The Research On Large Dynamic Range Radiation Standard Transmission Technology

With the development of optical remote sensing and photoelectric detection technology,low light level remote sensing has become a new research direction,and the dynamic range of current laboratory radiation standards needs to be expanded.The difficulty of expanding the dynamic range of the radiation standard is how to expand the dynamic range of the radiation source and how to calibrate the full-dynamic range radiance.This article focuses on how to expand the dynamic range of radiation sources and develops a large dynamic range radiation standard transmission technology.A large dynamic range radiation standard transmission link is proposed.It based on a laboratory radiation standard which consisted of an irradiance standard and a diffuser system,and a large dynamic range adjustable integrating sphere source.According to different adjustment methods of different brightness levels of integrating sphere,it works in normal mode and low light mode.In the normal mode,the radiation standard of the laboratory radiation standard is transmitted through the hyper spectral radiometer to each radiance level of the integrating sphere.Constrained by the response range of spectral radiometer,in the low-light mode,the brightest state in the low-light mode is calibrated by a hyperspectral radiometer at first.Using this as a reference point,the radiation standard is transmitted to the low-light level by a linearly calibrated silicon detector.Through the beam superposition method based on the double LEDs light source integrating sphere,the response linearity of the silicon detector is calibrated within 9 orders of magnitude.A large dynamic range adjustable integrating sphere light source is designed,which is composed of a built-in light source and an external light source,including two types of light sources,xenon lamps and tungsten halogen lamps.Through the adjustable aperture to control the flux from the external light source into the integrating sphere,the dynamic range adjustment of the integrating sphere could be realized.The adjustable aperture consists of a closed-loop stepper motor,ball screw and exponential blade.The adjustment range and repeatability of the diaphragm are tested.The test results show that the adjustable aperture has good performance.The integrating sphere light source has a light outlet with a diameter of 900mm,an inner diameter of 2200mm,and the opening surface ratio reached 7.1%.In order to maintain the uniformity and angular uniformity of the radiant surface of the integrating sphere light source under the condition of a large aperture ratio,a method using a surface light source as an integrating sphere internal illumination source wasadopted by optical simulation.The installation method of halogen lamps was changed.A uniform light quartz plate was added to the opening of the external light source.The optical properties of the quartz plate were tested and screened to improve the Lambertian of the light source.The adjustment scheme of the large dynamic range of the integrating sphere light source is given.Through software control,a radiance level of over 1000 can be achieved.The radiant adjustment range of the integrating sphere light source is approximately 2.38×10-7 Lmax～1.0Lmax.In the laboratory,the output radiance,stability,surface uniformity,and angular uniformity of the integrating sphere light source were examined.The uncertainty of the radiance of the integrating sphere light source was evaluated.Within the range of 400 to 1000 nm,the expanded uncertainty(K=2)of the emitted radiance in the normal mode was 5.23%to 5.48%.The radiant radiance in the low-light mode was evaluated.The expanded uncertainty(K=2)is 5.75%to 5.88%.The realization of the wide dynamic range of radiation standards has important significance for the quantitative development of optical radiation measurements.