Wearable optical see-through head-mounted display capable of adjusting virtual image depth

Persons who experience vertigo often describe their symptoms as a sensation of oscillations. Based on such a description, a pilot study was performed to determine if the frequency of the vertigo sensation could be quantified in a manner analogous to tone matching in tinnitus treatment. Fifteen subjects were tested using a virtual image system that consisted of a head mounted display showing a scene that oscillated horizontally or vertically at an adjustable frequency. Subjects were asked to adjust the direction and frequency to match their typical vertigo sensation. Results show that most persons with chronic vertigo had symptoms that could be realistically simulated by vection induced by the oscillating scene and that matched to a consistent specific frequency. They reported an average frequency of 1.09 Hz (range 0.27 to 3.3 Hz, SD 0.25). The large majority (13 out of 15) matched to a horizontal stimulus. Subjects that gave particularly high subjective ratings of the similarity of the motion sensation (7–8 out of 10) from the vection to their vertigo had lower frequency matches (average 0.61 +/- 0.25). Repeated measurements in 4 subjects 8 to 27 days later showed consistent results. This vertigo measurement technique may be used in the future to assess the ability of vestibular rehabilitation to reduce chronic vertigo. Identification of a specific frequency of chronic vertigo may be important in the specification of rehabilitation exercises.

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Resolution in photoelectron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086593 ◽

1991 ◽

Vol 49 ◽

pp. 458-459

Author(s):

G. F. Rempfer

Keyword(s):

Electron Microscopy ◽

Electric Field ◽

Ultraviolet Light ◽

Uniform Field ◽

Virtual Image ◽

Lens System ◽

Photoemission Electron Microscopy ◽

Planar Electrode ◽

Electron Lens ◽

Photoemission Electron

In photoelectron microscopy (PEM), also called photoemission electron microscopy (PEEM), the image is formed by electrons which have been liberated from the specimen by ultraviolet light. The electrons are accelerated by an electric field before being imaged by an electron lens system. The specimen is supported on a planar electrode (or the electrode itself may be the specimen), and the accelerating field is applied between the specimen, which serves as the cathode, and an anode. The accelerating field is essentially uniform except for microfields near the surface of the specimen and a diverging field near the anode aperture. The uniform field forms a virtual image of the specimen (virtual specimen) at unit lateral magnification, approximately twice as far from the anode as is the specimen. The diverging field at the anode aperture in turn forms a virtual image of the virtual specimen at magnification 2/3, at a distance from the anode of 4/3 the specimen distance. This demagnified virtual image is the object for the objective stage of the lens system.

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