CN100405043C - A high-precision measurement method for the refractive index of optical glass - Google Patents

Abstract

A high-precision measurement method for the refractive index of optical glass, which belongs to the technical field of optical precision measurement, adopts the following steps: turn on the light source in the optical glass refractive index measuring instrument; When the slit of the prism is aligned, the angle measuring encoder is cleared; the prism is placed on the turntable, and the minimum deflection angle values corresponding to the three vertex angles of the prism are measured sequentially; the refractive index of the measured optical glass is calculated by the formula; according to the test Ambient conditions correct the measured refractive index. Because the present invention adopts the method of measuring the minimum deflection angles corresponding to the three apex angles of the triangular prism, and calculating the refractive index according to the three minimum deflection angle values, the error caused when measuring the apex angles of the triangular prism is avoided, and the refractive index of the optical glass is measured Accuracy improved by nearly three times.

Description

A high-precision measurement method for the refractive index of optical glass

technical field

The invention belongs to the technical field of optical precision measurement, and relates to a method for measuring the refractive index, in particular to a high-precision method for measuring the refractive index of optical glass.

technical background

With the rapid development and application of precision optical measuring instruments in the fields of industry and science and technology, the requirements for the imaging quality of optical systems are getting higher and higher. In order to ensure the imaging quality of the optical system, it has become a very important link to accurately measure the refractive index of the optical glass used in the optical lens.

There are many methods for measuring the refractive index of optical glass, such as minimum deflection angle method, self-collimation method, V-prism refractometer method and interferometry. Due to the high precision, wide wavelength range and absolute measurement of the minimum deflection angle method, the minimum deflection angle method is commonly used in most high-precision optical glass refractive index measuring instruments. The minimum deflection angle method is usually to measure one of the vertex angles of a prism and its minimum deflection angle to calculate the refractive index of optical glass.

When measuring the minimum deflection angle, the three-image method is generally used for aiming. The relative positional relationship between the internal reflection image and the external reflection image of the refraction image seen in the field of view is used to aim. Small, the minimum deviation angle measurement accuracy mainly depends on the encoder angle measurement accuracy. The measurement of the vertex angle of the prism generally adopts the self-collimation method and the reflection method. Regardless of the self-collimation method or the reflection method, the reflection image of the slit or the crosshair is used for aiming. The reflectivity of the three reflection surfaces of the prism is low. , Relatively speaking, the aiming accuracy is worse, and there are certain differences in the measurement of different people. Therefore, the measurement accuracy of the apex angle of the prism depends on the angle measurement accuracy of the encoder and the aiming accuracy of the slit or crosshair.

Contents of the invention

The present invention adopts the method of measuring three minimum deflection angles corresponding to the three apex angles of the triangular prism, calculates the refractive index of optical glass through the three minimum deflection angle values, and aims to provide a high-precision measurement method for the refractive index of optical glass.

The present invention adopts following measurement steps:

a. Turn on the light source, image the light source near the incident slit of the collimator through the lens, and the light emitted by the collimator is parallel light;

b Use the crosshair on the reticle of the telescope to aim at the incident slit of the collimator, and clear the angle encoder;

c. Place the prism on the stage so that the parallel light emitted by the collimator shines on the prism. By rotating the stage and the telescope, you can see the refraction image, internal reflection image and external reflection image at the same time in the field of view of the telescope. , find the minimum deflection angle position corresponding to one of the vertex angles A of the prism, and read the minimum deflection angle value δ _minA from the angle measuring encoder;

d. Turn the stage to find the minimum deflection angle positions corresponding to the other two top angles B and C in turn, and read the minimum deflection angle values δ _minB and δ _minC from the angle encoder;

e. Calculate the refractive index of the measured optical glass through the formula, the formula is arcsin(cos(δ _minA /2)/(n-sin(δ _minA /2)))+arcsin(cos(δ _minB /2)/( n-sin(δ _minB /2)))+arcsin(cos(δ _minC /2)/(n-sin(δ _minC /2)))-π/2=0, where n is the measured pair of optical glass The refractive indices of the light emitted by the light source, δ _minA , δ _minB , and δ _minC are respectively the minimum deflection angles corresponding to the three vertex angles of the prism.

h. Correct the calculated refractive index according to the temperature and pressure of the test environment.

Because the present invention adopts the method of measuring the minimum deflection angles corresponding to the three apex angles of the triangular prism, and calculating the refractive index according to the three minimum deflection angle values, the error caused when measuring the apex angles of the triangular prism is avoided, and the refractive index of the optical glass is measured Accuracy improved by nearly three times.

Detailed ways

The triangular prism adopted in the present invention is a regular triangular prism with high transmittance, and the light source can be mercury lamp, hydrogen lamp and other spectral lamps, and the refractive index corresponding to the wavelength can be obtained by measuring light of different wavelengths.

Claims (1)

1. the high-precision measuring method of an optical glass refractive index is characterized in that adopting the following step:

A. open light source, near the parallel light tube entrance slit, the light that parallel light tube penetrates is directional light to scioptics source imaging;

B aims at parallel light tube entrance slit, angle measurement encoder tanks with the cross hair on the telescopical graticule;

C. prism is positioned on the objective table, parallel light tube outgoing directional light is radiated on the prism, by rotating objective table and rotating telescope, in range of telescope, see dioptric image, internal reflection picture and external reflection picture simultaneously, find the pairing angle of minimum deviation of one of them drift angle A of prism position, read angle of minimum deviation value δ from the angle measurement scrambler _MinA

D. rotate objective table, find the pairing angle of minimum deviation of two other drift angle B and C position successively, read angle of minimum deviation value δ from the angle measurement scrambler _MinB, δ _MinC

E. calculate the refractive index of institute's photometry glass by formula, formula is arcsin (cos (δ _MinA/ 2)/(n-sin (δ _MinA/ 2)))+arcsin (cos (δ _MinB/ 2)/(n-sin (δ _MinB/ 2)))+arcsin (cos (δ _MinC/ 2)/(n-sin (δ _MinC/ 2)))-and pi/2=0, the refractive index of the n light that to be institute's photometry glass send light source in the formula, δ _MinA, δ _MinB, δ _MinCBe respectively three pairing angle of minimum deviation of drift angle of prism;

H. according to temperature, the pressure of test environment the refractive index that calculates is revised.