JPH05127062A - Zooming controller for camera lens - Google Patents

Abstract

PURPOSE:To speedily zoom the camera lens while maintaining an excellent in-focus state, to reduce a noise generated by the motor for moving a master lens almost on a telescopic side, and to make no unnatural variation in field angle in the zooming to the eliminate unnaturalness of variation of an image. CONSTITUTION:The zoom controller which holds an image formation point position, shifting as zooming operation is performed by moving the variator lens of the camera lens having no compensator lens, constant by the movement of the master lens is provided with a zoom encoder 12 which obtains position information on the variator lens, a microcomputer 13 which controls the moving speed of the variator lens according to the obtained position information, a zoom motor driver 14 and the zoom motor 15; and the moving speed is slower almost on the telescopic end side than nearby the wide-angle end side and the quantity of variation in focal distance or the shift in the image formation position is held nearly constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom control device for a camera lens such as a video camera lens.

[0002]

2. Description of the Related Art As a general zoom lens for a video camera, one shown in FIG. 5 is known. This lens is
It is composed of five lens groups, a focusing lens 1, a variator lens 2, a compensator lens 3, an erector lens 4 and a master lens 5. Among them, the focusing lens 1 functions for focusing, the variator lens 2 functions for variable focal length (zooming), and the master lens 5 functions for image formation. The compensator lens 3 is connected to the variator lens 2 by a cam mechanism (not shown), and corrects the change of the image forming point position 6 due to the movement of the variator lens 2 as described above. By this correction, the image forming point position 6 is kept at a fixed position. The variator lens 2 can be moved in the range of the arrow from the position shown by the solid line to the position shown by the broken line.

By the way, in recent zoom lenses for video cameras, the compensator lens 3 is becoming more and more popular as the size and weight of the lens are reduced. When zooming is performed with a lens that does not include the compensator lens 3 as described above, the above-described image forming point position 6 changes, so it is necessary to move the master lens 5 in accordance with this change. FIG. 6 shows zooming, that is, the amount of movement of the master lens 5 with respect to the amount of movement of the variator lens 2 (this amount of movement is approximately the image forming point position 6) with the object distance as a parameter. The information of the image forming point position 6 with respect to the moving amount of the variator lens 2 is stored in the memory, and the master lens 5 is used during the zooming operation.
Is moved by the lens control microcomputer along the curve of FIG.

The position information of the variator lens 2 is taken out as a voltage change by incorporating a variable resistor in the lens. Further, since the position of the master lens 5 is required to be highly accurate, a stepping motor is used for precise control in order to meet this requirement.

Now, as shown in FIG. 6, the moving ratio of the master lens 5 during the zooming operation is extremely large in the vicinity of the telephoto side as compared with the wide angle side. Therefore, if the variator lens 2 is moved from the telephoto side to the wide-angle side at a constant high speed in order to perform zooming quickly, the master lens 5 is required to move considerably fast near the telephoto side. In order to move the master lens 5 quickly, it is necessary to move the master lens 5 with a large number of steps in one feeding operation by the stepping motor. Since the sensitivity to the position of the master lens 5 is extremely high near the telephoto side,
If the master lens 5 is moved in a large number of steps as described above, that is, if the master lens 5 is moved a large amount at a time, there is a possibility that the focus will be out of focus.

FIG. 7 shows the focal length with respect to the moving distance of the variator lens 2. With respect to the moving distance of the variator lens 2, the change of the focal distance is extremely large near the telephoto side and the focal length near the wide angle side. It turns out that there is little change in.

[0007]

As described above, in the conventional art, when trying to zoom quickly, the master lens 5 is moved a large amount at a time, which may cause out-of-focus. Therefore, if the focus is not sacrificed, it is necessary to suppress the zoom speed to some extent, and if the zoom speed is increased, the focus must be sacrificed. Further, when trying to zoom quickly, the moving speed of the master lens 5 becomes high near the telephoto side, so that there is a drawback that the noise of the moving motor becomes large. Further, when the variator lens 2 is moved at a constant speed, the change in the focal length in the vicinity of the telephoto side becomes extremely large as shown in FIG. 7, and conversely, the change in the focal length in the vicinity of the wide angle side is small, so during zooming. There is also a drawback that the rate of change of the angle of view in is lacking in uniformity and the change of the image is unnatural.

The present invention eliminates the above-mentioned drawbacks of the prior art, and enables quick zooming while maintaining a good focus, and also reduces noise caused by the moving motor of the master lens 5 near the telephoto side. An object of the present invention is to provide a zoom control device for a camera lens which can be made smaller and which does not cause an unnatural change in an image during zooming.

[0009]

A zoom control device for a camera lens according to the present invention has a focusing lens, a variator lens, an erector lens and a master lens,
In the camera lens having no compensator lens, the variator lens is used, in which the position of the image forming point that changes as the variator lens is moved to perform a zooming operation is kept constant by the movement of the master lens. And a means for obtaining the position information of the variator lens by controlling the moving speed of the variator lens based on the position information obtained by the means so that the moving speed is slower in the vicinity of the telephoto side than in the vicinity of the wide angle side. To do.

[0010]

In the zoom control device for a camera lens configured as described above, the moving speed of the variator lens is controlled by the position information of the variator lens, and this moving speed becomes slower in the vicinity of the telephoto side than in the vicinity of the wide angle side. , It enables quick zooming while maintaining good focus, reduces the noise caused by the motor for moving the master lens near the telephoto side, and prevents the image from changing unnaturally during zooming. can do.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a camera-integrated VTR will be described below with reference to the drawings. FIG. 1 is a block diagram showing the outline of a zoom control device for a camera lens according to the present invention. In the figure, 11 is a lens, 12 is a zoom encoder, 13 is a microcomputer, 14 is a zoom motor driver, and 15 is a zoom motor. Reference numeral 16 is a control line for instructing the rotation direction of the zoom motor 15.

The position information of the variator lens in the lens 11 is taken out as a voltage change by the zoom encoder 12, and this is A / D converted to be converted into a microcomputer 13.
Read by. The microcomputer 13 controls the control voltage of the zoom motor driver 14 by the D / A converted output according to a control table prepared in advance. The zoom motor 15 is driven by the output of the zoom motor driver 14, and the moving speed of the variator lens is controlled so that the change amount of the focal length or the change amount of the image forming position is kept substantially constant. By this control, the moving speed of the variator lens becomes slower in the vicinity of the telephoto side than in the vicinity of the wide angle side.

As a result of controlling the moving speed of the variator lens as described above, as shown in FIG. 2 (a), the amount of change in the focal length with respect to the moving time of the variator lens can be kept constant. Alternatively, as shown in (b), the amount of change in the master lens position is kept constant. By the way, (a), (b) of Figure 3
Represents the focal length or the master lens position with respect to the moving time of the variator lens in the conventional device, and the change amount of the focal length is not constant and the change amount of the master lens position is not constant. ..

FIG. 4 shows another embodiment, and FIG.
The same symbols as are the same. In this Figure 4,
The zoom encoder voltage from the zoom encoder 12 is applied to a circuit composed of a diode and a dividing resistor, and the control voltage of the zoom motor driver 14 is controlled by the voltage converted by this circuit. As a result, similarly to the case of FIG. 1, the moving speed of the variator lens is controlled so that the change amount of the focal length or the change amount of the imaging position is kept constant.

[0015]

As described above, the present invention controls the moving speed of the variator lens based on the position information of the variator lens so that the moving speed is slower in the vicinity of the telephoto side than in the vicinity of the wide angle side. Therefore, even if quick zooming is performed, focus blurring does not occur near the telephoto side, motor noise that occurs near the telephoto side can be reduced, and an unnatural change in the angle of view can be prevented. No, a natural zooming motion is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing control characteristics of the device of the present invention.

FIG. 3 is a characteristic diagram showing control characteristics of a conventional device.

FIG. 4 is a block diagram showing another embodiment of the present invention.

FIG. 5 is a configuration diagram of a commonly used zoom lens for a video camera.

FIG. 6 is a graph showing the amount of movement of a master lens with respect to the amount of movement of a variator lens of a commonly used camera.

FIG. 7 is a graph showing a focal length with respect to a moving amount of a variator lens of a commonly used camera.

[Explanation of symbols]

 11 Lens 12 Zoom Encoder 13 Microcomputer 14 Zoom Motor Driver 15 Zoom Motor

Claims (1)

[Claims] 1. An image forming point of a camera lens having a focusing lens, a variator lens, an erector lens and a master lens, and having no compensator lens, which changes as the variator lens is moved to perform a zooming operation. In the case where the position is kept at a constant position by the movement of the master lens, a means for obtaining the position information of the variator lens and a movement speed of the variator lens is controlled by the position information obtained by the means, and this movement is performed. A zoom control device for a camera lens, wherein the speed is set to be slower near the telephoto side than near the wide angle side.