A mechanism, employed for a camera, which obtains information upon a three-dimensional configuration and which does not give a user a feeling of unpleasantness. A monitor display device of the mechanism has an image storage device for storing a non-pattern image which has been taken by an image taking device when a patterned light is not projected by a pattern projector. When the patterned light is projected by the pattern projector, the monitor displays the non-pattern image stored on the image storage device, instead of displaying the image with a pattern which has been taken by the image taking device.