| 释义 |
shadow-casting, ppl. a. and vbl. n.
A. ppl. a. That casts a shadow or shadows.
1859Tennyson Merlin & V. 479 To him the wall That sunders ghosts and shadow-casting men Became a crystal. 1882Encycl. Brit. XIV. 584/1 The shadow-casting object should be near the screen. 1904W. de la Mare Henry Brocken 145 Laid embraced in the shadow-casting moonlight. 1953Jrnl. Exper. Psychol. XLV. 206/1 The shadow-casting object is placed as close to the screen as possible, whereas the distance between the light source and the object is made large.
B. vbl. n.
1. Microscopy. A technique for enhancing an electron-microscope image by projecting a beam of small particles or atoms (usu. of a heavy metal) on to the sample at a small angle to the horizontal, so as to form a deposit giving the appearance of shadows cast by sideways illumination.
1944Williams & Wyckoff in Jrnl. Appl. Physics XV. 712/2 Information was needed in our work other than that provided by stereoscopic photography. A procedure for measuring heights based on shadow-casting was accordingly developed to meet this need. 1947Ann. Rev. Microbiol. I. 11 With the addition of the shadow casting technique, about eleven fibrils were clearly seen to compose the cilium of Paramecium. 1971V. A. Phillips Mod. Metallogr. Techniques & Applications v. 183 It is customary to enhance the contrast of replicas by shadow casting, that is, by evaporating a heavy metal from an angle to give shadow effects in the final electron micrograph, equivalent to oblique light illumination.
2. lit. The casting of shadows, esp. in Psychol. as a technique of perceptual research. Also attrib.
1957Psychol. Rev. LXIV. 291/2 Previous shadow⁓casting devices..have not been constructed for this systematic purpose. 1971Nature 3 Sept. 55/2 The geometric principles of shadow casting and the use of chromatic filters for dichoptic stimulation are established techniques.
Hence (as a back-formation) ˈshadow-cast v. trans., to enhance (a microscopic image) by shadow-casting; to subject (a microscopic specimen) to shadow-casting; also as ppl. a.; shadow caster, a device employed in perceptual research in order to cast shadows, esp. one for producing seemingly three-dimensional shadows.
1944Jrnl. Appl. Physics XV. 715/2 (caption) Example of a shadow-cast electron micrograph for the determination of the heights of objects. 1957Psychol. Rev. LXIV. 291/2 Considering the mount and the screen as two geometrical planes, changes in the position of the mount will yield all possible perspective transformations of the shadow relative to the shadow caster. 1969Vision Res. IX. 154 The principal advantage of the stereoscopic shadow-caster over other stereoscopic projection methods lies in its versatility in the study of binocular kinetic space perception. 1971V. A. Phillips Mod. Metallogr. Techniques & Applications v. 187 After being allowed to harden, it is dry-stripped and shadow cast. 1971Nature 3 Sept. 55/2 To produce this effect, a stereoscopic shadow caster was used, in which two point sources slightly separated horizontally cast the shadows of three vertical rods on a rear-projection screen. 1979Ibid. 27 Sept. 287/2 Film samples were transferred to..electron microscope grids... Transferred films were shadowcast in the direction of compression with platinum-palladium at an angle of 10° before examination in a Siemens Elmiskop. |