The invention discloses a blackboard-writing projecting
system for teaching. The blackboard-writing projecting
system comprises a blackboard-writing projecting plate (1), a background mechanism and a
projector (2), wherein the background mechanism is positioned at the rear side of the blackboard-writing projecting plate (1) and is close to the blackboard-writing projecting plate (1), the blackboard-writing projecting plate (1) is made of a transparent material, the background mechanism comprises a fixed black background plate (3) and a
projection screen plate (4), the
projection screen plate (4) is positioned between the fixed black background plate (3) and the blackboard-writing projecting plate (1), the
projection screen plate (4) is made of electronically-controlled
liquid crystal photochromic glass, the electronically-controlled
liquid crystal photochromic glass is transparent when being electrified, and is white when being in power failure, and the
projector (2) projects on the electronically-controlled
liquid crystal photochromic glass in power failure when projecting. According to the blackboard-writing projecting
system, the writing area can be effectively increased, and a projection position can be changed by changing a position of the electronically-controlled liquid
crystal photochromic glass or a power failure region, so that persons in different angles can see projected contents clearly.