JP2893993B2 - Zoom drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom driving apparatus for a zoom lens used in a video movie.

[0002]

2. Description of the Related Art In recent years, with the spread of video movies, it has become common to employ an inner focus type zoom drive device capable of autofocusing from immediately before a lens to infinity.

[0003] A conventional zoom driving device will be described below. FIG. 3 is a block diagram showing a conventional zoom driving device. The first lens group 1, the second lens group 2, the third lens group 3, and the fourth lens group 4 are lens groups for photographing a subject on the image sensor 6, and the diaphragm 5 adjusts the amount of light that strikes the image sensor 6. . Reference numeral 8 denotes a zoom motor. The zoom motor driving device 10 drives the zoom motor according to the state of the zoom switch 11 to move the second lens group 2. The control circuit 12 calculates the position to which the fourth group lens moves based on the value of the zoom encoder 7, and drives the fourth group lens 4 by the focus motor 9. The second group lens 2 is a variable power lens for changing the size of an image shown on the image sensor 6, and the fourth group lens 4 is a focus lens for focusing the subject on the image sensor 6.

[0004] The operation of the conventional zoom drive device configured as described above will be described below.

First, when the user wants to change the image outline of the subject, the zoom switch 11 is pressed.
The state of 1 is transmitted to the zoom motor drive circuit 10, whereby the second lens group 2 is driven. The position of the second group lens 2 is controlled by a zoom encoder 7 in a control circuit 1.
2, the control circuit 12 calculates the moving position of the fourth lens group for focusing the subject on the image sensor 6, and drives the focus motor.

A series of operations as described above is called zoom tracking. This zoom tracking will be described in more detail with reference to FIG. In FIG. 2A, the horizontal axis is 2
Group (zoom) lens position, vertical axis is 4 groups (focus)
In the case where zoom tracking is performed in the direction of wide from the tele end at a position of the lens, for example, a subject 3 m away, a miracle like a curve in the figure may be traced. Z0 is the position of the second group (zoom) lens at time t0, F0 is the position of the fourth group (focus lens) at that time, Z
1 is the position of the second group (zoom) lens at time t1, F1
Is the position of the fourth group (focus lens) at that time, Z2 is the position of the second group (zoom) lens at time t2, and F2 is the position of the fourth group (focus lens) at that time. FIG. 2 (b)
In the operation of FIG. 2A, the horizontal axis represents time, and the vertical axis represents 4
This is converted into a group (focus) lens position. An ideal zoom tracking operation is one in which the four lens units move smoothly over time as shown in FIG.

[0007]

However, the above-mentioned conventional configuration has the following problems. Since the position of the second group lens 2 output from the zoom encoder includes an error due to electric noise or the like, the position of the second group lens cannot be accurately detected, and the position of the second group lens is tele side or wide from the actual position. The side position is communicated to the control circuit. Therefore, the zoom tracking operation is performed as shown in FIG.
The focus lens does not move as shown in FIG. As a result, the in-focus state of the image of the image pickup device is improved or deteriorated, and when the image of the movie is viewed, the image becomes a jerk. Also, since the movement of the focus motor becomes intense,
A loud motor sound is also recorded as noise in the recorded sound of the movie.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a zoom driving device in which an image does not jerk during zoom tracking and motor noise is extremely small.

[0009]

In order to achieve this object, a zoom driving apparatus according to the present invention stores a value of a zoom encoder, that is, a position of a second lens group by a latch circuit, and according to a state of a zoom switch. The comparator is configured to determine whether to use the stored value or to use a new value, to transmit the determined value to the control circuit, and calculate the position for driving the fourth lens group.

[0010]

According to this structure, fluttering in one direction among fluttering components due to electric noise or the like of the zoom encoder is mitigated, so that image blurring during zoom tracking is suppressed, and motor noise of the focus motor is extremely small. Become.

[0011]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 13 denotes a latch circuit, and reference numeral 14 denotes a comparison circuit, and a description of the same components as those in the conventional configuration will be omitted. The latch circuit 13 stores the value of the previous zoom encoder, and the comparator 14 determines whether to use the value stored in the latch circuit 13 or to use a new value according to the state of the zoom switch 11. Control circuit 12
To tell.

The operation of the zoom drive device of the present embodiment configured as described above will be described with reference to FIG.

For example, suppose that the zoom switch 11 in the wide direction is pressed assuming that the second lens group 2 is at the tele end. In the conventional zoom driving device, the position of the second group lens output from the zoom encoder includes an error due to electrical noise or the like, and therefore, the control circuit cannot accurately detect the position of the second group lens, and Enter 2
The position of the group lens was rattled as shown in FIG. The position of the fourth group lens calculated from the position of the second group lens is as shown in FIG. 9D, and the fourth group lens is driven rattling. However, in the zoom drive device according to the present invention, first, the position of the second group lens 2 previously input is stored by the latch circuit 13, and then, when the switch in the wide direction is pressed, the latch circuit 13 is compared with the current value, and the value closer to wide is output.
When the switch in the “le” direction is pressed, the comparator 14 is configured to compare the value of the latch circuit 13 with the current value and output a value closer to “tele”. The transmitted position of the second lens group 2 is as shown in FIG. Using the position of the second group lens 2, the fourth group lens 4
When the position is calculated and driven, the result is as shown in FIG.
As is apparent from a comparison between (d) and (f), when the zoom driving device of the present invention is used, fluttering of the position of the second lens group 2 is suppressed, and the fourth lens group 4 moves smoothly. become.

[0015]

As described above, according to the present invention, in the inner focus type zoom driving device, the latch circuit and the comparator are provided to suppress the fluttering of the fourth group lens, thereby suppressing the blurring during zoom tracking. The motor noise of the focus motor becomes extremely small.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a zoom driving device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining a tracking operation.

FIG. 3 is a block diagram showing a configuration of a conventional zoom driving device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1 group lens 2 2 group lens 3 3 group lens 4 4 group lens 5 Aperture 6 Image sensor 7 Zoom encoder 8 Zoom motor 9 Focus motor 10 Zoom motor drive circuit 11 Zoom switch 12 Control circuit 13 Latch circuit 14 Comparator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 7/08 H04N 5/232

Claims (1)

(57) [Claims] 1. An inner focus type zoom lens, comprising: a first group lens, a second group lens, a third group lens, and a fourth group lens for photographing a subject on an image sensor;
An aperture for adjusting the amount of light applied to the image sensor, a zoom motor drive circuit and a zoom motor for moving the second group lens according to the state of a zoom switch, a zoom encoder for detecting the position of the second group lens, and storing the position of the second group lens A latch circuit, a comparator that determines whether to use the value of the latch circuit or the value of the zoom encoder according to the state of the zoom switch, a focus motor that drives a fourth lens group, A control circuit for calculating the position to which the fourth lens group moves based on the output.