Optical: systems and elements – Lens – With variable magnification
Reexamination Certificate
2003-02-18
2004-07-13
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
With variable magnification
C359S823000, C359S694000, C396S079000
Reexamination Certificate
active
06762888
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a system that controls zooming of the lens for a digital still camera (hereinafter referred to as DSC) receiving electronic signals (pulses) from micro controller unit (hereinafter referred to as MCU), in which the program of zoom lens movement based on the lens design data is written, and also relates to a system that controls auto-focusing of the zoom lens using the very mechanism which drives the zooming of the lens after receiving electronic signals (pulses) from the MCU or electronically controlled distance measuring system of the DSC camera.
2. Background Art
In DSCs, the zoom lens usually fixes the front (headmost) lens element or the first group of lenses at the headmost position of the zoom lens assembly so it will not move. The second group and the third group of lenses move at the same time to enable the whole lens to work as a zoom lens. The movements of the second and third groups of the lenses change the focal length in a straight succession so it works as a zoom lens. From wide angle (shortest focal length of the lens) to telephoto (longest focal length of the lens), the two groups of lenses must move correspondingly with each other. From one focal length position to another focal length position, the moving strokes of the two groups of lenses are determined by the design of the lens. Usually, the moving strokes of these two groups of lenses are controlled mechanically by cams, which are groove cams in most cases.
FIG. 1
shows a typical design of zoom lens with 2× (two times) zooming ratio for DSCs. The first group of lenses (
1
) is fixed at the front (headmost) position. The second group of lenses (
2
) and the third group of lenses (
3
) move back and forth according to the change of the focal length, and tracks (
4
,
5
) show the movements of these two groups. The track (
4
) (straight line) shows the movement of the second group of lenses (
2
), and the track (
5
) (curved line) shows the movement of the third group of lenses (
3
). Each of the second and third groups of lenses (
2
,
3
) moves at a time correspondingly with each other following the predetermined tracks from one focal length point to another. In
FIG. 1
, five focal length points are shown as examples of zooming positions. Position #
1
shows the positions of the two groups of lenses at the focal length of 11.0 mm (the longest, telephoto position), #
2
at the focal length of 9.615 mm, #
3
at the focal length of 8.319 mm, #
4
at the focal length of 6.913 mm, and #
5
at the focal length of 5.505 mm (the shortest, wide angle position).
To enable the two groups of lenses to carry out the corresponding movements effectively, a mechanism with groove cams is usually used. FIGS.
2
and
2
-
a
show the conventional mechanical controlling system of zoom lens, which has six groove cams. One group of lenses is controlled by one set of three groove cams of the same curve and dimensions provided on the periphery of the outermost lens barrel (a tube to hold the whole lens assembly), and the other set of three groove cams of the same curve and dimensions provided on the same periphery of the lens barrel controls the other group of lenses.
The first set of groove cams (
6
) provided on the outermost lens barrel (
7
) controls the second group of lenses (
2
), and the second set of groove cams (
8
) provided on the outermost lens barrel (
7
) controls the third group of lenses (
3
). At the bottom rim of the outermost lens barrel (
7
), the gear teeth (
9
) are provided and engaged with the driving gears (
10
) of the stepping motor (
11
). When the zooming switch is turned on, the stepping motor (
11
) starts rotating, and then the outermost lens barrel (
7
) starts rotating. While the outermost lens barrel (
7
) rotates, the groove cams (
6
,
8
) move too, and the two groups of lenses (
2
,
3
) also move back and forth (up and down) through the movements of the pins (
12
) fixed on the lens barrel of each group of lenses and inserted into the slots of the groove cams, which move according to the curves of the groove cams (
6
,
8
). The curves of the groove cams (
6
,
8
) are designed accurately according to the design data of the zoom lens, namely, according to the tracks like the tracks (
4
,
5
) shown in FIG.
1
. The direction of lens movement (back or forth) is determined by the direction of the rotation of the stepping motor.
In this kind of mechanical controlling of zooming, the accuracy of the groove cams is highly required and it is very difficult to manufacture lens barrels with such accurate groove cams, and consequently, the cost of such accurate parts and components is quite expensive. The assembling and adjustment of the lens with such controlling mechanism are also quite difficult.
Furthermore, to focus the lens automatically, so-called auto-focusing, it is usually necessary to adjust the position of one of the groups of lenses regardless of the lens zooming mechanism. Receiving signals from auto-focusing systems of the MCU or electronic distance measuring system of the DSC, one of the groups of lenses must move back and forth very slightly. However, in the case of theretofore-explained mechanical cam type zooming system, it is physically impossible because all the moving groups of lenses are connected to the zooming cam mechanism. If one of the groups of lenses starts moving, the other group of lenses starts moving too, and it is impossible for one of the groups alone to move separately from the zooming system. Therefore, in the case of mechanical cam zooming system of DSCs, the image sensor like CCD or C-MOS usually moves to adjust the lens focus instead of driving any groups of lenses or lens element.
However, it is also extremely difficult to move the whole image sensor, which is connected to the print-circuit board (PCB), and this means that the image sensor must move together with a part of the PCB or with connecting wires.
The lens focusing of the DSCs must be adjusted with a very small scale unit of a hundredth of a millimeter, and if the focusing is adjusted by moving the image sensor, the horizontality of the image sensor against the lens must also be extremely high and the image sensor must be kept perfectly even with the lens. This kind of lens focusing method is also very difficult to carry out in comparison with the method of moving the lens element or one of the groups of lenses, which are held in lens barrels (tubes) and can move smoothly and easily back and forth (up and down).
FIG. 3
shows the mechanism of focusing by moving the image sensor. The image sensor (
13
) is placed just behind the rearmost lens, and the image sensor (
13
) is fixed on the base (
14
). The threaded bearing (
15
) is formed as a part of the image sensor base (
14
). The stepping motor (
16
) is provided to drive the auto-focusing mechanism, and the stepping motor (
16
) has a screw rod (
17
) as an extension of the motor shaft. The screw rod (
17
) engages with the female-screw-thread provided at the inner wall of the threaded bearing (
15
).
When the auto-focusing system switch is turned on, the stepping motor (
16
) rotates the screw rod (
17
) such that the threaded bearing (
15
) moves back and forth (up and down). Thus, the image sensor (
13
) moves back and forth (up and down) regardless of the movement of lens zooming.
The accuracy required for such movement of image sensor and adjustment of lens focus by such a delicate method is very high, and even if it is possible, it will be quite expensive.
To eliminate the above explained difficulties of controlling lens zooming mechanically by cams and of adjusting lens focus by moving the image sensor, it is preferable to have a much simpler system with less and inexpensive parts and components, and with much easier way of assembling.
An improved control system of zoom lens for DSCs has been disclosed in U.S. Pat. No. 6,453,123 issued to Arc Design, Inc., the same assignee of the subject application. In
FIGS. 4 and 5
, the control
Arc Design, Inc.
Mack Ricky
Senniger Powers Leavitt & Roedel
LandOfFree
Control system of zoom lens for digital still cameras does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Control system of zoom lens for digital still cameras, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Control system of zoom lens for digital still cameras will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3239663