| 摘要 |
PURPOSE:To save the electric power and at the same time eliminate the trouble due to the lamp disconnection or the like without providing any light source part, by securing a coincidence between the pickup state of the test pattern formed by an exterminal illumination and that formed by the built-in pattern projector. CONSTITUTION:The optical path change-over mirror prism 21 is provided between the relay lens front group 5 and rear group 7 at the relay lens part II of the zoom lens X. This prism 21 is out of the effective light flux which is delivered from the group 5 and then enters the group 7 in the normal pickup state, and then inserted into the effective light flux when the test pattern chart 2' of the built-in pattern projector is picked up. Then the light entered the lens X is reflected to the prism 21 through the part II and the group 5 and then put into the condenser lens 27. And the light delivered from the lens 27 varies its optical path via the optical path deflecting prism 24 to illuminate the chart 2'. The light delivered from the prism 24 is put into the prism 21 via the projection lens 8 in order to secure a coincidence between the test pattern formed by the external light and the pickup state of the chart 2' without using any internal power source. |
