JPS62276520A - Zoom lens focusing device - Google Patents

Abstract

PURPOSE:To obtain an accurate correction value with a simple detecting device, by forming the rotational angle of a zoom ring so that the angle can become the logarithmic function of the focal distance. CONSTITUTION:By rotating a zoom ring 14 a cam cylinder 11 is rotated and the movable lens of a zoom lens section A is moved forward and backward by means of the cam grooves 11a and 11b of the cam cylinder 11. Since the zoom ring 14 is marked with the logarithmic function of the focal distance of the zoom lens section A by means of the cam grooves 11a and 11b, the movable lens of the zoom lens section A moves forward and backward in the logarithmic function against the rotation of the zoom ring 14. As the movable lens moves, the position of the zoom lens 14 is detected and squared values of the focal distances of the zoom lens section A and a master lens section B are calculated by inversely transforming the detected value into its inverse logarithmic value by means of a squared value calculating device. The signal of the squared value calculating device is used for driving a driving section 23 which drives the movable lens of the master lens section B in order to adjust the focal distance.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Object of the Invention] (Field of Industrial Application) The present invention relates to the focal point vi position of a zoom lens such as a camera.

(Prior Art) In a zoom lens in which focus is adjusted by moving a movable lens in a master lens section, even if the subject distance is constant, when the magnification is changed in the zoom lens section, the focal position of the master lens section moves. Therefore, in order to keep this focal position constant, it is necessary to calculate the focal length and automatically correct the movable lens position of the master lens section. In this method, for example, as shown in Japanese Patent Application Laid-Open No. 57-186872 and Japanese Patent Application Laid-Open No. 52-114321, a movable lens of a master lens part that is influenced by the focal length and the subject distance is used. A moving range four-way circuit is provided which stores position information in the form of a table or table, detects the focal length, and corrects the position of the movable lens in the master lens section. In general, a digital circuit is used to hold position information in the form of a division formula or a table.

(Problems to be Solved by the Invention) However, when a digital circuit is used, the resolution ability of the analog-to-digital conversion circuit and the digital-to-analog conversion circuit determines the accuracy of control. Therefore, if the resolution capability is increased, the conversion circuit will become complicated, and if the resolution capability is decreased, continuous control will not be possible, resulting in an unsightly image.

In general, in automatic focus adjustment mode, focal length and aperture information are entered into a servo loop and focus adjustment is performed as a whole, so it is unlikely that an unsightly image will result. However, especially in the case of manual focus adjustment, other Since no correction means is included, there is a marked tendency for the image to become unsightly.

The present invention was made in view of the above problems, and an object of the present invention is to provide a simple and accurate focusing device for a zoom lens.

(Structure of the Invention) (Means for Solving the Problems) A focusing device for a zoom lens according to the present invention includes a cam barrel 11 formed with cam grooves 11a and 11b for advancing and retracting a movable lens by rotation, and a cam barrel 11. Zoom ring 1 that rotates
4 and the cam groove 11a of the cam cylinder 11.

11b is a zoom lens section A formed such that the rotation angle of the zoom ring 14 is a logarithmic function of the focal length, a master lens section B having a drive section 23 for moving the movable lens forward and backward, and a position of the zoom ring 14. A square value calculation device 46 detects the detection value, performs antilogarithmic transformation on the detected value, and calculates the square value of the focal length of the zoom lens section A and the master lens section B, and the square value calculation device 46 uses the calculated value of the square II output device 46 to calculate the above value. Drive unit 23 that drives the movable lens of master lens unit B
It is equipped with the following.

(Function) In the present invention, the zoom ring 14 is rotated to rotate the cam barrel 11, and the movable lens is moved forward and backward into the zoom lens section through the cam grooves 11a and 11b. At this time, the cam groove 11a
, 11b, the zoom ring 14 is graduated according to a logarithmic function of the focal length of the zoom lens section A, so the movable lens of the zoom lens section A moves forward and backward according to the rotation of the zoom ring 14 according to a logarithmic function. The position of the zoom ring 14 is detected as the movable lens of the zoom lens section A moves back and forth.
This detected value is inversely converted into an inverse logarithm to obtain the square value of the focal length of the zoom lens section A and the master lens section B, and the drive section 23 is driven by the signal given by this square value calculation device, and the master lens section This is to drive the second lens B to adjust the focal length.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a cylindrical base barrel, and a support part 2 is connected to the rear of the base barrel 1 via an adapter or the like to the camera body.
A cylindrical lens barrel main body 4 is attached to the front part of the base barrel 1 via a cylindrical fixed barrel 3. The first, second, and third lenses L1. The 11th consisting of l-2, L:]! In addition to being equipped with a T lens, SJI
A second lens group as a variator consisting of fourth, fifth, and sixth lenses L4, Ls, and Le is inserted into the cylinder body 4 through a second lens frame 6, and a second lens group as a variator is formed through a third lens frame 7. A third lens group as a compensator consisting of seven lenses L7 is provided so as to be movable in the axial direction. That is, the second group lens frame 6 and the third group lens frame 7
are movably supported by a plurality of guide shafts 8 provided in parallel at the upper and lower parts of the lens barrel body 4, and the second group lens frame 6 and the 37th! ■An engaging element 9 is attached to the upper part of the lens frame 7.
10 is provided protrudingly, and each of the engaging elements 9 and 10 is engaged with each cam groove 11a and 11b of a cylindrical cam barrel 11 provided concentrically and rotatably within the lens barrel main body 4, and this cam Cylinder 1
An engaging element 13 protruding from the circumferential frontage groove 12 of the lens barrel main body 4 is provided on the upper part of the lens barrel body 4 . In addition, the lens barrel body 4
A cylindrical zoom ring 14 is rotatably provided concentrically on the rear outer circumference of the cam cylinder 1.
1 engager 13 is engaged, and the zoom ring 1
A zoom lever 15 is provided on the outside of the zoom ring 14, and a cylindrical movable barrel 16 facing the outer periphery of the fixed barrel 3 is integrally provided at the rear of the zoom ring 14.

The cam grooves 11a and 11b are connected to the zoom ring 14.
If the rotation angle of is a logarithmic function of the focal length, that is, θ is the rotation angle, f is the focal length, and C and D are constants, then θ-C1og
It is formed so that f+Q.

When the zoom ring 14 is rotated by the zoom lever 15, the cam cylinder 1
1 rotates, and the second group lens frame 6 and the third group lens frame 7 advance and retreat in the axial direction along the guide shaft 8 via the engagers 9 and 10 that are engaged with the cam grooves 11a and 11b. The lenses of the second group and the third group as movable lenses 4 to [7
It is designed to advance and retreat.

Further, a fourth lens group consisting of eighth and ninth lenses L[l, L9 is provided at the rear of the lens barrel body 4 via a fourth lens frame 17.

The first lens is inserted into the front part of the base barrel 1 through the fifth lens frame
0, 11th, 12th lens *o, Ln.

A fifth group lens consisting of L12 is provided, and a cylindrical fixed tube 19 is integrally provided at the rear of the fifth group lens frame 18. In addition, the 13th and 14th lenses Lt+, l-v are inserted into the base barrel 1 via the sixth group lens frame 20.
A sixth lens group consisting of the following is towed so as to be movable in the axial direction. In other words, the 61st! The T lens frame 20 is supported by a guide shaft 21 provided in the above-mentioned forest tube 1 so as to be able to move forward and backward, and an operating section 22 is provided protrudingly from the upper part of the sixth group lens frame 20, and this operating section 22 is connected to the above mfill. It is connected to a drive fi24 of a linear motor 23 as a drive unit provided therein,
and the fixed cylinder 19 is disposed in the front part of the sixth group lens frame 20.
A movable cylinder 25 facing the inside is integrally provided.

Then, the linear motor 23 is driven to move its drive shaft 24 forward and backward, and the sixth lens frame 20 is moved back and forth in the axial direction along the guide shaft 21 via the actuating section 22, thereby forming the sixth group as a movable lens. The lenses Lo and Lw are moved forward and backward.

The first to ninth lenses 1 to 9 constitute a zoom lens section, and the tenth to 14th lenses 10 to 9 constitute a master lens section B.

Further, a zoom ring position detection device 31 is provided between the base barrel 1 and the zoom ring 14, and a zoom ring position detection device 31 is provided between the base barrel 1 and the zoom ring 14.
A master lens position detection device 32 is provided between the fixed barrel 19 and the sixth group lens frame 20.

As shown in FIGS. 1 and 2, the zoom ring position detection device 31 includes a pair of semicircular arc-shaped bolts 1f! in the circumferential direction of the outer periphery of the fixed barrel 3 at the front part of the base barrel 1. 33 and 34 are installed adjacent to each other in an insulated manner, and
At the rear of the zoom ring 14, an electrode 35 having a substantially semi-circular arc shape, which has a strength greater than that of the rotation of the zoom ring 14, is attached in the circumferential direction of the inner periphery of the movable barrel 16, and the electrodes 33, 34 of the fixed barrel 3 The electrodes 35 and 116 are disposed opposite each other with a gap of 9 mm, forming two variable capacitors 36 and 37.

As shown in FIGS. 1 and 3, the master lens position 5 detection device 32 includes a pair of cylindrical electrodes 38 and 39 extending in the axial direction of the inner circumference of the fixed barrel 19 at the front part within the base barrel 1.
are mounted adjacent to each other in an insulating state, and a cylindrical electrode 40 having a width greater than the movement width of the sixth nT lens frame 20 is provided on the outer periphery of the movable cylinder 25 at the front part of the sixth group lens frame 20. are attached, and the electrodes 138 and 39 of the fixed cylinder 10 and the electrode 40 of the movable cylinder 25 are disposed opposite to each other with a gap of 90 degrees between them to form two variable capacitors 41 and 42.

Further, as shown in FIG. 4, the zoom ring position detecting device 31 is connected to an anti-logarithmic conversion circuit 45, and the zoom ring position detecting device @31 and the anti-logarithmic converting circuit 45 are connected to a square rectifier 46. It consists of In addition, manual distance setting device 4
7 and the automatic focus adjustment circuit 48 are connected to a multiplication circuit 50 together with the antilogarithmic conversion circuit 45 via a changeover switch 49, and this multiplication circuit 50 is connected to a comparison circuit 51 together with the master lens position detection device 32. This comparison circuit 51 is connected to the drive section 23 consisting of the linear Tanabata.

This drive unit 52 is a master lens position detection device! A servo system is constructed that advances and retreats until the value of 32 becomes equal to the value from the above-mentioned Kakeren circuit 50.

Next, the operation will be explained.

The image of the subject is captured by each lens from the 1st group to the 6th group.
14, the image is formed on the film of the camera body.

For positive mode, first rotate the zoom ring 14 to
The fourth, fifth, sixth and seventh lenses L4, which are movable lenses of the zoom lens section A, advance and retreat the group and the third group lens.
．． L5. Move Le and L7 forward and backward to change the magnification. On this occasion,
The zoom ring position detection device @31 is activated. That is, when the zoom lens is at the center of displacement, the zoom ring 14
The opposing areas of the pair of electrodes 33, 34 of the fixed cylinder 3 with respect to the electrode 35 of the capacitor a12-16 are equal, and the capacitances of the pair of variable capacitors 36, 37 are equal, respectively.

Then, by rotating the electrode 35 together with the movable n1G of the zoom ring 14, the pair of electrodes 33 and 34 of the fixed barrel 3 are rotated.
For example, when the opposing areas of the two variable capacitors 36 and 36 are changed to a larger magnification than the previous state, the capacitance a of one variable capacitor 36 increases, and the capacitance 6ffi of the other variable capacitor 37 decreases, causing the opposite effect. When the magnification is set to be smaller than the previous state, the capacitance of one variable capacitor 36 decreases and the capacitance of the other variable capacitor 37 increases, and in this way, the second group,
31 for the displacement of the third group lens! As a result, the capacitance of the pair of variable capacitors 36 and 37 changes, and this is output as the position of the second and third group lenses. Then, when the magnification of the zoom lens is changed, the zoom ring position detection device 31 outputs the position.

At this time, the rotation angle of the zoom ring 14 is the logarithm II of the focal length.
Qr11, that is, if θ is the rotation angle of the zoom ring 140, f is the focal length, and C and D are constants, θ−C1oof+
Since the cam grooves 118 and 11b are formed so as to be D, the voltage value that changes with the rotation angle of the zoom ring 14,
The current value is also a logarithmic function. Then, the detection value of the zoom ring position detection device 31 is doubled, and the inverse logarithmic conversion circuit 4
5, the square of the focal length f2 can be obtained.

In addition, the manual distance setting device 47 or the automatic focus adjustment circuit 4
8 inputs the reciprocal (1/a) of either one of the distance information to the multiplication circuit 50 via the changeover switch 49 together with the square of the focal length f2 output from the anti-logarithm conversion circuit 45, and the multiplication circuit 50 A signal (f2/a) that is the product of the reciprocal of the distance information (1/a) and the square of the focal length (2) is output. Master lens part B
A comparator circuit 51 compares the output signal corresponding to the position of .

That is, when the master lens position detection device 23 is at the center of displacement, the movable barrel 25 of the sixth group lens frame 20
A pair of electrodes 38 and 39 of the fixed cylinder 19 for the electrode 40 of
A pair of variable capacitors 41 and 42 whose opposing areas are equal
have the same capacitance. By moving the electrode 40 forward and backward together with the movable cylinder 25, the opposing areas of the pair of electrodes 38 and 39 of the fixed cylinder 19 change, for example.
When the subject distance is short and the sixth group lens is moved to a position more forward than the previous position, the capacitance of one variable capacitor 41 increases and the capacitance of the other variable capacitor 42 decreases, and conversely, When the subject distance is long and the sixth group lens is placed at a position rearward from the position of the moe, the capacitance of one variable capacitor 41 decreases, and the capacitance ω of the other variable capacitor 42 increases. Master lens part B
When the position of the 6th group lens is at a position corresponding to a subject distance that is closer than the position corresponding to the subject distance, a signal indicating that the position of the 6th group lens is moved back toward the camera body is sent; If the position corresponding to the subject distance is farther than the position corresponding to the distance, a signal indicating that the position of the sixth group lens should be advanced toward the subject side is output to the drive section 23, and this drive section 23 moves the sixth group lens. advance or retreat. This drive unit 23 receives the output signal of the master lens position detection device 32.
The sixth lens group of the master lens unit B is accurately set at a position corresponding to the subject distance by driving forward and backward until the value and the output signal value of the multiplication circuit 50 become equal, or by repeating forward and backward driving.

The reason for determining the square value of the focal length is as follows. If a is the subject distance, b is the imaging distance, and f is the focal length, the basic optical formula is (1/a) + (1/b
) = (1/f), and the lens cannot be suspended due to the Δ work, so b = f + A work. If we rearrange these equations, we can see how the lens extends? ΔX is Ax=f2/(a-
f), and since a) f, Δwork = (f2
/a), that is, the lens extension half is proportional to the square of the focal length. By detecting the square of the focal length f2 in this way, the distance can be calculated in an analog manner using a simple arithmetic circuit. Therefore, if it is recommended to use a linear sensor such as a potentiometer to detect the amount of rotation of the zoom ring 14, which is advantageous in terms of cost,
If there is a proportional relationship between the focal length display shown in 4 and the rotation angle of the zoom Ifi 14, the square value of the focal length can be easily obtained by inputting the obtained output & to the square value calculation device 46 which simply squares the obtained output &. f2 is obtained.

However, in general, in a zoom lens, the change m of the variator must be increased as the focal length becomes shorter on the wide-angle side. The angle needs to be made larger. In this way, it is impossible to simply obtain the square value of the focal length with a simple change i of the zoom ring 14.

Therefore, as shown in FIGS. 5 and 6, the zoom ring 14
The rotation angle is formed to be a logarithmic function of the focal length.

According to the above embodiment, the rotation angle of the zoom ring 14 can be detected by the simple zoom ring position detection device 32 as the focal length m + 1III, which is converted directly into a logarithmic function. For this reason,
From this detected value, the square value of the focal length can be easily calculated. The T lens position 6 can be instructed to the camera using an analog signal.

In addition, by calculating backwards from the position of the 6th group lens of the master lens section B, the subject distance can be calculated, and it is easy to display which distance, for example, between oo and 1 m is in focus, and automatically Convenient when in focus adjustment mode. Further, in the above embodiment, the detection value of the zoom ring position detection device 31 is doubled and subjected to antilogarithmic transformation in the antilogarithmic conversion circuit 45 to obtain the square of the focal length f2. By mechanically setting the rotation angle of 14 to twice the logarithmic function, the antilogarithmic conversion circuit 45 may perform antilogarithmic conversion to obtain the square of the focal length r2. Furthermore, the zoom ring position detecting device 31 and the master lens position detecting device 32 are not limited to convex electrostatic capacitors, but may be ordinary potentiometers. Also, the zoom lens section A has a zoom f
As long as the rotation angle of f114 is configured to be a logarithmic function of the focal length, it is not limited to the illustrated configuration, and other variable magnification function configurations may be used.

〔Effect of the invention〕

According to the present invention, since the rotation angle of the zoom ring is formed to be a logarithmic function of the focal length, an accurate correction value can be given by a simple detection device, and a simple, inexpensive, and accurate measurement can be performed. A focusing device δ can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the focal point Hk'J of the zoom lens of the present invention, FIG. 2 is a sectional view of a part of FIG. 1,
3 is a perspective view of a part of FIG. 1, FIG. 4 is a circuit block diagram, FIG. 5 is a developed view of the cam cylinder of FIG. 1, and FIG. 6 is an explanatory diagram of the cam groove. A: Zoom lens section, B: Master lens section, 11
...Cam cylinder, 11a, 11b -- cam) Toma, 14
...Zoom ring, 23.. Drive section, 31.. Zoom ring (detection device), 45.. Anti-logarithm conversion device, 46.. Square value extraction device, La, Ls, La, L7... Zoom The second group as a movable lens of the lens part Δ, the 351' lens,
Ln, Lw...6th group lens as a movable lens of master lens section B. e-turn qc6 J

Claims (1)

[Claims] (1) It has a cam barrel with a cam groove that moves the movable lens forward and backward by rotation, and a zoom ring that rotates this cam barrel, and the rotation angle of the zoom ring is a logarithmic function of the focal length of the cam groove of the cam barrel. a master lens section having a drive section for moving the movable lens forward and backward; a master lens section that detects the position of the zoom ring and performs anti-logarithmic conversion on the detected value; A zoom lens comprising: a square value calculation device that calculates the square value of the focal length of the lens portion; and a drive portion that drives the movable lens of the master lens portion using the calculated value of the square value calculation device. focusing device.