JP2006133592A - Automatic focusing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic focusing apparatus capable of accurately performing an automatic refocusing processing in accordance with the change in an object of focusing target, and is, capable of attaining both superiority of user's operability and power consumption. <P>SOLUTION: Regarding the automatic focusing apparatus where the need for automatic re-focusing processing is decided in accordance with a change in a prescribed object monitoring area, then the automatic re-focusing processing is performed, the object monitoring area in the case the lens drive is stopped in a focused state is changed from that when the lens drive is stopped in non-focused state state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an autofocus (automatic focus adjustment) apparatus that automatically focuses a subject on a video camera or the like.

In general, a video camera device includes an automatic focus adjustment device that drives a focus adjustment lens to automatically focus on a subject. The subject image is photoelectrically converted by an image sensor or the like, the sharpness of the screen is calculated from the obtained video signal, and the lens adjustment device is controlled to bring it into the in-focus state so as to maximize it.
As the sharpness, in general, the intensity of a high-frequency component of a video signal extracted by a bandpass filter (BPF), an edge component of a video signal extracted by a differentiation circuit, or the like is used.

  When a normal subject image is captured, these signals have a low high-frequency component level and a large blur amount when the focus is blurred, and the high-frequency component level increases and the blur amount decreases as the focus is adjusted. The maximum and minimum values are taken in the state where the in-focus point is reached. Therefore, the focus adjustment lens is controlled so that it moves in the direction of increasing when the level of the sharpness signal is low and stops at the maximum of the sharpness signal.

  The control by the automatic focus adjustment device is typically a procedure shown in, for example, Japanese Patent Application Laid-Open No. 2-140074. The outline of the procedure of Patent Document 1 will be described with reference to FIGS. First, FIG. 3 and FIG. 4 which are subroutines will be described. FIG. 3 shows the movement of the focus adjustment lens toward the close side. First, the lens is driven to the closest side (S301). Here, it is determined whether or not the evaluation value has increased by a predetermined amount or more (S302), and if it is increased, the lens position is stored in a storage device such as a memory (S303). If the evaluation value has not increased by a predetermined amount (S302), it is determined whether the predetermined amount has decreased (S304). If it is lowered, it is determined whether the lens position is stored (S306). If it is stored, the two-dimensional area (detection frame) where the in-focus is detected is determined (S307), and it is determined that the peak position has been detected (S308). ). If the lens position is not stored (S306), the process returns from the subroutine without determining the peak position. If the evaluation value does not decrease by a predetermined amount in S304, it is determined whether the focus adjustment lens has reached the closest end (S305). If the close end has not been reached, the process returns to S301 and moves again to the close side. If the closest end is reached in S305, the process returns from the subroutine.

  FIG. 4 shows driving of the focusing lens toward the infinity side. The processing procedure is the same as that obtained by replacing “close” with “infinite” in steps S301 and S305 in FIG.

FIG. 2 will be described. In FIG. 2, first, the storage device for storing the lens position is cleared (S201). Next, the end arrival counter is cleared (S202). Then, the subroutine for the near side peak search shown in FIG. 3 is called (S203). If the peak is detected (S204), the focus adjustment lens is moved to the stored peak position (S205). If the peak cannot be detected (S204), it is determined whether the closest end has been reached (S206). If the closest end has not been reached, infinite peak search is performed in S208 in order to switch to infinite driving. If the closest end has been reached in the determination of S206, 1 is added to the end detection counter (S207). If a peak can be detected in S208 (S209), the focus adjustment lens is moved to the peak position (S205). If a peak has not been detected (S209), it is determined whether or not the peak has been reached (S210). If the end point has been reached, 1 is added to the end detection counter (S211). If it has not reached the infinite end (S210), it is determined whether the end counter is equal to or greater than the predetermined value (S212). If it is less than the predetermined value, the process returns to S203, and the near side peak search is performed again. If the predetermined value is exceeded in S212, it stops in an out-of-focus state (S213).
As a result of the above processing, for focus adjustment in the focused state (the state in which the focus adjustment lens is moved to the peak position) or in the out-of-focus state (the state in which the driving of the focus adjustment lens is stopped without detecting the peak) The lens can be stopped.

After the stop, the two-dimensional area is monitored as shown in FIG. Determine the need for re-autofocus. Here, FIG. 5 will be described. After performing the autofocus process (S501), the specification value (video state value) of the subject obtained from the area where the in-focus is determined is stored (S503). As the specification values, the contrast, brightness, sharpness, distance, etc. of the subject are appropriate. In addition, the specification value S1 of the subject is sequentially collected (S504), and compared with the value S0 stored in S503. If a certain difference has occurred (S505), the process returns to S501 and the autofocus process is performed again. If there is no difference, the process returns to S504 and the subject specification values are collected again.
Japanese Patent Laid-Open No. 2-140074

By the way, when focusing is stopped, it is preferable to perform autofocus in response to changes in the subject that is the focusing target. On the other hand, if you react sensitively to the surrounding subjects, the focus target subject has not changed, but an unnecessary focus adjustment lens drive has occurred in response to changes in the surroundings. This is a disadvantageous both in terms of appearance and power consumption.
The present invention has been made in view of the above-described problems in the conventional example. The re-autofocus processing can be accurately performed by changing the subject that is a focus target, and it is easy for the user to use and has superior power consumption. It is an object of the present invention to provide an autofocus device capable of achieving compatibility.

In order to solve the above-described problem, the present invention is characterized in that the subject monitoring area when the focus is stopped is different from the subject monitoring area when the focus is stopped.
That is, a first autofocus device according to the present invention includes a lens, an imaging unit that converts an image formed through the lens into an electrical signal, and a plurality of types of two-dimensional types including a part or all of the image. Sharpness calculation for calculating a sharpness value of the video based on a video signal corresponding to the two-dimensional area selected by the area selection means from the imaging means and the area selection means for selecting one or more of the areas Means, a video state calculation means for calculating a video state value of the video based on a video signal corresponding to a two-dimensional area selected by the area selection means from the imaging means, and the sharpness value is a maximum value. A lens driving means for driving the lens in the direction of the optical axis, and a drive control means for starting the driving of the lens when the image state value changes by a predetermined value or more. The stage is used for the image state calculation means, and when the lens driving means drives the lens, the position of the lens where the sharpness is maximized is specified and the driving is ended and the driving is ended without being specified. In this case, different two-dimensional regions are selected.

  According to a second autofocus device of the present invention, in the first autofocus device, the region selection unit may be used for the sharpness calculation unit, and the sharpness level when the lens driving unit drives the lens. Different two-dimensional regions are selected depending on whether the position of the lens where the maximum value of the lens is specified and the driving is ended or the driving is ended without being specified.

  A third autofocus device according to the present invention includes a lens, an imaging unit that converts an image formed through the lens into an electric signal, and a plurality of types of two-dimensional types including a part or all of the image. Sharpness calculation for calculating a sharpness value of the video based on a video signal corresponding to the two-dimensional area selected by the area selection means from the imaging means and the area selection means for selecting one or more of the areas Means for driving the lens in the optical axis direction so that the sharpness value becomes a maximum value, and drive control means for starting driving of the lens by the lens driving means, and the region selecting means Is different between when the lens driving means specifies the position of the lens where the sharpness becomes maximum when driving the lens and when the driving ends without being specified. And selects the two-dimensional region.

Here, the drive control means determines whether it is necessary to start driving the lens based on the sharpness value, for example. Alternatively, whether or not it is necessary to start driving of the lens based on the image state value output from the switch, which is provided with the image state calculation means as in the case of the autofocus start switch and the first and second autofocus devices. It may be a thing to determine.
The sharpness calculation means extracts a specific spatial frequency component from the video signal using, for example, a bandpass filter, and calculates a sharpness value based on the intensity of the spatial frequency component.

  The drive control means specifies the position of the lens when the lens driving means specifies the position of the lens at which the sharpness reaches a maximum when driving the lens and completes driving (focusing). The criterion for determining that the lens needs to be driven may be different depending on whether the driving is completed (out of focus). For example, in the case of out-of-focus, the determination criterion is set lower than that in the case of in-focus, and is set to a side where the necessity of driving the lens can be detected sensitively.

For example, the video state calculation unit calculates a video state value based on at least one of the luminance of the subject, the contrast of the subject, and the subject distance as an evaluation value for starting lens driving by the drive control unit.
The region selection means may select a wide two-dimensional region in the case of focusing and in the case of non-focusing.

In the conventional autofocus process described above, there was no difference between the subject monitoring area when the focus was stopped and the subject monitoring area when the focus was stopped. Even if autofocus processing is not performed again, the focus target subject does not move, but the focus adjustment lens is driven in response to sensitive changes in the surrounding subjects (background, foreground, etc.). Occurs, resulting in an inappropriate autofocus process, which is disadvantageous in terms of appearance and power consumption.
According to the present invention, the re-autofocus process can be accurately performed by changing the subject by changing the monitoring area when the focus is achieved and when the focus is stopped out of focus. As a result, it is possible to achieve both user-friendliness and superior power consumption.

The embodiments of the present invention are listed below.
[Embodiment 1]
A focusing lens;
Lens driving means for driving the focus adjustment lens in the optical axis direction;
Imaging means for converting a subject image formed through the focus adjustment lens into an electrical signal;
Image processing means for electrically processing a video signal of the imaging device;
Sharpness calculation means for calculating the sharpness value of the subject image from the video signal of the image processing means;
Video state calculation means for calculating the video state value of the subject image from the video signal of the image processing means;
Area selection means for selecting a two-dimensional area of the subject image to be input to the sharpness calculation means and the video state calculation means;
A bandpass filter for extracting a specific spatial frequency component from the video signal input to the region selection means;
The lens driving unit is controlled so that the subject sharpness calculated by the sharpness calculating unit is maximized, and the signal from the video state calculating unit is monitored after the subject sharpness has been maximized, and again. In a video camera apparatus comprising: system control means for determining whether it is necessary to control the lens driving means;
The region selection means is configured to determine whether the focus adjustment lens position where the subject sharpness is maximized can be specified (focused) or not (not focused) by the system control means. An autofocus device characterized by differentiating two-dimensional regions of a subject image inputted to a sharpness calculation means and a video state calculation means.

[Embodiment 2]
2. The autofocus device according to Embodiment 1, wherein a two-dimensional region input to the sharpness calculation device and the video state calculation device is made different according to whether the image is focused or not focused. .
[Embodiment 3]
In the autofocus device according to the second embodiment, two-dimensional regions input to the sharpness calculation device and the video state calculation device are made different according to in-focus / non-focus, and at the same time when in-focus An autofocus device characterized in that the two-dimensional area is wider than the two-dimensional area at the time of focusing.
[Embodiment 4]
The autofocus device according to the first embodiment, wherein the determination criterion for determining the necessity of driving the focus adjustment lens again is made different by the system control device at the time of out-of-focus as compared to at the time of focus. Focus device.

[Embodiment 5]
In the autofocus device according to the fourth embodiment, the system control device at the time of out-of-focus is different from that at the time of in-focus, and the determination criterion for determining the necessity of driving the focus adjustment lens is made different at the same time. An auto-focus device characterized in that the time criterion is set low and set to the sensitive side.
[Embodiment 6]
The video state calculation device according to any one of Embodiments 1 to 5 calculates an evaluation value for subject luminance, as an object.
[Embodiment 7]
6. A video camera device having an autofocus device, wherein the video state calculation device according to any one of the first to fifth embodiments calculates an evaluation value for subject contrast.

[Embodiment 8]
6. A video camera device having an autofocus device, wherein the video state calculation device according to any one of the first to fifth embodiments calculates an evaluation value for a subject distance.
In the above embodiment, the contrast, brightness, and sharpness of the subject can be used individually or simultaneously as the video state collected from the monitored area.
Further, it is possible to determine the re-autofocus process by using the amount of change in the video state that is different between the focused state and the out-of-focus state.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an embodiment of the present invention. In FIG. 1, 11 is a lens device including a focus adjustment lens, 12 is a diaphragm device, 13 is an imaging device that performs photoelectric conversion, 14 is an image processing device having CDS, AGC, and A / D functions, and 15 is a specific device. A band-pass filter (BPF) device that detects frequency components, 16 is a region selection device that selects a two-dimensional region on the screen, and 17 is a sharpness calculator that performs a sharpness calculation from the BPF device 15 signal in the region selected by the region selection device 16. Degree arithmetic unit 18 calculates a specific video state amount from the BPF device 15 signal in the area selected by the area selection unit 16. Video state arithmetic unit 19 controls the timing of the imaging device 13 and the image processing unit 14. Drive circuit device 20, aperture control device 20 for controlling the aperture device 12, 21 lens drive device for controlling the focus adjustment lens, 22 Control the device, calculating, performing result holding such a system controller.

The autofocus device shown in FIG. 1 can perform autofocus processing in accordance with the procedure shown in FIGS. 2, 3, 4, and 5. However, in this embodiment, the process of FIG. 6 is applied instead of the process procedure of FIG. FIG. 6 will be described.
FIG. 6 is obtained by replacing the area monitoring process (S502) shown in FIG. 5 with S602 to S604. That is, the autofocus process is performed in S601, and it is determined whether the focus is stopped or not focused (S602). If the focus is stopped, the area selected at the time of focusing is set as the subsequent monitoring area (S603). In the case of the out-of-focus stop, all the monitoring possible areas are set as subsequent monitoring areas (S604).

For example, referring to FIG. 7, when a subject exists as shown in the A frame of FIG. 7 and the subject is focused, the subsequent monitoring is set to the A frame. If the frame A is not reached or the focus is not reached, the frame B is set as a monitoring area.
FIG. 8 shows another example of the area. In FIG. 8, there are three frames A, B, and C, and any of them can be determined as being in focus. For example, a subject exists so as to cover the A frame, and the focus determination is performed using the A frame. When the focus is reached, the subsequent monitoring is performed using the subject information obtained from the A frame. The same applies to the B frame and the C frame. On the other hand, if there is no subject that can be brought into focus in any of the A, B, and C frames, and the subject is out of focus, all of the A, B, and C frames are set as monitoring areas.

  Furthermore, FIG. 9 is given as an example of another region. In the example of FIG. 9, there are nine areas where focus can be determined, and all of the A, B,. Here, for example, a subject exists so as to cover the E frame, and when the focus determination is performed using the E frame and the focus is reached, the subsequent monitoring area is set as the E frame. When there is no subject to be brought into focus in any of the A, B,..., I frames, and when the subject is out of focus, all of the A, B,.

  Furthermore, FIG. 10 is given as an example of another region. In the example of FIG. 10, there are five areas where focus can be determined, and all of the A, B,. Here, for example, a subject exists so as to cover the B frame, and the focus determination is performed using the B frame. When the focus is reached, the subsequent monitoring area is set as the B frame. When there is no subject that can be brought into focus in any of the A, B,..., E frames, and all the A, B,.

  Referring to FIG. 6, after an area is determined, subject information (S0), which is a video state value (specific value) of the area, is stored in a memory device (not shown) (S605). Subsequently, subject information (S1) of the area is acquired (S606), and it is determined whether a difference of a predetermined amount or more has occurred between S0 and S1 (S607). If no difference has occurred, it is determined that the subject has not changed, and subject information is acquired again (S606). If a difference has occurred (S607), the process returns to S601, and autofocus processing is performed again.

The actual acquisition timing of subject information in S606 is performed at the timing of V synchronization in the television standard. However, it may be performed with timer synchronization of about 10 ms to 100 ms. The predetermined amount calculated in S607 can be set to a different value when S603 is processed and when S604 is processed. In other words, when the focus is reached, it may be sticky to re-autofocus due to a certain subject change, and when it is out of focus, it may be sensitive to changes in the monitoring area.
In addition, according to the subject information value acquired in S605, a predetermined difference value can be reset as the ratio. It is preferable to set so as to respond to a change of about 10% to 20% of the S0 value.
With the autofocus device of this embodiment, the re-autofocus process can be accurately performed by changing the subject by changing the monitoring area when the focus is achieved and when the focus is stopped when the focus is stopped. As a result, it is possible to achieve both user-friendliness and superior power consumption.

It is the figure which showed the outline of the autofocus apparatus based on one Example of this invention. It is the figure which showed the autofocus processing procedure in the apparatus of FIG. FIG. 3 is a diagram of a subroutine used in the processing procedure of FIG. 2. FIG. 3 is a diagram of a subroutine used in the processing procedure of FIG. 2. It is a figure which shows the restart procedure based on the prior art which calls the autofocus processing procedure of FIG. It is a figure which shows the procedure of the restart which concerns on a present Example which calls the autofocus processing procedure of FIG. It is the figure which showed an example of the monitoring area | region used by the restart procedure of FIG. It is the figure which showed another example of the monitoring area | region used by the restart procedure of FIG. It is the figure which showed another example of the monitoring area | region used by the restart procedure of FIG. It is the figure which showed another example of the monitoring area | region used by the restart procedure of FIG.

Explanation of symbols

11: Lens device including a focus adjustment lens,
12: A diaphragm device,
13: an imaging device that performs photoelectric conversion,
14: Image processing apparatus having CDS, AGC, A / D function,
15: a bandpass filter (BPF) device for detecting a specific frequency component,
16: a region selection device for selecting a two-dimensional region on the screen;
17: A sharpness calculation device that performs a sharpness calculation from the BPF device 15 signal in the region selected by the region selection device 16;
18: a video state calculation device that calculates a specific video state amount from the BPF device 15 signal in the region selected by the region selection device 16;
19: a drive circuit device that performs timing control of the imaging device 13 and the image processing device 14,
20: A diaphragm control device for controlling the diaphragm device 12,
21: a lens driving device for controlling the focus adjustment lens;
22: System control device for controlling the above-mentioned device and performing calculation, result holding, etc.

Claims (12)

A lens,
Imaging means for converting an image formed through the lens into an electrical signal;
A region selecting means for selecting one or more of a plurality of types of two-dimensional regions comprising part or all of the video;
Sharpness calculation means for calculating a sharpness value of the video based on a video signal corresponding to the two-dimensional area selected by the area selection means from the imaging means;
Video state calculation means for calculating a video state value of the video based on a video signal corresponding to the two-dimensional area selected by the area selection means from the imaging means;
Lens driving means for driving the lens in the optical axis direction so that the sharpness value becomes a maximum value;
Drive control means for starting the driving of the lens when the video state value changes by a predetermined value or more,
The area selecting means is not able to identify the case where the driving is completed by specifying the position of the lens where the sharpness becomes maximum when the lens driving means drives the lens for the image state calculating means. An autofocus device, wherein a different two-dimensional region is selected when driving is finished.   The area selection means is not specified for the sharpness calculation means, when the lens driving means specifies the position of the lens where the sharpness reaches a maximum when the lens is driven and the driving is finished. The autofocus device according to claim 1, wherein a different two-dimensional region is selected when the driving is finished. A lens,
Imaging means for converting an image formed through the lens into an electrical signal;
A region selecting means for selecting one or more of a plurality of types of two-dimensional regions comprising part or all of the video;
Sharpness calculation means for calculating a sharpness value of the video based on a video signal corresponding to the two-dimensional area selected by the area selection means from the imaging means;
Lens driving means for driving the lens in the optical axis direction so that the sharpness value becomes a maximum value;
Drive control means for starting the driving of the lens by the lens driving means,
The region selection means includes a case where the lens driving means specifies the position of the lens where the sharpness becomes maximum when driving the lens, and a case where the driving ends without being specified. An autofocus device characterized by selecting different two-dimensional regions.   4. The image processing apparatus according to claim 2, further comprising a band pass filter that extracts a specific spatial frequency component from the video signal, wherein the sharpness calculation unit calculates the sharpness value based on the spatial frequency component. Autofocus device.   The drive control means includes a case where the lens driving means specifies the position of the lens at which the sharpness reaches a maximum when driving the lens, and a case where the driving ends without being specified. The autofocus device according to claim 1, wherein a criterion for determining that driving of the lens is necessary is made different.   The drive control means specifies the position of the lens and drives when the lens drive means finishes driving without specifying the position of the lens where the sharpness becomes maximum when driving the lens. 6. The autofocus device according to claim 5, wherein the determination criterion is set lower than that when the lens is finished, and is set to a side where the necessity of driving the lens can be sensitively detected.   7. The video state calculation unit according to claim 1, 2, 5, or 6, wherein the video state calculation unit calculates a video state value based on a luminance of a subject as an evaluation value for starting lens driving by the drive control unit. Autofocus device.   7. The image state calculation unit according to claim 1, 2, 5 or 6, wherein the image state calculation unit calculates an image state value based on a subject contrast as an evaluation value for starting lens driving by the drive control unit. Autofocus device.   7. The auto according to claim 1, 2, 5, or 6, wherein the video state calculation unit calculates a video state value based on a subject distance as an evaluation value for starting lens driving by the drive control unit. Focus device.   When the lens driving unit finishes driving without specifying the position of the lens where the sharpness reaches a maximum when the lens driving unit drives the lens, the region selecting unit specifies the position of the lens and performs driving. The autofocus device according to any one of claims 1 to 9, wherein a two-dimensional area that is wider than that in the case of completion is selected.   A camera comprising the autofocus device according to claim 1. An optical apparatus comprising the autofocus device according to any one of claims 1 to 10.

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