US005994699A [ii] Patent Number: 5,994,699 [45] Date of Patent: Nov. 30,1999
[54] THERMAL CAMERA FOR INFRARED IMAGING
[75] Inventor: Keiichi Akagawa, Kamakra, Japan [73] Assignee: Nikon Corporation, Tokyo, Japan
[21] Appl. No.: 08/975,174
[22] Filed: Nov. 20, 1997
[30] Foreign Application Priority Data
Nov. 25, 1996 [JP] Japan 8-313506
[51] Int. C I. H01L 27/16
[52] U.S. CI 250/332; 250/338.1
[58] Field of Search 250/332, 330,
250/334, 338.1, 339.02; 327/350
[56] References Cited
U.S. PATENT DOCUMENTS
Thermographic infrared cameras are disclosed that comprise an infrared image sensor having linearly positioned thermosensing elements. A physical property ol each thermosensing element changes in proportion to a corresponding temperature change caused by infrared irradiation incident on the thermosensing element. The infrared image sensor comprises a read device that reads signals from each thermosensing element in an ordered manner. A logarithmic converter receives signals from the infrared image sensor and outputs corresponding logarithmic values ol the signals. An image information output device receives the logarithmic values from the logarithmic converter and outputs a corresponding infrared image. Such thermographic infrared cameras can lurther comprise a relerence infrared image sensor. The relerence infrared image sensor includes relerence thermosensing elements each having a physical property that exhibits a change in value in proportion to a temperature change ol the respective thermosensing element. A compensating logarithmic converter outputs a logarithmic value ol the ratio ol the signal read by the infrared sensor and the signal read by the relerence infrared sensor. An image information output device receives the logarithmic values output by the compensating logarithmic converter and outputs corresponding infrared image information.
20 Claims, 8 Drawing Sheets
