Device and method for quickly measuring the refractive index of optical glass

Abstract

A device and method for rapidly measuring the refractive index of optical glass, wherein a laser light source is mounted on an optical platform, and a fixed platform, a mobile measuring platform, and a shearing interferometer are sequentially mounted along the laser emission direction, wherein the fixed platform is provided with an optical glass plate with a known refractive index, and the mobile measuring platform is provided with a collimating lens. The laser beam emitted by the laser light source passes through the collimating lens, and after the mobile measuring platform is adjusted to collimate the laser beam passing through the collimating lens, the first position X0 of the collimating lens is recorded; a fixed platform with an optical glass with a known refractive index is added, and the laser beam emitted by the laser light source passes through the optical glass plate and the collimating lens, and after the mobile measuring platform is adjusted to collimate the laser beam passing through the collimating lens, the second position X1 of the collimating lens is recorded; the optical glass plate to be measured replaces the optical glass plate with a known refractive index, and the mobile measuring platform is adjusted to collimate the laser beam passing through the collimating lens again, and then the third position X2 of the collimating lens is recorded; the refractive index of the optical glass to be measured is calculated based on the first position, the second position, and the third position.

Description

Technical Field

[0001] The invention belongs to the field of measurement technology, and in particular relates to a device and a method for quickly measuring the refractive index of optical glass. Background Art

[0002] The refractive index of optical glass is a quantity that changes with the optical glass material, ambient temperature, air pressure and wavelength of incident light. When the incident light wavelength line width is extremely narrow and the air pressure and temperature do not change much, the refractive index of optical glass material changes very little and is only related to the properties of the material itself.

[0003] At present, at room temperature and standard atmospheric pressure, the refractive index of optical glass for a certain wavelength of incident light is known. For example, the common BK7 material is 1.517. If we want to know the refractive index of a common optical glass material at room temperature and standard atmospheric pressure, it is most convenient to directly look up the optical handbook. However, if we do not know the specific material of this optical glass material, or if this is not a common and commonly used material, we cannot obtain the refractive index of this optical glass material by looking up the optical handbook. Using existing refractive index measuring devices and methods to measure is another way, but existing devices and methods often contain large precision optical instruments, or the optical path is complex, and they are not particularly convenient to use. Summary of the invention

[0004] The technical problem to be solved by the present invention is to use the refractive index of a known optical glass material to quickly measure the refractive index of a certain optical glass, and to provide a device for measuring the refractive index of optical glass with reasonable design, simple structure, convenient operation and high efficiency.

[0005] The technical solution adopted to solve the above technical problems is: a device for quickly measuring the refractive index of optical glass, a laser light source is installed on the optical platform, a fixed platform, a movable measuring platform, and a shearing interferometer are installed on the optical platform in sequence along the laser emission direction, an optical glass plate with a known refractive index is arranged on the fixed platform, and a collimating lens is arranged on the movable measuring platform. The laser emitted by the laser light source passes through the optical glass plate with a known refractive index and the collimating lens in sequence and enters the shearing interferometer.

[0006] As a preferred technical solution, the thickness of the optical glass plate is 10 to 30 mm.

[0007] As a preferred technical solution, the aperture number F of the collimating lens is 1.5-3, the root mean square value RMS of the wavefront aberration is less than one-quarter of the laser wavelength, the laser wavelength matches the wavelength of the anti-reflection film of the collimating lens, and the spot diameter of the laser emitted by the laser light source after passing through the collimating lens is less than the aperture of the light hole of the shearing interferometer.

[0008] The present invention also provides a method for quickly measuring the refractive index of optical glass, comprising the following steps:

[0009] S1. At room temperature, a laser light source emits a laser beam with a divergence angle ≤10° through a collimating lens, and the mobile measuring stage is adjusted to collimate the laser beam passing through the collimating lens. The collimated laser beam enters a shearing interferometer, and the shearing interferometer is used to determine whether the laser beam is collimated. After collimation, the first position X0 of the collimating lens is recorded by the mobile measuring stage;

[0010] S2. At room temperature, in the optical path of step S1, a fixed table with an optical glass plate of known refractive index is added, and the laser beam emitted by the laser light source passes through the optical glass plate and the collimating lens. The movable measuring table is adjusted so that the laser beam passing through the collimating lens is collimated. The collimated laser beam enters the shearing interferometer, and the shearing interferometer is used to determine whether the laser beam is collimated. After collimation, the second position X1 of the collimating lens is recorded by the movable measuring table;

[0011] S3. Remove the optical glass plate with known refractive index on the fixed stage, and replace it with an optical glass plate with the same thickness as the optical glass plate with known refractive index to be measured. Due to the change in the refractive index of the optical glass, the laser beam passing through the collimating lens is no longer a collimated beam. Adjust the mobile measuring stage so that the laser beam passing through the collimating lens is collimated again, and then record the third position X2 of the collimating lens through the mobile measuring stage;

[0012] S4. The refractive index n2 of the optical glass to be tested is obtained according to the following formula:

[0013]

[0014] Where n1 is the refractive index of the known optical glass at room temperature.

[0015] The beneficial effects of the present invention are as follows:

[0016] The present invention is used for rapidly measuring the refractive index value of a certain optical glass at room temperature and standard atmospheric pressure. Compared with the existing measuring device, the present invention has a simple structure, convenient operation, fast measuring speed and high efficiency, and can be widely promoted and used. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described in detail below in conjunction with the accompanying drawings and examples, but the present invention is not limited to the following embodiments.

[0019] exist Figure 1In the embodiment, the device for quickly measuring the refractive index of optical glass is composed of an optical platform 1, a laser light source 2, a fixed platform 3, an optical glass plate with a known refractive index 4, a movable measuring platform 5, a collimating lens 6, and a shearing interferometer 7.

[0020] A laser light source 2 is installed on the optical platform 1. The numerical aperture NA value of the laser light beam emitted by the laser light source 2 is 0.11 and the wavelength is 852nm. A fixed platform 3, a mobile measuring platform 5, and a shearing interferometer 7 are installed on the optical platform 1 in sequence along the laser emission direction. An optical glass plate 4 with a known refractive index is installed on the fixed platform 3. The material of the optical glass plate is BK7, the thickness is 25.4mm, and the refractive index n1 is 1.517. A collimating lens 6 is installed on the mobile measuring platform 5. The mobile measuring platform 5 is used to adjust the position of the collimating lens 6. The aperture number F of the collimating lens 6 is 1.5 , the root mean square value RMS of the wavefront aberration is equal to 1 / 4 of the laser wavelength, the diameter is 50mm, the curvature radius of the collimating lens 6 is 112.2mm, -95.9mm, and -325.1mm from left to right, respectively. The collimating lens 6 is a double-glued collimating lens made of N-LAK22 and N-SF6HT. The laser passes through the optical glass plate 4 with a known refractive index and the collimating lens 6 in turn and enters the shearing interferometer 7. The collimating lens 6 is used to collimate the laser beam. The shearing interferometer 7 is used to determine whether the laser beam is collimated. The light spot collimated by the collimating lens 6 is smaller than the aperture of the light hole of the shearing interferometer 7.

[0021] The method for rapidly measuring the refractive index of optically transparent glass using the above device at room temperature and standard atmospheric pressure comprises the following steps:

[0022] S1. The laser light source 2 emits a laser beam with a numerical aperture NA of 0.11 and a wavelength of 852 nm. The laser beam passes through the collimating lens 6. The movable measuring stage 5 is adjusted to collimate the laser beam passing through the collimating lens 6. The collimated laser beam enters the shearing interferometer 7. The shearing interferometer 7 determines whether the laser beam is collimated. After collimation, the first position X0 of the collimating lens 6 is recorded by the movable measuring stage 5, where X0=20 mm.

[0023] S2. In the optical path of step S1, a fixed platform 3 with an optical glass plate 4 of known refractive index is added. The laser beam emitted by the laser light source 2 passes through the optical glass plate 4 of known refractive index and the collimating lens 6. The movable measuring platform 5 is adjusted to collimate the laser beam passing through the collimating lens 6. The collimated laser beam enters the shearing interferometer 7. The shearing interferometer 7 determines whether the laser beam is collimated. After collimation, the second position X1 of the collimating lens 6 is recorded by the movable measuring platform 5, where X1=11.4 mm.

[0024] S3. Remove the optical glass plate 4 with a known refractive index from the fixed table 3, and replace it with an optical glass plate of a material to be measured with a thickness of 25.4 mm. At this time, the laser beam passing through the collimating lens 6 is no longer a collimated beam. Adjust the movable measuring table 5 so that the laser beam passing through the collimating lens 6 is collimated again, and then record the third position X2 of the collimating lens 6 through the movable measuring table 5, X2 = 9.5 mm;

[0025] S4. According to the following formula, the refractive index n2 of the optical glass to be tested at room temperature and standard atmospheric pressure is obtained:

[0026]

[0027] Then n2 is 1.712.

[0028] Example 2

[0029] In this embodiment, a laser light source 2 is installed on the optical platform 1. The numerical aperture NA value of the laser beam emitted by the laser light source 2 is 0.11 and the wavelength is 852nm. A fixed platform 3, a mobile measuring platform 5, and a shearing interferometer 7 are installed on the optical platform 1 in sequence along the laser emission direction. An optical glass plate 4 with a known refractive index is installed on the fixed platform 3. The material of the optical glass plate is BK7, the thickness is 10mm, and the refractive index n1 is 1.517. A collimating lens 6 is installed on the mobile measuring platform 5. The mobile measuring platform 5 is used to adjust the position of the collimating lens 6. The aperture number F of the collimating lens 6 is 2 , the root mean square value RMS of the wavefront aberration is equal to 1 / 4 of the laser wavelength, the diameter is 50mm, the curvature radius of the collimating lens 6 is 112.2mm, -95.9mm, and -325.1mm from left to right, respectively. The collimating lens 6 is a double-glued collimating lens made of N-LAK22 and N-SF6HT. The laser passes through the optical glass plate 4 with a known refractive index and the collimating lens 6 in turn and enters the shearing interferometer 7. The collimating lens 6 is used to collimate the laser beam. The shearing interferometer 7 is used to determine whether the laser beam is collimated. The light spot collimated by the collimating lens 6 is smaller than the aperture of the light hole of the shearing interferometer 7.

[0030] The method for rapidly measuring the refractive index of optically transparent glass using the above device at room temperature and standard atmospheric pressure comprises the following steps:

[0031] S1. The laser light source 2 emits a laser beam with a numerical aperture NA of 0.11 and a wavelength of 852 nm. The laser beam passes through the collimating lens 6. The movable measuring stage 5 is adjusted to collimate the laser beam passing through the collimating lens 6. The collimated laser beam enters the shearing interferometer 7. The shearing interferometer 7 determines whether the laser beam is collimated. After collimation, the first position X0 of the collimating lens 6 is recorded by the movable measuring stage 5, where X0=10 mm.

[0032] S2. In the optical path of step S1, a fixed table 3 is added with an optical glass plate 4 with a known refractive index, the thickness of the optical glass plate 4 with a known refractive index is 10 mm, the laser beam emitted by the laser light source 2 passes through the optical glass plate and the collimating lens 6, the mobile measuring table 5 is adjusted to collimate the laser beam passing through the collimating lens 6, the collimated laser beam enters the shearing interferometer 7, the shearing interferometer 7 determines whether the laser beam is collimated, after collimation, the second position X1 of the collimating lens 6 is recorded by the mobile measuring table 5, X1 = 4.9 mm;

[0033] S3. Remove the optical glass plate 4 with a known refractive index from the fixed table 3, and replace it with an optical glass plate of a material to be measured with a thickness of 10 mm. At this time, the laser beam passing through the collimating lens 6 is no longer a collimated beam. Adjust the mobile measuring table 5 so that the laser beam passing through the collimating lens 6 is collimated again, and then record the third position X2 of the collimating lens 6 through the mobile measuring table 5, X2 = 3.5 mm;

[0034] S4. According to the following formula, the refractive index n2 of a certain optical glass at room temperature and standard atmospheric pressure is obtained:

[0035]

[0036] Then n2 is 1.77.

Claims

1. A method for rapidly determining the refractive index of optical glass, characterized in that: The device used in the method is as follows: a laser light source (2) is mounted on an optical platform (1); a fixed platform (3), a movable measuring platform (5), and a shearing interferometer (7) are sequentially mounted on the optical platform (1) along the laser emission direction; an optical glass plate (4) with a known refractive index is disposed on the fixed platform (3); a collimating lens (6) is disposed on the movable measuring platform (5); laser light emitted by the laser light source (2) sequentially passes through the optical glass plate (4) with a known refractive index and the collimating lens (6) and enters the shearing interferometer (7); The method comprises the following steps: S1. At room temperature, the laser light source (2) emits a laser beam with a divergence angle ≤10° through a collimating lens (6), and the movable measuring platform (5) is adjusted so that the laser beam passing through the collimating lens (6) is collimated. The collimated laser beam enters a shearing interferometer (7), and the shearing interferometer (7) is used to determine whether the laser beam is collimated. After collimation, the first position X0 of the collimating lens (6) is recorded through the movable measuring platform (5); S2. At room temperature, in the optical path of step S1, a fixed platform (3) equipped with an optical glass plate (4) with a known refractive index is added, and the laser beam emitted by the laser light source (2) passes through the optical glass plate and the collimating lens (6). The movable measuring platform (5) is adjusted so that the laser beam passing through the collimating lens (6) is collimated. The collimated laser beam enters the shearing interferometer (7). The shearing interferometer (7) determines whether the laser beam is collimated. After collimation, the second position X1 of the collimating lens (6) is recorded by the movable measuring platform (5); S3. Remove the optical glass plate (4) with a known refractive index on the fixed platform (3), and replace it with an optical glass plate to be measured with a thickness equal to that of the optical glass plate (4) with a known refractive index. Due to the change in the refractive index of the optical glass, the laser beam passing through the collimating lens (6) is no longer a collimated beam. Adjust the movable measuring platform (5) so that the laser beam passing through the collimating lens (6) is collimated again, and then record the third position X2 of the collimating lens (6) through the movable measuring platform (5); S4. Obtain the refractive index of the optical glass to be tested according to the following formula: In the formula, n 1 is the refractive index of the known optical glass at room temperature.

2. The method for rapidly measuring the refractive index of optical glass according to claim 1, characterized in that: The thickness of the optical glass plate (4) with known refractive index is 10 to 30 mm.

3. The method for rapidly measuring the refractive index of optical glass according to claim 1, characterized in that: The aperture number F of the collimating lens (6) is 1.5 to 3, the root mean square value RMS of the wavefront aberration is less than one quarter of the laser wavelength, the laser wavelength matches the wavelength of the anti-reflection film of the collimating lens, and the spot diameter of the laser emitted by the laser light source (2) after passing through the collimating lens (6) is less than the aperture of the light hole of the shearing interferometer (7).

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