Title:
OPTICAL DEVICE
Document Type and Number:
Japanese Patent JPH01268372
Kind Code:
A
Abstract:
PURPOSE:To miniaturize a bracket by constituting a pressure governing mechanism of a hollow body whose volume is changed by an external pressure and sealing this mechanism in such position in the bracket that it does not intercept the light from a projection tube to a lens. CONSTITUTION:A hollow body 12 is sealed together with a transparent medium in the space surrounded with a projection tube 1, a bracket 3, and a first lens 7 so that this hollow body 12 does not intercept the light from the image projected on the projection tube 1 to the first lens 7. When the projection tube 1 generates heat and the temperature of the transparent medium rises, its volume is increased by 2-5%. This volume increase of the transparent medium is absorbed by deformation of the hollow body 12 in which air is sealed. Since it is unnecessary to attach bellows, which absorb thermal expansion of the transparent medium, to the bracket 3, not only the bracket 3 is made small-sized and light-weight but also a liquid sealing part is reduced to improve the reliability.
Inventors:
YOSHIKAWA HIROKI
NUMATA TORU
MORI SHIGERU
HIRATA KOJI
JITSUKATA HIROSHI
NUMATA TORU
MORI SHIGERU
HIRATA KOJI
JITSUKATA HIROSHI
Application Number:
JP9551788A
Publication Date:
October 26, 1989
Filing Date:
April 20, 1988
Export Citation:
Assignee:
HITACHI LTD
International Classes:
H01J29/89; H01J7/26; H01J31/10; H04N5/74; (IPC1-7): H01J7/26; H01J29/89; H04N5/74
Attorney, Agent or Firm:
Katsuo Ogawa (1 person outside)