| 摘要 |
A flat illuminant emits a beam of light toward a reflective scale having predetermined reference gratings formed thereon. A photoreceptive module is placed at a location between the flat illuminant and the reflective scale and closer to the flat illuminant. The photoreceptive module includes an array of photoreceptive devices, which also serves as illuminant-side gratings for partially shielding the beam from the flat illuminant.
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