• Color Glass Filter

Color Glass Filter

Color Glass Comparative (CHINESE, SCHOTT, HOYA)

Chinese Color Glass Type

Classifications and Names

1.Cut-off Color Glass
The spectral transmittance curve of this kind of glass is as shown in Fig.1. Their spectral characteristic is represented by the limit wavelength of transmission(Lambdatj), the allowable deviation of limit wavelength of transmission, the transmittance(TLambda 0) at a defined wavelength and the slope of transmission curve(K).

2.Absorption-selective Color Glass
This kind of glass only transmits(or absorbs)light within one or several wavelength ranges as shown in fig.2. Their spectral characteristic is represented by the transmittance of a defined wavelength at a certain glass thickness and the allowable deviation value of transmittance at a certain glass thickness.

 

3.Neutral Color Glass
This kind of glass uniformly absorbs all the light at different visible wavelengths. Its transmittance curve is as shown in Fig.3. Their spectral characteristic is represented by the average transmittance(Tp), the allowable deviation of the average transmittance and the maximum allowable deviation Qz.

 

Where:
R = Reflectance
no = index of refraction of air
n1 = index of refraction of the color glass, typically 1.51-1.56.

Therefore, R is 0.04 at one surface for a typical color glass in the air. The total reflection loss for two surfaces is approximately 0.08.

Internal transmittance can also be used to determine the transmission at other glass thickness by:

(Tt2)=(Tt1)t2/t1

Where:
Tt1 = Internal transmittance at λfor thickness t1
Tt2 = Internal transmittance at λfor thickness t2

Based on their spectral transmission characteristic, primarily we divide color glass into 3 categories. And according to the color, optical properties, and the first alphabet of the Chinese pronunciation of the colors, we further divided them into 20 groups and 117 types and named them.

1.Cut-off Color Glass

The glass is named based on spectral characteristic, which is represented by the wavelength transmission limit. For example, if the transmission limit of glass is 490nm,then it is named as JB490.There are altogether 5 groups and 35 types glasses.

2.Absorption-selective Color Glass

This category of glass can be divided into 14 groups and 78 types in this catalogue based on spectral characteristic represented by wavelength transmission.

3.Neutral Color Glass

The glasses in this category are named based on their average transmission on a 2mm thick sample at the wavelength from 400nm to 700nm. For example, if the average transmission is 70%, we name it as ZAB70. Altogether here are 10 types of glass in this category. But the transmission of three types(ZAB65,ZAB30,ZAB5) is tested at the wavelength of 440nm-660nm.

Spectral transmittance characteristic

The limit wavelength of transmission(t) refers to the wavelength, at which the transmittance is 50% of the maximum transmittance at the defined wavelength(Lambda 0) when the thickness of the sample glass is defined. We use Lambda tj to represent it.

Lambda0 is the transmittance at a defined wavelength. It is the top transmittance of the transmittance curve.

The slope of transmittance curve is represented by the difference between the light density at Lambdatj and Lambdatj-20nm at a certain glass thickness. That is K = D Lambdatj-20nm - D Lambdatj.

The average transmittance is the average of a group of transmittance values measured every 20nm among the defined wavelength range.

The allowable deviation of the average transmittance means the allowable deviation of average transmittance of a certain type of glass. We use Delta Tp to represent it.

The maximum allowable deviation means the absolute difference between the transmittance with the maximum average transmittance deviation and the average transmittance. We use Qz to represent it.

Transmittance of Color Glass

As any other transparent optics materials, color glass also has surface reflectance, which is given by: