# Optical Density Measurement Using Optical Density Meter

Time:2020/05/26 18:00:00 Browse:1161

## I. Optical density and definition

Optical density generally abbreviated as OD. It represents the shading ability of the material, which is the national standard name. Optical density refers to the logarithm of the ratio of incident light to transmitted light, or the reciprocal of the light transmittance.

The calculation formula of optical density is: optical density = log10 (incident light / transmitted light) or optical density = log10 (1 / transmittance).

## II. Which materials need to be tested for optical density?

Through the definition of optical density, we can see that there is a fixed relationship between optical density and light transmittance. Materials with low optical density values will have relatively high light transmittance, while materials with high optical density values will do the opposite. So which materials have the need to test optical density?

For example, the materials such as black film, X-ray film, aluminized film and ink on cell phone lenses that we can see in our daily life are all required to test optical density in the industry. For these materials with very low light transmittance, it is difficult to compare the difference between the materials with the light transmittance value. But if converted into the optical density value, the data will be more intuitive.

There are corresponding optical density detection instruments on the market, such as optical density meters. Linshang LS117 optical density meter will automatically display the transmittance value and optical density value on the interface according to the conversion formula of optical density and light transmittance, making it easier and more convenient for us to test the above materials. Moreover, the Linshang LS117 optical density meter adopt diffuse transmission principle, which is the most cost-effective instrument in the market.

Test optical density and light transmittance
Use diffuse transmission principle
OD measurment range:OD0-OD 6.Light transmittance resolution can reach 0.005%
The light source conforms to the CIE photopic luminosity function standard
Model: LS117

## III. LS117 optical density meter test various materials

The optical aperture of Linshang Optical density meter LS117 is 2mm. And the materials that can be tested are very wide. The optical density measurement accuracy of the instrument is 0-2OD, the minimum can reach ± 0.02. The transmittance resolution can reach 0.0005%. It can also be tested for some materials with extremely low transmittance and the accuracy is very high.

The operation of the optical density meter LS117 is very simple. It can be tested after the power is turned on. The OD displayed on the interface is the optical density value. T is the transmittance value.

### 1. LS117 optical density meter test films

Generally, the film with a thickness of 0.1mm is black. There is also a silver film with a thickness of 0.175mm, which is collectively called a light-painted black film. There are requirements for testing the shading degree and transmittance, that is, black and white is clear (generally shading degree> 4.0, Transmittance is less than 0.04).

What needs to penetrate is full-wave band white light, so the optical density meter LS117 measures the optical density of full-wave band white light in the 380-760nm.

There are two measurement methods for the optical density meter LS117. The small film can be placed on a fixed base for testing. To test the large film, we need to take out the receiver and the light source and align it manually for measurement.

### 2. LS117 optical density meter test X-ray film

X-ray films are mostly used in medical treatment. A high-quality qualified X-ray film should be judged from the quality of the photo image and whether it meets the diagnostic requirements. The high-quality X-ray film should have clear photos and good contrast. The density should not be too high or too low. There should be no artifacts affecting the diagnosis on the surface. In the end, there must be clear signs and clear instructions.

When measuring the X-ray film with the optical density meter LS117, the user can use the light source and receiver to carry out the measurement after the self-calibration.

## 3. LS117 optical density meter test aluminum coating

Vacuum aluminized film is a composite flexible packaging material with low price, beautiful appearance, excellent performance and strong practicability. The greater the optical density of the finished aluminum film, the higher the certain substance content. In the analysis of optical performance, if you want to know the uniformity of the certain substance content distribution in the whole, you can use an optical density meter. You can accurately measure the uniformity of the aluminum coating thickness and the light transmittance value.

After the optical density meter LS117 has passed the self-calibration, the screen shows that the OD (optical density) is "0.000" and the T (transmittance) shows "100.00%". Put the aluminum coating in for testing and test several sets of data to compare Uniformity.

### 4. LS117 optical density meter test cell phone lens ink

The inks in mobile phone lenses are often used in mobile phone lens manufacturers. The glass lens industry uses inks to process various kinds of reinforced white sheet materials, such as acrylic, PC, PET / composite materials, etc. The lens ink not only has good adhesion, strong infrared transmittance, but also has a high coverage rate. The OD (optical density) value can reach 4.0 or more. There is no bad phenomenon such as light transmission, trachoma and pinholes. The OD value of cell phone lens ink is tested in the industry. It is usually measured by optical density meter.

After the optical density meter LS117 is turned on, when the interface displays OD (optical density) as "0.000" and T (transmittance) as "100.00%", just align the ink position of the mobile phone lens with the test hole. The test will be displayed on the screen.

In addition to the above materials, Linshang optical density meter LS117 can also test the optical density of banknotes, express bags, matte materials, opalescent materials, zirconia raw materials, diffusion plates, lampshades, dimming films and other materials.

The optical density meter LS117 was developed based on the national "JJG 920-1996 Diffuse Transmission Visual Densitometer" standard. It can pass the inspection of Chinese Third-Party Metrology Institute.