PURPOSE: To pick up two objects at proper positions on a monitor screen in a high contrast, by providing a means which controls the slope of a reflecting surface to an opticlal reflecting means and furthermore a means which covers a part of an optical axis for each object.

CONSTITUTION: A control screw 12 is provided to mirrors 50 and 60 respectively to control the slope of each reflecting surface. The picture of an object can be shifted to a proper position on a monitor screen by turning the screw 12. At the same time, a hood 14 of a casing 8 contains a picture receiving window 15 on its front surface, and mask plates 16 and 17 which can move up and down are provided at the upper and lower parts of the window 15. An interference distortion is sometimes produced at the counter areas of pictures owing to an overlap of optical axes with two objects. This distortion is generated when a part of the optical axis is made incident with an overlap between the optical axis and a lens 7. In this respect, a part of the optical axis is covered by the plates 16 and 17. This secures a high-contrast picture which is free from any distortion.