JPH11275431A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the response to transition and to return from a panning operation. SOLUTION: A shake proof control circuit 22 calculates an angular displacement θ from an angular velocity sensed by angular velocity sensors 18a, 18b and calculates a corresponding shake correction amount based on a focal distance (f) and the angular displacement θ. A cut-off frequency to limit the frequency band of the sensed angular velocity signal is determined from the shake correction amount. The cut-off frequency is changed in the order of the square of the shake correction amount when the shake correction amount is small, and the cut-off frequency rapidly gets higher when the shake correction amount increases. A line read from an image pickup element 12 and a horizontal position read from a line memory 28 are controlled depending on the shake correction amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging device,
More specifically, the present invention relates to an imaging device such as a video camera having a camera shake correction function.

[0002]

2. Description of the Related Art In recent years, a video camera equipped with an image stabilizing function equipped with image stabilization is generally used. As methods of the camera shake prevention function, there are optical correction and electronic correction.

In optical camera shake correction, a prism or lens member capable of displacing the optical axis is arranged in the middle of the optical path of photographing light incident on the image pickup device, and the optical axis is deflected in accordance with the camera shake to obtain an image due to camera shake. Offset the movement. The camera shake detection means is an angular velocity sensor such as a vibration gyro,
It is common to detect a shake component applied to a camera and to detect the angular displacement of the camera by integrating this output.

On the other hand, electronic image stabilization is often used in combination with a motion vector detection method for calculating the amount of motion of a camera from a change in a video signal between fields, and is stored in a motion vector detection field memory. A method of extracting a part from an image so that the motion of the image is removed is adopted. As another method of electronic camera shake correction, there has been proposed a method of using an angular velocity sensor for shake detection, cutting out an image output from an image sensor, and extracting a part of the image to offset the movement of the image, and outputting the cut out part. .

[0005] In the case of the electronic type, since a video signal is electronically processed, its correction cycle is a field cycle.
Therefore, while it is not possible to remove camera shake during the exposure time, there is an advantage that it can be made smaller and lighter than the optical system. In addition, by using a high-density, large-type image sensor, the resolution of an image cut out from an image signal is increased, and image quality degradation, which is disadvantageous compared to the optical type, is being improved.

In some cases, a video camera performs photographing while performing camera work such as panning or tilting for intentionally moving the camera. If image stabilization is enabled without change when shooting with these camera works, the image quality may be disturbed by hitting the end of the correction range, and the response to the direction intended by the photographer may be delayed. As a means to prevent this,
A configuration has been proposed in which the camera shake correction is restricted to reduce the correction ability (for example, 1993 Patent Application Publication No. 14).
No. 2614). Further, there has been proposed an invention that realizes a banning operation that does not give a photographer an uncomfortable feeling even when the focal length becomes a super telephoto range (Japanese Patent Application Publication No. 51466/1997).

[0007]

In the conventional panning operation control, when the level of a camera shake detection signal (or a processed signal thereof) exceeds a predetermined threshold, the shake correction capability is reduced. Therefore, in continuous video shooting, which is a video shooting, the movement at the time of transition to the panning mode becomes clear on the screen, resulting in an unnatural video.

In order to avoid this problem, there has been proposed an invention in which the shake correction characteristic is changed so that the shake correction ability changes smoothly with time (1996 Patent Application Publication No. 313950). Conversely, the responsiveness of shifting to and returning from the panning operation has deteriorated.

[0009] Further, by the extremely complicated anti-vibration control processing,
A configuration that realizes a smooth change of the shake correction characteristic and prevention of deterioration of the response has also been proposed. However, this proposal can be realized by an optical image stabilizing device in which the shake correcting means is placed before the zoom lens, but an optical or electronic image stabilizing device in which the shake correcting means is placed after the zoom lens. In the apparatus, setting parameters for the panning operation must be prepared for each change in the focal length, which is not practical.

An object of the present invention is to provide an image pickup apparatus which solves these problems.

That is, an object of the present invention is to provide an image pickup apparatus which can obtain a natural image during panning or tilting even if it has an image stabilizing function.

Another object of the present invention is to provide an image pickup apparatus capable of realizing a camera shake correction function having the same characteristics even when a lens is exchanged by an interchangeable lens system.

[0013]

According to a first aspect of the present invention, there is provided an image pickup apparatus comprising: a variable magnification photographing optical system; an image pickup means for converting an optical image by the variable magnification photographing optical system into an electric signal; A shake detecting means for detecting a shake applied to the imaging means, a shake correcting means for correcting a shake detected by the shake detecting means, and the shake correction using a limit value of a predetermined characteristic corresponding to a shake correction amount of the shake correcting means. Limiting means for limiting the correcting operation of the means.

2. An image pickup apparatus according to claim 1, wherein said restricting means changes said predetermined characteristic in accordance with a focal length of said zoom optical system.

The limiting means includes a normalizing means for normalizing a shake correction amount of the shake correcting means, and a predetermined limit value characteristic applied to the shake correction amount standardized by the normalizing means, and And a shake limiter that limits the correction operation of the shake corrector based on the limit value calculated by the limit value calculator.

The normalizing means normalizes the amount of shake correction of the shake correcting means based on the focal length and the maximum shake correction range of the shake correcting means.

The shake correcting means includes an optical element for moving the optical axis of the variable magnification photographing optical system.

The limiting means has a band limiting means for limiting the band of the shake signal detected by the shake detecting means.

The shake correcting means is an electronic extracting means for electronically extracting a part from the entire image screen of the image capturing means.

Further, there is provided storage means for storing the focal length of the variable-magnification photographing optical system, the surplus change amount and the pixel size of the position of the extracted image in the entire imaged screen, and the output video format.

In accordance with the output video format, the detection frequency of the shake detecting means is set to an integral multiple of the least common multiple of the field frequency.

The limit value of the predetermined characteristic is determined in proportion to the n-th power of the shake correction amount (where n is an integer of 1 or more).

[0023]

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

FIG. 1 is a schematic block diagram showing an embodiment of the present invention in which a video camera is provided with an electronic image stabilizing function. Reference numeral 10 denotes a photographing lens, and 12 denotes a CCD image pickup device that converts an optical image of the photographing lens 10 into an electric signal. The output signal of the image sensor 12 is amplified by the amplifier 14 and input to the camera signal processing circuit 16. The camera signal processing circuit 16 performs well-known camera signal processing such as gain adjustment, color balance adjustment, and γ correction on the image signal from the amplifier 14 to form and output a standard format video signal.

Reference numeral 18a denotes an angular velocity sensor in the pitch direction,
b is an angular velocity sensor in the yaw direction; 20a and 20b are amplifiers for amplifying the outputs of the angular velocity sensors 18a and 18b; 22 is the camera shake from the outputs of the amplifiers 20a and 20b (that is, the angular velocity in the pitch direction and the angular velocity in the yaw direction). This is a vibration control circuit that detects the angle and the angle and cancels camera shake. The anti-vibration control circuit 22 is specifically formed of a microcomputer, and includes an A / D converter for converting the outputs of the amplifiers 20a and 20b into digital signals. Reference numeral 24 denotes an anti-shake on / off switch for instructing the anti-shake control circuit 22 by the user to turn on or off the anti-shake control. A CCD drive circuit for reading, a line memory for selecting an output image portion in the line direction, and a memory control circuit for controlling the line memory in accordance with a command from the image stabilizing control circuit are shown.

The anti-shake control circuit 22 calculates the angular displacement by integrating the detected angular velocities (outputs of the amplifiers 20a and 20b), and obtains the obtained angular displacement, that is, the camera shake angle θ and the photographic lens 10 From the focal length f, the amount of pixel movement due to the shake on the image sensor 12 (approximately equivalent to fx tan θ) is calculated. Read the image signal.

An image area extracted by electronic image stabilization control will be briefly described. FIG. 2 shows a relationship between an image obtained from the entire imaging area of the image sensor 12 and an image cut out from the image and output. Reference numeral 32 denotes an entire imaging area of the image sensor 12, and reference numeral 34 denotes a cutout range for cutting out an image from the entire imaging area 32 for output, and coordinates (V0, H0) of an upper left corner thereof.
Is the position coordinate of the extraction range 34. Cutting range 34
The image extracted or extracted from the image is reorganized into an output image size or a pixel configuration as shown in FIG. 2B and output.

The camera shake can be corrected by moving the position of the cut-out range 34 on the entire imaging area 32 so as to cancel the camera shake. The position changeable range of the cutout range 34, that is, the camera shake correction capability, is determined by the difference between the number of horizontal and vertical pixels between the entire imaging area 32 and the cutout range 34 (hereinafter, referred to as a surplus pixel number). In the cutout range 34, a reference position (initial position) when camera shake correction is off is determined in advance. The reference position is usually the center of the entire imaging area 32.

As a method of extracting the image of the cut-out range 34, the entire image of the entire image pickup area 32 is stored in a field memory, and while only the image of the cut-out range 34 is read, the image is read out horizontally and vertically so as to have the display size. There is a method of interpolating and a method of using a high-density, high-pixel type large-sized image sensor so that the cutout range 34 satisfies the number of scanning lines and the number of horizontal pixels necessary for the standard video signal in advance.

In the present embodiment, a general-purpose PA
L CCD image sensor is used, and the output video signal is NTSC
It shall conform to the method. Since the PAL CCD image sensor has a high pixel density in the vertical direction, in the vertical scanning direction, the CCD drive circuit 26 determines the number of lines to be swept at high speed within a range of extra lines for the NTSC standard. If it is changed according to the displacement, the cutout position in the vertical direction can be changed. In the horizontal scanning direction, the line memory 28 and the memory control circuit 30 change the relationship between the write start pixel position and the read start pixel position in the line memory 28 while performing enlargement processing by the aspect ratio. , The horizontal screen position can be changed.

In the embodiment shown in FIG.
In the vertical direction, a desired scanning line portion is read from the image sensor 12 by causing the CCD driving circuit 26 to perform high-speed sweeping control, and the line image processed by the camera signal processing circuit 16 is read in the horizontal scanning direction. While writing to the line memory 28, the memory control circuit 30 changes the read position of the line image in the line memory 28 according to the pixel movement amount of the shake correction, and enlarges the image by an amount corresponding to the aspect ratio (changes the memory read rate). Then, it can be enlarged by thinning out and reading out.). The signal read from the line memory 28 is subjected to color processing and the like by the camera signal processing circuit 16, converted into a standard format video signal, and output.

Next, the anti-shake control operation of the anti-shake control circuit 22 will be described in detail with reference to FIGS. One of the objects of the present embodiment is to smoothly switch the anti-shake control to the panning operation. In this embodiment, in accordance with the shake correction amount, the limit amount is changed with a characteristic proportional to the n-th power of the shake correction amount (n is an integer of 1 or more) to automatically adjust the degree of effectiveness of the shake correction.

FIG. 3 shows a flowchart of a process for calculating an angular displacement by integrating the angular velocity signals detected by the angular velocity sensors 18a and 18b. This process is an interrupt process of a fixed period. In the present embodiment, it is 10 times the field frequency, that is, 600 Hz in the case of the NTSC system.
At a frequency of This frequency corresponds to the sampling frequency of the angular velocity signal, that is, the calculation frequency of the angular displacement. The interrupt signal for this processing can be generated by a known method. For example, the clock signal is counted up or down, and an interrupt signal is generated when 1/600 second is counted. The anti-vibration control circuit 22 converts the angular velocity signal into a digital signal using an A / D converter having a built-in signal, and in this embodiment, in order to facilitate understanding,
The A / D converter is operating in scan mode,
It is assumed that an input signal is converted into a digital signal.

First, the DC component is removed from the angular velocity signal sampled by the A / D conversion (S1), and the A of the angular velocity signal is removed.
The band of the C component is limited (S2). This band limitation is actually a high-pass filter process similar to that for removing the DC component. The difference is that the cutoff frequency is a fixed value in S1, whereas it is variable in S2. By changing the cutoff frequency from a low band to a high band, a desired band component is extracted. In the present embodiment, during a camera work operation such as panning, the cutoff frequency is increased to reduce the vibration suppression capability.
The cutoff frequency is reduced for camera shake correction. Further, the cutoff frequency of S2 is adjusted in order to prevent unnaturalness of the screen when the camera strikes the correction end in an attempt to correct a camera shake larger than the limit of the shake correction possible range. How to control the cutoff frequency will be described later with reference to FIG.

An angular displacement is calculated by integrating the band-limited angular velocity signal (S3). The calculated angular displacement corresponds to the shake angle applied to the camera body. The variable m of the number of times of deflection angle calculation is incremented (S4). If m is equal to 10 (S5), 0 is substituted for m (S6), the interrupt processing is terminated, and if m is not equal to 10 (S5). ), And the process ends. That is, if there are 10 interrupts in one field period, m is initialized to 0.

Steps S1 to S3 are executed for each of the pitch direction and the yaw direction.

The process shown in FIG. 4 is performed once per field,
Be executed. Specifically, when m = 0,
That is, it is executed at the end of the current field.

It waits until m becomes 0 (S11). When the interrupt process shown in FIG. 3 is executed ten times in the current field, m is initialized (S6). When m = 0 (S1
1), a shake correction amount is calculated (S12). As described above, the shake correction amount is obtained as f × tan θ from the shake angle θ and the focal length f of the optical system. A limit value for limiting the shake correction capability is calculated from the calculated shake correction amount (S1).
3). Specifically, the calculated limit value is a cutoff frequency applied in S2 of FIG.

Next, the target position coordinates (V
(0, H0) is calculated (S14). Here, the target position coordinates are given by the following equation. That is, V0 = vertical origin position ± the number of moving pixels for correcting the deflection angle in the pitch direction = vertical origin position ± (−1) × focal length × tan (pitch deflection angle) / vertical cell size H0 = vertical origin position ± Number of moving pixels for correcting the deflection angle in the yaw direction = vertical origin position ± (−1) × focal length × tan (yaw deflection angle) / horizontal cell size. From these equations, the number of moving pixels required for shake correction can be obtained.

A predetermined command is output to the CCD drive circuit 26 and the memory control circuit 30 using the calculated target position coordinates (V0, H0) as reference coordinates of the cut-out range (S1).
5). The CCD drive circuit 26 and the memory control circuit 30
It operates to execute cutout as instructed in the next field. Thereafter, the process returns to S11 in preparation for the next field, and waits for the execution of ten integration processes.

FIGS. 5 and 6 show cutoff frequency characteristics with respect to the amount of shake correction. FIG. 5 shows the characteristics at the telephoto end, and FIG. 6 shows the characteristics at the wide end. In both FIG. 5 and FIG. 6, the horizontal axis represents the shake correction amount, and the vertical axis represents the cutoff frequency. Since the cutoff frequency is a function of the amount of shake correction, the vibration suppression capability is finely controlled according to the degree of shake correction, and smooth switching can be performed even during a panning operation. In this embodiment, the maximum cutoff frequency is 6 Hz. This is because the main camera shake frequency component is 5
Hz or less.

In a portion where the camera shake correction amount is small, the cutoff frequency is made proportional to the square of the correction amount.
This is because the cutoff frequency is sharply increased when the shake correction amount increases, and when the shake correction amount is near zero, the cutoff frequency is reduced as much as possible to enhance the image stabilization effect.

When it is desired to expand the range in which the anti-shake effect is high (the range in which the shake correction amount is near zero) as much as possible, the order with respect to the shake correction amount is increased, and when the shake correction amount becomes larger, the cutoff frequency is increased. What is necessary is just to set a coefficient etc. so that it may rise steeply.

In the tele area where the focal length is long, the displacement speed of the subject with the same shake correction amount tends to be higher than in the wide area. This is because the shake angle displacement for which the same shake correction amount is calculated is smaller in the tele region having a longer focal length, and the shake angle is easily increased by the panning speed. Therefore, in order to prevent a phenomenon in which the shake angle becomes large and the captured image is disturbed by colliding with the shake correction end, it is necessary to increase the cutoff frequency more quickly on the tele end side as shown in FIG.

As described above, by changing the cutoff frequency characteristic in accordance with the focal length, it is possible to achieve both the anti-vibration control for the panning operation and the end collision prevention with the same limiting parameter.

According to the processing described with reference to FIGS. 3 to 6, in the present embodiment, the limit amount for the shake correction amount, that is, the cutoff frequency is changed in accordance with the shake correction amount, whereby the shake correction amount is reduced. Since the limit changes continuously, switching between image stabilization control during normal shooting and image stabilization control during panning becomes smooth. In particular, by changing the cutoff frequency in proportion to the n-th power of the shake correction amount (n is an integer of 1 or more), the correction amount is sharply limited at a predetermined shake correction amount, or the correction amount is not limited as much as possible. Flexible settings, such as a wider range, are possible. By setting appropriate limiting characteristics in accordance with the focal length, it is possible to prevent disturbance of a captured image due to a collision with a shake correction end and perform image stabilization control during a panning operation with the same band limiting parameter.

In this embodiment, the PAL CCD image pickup device and the line memory are used, but the same operation and effect can be realized by controlling the image extraction position on the field memory. A large-sized or ultra-high-pixel type CCD image sensor which does not need to perform enlargement control may be used. In this embodiment, the angular velocity sensor is used as the shake detection means. However, an acceleration sensor may be used. In this case, the integration process may be performed once inside or outside the image stabilization control circuit 22. Obviously, the calculation of the deflection angle displacement amount may be performed by software processing or hardware processing. Furthermore, in the present embodiment, the band limiting unit that limits the band of the shake signal is used as the shake correction limiting unit, but the present invention is not limited to this. For example, the restriction may be made by changing the shake correction gain. In that case, the motion vector detecting means can be used as the shake detecting means.

In the processing described with reference to FIGS.
Although the limit value in the panning mode is mainly determined according to the shake correction amount, it is necessary to set a limit value characteristic for each focal length, which makes the image pickup apparatus using a zoom lens slightly more complicated.

Next, an embodiment suitable for an image pickup apparatus using a zoom lens or an interchangeable lens type image pickup apparatus will be described.
FIG. 7 shows a schematic block diagram of the embodiment. In this embodiment, an optical image stabilizing device that corrects camera shake by moving a shift lens for image stabilization perpendicular to the optical axis is used.

Reference numeral 110 denotes an inner focus type photographing lens, which includes a fixed lens 112 and a zoom lens 11.
4, an aperture 116, an anti-vibration shift lens 118 and a focus lens 120.

Reference numeral 122 denotes an image sensor for converting an optical image obtained by the photographing lens 110 into an electric signal, and 124 denotes an image sensor 12
Reference numeral 126 denotes an amplifier for amplifying the output of the amplifier 2, and reference numeral 126 denotes a camera signal processing circuit that performs a known camera signal processing on the output signal of the amplifier 124.

The motor drive circuit 128 has a stepping
The zoom lens 114 is moved in the optical axis direction by the motor 130. The motor drive circuit 132 moves the anti-vibration shift lens 118 in a direction perpendicular to the optical axis by a stepping motor 134. The encoder 136 detects the position of the shift lens 118 for image stabilization. The amplifier 138 amplifies the output of the encoder 136, and the subtractor 140 uses the control signal from the system control circuit
8 is subtracted and applied to the motor drive circuit 132.
The motor drive circuit 142 includes a stepping motor 144
Moves the focus lens 120 in the optical axis direction.

The system control circuit 146 is a microcomputer that performs overall control, and
8 and 142, and outputs the target value of the image stabilization control to the subtractor 140.

Reference numeral 148 denotes a zoom key operated by the user to change the focal length.
Moves the zoom lens 114 in a designated direction by the motor drive circuit 128 and the motor 130 in response to the operation of the zoom key 148.

150a is an angular velocity sensor in the pitch direction, 1
50b is a yaw direction angular velocity sensor. The detection outputs of the angular velocity sensors 150a, 150b are output from the amplifiers 152a,
It is amplified by 52b and applied to the system control circuit 146. Reference numeral 154 denotes an anti-vibration on / off switch.

The system control circuit 146 includes an amplifier 152
The analog outputs a and 152b are converted into digital signals, integrated, and the angular velocity is converted into each displacement. The system control circuit 146 calculates the amount of movement of the captured image due to the shake on the image sensor 122 (substantially corresponds to f × tan θ) from the obtained angular displacement, that is, the swing angle θ and the focal length f of the imaging lens 110. By moving the shift lens 118 perpendicular to the optical axis so as to move in the direction opposite to the movement direction due to shake,
Correct the shake. Specifically, the system control circuit 146
Outputs a target value for shake correction to the subtractor 140. The subtractor 140 compares the output of the amplifier 138 (specifically, a signal indicating the position of the shift lens 118) with a target value, and applies the difference signal to the motor drive circuit 132. As a result, the shift lens 118 moves to a position corresponding to the target value.

The system control circuit 146 also controls the zoom lens 114 and the focus lens 120. That is, the system control circuit 146 controls the motor drive circuit 128 to move the zoom lens 114 in a specified direction in response to a signal from the rotary operation type zoom switch 148 in which the resistance value changes according to the pressing force. The system control circuit 146 controls the motor drive circuit 142 to move the focus lens 120 back and forth so that the focus signal obtained from the camera signal processing circuit 126 is maximized,
An optical image is formed on the imaging surface of the imaging element 122.

Referring to FIG. 8, system control circuit 146
Will be described. In this embodiment, the shake correction amount is standardized by the focal length and the maximum correction limit,
A limit value is calculated with a predetermined limit characteristic according to the standardized shake correction amount. Therefore, only having one kind of limiting characteristic,
It becomes possible to correspond to all focal lengths.

Also in this embodiment, the angular velocity sensors 150a, 150
The angular displacement is calculated by integrating the angular velocity signal detected at 50b, and the shake correction amount and its limit value are calculated. In the first embodiment, the shake correction cycle is the field cycle. However, in the present embodiment, since the optical vibration proof is used, the shake sampling and the shake correction cycle are made to coincide with each other, and during the charge accumulation time of the image sensor, This also makes it possible to correct camera shake. The process shown in FIG. 8 is actually a periodic interrupt process executed by the system control circuit 146. In this embodiment, the process is executed at a frequency of, for example, 1 kHz. For example, an oscillation clock divided by a predetermined division ratio is counted up (or down), and the time corresponding to 1 millisecond is counted.
You only need to interrupt it. The system control circuit 146 includes:
An A / D converter for converting the analog outputs of the amplifiers 152a and 152b into digital signals is built in.
It is assumed that the converter is always operating in the scan mode.

The system control circuit 146 removes a DC component from the angular velocity signal sampled by the A / D conversion (S
21), band-limiting the AC component of the angular velocity signal (S2)
2). This band limitation is actually a high-pass filter process similar to that for removing the DC component. The difference is that the cutoff frequency is a fixed value in S11 but is variable in S22. By changing the cutoff frequency from a low band to a high band, a desired band component is extracted. In the present embodiment, as in the previous embodiment, during a camera work operation such as panning, the cutoff frequency is increased to reduce the vibration suppression ability.
The cutoff frequency is reduced for camera shake correction. Further, the cutoff frequency of S22 is adjusted in order to prevent unnaturalness of the screen when colliding with the correction end in order to correct a camera shake larger than the limit of the shake correction possible range.

An angular displacement is calculated by integrating the band-limited angular velocity signal (S23). The calculated angular displacement corresponds to the shake angle applied to the camera body. Next, a shake correction amount (shift target value) is calculated (S24). As described above, the shake correction amount is obtained as f × tan θ from the shake angle θ and the focal length f of the optical system. The calculated shake correction amount is normalized by the maximum correction limit (the movement limit of the shift lens 118) (S25). That is, pitch standardized shake correction amount = pitch shake correction amount / pitch maximum shift limit × 100 (%) yaw standardized shake correction amount = yaw correction amount / yaw maximum shift limit × 100 (%).

From the standardized shake correction amount calculated in this way, a limit value for limiting the shake correction capability is calculated (S2).
6). The calculated limit value is, specifically, the cutoff frequency applied in S22. The calculated cutoff frequency is applied in the next band limitation process. For example,
When the cutoff frequency is large, the shake correction effect is reduced with respect to a shake having a shake frequency equal to or lower than the cutoff frequency. Next, the correction amount calculated in S24 (shift lens 11
8 is output to the subtractor 140 (S27).

FIG. 9 shows the characteristic of the limit value (cutoff frequency) with respect to the standard value of the shake correction amount. The horizontal axis indicates the normalized shake correction amount, and the case where the correction is performed by shifting to the maximum shift limit is set to 100%. The normalized shake correction amount is
In other words, it indicates the ratio of the correction amount necessary to correct the current shake. The vertical axis is the cutoff frequency serving as the limit value. As in the previous embodiment, the cutoff frequency is a function of the square of the normalized shake correction amount.

The maximum shift limit is determined as follows. FIG. 10A shows a change in the effective image circle diameter with respect to the focal length change, and FIG. 10B shows a change in the maximum correction range (maximum shift limit) with respect to the focal length. FIG.
In (a), the horizontal axis indicates the focal length, and the vertical axis indicates the effective image circle diameter. In FIG. 10B, the horizontal axis represents the focal length, and the vertical axis represents the maximum correction range.

In FIG. 10A, A is the shift lens 11.
8 is a value obtained by converting the mechanical maximum moving distance of 8 into an effective image circle diameter, and 160 indicates that even if the shift lens 118 is mechanically moved to the maximum moving limit at all focal lengths from wide to tele, The photographing screen shows characteristics of the photographing lens in which vignetting does not occur. The maximum correction range for the lens having the characteristic 160 is a constant value B shown in FIG. On the other hand, as shown by the characteristic 162, when the image diameter becomes larger than A only on the telephoto side from the focal length C, the shift lens 118 is shifted to the maximum mechanically movable position on the wide side from the focal length C. Then, a part of the shooting screen is vignetted. Therefore, the maximum correction range for the lens of the characteristic 162 decreases as the characteristic 164 is shown in FIG. In general, the lens optical system is designed to have the characteristic 162, and the size of the lens is often reduced. As described above, even when the maximum correction range changes as the characteristic 164 according to the focal length, the shake correction amount is standardized by the maximum correction range, so that the limiting characteristic does not change for each focal length. In both cases (i.e., without having a large number of characteristic change parameters), prevention of end collision and smooth transition / cancellation of the panning operation can be realized.

The determination of the limit value based on the standardized shake correction amount is as follows.
The present invention is also applicable to the electronic shake correction system in the embodiment shown in FIG. FIG. 11 shows a flowchart in which the determination of the limit value based on the normalized shake correction amount is introduced into the embodiment shown in FIG.

It waits until m becomes 0 (S31). When the interrupt process shown in FIG. 3 is executed ten times in the current field, m is initialized (S6). When m = 0 (S3
1), a shake correction amount is calculated (S32). As described above, the shake correction amount is obtained as f × tan θ from the shake angle θ and the focal length f of the optical system. From the calculated shake correction amount, the target position coordinates (V0, H0) of the cutout range are calculated in a manner similar to S14 (S33). As a result, the number of moving pixels required for shake correction is obtained.

The calculated shake correction amount is normalized according to the following equation (S34). That is, pitch standardized shake correction amount = pitch shake correction amount / vertical pixel size / vertical surplus pixel number / 2 × 100 (%) yaw standardized shake correction amount = yaw shake correction amount / horizontal pixel size / horizontal surplus pixel number / It is 2 × 100 (%). In the embodiment shown in FIG.
The CCD image pickup device for AL 12 (582V × 752H) was used. Assuming that 485 vertical lines of the NTSC standard are cut out from the PAL image sensor 12, the number of extracted pixels in the horizontal direction is 627H from the aspect ratio. Therefore, the surplus pixels are 97
V × 125H, and the correction direction becomes positive or negative in accordance with the direction of camera shake. Therefore, 規格 of the number of surplus pixels is used for normalization.

A limit value (cutoff frequency) is calculated from the obtained normalized shake correction amount (S35). Using the target position coordinates (V0, H0) calculated in S33 as the reference coordinates of the cutout range, a cutout command is output to the CCD drive circuit 28 and the memory control circuit 30 (S36). Then, the process returns to S31 in preparation for the next field, and waits until the integration process is performed ten times.

FIG. 12 is a characteristic diagram of the limit value (cutoff frequency) for the normalized shake correction amount used in S35 of FIG. The horizontal axis shows the normalized shake correction amount, and the vertical axis shows the cutoff frequency. However, on the horizontal axis, 100% is the case where the correction is performed using all 1/2 of the surplus pixels, which is the maximum correction limit. As in the previous embodiment, the cutoff frequency is a function of the square of the normalized shake correction amount. Here, in order to prevent a phenomenon in which the shake angle becomes large and collides with the shake correction end and the captured image is disturbed, in FIG. 12, the cutoff frequency is sharply increased as the shake correction is closer to the maximum correction limit. Is set to

The shake correction amount calculated according to the camera shake is standardized within the maximum shake correction range, and the limit value of the shake signal is determined according to the normalized shake correction amount. A smooth panning mode transition can be realized even with a camera whose effective image circle diameter changes accordingly. Further, similar panning characteristics can be obtained by simple parameter setting regardless of the image stabilization method.

In the above embodiment, smooth panning processing can be realized with simple setting parameters. Next, similar panning processing is performed not only in the case of the image stabilization method but also in the case where the lens, the image sensor, and the video signal format are different. A description will be given of an embodiment which can be performed and can bring out uniform anti-vibration performance. FIG. 13 shows a schematic block diagram of the embodiment. This embodiment is applied to an interchangeable lens type video camera.

This embodiment comprises a lens unit 210 and a camera body 240, and the lens unit 210 is detachable from the camera body 242.

The raise unit 210 is an inner focus type, and includes a fixed lens 212 and a zoom lens 21.
4, an aperture 216, a fixed lens 218, and a focus lens 220. The motor drive circuit 222 moves the zoom lens 214 in the optical axis direction by the stepping motor 224. The motor drive circuit 226 moves the focus lens 220 in the optical axis direction by the stepping motor 228. 230 communicates with the camera body 240 to control the lens unit 210,
This is a camera control circuit composed of a microcomputer that sends ten pieces of information to the camera body 240. Reference numeral 232 denotes a rotary operation type zoom switch whose resistance value varies according to the pressing force.

The lens control circuit 230 controls the motor drive circuit 222 in accordance with the operation of the zoom switch 232 to move the zoom lens 214 in the direction indicated. The lens control circuit 230 also uses the motor drive circuit 226 and the motor 228 based on the focus signal information from the camera body 240 to maximize the focus signal information.
0 is moved in the optical axis direction.

In the camera body 240, reference numeral 242 denotes a C for converting an optical image by the lens unit 210 into an electric signal.
It is a CD-type image sensor. The output signal of the image sensor 242 is amplified by the amplifier 244, and is output to the camera signal processing circuit 246.
Is input to The camera signal processing circuit 246 includes the amplifier 24
A known camera signal processing such as gain adjustment, color balance adjustment, and γ correction is performed on the image signal from No. 4 to form and output a standard format video signal.

Reference numeral 248a denotes an angular velocity sensor in the pitch direction;
48b is an angular velocity sensor in the yaw direction, 250a and 250b
Is an amplifier for amplifying the outputs of the angular velocity sensors 248a and 248b. Reference numeral 252 denotes a system control circuit including a microcomputer which communicates with the lens control circuit 230 of the lens unit 210 and controls the whole.
A camera shake control module 254 for detecting the camera shake of the camera main body and its angle from the outputs of a and 20b (that is, the angular velocity in the pitch direction and the angular velocity in the yaw direction) and canceling the camera shake is provided. The system control circuit 252 includes an amplifier 250a,
An A / D converter for converting the output of 250b into a digital signal is built in. Reference numeral 256 denotes an anti-vibration on / off switch for instructing the system control circuit 252 to turn on / off anti-vibration. Reference numeral 258 denotes a memory such as an EEPROM, which stores camera-specific information, for example, information such as the pixel size of the image sensor 242, the number of surplus pixels, and the output video format.

Reference numeral 260 denotes a CCD drive circuit for driving the image pickup device 242 in accordance with a command from the image stabilization control module 254 of the system control circuit 252 to read a desired line portion, and 262 selects an output image portion in the line direction. 264 is a line memory for performing anti-vibration control module 25.
4 is a memory control circuit that controls the line memory 262 in accordance with a command from

The image pickup device 242 converts the optical image from the lens unit 210 into an electric signal, and outputs the electric signal to the amplifier 24.
4 and applied to the camera signal processing circuit 246. The camera signal processing circuit 246 performs well-known camera signal processing on the output of the amplifier 244 and outputs an NTSC video signal. The camera signal processing circuit 246 also generates a focus signal from the output of the amplifier 244 and supplies the focus signal to the system control circuit 252. The system control circuit 252 transmits the focus signal from the camera signal processing circuit 246 to the lens unit 2.
10 to the lens control circuit 230.

The anti-vibration control module 254 of the system control circuit 252 calculates the angular displacement by integrating the angular velocities (outputs of the amplifiers 20a and 20b) detected by the angular velocity sensors 248a and 248b, and obtains the obtained angular displacement, ie, the angular displacement. From the camera shake angle θ and the focal length f of the lens unit 210, the amount of pixel movement due to the shake on the image sensor 242 (substantially f × t
anθ. ), And the CCD drive circuit 26 and the memory control circuit 26
4 is controlled in the same manner as in the embodiment shown in FIG.

Next, the operation of the image stabilization control module 254 will be described with reference to FIG. 14, FIG. 15, and FIG. FIG.
4 is a flowchart of an initialization routine of the image stabilization control module 254, which is executed once after the power is turned on.
FIG. 15 is a flowchart of a routine for calculating the deflection angle, which is an interrupt processing routine similar to FIG. FIG. 16 is a flowchart of the same process as FIG.
Executed once in the field.

First, FIG. 14 will be described. The camera-specific information is read from the memory 258 (S41). Image sensor 24
The vertical / horizontal pixel sizes are stored in memory α, respectively.
v, αh, and the numbers of surplus pixels in the vertical / horizontal directions are stored in the memories βv, βh, respectively. When the PAL image sensor is used in the NTSC camera, βv = 97, βh
= 125. Next, it is determined whether the camera is the NTSC system or the PAL system from the read output video format information (S42).

In accordance with the output video format, the interrupt frequency of the interrupt process shown in FIG. 15, that is, how many times to interrupt one field is determined (S43, S44). The interrupt frequency is a sampling frequency of the angular velocity signal, and is also a frequency for calculating angular displacement by various filter processes. It is desirable that the sampling frequency be constant regardless of the output video format. This is because, if the sampling frequency is different, the frequency characteristics in various filter processes will change. In addition, the frequency of the camera shake correction is an electronic correction, and is in units of a field frequency. It is preferable that sampling be synchronized with the field cycle because handling becomes easier. In this embodiment, information indicating how many times one field is interrupted is set as the sampling frequency in the memory K. The sampling frequency is set to the least common multiple (300H) of the field frequency of the NTSC system and the PAL system.
By setting an integer multiple of z) and 600 Hz in this embodiment, the frequency characteristics in the angular velocity signal processing by the program can be the same in both the NTSC system and the PAL system.

In the case of the NTSC system (S42), the interrupt frequency is set to 600 Hz and the number of interrupts K in one field is set to 10 (S43). PA
In the case of the L system (S42), the interrupt frequency is set to 600 Hz.
And the number of interrupts K in one field is set to 12 (S44).

Initial communication is performed with the lens control circuit 230 to obtain focal length information (zoom lens position information) from the lens control circuit 230. In particular, the focal lengths ft and fw at the telephoto end and the wide end and the position information are stored (S4).
6), the initial setting process ends.

FIG. 15 shows the angular velocity sensors 150a, 150
4 is a flowchart of a process for calculating an angular displacement by integrating the angular velocity signal detected in b. This process is a periodic interrupt process executed by the system control circuit 252.
43 and the frequency determined in S44 (in this embodiment, 60
0 Hz (10 times the field frequency in the case of NTSC,
In the case of PAL, this is performed at 12 times the field frequency)). This frequency corresponds to the sampling frequency of the angular velocity signal, and corresponds to the calculation frequency of the angular displacement. The interrupt signal for this processing can be generated by a well-known method.
When / 600 seconds have been counted, an interrupt signal is generated. Similarly to the above-described embodiment, the system control circuit 252 converts the angular velocity signal into a digital signal using an A / D converter having a built-in signal.
It is assumed that the / D converter operates in the scan mode and always converts an input signal into a digital signal.

First, the DC component is removed from the angular velocity signal sampled by the A / D conversion (S51), and the AC component of the angular velocity signal is band-limited (S52). This bandwidth limitation is
Actually, it is the same high-pass filter processing as that for removing the DC component. The difference is that the cutoff frequency is a fixed value in S51, but variable in S52. By changing the cutoff frequency from a low band to a high band, a desired band component is extracted. In this embodiment, during a camera work operation such as panning, the cutoff frequency is increased to reduce the vibration suppression capability, and during normal shooting, the cutoff frequency is reduced for camera shake correction. In addition, the cutoff frequency of S52 is adjusted to prevent unnaturalness of the screen when the camera strikes the correction end in an attempt to correct a camera shake larger than the limit of the shake correction possible range. How to control the cutoff frequency will be described later with reference to FIG.

An angular displacement is calculated by integrating the band-limited angular velocity signal (S53). The calculated angular displacement corresponds to the shake angle applied to the camera body. The variable m of the number of times of deflection angle calculation is incremented (S54). If m is equal to the value of the memory K (S55), 0 is substituted for m (S5).
6), interrupt processing is terminated, and if m is not equal to the value of the memory K (S55), the processing is terminated as it is. That is, if there are K interrupts in one field period, m is initialized to 0.

Steps S51 to S53 are executed for each of the pitch direction and the yaw direction.

The process shown in FIG. 16 is executed once for one field. That is, the processing is performed, and the processing shown in FIG. 15 is executed K times, and the processing shown in FIG. 16 is executed until the next first execution, that is, at the end of the current field.

The process waits until m becomes 0 (S61). When the interrupt process shown in FIG. 15 is executed K times in the current field, m is initialized (S56). When m = 0 (S
61) Inquire the lens control circuit 230 to obtain the current zoom lens position information (S62). The current focal length f is calculated from the focal lengths ft and fw at the telephoto end and the wide end obtained earlier and the current zoom lens position (S63). That is, f = ft− (ft−fw) / zoom stroke × (tele end position−current position) where zoom stroke = tele end position−wide end position. A shake correction amount is calculated from the obtained current focal length f (S64). As described above, the shake correction amount is obtained as f × tan θ from the shake angle θ and the focal length f of the optical system. From the calculated shake correction amount, the target position coordinates (V0, H0) of the cutout range are calculated according to the following equation (S6).
5). V0 = vertical origin position ± the number of moving pixels for correcting the shake angle in the pitch direction = βv / 2 ± (−1) × pitch shake correction amount / αv H0 = vertical origin position ± the shake angle in the yaw direction The number of moving pixels to be performed = βh / 2 ± (−1) × the amount of yaw shake correction / αh As a result, the number of moving pixels required for shake correction is obtained.

The calculated shake correction amount is normalized according to the following equation (S66). That is, pitch standardized shake correction amount = pitch shake correction amount / αv / β
v / 2 × 100 (%) Yaw standardized shake correction amount = Yaw shake correction amount / αh / βh /
It is 2 × 100 (%). PAL CCD image sensor 1 for NTSC camera
2 (582V × 752H), if 485 vertical lines of the NTSC standard are cut out from the PAL image sensor, the number of extracted pixels in the horizontal direction is 627H from the aspect ratio. Therefore, the surplus pixel β is 97V × 125H.

A limit value (cutoff frequency) is calculated from the obtained normalized shake correction amount (S67). The cutoff frequency has a characteristic as shown in, for example, 12, and as the shake correction amount approaches the maximum correction limit, the cutoff frequency increases sharply.

The target position coordinates (V0, V0,
A cutout command is output to the CCD drive circuit 260 and the memory control circuit 264 using H0) as the reference coordinates of the cutout range (S68). Then, in preparation for the next field, S61
And waits until K integration processes are performed.

In the embodiment shown in FIG. 13, an image stabilization operation can be realized by a common image stabilization control program simply by initializing the unique states of the camera and the lens. Further, since the limit value of the vibration suppression ability at the time of panning can also be a standardized characteristic, the same image stabilization control module can be used for different combinations of the lens unit and the camera body. For example, even if a lens unit having different lens characteristics is mounted on the same camera body, or a camera body having different performance on a lens having the same characteristics, for example, a high-density type large CCD
Even if a camera using an image sensor or a camera of a different video system such as the NTSC system and the PAL system is mounted, the same image stabilization performance can be obtained. In particular, the same image stabilization control module can be applied to any combination of the lens and the camera body, so that the cost can be significantly reduced.

[0096]

As can be easily understood from the above description, according to the present invention, the limit value (for example, cut-off frequency) of the shake signal is determined according to the shake correction amount, so that the shake signal is continuously output. Thus, the mode transition between image stabilization control during normal shooting and control during panning can be made smooth. In particular, by making the limit value proportional to the n-th power of the shake correction amount (n is an integer of 1 or more), a sharp limit can be imposed at a predetermined shake correction amount,
This makes it possible to flexibly set the anti-vibration characteristics according to the situation, such as not to impose restrictions as much as possible. Also, by setting appropriate limiting characteristics according to the focal length, it is possible to realize the prevention of disturbance of the captured image due to the collision with the shake correction end and the anti-shake control during the panning operation with the same band limiting parameter. .

Further, by standardizing the shake correction amount with the focal length and the maximum correction limit, an imaging apparatus in which the focal length and / or the effective image circle diameter changes only by preparing the limiting characteristic for the standardized shake correction amount. However, smooth transition and return of the panning mode can be made smooth and natural. With simple parameter settings, regardless of the anti-vibration method,
Uniform panning characteristics can be obtained.

By modularizing the image stabilization control program, the image stabilization operation corresponding to a wide range of devices can be realized by the common image stabilization control program only by initializing the unique state of the camera and / or the lens. In addition, since the limit value of the vibration suppression ability during panning can be standardized characteristics, even if any lens such as an interchangeable lens camera is mounted, the same lens can be used with a high-density type large CCD image sensor Cameras using NTSC, NTSC and P
Even if cameras of different video formats such as the AL system are mounted, it is possible to provide a high value-added imaging apparatus that can realize a camera shake correction function having the same characteristics. In particular, since the same module can be applied to any combination of camera systems, the cost can be significantly reduced and an inexpensive imaging device can be provided.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a relationship between an entire imaging area and a cutout range.

FIG. 3 is a flowchart of a process for calculating an angular displacement from angular velocity signals detected by the angular velocity sensors 18a and 18b.

4 is a flowchart of a process for determining a cutout range from the angular displacement calculated in the process shown in FIG.

FIG. 5 is a cutoff frequency characteristic with respect to a shake correction amount at a telephoto end.

FIG. 6 is a cutoff frequency characteristic with respect to a shake correction amount at a wide end.

FIG. 7 is a schematic configuration block diagram of a second embodiment of the present invention.

8 is a flowchart of an image stabilization control operation of the embodiment shown in FIG.

FIG. 9 shows a characteristic of a limit value (cutoff frequency) with respect to a normalized shake correction amount.

FIG. 10 is an example of a change in an effective image circle diameter and a maximum correction range (maximum shift limit) with respect to a change in focal length.

11 is a flowchart in which the determination of the limit value based on the normalized shake correction amount is introduced into the embodiment shown in FIG.

12 is a characteristic diagram of a limit value (cutoff frequency) with respect to a normalized shake correction amount used in S35 of FIG.

FIG. 13 is a schematic configuration block diagram of a third embodiment of the present invention.

FIG. 14 is a flowchart of an initialization routine of the image stabilization control module 254.

FIG. 15 is a flowchart of a routine for calculating a shake angle.

FIG. 16 is a flowchart of a process for determining a cutout range from angular displacement.

[Explanation of symbols]

 10: Photographing lens 12: CCD image sensor 14: Amplifier 16: Camera signal processing circuit 18a: Angular velocity sensor in pitch direction 18b: Angular velocity sensor in yaw direction 20a, 20b: Amplifier 22: Anti-vibration control circuit 24: Anti-vibration ON / OFF switch 26: CCD drive circuit 28: Line memory 30: Memory control circuit 32: All imaging area of image sensor 12 34: Cutout range 110: Photographing lens 112: Fixed lens 114: Zoom lens 116: Aperture 118: Anti-vibration Shift lens 120: focus lens 122: imaging device 124: amplifier 126: camera signal processing circuit 128: motor drive circuit 130: stepping motor 132: motor drive circuit 134: stepping motor 136: encoder 138: amplifier 140: subtractor 142: Mo Drive circuit 144: stepping motor 146: system control circuit 148: zoom key 150a: angular velocity sensor in pitch direction 150b: angular velocity sensor in yaw direction 152a, 152b: amplifier 154: anti-vibration on / off switch 210: lens unit 212: fixed Lens 214: Zoom lens 216: Aperture 218: Fixed lens 220: Focus lens 222: Motor driving circuit 224: Stepping motor 226: Motor driving circuit 228: Stepping motor 230: Camera control circuit 232: Zoom switch 240: Camera body 242 : CCD image sensor 244: amplifier 246: camera signal processing circuit 248 a: angular velocity sensor in pitch direction 248 b: angular velocity sensor in yaw direction 250 a, 250 b: amplifier 252: stage Control circuit 254: image stabilization control module 256: image stabilization ON / OFF switch 258: memory, such as EEPROM 260: CCD drive circuit 262: a line memory 264: memory control circuit

Claims (10)

[Claims] A variable-magnification photographing optical system, imaging means for converting an optical image by the magnification-magnification photographing optical system into an electric signal, vibration detection means for detecting vibration applied to the imaging means, and vibration detection means An image pickup apparatus comprising: a shake correction unit configured to correct a detected shake; and a limit unit configured to limit a correction operation of the shake correction unit with a limit value of a predetermined characteristic corresponding to a shake correction amount of the shake correction unit. apparatus. 2. The imaging apparatus according to claim 1, wherein the limiting unit changes the predetermined characteristic according to a focal length of the zoom optical system. 3. The limiting means includes: a normalizing means for normalizing a shake correction amount of the shake correcting means; and a predetermined limit value characteristic applied to the shake correction amount standardized by the normalizing means. The imaging apparatus according to claim 1, further comprising: a limit value calculating unit configured to calculate a limit value; and a shake limiting unit configured to limit a correction operation of the shake correcting unit based on the limit value calculated by the limit value calculating unit. 4. The imaging apparatus according to claim 3, wherein the normalizing unit normalizes a shake correction amount of the shake correcting unit based on a focal length and a maximum shake correction range of the shake correcting unit. 5. The imaging apparatus according to claim 1, wherein the shake correction unit includes an optical element that moves an optical axis of the zoom optical system. 6. The imaging apparatus according to claim 1, wherein the limiting unit includes a band limiting unit that limits a band of the shake signal detected by the shake detecting unit. 7. The imaging apparatus according to claim 1, wherein the shake correction unit is an electronic extraction unit that electronically extracts a part of the entire imaging screen of the imaging unit. 8. A focal length of the zoom optical system,
The imaging apparatus according to claim 7, further comprising a storage unit configured to store a surplus position change amount and a pixel size of the extracted image in the entire imaging screen, and an output video format. 9. The imaging apparatus according to claim 1, wherein the detection frequency of the shake detection means is set to an integral multiple of the least common multiple of the field frequency according to an output video format. 10. The method according to claim 1, wherein the limit value of the predetermined characteristic is determined in proportion to the n-th power of the shake correction amount (where n is an integer of 1 or more). Imaging device.