| 摘要 |
A light pen for detecting radiation from a display screen has a tubular body with a conical tip (1). The tip which fastens into the pen body includes an opaque bush (4) which has a bore (5) having a precisely determined diameter for transmitting light from an aperture in the tip to a light sensing device mounted in the body of the pen. The bore or interior surface of the bush has a surface formed to eliminate internal reflection.
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