KR20030006878A - Control system of zoom lens for digital still cameras - Google Patents

Abstract

PURPOSE: A control system for a zoom lens of a digital still camera is provided to control the zoom lens by using data programmed in a micro-controller unit and to control auto-focusing of the zoom lens by using an electronic control distance measuring system or receiving the electronic signal with simple mechanism. CONSTITUTION: A control system of a zoom lens in a digital camera is composed of an assembling base(14); a first front lens group(1) combined with a lens barrel and arranged in the front of a zoom lens assembly; a second lens group(2) combined with the lens barrel; a first screw bearing(3) formed in the lens barrel; a first position stabilizing unit(5) restricting rotation of the lens barrel; a first stepping motor(6) driving the second lens barrel; a first screw rod(7) connected to the shaft of the first stepping motor, and engaged with the first screw bearing; a third lens group(8) combined with the lens barrel; a second screw bearing(9) formed in the third lens barrel; a second position stabilizing unit(11) restricting rotation of the third lens barrel; a second stepping motor(12) driving the third lens barrel; and a second screw rod(13) combined with the second stepping motor shaft and engaged with the second screw bearing.

Description

CONTROL SYSTEM OF ZOOM LENS FOR DIGITAL STILL CAMERAS}

The present invention controls the zooming of a lens for a digital still camera by receiving an electronic signal from a microcontroller unit (MCU) in which a program for zoom lens movement based on lens design data is stored. An electronically controlled distance measuring system or a system for controlling auto-focusing of a zoom lens using the same mechanism that drives the zooming of the lens by receiving an electronic signal (pulse) from the MCU.

In the case of digital still cameras, the zoom lens is typically such that the first lens group or front (front) lens element fixed at the leading position of the zoom lens assembly is immovable. The second lens group and the third lens group are simultaneously moved such that the entire lens acts as a zoom lens. The movement of the second lens group and the third lens group acts as a zoom lens by changing the focal length continuously in a straight line. From the wide angle (shortest focal length of the lens) to telephoto (longest focal length of the lens) the two groups of lenses must be moved correspondingly. The movement stroke of two groups of lenses from one focal length position to another is determined by the design of the lens. Typically the movement strokes of these two lens groups are mechanically controlled by a cam (which in most cases is a home cam).

1 is a typical design of a zoom lens for a digital still camera having a zooming ratio of 2X (2x). As shown in Fig. 1, the first lens group 1 is fixed in the front (front) position and does not move. The second lens group 2 and the third lens group 3 move back and forth according to the change of focal length, and the lines 4 and 5 represent the movements (tracks) of these two groups. The straight line 4 represents the movement of the second lens group 2, and the curve 5 represents the movement (track) of the third lens group 3. Each group moves simultaneously corresponding to each other while following a predetermined track from one focal length to another focal length. In FIG. 1, five focal length points are shown as an example of the zooming position. Position # 1 is 11.0 mm focal length (longest telephoto position), # 2 is 9.615 mm focal length, # 3 is 8.319 mm focal length, # 4 is 6.913 mm focal length, and # 5 is 5.505 mm The position of two lens groups at the focal length (shortest wide-angle position) is shown.

In order for the two lens groups to effectively perform the corresponding movement, a mechanism with a groove cam is typically used. 2A and 2B show a conventional mechanical control system of a zoom lens having six groove cams. One lens group is controlled by three sets of groove cams of the same curve and dimensions provided on the periphery of the outermost lens barrel (tube for holding the entire lens assembly), and the same curve provided on the same periphery of the lens barrel; The other three groove cam sets of dimensions control different lens groups.

The first groove cam set 6 provided on the outermost lens barrel 7 controls the second lens group 2, and the second groove cam set 8 provided on the outermost lens barrel 7 3 Controls the lens group 3. A gear tooth 9 is provided at the bottom edge of the outermost lens barrel 7, which meshes with the drive gear 10 of the stepping motor 11. When the zooming switch is turned on, the stepping motor 11 starts to rotate, and then the outermost lens barrel 7 starts to rotate. While the outermost lens barrel 7 is rotating, the groove cams 6 and 8 also move, and two lens groups 2 and 3 are also fixed on the lens barrel of each lens group and inserted into the slots of the groove cam. It moves back and forth (up and down) by the movement of the pin 12 which moves along the curve of the groove | channel cam 6,8. The curves of the groove cams 6, 8 must be precisely designed in accordance with the design data of the zoom lens, i. The direction of lens movement (front or rear) is determined by the stepping motor rotation direction.

In this kind of mechanical zooming control, the home cam requires high precision, and it is very difficult to manufacture a lens barrel having such a precise groove cam, and as a result, the cost of such precision parts and components is quite expensive. Assembly and alignment of lenses with such control mechanisms are also quite difficult.

Moreover, in order to automatically focus the lens (so-called 'auto focusing') it is usually necessary to adjust the position of one group of lens groups irrespective of the lens zooming mechanism. When receiving a signal from an electronic distance measuring system of a digital still camera or an automatic focusing system of a MCU, one of the lens groups must move slightly back and forth. However, in the case of the mechanical cam-type zooming system described so far, this movement is physically impossible since all the moving lens groups are connected to the zooming cam mechanism. When one group of lenses starts to move, the other lens group also starts to move, and it is impossible for only one group of lenses to move independently of the zooming system. Therefore, in the case of a mechanical cam zooming system of a digital still camera, instead of driving one group of lens groups or lens elements, an image sensor such as CCD or C-MOS is moved to adjust the lens focus.

However, it is also extremely difficult to move the entire image sensor connected to the printed circuit board (PCB), which means that the image sensor must be moved with a part of the PCB or with the connecting wire.

The lens focusing of a digital still camera must be adjusted in very small increments of 1/1000 millimeters. If the focusing is adjusted by moving the image sensor, the level of the image sensor relative to the lens must also be extremely high. It must be perfectly level. This type of lens focusing method is also extremely difficult to implement compared to the method of moving a lens element or one group of lens groups that can be held in the lens barrel (tube) and can be moved smoothly and easily back and forth (up and down). The image sensor 13 is disposed immediately after the rear lens, and the image sensor is fixed on the base 14. The threaded bearing 15 is formed as part of the image sensor base 14. A stepping motor 16 is provided to drive an automatic focusing mechanism, which has a screw rod 17 which is an extension of the motor shaft. The screw rod meshes with the female screw screw provided on the inner wall of the threaded bearing 15.

When the auto focusing system is switched on, the stepping motor 16 rotates, the screw rod 17 rotates, and the threaded bearing 15 moves back and forth (up and down). Therefore, the image sensor 13 moves back and forth (up and down) regardless of the movement of the lens zooming.

The precision required for such movement of the image sensor and the adjustment of the lens focus by such a precise method must be quite difficult and even expensive if possible.

In order to eliminate the difficulty of mechanically controlling lens zooming by the cam mechanism and the difficulty of adjusting the lens focus by moving the image sensor, parts and components are much smaller, cheaper and much easier to assemble. It is desirable to have a simpler system. Accordingly, the present invention aims to provide a control system of such a zoom lens for a digital still camera.

1 shows a zoom lens for a digital still camera of a typical design, showing the moving tracks of the second and third lens groups;

2A is a perspective view of a conventional zooming control system with a cam,

2B is a perspective view of two lens groups disposed within a conventional zooming control system by a cam and assembled within each lens barrel;

3 is a perspective view of a conventional zooming control system with a cam having an automatic focusing mechanism to move the image sensor for focus adjustment.

4 is a perspective view of an example of a control system of a zoom lens for a digital still camera of the present invention;

5 is a partial cross-sectional view of an example of a control system of a zoom lens for a digital still camera of the present invention.

※ Explanation of code for main part of drawing

1: Front (first) lens group 2: 2nd lens group

3: first threaded bearing 4: second lens barrel

5: 1st position stabilization fork 6: 1st stepping motor

7: first screw rod 8: third lens group

9: second threaded bearing 10: third lens barrel

11 second position stabilization fork 12 second stepping motor

13 second screw rod 14 assembly base

15: image sensor

In the present invention, the groove cam used in the conventional zooming control mechanism is eliminated, and instead of the groove cam, two lens groups are controlled by two stepping motors, one stepping motor driving the first lens group and the other stepping. The motor drives the second lens group. Threaded bearings are formed on the barrel side as part of the lens barrel of each moving lens group. The stepping motor has a screw rod, which is an extension of the motor shaft, which meshes with a female screw screw provided on the inner wall of the threaded bearing. The screw rod supports the lens barrel with some kind of position stabilization means to stop the rotation of the lens barrel itself.

When the stepping motors start to rotate at the same time, both screw rods begin to rotate, and by the rotation of these rods, the threaded bearings are driven on the male screws of the screw rods, and as the threaded bearings move forward and backward (up and down) The two lens groups start to move back and forth (up and down) according to the motor rotation direction.

In the case of the present invention, instead of the home cam mechanically controlling the zooming of the lens, the lens movement data for controlling each lens group for each focal length position, i.e., the tracks 4 and 5 shown in FIG. The data of the lens group movement track must be programmed as electronic position signal data and stored in the MCU (micro control unit) of the digital still camera. As soon as the telephoto or wide-angle power zoom switch is turned on, the stepping motor starts to move simultaneously, and the lens groups move to control the zooming of the entire lens in the telephoto or wide-angle direction by receiving signals from the MCU according to the designed lens movement track. It starts to win.

While the telephoto or wide-angle switch is on, the MCU continues to send signals to each stepping motor to move the group of lenses from one point to another, and when the switch is turned off, the lens immediately stops at that point. The position where the lens is stopped must be remembered by the MCU, and the next time the telephoto or wide switch is turned on, the lens zooming will start at the focal length position where the lens was last stopped.

At the same time, there is no cam at all that disables lens focusing apart from the lens zooming mechanism. However, instead, one part of the zooming mechanism, one of the stepping motors, can be used to drive one group of moving lens groups. Lens focusing can be adjusted by moving one of the moving lens group, the second lens group, or the third lens group. Before and after zooming is controlled, the MCU sends a position signal to which one of the two lens groups must be placed to adjust the focus, which then causes the stepping motor to start moving and move the lens group to the desired position.

Thus, by using two stepping motors that eliminate mechanical groove cams that require extreme precision in manufacturing, zooming can be very easily controlled with only electronic signals pre-programmed and stored in the camera's MCU, and more By moving one group the automatic focusing can be adjusted by one of the two stepping motors, eliminating the extremely difficult way of moving the image sensor to perform lens focusing.

4 and 5 show an example of the control system of the invention, i.e., the zoom lens for a digital still camera, which control system is a fixed front (first) lens group (or first) at the leading position of the zoom lens assembly. Element) 1, a lens group 2 (hereinafter referred to as a 'second lens group') disposed after the first lens group, and a lens barrel 4 of the second lens group 2 (hereinafter, A threaded bearing 3 (hereinafter referred to as a 'first threaded bearing') formed as part of a two lens barrel ', a second of the second lens group 2 from the first threaded bearing 3 Position stabilizing fork 5 (hereinafter referred to as 'first position stabilizing fork') formed on the opposite side of the lens barrel 4, provided as an extension of the motor shaft, and the first screw of the second lens group 2 A screw furnace which is screwed into the bearing hole of the axial bearing 3 and engages with a screw provided in the inner wall of the bearing hole of the first threaded bearing 3. A stepping motor 6 (hereinafter referred to as a 'first stepping motor') having a rod 7 (hereinafter referred to as a 'first screw rod'), a lens group 8 arranged after a second lens group ( Hereinafter, the threaded bearing 9 (hereinafter, referred to as 'third lens group') and as part of the lens barrel 10 (hereinafter referred to as 'third lens barrel') of the third lens group 8 (hereinafter, 'Second threaded bearing', position stabilizing fork 11 (hereinafter referred to as 'second position stabilizing fork') formed on the opposite side of the third lens group 8 from the second threaded bearing 9; And screwed into the bearing hole of the second threaded bearing 9 of the third lens group 8 and provided on the inner wall of the bearing hole of the second threaded bearing 9). It consists of a stepping motor 12 (hereinafter referred to as a 'second stepping motor') with a screw rod 13 (hereinafter referred to as a 'second screw rod') that engages the screw. All these components are assembled on the assembly base 14, on which an image sensor 15, such as a CCD or C-MOS, is placed just below the rear element of the lens assembly.

The second lens group 2 is assembled in the second lens barrel 4, the second lens barrel 4 extends from the shaft of the first stepping motor 6, and as part of the second lens barrel 4. It is screwed into the hole of the formed first threaded bearing 3 and is supported by a first screw rod 7 which engages with an internal thread of the first threaded bearing 3. The second lens barrel 4 is also provided as a position stabilization means of the second lens barrel 4 and is formed on the opposite side of the second lens barrel 4 from the first threaded bearing 3 and the second stepping motor ( Supported by a first position stabilizing fork 5 disposed on a second screw rod 13 extending from the shaft of 12, the second screw rod (between the ends (slots) of the first position stabilizing fork 5 ( 13) so that the second lens barrel cannot be rotated.

The second lens barrel 4 may be moved back and forth (up and down) along the rotating first screw rod 7 and the second screw rod 13.

The third lens group 8 is assembled in the third lens barrel 10, and the third lens barrel 10 extends from the shaft of the second stepping motor 12 to form part of the third lens barrel 10. It is screwed into the hole of the formed second threaded bearing 9 and is supported by a second screw rod 13 which engages with the internal thread of the second threaded bearing 9. The third lens barrel 10 is also provided as a position stabilization means of the third lens barrel 10 and is formed on the opposite side of the third lens barrel 10 from the second threaded bearing 9 and the first stepping motor ( Supported by a second position stabilizing fork 11 disposed on the first screw rod 7 extending from the shaft of 6), the first screw rod (between the ends (slots) of the second position stabilizing fork 11 ( 7) so that the third lens barrel cannot be rotated.

The third lens barrel 10 may be moved back and forth (up and down) along the rotating second screw rod 13 and the first screw rod 7.

As soon as the telephoto or wide-angle power zoom switch is turned on, the stepping motors 6 and 12 start to move simultaneously, and the lens groups 2 and 8 control the lens groups for each focal length position. Telephoto direction by receiving movement data, i.e., data of lens group movement tracks such as tracks 4 and 5 as shown in FIG. Or it starts to move to control the zooming of the entire lens in the wide angle direction.

While the telephoto switch or one of the switches or the wide-angle switch is on, the MCU continues to transmit a signal to each stepping motor (6, 12) to move the lens group from one point to another, with both lenses off. The movement of the group immediately stops at that point. The position at which both lens groups (2, 8) are stopped must be remembered by the MCU, and the next time the telephoto switch or the wide-angle switch is turned on, the lens zooming will be in the focal length position at which the lens group was stopped last time. Starts from.

As shown in Figures 4 and 5, the entire assembly is assembled on the assembly base 14, and the image sensor 15 is disposed immediately after or directly under the trailing element of the zoom lens, where the image is No focusing to move the sensor 15 is necessary. By rotating one of the two stepping motors 6, 12 alone, one of the two lens groups 2, 8 can be moved back and forth precisely, and one of the two lens groups 2, 8 can be moved. By moving alone, the lens can be properly focused with respect to the image sensor 15. Therefore, if an auto focusing signal is sent from the MCU of the digital camera to properly focus the lens using the auto focusing system of the entire lens, one of the barrels of lens barrels 4, 10 starts to move alone and the image sensor 15 If the image acquired on the image is sharply focused, it is stopped. Therefore, in the present invention, which does not use any control mechanism according to image sensor movement, one of the very stepping motors 6 and 12 used for zooming control is an auto focusing signal from the camera MCU independently of the zooming control mechanism. By receiving, one of the lens groups 2 and 8 is moved to automatically focus the zoom lens.

As described so far, in the present invention, no zooming groove cam is used, which requires a very high precision in manufacturing, and an image sensor moving mechanism for lens focusing, which has been very difficult, is not used. Instead, only two stepping motors 6 and 12 control zooming in the present invention, and one of the two stepping motors 6 and 12 can be used for automatic focusing. Thus, the overall system and mechanism of the present invention is much simpler, cheaper and easier to assemble.

Claims (8)

Zoomed by controlling zooming of the zoom lens using programmed data stored in the microcontroller unit (MCU) of the digital still camera, and receiving electronic signals (pulses) from an electronically controlled distance measuring system or MCU of the digital still camera. A control system of a zoom lens for a digital camera, which controls the automatic focusing of the zoom lens by the same mechanism used for control, (a) an assembly base which is a place where the control system of the zoom lens for the digital camera is assembled; (b) a front (first) lens group assembled within the lens barrel and disposed at a leading position of the zoom lens assembly; (c) a lens group as a second lens group assembled within the lens barrel as a second lens barrel and disposed after the first lens group; (d) a threaded bearing as a first threaded bearing formed as part of said second lens barrel of said second lens group; (e) position stabilization means as first position stabilization means for preventing the second lens barrel from rotating; (f) a stepping motor as a first stepping motor for driving the second lens barrel; (g) an extension of the motor shaft, provided on the shaft of the first stepping motor and connected to the shaft, and screwing into the bearing hole of the first threaded bearing of the second lens barrel of the second lens group; A screw rod as a first screw rod engaged with a screw provided on an inner wall of the first threaded bearing of the second lens barrel of the second lens group; (h) a lens group as a third lens group assembled within the lens barrel as a third lens barrel and disposed after the second lens group; (i) a threaded bearing as a second threaded bearing formed as part of said third lens barrel of said third lens group; (j) position stabilization means as second position stabilization means for preventing the third lens barrel from rotating; (k) a stepping motor as a second stepping motor for driving the third lens barrel; And (l) an extension of the motor shaft, provided on the shaft of the second stepping motor and connected to the shaft, and screwing into the bearing hole of the second threaded bearing of the third lens barrel of the third lens group; And a screw rod as a second screw rod engaged with a screw provided on an inner wall of the second threaded bearing of the third lens barrel of the third lens group. system. The method of claim 1, The second lens barrel is supported and stabilized by the first screw rod engaged with the first threaded bearing and the first position stabilizing means to prevent the second lens barrel from rotating while the second lens barrel moves back and forth. To allow the second lens barrel to move smoothly without any harmful rotation. The method of claim 1, The third lens barrel is supported and stabilized by the second screw rod engaged with the second threaded bearing and the second position stabilizing means to prevent the third lens barrel from rotating while the third lens barrel moves back and forth. To allow the third lens barrel to move smoothly without any harmful rotation. The method of claim 1, The second lens barrel, to which the second lens group is assembled, is connected to the first screw rod of the first stepping motor via the first threaded bearing so that the first stepping motor is connected to the micro of the digital still camera. A zoom lens for a digital still camera, wherein the second lens barrel can move back and forth (up and down) while rotating by receiving zooming data signals of a zoom lens preprogrammed and stored in the controller unit MCU. Control system. The method of claim 1, The third lens barrel, in which the third lens group is assembled, is connected to the second screw rod of the second stepping motor through the second threaded bearing, such that the second stepping motor is connected to the micro of the digital still camera. A zoom lens for a digital still camera, characterized in that the third lens barrel can move back and forth (up and down) during rotation by receiving zooming data signals of the zoom lens preprogrammed and stored in the controller unit MCU. Control system. The method of claim 1, When one of the first and second stepping motors starts to rotate, the other stepping motor also starts to rotate exactly at the same time or exactly simultaneously, so that the second and third lens groups are received from the MCU of the digital still camera. A control system for a zoom lens for a digital still camera, characterized by starting to move simultaneously in accordance with lens motion data so that all of the lens groups as a whole act as a complete zooming lens. The method of claim 1, When the first stepping motor receives an auto focusing signal from the MCU of the digital still camera, the first stepping motor starts to rotate alone and the rotation of the first stepping motor is performed until the entire zoom lens is properly focused. And moving the second lens barrel back and forth, and stopping when the first stepping motor receives a stop signal from the MCU. The method of claim 1, When the second stepping motor alone receives the auto focusing signal from the MCU of the digital still camera, the second stepping motor starts to rotate alone and the rotation of the second stepping motor when the entire zoom lens is properly focused. And moving the third lens barrel back and forth until it stops when the second stepping motor receives a stop signal from the MCU.