| 摘要 |
PURPOSE:To easily calibrate a detection origin by calculating and determining an offset quantity by a distance setting jig based on the difference between the distance from the holding part of a projection lens and the distance detection output of the holding part. CONSTITUTION:When the distance setting jig 28 is set at a projection surface part 15, the distance between the reference surface 18 of the holding part 12 for the projection lens 11 and the projection surface part 15 is set to distance A'. The distance Ax between the main surface Pa of the lens 11 and the projection surface part 15, on the other hand, is detected as Ax=KaXalpha from the encoder and counter of a distance detector which is associated with a mechanism for elevating and lowering the holding part 12. Here, Ka is a counter value and alpha is the resolution of the encoder. Then, the offset Aoff of the detection zero point of the distance detector is determined from Ax-(A'+a). Here, (a) is the distance between the reference surface 18 and main surface Pa. The distance detection offset quantity as to a film surface 13 is determined similarly and the detection origin is easily calibrated by using a reference distance setting jig.
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