the company has developed many kinds of infrared glass that permitting transmission of near-infrared light, mid-infrared light, far-infrared light at various bands.
where, the transmission band, refractive index (nd) of near-infrared and mid-infrared glass is 0.37～6.7μm, 1.52～1.99 respectively. their glass systems include silicate system, germinate system, calcium aluminate system, lead germinate system, lead niobate system, etc. they are mainly applied to infrared-tracking、 infrared-detection, and infrared window of other near-infrared, mid-infrared instruments. at present time, the company owns mid-infrared irg1xx series (5 types).
far-infrared glass is mainly applied to infrared detectors and devices at 8～14μm, and can be processed to far-infrared optical condenser lens with aspheric surface, components of prism group with spherical surface, glass windows. it can also be used as substrate material of external semiconductor gaas, gan or ingan.
chalcogenide glasses are composed of three kinds of elements sulfur, selenium, tellurium and others(arsenic, antimony, germanium,etc) or their mutual combinations except oxygen or polonium in the sixth main group of periodic table of elements.
they offer excellent properties:
●transmission in the far infrared band(8～12μm) is over 64% while over 95% after coating.
●their low transformation and sag temperatures support molding of aspherical lens and low mass-produced cost.
●with physical properties such as low dn/dt enables the optical engineers to design color corrected optical systems without chromatic aberration or thermal defocusing.
chalcogenide glasses can be widely used for infrared monitoring, thermometry temperature measurement, medical treatment, detection, guidance and other fields.
our company can provide eight types of chalcogenide glasses irg201～irg209 in bulk and owns high accuracy infrared refractometer, infrared crack detector, infrared stria projector, fourier transform infrared spectrophotometer and other infrared testing equipments. quality of the products is completely controlled and can supply in various forms according to customers' requirements, such as blanks, parts, lens and balls, etc. currently, we would like to offer you the products with maximum sizes up to φ 200 mm.
1）product parameters of mid-inrared materials
2）product parameters of far-inrared materials
1 classification and designation of infrared optical glass
1.1 principle of classification
products are classified to mid-ir and far-ir optical glass according to the transmittance wavebands.
1.2 designation methods of glass types
irg203 refers to infrared optical glass which has transmittance at far-ir waveband and the sequence number of it is 03.
2 optical properties
2.1 infrared refractive index nλ
infrared refractive index refers to the velocity of infrared light in the air as compared to that in the medium by the municipality. deflection angle method is adopted to measure the incident angle i, refraction angle φ and vertex angle a. according to formula (1), we can obtain refractive index nλ of wavelength λ, and the measuring accuracy is ±1×10-4.
in the spectral range of 1.5~16μm, the refractive indices not listed in the handbook can be calculated by the herzberger formula (2):
where:
a, b, c, d, e, f－calculating constants.
2.2 infrared dispersion coefficient
infrared dispersion means the deviations of refractive index at different infrared wavelengths. in this handbook, the infrared dispersion coefficients υ4 and υ10.6,of two air windows 3μm-5μm and 8μm-12.5μm are given. υ4 and υ10.6 can be calculated by equation (3):
where:
υ4—infrared dispersion coefficient (3 ~ 5μm);
υ10.6—infrared dispersion coefficient (8 ~ 12.5μm);
nλ(λ=3,4,5,8,10.6,12.5)—infrared refractive index at specific wavelengths (μm).
2.3 calculating constants of nabs.
the refractive indices given in the glass handbook in general are all relative values at 22℃, but refractive indices in other temperatures are always requested by many optic designers. the absolute refractive indices of glass regards to wavelengths and temperatures which are not listed in the handbook can be calculated by the following equation (4).
where:
△nabs —the difference of absolute indices;
n(λ,t0) —relative index at the reference temperature;
t0—reference temperature(22 ℃);
t —targeted temperature (℃);
δt—temperature difference t-t0 (℃);
λ—vacuum wavelength ( μm);
d0, d1, d2, e0, e1and λtk—constants depending on glass types.
the applied temperature range: –40℃~ 80℃;
the applied wavelength range: 1μm~14μm.
2.4 infrared transmittance τ
test the infrared transmittance of samples with different thickness using double samples and single beam, and then calculate the internal transmittance of sample with thickness d at wavelength λ by formula (5):
where:
d1, d2—sample thickness ;
τ1λ—transmittance of sample with thickness d1 at wavelength λ (including surface loss) ;
τ2λ—transmittance of sample with thickness d2 at wavelength λ (including surface loss) .
3 dielectric constant
measure dielectric constant according to the recommended methods for capacitivity and dielectric loss factor of electro-insulating material at power frequency, audio frequency and high frequency (including meter wavelength) in gb/t 1409-2006.
4 others
in this handbook, chemical stabilities, thermal properties, mechanical properties and density are measured by the corresponding testing methods of colorless optical glass.
5 main quality definition
5.1 allowable tolerances of refractive index and dispersion coefficient
the differences between refractive index, dispersion coefficient of each batch products and the standard values are generally in the following tolerance ranges:
refractive index nλ：±3×10-4 υ10.6: ±0.8%
5.2 striae
striae of infrared optical glass are inspected by the methods specified in gb/t 32561.2. the gray scale of shadow images and its area taking of the observable image are adopted for quantitative expression, and striae are classified into 4 grades as shown in table 1.
table 1
grade | striae visibility |
a | no obvious striae shadow. |
b | fine and scattering striae shadow exists in side and the diameter is not greater than 1mm |
c | fine striae exists in side and the diameter is between 1mm and 2mm |
d | thick striae exists in side but not intensive and the diameter is not less than 2mm |
5.3 impurities
impurities in optical glass are inspected by the method specified in gb/t 52361.3. impurity content is established by specifying the total cross sectional area (in mm2) of impurities (diameter φimpurity≥0.1 mm) in 100 cm3 glass volume. the impurity grades are classified into 5 grades as shown in table 2. the cross sectional area of oblate impurity is obtained by the average value of the longest axis and shortest axis as the diameter.
table 2
grade | 0 | 1 | 2 | 3 | 4 |
total cross sectional area s（mm2） | s＜0.05 | 0.05≤s＜0.2 | 0.2≤s＜0.4 | 0.4≤s＜0.6 | 0.6≤s＜1.2 |
6 forms of supply
6.1 pressing blanks
blanks of various shapes (plain film, concave-convex part, etc.) are formed by reheated-press process. we can provide products with diameters of φ7mm~φ200mm stably.
6.2 infrared lens
6.2.1 cold working lens
cold working lens refer to spherical, aspheric lens after coarse grinding, fine grinding, polishing or single point diamond turning. we can provide lens with diameters of φ5mm~φ160mm according to customers’ requirements.
6.2.2 precision molding lens
precision molding lens refer to the products which are obtained by molding process. we can provide precision molding lens with diameters of φ5mm~φ25mm according to customers’ requirements.
6.3 infrared lens
lens with focal length of 3.5mm, 6.5mm, 10mm, 13mm, 15mm, 19mm, 25mm, 35mm, 45mm, 50mm and standard lens of other sizes are now available. please contact the salesman for specific parameters. we can also design and manufacture other sizes according to customers’ requirements.
6.4 others
if you have any special requirement on our products, please contact the salesman.