JPS6383711A - Focusing device for zoom lens - Google Patents

Abstract

PURPOSE:To obtain a simple, precise focusing device by permitting a sampling pulse which changes in response to the position of a zoom ring to maintain an output from a charge/discharge circuit and controlling a drive part in a master lens part by said output. CONSTITUTION:The zoom ring 14 is turned to turn a cam mechanism, which advances and retreats a movable lens in a zoom lens part A. Since the cam mechanism scales the zoom ring 14 in response to the logarithm function of a focus distance in the zoom lens part A, the movable lens in the zoom lens part A advances and retreats by the logarithm function in response to the turn of the zoom ring 14. Together with the advance and retreat of the movable lens in the zoom lens part A, the position of the zoom ring 14 is detected, and a sampling pulse generator circuit 60 outputs a pulse corresponding to the position. The discharge of the charge/discharge circuit 70 in which a printing voltage varies with information about a distance to an object maintains the changing output, which drives the drive part 23. Then the movable lens in the master lens part B is drived to focus the distance. Thus the simple, inexpensive, precise focusing device can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a focusing device for 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 unit. This method is disclosed in, for example, Japanese Patent Application Laid-Open No. 186872/1983,
As shown in Japanese Patent Application Laid-open No. 52-114321, etc.,
A moving range metering circuit is provided that contains positional information of the movable lens of the master lens section, which is influenced by the focal length and subject distance, in the form of 40 types or a table, and detects the focal length to determine the position of the movable lens of the master lens section. I am trying to correct it. In general, a digital circuit is used to hold position information as a calculation formula or table.

(Problems to be Solved by the Invention) However, when a digital circuit is used, the resolution capability of the analog-to-digital conversion circuit and the digital-to-all log conversion circuit influences the control error density. Therefore, if the resolution capability is increased, the conversion circuit becomes complicated, whereas if the resolution capability is decreased, continuous control is not possible, resulting in an unsightly image. Generally, in automatic focus adjustment mode, the focal length and aperture information are entered into a servo loop and the focus is adjusted as a whole, so it is unlikely that the image will be spectacular.
Particularly in the case of manual focus adjustment, since no other correction means are included, there is a marked tendency for the image to become unsightly. Furthermore, the conversion circuit has poor stability and cannot be simplified.

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 mechanism C that moves a movable lens forward and backward by rotation, and a zoom ring 14 that rotates this cam mechanism C. A zoom lens section A in which C is 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 that moves the movable lens forward and backward, and a master lens section B that corresponds to object distance information. A charging circuit 70 in which the applied voltage changes, etc.
A sample pulse generation circuit 60 that outputs a sampling pulse that changes in accordance with the position of the zoom ring 14; and a drive unit for the master lens section B that holds the output of the charging circuit 70 using the sampling pulse; 23.

(Function) In the present invention, the zoom T:L14 is rotated to rotate the cam mechanism C, and the cam mechanism C moves the movable lens of the zoom lens section A forward and backward. At this point, since the zoom ring 14 is graduated according to the logarithmic function of the focal length of the zoom lens section A by the cam mechanism C, the movable lens of the zoom lens section A advances in a logarithmic function with respect to the rotation of the zoom ring 14. ) to speak. The position of the zoom ring 14 is detected as the movable lens of the zoom lens unit A moves back and forth, and the ripple pulse generation circuit 60 outputs a pulse in accordance with the position of the zoom ff 114, and applies a voltage in accordance with the object distance information. The output that has changed due to the discharge of the charging/discharging circuit 10 is held, and this output drives the drive section 23 to drive the movable lens of the master lens section B to adjust the focal length.

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

In Fig. 2, reference numeral 1 denotes a cylindrical base tube, and a support portion 2 is connected to the rear of the base tube 1 via an adapter or the like to the camera body.
is provided, and a cylindrical VL pipe rest is attached to the front part of the base cylinder 1 via a cylindrical fixed cylinder 3. At the front inside this lens barrel body 4 is the 12th! The first, second, and third lenses L1 . L, 2, L
A first group lens consisting of -3 is provided, and
The fourth, fifth, and
6th lens L4. L5. The second lens group as a variator consisting of L6, and the third lens group! ! The third lens as a convencator consisting of the seventh lens L7 is inserted through the T lens frame 7.
Group lenses are each 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 supported by a plurality of guide shafts 8 provided in parallel at the upper and lower parts of the lens barrel main body 4 so as to be able to move forward and backward, and the 21st!
Engagement elements 9 and 10 are protruded from the upper parts of the 1' lens frame 6 and the third group lens frame 7, and each of the engagement elements 9 and 10 form a cylinder rotatably provided concentrically within the lens barrel body 4. shaped cam tube 1
The cam barrel 11 is engaged with each of the cams FM11a, 11b, and an engager 13 protruding from the frontage groove 12 in the circumferential direction of the lens barrel body 4 is provided at the upper part of the cam barrel 11. 11b constitutes a cam mechanism C. Further, a cylindrical zoom ring 1 is provided on the rear outer circumference of the lens barrel body 4.
4 is provided rotatably concentrically, the engager 13 of the cam cylinder 11 is engaged with the inside of the zoom ring 14, and a zoom lever 15 is provided on the outside of the zoom ring 14, and A cylindrical movable barrel 1G facing the outer periphery of the fixed barrel 3 is integrally provided at the rear of the zoom ring 14.

The above-mentioned frames 11a and 11b are zoom rings 1
If the rotation angle of 4 is a logarithmic function of the focal length, that is, θ is the rotation angle, f is the focal length, and F and G are constants, then 0=F
It is formed to be logf-G.

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 01I8 via the engaging elements 9 and 10 engaged with the cams M11a and 11b,
Second group and third group lenses as movable lenses 4~
It is designed to advance and retreat 7 times.

Also, a fourth group lens frame 11 is provided at the rear inside the V1 cylinder main body 4.
A fourth lens group consisting of eighth and ninth lenses Lo and Ls is provided through the lens.

The 11th and 12th lenses L1o and L1+ are connected to the front part of the J1 cylinder 1 through the fifth group lens frame 18.

A fifth group lens consisting of L 12 is provided, and a cylindrical fixed tube 19 is integrally provided at the rear of the fifth group lens frame 18. Further, the 13th and 14th lenses L13. L14
A sixth group lens is provided to be movable in the axial direction. That is, the sixth group lens frame 20 is supported by a guide shaft 21 provided in the base barrel 1 so as to be freely forward and backward, and an operating portion 22 is provided protruding from the upper part of the sixth group lens frame 20.
This actuating section 22 is connected to a driving Ir 1124 of a linear motor 23 as a driving section provided in the base barrel 1, and is movable at the front part of the sixth group lens frame 20 facing inside the fixed barrel 19. A tube 25 is integrally provided.

Then, the linear motor 23 is driven to move the drive shaft 24 back and forth, and the sixth group lens frame 20 is moved back and forth in the axial direction along the guide shaft 21 via the operating section 22, so that the sixth group lens as a movable lens L13. It is designed to advance and retreat on L+4.

The first to ninth lenses 1 to 1-9 constitute a zoom lens section A, and the 10th to 14th lenses L+o
”-L 14 to star lens part B? 4M
has been completed.

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

As shown in FIGS. 2 and 3, the zoom ring position detection device 31 has a pair of semicircular arc-shaped electrodes 33 and 34 extending in the circumferential direction of the outer periphery of the fixed barrel 3 at the front part of the base barrel 1. They are mounted adjacent to each other in an insulated state, and the zoom ring 14 rotates in the circumferential direction of the inner periphery of the movable barrel 16 at the rear of the zoom ring 14 in a substantially semicircular manner that extends over a length of i. An arc-shaped electrode 35 is attached and can be connected to the electrodes 33 and 34 of the fixed cylinder 3! Two variable capacitors 36 and 37 are arranged opposite to the electrode 35 of the cylinder 16 with a gap of 9 mm.
It consists of

As shown in FIGS. 2 and 4, the master lens position detection device 32 includes a pair of cylindrical electrodes 38.
39 are attached in an insulated state adjacent to each other, and a cylindrical electrode having a width equal to or larger than the amount of movement of the sixth group lens frame 20 is provided on the outer periphery of the movable cylinder 25 at the front part of the 68th lens frame 20. 40 is attached to the fixed cylinder 19. The fi pole 38.39 and the electrode 40 of the movable cylinder 25 are arranged oppositely with a gap of 9 mm, and the two variable capacitors 41.4
2.

In addition, in FIG. 1, 51 is a square wave φ1 of opposite polarity;
This basic signal generation circuit 51 is a reference signal generation circuit that generates φ2, a triangular wave φ;1, and a timing pulse φ4.
The output end of the square wave φ1 is connected to one electrode 33 inside the zoom ring position detecting device 31 via a resistor 52.
The output end of 2 is connected to the other electrode 34 inside the zoom ring position detection device 31 through a resistor 53, and the output end of the triangular wave φJ is connected between the electrode 33 and the i-pole 34 through a resistor 54.55. has been done. In addition, the zoom ring position detection device δ31
A sample pulse generation circuit 60 is connected to the outer electrode 35 . This sample pulse generation circuit 60 is connected from the output end of an amplifier 61 via a capacitor 62 to the normal input end of a U-rocross comparator consisting of an operational amplifier 63, and the inverting input end of this operational amplifier 63 is grounded. Output end is instep stable multi-by break 6
Connected to 4.

A variable voltage source 66 is variable by a distance setting means 67, and this variable voltage source 6G is connected to a charging/discharging circuit 70. This charging/discharging circuit 70 consists of a capacitor +172 and a resistor 73, which are connected in parallel through a switch 71 and one end is grounded.The output end of the timing pulse φ4 of the reference signal generating circuit 51 is connected to the switch 11. The switch 71 is opened by the timing pulse φ4. This charge/discharge circuit 70 is a sample hold circuit 75
It is connected to the. This sample bold circuit 75 is
The switch 76 is connected to a hold capacitor +177 whose -15 terminal is grounded, and the normal input end of an operational amplifier 78, which is a voltage follower connected to the output end and the inverting input end of the operational amplifier 78. The sample pulse generation circuit 60 is connected, and the switch 76 is closed by the sample pulse.

The four non-pull hold circuits 75 are connected to the lens drive circuit 81. This lens drive circuit 81
The output end of the operational amplifier 82 is connected to the driving section 23 that drives the master lens section B, and the operational amplifier 82
On the inversion input side of
A sensor 83 is connected thereto, which outputs the position of the master lens portion B in correspondence with the voltage. This lens drive circuit 81 constitutes a servo system that moves forward and backward until the voltages of the sample hold circuit 75 and the master lens position detection device 32 become equal.

Next, the operation will be explained with reference to FIG.

The image of the subject is captured by each lens of the 1st group to the 6th group.
14, and is imaged onto the film (specific image plane) of the camera body.

For decoy imaging, first, rotate the -zoom ring 14 to move the second and third lens groups forward and backward, and move the fourth, fifth, sixth, and seventh lenses L, which are movable lenses of the zoom lens section A.
4, Ls, L6. Change the magnification by advancing and retreating from L7. At this time, the zoom ring position detection neck 31 is activated. That is, when the zoom lens is at the standard focal length S, that is, at the center position of displacement, the electrode 35 of the adjustable cylinder 16 of the zoom ring 14
The opposing areas of the pair of capacitors 33 and 34 of the fixed cylinder 3 are equal, and the capacitances of the pair of variable capacitors 36 and 37 are equal. By rotating the electrode 35 together with the movable barrel 1G of the zoom ring 14, the opposing areas of the pair of electrodes 33 and 34 of the fixed barrel 3 are changed, and for example, as a telephoto focal length T, a ratio of 1a larger than that of the target state is achieved. If you make it so that one variable capacitor 36
As the capacitance of the other variable capacitor 3G increases, the capacitance of the other variable capacitor 31 decreases.On the contrary, when the wide-angle focal length W is set to a smaller magnification than the Moe state, the capacitance of the other variable capacitor 3G decreases. As injuries decrease, the capacitance R of the other variable capacitor 37 increases, and in this way, the capacitances of the pair of variable capacitors 36 and 31 change in conjunction with the displacement of the second and third group lenses. , this is the second
, output as (ff, fi) of the third group lens.Then, in order to change the magnification of the zoom lens, the zoom ring 14
When the second and third lens groups are moved by rotating the lens, the zoom ring position deviation detection device 31 outputs the moved position.

At this time, one electrode 33 is
A composite wave φ1+φ3 of a square wave φ1 and a triangular wave φ:I is applied to the electrode 34, and a composite wave φ2+φ; In this case, capacitor 36 and capacitor 1
] 37 have the same capacity, the unbalanced square waves φ1 and φ2 cancel each other out to one electrode 35, and only the triangular wave φ3 component appears. Then, the sample pulse generation circuit 60
The comparator 63 outputs a normal rotation when the voltage of the triangular wave φ3 is OV or more, and outputs an inversion when it is less than 0■.The monostable multivibrator 64 changes the output of the comparator 63 from a normal output to an inversion output. or when changing from inverted output to normal output, the sample pulse PS
Output.

Furthermore, when the zoom lens has a telephoto focal length flflT, the opposing area of the condenser 3G increases, while the opposing area of the lens 37 decreases, so the capacitance of the condenser 3G becomes smaller than the capacitance G1 of the condenser 37. Electrode 3
The voltage appearing at 5 and input to the comparator 63 is a triangular wave φ3 strongly influenced by the square wave φ1,
The voltage crosses Ov, and the comparator 63 outputs normal rotation.
Or, the time to change from inverted output to normal output is earlier than in the case of standard focal length S, and monostable multivibrator 6
4, the timing at which the sampling pulse P1 is output becomes earlier.

On the other hand, when the zoom lens has a wide-angle focal length W, the opposing area of the condenser 36 decreases, while the opposing area of the condenser 37 increases by j (9), so the condenser 36
The capacity of 0212 is smaller than that of 37, and the capacity of
The voltage appearing at 35 and input to the comparator 63 is a triangular wave φ3 strongly influenced by the square wave φ2, and the voltage crosses OV, causing the comparator 63 to switch from the normal output to the inverted output, or from the inverted output to the positive output. The timing at which the output power changes is delayed compared to the case of the standard focal length f4S, and the timing at which the sampling pulse P is output from the monostable multivibrator 63 is delayed.

When operating the above device, Mari", Distance 9Ji
A distance is set at a desired position by the setting means 61, and the variable voltage source 66 is set to a voltage value corresponding to the distance.

Then, every time the timing pulse φ4 of the reference signal generation circuit 51 is output, the switch 11 of the charging/discharging circuit 7o is closed to charge the capacitor +j12, and when the switch 71 is opened, as shown in FIG. The electric charge charged in the capacitor 12 is transferred from the capacitor 72 and the resistor 73 to the RC
Discharge occurs in the circuit, and the electric current B: decreases with an exponential function. Further, in the sample hold circuit 75, the sample pulse generation circuit G
The ripple pulse from o closes the switch 7G, and the hold capacitor 77 holds the current voltage of the capacitor 72 shown in FIG. Out)j
and inputs it to the normal rotation input terminal of the operational amplifier 82.

At this point, in the case of a telephoto focal length FI T that outputs the υ combining pulse PT quickly after the start of discharge of the capacitor 72,
A relatively high voltage is applied to the hold capacitor 17, whereas a relatively low voltage is applied in the case of a slow sampling pulse PIA. Also, the standard focal length I! In the case of the sampling pulse Ps of 1ItS, it is in the middle.

Regarding the master lens part B, when the master lens part B is at the center position, the facing area of the electrode 38 and the electrode 40 and the facing area of the electrode 39 and the electrode 4o are equal;
The capacitances M of the variable capacitor 41 and the variable capacitor 42 become equal. Also, when master lens section B moves forward,
The opposing area between the electrode 38 and the voltage VM 40 increases, and the opposing area between the electrode 39 and the ¥1 pole 40 decreases, so that the capacitance of the variable capacitor 41 becomes larger than the capacitance of the variable capacitor 42. On the other hand, when the master lens part B is retracted, the opposing area of the electrode 38 and the electrode 40 decreases, and the opposing area of the electrode 39 and the electrode 40 increases, so that the capacitance R of the variable capacitor 41 becomes larger than that of the variable capacitor. It becomes smaller than the capacity ω of 42. Then, as in the case of the zoom lens section above, the position of the master lens section B is adjusted to the variable condenser 4J41.42.
Convert the position into a voltage value.

The voltage indicating the position of the zoom lens section A is input to the positive input side of the operational amplifier 82, and is input to the inverting input side of the sensor 83 indicating the position of the master lens section B. Then, the driving section 23 moves the master lens section B back and forth in a direction in which the difference between the two inputs is eliminated by the operational amplifier 82 to focus.

The reason why the cam mechanism C of the zoom lens section A is set by a logarithmic function and the CR circuit is used is as follows. If X is the lens extension, a is the subject distance, and f is the focal length, then X=f2/a...
・・・・・・・・・・・・・・・・・・・・・・・・(1)
Furthermore, in a zoom lens in which the rotation angle θ of the zoom ring 1G is set to be a logarithmic function of the focal length f, 0-Nogf-G or 0=F'1nr-G(r, F'
, G is a constant〉・・・・・・・・・・・・・・・・・・
・・・・・・・・・(2) becomes, and when formula (2) is transformed, Inf=(θ×G)/F' ・・・・・・・・・・・・
・・・・・・・・・(3) Therefore, f=e (θ+G ”) / F', ,, ,,,
, , , , , , , , , 10. , ,,, (4
> becomes.

From equations (1) and (4), on the other hand, the discharge voltage EX after t seconds in the CR discharge circuit is:
If Eo is the initial value, EX=Eoe-t/CR・・・・・・・・・・・・・・・
(11) Also, in the CR charging circuit, t
The charging voltage EX after seconds is: Ex=Eo (1-e "CR) = Eo Eo e-t/CR...
... (Foundation), Eo-EX is EX, (Foundation)
Substituting into the formula, -t/CR, , , , , , , , , , , , , , ,
, @E)<=Eoe, and equations (6) and (2) can be expressed by similar functions.

Therefore, from equation (5) and equation (5), if we set each constant so that the lens extension ωX becomes the terminal voltage
C) can be produced as a change in .

Furthermore, the sensor 83 is not limited to one that uses the charging/discharging circuit 70 to determine the voltage based on the discharge time of the capacitor 72 as described above, but may also be a variable capacitor that outputs a higher voltage. can.

Also, if the distance setting means 67 can be replaced with a distance measuring device, automatic focusing I! i1! IJJ works are also possible.

Further, the charging/discharging circuit 70 is not limited to the circuit shown in the drawings, and the same operation can be obtained by using a well-known CR charging/discharging circuit.

〔Effect of the invention〕

According to the present invention, the charge charged in the charging circuit is discharged, the sample pulse circuit outputs sample pulses at different times depending on the position of the lens, and by changing the discharge time, a voltage corresponding to the position is output. Therefore, a simple, inexpensive, and accurate focusing device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the focusing device for a zoom lens according to the present invention, FIG. 2 is a vertical cross-sectional view of the device, and FIG.
A cross-sectional view of a part of the figure, Figure 4 is a perspective view of a part of Figure 2,
FIG. 5 is a flowchart, FIG. 6 is a diagram showing the relationship between time and voltage of the discharge circuit, and FIG. 7 is an output diagram of the sample and hold circuit. A: Zoom lens section, B: Master lens section, C.
-Cam mechanism, 14...zoom ring, 23...driver, 60
...4 non-pull pulse generation circuit, 70...charging and discharging circuit,
75...Sample hold circuit, 4°L5. l-6
, 17...Moveable lens to zoom lens part and teno second
Group, 3rd J! I'L/7", L13.L14・
- 6th group lens as a movable lens of master lens section B.

Claims (1)

[Claims] (1) A zoom lens that has a cam mechanism that moves the movable lens forward and backward by rotation, and a zoom ring that rotates this cam mechanism, and the cam mechanism is formed such that the rotation angle of the zoom ring is a logarithmic function of the focal length. a master lens section having a drive section for advancing and retracting the movable lens; a charging/discharging circuit whose applied voltage changes in accordance with object distance information; and a sampling pulse which outputs a sampling pulse which changes in accordance with the position of the zoom ring. A focusing point of a zoom lens, comprising: a sample pulse generation circuit; and a sample hold circuit that holds the output of the charging/discharging circuit using the sampling pulse and controls the driving section of the master lens section using the output. Device.