JPH04306080A - Image pickup device - Google Patents

Abstract

PURPOSE:To prevent occurrence of unsharp locking by detecting a displacement of an iris mechanism and a movement and its direction of a main body and applying arithmetic processing to a focus evaluation value in response to the detected moving vector and iris. CONSTITUTION:A motion vector detection means 11 extracts a motion vector 12 based on a Y signal 5 to detect the movement and direction of a main body. Moreover, an iris 16 detected by an iris detection circuit 15 is fed to an arithmetic control means 13 together with the motion vector 12, in which they are always monitored. In this case, the vector 12 indicates the presence of a hand blur and the iris 16 is information representing the degree of the depth of the focus. When the iris 16 is smaller than a predetermined value, a moving means of focus evaluation values 8 for three fields is calculated, and when the iris 16 is larger than a predetermined value, a moving means of focus evaluation values 8 for five fields is calculated and the result is respectively outputted to a focus control means 9. Then the fluctuation in the evaluation value 8 does not give effect on input information of the control means 9 thereby preventing production of unsharp locking.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus such as a video camera that automatically adjusts the focus based on a captured video signal obtained from an imaging device.

0002

2. Description of the Related Art FIG. 3 is a diagram showing an example of a conventional imaging device. In the figure, a focus lens 1 forms an image of a subject (not shown) onto an image pickup device 2 such as a CCD. The output of the image sensor 2 is connected to a video signal processing circuit 3, and one of the outputs is connected to a monitor TV 4, making it possible to capture the subject as a visible image. Reference numeral 6 denotes a high-pass filter (hereinafter referred to as HPF), to which the luminance signal (hereinafter referred to as Y signal) 5, which is the other output of the video signal processing circuit 3, is connected;
The output of the F6 is connected to an integration circuit 7, and the HPF 6 and integration circuit 7 constitute a focus evaluation value detection means 18, which outputs a focus evaluation value 8.

Reference numeral 9 denotes focus control means, into which the focus evaluation value 8 is input, and the output of the focus control means 9 is a signal created based on the focus evaluation value 8, which is connected to a focus motor 10. The focus lens 1 is driven according to the focus evaluation value 8.

Next, the operation of the conventional imaging apparatus configured as described above will be explained with reference to FIGS. 4 and 5. In FIG. 3, a subject image (not shown) is formed on an image sensor 2 by a focus lens, photoelectrically converted, and input to a video signal processing circuit 3. A visible image is obtained by being applied to the monitor TV 4 as a composite video signal (not shown).

Next, in order to automatically focus the subject image on the image pickup device 2 and obtain a clear image on the monitor TV 4, the following procedure is required. First, the Y signal 5 is taken out from the video signal processing circuit 3, the high frequency component of this Y signal 5 is extracted by the HPF 6, and the integration circuit 7 integrates it for each horizontal scanning period, and then integrates it over one field. A focus evaluation value 8, which is a signal indicating the sharpness of the image, can be obtained. That is, the above procedure becomes a focus evaluation value detection procedure.

[0006] Next, when the focus evaluation value 8 is inputted to the focus control means 9, the focus control means 9
A focus motor 10 that constantly monitors the focus evaluation value 8 and drives the focus lens 1 so as to lead it to a peak.
control. In this way, a so-called mountain climbing autofocus (AF) closed loop is configured to realize stable focusing operation.

[0007]More detailed description of the mountain climbing AF will be given here.As mentioned above, it utilizes the fact that the amount of high frequency components of the Y signal 5 of the video image corresponds to the degree of focus. In other words, each subject has its own unique spatial frequency component, but since the focus lens 1 acts as a low-pass filter for this, the actual captured video signal is generated when the focus lens 1 is in focus. However, the further the focus lens 1 deviates from this point, the more the image corresponds to passing through a low-pass filter with a low cutoff frequency, resulting in a blurred image lacking high-frequency components. Therefore, as shown in FIG. 5, the amount of high frequency components of the video signal is
That is, the focus evaluation value 8 forms a mountain with the top at the in-focus point on the distance axis of the focus lens. This is mountain climbing AF
It is called.

In this mountain-climbing AF, as shown in FIG. 4, focus control is performed through a five-step procedure indicated by (101) to (105). That is, (101)
Activation: First, the focus lens 1 is activated in an arbitrary direction and the focus evaluation value 8 is measured. (102) Mountain climbing: If the starting direction increases the focus evaluation value 8, continue to drive the lens 1 in that direction, and if the opposite, drive the lens 1 in the opposite direction. (103) Top detection: It is detected that the position of the focus lens 1 has passed the in-focus point, that is, the top of the focus evaluation value 8, as the focus evaluation value 8 changes from an increasing direction to a decreasing direction, and this is stored. (104) Stop: Return the focus lens 1 to the in-focus position stored in (103) and stop. (105) Standby: The state of the focus evaluation value 8 is monitored, and when a change occurs, the focus control is performed stably using an algorithm that returns to the activation of (101) as necessary.

[0009]

[Problems to be Solved by the Invention] In the conventional imaging device configured as described above, the focus evaluation value 8 varies from field to field due to camera shake, etc. when performing hand-held imaging, especially when imaging at the telephoto end during zooming. Despite the fact that
Since focusing control is continued based on the algorithm described above, there is a problem in that the focusing operation takes a long time to complete.

[0010] Furthermore, in order to avoid the above-mentioned problems, it has been known that a moving average over several fields of the focus evaluation value 8 is adopted as the true focus evaluation value, and this is used to climb a mountain. , for example, focus lens 1
In the case of a subject for which the focus evaluation value 8 changes sharply with respect to the position of Since the difference between the positions becomes relatively large, there is a problem that the focusing operation ends with the image still blurred.

The present invention has been made in view of the above-mentioned circumstances, and is capable of preventing the occurrence of so-called bokeh lock, in which the focusing time is prolonged due to camera shake during hand-held shooting, or the focusing operation ends with a blurred image. The purpose is to provide an imaging device that can.

0012

[Means for Solving the Problems] An imaging device according to the present invention detects a detected focus evaluation value by an evaluation value detection means that detects a high frequency component level of an imaged video signal obtained from an image sensor as a focus evaluation value at fixed time intervals. A motion vector that can detect the movement and direction of the device body in an imaging device that has a focus control means that monitors changes, moves the focus lens in an increasing direction, and fixes it at the position where the maximum evaluation value is obtained. The present invention is characterized in that the calculation control of the focus evaluation value is performed in accordance with the motion vector detected by the detection means and the aperture value detected by the aperture value detection means that detects the amount of displacement of the aperture mechanism.

[0013]

[Operation] According to the present invention having the above structure, the state of the motion vector for detecting the movement and direction of the device and the aperture value of the aperture mechanism are constantly monitored, and when the motion vector is within a preset range, camera shake is detected. The moving average of the number of fields is determined according to the aperture value, that is, the depth of focus. This value is again adopted as the focus evaluation value. Also,
If the motion vector is less than the preset range, it is determined that there is no camera shake, and the moving average of the focus evaluation values is not taken. Furthermore, when the motion vector exceeds a preset range, it is determined that the panning or tilting state is present.
Prohibits focusing operation.

[0014] Based on the focus evaluation value determined as above,
By allowing the camera to climb mountains or prohibiting focusing operations, efficient, accurate, and quick automatic focusing can be performed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of an imaging device according to an embodiment of the present invention. In the diagram, the same components as in the conventional example shown in FIG. Omitted.

In FIG. 1, reference numeral 11 denotes motion vector detection means, to which the Y signal 5 is input, and the motion vector 1 is output.
2 is obtained, and this is input to the calculation control means 13. 1
Reference numeral 5 denotes an aperture value detection circuit which uses a Hall element to detect the amount of displacement of the aperture mechanism 14 as an aperture value 16, and a known method can be used. The aperture value 16 corresponds to what is known as the so-called F number, and like the motion vector 12, it is connected to the arithmetic control means 13, and when the value is large, the aperture mechanism 14 is closed. state, and when it is small it is open.

The output of the calculation control means 13 is a focus evaluation value calculated according to the motion vector 12 and the aperture value 16, and is input to the focus control means 9. Incidentally, this value does not necessarily match the focus evaluation value 8. Further, a focusing operation prohibition signal 17 is also input to the focus control means 9. Furthermore, the output of the focus control means 9 is connected to a focus motor 10.

Next, the operation of the embodiment configured as described above will be explained. However, descriptions of parts that overlap with the conventional technology will be omitted. In FIG. 1, a motion vector detection means 11 extracts a motion vector 12 based on the Y signal 5. In FIG. Although a detailed explanation of the method for determining the motion vector 12 will be omitted, it is possible to use a known method such as a representative point matching method using a field memory, for example. The motion vector 12 obtained by such a method is applied to the calculation control means 13.

On the other hand, the aperture value 16 detected by the known aperture value detection circuit 15 is also added to the arithmetic control means 13, and in this arithmetic control means 13, the motion vector 12, which is information on the presence or absence of camera shake, and the focus The aperture value 16, which is information about the degree of depth, is constantly monitored.

Now, if the motion vector 12 is smaller than a predetermined value, the arithmetic control means 13 calculates
The input focus evaluation value 8 is output as is to the focus control means 9. Further, assume that the motion vector 12 is larger than a predetermined value and is not large enough to determine that panning or tilting is occurring. Here, if the aperture value 16 is less than a predetermined value, that is, if the depth of focus is relatively shallow, a moving average of three fields of the focus evaluation value 8 is taken, and the value is output to the focus control means 9. In addition, if the aperture value 16 is larger than a predetermined value, that is, if the depth of focus is relatively deep,
A moving average for the field is taken and the value is output to the focus control means 9.

The reason why the number of fields of the moving average of the possible focus evaluation values 8 is made variable depending on the aperture value 16 will be described below. In other words, when a moving average is taken for the focus evaluation value 8, it has the advantage that fluctuations in the evaluation value due to camera shake are suppressed and the problem of so-called blur lock caused by false mountains can be avoided. The position may be slightly off from the actual position. This problem may cause visual problems, especially when the aperture value 16 is large, that is, when focusing is performed with a shallow depth of focus. In order to avoid such problems, the number of fields on which moving average is performed is reduced compared to when the depth of focus is deep. Note that when the depth of focus is deep, this kind of problem practically does not occur, and instead, the number of fields for which the moving average is taken is increased to minimize the fluctuation of the focus evaluation value 8 due to camera shake. making an effort. Incidentally, the determined value of the aperture value 16 in this embodiment corresponds to the so-called F number of about 5.6, but it goes without saying that it is not limited to this value. Also, regarding the case classification,
In this embodiment, there are two, but the number is not particularly limited to this.

Furthermore, when the motion vector 12 becomes large enough to determine that the camera is in a panning or tilting state, a focusing operation prohibition signal 17 is output to the focus control means 9.

The focus control means 9 controls the drive of the focus motor 10 in accordance with the input information from the arithmetic control means 13, usually in accordance with the principle of mountain climbing servo, so as to maximize the input information, that is, the focus evaluation value. do. Further, when the focusing operation prohibition signal 17 is received, the focusing operation is not performed until the prohibition is canceled, that is, the motion vector 12 falls within a certain value.

By the above-described operation, precise and quick focusing can be achieved in all situations. Here, the output to the focus control means 9 is changed to the motion vector 12
Although the cases are divided into three depending on the value of , when the absolute value of the motion vector 12 is x (the number of horizontal scanning lines), it has been experimentally found that the following values are desirable.・No camera shake: vertical direction x≦2H…Output without taking the moving average of focus evaluation value 8 ・With camera shake: vertical direction 2H<x≦40H…taking the moving average of focus evaluation value 8 for 3 to 5 fields Output from
Chilled: Vertical direction x > 40H…Outputs focus operation prohibition signal 17

Note that although the horizontal value is omitted, it can be considered that the width is such that it forms a square on the screen together with the vertical value. However, the above values are only a guideline and are not limited to these.

FIG. 2 is a block diagram of an imaging apparatus according to another embodiment of the present invention. In the figure, reference numeral 19 denotes an angular velocity sensor, which is attached to the main body of the imaging apparatus and detects shaking of the main body of the apparatus. This angular velocity sensor 19 is connected to the motion vector detection means 11.
generates a motion vector 12 by processing the information obtained from the angular velocity sensor 19, and inputs it to the arithmetic control means 13. Since the other configurations are the same as those of the embodiment shown in FIG. 1, the same reference numerals are given to the corresponding parts and the explanation thereof will be omitted.

Next, the operation of FIG. 2 will be explained. The motion of the imaging device is detected by the angular velocity sensor 19, and its output is input to the motion vector detection means 11. The motion vector detection means 11 performs processing such as amplification and shaping on the signal corresponding to the motion of the imaging device obtained by the angular velocity sensor 19, and then inputs the signal as a motion vector 12 to the arithmetic control means 13. The following explanation will be omitted since it is the same as the above embodiment, but in any case, efficient focusing operation is possible, and precise and quick focusing can be achieved in all situations.

[0028]

[Effects of the Invention] As described above, according to the present invention, even if camera shake occurs during a focusing operation, the influence of the fluctuation of the focus evaluation value due to it is not included in the input information to the focus control means. It doesn't appear. Therefore, it is possible to perform a focusing operation toward the true mountain without being confused by the false mountain. In addition, when panning or tilting, focusing operations can be prohibited to eliminate unnecessary movement of the focus lens, making accurate and quick automatic focusing possible and providing extremely comfortable operability. This has the effect of providing an imaging device.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the invention.

FIG. 3 is a diagram showing the configuration of an example of a conventional imaging device.

FIG. 4 is a flowchart showing the procedure of mountain climbing autofocus.

FIG. 5 is an explanatory diagram of the operation of mountain climbing autofocus.

[Explanation of symbols]

1 Focus lens 2 Imaging device 8 Focus evaluation value 9 Focus control means 11 Motion vector detection means 12 Motion vector 13 Arithmetic control means 15 Aperture value detection circuit 18 Focus evaluation value detection means

Claims (1)

[Claims] 1. Focus evaluation value detection means for detecting the level of a high frequency component of a captured video signal obtained from an image sensor as a focus evaluation value at regular intervals; In an imaging device, a focus control means performs a focusing operation by moving a focus lens to a position where a maximum evaluation value is obtained, and a motion vector detection means for detecting movement and direction of the main body of the device, and an aperture mechanism. What is claimed is: 1. An imaging apparatus comprising: aperture value detection means for detecting a displacement of the aperture value; and arithmetic control means for performing arithmetic control of a focus evaluation value according to the detected motion vector and aperture value.