Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2000-01-28
2002-04-16
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S682000, C359S691000, C359S708000, C359S733000
Reexamination Certificate
active
06373640
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to optical systems for digital cameras and, in particular, to optical systems which permit through-the-lens (TTL) viewing of a scene to be digitally recorded (photographed).
BACKGROUND OF THE INVENTION
There exists a need in the art for digital cameras having some and preferably all of the following properties:
(1) The camera is a TTL camera so that parallax problems are avoided, thus making the scene viewed by the user and the scene recorded by the camera as close to identical as possible.
(2) During picture composition (picture framing), the camera is completely optical as opposed to being a combination of an optical system and an electronic display, e.g., an LCD display. In this way, the amount of electrical current used by the camera is minimized and thus battery life is maximized. As known in the art, achieving long battery life is one of the key problems in designing a successful digital camera.
(3) The camera has a recall mode (also known as a review mode) so that the user can view previously recorded images in real time.
(4) The recall mode uses an electronic display (display unit or microdisplay) to reduce camera size and conserve battery power, but still creates a large recalled image for viewing by the user, i.e., an image which subtends a large angle at the user's eye. A large recalled image is important since it allows the user to perform recall without the need for, for example, reading glasses.
(5) The camera has a single eyepiece which is used in both the TTL and recall modes. In this way, the user can perform recall without taking his or her eye away from the position used to view the scene to be photographed.
(6) The camera is a zoom camera with a focal length range of preferably at least 2:1 and most preferably at least 3:1.
(7) The camera is ergonomic and is of relatively small size both during use and storage.
(8) Although being small in overall size, the camera has a large zoom space thus allowing the use of a negative-positive (NP) relaxed zoom objective lens.
(9) The camera has a mechanical construction which is compatible with production of high quality images. In the past, many digital cameras have employed the classical layout of film cameras, namely, a layout in which the optical axis of the camera is parallel to the camera's shortest dimension. To provide for compact storage, such digital cameras have had collapsible optics, i.e., a lens barrel which was extended from the camera during picture taking and folded back into the camera during storage. For zoom lenses, it is difficult to maintain good optical performance with collapsible optics since the collapsing action compromises concentricity and accurate positioning of the optical elements making up the lens.
(10) To reduce manufacturing costs, the camera's optical system employs relatively few optical elements and is designed to have a low sensitivity to manufacturing variations (tolerances).
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the invention to provide digital cameras which have some and preferably all of the above features. It is also an object of the invention to achieve the foregoing object through optical systems that are suitable for integration with a digital camera's electronic components in an overall small package.
To achieve the foregoing and other objects, the invention in accordance with a first aspect provides an optical system which can be switched between a first optical path (
1
) and a second optical path (
2
), said system comprising:
(A) an objective lens unit (
10
) having a positive optical power;
(B) an erector lens unit (
12
) having a positive optical power;
(C) an eye lens unit (
13
) having a positive optical power;
(D) a display unit (
16
); and
(E) optical means (
17
,
18
) for switching the optical system between said the first (
1
) and second (
2
) optical paths;
wherein:
(i) the first optical path (
1
) comprises, in order, the objective lens unit (
10
), the erector lens unit (
12
), and the eye lens unit (
13
); and
(ii) the second optical path comprises, in order, the display unit (
16
) and the eye lens unit (
13
).
In accordance with a second aspect, the invention provides an optical system which can be switched between a first optical path (
1
), a second optical path (
2
), and a third optical path (
3
), said system comprising:
(A) an objective lens unit (
10
) having a positive optical power;
(B) an erector lens unit (
12
) having a positive optical power;
(C) an eye lens unit (
13
) having a positive optical power;
(D) a sensor unit (
15
);
(E) a display unit (
16
); and
(F) optical means (
17
,
18
) for switching the optical system between said first (
1
), second (
2
), and third (
3
) optical paths;
wherein:
(i) the first optical path (
1
) comprises, in order, the objective lens unit (
10
), the erector lens unit (
12
), and the eye lens unit (
13
);
(ii) the second optical path (
2
) comprises, in order, the display unit (
16
) and the eye lens unit (
13
); and
(iii) the third optical path (
3
) comprises, in order, the objective lens unit (
10
) and the sensor unit (
15
).
In certain preferred embodiments of the foregoing two aspects of the invention, the second optical path (
2
) comprises the erector lens unit (
12
) between the display unit (
16
) and the eye lens unit (
13
). The use of this unit in the second optical path, however, is not required since the eye lens unit (
13
) and the display unit (
16
) can be designed to operate without an erector lens unit, e.g., the display unit can display a reverted and inverted image and the magnification of the eye lens unit and/or the size of the display unit can be chosen so that the image of the display unit produced by the eye lens unit subtends a sufficiently large angle at the user's eye for ready viewing of recalled pictures.
In other preferred embodiments of the foregoing two aspects of the invention, the system further comprises an image size adjusting lens unit (
11
) located in the first optical path (
1
) between the objective lens unit (
10
) and the erector lens unit (
12
).
In still further preferred embodiments of the foregoing two aspects of the invention, the optical system has an optical axis (
1
,
2
) which lies in a single plane for the first optical path (
1
) and the second optical path (
2
).
In certain preferred embodiments of the second aspect of the invention, a sensor lens unit (
14
) is located in the third optical path (
3
) between the objection lens unit (
10
) and the sensor unit (
15
) and serves to reduce the sensitivity of the system to manufacturing variations.
In accordance with a third aspect, the invention provides an optical system comprising:
(A) a zoom objective lens unit (
10
) which has a long conjugate and a short conjugate and, in order from said long conjugate to said short conjugate, comprises:
(i) a first lens unit (U
1
) having a focal length fi, said first lens unit comprising two lens elements, each of which has two aspherical surfaces;
(ii) a second lens unit (U
2
) that moves to effect a change in the optical power of the zoom objective lens unit, said second lens unit having a focal length f
2
and comprising two lens elements, each of which has two aspherical surfaces; and
(iii) a sensor lens unit (
14
); and
(B) a sensor unit (
15
) adjacent to the sensor lens unit (
14
). In accordance with a fourth aspect, the invention provides a zoom lens (
10
) which has a long conjugate and a short conjugate and, in order from said long conjugate to said short conjugate, comprises:
(a) a first lens unit (U
1
) having a focal length f
1
, said first lens unit comprising two lens elements, each of which has two aspherical surfaces; and
(b) a second lens unit (U
2
) that moves to effect a change in the optical power of the zoom lens, said second lens unit having a focal length f
2
and comprising two lens elements, each of which has two aspherical surfaces;
wherein:
f
1
<0,
f
2
>0, and
|f
1
|/f
2
<1.
In certain pre
Betensky Ellis I.
Raschke Alex
Raschke Klaus G.
Concord Camera Corp.
Klee Maurice M.
Schwartz Jordan M.
LandOfFree
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