Optical: systems and elements – Lens – Fluid
Reexamination Certificate
1999-06-25
2001-02-13
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
Fluid
C359S665000
Reexamination Certificate
active
06188526
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is related to, and claims priority from, Japanese Patent Application Nos. Hei. 10-180885 and Hei. 11-106174, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates generally to variable focus lenses, and particularly to a variable focus lens device having a focal point adapted to cyclical high-speed fluctuation to deepen the device's depth of focus.
2. Discussion
A variable focus lens device having a lens member and a separate a pressuring part adjacent to the lens member is disclosed, for example, in Japanese Patent Application Laid-Open No. Hei. 8-114703.
In this variable focus lens device, a pair of pressure-measuring strain gauges and a pair of temperature-compensating strain gauges are joined to the transparent elastic film for measuring the pressure of a transparent liquid acting on a transparent elastic film and controlling the pressuring part so that this pressure approaches a target value. These pressure-measuring strain gauges and temperature-compensating strain gauges form a Wheatstone bridge circuit, and distortion of the transparent elastic film is measured on the basis of an output from this circuit. Because the focal length of the lens member lens is temperature-compensated during this measurement, if the same measured values are used to control a piezoelectric unimorph driving the pressuring part, volume fluctuations of the transparent liquid resulting from thermal expansion and contraction are also compensated.
However, this related art variable focus lens device has a complex structure because the Wheatstone bridge circuit must be formed by a pair of pressure-measuring strain gauges and a pair of temperature-compensating strain gauges. Also, because the strain gauges must be mounted at correct angles in correct positions to form the Wheatstone bridge circuit, manufacturing is difficult to automate and is therefore labor-intensive.
Nevertheless, with a variable focus lens device having a transparent liquid sealed in a closed container and not having a temperature compensation function, the focal length of the lens changes and the focus position moves when the transparent liquid thermally expands or thermally contracts due to an increase in temperature resulting from a change in the surrounding temperature or extended operation. That is, it is sometimes unavoidably necessary for the device to be provided with a temperature compensation function, because without temperature compensation precise focus positioning sometimes is difficult to obtain, depending on the environment in which a variable focus lens device is to be used and the purpose of that use.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a variable focus lens device which has both a temperature compensation capability and a simple construction which can be manufactured inexpensively with little labor.
More particularly, the present invention comprises a variable focus lens device including a lens member with a lens container having a disc-shaped transparent elastic film, a transparent sealing member disposed facing the transparent elastic film across a predetermined gap forming an internal volume, and a transparent liquid filling the internal volume. An actuator varies a focal point of the lens member by deforming the transparent elastic film by fluctuating the pressure inside the internal volume.
Also, a temperature compensator, connected to the internal volume, absorbs a temperature fluctuation component of the transparent liquid, which varies due to thermal expansion and thermal contraction. The temperature compensator has a tank whose capacity is variable and a narrow passage that, while being connected to the internal volume, essentially does not function as a flow passage with respect to sudden pressure fluctuations caused by the actuator.
According to the present invention, even when the transparent liquid filling the internal volume of the lens container thermally expands or thermally contracts due to an increase in temperature resulting from a change in the surrounding temperature or from extended operation, the temperature fluctuation component of the transparent liquid is absorbed or supplied by the temperature compensator. As a result, even without a temperature compensation circuit such as a Wheatstone bridge circuit, changes in the focal length of the lens member caused by variations in the temperature of the transparent liquid are suppressed, and an effect similar to that of when temperature compensation is carried out is obtained.
Therefore, it is possible to provide an inexpensive variable focus lens device that includes a temperature compensation capability and that is simple in construction and does not require much labor to manufacture.
REFERENCES:
patent: 5438486 (1995-08-01), McNair
patent: 1-140118 (1989-06-01), None
patent: 8-114703 (1996-05-01), None
patent: 9-230252 (1997-09-01), None
patent: 10-144975 (1998-05-01), None
Kaneko Takashi
Kawahara Nobuaki
Sasaya Takanari
Denso Corporation
Mack Ricky
Pillsbury Madison & Sutro LLP
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