The present invention relates to a method of and apparatus for enabling the visualization of isometric physical condition maps of a three-dimensional test object, the physical condition being for example the amplitude of vibration of the test object or the contour of the object. The latter is studied by the striation method whereby flat parallel light beams on light on the object forming a system of striations thereon; there is superimposed on the image in a given direction of the illuminated object a corresponding image of a typical comparison object, the resultant superimposed image being a coded representation of the physical condition of the test object. A television camera is used to analyze the successive images of the system of striations formed on the surface of the object. The modulation signal is separated from the synchronizing signals, filtered and demodulated so as to reproduce in real time on a viewing device or control receiver an isometric physical condition map of the object with free from the structure.

A method and apparatus for comparing two objects having similar shapes and dimensions wherein one of the objects is illuminated by a collimated light beam whose intensity is modulated in a direction transverse thereto at a spatial frequency 1/p. The modulated light beam generates a lattice of alternately dark and light parallel bands similar to interference fringes having a pitch p on the illuminated surface of the object having a configuration in the manner of contour lines determined by the relief of the illuminated side of the object. The other object is thereafter substituted for the first one and in the same position, and is similarly illuminated by the same beam but wherein the intensity modulation has been phase-shifted by 180.degree.. The respective images of the two objects are optically superimposed and from which is then obtained only the differential component of the image which is modulated with a spatial frequency 1/p. Apparatus for carrying out the method can be either (1) photographic in which case the superimposed images of the two objects are established by development on a photo-sensitive negative which is light-transmissive in conjunction with a lens which transmits only the differential component in the negative to a photographic plate, or (2) electronically by means of a TV camera and related components by which the respective video images are added and passed to a visual display device such as a cathode ray tube via a filter having a pass band transmitting only the differential signal component which is modulated by the time frequency v/p wherein v constitutes the linear sweep speed of the TV camera.

A method of optically mapping a person's face includes the steps of illuminating the face through a grid structure to produce a grid representation on the face; viewing the illuminated face with a video camera; producing a video signal in response to the step of viewing; converting the video signal to digital form; storing a frame of the digitized video signal in a frame memory; defining the grid representation on the face, from the stored video signal; locating coordinates of the intersection points of the grid representation; determining curvatures of the grid representation at the located intersection points; and three-dimensionally reconstructing the surface of the face from the coordinates and curvatures of the intersection points.

A shape measuring apparatus includes a first light source for illuminating a solid object in a proper place through a first slide, a second light source for illuminating the object through a second slide and an observation plane permitting the surface of the object to be observed through a focal point. Each of the first and second slides, contains slit lines. When the first and second light sources are lighted, the slit lines of the first and second slide are projected, in an intersecting pattern, on the surface of the object. A projection grating is formed on the surface of the object and is observed, as a projection grating, in the observation plane. The space coordinates of any one arbitrary point of a grating point array on the projection grating are determined by determining a light beam projecting the grating point after it has left the first light source, determining a light beam projecting the grating point after it has left the second light source, determining a light beam, through the focal point, to permit the grating point corresponding to the projection grating point to be observed in the observation plane and determining the space coordinates of the intersection of at least two of the three light beams. Similarly, the space coordinates of other grating points on the projection grating are sequentially determined, thus measuring the shape of the object.

A technique for comparing master parts with replicas to determine differences in shapes or sizes, is disclosed, which uses interferometric techniques as disclosed. A television camera is used to scan the pattern established by illuminating the subject with a set of optical fringes. An objective lens images these on a transmission line grating. A television camera scans the transmission grating. The spatial frequencies of the subject fringes and of the grating are especially selected so that the camera can not resolve either of them but can resolve their difference. As a result, the output signals of the camera represent a contour map of the object placed on a low frequency spatial carrier, but yet, the measurement sensitivity is still determined by the spatial frequency of the subject fringes.