Tunable Light Source-Uniform Light source

Introduction

light sources are very popular in many optical experiments, but many can’t provide monochromatic light or a short bandwidth light. Tunable Light Source (TLS) can match these requirements. It’s very easy to achieve high bright emission light or hight resolution monochromatic light with a diffraction system.

Application

Uniform light source is one important part of TLS system, which is widely used in the non-uniformity measurement of array detectors, such as CCD or CMOS camera.

Non-uniformity measurement of CCD

CCD contains many pixels, each pixel may behave a little different, because of the quality of silicon or the manufacturing. We may find each pixel has different dark current and Quantum efficiency, even when the capturing settings (AD values, exposure Time) are same. Non-uniformity measurement is very important in some areas, such as in Astronomy, we need to know the non-uniformity of the big array detector before observation.

Uniform light source plays a key role in the whole non-uniformity system.

Fig.1：Diagram of non-uniformity measurement of CCD Chip, including TLS and Integrating Sphere

After integrating Sphere, the monochromatic light is uniform, which is suitable for non-uniformity measurement. Tungsten lamp is often used in this kind of measurement, as it output a wide range wavelength (from UIS to NIR), and the spectral is smooth.

Before the non-uniformity measurement, we should test the stability and uniformity of light after integrating Sphere.

With a power meter put on the output of Integrating Sphere, we can get two values of light energy, one is on the beginning of the lamp start, the other is after long time working (for example, after 30 Mins). We may optimize the working current till the stability of light power is the best. If the stability of power is within 1%, we may say the stability is suitable for the measurement!

Also, For the uniformity measurement of light spot, we can put the power meter on a X-Y stage, where the CCD chips will stand. With a small step scanning, we can find if the light spot is suitable for the measurement with measuring the light power step by step.

Now, we can do the non-uniformity measurement. With the help of shutter, we get the two image data, (dark image and illuminating image) with the same acquisition settings. After analysing the data, non-uniformity of CCD will be achieved!

Fig2：Zolix provide uniform light system based on TLS

Zolix can provide different kinds of tunable light source, which are suitable for applications in many field!

Fig3：Different combination of TLS

TLS(320mm Monochromator+Light source)

TLS(200mm Monochromator+Light source)

References

[1] Liang Shaolin, Wang Yongmei, Mao Jinghua, Jia Nan, Shi Entao,Infrared and Laser Engineering, 0417004, 48（2019）.

[2] EMVA Standard 1288,Standard for Characterization of Image Sensors and Cameras，2021.

[3] Wang Shushu, Ping Yiding, Men Jinrui, Zhang Chen, Zhao Changyin，Proc. SPIE 11525, SPIE Future Sensing Technologies, 115252I (2020).