Development Of Luminous Transmittance And Haze Measuring Device Based On Structure Of Double-integrating Spheres

Luminous transmittance is an important indicator to characterize thetransmission characteristics of material. And haze is another important indicator todescribe the physical properties of transparent materials, which characterizes thescattering capability to the transmitted light. For example, in civilian areas, theluminous transmittance of plastics will affect the lighting conditions of crop in thegreenhouse. Haze of plastic packaging will directly affect the clarity of the printedcontent. For aircraft industry, luminous transmittance and haze of aircraft windshieldscreen will directly affect the pilot’s visual distance and resolution of image.Therefore, to ensure the safety of flight, study of these two performance indicators isof great significance. And accurate measurement of luminous transmittance and hazeis required.In domestic, some devices have been developed to measure the luminoustransmittance and haze, whose structure and operational principle comply withGB/T2410-2008. Their receivers are composed of a single integrating spherestructure with optical trap. By moving the standard reflectance plate upon the trap,different outlet is achieved and different luminous flux is measured at differentmoments accordingly. However, because of the movement of the standardreflectance plate, measurement efficiency is low. At the same time, these devices can only apply to small transparent pieces in the lab. They can’t test transparent pieceswith large surface in the aviation production.In this article, a new type of device based on structure of double-integratingspheres was designed and developed to measure the luminous transmittance and haze.In order to achieve efficient, precise and synchronous measurement of luminoustransmittance and haze, in the device, parallel light was generated by LEDmodulated by current and the detection part was made up of double-integratingspheres. Through analysis of various parameters, physical model of measurementwas simplified. Then the algorithm and measurement scheme were given. Accordingto the technical route, electronic system was designed, which was made up of lock-inamplifier, signal generation and LED driving circuit, data acquisition system and soon. And the programs were coded accordingly. Finally, the performance of this newdevice was tested. The accuracy of luminous transmission measurement and hazemeasurement were0.3%and0.23%respectively. And in terms of the repetitiveness,the deviation of luminous transmission measurement and haze measurement were0.04%and0.007%respectively. The results show that the device has goodmeasurement accuracy and repetitiveness, which reach the desired specifications.