JPS63167335A - Zooming system - Google Patents

Abstract

PURPOSE:To obviate unnaturalness due to zooming on a screen by controlling the moving speed of a movable lens in its optical axis direction so that a focal distance is changed approximately linearly to zooming time. CONSTITUTION:When a motor 9 is rotated at a constant speed and a cylindrical cam 7 is rotated by zooming drive, a mirror barrel 5 is guided by cam groove 8 together with a movable convex lens L2 and moved in them optical axis direction. When it is defined that the radius of the cylindrical cam 7 is R and a rotational angle theta is expressed by radian, the planely developed shape of the cam groove 8 formed so as to be approximately the same as a curve obtained by expanding a curve expressing relation between the rotational angle thetaof the cam 7 and a distance (a) R times. At the time of moving the lens L2 by means of the cam groove 8, the focal distance f0 of a zoom lens is approx imately proportioanl to the rotational angle theta of the cam 7 and is approximately linearly changed. When the rotational speed of the cam 7 is fixed, the focal distance f0 is approximately linearly changed in accordance with the elapsed. Consequently, an unnatural change due to zooming in the size of the screen can be obviated.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a zooming method used in a video camera, etc., and in particular, to a zooming method used in a video camera, etc. The focal length is changed approximately linearly.

(Prior Art) As shown in FIG. 4, a zoom lens has been generally known which is composed of four groups of lenses: a fixed convex lens Li, a movable concave lens L2, a movable convex lens L3, and a fixed convex lens L4. There is.

In a zoom lens having such a configuration, for example, the carried image light 1 from an object at infinity enters the fixed convex lens L1 as parallel light, and the second focal point F of this fixed convex lens L1 is
The light is refracted so as to be converged at 1, and further refracted by the movable concave lens L2 so as to be equivalent to the light emitted from the first focal point F3 of the movable convex lens L3.

Then, it was refracted by this movable concave lens L2! ! The withdrawn light 1 is refracted by the movable convex lens L3 to become parallel light, and is further focused by the fixed convex lens L4 onto the image plane 1 located at the second focal point F4 of the fixed convex lens L4. It has become.

Note that the focal length of each of the lenses L1 to L4 is f1.
．． f2. r3. r, and the focal length of this zoom lens is rll.

In the zoom lens configured as described above, by moving the movable concave lens L2 in the optical axis direction (in the six directions of arrows) and moving the movable convex lens L3 in accordance with the movable concave lens L2, the zoom lens Zooming is performed by appropriately changing the focal path @fo without changing the imaging position.

In this case, the positional relationship between the movable concave lens L2 and the movable convex lens L3 is such that the distance between the second focal point F1 of the fixed convex lens L1 and the movable concave lens L2 is a, and the distance between the first focal point F3 of the movable convex lens L3 and the movable concave lens is a. The distance L2 is determined so as to satisfy the following equation, and the path 1illa is varied to move the position of the movable concave lens L2, and along with this movement, the distance L2 is determined so as to satisfy the equation (1). Zooming is performed by varying the path 1b and moving the movable convex lens L3.

In addition, focusing in the zoom lens described above involves front lens correction by moving the fixed convex lens L1 to move the second focal point F1 of the fixed convex lens L1, or by moving the fixed convex lens L4 to change the imaging point to @image. This is done by correcting the rear lens to match surface 1.

(Problems to be Solved by the Invention) In the conventional zoom lens, the movable concave lens L2 and the movable convex lens L3 are moved in the optical axis direction by, for example, a cylindrical cam mechanism, and the position of the movable concave lens L2 is When expressed as the distance a, this distance a and the rotation angle θ of the cylindrical cam had a linear proportional relationship as shown in FIG.

However, in such a case, the focal length f of the zoom lens and the rotation angle θ of the cylindrical cam are not directly proportional, and especially when the movable concave lens L2 moves to the long focal point side, the rotation angle θ As the focal length fo changes, the focal length fo changes rapidly.

In this case, the size of the subject with respect to the same angle of view changes rapidly, resulting in a problem that screen changes during zooming become unnatural.

(Means for solving the problems) The present invention has been made in view of the above-mentioned circumstances,
It is an object of the present invention to provide a zooming method capable of eliminating unnaturalness of the screen during zooming by causing the focal length to change approximately linearly as a movable lens constituting the zoom lens moves.

In order to achieve the above object, the present invention provides a zooming method in which the focal length of the zoom lens is varied by driving a movable lens constituting the zoom lens in the optical axis direction, comprising: As shown in the figure, there is provided a zooming method characterized in that the moving speed of the movable lens in the optical axis direction is controlled so that the focal length fo changes approximately linearly with respect to the zooming time.

(Function) According to the zooming method described above, since the change in the focal length "0" caused by the movement of the movable lens changes approximately linearly with respect to the zooming time, the change in the screen size also approximately changes. The image changes linearly, which eliminates the unnaturalness of screen changes during zooming.

(Example) Below, preferred embodiments of the present invention are shown in Figure 1. This will be explained in detail using FIG.

In this embodiment, four groups of lenses L! as shown in FIG. 4 are used.
The present invention is applied to a zoom lens constituted by L4, and a cylindrical cam 7 that engages with a pin 6 protruding from a lens barrel 5 housing a movable concave lens L2 constituting this zoom lens. By making the shape of the cam groove 8 into a predetermined curve, when the rotational speed of the cylindrical cam 7, that is, the zoom drive speed is constant, the moving speed of the movable concave lens L2 in the optical axis direction (in the direction of the six arrows) can be controlled. It is variable so that the change in focal length "0" per unit time is approximately constant.

That is, the lens barrel 5 is slidably inserted into the cylindrical cam 7, and the pin 6 protruding from the outer periphery of the lens barrel 5 is inserted into the cam groove formed on the inner periphery of the cylindrical cam 7. It is engaged with 8.

Further, a first gear G1 is carved on the outer peripheral surface of the cylindrical cam 7, and this first gear G1 is rotated by a power zoom motor 9 via a second gear G2. It meshes with No. 3 gear G3.

Then, by rotating the motor 9 at a constant speed and driving the zoom, the cylindrical cam 7 is rotated, whereby the lens barrel 5 is guided by the cam groove 8 together with the movable concave lens L2 and moved in the optical axis direction. It looks like this.

Here, in this embodiment, the planar development shape of the cam groove 8 is the rotation angle θ of the cylindrical cam 7 and the distance a shown in FIG.
The shape is approximately the same as the curve obtained by multiplying the curve representing the relationship by 8 in the θ direction.

When the movable concave lens L2 is moved using such a cam groove 8, the focal length of the zoom lens is
0 is approximately directly proportional to the rotation angle θ of the cylindrical cam 7, and the focal length to changes approximately linearly.

Therefore, when the rotation speed of the cylindrical cam 7, that is, the zoom drive speed is constant, the focal length [0] changes approximately linearly with time.

Next, the shape of the cam groove 8 will be explained.

First, when the rotation angle θ of the cylindrical cam 7 is changed, the focal length to changes linearly if the following equation holds.

Here, when the above-mentioned focal length to is determined, in FIG. 4, it becomes as follows: 1] fo=f4 3).

Also, h:h-=f1:a, H:h-=f3:
Since b, the above equation (3) becomes.

Here, since it is from the above equation (1), substituting this equation (5) into the above equation (4) yields.

Kokote, Kono (6) type nioite, fl, f2. f3゜f
Since 4 is a constant, the above (2 equations become).

In equation (8), 1 is a constant, so if we find the relationship between a and θ that satisfies this equation 0, we get the amount of change in focal length f with respect to rotation angle θ (df/dθ)
will be constant.

Then, when this equation 0 is solved for a, the relationship between a and θ to be obtained is as follows.

Therefore, the cam groove 8 is arranged so that the distance a based on the movement of the movable concave lens L2 by the cam a8 satisfies the above equation (10) in relation to the rotation angle θ of the cylindrical cam 7.
By specifying the shape of , the change in the focal length "a" becomes approximately linear with respect to the rotation angle θ of the cylindrical cam 7.

Further, in this embodiment, since the power zoom motor 9 is rotated at a constant speed, the rotation angle θ of the cylindrical cam 7 changes at a constant speed.

Therefore, the change in the focal length fo is also approximately linear with respect to the zooming time.

Further, when the angle of view of the zoom lens is α, the screen size M can be expressed by the following formula: M=f Ota''Ronie Ql.

Therefore, when the focal point Wlfa changes substantially linearly, the screen size M also changes substantially linearly, making it possible to eliminate unnatural changes in the screen size during zooming.

Here, the relationship between the amount of change in screen size M during zooming and time is as follows: θ = ω°C
Then, it becomes .

Therefore, if df/dθ is constant in equation (12), that is, if the relationship between distance a and rotation angle θ is set so as to satisfy equation (10), the screen size M will also be approximately linear. It's going to change.

As described above, according to this embodiment, by setting the shape of the cam groove 8 of the cylindrical cam 7 to satisfy the above equation (10), the change in the focal length f with respect to the zooming time can be made approximately linear. Furthermore, the change in the screen size M over time is approximately linear.

Therefore, when the cylindrical cam 7 is rotated at a constant speed, each change in the focal length fO1 of the zoom lens according to this embodiment and the screen size M obtained using this zoom lens, that is, the size of the subject. can be made approximately linear with respect to the zooming time, and unnatural changes in the screen during zooming can be eliminated.

In addition, in this embodiment, the power zoom motor 9
Although the cylindrical cam 7 is rotated at a constant speed using the cylindrical cam 7, the same effect can be obtained even when the cylindrical cam 7 is rotated manually and driven for zooming, as long as the rotation speed is constant.

By the way, in the above embodiment, the power zoom motor 9 is rotated at a constant speed, and the cam groove 8 of the cylindrical cam 7 is rotated at a constant speed.
By making the movable concave lens L2 curved, the moving speed of the movable concave lens L2 in the optical axis direction can be varied depending on the position of the movable concave lens L2. In order to vary the moving speed, the rotational speed of the power zoom motor is changed to the movable concave lens L2.
It may be changed depending on the position.

An example in this case will be described below.

In this embodiment, the lens barrel 10 housing the movable concave lens L2 is fitted into the cylindrical cam 11 so as to be slidable only in the optical axis direction, and the cylindrical cam 11 is similar to the previous embodiment. First to third gear G1. It is designed to be rotated by pulse motors 12 for G2, G3 and power zoom.

Furthermore, a linear cam groove 13 is formed on the inner circumference of the cylindrical cam 11.
is formed, and a pin 14 protruding from the outer periphery of the lens barrel 10 is engaged with this cam groove 13.

Further, a fourth gear G4 meshes with the first gear Gl, and this fourth gear G4 is connected to the rotary encoder 1.
It is attached to the rotation shaft 16 of No. 5. As a result, the rotary encoder 15 outputs a position information signal S1 representing the position of the movable concave lens 2.

Then, this position information signal S1 is supplied to a control circuit 17, and this control circuit 17 supplies a pulse signal of a predetermined frequency to the pulse motor 12 as a motor drive signal S2 based on this position information signal S1. ing.

Here, the control circuit 17 detects the distance 111ia in the equation (10) based on the position information signal S1, and sets the rotation speed of the pulse motor 12 based on this distance @a.

That is, the above equation (10) can be expressed as follows by replacing the rotation angle θ in this equation (10) with the zooming time °C.

Then, the control circuit 17 sets the rotation speed of the pulse motor 12 so that the distance @a and the zooming time t satisfy equation (13).

Therefore, in this embodiment, the above (13)
The rotational speed of the pulse motor 12 is set and controlled so as to satisfy the formula, and the moving speed of the movable concave lens L2 in the optical axis direction is variably controlled, thereby changing the focal length f of the zoom lens in this embodiment to the zooming time. On the other hand, it can be changed approximately linearly.

And, as mentioned earlier, focal path I! By changing Ii[a approximately linearly with respect to time, unnatural changes in screen size can also be eliminated.

Note that the present invention can be applied not only to a zoom lens configured with four lens groups, but also to a zoom lens configured with five or more lens groups to obtain the above-described effects.

(Effects of the Invention) As is clear from the above description, the present invention provides a method for adjusting the focal length of the zoom lens in the optical axis direction of the movable lens constituting the zoom lens so that the focal length of the zoom lens changes approximately linearly with respect to the zooming time. By controlling the moving speed of the screen, it is possible to eliminate unnatural changes in screen size during zooming.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between the rotation angle of the cylindrical cam and the focal length and the distance (position) of the movable lens in the present invention, Fig. 2 is a sectional view showing the main part of the embodiment according to the invention, and Fig. The figure is a sectional view showing the main parts of another embodiment, FIG. 4 is a diagram schematically showing the optical system of a general zoom lens, and FIG. 5 is a diagram showing the rotation angle, focal length, and movability of a conventional cylindrical cam. It is a graph showing the relationship with the distance (position) of the lens. 7... Cylindrical cam, 8... Cam groove, 11... Cylindrical cam, 12... Pulse motor, 13... Cam groove, fO
...Focal length, L2...Movable lens (movable concave lens). θ Figure 1

Claims (1)

[Claims] A zooming method in which the focal length of the zoom lens is varied by moving a movable lens constituting the zoom lens in the optical axis direction by zoom driving, the focal length being approximately equal to the zooming time. A zooming method characterized in that the moving speed of the movable lens in the optical axis direction is controlled so as to change linearly.