| 摘要 |
A device for determining an amount of focus adjustment for an image-forming optical system which forms an image on a predetermined image plane includes a sensor, an image-re-forming optical system which re-forms the image on the sensor, and a reference member disposed at a position close to the predetermined image plane of the image-forming optical system. The projection image of the reference member is detected by the sensor, and a correction calculation is performed on the basis of the displacement of the projection image of the reference member from a preset position, so that errors in detection results caused by temperature variation, etc., are corrected.
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