JPH041618A - Video camera - Google Patents

Abstract

PURPOSE:To automate zooming operation by storing the position of a focusing position at the timing where a variable power lens is switched from a middle position to a wide-angle position previously and setting the power varying lens at the middle position at the timing where the focusing lens passes the stored position in the direction of focusing to a longer distance. CONSTITUTION:When the relative distance between the camera and a subject decreases below 3 m while the variable power lens 2 is set at the middle position, a field angle setting means 13 switches the variable power lens 2 to the wide-angle end. When the focusing lens 3 is moved by a focusing control means 12 to reach the wide-angle end, the position of the power varying lens 2 is stored in a focal length switching means 14. When the relative distance between the camera and subject increases and the focusing lens 3 moves to pass the stored position, the focal length switching means 14 switches the variable power lens 2 to the middle position. Consequently, zooming in the direction where the size of the subject on a picture plane is maintained is performed automatically according to the relative distance between the subject and camera.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video camera, and more particularly, it has an optical system for imaging that performs focusing operation and zooming operation of a non-front lens moving type using independent actuators. The present invention relates to a video camera configured to automatically perform a focusing operation depending on the distance between the camera and a subject.

[Conventional technology]

Conventionally, there are many types of video cameras configured as described above, and in this type of video camera, the imaging optical system is of a non-moving front lens type, that is, the lens located at the front end is fixed. Therefore, the focusing operation is performed by moving the focusing lens located behind the front end lens (on the focal point side), and the zooming action is also performed by moving the variable power lens located behind the front end lens. be done.

Furthermore, the automatic focusing operation according to the distance between the camera and the subject is usually called autofocusing, and in conventional video cameras, the size of the subject displayed in the viewfinder is The camera is configured so that the photographer performs zooming while checking the camera's accuracy (references not cited).

[Problem to be solved by the invention]

Now, thinking about the situation when shooting, when shooting a still subject such as a landscape, when deciding on the composition of the subject, there is no need to zoom much after zooming by - degrees. When photographing a person, it is necessary to zoom frequently as the person moves.

Also, the reason for zooming in this way is:
When photographing a person, the aim is to maintain the size of the subject on the screen to the extent that the person's facial expressions can be seen, and for this reason, conventional video cameras do not take photographs of people. In some cases, zooming becomes troublesome.

In addition, with a video camera that performs autofocusing, it is possible to determine the relative distance between the camera and the subject from the set position of the focusing lens and the focal length at that point. However, if you try to configure the system so that zooming is performed every time the relative distance changes depending on the set position of the focusing lens, it is possible to perform the zooming operation after the focusing lens completes its operation. Therefore, the zooming operation tends to be delayed with respect to the movement of the subject.

In addition, there are different types of optical systems that do not move the front lens, such as an inner focusing type or a rear focusing type, and in this type of optical system, when zooming,
In other words, when the focal length of the optical system is adjusted, even if the distance between the camera and the subject is constant, there will be a difference in the set position of the focusing lens (in an optical system that focuses by moving the front lens) Even if you zoom, if the distance between the camera and the subject remains constant, the set position of the front lens will not change.)

Moreover, in this type of optical system, when the optical system is set to the short focal length side (wide-angle side) by zooming, the amount of movement of the focusing lens when a subject close to the camera moves in the distance direction is extremely small. Also, when the optical system is set to the wide-angle side, the depth of field is deep, so it is difficult to obtain accurate subject position information, so as mentioned above, zooming operations are performed based on the set position of the focusing lens. If this is to be done automatically, a highly accurate sensor must be used to accurately determine the setting position of the focusing lens, and there is room for improvement.

In this non-front lens moving type optical system, a graph in which the amount of zooming operation is set on the horizontal axis and the amount of movement of the focusing lens is set on the vertical axis is shown in Figure 5. as,
Even when photographing a subject at infinity (■), this optical system can be moved from the tele end (T) (long focal length end) to the wide end (W).
When the zooming operation is performed to the end on the short focal length side, the focusing lens moves (in reality, it moves forward once and then returns to its original position). Even when photographing a subject located at a position from (In+) to (I n+), if this optical system is set to the wide end (-), the amount of movement of the focusing lens will be Z
) (actually, the amount is about 60 μm).

An object of the present invention is to provide a video camera equipped with a non-front lens moving type optical system that
Automatically performs zooming in a direction that maintains the size of the subject on the screen, and when performing this zooming, even if the optical system is set to the short focus side, it also responds to changes in the relative distance. The object of the present invention is to rationally configure a video camera that performs zooming operations more accurately with a structure as simple as possible.

[Means to solve the problem]

The present invention is characterized by an imaging optical system in which a first actuator performs a focusing operation without moving the front lens and a second actuator performs a zooming operation; The focal length of the optical system is maintained at a predetermined value when a subject exists within a predetermined photographing area formed based on the position of the camera. The second actuator is configured to maintain the focal length of the optical system at a value shorter than the predetermined value when a subject exists in a photographing area formed adjacent to the camera side of the predetermined photographing area. It is equipped with an angle of view setting means that performs zooming in stages in response to continuous changes in the relative distance of the subject, and a position for determining the position of the focusing lens operated by the first actuator. and detecting means, wherein the angle of view setting means sets the focal length of the optical system to the shortest distance set by the angle of view setting means because the relative distance is displaced in a shortening direction beyond the boundary of the photographing area. When the value is set to a value that When a focusing operation is performed in which the lens passes through this memorized position, at the timing of this passing, the focal length of this optical system is set to a value corresponding to the adjacent photographing area, regardless of the boundary of the photographing area. The present invention is characterized by comprising a focal length switching means for increasing the focal length to
Its action and effects are as follows.

[For production]

When the above characteristics are configured as shown in FIGS. 1 to 4, for example, when the variable magnification lens (2) is set at the middle (1'l) position, the relative path between the camera and the subject is # (
D) reaches 3 m or less, the angle of view setting means (13) switches the variable magnification lens (2) to the wide end (-), and at the same time, the focusing control means (12) switches the focusing lens (3) to the wide end (-).
Move the image of the subject to the position where it will be in focus.

Further, when the variable power lens (2) starts to move, the focusing position of the focusing lens (3) also changes accordingly, so the focusing lens (3) also moves accordingly.

Then, the focal length switching means (14) stores the position of the variable power lens (2) at the timing when the focusing lens (3) reaches the wide end.

And like this, the focusing lens (3) is at the wide end (Homare)
, the relative path M between the camera and the subject is
(D) is thick (becomes), the focusing lens (3) is moved by the focusing control means (12), and the distance f is stored as described above.
fZ (X), the focal length switching means (
14) switches the variable magnification lens (2) to a position corresponding to the middle (M) focal length at the timing of this passage.

Further, in the present invention, it is possible to simultaneously operate the variable power lens (2) and the focusing lens (3) based on the detection result from the focus control means (12), and the variable power lens (2)
This variable magnification lens (2)
The mechanism for feeding back the position can be a contact type encoder or other low-precision mechanism, and furthermore, for example, it can measure the position of the focusing lens (3) at the wide end (W) with high precision, and Compared to the method that calculates the distance of
It is also possible to reduce the accuracy of the actuator or malfunctions caused by mechanical errors in the actuating section.

[Example〕 Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 shows an outline of a video camera. In this camera, the optical system for imaging is a fixed-position main lens (
front lens) (1) and a variable magnification lens for zooming (
2) and a focusing lens (3) for focusing
are arranged in series along the optical axis (L), and a half prism (4) and a photographing element (not shown) are arranged on the focal point side of this optical system. The focused light beam is sent to a focusing module (5).

In addition, in the focusing module (5), the light flux is photoelectrically converted and then sent to the focus determination circuit (6), which determines whether the subject image is in focus or out of focus. However, in the case of an out-of-focus state, the "deviation amount" is controlled by the control device (
7).

This control device (7) is a microprocessor (not shown)
The control device (7) also includes a focusing motor (8) as a first actuator that performs a focusing operation of the focusing lens (3), and a zoom lens (2). Variable magnification motor (9) as a second actuator that operates
A first sensor (10) as a detection means for detecting the position of the focusing lens (3) and the position of the variable magnification lens (2) is formed. An input signal path is formed for obtaining detection signals from each of the second sensors (11).

In this video camera, when shooting, the control device (7) calculates the driving amount of the focusing lens (3) based on the "shift amount" output from the focus determination circuit (6),
The camera is configured to automatically perform focusing, that is, autofocusing, by driving a focusing motor (8).

Additionally, this video camera has a mechanism for manually operating the variable magnification lens (2), that is, zooming (not detailed), and a mechanism for automatically zooming according to the distance to the subject. It is equipped with a camera that allows you to select manual or automatic mode when shooting.

A mechanism that automatically performs zooming performs zooming according to the relative distance between the camera and the subject when shooting,
It functions so that the size of the subject on the screen does not change much.

In other words, with this video camera, when zooming is performed automatically (hereinafter referred to as program mode), the focal length is set at the tele end (T) on the long focal length side and at the short focal length side, as shown in Figure 3. A contact type encoder is used for the second sensor (11) so that the second sensor (11) is set at only three positions: the wide end (W) of When zooming, use the focusing lens (3
), find the value before the relative distance changes, and calculate the value of the in-focus position obtained from the focus determination circuit (6).
The value after the relative distance has changed by calculating the value of "Amount of deviation" and the above value, that is, if the subject has moved, the relative distance between the camera and the subject after the movement is calculated and this value is "10 m. ~ω'', the variable magnification lens (2) is set to the telephoto end (T), and when located in the photographic area of ``3m to 10m'', the variable magnification lens (2) is set to the middle position ( M), when located in the shooting area of ``rim ~ 3 m'', the relative distance between the camera and the subject changed continuously by setting the variable magnification lens (2) to the wide end (-). The basic operation is set to adjust the focal length in stages even when the lens is closed.

Note that a linear potentiometer is used as the first sensor (10) to steplessly detect the position of the focusing lens (3).

In addition, in this program mode, when switching from the wide end (W) to the middle position (M) in the zoom operation described above, the variable magnification lens (2 ) is switched, and the timing when the focusing lens (3) passes through the memorized position by autofocusing in the direction of focusing on a distant object. The operation is set so that the variable magnification lens (2) is set to the middle position t (M).

The configuration described above can be expressed as shown in FIG. 2, and in this configuration, the focus control means (12) is a system for performing autofocusing, and the field angle setting means 13) is a system that automatically performs zooming, and the focal length switching means (14) is a variable magnification lens (2
) from the wide end (-) to the middle position (M), each means is configured by a program set in the control device (7), and the position detection means is the first sensor (10) itself. It is.

In addition, in this video camera, the operation by the focus control means (12), that is, autofocusing, is always operated during shooting (the operation is not described in detail), and the operation by the angle of view setting means (13) and the focal length operation with the switching means (I4);
In other words, the outline of the operation in the program mode is shown in the flowchart of FIG.

That is, when program mode control is started, initial settings are first made (11 steps), and then the variable magnification lens (2
) is set to the middle position (M).
12.113 step), if the camera is not set to the middle position (M), or even if it is set to the middle position (M), the relative distance (D) between the camera and the subject is not less than 3 m. ($14. #5 step) As mentioned above, the variable magnification lens (2
) until the program mode is reset (#6.117 step).

Next, when it is determined that the relative path i1 (D) has reached 3 m or less in 15 steps, the variable magnification lens (2)
is set to the wide end (-), and the position iff (X) of the focusing lens (3) at this setting timing is stored in a memory (not shown) ($18,119 steps).

After this, the position (Y) of the focusing lens (3), which changes with autofocusing, is sampled at extremely short intervals and compared with the stored value (X) as described above. Set the variable magnification lens (2) to the middle position (M) at the timing when the value reaches a value larger than the value (X).110
, 111, 112 steps), and the process proceeds to step #6 described above.

In addition, #10. The program mode is also configured so that it can be exited from this program mode by a reset operation within the routine of step #11 (step 113).

Incidentally, in the imaging optical system of this video camera, the variable magnification lens (2) is
The operating stroke has a value of about 10 times, and as mentioned above, when memorizing the position of the focusing lens (3) at the timing of switching the variable magnification lens (2) to wide 1 (W), , Focusing lens (3) by autofocusing
Normally, the camera has already reached the in-focus position, so if the subject moves within a very short period of time, the relative distance between the camera and the subject may be 3 m, as shown by the imaginary line in Figure 3.
From the wide end (匈) to the middle position (
M) may also be switched to.

[Bessio side]

In addition to the above-mentioned embodiments, the present invention may also include, for example, the focal length set in the program mode may be set in three steps or more, and
The focusing control means, the angle of view setting means, and the focal length switching means can be configured by hardware by combining logic gates, comparators, etc. Also, the imaging optical system can be configured as a rear focusing type. good.

〔Effect of the invention〕

Therefore, even if the relative distance between the subject and the camera changes, zooming in a direction that maintains the size of the subject on the screen without causing trouble to the photographer is possible with a simple structure and relatively quickly. In addition, even if the movement stroke of the focusing lens is small in a short focus range, such as in a non-front lens moving type optical system, the zooming can be performed accurately without using high-precision parts. The camera was constructed rationally.

[Brief explanation of drawings]

The drawings show an embodiment of a video camera according to the present invention, and the first embodiment shows a video camera according to the present invention.
The figure is a block diagram of the imaging optical system and control system, Figure 2 is a block circuit diagram showing the configuration of the control system, Figure 3 is a graph showing the relationship between relative distance and focal length, and Figure 4 is a diagram of the control system. FIG. 5 is a flowchart showing the operation, and is a graph showing the amount of movement of the focusing lens relative to the amount of zooming operation in the non-front lens moving type optical system. (8)...First actuator, (9)...
. . . second actuator, (10) . . . position detection means, (12) . . . focus control means, (13)
)... Angle of view setting means, (14)... Focal length switching means.

Claims (1)

[Claims] an imaging optical system that performs a non-front lens moving type focusing operation with a first actuator and a zooming operation with a second actuator; and a focusing control that operates the first actuator based on the relative distance between the camera and the subject. When a subject exists within a predetermined photographing area formed based on the position of the camera, the focal length of the optical system is maintained at a predetermined value, and the camera is When a subject is present in the photographing area formed adjacent to the side, the second actuator is controlled to maintain the focal length of the optical system at a value shorter than the predetermined value. , comprising angle-of-view setting means for performing zooming in stages in response to continuous changes in relative distance of the subject, and position detection means for determining the position of the focusing lens operated by the first actuator,
The angle of view setting means sets the focal length of the optical system to the shortest value set by the angle of view setting means because the relative distance is displaced in a shortening direction beyond the boundary of the photographing area. In this case, the position of the focusing lens at the timing of this setting is stored based on the detection result of the position detecting means, and after this storage, the position of the focusing lens is stored due to the expansion of the relative distance. When a focusing operation is performed to pass through a position, the focal length increases the focal length of this optical system to a value corresponding to that of the adjacent photographing area at the timing of this passage, regardless of the boundary of the photographing area. A video camera comprising switching means.