashort pulsed light, and emits the ultrashort pulsed light at the increased repetition frequency thereof.

(35) The beam adjusting unit 103 has the function of adjusting the beam diameter of the ultrashort pulsed light incident from the pulse splitting device 102 in accordance with the pupil diameter of the objective lens 106, the function of adjusting the convergence and divergence angles of ultrashort pulsed light in order to correct the axial chromatic aberration (focus difference) between the wavelength of multiphoton excitation light emitted from a sample S and the wavelength of the ultrashort pulsed light, the pre-chirping function (group velocity dispersion compensation function) of providing reverse group velocity dispersion to the ultrashort pulsed light in order to correct the increase in the pulse width of the ultrashort pulsed light due to group velocity dispersion while passing through the optical system, and the like.

(36) The repetition frequency of the ultrashort pulsed light emitted from the pulsed laser device 101 is increased by the pulse splitting device 102, and the light is adjusted as described above by the beam adjusting unit 103. Then, the ultrashort pulsed light emitted from the beam adjusting unit 103 is reflected toward the dichroic mirror 105 by the dichroic mirror 104 to pass through the dichroic mirror 105, and focused by the objective lens 106 to irradiate the sample S. In this regard, the observation surface of the sample S may be scanned with the ultrashort pulsed light by using a scanning means (not shown).

(37) For example, in the case of fluorescence observation of the sample S, a fluorescent dye with which the sample S is dyed is multiphoton-excited in a region of the sample S irradiated with the ultrashort pulse light and in the vicinity thereof, thereby producing fluorescence with a shorter wavelength than the ultrashort pulsed light as an infrared wavelength (hereinafter referred to as observation light).

(38) The observation light emitted from the sample S in a direction toward the objective lens 106 is collimated by the objective lens 106, and depending on the wavelength, reflected by the dichroic mirror 105 or transmitted through the dichroic mirror 105.

(39) The observation light reflected by the dichroic mirror 105 enters the fluorescence detection unit 107. The fluorescence detection unit 107 composed of, for example, a barrier filter, a PMT (photo multiplier tube), and the like, receives the observation light reflected by the dichroic mirror 105, and outputs an electric signal corresponding to the amount of light. In addition, in accordance with scanning the observation surface of the sample S with the ultrashort pulse light, the fluorescence detection unit 107 detects observation light over the observation surface of the sample S.

(40) On the other hand, the observation light transmitted through the dichroic mirror 105 is subjected to descanning by a scanning means (not shown), transmitted through the dichroic mirror 104, condensed by the condenser lens 108, transmitted through a pinhole 109 provided at a position substantially conjugated with the focal position of the objective lens 106, and passed through the imaging lens 110 to enter the fluorescence detection unit 111. The fluorescence detection unit 111 composed of, for example, a barrier filter, PMT, and the like, receives the observation light imaged on the light-receiving surface of the fluorescence detection unit 111 by the imaging lens 110, and outputs an electric signal corresponding to the amount of light. In addition, in accordance with scanning the observation surface of the sample S with the ultrashort pulse light, the fluorescence detection unit 111 detects observation light over the observation surface of the sample S.

(41) It is to be noted that the dichroic mirror 105 may be deviated from the optical path such that the observation light emitted from the sample S in the direction toward the objective lens 106 is all detected by the fluorescence detection unit 111.

(42) In addition, the observation light emitted from the sample S in the direction opposite to the objective lens 106 is reflected by the dichroic mirror 112 to enter the fluorescence detection unit 113. The fluorescence detection unit 113 composed of, for example, a barrier filter, a PMT, and the like, receives the observation light reflected by the dichroic mirror 112, and outputs an electric signal corresponding to the amount of light. In addition, in accordance with scanning the observation surface of the sample S with the ultrashort pulse light, the fluorescence detection unit 113 detects observation light over the observation surface of the sample S.

(43) The electric signals respectively output from the fluorescence detection units 107, 111, 113 are input to, for example, a computer (not shown), and the computer can generate an observation image based on the input electric signals, and display the generated observation image and store the data of the observation image.

Imaging Device

(44) The optical element using the optical glass according to the present embodiment can also be used for an imaging device. FIG. 2 shows a perspective view of an imaging device including an optical element that uses an optical glass according to an embodiment of the present invention. The imaging device 2 (optical device) includes a lens 203 (optical element) with the optical glass according to the present embodiment as a base material.

(45) The imaging device 2 is a so-called digital single-lens reflex camera, and a lens barrel 202 is detachably attached to a lens mount (not shown) of a camera body 201. Further, light passed through the lens 203 of the lens barrel 202 is imaged on a sensor chip (solid-state imaging element) 204 of a multichip module 206 disposed 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 multichip module 206 is, for example, a COG (Chip On Glass) type module with the sensor chip 204 bare chip-mounted on a glass substrate 205.

(46) It is to be noted that the optical device is not limited to such an imaging device, but intended to encompass a wide range of devices such as a projector. The optical element is also not limited to any lens but intended to encompass a wide range of elements such as a prism.

EXAMPLES

(47) Next, the following examples and comparative examples will be described, but the present invention is not to be considered limited by the following examples in any way. Tables 2 to 8 show the composition, refractive index (n.sub.d), Abbe number (.sub.d), partial dispersion ratios (P.sub.g,F and P.sub.c,t), values (P.sub.g,F, P.sub.c,t) indicating anomalous dispersibility, and value of P.sub.c,t+5.Math.(P.sub.g, F+0.0075), for optical glass according to each example and each comparative example.

(48) <Preparation of Optical Glass>

(49) The optical glass according to each example and each comparative example was prepared by the following procedure. First, glass raw materials such as oxides, hydroxides, carbonates, sulfates, and nitrates were weighed so as to provide the chemical compositions (% by mass) listed in each table. Next, the weighed raw materials were mixed and put into a platinum crucible, and melted at a temperature of 1200 to 1400 C. for about 1 hour, for stirring and homogenization. Thereafter, after bubbles were removed, each sample was obtained by lowering the temperature, casting into a mold, slow cooling, and molding.

Physical Property Measurement of Optical Glass

(50) The refractive indices of the respective samples for d-line (587.562 nm), g-line (435.835 nm), F-line (486.133 nm), C-line (656.273 nm) and t-line (1013.98 nm) were measured with the use of an accurate refractive index measurement instrument (Spectro Master HR from TRIOPTICS). The Abbe number (.sub.d), partial dispersion ratios (P.sub.g,F, P.sub.c,t), P.sub.g,F, P.sub.c,t, and P.sub.c,t+5(P.sub.g,F+0.0075) for the optical glass were calculated from the obtained actual measurement values. It is to be noted that the value of the refractive index used for the calculation was obtained down to seven places of decimals after the decimal point. It is to be noted that the term denitrification in Table 8 indicates a sample with glass partially or entirely devitrified in the manufacture of the glass. The samples were not subjected to the refractive-index measurement, because it is not possible to use the samples as optical glass.

(51) The value (P.sub.g,F) indicating anomalous dispersibility in the visible range and the value (P.sub.c,t) indicating anomalous dispersibility in the near-infrared range were calculated by the following calculation method for the value (P.sub.x,y) indicating anomalous dispersibility.

(52) (1) Creation of Reference Line

(53) First, as normal partial dispersion glass, two vitreous types of glass NSL7 and PBM2 (the names of vitreous types both manufactured by OHARA Co., Ltd., both) with the Abbe numbers (.sub.d) and partial dispersion ratios shown in Table 1 were selected as reference materials. Then, for each glass, the Abbe number (.sub.d) was indicated on the horizontal axis, the partial dispersion ratio (P.sub.x,y) was indicated on the vertical axis, and a straight line connecting two points corresponding to the two reference materials was regarded as a reference line (Creation of Reference Line). It is to be noted that the partial dispersion ratio (P.sub.x,y) refers to the ratio of (nx-ny) to the principal dispersion (nF-nC). The types of emission lines are put in x and y.

(54) TABLE-US-00001 TABLE 1 NSL7 PBM2 .sub.d 60.49 36.26 P.sub.g, F 0.5436 0.5828 P.sub.c, t 0.8305 0.7168

(55) (2) Calculation of Value Indicating Anomalous Dispersibility

(56) Next, values corresponding to the optical glass according to each example and each comparative example were plotted on the graph with the Abbe number (.sub.d) on the horizontal axis and the partial dispersion ratio (P.sub.x,y) on the vertical axis, and the difference between the point on the reference line, corresponding to the Abbe number (.sub.d) for the vitreous type mentioned above, and the value (P.sub.x,y) on the vertical axis thereof was calculated as a value (P.sub.x,y) indicating anomalous dispersibility. It is to be noted that the partial dispersion ratio above the reference line is referred to as a value indicating positive anomalous dispersibility, and the ratio below the straight line is referred to as a value indicating a negative anomalous dispersibility.

(57) (3) Calculation of Value Indicating Anomalous Dispersibility in Visible Range and Value Indicating Anomalous Dispersibility in Near-Infrared Range

(58) Through the use of the above approach, P.sub.g,F was calculated as an index of anomalous dispersibility in the visible range, and P.sub.c,t was calculated as an index of anomalous dispersibility in the near-infrared range. The reference line equation in the visible range and the reference line equation in the near-infrared range are as follows. This anomalous dispersibility is expressed as a degree of deviation from the normal partial dispersion glass.
P.sub.g,F=0.641462+(0.0016178).sub.d(i)
P.sub.c,t=0.546649+0.00469253.sub.d(ii)

(59) More specifically, the value (P.sub.g,F) indicating anomalous dispersibility in the visible region refers to the difference between the point on the reference line, corresponding to the Abbe number (.sub.d), and the partial dispersion ratio (P.sub.g F), with the above-mentioned formula (i) as a reference line equation. The value (P.sub.c,t) indicating anomalous dispersibility in the near-infrared range refers to the difference between the point on the reference line, corresponding to the Abbe number (.sub.d), and the partial dispersion ratio (P.sub.c,t), with the above-mentioned formula (ii) as a reference line equation.

(60) It has been also determined whether the value (P.sub.g,F) indicating anomalous dispersibility in the visible range and the value (P.sub.c,t) indicating anomalous dispersibility in the near-infrared range satisfy the relationship represented by the inequality P.sub.c,t5.Math.(P.sub.g,F+0.0075) or not. More specifically, if the value of P.sub.c,t+5.Math.(P.sub.g,F+0.0075) is zero or negative, the above-mentioned inequality is evaluated as being satisfied, and if the value is positive, the inequality is evaluated as being unsatisfied.

(61) Tables 2 to 8 show therein the compositions and evaluation results for each example and each comparative example. In addition, FIG. 3 shows therein a graph obtained by plotting the values of P.sub.g,F and P.sub.c,t for each example and each comparative example.

(62) TABLE-US-00002 TABLE 2 EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 4 EXAMPLE 5 EXAMPLE 6 EXAMPLE 7 SiO.sub.2 25.37 16.72 17.64 14.66 16.86 16.07 19.03 B.sub.2O.sub.3 9.81 15.85 14.48 13.86 15.08 13.19 15.54 La.sub.2O.sub.3 32.16 32.47 38.58 13.31 22.77 30.12 36.99 Y.sub.2O.sub.3 4.28 4.33 7.57 0.00 19.37 4.02 4.93 ZnO 15.34 15.49 0.00 42.02 10.63 14.36 13.75 ZrO.sub.2 4.04 6.06 6.16 5.14 6.12 0.00 6.89 Ta.sub.2O.sub.5 4.21 4.25 8.77 5.34 4.29 14.27 0.00 Li.sub.2O 2.87 2.90 2.95 2.45 2.93 2.69 2.67 Na.sub.2O 1.77 1.78 3.69 3.07 1.80 5.13 0.00 Sb.sub.2O.sub.3 0.15 0.15 0.16 0.15 0.15 0.15 0.20 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 SiO.sub.2 + B.sub.2O.sub.3 35.19 32.56 32.11 28.53 31.94 29.26 34.57 ZrO.sub.2 + Ta.sub.2O.sub.5 8.25 10.32 14.94 10.48 10.41 14.27 6.89 La.sub.2O.sub.3 + 51.78 52.29 46.15 55.33 52.77 48.51 55.67 Y.sub.2O.sub.3 + ZnO Li.sub.2O + Na.sub.2O 4.64 4.68 6.64 5.52 4.73 7.81 2.67 n.sub.d 1.71433 1.73173 1.73528 1.71392 1.73673 1.72241 1.73634 .sub.d 48.53 47.78 47.45 44.20 48.13 45.82 49.23 P.sub.g, F 0.5550 0.5551 0.5554 0.5619 0.5547 0.5590 0.5530 P.sub.g, F 0.0080 0.0091 0.0093 0.0081 0.0089 0.0084 0.0088 P.sub.C, t 0.7734 0.7753 0.7757 0.7548 0.7759 0.7638 0.7809 P.sub.C, t 0.0010 0.0044 0.0064 0.0008 0.0034 0.0021 0.0032 P.sub.C, t + 5 0.0034 0.0035 0.0027 0.0022 0.0037 0.0022 0.0033 (P.sub.g, F + 0.0075)

(63) TABLE-US-00003 TABLE 3 EXAMPLE 8 EXAMPLE 9 EXAMPLE 10 EXAMPLE 11 EXAMPLE 12 EXAMPLE 13 EXAMPLE 14 SiO.sub.2 17.34 16.35 16.76 16.07 22.22 19.48 16.60 B.sub.2O.sub.3 15.50 14.61 15.00 13.80 11.66 13.74 13.63 La.sub.2O.sub.3 33.69 31.76 32.60 25.36 31.84 32.16 34.32 Y.sub.2O.sub.3 4.49 4.23 4.34 4.90 4.24 4.28 4.15 ZnO 16.07 15.15 15.55 13.38 15.19 15.34 10.84 ZrO.sub.2 2.18 3.99 4.10 4.97 5.95 6.00 5.80 Ta.sub.2O.sub.5 4.41 6.07 5.25 7.51 4.17 4.21 8.26 Li.sub.2O 0.00 7.70 6.25 1.25 2.84 2.87 2.78 Na.sub.2O 6.17 0.00 0.00 12.58 1.75 1.77 3.47 Sb.sub.2O.sub.3 0.15 0.14 0.15 0.18 0.14 0.15 0.15 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 SiO.sub.2 + B.sub.2O.sub.3 32.84 30.95 31.77 29.88 33.87 33.22 30.22 ZrO.sub.2 + Ta.sub.2O.sub.5 6.59 10.06 9.35 12.49 10.12 10.22 14.06 La.sub.2O.sub.3 + 54.25 51.14 52.49 43.63 51.27 51.78 49.31 Y.sub.2O.sub.3 + ZnO Li.sub.2O + Na.sub.2O 6.17 7.70 6.25 13.82 4.59 4.64 6.25 n.sub.d 1.70695 1.72522 1.72912 1.68278 1.72446 1.72806 1.72132 .sub.d 48.17 47.47 47.85 45.59 47.88 47.84 45.00 P.sub.g, F 0.5553 0.5556 0.5551 0.5587 0.5551 0.5552 0.5597 P.sub.g, F 0.0082 0.0090 0.0090 0.0090 0.0089 0.0089 0.0090 P.sub.C, t 0.7737 0.7726 0.7746 0.7627 0.7725 0.7740 0.7608 P.sub.C, t 0.0010 0.0032 0.0034 0.0021 0.0012 0.0028 0.0030 P.sub.C, t + 5 0.0026 0.0044 0.0041 0.0056 0.0056 0.0039 0.0045 (P.sub.g, F + 0.0075)

(64) TABLE-US-00004 TABLE 4 EXAMPLE 15 EXAMPLE 16 EXAMPLE 17 EXAMPLE 18 EXAMPLE 19 EXAMPLE 20 EXAMPLE 21 SiO.sub.2 18.94 15.26 15.68 15.00 16.83 16.40 17.01 B.sub.2O.sub.3 15.48 14.43 14.79 14.18 15.06 13.47 15.22 La.sub.2O.sub.3 33.40 28.62 22.56 21.62 32.24 30.76 33.08 Y.sub.2O.sub.3 4.91 3.82 3.91 3.75 4.99 4.11 4.41 ZnO 17.55 21.02 25.81 28.93 15.61 14.67 15.78 ZrO.sub.2 6.86 5.34 5.48 5.26 6.11 3.34 6.18 Ta.sub.2O.sub.5 0.00 5.60 5.72 5.46 4.29 10.31 4.33 Li.sub.2O 2.66 2.56 2.62 2.51 2.92 2.75 2.02 Na.sub.2O 0.00 3.20 3.28 3.14 1.80 4.04 1.82 Sb.sub.2O.sub.3 0.20 0.15 0.15 0.15 0.15 0.15 0.15 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 SiO.sub.2 + B.sub.2O.sub.3 34.42 29.70 30.46 29.18 31.89 29.88 32.24 ZrO.sub.2 + Ta.sub.2O.sub.5 6.86 10.94 11.20 10.72 10.40 13.65 10.51 La.sub.2O.sub.3 + 55.86 53.46 52.28 54.29 52.85 49.53 53.26 Y.sub.2O.sub.3 + ZnO Li.sub.2O + Na.sub.2O 2.66 5.75 5.90 5.65 4.72 6.78 3.84 n.sub.d 1.73294 1.73048 1.72058 1.72439 1.72431 1.72828 1.73681 .sub.d 48.91 46.25 46.06 45.52 47.73 46.12 47.54 P.sub.g, F 0.5536 0.5579 0.5582 0.5593 0.5554 0.5581 0.5558 P.sub.g, F 0.0088 0.0088 0.0087 0.0086 0.0088 0.0088 0.0088 P.sub.C, t 0.7791 0.7653 0.7655 0.7614 0.7732 0.7657 0.7731 P.sub.C, t 0.0030 0.0017 0.0027 0.0011 0.0026 0.0026 0.0033 P.sub.C, t + 5 0.0033 0.0046 0.0034 0.0042 0.0040 0.0038 0.0029 (P.sub.g, F + 0.0075)

(65) TABLE-US-00005 TABLE 5 EXAMPLE 22 EXAMPLE 23 EXAMPLE 24 EXAMPLE 25 EXAMPLE 26 EXAMPLE 27 EXAMPLE 28 SiO.sub.2 17.16 17.66 17.40 14.84 16.86 16.86 17.10 B.sub.2O.sub.3 15.34 15.80 15.56 13.29 15.08 15.08 14.03 La.sub.2O.sub.3 33.35 34.34 33.81 28.87 27.77 22.77 35.33 Y.sub.2O.sub.3 4.44 4.58 4.50 3.86 9.37 14.37 4.25 ZnO 15.91 16.37 16.11 13.77 15.63 15.63 8.24 ZrO.sub.2 4.19 6.40 6.30 4.22 6.12 6.12 5.97 Ta.sub.2O.sub.5 4.37 1.11 2.18 11.72 4.29 4.29 8.50 Li.sub.2O 5.09 3.07 3.02 2.58 2.93 2.93 2.86 Na.sub.2O 0.00 0.47 0.92 6.70 1.80 1.80 3.57 Sb.sub.2O.sub.3 0.15 0.20 0.20 0.15 0.15 0.15 0.15 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 SiO.sub.2 + B.sub.2O.sub.3 32.50 33.47 32.95 28.14 31.94 31.94 31.12 ZrO.sub.2 + Ta.sub.2O.sub.5 8.56 7.51 8.48 15.94 10.41 10.41 14.47 La.sub.2O.sub.3 + 53.70 55.29 54.43 46.50 52.77 52.77 47.82 Y.sub.2O.sub.3 + ZnO Li.sub.2O + Na.sub.2O 5.09 3.53 3.94 9.28 4.73 4.73 6.43 n.sub.d 1.73165 1.73448 1.73428 1.73710 1.73332 1.73268 1.73438 .sub.d 48.17 48.64 48.27 46.40 47.62 47.68 46.76 P.sub.g, F 0.5548 0.5539 0.5545 0.5573 0.5555 0.5552 0.5565 P.sub.g, F 0.0087 0.0089 0.0089 0.0091 0.0089 0.0091 0.0093 P.sub.C, t 0.7759 0.7781 0.7765 0.7678 0.7736 0.7739 0.7708 P.sub.C, t 0.0032 0.0033 0.0033 0.0034 0.0035 0.0035 0.0048 P.sub.C, t + 5 0.0029 0.0036 0.0038 0.0047 0.0037 0.0044 0.0044 (P.sub.g, F + 0.0075)

(66) TABLE-US-00006 TABLE 6 EXAMPLE 29 EXAMPLE 30 EXAMPLE 31 EXAMPLE 32 EXAMPLE 33 EXAMPLE 34 EXAMPLE 35 SiO.sub.2 17.64 14.89 14.66 14.66 16.63 17.14 16.39 B.sub.2O.sub.3 14.48 14.06 13.86 13.86 14.26 14.72 14.07 La.sub.2O.sub.3 36.46 21.44 21.13 16.24 26.20 27.04 25.84 Y.sub.2O.sub.3 4.38 0.99 0.00 0.00 5.06 5.22 4.99 ZnO 5.31 32.23 34.20 39.09 13.82 14.27 13.63 ZrO.sub.2 6.16 5.22 5.14 5.14 5.14 5.87 5.07 Ta.sub.2O.sub.5 8.77 5.42 5.34 5.34 7.76 5.97 7.66 Li.sub.2O 2.95 2.49 2.45 2.45 1.29 1.33 1.27 Na.sub.2O 3.69 3.11 3.07 3.07 9.66 8.25 10.90 Sb.sub.2O.sub.3 0.16 0.15 0.15 0.15 0.18 0.19 0.18 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 SiO.sub.2 + B.sub.2O.sub.3 32.11 28.95 28.53 28.53 30.88 31.87 30.46 ZrO.sub.2 + Ta.sub.2O.sub.5 14.94 10.63 10.48 10.48 12.90 11.84 12.72 La.sub.2O.sub.3 + 46.15 54.67 55.33 55.33 45.09 46.53 44.47 Y.sub.2O.sub.3 + ZnO Li.sub.2O + Na.sub.2O 6.64 5.60 5.52 5.52 10.95 9.58 12.17 n.sub.d 1.73110 1.72270 1.72312 1.71731 1.69522 1.69921 1.68983 .sub.d 47.14 45.16 44.85 44.45 46.07 46.68 45.87 P.sub.g, F 0.5559 0.5600 0.5606 0.5613 0.5581 0.5570 0.5583 P.sub.g, F 0.0093 0.0084 0.0083 0.0082 0.0089 0.0089 0.0090 P.sub.C, t 0.7741 0.7596 0.7575 0.7559 0.7663 0.7696 0.7646 P.sub.C, t 0.0063 0.0010 0.0004 0.0006 0.0034 0.0039 0.0027 P.sub.C, t + 5 0.0029 0.0036 0.0036 0.0031 0.0034 0.0031 0.0048 (P.sub.g, F + 0.0075)

(67) TABLE-US-00007 TABLE 7 EXAMPLE 36 EXAMPLE 37 EXAMPLE 38 EXAMPLE 39 SiO.sub.2 16.26 15.91 14.66 16.79 B.sub.2O.sub.3 13.95 13.65 13.86 15.67 La.sub.2O.sub.3 25.63 32.07 10.38 41.78 Y.sub.2O.sub.3 4.95 0.00 0.00 0.00 ZnO 13.52 13.23 44.95 17.12 ZrO.sub.2 5.02 4.92 5.14 6.09 Ta.sub.2O.sub.5 7.60 7.43 5.34 0.00 Li.sub.2O 1.26 1.23 2.45 2.36 Na.sub.2O 11.63 11.38 3.07 0.00 Sb.sub.2O.sub.3 0.18 0.18 0.15 0.19 Total 100.00 100.00 100.00 100.00 SiO.sub.2 + B.sub.2O.sub.3 30.21 29.56 28.53 32.47 ZrO.sub.2 + Ta.sub.2O.sub.5 12.62 12.35 10.48 6.09 La.sub.2O.sub.3 + 44.11 45.30 55.33 58.90 Y.sub.2O.sub.3 + ZnO Li.sub.2O + Na.sub.2O 12.89 12.61 5.52 2.36 n.sub.d 1.68680 1.69227 1.7112 1.7465 .sub.d 45.74 45.55 43.87 48.50 P.sub.g, F 0.5586 0.5589 0.5625 0.5543 P.sub.g, F 0.0089 0.0088 0.0080 0.0087 P.sub.c, t 0.7637 0.7616 0.7532 0.7750 P.sub.c, t 0.0023 0.0012 0.0007 0.0008 P.sub.c, t + 5 0.0046 0.0054 0.00173 0.00511 (P.sub.g, F + 0.0075)

(68) TABLE-US-00008 TABLE 8 COMPARATIVE COMPARATIVE COMPARATIVE COMPARATIVE COMPARATIVE EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 4 EXAMPLE 5 SiO.sub.2 18.35 13.48 27.16 15.90 15.74 B.sub.2O.sub.3 7.62 15.74 11.79 15.01 13.51 La.sub.2O.sub.3 35.65 43.79 26.92 30.91 24.82 Y.sub.2O.sub.3 4.75 0.00 3.59 0.00 4.79 ZnO 17.00 17.94 12.84 16.21 13.10 ZrO.sub.2 6.66 6.38 5.02 0.00 4.87 Ta.sub.2O.sub.5 4.67 0.00 7.14 19.56 7.36 Li.sub.2O 3.18 2.47 2.40 2.23 1.22 Na.sub.2O 1.96 0.00 3.01 0.00 14.42 Sb.sub.2O.sub.3 0.16 0.20 0.13 0.18 0.17 Total 100.00 100.00 100.00 100.00 100.00 SiO.sub.2 + B.sub.2O.sub.3 25.97 29.23 38.94 30.92 29.25 ZrO.sub.2 + Ta.sub.2O.sub.5 11.33 6.38 12.17 19.56 12.22 La.sub.2O.sub.3 + 57.40 61.73 43.35 47.12 42.71 Y.sub.2O.sub.3 + ZnO Li.sub.2O + Na.sub.2O 5.14 2.47 5.41 2.23 15.64 n.sub.d DEVITRIFICATION DEVITRIFICATION 1.6917 1.7513 DEVITRIFICATION .sub.d DEVITRIFICATION DEVITRIFICATION 48.72 44.90 DEVITRIFICATION P.sub.g, F DEVITRIFICATION DEVITRIFICATION 0.5541 0.5600 DEVITRIFICATION P.sub.g, F DEVITRIFICATION DEVITRIFICATION 0.0085 0.0089 DEVITRIFICATION P.sub.c, t DEVITRIFICATION DEVITRIFICATION 0.7817 0.7671 DEVITRIFICATION P.sub.c, t DEVITRIFICATION DEVITRIFICATION 0.0065 0.0097 DEVITRIFICATION P.sub.c, t + 5 DEVITRIFICATION DEVITRIFICATION 0.00124 0.00291 DEVITRIFICATION (P.sub.g, F + 0.0075)

(69) It has been confirmed that the optical glass according to each example has small values indicating anomalous dispersibility in the visible range and the near-infrared range. On the other hand, it was not possible to use, as optical glass, Comparative Examples 1, 2 and 5, because the obtained glass was partially or entirely devitrified. Comparative Example 3, with the large P.sub.c,t, failed to satisfy the relational expression of P.sub.c,t5.Math.(P.sub.g,F+0.0075). Comparative Example 4, with the large n.sub.d and P.sub.c,t, failed to satisfy the relational expression of P.sub.c,t5.Math.(P.sub.g,F+0.0075). It is to be noted that, in FIG. 3, an auxiliary line indicating P.sub.c,t=5.Math.(P.sub.g,F+0.0075) is shown for reference.

REFERENCE SIGNS LIST

(70) 1 Multiphoton microscope

(71) 101 Pulsed laser device

(72) 102 Pulse splitting device

(73) 103 Beam adjusting unit

(74) 104, 105, 112 Dichroic mirror

(75) 106 Objective lens

(76) 107, 111, 113 Fluorescence detection unit

(77) 108 Condenser lens

(78) 109 Pinhole

(79) 110 Imaging lens

(80) S Sample

(81) 2 Imaging device

(82) 201 Camera body

(83) 202 Lens barrel

(84) 203 Lens

(85) 204 Sensor chip

(86) 205 Glass substrate

(87) 206 Multichip module