Black And White Densitometer Based On Optical Frequency Converters

In the film production and using process, it is usually needed to monitor and detect the quality of the film. The logarithm of the Light Resistance which showed the phenomenon that the silver in the film emulsion layer can reduce the light called the film's transmission density, or density. As the result of the measurement of density is one of the most important links to the sensitometer, the accuracy of it would directly affect the validity and the exactitude of the sensitivity survey. It is not only has the advantage of quantitative determination to use the densitometer other than the eye to evaluate the shooted film, but also can made the photographic film more clearly and can contribute to distinguish the defect according to the evaluation.The traditional method we used to Measure the density is the direct-reading of optical transmission which use the battery as a receiving device, measure the light intensity through the film, and at the same time, convert the optical signals into the electrical signals, process the data of the electrical signals, and finally we get the film value which is showed in some way. But this measurement needs to handle a complex circuits system, and calibrate difficulties in the production and testing. The measuring range does not go for enough, and equipment is too large either. In order to improve measurement accuracy, enlarge range, and simplify the structure of this instrument, the paper developed a simple design which is easy to operate according to the new type of black-and-white densitometer requirements. This method use integrated optical frequency conversion chip TSL230 measures light signal directly, samples the high and low frequency separately, then process the signal by microprocessor which in counting and processing cycle method, and in the end calibration the measurements. Using LED as the light source apparatus, which has lots of advantages such as small size, long life(up to 100,000h), wide range, the light of output stability and easy to drive. The experiment proves that the designs reduces the distribution of parameters and other parameters of the outside world, stabilities the measurement results, improves the measurement accuracy, expands the measurement range, meets the measurement needs and promote a better value.