an orthoscope

[Gr. ἀν (an), priv.; ὀρθός ( orthos ) = straight; σκοπέω ( skopeō ) = to look at.] The Optics: An instrument for producing a particular kind of optical illusion by means of two opposite disks rotating rapidly. hinder disk, which is transparent, has certain distorted figures painted upon it. The other one, which is in front of that now described, is opaque, but is pierced with a number of narrow slits, through which the figures on the disk behind it may be viewed.