JPH07107372A - Video camera with shake prevention device - Google Patents

Abstract

PURPOSE:To provide a video camera capable of reducing out of focus, inadequate exposing time when object distance or object luminance change by quickening the responding speed of a focus lens or a diaphragm even at the time of providing a shake prevention device. CONSTITUTION:When the shake prevention device is in an operating state, (Th0) ON and (Th1) ON of a curve c1 are set to be respective threshold values Th0 and Th1 and when the shake preventing device is in a non-operating state, (Th0) OFF and (Th1) OFF of a curve c2 are set to be respective threshold values Th0 and Th1. Then, focusing voltage A and threshold values Th0 and Th1 are compared to set a value quickening the moving speed of a lens group by an AF actuater when focusing voltage A<Th0, to set a value slower than the moving speed when Th0 <= focusing volatage A < Th1 and to set a value for stopping when Th1 <= focusing voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera equipped with a shake prevention device for suppressing shake of an image pickup screen caused by a shake of a photographer's hand.

[0002]

2. Description of the Related Art In recent years, photographing apparatuses such as still cameras and video cameras have been automated, and various functions such as automatic exposure adjusting means and automatic focus adjusting means have been put to practical use.

Particularly, in a photographing device such as a video camera, it is general to use a zoom lens as a photographing lens used, and the zoom ratio thereof tends to increase year by year.

On the other hand, the miniaturization of the photographing device is also remarkable, and due to the reduction of the photographing screen size, the development of high-density mounting technology, the development of a compact recorder mechanical chassis, etc., a small model capable of photographing with one hand appears. Is coming.

However, when a small video camera equipped with such a zoom lens is used, harmful shake of the screen is likely to occur due to camera shake of the photographer. Therefore,
In order to remove this shake and obtain a stable screen, various shake preventing devices have been proposed. If this kind of shake prevention device is used, not only the harmful shake of the screen due to such a shake, but also in the situation where the harmful shake cannot be eliminated even when using a tripod when photographing from a ship or car. However, it goes without saying that it has a great effect.

This type of shake prevention apparatus includes shake detecting means for detecting shake of an image pickup screen which occurs according to shake during photographing, and shake so that the screen does not shake according to the detected shake information. A shake correction unit that performs some shake suppression correction is included at least.

As the shake detecting means, for example, an angular accelerometer, an angular velocity meter, an angular displacement meter, etc. are known. As the shake correction means, a variable apex angle prism (details will be described later) used by the present applicant, or a video camera configured to cut out an area to be actually used as a screen from the obtained imaging screen information There is known a method of sequentially changing (tracking) the cutout position to a position where the shake is corrected.

As the shake correction means, here, the former method such as a variable apex angle prism or some other optical means is used to optically remove the shake at the stage of the image formed on the image pickup device. The correction method will be referred to as "correction means", and the latter method of electronically processing the image information including the shake to remove the shake will be referred to as "electronic correction means".

Generally, the optical correction means is capable of correcting a shake within an angle defined as a shake angle of the camera regardless of the focal length of the lens, and therefore, the tele side of the zoom lens. Even if the focal length is long, it is possible to have the shake removal performance with no practical problem. However, it has a drawback of increasing the size of the camera.

On the other hand, in the case of the electronic correction means,
In general, it is often advantageous for downsizing, but the correction factor on the screen, for example, for the vertical dimension of the screen is constant. Therefore, as the telephoto side focal length becomes longer, the shake removal It has the drawback of degrading performance.

FIG. 5 is a diagram for explaining the relationship between the focal length and the shake angle of the camera by the subject position on the screen.

In FIG. 5A, the optical axis of the lens is 13 when the camera is at the position indicated by 12, which means that the face of the person 11 who is the subject is almost centered. From this state, it is assumed that the camera rotates a degrees due to camera shake. At this time, the camera position is 14 and the optical axis is 15
, Respectively.

FIGS. 5 (B) and 5 (C) show the screen positions at the camera positions of 12 and 14, (B) showing the state at the tele end of the zoom lens, and (C) showing the wide end. Indicates the state of. Reference numeral 16 denotes a subject within the screen, and 17 and 1
9 shows a screen when the camera position is 12, and 18 and 20 show screens when the camera position is 14.

As is apparent from FIG. 5, even if the camera shake is the same a degree, naturally, the longer the focal length of the lens, the greater the harm as the shake on the screen. Therefore, an optical means such as a variable apex angle prism is effective especially as a shake correction means combined with a lens having a long focal length at the telephoto end.

FIG. 6 shows the structure of the variable apex angle prism.

In FIG. 6A, 21 and 23 are glass plates, and 27 is a bellows portion made of a material such as polyethylene. A transparent liquid 22 made of, for example, silicon oil is enclosed in the inside surrounded by the glass plates 21 and 23 and the bellows 27.

In FIG. 6B, two glass plates 21 and 2 are provided.
3 is in a parallel state, and in this case, the incident angle and the outgoing angle of the light ray 25 of the variable apex angle prism are equal. on the other hand,
When the angles are (A) and (C), the rays are bent at a certain angle as shown by rays 24 and 26, respectively.

Therefore, when the camera is tilted due to camera shake or the like, the shake is eliminated by controlling the angle of the variable apex angle prism provided in front of the lens so that the spectral line corresponding to the angle is bent. It can be done.

FIG. 7 shows this state. Assuming that the variable apex angle prism is in the parallel state in FIG. 7A and the light beam is capturing the head of the subject, the deflection is a degree as in FIG. 7B. On the other hand, by driving the variable apex angle prism to bend the light beam as shown in the figure, the photographing optical axis is still unchanged and the head of the subject is continuously captured.

FIG. 8 is a diagram showing an actual configuration example of a variable vertical angle prism unit including the variable vertical angle prism, an actuator section for driving the variable vertical angle prism, and a vertical angle sensor for detecting an angular state.

Since the actual shake is realized in all directions, the front glass surface and the rear glass surface of the variable apex angle prism are configured so as to be rotatable about the rotation axes in directions shifted by 90 degrees. Here, the subscripts a and b are used to indicate the respective components in the two rotation directions, but those having the same number have exactly the same function.
Also, some of the parts on the b side are not shown.

Reference numeral 41 denotes a variable apex angle prism, which is a glass plate 2
1, 23, the bellows portion 27, the liquid 22 and the like. The glass plates 21 and 23 are integrally attached to the holding frame 28 using an adhesive or the like. The holding frame 28 constitutes a rotary shaft 33 with a fixed component (not shown) and is rotatable around this shaft. The shaft 33a and the shaft 33b are different in 90 ° direction. A coil 35 is integrally provided on the holding frame 28, while the magnet 3 is attached to a fixed portion (not shown).
6, yokes 37, 38 are provided. Therefore,
By passing a current through the coil 35, the variable apex angle prism 41 rotates about its axis 33. There is a slit 29 at the tip of the arm portion 30 integrally extending from the holding frame 28,
The light emitting element 31 such as iRED provided on the fixed portion and the PS
An apex angle sensor is configured with a light receiving element such as D.

FIG. 9 is a block diagram showing a combination of a lens and a shake prevention device 55 having the variable apex angle prism 41 as shake correction means.

In the figure, 41 is a variable apex angle prism,
43 and 44 are apex angle sensors, 53 and 54 are apex angle sensors 4
An amplifier circuit for amplifying the outputs of 3, 44, 45 is a microcomputer, 46 and 47 are shake detecting means including an angular accelerometer, 48 and 49 are actuators including the coil 35 to the yoke 38, and 52 is a lens. is there.

In the microcomputer 45, the angular state detected by the apex angle sensors 43 and 44 and the shake detecting means 4
In order to control the variable apex angle prism 41 to an optimum angle state for removing shake according to the detection results of 6, 47,
The current to be applied to the actuators 48 and 49 is determined.

The main element is composed of two blocks because it is assumed that control in two directions 90 degrees apart is performed independently.

The shake prevention device 55 using a variable apex angle prism as the shake correction means has been described above.

Next, a general automatic focus adjustment method will be described with reference to FIG.

In FIG. 10A, reference numeral 61 shows the entire screen of the video camera, and 62 shows the distance measuring area therein.
This focus adjustment method is a method of detecting the contrast of an image in principle, and detects the blur amount by processing the output of the image having the contrast indicated by 63, for example. 10B shows a video signal of the image 63, and FIG. 10B shows a differential waveform thereof. (C) shows a waveform obtained by converting the differentiated waveform into an absolute value, and (d) shows a signal level A (evaluation value) obtained by integrating and holding the absolute value-converted waveform. That is, when the image 63 is sharp, a high signal level A is obtained, and when it is not sharp, that is, when the image is blurred, the evaluation value becomes a low value. Therefore, basically, as shown in FIG. 10C, the position B of the focus lens group that should be in focus can be determined by detecting the position with the highest signal level A.

In this method, the evaluation value A and the two threshold levels Th ₀ and Th ₁ are compared to divide the degree of blur into three.

As described above, in the conventional video camera, the functions such as the automatic focus adjusting means and the automatic exposure adjusting means have been generalized, and more recently, the shake preventing device has been put into practical use.

The automatic focus adjusting means and the automatic exposure adjusting means are generally tuned on the assumption that the video camera is held by hand, and are tuned as those having no shake prevention device. Was common. That is, especially when shooting with a long focal length on hand, the following effects due to automatic focus adjustment and automatic exposure adjustment appear due to camera shake even when a still subject is shot still. A system that takes these effects into consideration has been constructed so that the function does not become a problem in practical use.

The effects of the automatic focus adjustment are as follows: (1) The subject in the distance measuring area changes due to camera shake, and even if the same blur condition occurs, the focus voltage (level A in FIG. 10B signal (d)) changes field by field. (2) It is possible that the focus voltage drops due to camera shake within the shutter speed.

Further, it is conceivable that the effect of automatic exposure adjustment is that the subject in the photometric area changes due to camera shake, and the Y signal level changes for each field.

Since these effects are considered to be almost the same phenomenon as "noise is added" or "low-pass filter" is applied to the video signal, when tuning these functions in the conventional video camera,
Control algorithm measures such as so-called averaging (signal averaging) and setting of response delay time of actuators (focus lens moving actuator, aperture value varying actuator, etc.) have been performed.

[0036]

However, the above-mentioned conventional video camera having the automation function is required to be handled by a control algorithm such as averaging or setting of the response delay time of the actuator on the assumption that the video camera is handheld. Since the delay time of the response time such as the time to move the focus lens group to the in-focus position and the time to adjust the exposure to an appropriate state becomes noticeable, the actual subject distance or subject brightness may change. There was a problem that the photographed image was unsightly due to out-of-focus and inappropriate exposure time.

The present invention has been made in view of the above problems. Even if a shake prevention device is provided, the response speed of the focus lens and the diaphragm is increased, and when the subject distance or the subject brightness changes, out of focus or improperly. An object of the present invention is to provide a video camera capable of reducing the exposure time.

[0038]

In order to achieve the above object, the first invention of the present invention is to provide a shake prevention means for preventing shake of an image pickup screen which occurs according to a shake at the time of photographing, and a high frequency component of a video signal. In a video camera equipped with an automatic focus adjusting means for adjusting a focus position by driving a lens group for focus adjustment so as to maximize the value, the shake prevention means is in an operating state or a non-operating state. Detecting means for detecting whether or not the lens group of the automatic focus adjusting means is changed, and a changing means for changing the responsive state of the lens group by the changing means according to the state detected by the detecting means. It is characterized by having control means for changing.

A second aspect of the present invention is a shake detecting means for detecting shake of an image pickup screen generated according to shake during photographing, and a predetermined shake suppressing correction according to a detection result of the shake detecting means. In a video camera provided with a shake prevention means having shake correction means, and an automatic focus adjustment means for adjusting a focus position by driving a lens group for focus adjustment so that a high frequency component of a video signal is maximized. A change means for changing the response state of the lens group of the automatic focus adjustment means, and a control means for changing the response state of the lens group by the change means according to the detection result of the shake detection means. And

[0040]

According to the structure of the first aspect, when the detecting means detects the operating state of the shake preventing means, the changing means changes the responsive state of the lens group of the automatic focus adjusting means in accordance with the detected operating state. It

According to the structure of the second invention, the changing state of the lens group of the automatic focus adjusting means is changed by the changing means according to the detection result of the shake detecting means.

[0042]

Embodiments of the present invention will now be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing the schematic arrangement of a first embodiment of a video camera according to the present invention. In the figure, blocks having the same functions as those in FIG. 9 are assigned the same numbers, and explanations thereof are omitted.

This embodiment is different from the conventional example of FIG. 9 in CC
D1, a signal processing circuit 2, a frame designating circuit 3, a low-pass filter 4, an AF microcomputer 5, a movable lens 6, and an AF actuator 7 are added.

The CCD 1 is an image pickup device, and the output of the CCD 1 is supplied to a signal processing circuit 2 for converting the output signal into a video signal. The Y signal obtained by the circuit 2 is supplied to the frame designating circuit 3 which extracts only the signal within a predetermined distance measurement area from the Y signal, and the output of the circuit 3 outputs only the high frequency component of the Y signal. Low-pass filter 4 for extraction
Is supplied to. This warpass filter 4 is actually
In some cases, a plurality of low-pass filters are arranged in parallel.

The focus voltage thus taken out, that is, the output of the low-pass filter 4 is supplied to the AF microcomputer 5. Based on this focus voltage, the AF microcomputer 5 judges whether the focus is on or out of focus, In the case of out-of-focus, it is determined whether it is mae-pin or atop-pin, and the level of blurring. Further, the AF microcomputer 5 is provided with a focal length detecting means (not shown), an aperture value detecting means, a focal length f,
The aperture value F is supplied, and the AF microcomputer 5 determines the moving speed of the lens group 6 that moves for focusing according to these signals, and drives the AF actuator 7.

Here, a predetermined communication is performed between the microcomputer 45 for preventing shake and the AF microcomputer 5. In the present embodiment, this communication is for transmitting from the microcomputer 45 for preventing shake to the AF microcomputer 5 whether the shake preventive device 55 is in an operating state or in a non-operating state.

FIG. 2 is a flow chart showing a procedure of control processing executed by the AF microcomputer 5.

First, in step S1, it is determined whether the shake prevention device 55 is in an operating state or a non-operating state. When in the operating state, the threshold value T for changing the actuator speed set for the focus voltage in steps S2 and S3
The values of h ₀ and Th ₁ are (Th ₀ ) ON and (T
h ₁ ) Set ON. In the non-operating state, step S4
In S5, thresholds Th ₀ , T are set in the same manner as in steps S2 and S3.
(Th ₀ ) OFF and (Th ₁ ) OFF are set in h ₁ , respectively. Here, a setting example of (Th ₀ ) ON and (Th ₀ ) OFF or (Th ₁ ) ON and (Th ₁ ) OFF will be described with reference to FIG.

FIG. 3 is a graph showing the focusing lens position on the horizontal axis and the focus voltage on the vertical axis when the cameras are directed to the same subject at the same focal length and the same brightness. Here, the curve c1 shows the signal when the shake preventing apparatus is in the operating state, and the curve c2 shows the signal when it is in the non-operating state. The focus voltage obtained at the same degree of blurring is higher when the shake prevention device 55 is operating.
Therefore, (Th ₀ ) OFF <(Th ₀ ) ON, (Th
₁ ) The thresholds Th ₀ and Th ₁ are set so that OFF <(Th ₁ ) ON.

Returning to the flowchart of FIG. 2, step S
6 and S7, the focus voltage A and the threshold value Th ₀ ,
A comparison with Th ₁ is made. When the focus voltage A is lower than Th _{0 in} the comparison in step S6, a high speed value v ₂ is set as the actuator speed v in step S8 (v =
v ₂ ). When the focus voltage A is between Th ₀ and Th _1, a value v ₁ slower than v ₂ is set in step S9 (v = v ₁ ).
When the focus voltage A is equal to or higher than Th _1, it is determined that the focus is achieved, v = 0 is set in step S10, and AF is set.
Stop the actuator operation.

As described above, according to this embodiment, the threshold value for switching the actuator speed for focusing is changed depending on whether the shake prevention device 55 is in the operating state or the non-operating state. Therefore, the effect of increasing the response speed of the focus lens and the diaphragm can be obtained even if the shake prevention device is provided.

In this embodiment, the speed of the focusing actuator is switched depending on whether the shake prevention device is in the operating state or the non-operating state, but the same effect can be obtained by other configurations.

For example, the focus voltage is set to A = A-d, d = 0 when the shake prevention is not operated, a certain value is set when the shake prevention is not performed, and apparent curves c1 and c2 are made to coincide with each other, and thresholds Th ₀ and Th are set. _It is possible to set a predetermined value to ₁ and add the correction amount to Th ₀ and Th ₁ according to the operation state of the shake prevention device.

Further, in the actual automatic focus adjusting device, the thresholds Th ₀ and Th ₁ are also shifted by detecting the subject condition, for example, the high brightness state or the low contrast state, by some method. In such a case, the thresholds Th ₀ , T
It suffices to variably set h ₁ according to both the subject condition and the state of the shake prevention device.

Further, in this embodiment, two threshold values are provided, but more threshold values are provided, or the actuator speed and the focus voltage A are expressed by a certain function, and the actuator speed is changed according to this function. You may

[Second Embodiment] Next, a second embodiment of the present invention will be described.

As a method for finding the peaks (focus points) of the focus voltage curve as shown in FIG. 3, a method of giving an absolute threshold value as described in the above embodiment and a focus voltage A for each field are used. A well-known method is to obtain the difference between the two and determine the rotation direction and speed of the actuator based on the sign and the amount.

That is, for example, in FIG.
If the lens group 6 moves by x, and the focus voltage changes from A ₁ to A ₂ during this period, it is a method of determining whether or not the focus point is achieved by A ₂ −A ₁ = ΔA.

Here, Δx is the moving distance between one field, but if the time of this difference is changed according to the state of the shake prevention device, as a result, the amount of ΔA should be aligned at the same lens position. Will also be possible.

For example, when moving at the same actuator speed for both the curves c1 and c2 at the lens positions from P ₁ to P ₂ , there is a difference when the shake prevention device is in the non-operating state than when it is in the operating state. ΔA becomes smaller. When the absolute value of ΔA is proportional to the actuator speed, the motor speed used is higher in the operating state. Therefore, the speed can be increased, but conversely, for example, there is concern that the lens position hunts near the focus. In order to prevent this, more optimal control can be reproduced by changing the time difference of ΔA calculation depending on whether the shake prevention device operates or not.

[Third Embodiment] Next, a third embodiment of the present invention will be described.

In the above-mentioned two embodiments, the method of changing the constant in the algorithm of the automatic focusing apparatus depending on the operating state and the non-operating state of the image stabilizing apparatus is used.

On the other hand, in this embodiment, instead of the operating state and the non-operating state of the shake prevention device, a control method according to the detection result of the shake detecting means is used.

That is, even when the shake prevention device is in a non-operating state, for example, when it is attached to a tripod, the focus voltage becomes the curve c1 instead of the curve c2 in FIG. At this time, even if the operating state is switched depending on whether the device is operating or not, the optimum effect cannot be expected.

This problem is solved by using the flowchart of FIG. 5 instead of the flowchart of FIG.

In FIG. 4, first, in step S1, it is determined whether or not the output indicating the detection speed of the shake detecting means is larger than a predetermined value V ₀ , for example, if it is large, the process proceeds to step S11, and if it is small, the step is performed. Proceed to S14. The processes of steps S11 to S20 are the same as steps S2 to S10 of FIG.

In particular, when the shake detecting means is a non-electronic angular velocity sensor or the like which directly uses the CCD signal, the detection result of the shake detecting means is further corrected by the focal length, and then the threshold value or the like is set. Should be done.

[0069]

As described above, according to the present invention,
Shake prevention means to prevent shake of the image pickup screen that occurs according to shake during shooting, and to automatically adjust the focus position by driving the lens group for focus adjustment to maximize the high frequency component of the video signal In a video camera equipped with a focus adjusting means, a detecting means for detecting whether the shake preventing means is in an operating state or a non-operating state, and a response state of a lens group of the automatic focus adjusting means are changed. Change means,
A configuration having a control unit that changes the response state of the lens group by the changing unit according to the state detected by the detection unit, and a shake that detects shake of the imaging screen that occurs according to shake at the time of shooting. A shake prevention unit having a shake correction unit that performs a predetermined shake suppression correction according to a detection unit and a detection result of the shake detection unit, and a lens group for focus adjustment so that a high frequency component of a video signal is maximized. In a video camera equipped with an automatic focus adjusting means for adjusting the focus position, the changing means for changing the responsive state of the lens group of the automatic focus adjusting means, and the detection result of the shake detecting means, Since the changing unit changes the response state of the lens group, the control unit changes the response speed of the focus lens and the diaphragm even if the shake prevention device is provided. Reducing the defocusing or improper exposure time when the distance and object luminance is changed the effect that can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of a video camera according to the present invention.

FIG. 2 is a flowchart showing a procedure of control processing executed by the AF microcomputer of FIG.

FIG. 3 is a diagram showing characteristics of a focus voltage when the shake prevention device is operated and when it is not operated.

FIG. 4 is a flowchart showing a procedure of control processing executed by an AF microcomputer in the third embodiment.

FIG. 5 is a diagram illustrating a relationship between a focal length and a shake angle of a camera by using a subject position on a screen.

FIG. 6 is a diagram illustrating states of incident angles and emission angles of light rays when a variable apex angle prism is controlled.

7 is a diagram illustrating the principle of preventing shake using the variable apex angle prism of FIG.

FIG. 8 is a diagram showing a configuration example in which a variable apex angle prism unit is actually configured.

FIG. 9 is a block diagram showing a schematic configuration of a conventional shake prevention device.

FIG. 10 is a diagram illustrating a conventional automatic focus adjustment method.

[Explanation of symbols]

 5 AF microcomputer (control means) 7 AF actuator (change means) 45 Microcomputer (detection means) 47, 48 Shake detection means

Claims (2)

[Claims] 1. A shake prevention means for preventing a shake of an image pickup screen which occurs according to a shake at the time of shooting, and a lens group for focus adjustment so as to maximize a high frequency component of a video signal, thereby focusing. In a video camera provided with an automatic focus adjusting means for adjusting the position, a detecting means for detecting whether the shake preventing means is in an operating state or a non-operating state, and a lens group of the automatic focus adjusting means. A video camera, comprising: changing means for changing the responsive state, and control means for changing the responsive state of the lens group by the changing means in accordance with the state detected by the detecting means. 2. A shake preventing means having shake detecting means for detecting shake of an image pickup screen caused according to shake at the time of photographing and shake correcting means for performing predetermined shake suppressing correction according to the detection result of the shake detecting means. And a autofocus adjusting means for adjusting the focus position by driving the lens group for focus adjustment so that the high frequency component of the video signal becomes maximum, the lens group of the autofocus adjusting means And a control unit that changes the response state of the lens group by the change unit according to the detection result of the shake detection unit.