JPS63229440A - Zooming system - Google Patents

Abstract

PURPOSE:To eliminate the unnaturalness of image plane variation in zooming by controlling the moving speed of a movable lens in optical-axis directions so that a view angle determined by the position of the movable lens varies almost linearly to a zooming time. CONSTITUTION:The plane developed shape of a cam groove 8 is so formed that a curve obtained by a curve showing the relation between the rotational angle theta and distance (a) of a cylindrical cam 7 by R in a theta direction is nearly circle, where R is the radius of the cylindrical cam 7 and theta is its rotational angle. Then when the movable concave lens L2 is moved by using this cam groove 8, the view angle alpha of a zoom lens is nearly in direct proportion to the rotational angle theta of the cylindrical cam 7, and consequently the view angle alphavaries almost nearly. Therefore, the unnaturalness of the size of an image plane in zooming is eliminated by controlling the moving speed of the movable lens in the optical-axis directions so that the view angle of the zoom lens varies almost linearly to the zooming time.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a zooming method used in a video camera, etc., and in particular to the position of a movable lens constituting a zoom lens as the movable lens moves in the optical axis direction. Accordingly, the angle of view determined is changed approximately linearly.

(Prior Art) Conventionally, as a zoom lens, a fixed convex lens L1. Movable concave lens L2. It is generally known that the lens is composed of four groups of lenses: a movable convex lens L3 and a fixed convex lens L4.

In a zoom lens having such a configuration, for example, imaging light 1 from an object at an infinite distance 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 focused at 1, and further refracted by the movable concave lens L2 to the movable convex lens L3 so as to be equivalent to the light emitted from the first focal point F3.

Then, the imaging light 1 refracted by this movable concave lens L2
is refracted into parallel light by the movable convex lens L3, and further focused by the fixed convex lens L4 onto the captured image 1 located at the second focal point F4 of the fixed convex lens L4.

Note that the focal length of each of the lenses L1 to L4 is f1.
．． f2. f3. f4, and the focal length of this zoom lens is f.

In the zoom lens configured as described above, the movable concave and convex lens L2 is moved in the direction of the optical axis (in the six directions of arrows), and the movable convex lens 3 is moved in accordance with the movable concave lens L2. Zooming is performed by appropriately changing the focal length fo without changing the position of the origin of the lens.

In this case, the positional relationship between the movable concave lens L2 and the movable concave lens L3 is such that the distance a is between the second focus F1 of the fixed convex lens L1 and the movable concave lens L2, and the distance a between the first focus F3 of the movable convex lens L3 and the movable concave lens L2. If b is the distance from Zooming is performed by varying the distance and moving the upper movable convex lens L3.

Focusing with the zoom lens J3 as 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 adjust the imaging point. This is performed by rear lens correction to match the captured image to 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 angle of view α of the zoom lens
is not directly proportional to the rotation angle θ of the cylindrical cam, and especially when the movable concave lens L2 moves to the long focal point side, the angle of view α changes rapidly as the rotation angle θ changes.

In this case, there is a problem in that the size of the subject changes rapidly with zooming, and 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 angle of view to change approximately linearly as a movable lens constituting a 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: Provided is a zooming method characterized in that the moving speed of the movable lens in the optical axis direction is controlled so that the angle of view determined by the position of the movable lens changes approximately linearly with respect to the zooming time as shown in the figure. It is something to do.

(Function) According to the zooming method described above, the change in the angle of view α due to the movement of the movable lens changes approximately linearly with respect to the zooming time, and therefore the screen size also changes approximately. The image changes linearly, which eliminates the unnaturalness of screen changes during zooming.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4.

In this embodiment, four groups of lenses L1 as shown in FIG.
The present invention is applied to a zoom lens configured with ~L4, and a cylindrical cam that engages with a pin 6 protruding from a lens barrel 5 in which a movable concave lens L2 constituting this zoom lens is housed. By making the shape of the cam groove 8 of 7 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 arrow 6) can be increased. is made variable so that the change in the angle of view α per unit time becomes approximately constant.

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

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. 3 gear G3 is engaged.

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 represented by the rotation angle θ and the distance a 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 angle of view α of the zoom lens is approximately directly proportional to the rotation angle θ of the cylindrical cam 7, so that the angle of view α is Changes approximately linearly.

Therefore, when the rotation speed of the cylindrical cam 7, that is, the zoom drive speed is constant, the angle of view α 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 angle of view α changes linearly if the following equation holds.

Here, as is clear from FIG. 4, the angle of view α is -1H α=2m −=2mm (3).

Therefore, by substituting this equation (3) into the above equation ('2J) and finding the focal length of one aperture, in FIG.

)(:h′-f3:b, so the above equation (5) is
becomes.

Here, since it is from the above equation (1), substituting this (force equation) into the above equation (e), it becomes.

Also, in this equation (8), fl, f2. Since f3° and f4 are each constant, by setting, the above equation (8) becomes as follows.

In addition, dfo/dθ in the above equation (4) is this (1
0) Using the formula, it becomes.

Then, by substituting this equation (11) into the above equation (4), we get
becomes.

Here, since dα/dθ is constant (K1), it becomes.

Therefore, from this equation (13), becomes.

Then, by expanding the denominator on the left side of this equation (14) and integrating and solving, we get: The shape of the cam groove 8 is determined so that the relationship between a and θ satisfies this equation (15). By specifying this, the change in the angle of view α becomes 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 varies linearly with the zooming time.

Therefore, the change in the angle of view α also becomes linear with respect to the zooming time.

In addition, in the above formula (15), (2f 2 H) 2-4H<f 2 '' H+22)
-D, when D=O, it becomes.

Also, when D<O, Then, When D〉0, becomes.

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, as shown in FIG.
1 is the first to third gear G1 as in the previous embodiment,
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 G1, and this fourth gear G4 is connected to the rotary encoder 1.
It is attached to the rotation shaft 16 of No. 5. Thereby, this rotary encoder 15 outputs a position information signal S1 representing the position of the movable concave lens L2.

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. There is.

Here, the control circuit 17 detects the distance 11a in the equation (15) based on the position information signal S1, and sets the rotation speed of the pulse motor 12 based on this distance a.

In other words, the above equation <15> is calculated as follows by replacing the rotation angle θ in equation (15) with the zooming time t,...(1
It can be expressed as a place.

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 (19).

Therefore, in this embodiment. According to the distance a, that is, according to the position of the movable concave lens L2, the above (19)
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 angle of view α of the zoom lens in this embodiment with respect to the zooming time. It can be changed almost linearly.

Further, as described above, by changing the viewing angle α approximately linearly with respect to time, unnatural changes in the 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 angle of view of the zoom lens in the optical axis direction of the movable lens constituting the zoom lens so that the angle of view 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 angle of view 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. 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, f,
...Focal length, L2...Movable lens (movable concave-convex lens).稟1 fig. 7 −“− 蒃GA fig.

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 using a zoom drive, the focal length of the zoom lens being varied by the position of the movable lens. A zooming method characterized in that the moving speed of the movable lens in the optical axis direction is controlled so that the determined angle of view changes approximately linearly with respect to the zooming time.