JPH03284738A - Camera provided with soft focus switching function - Google Patents

Abstract

PURPOSE:To accomplish a soft focus function which is excellent in all the focal distance and all the object distance by moving the rear lens group of a photographing lens group in an optical axis direction by the use of a stepping motor and setting it at a position deviated from a regular position by a control circuit. CONSTITUTION:In a camera apparatus reset at the position of an origin, a lens is manually focused on an object and the rear group lens 11b is moved to a position that an image is formed on a CCD 12, for example, by turning a volume control so that the stepping motor 18 is driven. This operation is performed by actuating a focus detection circuit 32 and a diaphragm driving circuit 33 by a video signal processing circuit 31. When a soft focus switch 23 is made in an on-state, a soft focus signal generation circuit 24 is actuated and gives a command informing that a soft focus state is obtained to the control circuit 21. The circuit 21 is set at the position deviated from the regular position in order to perform a soft focus action, and the soft focus function which is excellent in the object distance is accomplished at the position of a variable power group lens 11d in a front group lens 11a by a focal distance information detection circuit 25.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a camera with a soft focus switching function, in which a soft focus function is added to a video camera lens mounted on a movie camera or the like.

Conventional technology In recent years, with the spread of movies (VTR integrated cameras),
Video camera lenses are also becoming more sophisticated and value-added, with higher magnifications, wider angles, and higher sensitivity (bright lenses with smaller FNos). However, the soft focus function used for portrait photography and the like has hardly been introduced into movie cameras due to the complexity of the lens mechanism.

Hereinafter, an example of the above-mentioned conventional soft focus mechanism will be described with reference to the drawings.

Figure 5 shows the configuration of a conventional soft focus camera?
・[This is a perspective view. In FIG. 5, in the normal specification state, the CCD 2 is installed with an appropriate space so that the imaging surface of the CCD 2 matches the imaging position of the photographing lens I. next,
In the soft focus state, the soft focus lens 3 is coaxially inserted into the space on the optical axis of the photographing lens 1 and the CCD 2, and the photographing lens 1 is adjusted by the change in so-called back focus due to the insertion of the soft focus lens 3.
Alternatively, by moving the CCD 2 on the optical axis using the soft focus drive mechanism 4, the spherical aberration generated by the photographing lens 1 and the soft focus lens 3 can be realized to an appropriate value as shown in FIG. It was something that could be done. In FIG. 6, (a) shows normal spherical aberration, and (b) shows spherical aberration during soft focus.

Problems to be Solved by the Invention However, in the above configuration, it is necessary to separately provide a soft focus lens, and there are problems in terms of cost, weight, etc., including the drive mechanism thereof.

In addition, when the above-mentioned photographic lens is a zoom lens, in order to install a soft focus lens so that the same spherical aberration can be generated at all focal lengths, the air distance between the front photographic lens and the CCD must be further changed. There was also the problem that the mechanism became even more complicated.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a camera with a soft focus switching function at low cost using simple software without adding a soft focus lens.

Means for Solving the Problems In order to solve the above problems, the camera with a soft focus switching function of the present invention includes a moving means for moving a part of the photographing lens group in the optical axis direction, and a moving means for moving a part of the photographing lens group in the optical axis direction. The lens is equipped with a control means for setting a part of the lens at a position shifted from a lens set position determined based on a video signal in accordance with the subject distance.

Operation With the above-mentioned configuration, during soft focus, the control means works to set a part of the photographic lens group to a position shifted from the normal position using the moving means, thereby setting another lens group for soft focus. This eliminates the need for a camera with a soft focus switching function, making it possible to provide a camera with a simple configuration and low cost.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a configuration diagram showing a camera with a soft focus switching function according to an embodiment of the present invention. In FIG. 1, the photographic lens 11 includes a front group lens lla, a rear group lens llb, and an automatic diaphragm 5 disposed between them, and the front group lens Ifa includes a fixed group lens lJc and a variable magnification lens for zooming. It is composed of a group lens Ild and a zoom encoder 16 for the variable power group lens Ild.

In addition, the rear lens group llb has a CCD depending on the distance of the object.
In order to image the light rays from the object on the image forming plane 12, the rear group lens frame 17 with the rear group lens lld fixed is moved in the optical axis direction by the stepping motor 18. The operation of the attached camera will be explained below with reference to FIGS. 1 and 2.

Here, FIG. 2 shows a flowchart showing the processing executed by the circuit blocks of FIG. 1.

When taking pictures with a camera, when the power of the camera is first turned on, the stepping motor 18 is activated by the stepping motor drive circuit 22 in response to a command from the control circuit 21.
rotates, and simultaneously moves the rear group lens frame 17 connected to the stepping motor 18 and the rear group lens Ilb, which is integrated with the rear group lens frame 17, in the optical axis direction. (not shown) (step A).

Next, by manually focusing the lens on the subject (step B), for example by driving the stepping motor 18 by turning a volume control (not shown), the rear group lens llb adjusts to the subject distance. Then CCD12
(step C). These operations are performed by the video signal processing circuit 31 operating the focus detection circuit 32 and the aperture drive circuit 33.

Next, when the soft focus switch 23 is turned on (step D), the soft focus signal generation circuit 24
In step E), a command is given to the control circuit 21 to notify that the soft focus state has been reached.

Here, the control circuit 21 is composed of, for example, a variable resistance element, which generates a voltage corresponding to the position of the variable magnification group lens lld in the front lens group lla from the focal length information detection circuit 25 in order to perform a soft focus operation. The focal length f is detected from the voltage of the zoom encoder I6 (Step F), and the FNo. detection circuit 26 detects the focal length f of the photographing lens 1.
FNo. and F are detected from the voltage of the iris encoder 19, which is constituted by, for example, a Hall element, and generates a voltage corresponding to the aperture diameter of the aperture blades of the automatic aperture 15 (step G).

Next, the control circuit 21 controls the data ROM table 2
7, the focal length f and FNo.

From the ROM data corresponding to F, a stepping motor 1 is used to provide the amount of defocus necessary to move the rear lens group itb to achieve a soft focus state.
8, that is, the defocus pulse PSF (
(signs are both + and -) (step H), and this P
By applying sp to the stepping motor 18 via the stepping motor drive circuit 22 (Step I)
, a predetermined spherical aberration can be obtained, and a soft focus state can be obtained.

The above is the basic operation. Next, the operation of the soft focus function during zooming will be explained using FIGS. 3 and 4.

First, the zooming operation in the normal state (non-soft focus state) of the lens of this example is shown in Figure 3 (
This will be explained using a). In FIG. 3(a), the horizontal axis indicates the position of the variable power group lens, and the vertical axis indicates the position of the rear group lens. The solid line in the figure uses the object distance in the normal state as a parameter and indicates the in-focus position of the rear group lens corresponding to the position of the variable power group lens with respect to the object distance. Then, data obtained by sampling this curve is stored in the normal mode P of the data ROM table 27 in FIG. It is written as 1m. Furthermore, the subject distance that is not written as data, for example 3m is 2m.
The broken line in Figure 3 (a) is the same data as above when the aperture is wide open (minimum FNo.). , the difference between the solid line and the broken line is written in the soft focus mode FNo, MiN of the data ROM table 27 as a defocus amount Psp.

Furthermore, when the aperture is stopped down, the spherical aberration decreases as shown in FIG. 3(b), so it is necessary to further defocus the rear group lens 11b to increase the spherical aberration.

Therefore, in this embodiment, numerical data obtained from a curve similar to that shown in FIG. It is stored. The above is collectively referred to as a soft focus mode in the data ROM table.

FIG. 4 is a flowchart showing the processing executed during zooming. In FIG. 4, when the focal length f and FNo.F are determined by the method described above (step G), the control circuit 21 refers to the normal mode in the data ROM table to determine the rear group movement pulse P during zooming. ,1
(Step J).

Next, in step M, if there is no soft focus signal, proceed to step L; if there is a soft focus signal, further refer to the soft focus mode in the data ROM table to find the defocus pulse PAF for the rear group (step M ).

After the above steps, P. By applying pulses of rar+P Sr to the stepping motor 18 (step N), a zooming operation having a good soft focus function with sufficient spherical aberration in the entire zoom range is performed.

As described above, according to this embodiment, a stepping motor is used to move the rear group lens of the photographing lens group in the optical axis direction, and the rear 11'F lens is moved during soft focus.
At that time, by setting the focal length information to a position shifted from the normal position using the focal length information detection circuit, there is no need for a special lens group, and even when zooming, the entire focal length can be read out from the data ROM table prepared in advance. , it is possible to achieve good soft focus function at all subject distances.

Effects of the Invention As described above, according to the present invention, there is no need for a special lens group when switching to soft focus, and even when zooming, it is possible to read out the data ROM prepared in advance so that the image can be photographed at all focal lengths and at all subject distances. The excellent effect of realizing a good soft focus function can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a camera with a soft focus switching function according to an embodiment of the present invention, FIG. 2 is a flowchart showing basic processing executed by the camera, and FIG.
b) is a characteristic diagram for explaining the operation of the same camera, FIG. 4 is a flowchart showing the processing executed during zooming by the same camera, FIG. 5 is a perspective view showing a conventional lens configuration, and FIG. 6 is a It is a characteristic diagram of spherical aberration in a conventional example. 11...Photographing lens, lla...Front group lens, ll
b...Rear group lens, lie...Fixed group lens, ll
d...Variable power group lens 12...CCD. 15... Automatic aperture, 16... Zoom encoder, 17... Rear group lens frame, 18... Stepping motor, 19... Iris encoder, 2I... Control circuit, 22... Stepping motor drive circuit, 23... Soft focus switch, 24... Soft focus signal generation circuit, 25... Focal length information detection circuit, 26... FNo., detection circuit, 27... Data ROM table.

Claims (1)

[Claims] 1. A moving means for moving a part of the photographic lens group in the optical axis direction; and a control means for setting a part of the photographic lens group at a position deviated from its normal position using the moving means during soft focus. A camera with soft focus switching function.