INTERFACE DEVICE FOR DISPLAY DATA FETCH AND TRANSFER

PURPOSE:To reduce the size of a device at a data transfer origin and decrease the number of components, and to prolong the life of a product to reliability guarantee by providing a means for fetching light signal data and a transfer means for the fetched data. CONSTITUTION:When liquid crystal 13 is in transmission mode, light which passes through a polarizing material 15a, the liquid crystal 13, and a polarizing material 15b and is reflected by a reflecting plate 14 as to light emitted by a light source 21 in an interface device 200 is photodetected by a photodetecting element 22. When the liquid crystal 13 is in light shield mode, on the other hand, the light passing through the liquid crystal 13 is cut off by the material 15b and does not reach the plate 14, so the light reflected by the plate 14 does not reach the element 22. However, light reflected by the surface of a glass substrate 11 also reaches the element 22, so variation in photodetected light intensity is observed on the element 22. Consequently, a comparator 23 judges whether or not there is sent data from the quantity of photodetection is larger or smaller than a reference level and the data is transferred through a data transfer device 3. Thus, the components are decreased in number to prolong the product life to the reliability guarantee.