Converging air lens structures

Details Converging air lens structures Converging air lens structures

2002-11-21

2004-08-31

Epps, Georgia (Department: 2873)

Optical: systems and elements

Lens

Single component with multiple elements

C359S666000, C359S739000

Reexamination Certificate

active

06785061

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to converging lens structures, and more particularly, to converging air lens structures.
BACKGROUND OF THE INVENTION
Converging lenses that are formed in glass or plastics are well known. Furthermore, the use of such a lens to relay an image in air (or vacuum) is very common.
Designers often use the so-called “Gaussian” lens formula for the paraxial behavior of such a lens:
1
/f
=1
/s
+1
/s″
where (s) is the object distance from the lens, (s″) is the image distance from the lens, and (f) is the focal length of the lens.
For thin lenses in air for which this formula is valid, it is also known that the focal length is related to the (thin) lens parameters by the following equation:
1
/f
=(
n
−1)(1
/r
1
−1
/r
2
)
where (r
1
) is the first surface radius of curvature, (r
2
) is the second surface radius of curvature, and (n) is the refractive index of the lens material (typically 1.5).
With practical lenses, it is not often true that the lens can be considered ‘thin’ so it is usually required to take the real central thickness of the lens into account.
The focal length formula then becomes:
1
/f
=(
n
−1)(1
/r
1
−1
/r
2
)+(
n
−1)2


*(
tc
/(
r
1
r
2
))
where (tc) is the lens central thickness.
In imaging systems, particularly those which are intended to image a significant angular field of view, it is necessary to provide an aperture stop to limit the rays which can propagate through the lens, and to control certain aberrations of the off-axis images, such as coma, astigmatism, distortion and field curvature.
Systems, which have two groups of elements about a centrally located stop, are quite beneficial for such wider field imaging. Certain lenses are known where a single thick lens can provide good wide-angle imaging provided the lens contains an aperture stop imbedded in the lens material.
A classical example of this type of lens is the Coddington magnifier. The Coddington magnifier is often used as a postage stamp magnifier. This lens is formed from a complete sphere of glass with a small aperture stop located at the center of the sphere. The lens is very thick with the radii being equal and opposite, and with the thickness being twice the radius of curvature. In practice, the sphere is reduced to a cylinder with spherical end caps. Then, a groove is ground into the central plane to form an aperture stop. Thereafter, the groove is painted with a black paint, for example.
FIG. 5
illustrates a cross section of a prior art Coddington magnifier lens.
Unfortunately, the Coddington Magnifier lens is difficult to manufacture and produce in large quantities. Furthermore, internal aperture stops can be molded into plastic lenses, but it is generally inconvenient to use an internal stop even though there may be optical benefits to doing so. For example, molding an internal stop in a plastic part requires the insertion into the mold of a metal shim part containing the stop. This procedure would normally be a manual type process step, which is not desirable from a manufacturing standpoint. Alternatively, an expensive automation would be required to insert the stop element every time a mold is opened, and a new shot run.
Also the different coefficient of expansion of metals and plastics can result in built in strain in the material and the possibility of subsequent delamination.
Accordingly, it is desirable to have a lens structure that has an embedded stop that enables improved wide field imaging without the manufacturing difficulties and other negative effects of prior art lens structures with embedded stops described previously.
Based on the foregoing, there remains a need for a lens that overcomes the disadvantages set forth previously.
SUMMARY OF THE INVENTION
According to one embodiment of the present invention, converging air lens structures are described. The converging air lens structures include a first refractive medium that has a first index of refraction. A second refractive medium that has a second index of refraction is immersed in the first refractive medium. The second refractive index is less than the first index of refraction. The lens structure features converging lens properties. An aperture stop is disposed in the second refractive medium, which is preferably air.


REFERENCES:
patent: 4721373 (1988-01-01), Sugiyama
patent: 5272568 (1993-12-01), DeJager
patent: 5274503 (1993-12-01), DeJager
patent: 5808808 (1998-09-01), Yamanashi
patent: 6473238 (2002-10-01), Daniell

Affiliated with

Also associated with

Rating

Converging air lens structures does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Converging air lens structures, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Converging air lens structures will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3300730