JPH0686142A - Image pickup device - Google Patents

Abstract

PURPOSE:To device a lens drive direction accurately by deciding restarting of automatic focus adjustment from a decrease in a focus point and a change in a current focus voltage base on a signal in response to a focal state. CONSTITUTION:This image pickup device is provided with a 1st fixed lens group 101, a 2nd magnification lens group (zoom lens) 102, an iris 103, and a 3rd fixed lens group 104. The automatic focus is adjusted by moving a focus lens 105 so as to maximize the output signal level of a band pass filter 117. In this case, when the output signal level of the band pass filter 117 is decreased from a prescribed level over a prescribed time after focusing, it is judged that an object is moved and the focus lens 105 is moved again. The focus lens 105 is moved (wobbling) in the forward backward directions in his restarting and a change in the output signal level of the band pass filter 117 is observed to drive the lens in a direction at which the focal voltage is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device, and in particular,
The present invention relates to a device for automatically adjusting focus by grasping a focus state of an optical system on a captured image from a state of a video signal obtained via an image sensor.

[0002]

2. Description of the Related Art In recent years, video equipment such as a video camera has made remarkable progress, and auto focus control, auto iris control, zoom function, etc. are standardly equipped.
Improvements in operability and multiple functions are being pursued in all parts.

By the way, when looking at a conventional autofocus device, the sharpness of the screen is detected from the video signal obtained by photoelectrically converting the subject image by an image pickup device or the like, and the focus lens is used to maximize the sharpness. Control the position of
The method of adjusting the focus is becoming mainstream.

In order to evaluate the sharpness of the screen, generally, the level (focus voltage) of the high frequency component of each video signal extracted by a plurality of bandpass filters (BPF) having different band limits. Etc. are used. This takes advantage of the fact that when a normal subject image is taken, the level of the high-frequency component (focus voltage) increases as the focus comes in, and the point at which the level becomes maximum is the in-focus position. .

Therefore, when the focus voltage is low, the focus lens is driven at a high speed in the direction in which the focus voltage becomes high, the speed is reduced as the focus voltage becomes higher, and the focus lens is accurately stopped at the point where the focus voltage is high. As described above, control is performed by using the level of the focus voltage and the size of the differential amount. Such a method is generally called a hill-climbing autofocus method.

Next, when the focus voltage drops below a predetermined value for a certain period of time after focusing, it is determined that the subject has changed, and the focus lens is moved again.
This is called a restart. In restarting, the lens is swung back and forth (wobbling), and the change in the focus voltage at that time is observed, and the lens is driven as the focus voltage increases.

[0007]

However, in the case of the above-mentioned conventional example, the following problems occur when the system is restarted. That is, when the camera is panned from the in-focus state, the focus voltage changes as shown in FIG. 3, the focus voltage becomes low during the panning, and becomes high during the stop. Therefore, since the focus voltage changes due to factors other than the movement of the lens during panning, if the lens is restarted and wobbling during panning, the lens drive direction determination may be erroneous.

In view of the above problems, it is an object of the present invention to make it possible to accurately determine the lens driving direction.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a focus adjusting means for performing focus adjustment based on a signal corresponding to a focus state detected from an image pickup signal, and a focus adjusting means based on the signal corresponding to the focus state. It is provided with a calculation means for determining the restart of the automatic focus from the amount of decrease of the state from the in-focus point and the amount of change of the current focus voltage.

Another feature of the present invention is that
Focus adjustment means for performing focus adjustment based on a signal corresponding to the focus state detected from the image pickup signal obtained through the image pickup device, and based on the signal according to the focus state, The focus state is adjusted regardless of the current change amount of the focus voltage based on the calculation means for determining the restart of the automatic focus from the decrease amount and the current change amount of the focus voltage and the signal according to the focus state. And a calculation means for determining restart of the automatic focus after a certain time has passed since the focus was lowered.

Another feature of the present invention is that a focus adjusting means for performing focus adjustment based on a signal corresponding to a focus state detected from an image pickup signal obtained through an image pickup device, and the focus adjustment means. The calculation means reverses the vibration direction of the lens, which determines the adjustment direction, every time.

[0012]

[Function] Based on the signal according to the focus state, the restart of the automatic focus adjustment is determined from the decrease amount from the in-focus point and the change amount of the current focus voltage to restart the wobbling during the panning. This prevents the occurrence of an error in the determination of the lens driving direction. Further, preferably, even if the amount of change in the focus voltage does not become small, the restart is performed after a lapse of a certain period of time, thereby preventing the problem that the restart is not performed forever. Further, preferably,
If the driving direction of the lens is not known after the web ring, by performing the web ring in the opposite direction to the previous web ring, the change in the focus voltage due to the web ring is canceled and the lens drive direction is changed. Avoid the inconvenience of being unable to make decisions.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the image pickup apparatus of the present invention will be described below with reference to FIGS. In FIG. 1, 1
Reference numeral 01 is a fixed first lens group, 102 is a second lens group (zoom lens) for zooming, 103 is a diaphragm, 104 is a fixed third lens group, and 105 is a movement of a focus image due to zooming. It is a fourth lens group (focus lens or compensator lens) having both a correcting function and a focusing function.

Reference numeral 106 is an image pickup surface of the image pickup element.
Next, 107, 108, and 109 are the zoom lens 10.
2, an actuator for moving the diaphragm 103 and the focus lens 105, respectively. And 11
Reference numerals 0, 111, and 112 denote drivers, and the actuators 107, 108, and 10 based on a signal given from a system control circuit 119 that controls the entire system.
It is for driving 9.

Reference numerals 113, 114 and 115 denote position encoders for detecting the mechanical positions of the zoom lens 102, diaphragm 103 and focus lens 105 and converting them into electric signals. Reference numeral 113 denotes a zoom encoder. Reference numeral 114 is an iris encoder, and 115 is a focus encoder. Further, 116 is an amplifier that amplifies the output of the image sensor 106 to a predetermined level, and 117 is a bandpass filter that extracts a wide range component used for focus detection from the output signal of the image sensor 116.

Reference numeral 118 is an adjuster for controlling the state of the diaphragm using the output signal level of the image pickup element 116.
A system control circuit 9 controls the actuators 107 and 109 based on the output signals of the zoom encoder 113, the iris encoder 114, the focus encoder 115, and the bandpass filter 117, while controlling the entire system. It is composed of a computer (microcomputer).

In the camera system configured as shown in FIG. 1, generally, automatic focus adjustment (AF) is performed by moving the focus lens 105 so that the output signal level of the bandpass filter 117 becomes maximum. .

Next, the bandpass filter 117 after focusing is performed.
When the output signal level of 1 is lower than a predetermined value for a certain period of time, it is determined that the subject has changed, and the focus lens 105 is moved again. This is called restart. In this restart, the focus lens 105
Wobbling back and forth (wobbling) and observing the change in the output signal level of the bandpass filter 117 at that time, the lens is driven as the focus voltage increases.

FIG. 3 is a characteristic diagram showing the output signal level of the bandpass filter 117 when the camera is panned from the in-focus state. That is, the signal level is low during panning and high during stop. For this reason, if the device is restarted and wobbled during panning, the signal level changes due to factors other than the movement of the lens, and the lens drive direction determination may be erroneous.

In this embodiment, in order to prevent such inconvenience, the following is done. That is, FIG.
As shown in FIG.
It is determined whether or not the output signal level (focus voltage) of No. 7 falls below a predetermined value for a certain period of time.

If it has not decreased, the process waits at step P1, while if it has decreased, the process proceeds to step P2 to decide to restart. At this time, in the present embodiment, in order to avoid restarting during panning, after determining restarting, the process proceeds to step P3, where the amount of change in the output signal level (focus voltage) of the bandpass filter 117 is a predetermined amount. It is determined whether or not the value is lower than the value.

In this case, if it has not decreased, the system waits for restarting and wobbling until the amount of change in the output signal level (focus voltage) of the bandpass filter 117 becomes small. When the amount of change becomes small, step P4
Go to and restart here to wobble. That is, the wobbling is performed after the amount of change in the focus voltage becomes small and becomes stable.

In the present embodiment, since wobbling is performed in this manner, restarting and wobbling during panning causes the signal level to change due to factors other than lens movement, causing the lens drive direction to change. There is no erroneous judgment of.

Next, a second embodiment of the image pickup apparatus of the present invention will be described with reference to FIGS. If the restart is not performed when the amount of change in the focus voltage is large as in the first embodiment, as shown in FIG. 5, if the camera shake occurs after the panning, the restart is not performed forever. Therefore, there is an inconvenience that the image remains blurred.

In the present embodiment, in order to prevent such an inconvenience, wobbling is performed by restarting after a lapse of a certain time even if the focus voltage vibrates and the amount of change does not become small. Is.

That is, as shown in the flow chart of FIG. 6, in the image pickup apparatus of this embodiment, first, in step P1, the output signal level (focus voltage) of the bandpass filter 117 falls below a predetermined value for a certain period of time. It is determined whether or not it has been done, and if it has fallen, it proceeds to step P2 and decides to restart.

Next, in step P3, the bandpass filter 1 is used to avoid restarting during panning.
Until the output signal level of 17 (focus voltage) becomes small,
Wait for the reboot and wobbling. Then, when the amount of change in the focus voltage becomes lower than a predetermined value, step P
Proceed to step 5, restart and perform wobbling.

If, as a result of the determination in step P3, the amount of change in the focus voltage does not become smaller than the predetermined value due to camera shake after panning, the process proceeds to step P4, and it is determined whether or not a fixed time has elapsed after the restart decision. Make a decision. When the fixed time has not elapsed, the process returns to step P3. If the time has passed, the process proceeds to step P5 to restart and perform wobbling.

In the case of this embodiment, since wobbling is performed by restarting as described above, even if the focus voltage oscillates due to camera shake or the like and the amount of change does not become small after the end of panning, a constant time is maintained. Reboot after is passed. Therefore, it is possible to reliably prevent the inconvenience that the image remains blurred by not restarting the image forever.

Next, a third embodiment of the image pickup apparatus of the present invention will be described with reference to FIGS. In the hill climbing autofocus method described above, when first determining the driving direction of the lens, swing the lens back and forth as shown in FIG.
The lens is driven in the direction in which the focus voltage increases by observing the change in the focus voltage at that time.

That is, in FIG. 7, (a) is the start of wobbling, and in (b), the lens is moved to the close side to capture the focus voltage. Then, in (c), the lens is moved to the infinity side to capture the focus voltage, and in (d), the lens is returned to the original state. Then, the hill climbing direction is determined based on the magnitudes of the respective focus voltages captured in (b) and (c).

However, if the hill climbing direction is determined in this way, the following inconvenience may occur. That is, when the subject moves away from the camera as indicated by the arrow in FIG. 8 by the same amount as the change in the focal length due to the movement of the lens during the movement of the lens from FIG. 7B to FIG. Since the blurring of the subject does not change between (b) and (c), there arises a disadvantage that the difference in focal voltage does not appear and the voltage for discriminating the direction is not used.

In the case of the third embodiment, it is made to solve such inconvenience, and even if the subject moves so as to cancel the change of the focus voltage due to the wobbling,
The direction is surely discriminated.

The operation of the image pickup apparatus of the third embodiment will be described below with reference to the flowchart of FIG. First, in step P1, the lens is moved to the infinite side, and in step P2, the focus voltage is captured. Next, in step P3, the lens is moved to the close side, and in step P4, the focus voltage is captured. Then
In step P5, while moving the lens to the initial position,
The directions are determined by comparing the focus voltages captured in steps P2 and P4. The movement state of the above-mentioned lens is shown in FIG.

Next, in step P6, it is determined whether or not the direction has been determined. If so, the process proceeds to step P7 to drive the lens. If the direction has not been determined, the process proceeds to step P8, and the wobbling opposite to the previously performed wobbling is performed again.
That is, in step P8, wobbling for moving the lens to the closest side is performed. Then, in step P9, the focus voltage is fetched.

Then, in step P10, the lens is moved to the infinite side, and in step P11, the focus voltage is captured. In step P12, the lens is returned to the initial position and the direction is determined. Then, in step P13, it is determined whether or not the direction is determined. If the direction is determined, the process proceeds to step P7 to drive the lens. If the direction is not determined as a result of the determination in step P13, it remains as it is.

As described above, in the third embodiment, first, wobbling is performed from the closest distance to the infinite direction. Next, on the contrary, since the wobbling is performed from the infinity side to the near side, it is possible to eliminate the inconvenience that the change of the focus voltage due to the wobbling is canceled by the movement of the subject. Therefore, the driving direction of the lens can be reliably determined.

[0038]

As described above, according to the first aspect of the present invention, after the restart is determined, the wobbling is waited until the change amount of the focus voltage becomes small, thereby determining the driving direction of the lens. It is possible to obtain a quick focus even on a subject after panning.

According to the second aspect of the present invention, even if the amount of change in the focus voltage does not become small due to the vibration of the focus voltage due to camera shake or the like even after the end of the panning, the restart is performed after a certain period of time. By not restarting forever, it is possible to reliably prevent the inconvenience that the image remains blurred.

According to the third aspect of the present invention, if the direction cannot be determined after the wobbling, the wobbling is performed again in the opposite direction to the wobbling previously performed, thereby canceling the change in the focus voltage due to the wobbling. The inconvenience that the lens driving direction cannot be determined can be eliminated. Therefore, it is possible to surely prevent the image from being unfocused and unfocused even though the image is out of focus and the automatic focus adjustment should be performed.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a relationship between a focus voltage and a lens position.

FIG. 3 is a diagram showing a change in focus voltage during panning.

FIG. 4 is a flowchart illustrating an operation of the image pickup apparatus according to the first embodiment.

FIG. 5 is a diagram for explaining that the focus voltage changes due to camera shake.

FIG. 6 is a flowchart for explaining the operation of the image pickup apparatus according to the second embodiment.

FIG. 7 is a diagram for explaining a procedure for performing wobbling.

FIG. 8 is a diagram showing how a subject moves so as to cancel a change in focus voltage due to wobbling.

9 is a diagram for explaining a procedure for performing wobbling from a direction different from the direction shown in FIG.

FIG. 10 is a flowchart illustrating the operation of the image pickup apparatus according to the third embodiment.

[Explanation of symbols]

 101 Fixed First Lens Group 102 Zoom Lens 103 Aperture 104 Fixed Third Lens Group 105 Focus Lens 106 Imaging Surface of Image Sensor 107 Zoom Lens Actuator 108 Aperture Actuator 109 Focus Lens Actuator 110 Driver 111 Driver 112 Driver 113 Zoom Encoder 114 Iris Encoder 115 Focus Encoder 116 Amplifier 117 Bandpass Filter 118 Iris Adjuster 119 System Control Circuit

Claims (3)

[Claims] 1. A focus adjustment means for performing focus adjustment based on a signal corresponding to a focus state detected from an image pickup signal obtained through an image pickup device, and a focus state based on the signal according to the focus state. And an arithmetic unit that determines restarting of the automatic focus from the amount of decrease from the in-focus point and the change amount of the current focus voltage. 2. A focus adjustment means for performing focus adjustment based on a signal corresponding to a focus state detected from an image pickup signal obtained through an image pickup device, and a focus state based on the signal corresponding to the focus state. Based on the signal according to the above-mentioned focus state, and the calculation means that determines the restart of the automatic focus from the amount of decrease from the in-focus point and the change amount of the current focus voltage, regardless of the current change amount of the focus voltage. An imaging device, comprising: an arithmetic unit that determines restarting of the automatic focus after a fixed time has elapsed after the focus state is lowered from the in-focus state. 3. Focus adjustment means for performing focus adjustment based on a signal corresponding to a focus state detected from an image pickup signal obtained through an image pickup element, and vibration of a lens for determining a direction of the focus adjustment. An imaging device, comprising: an arithmetic unit that reverses the direction every time.