JP2002122773A - Focusing unit, electronic camera and focusing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focusing unit constituted, so that the time required for focusing can be shortened, and also the focal position can be appropriately set. SOLUTION: The unit is provided with a focusing means 11 for adjusting the focal position so that an object image is formed on an imaging device 12, a moving means 15 moving the focusing means, detecting means 18 and 19 detecting the focal position, based on the contrast value of an image signal obtained, while moving the focusing means, and a scanning range setting means 19 setting a scanning range, that is, a focusing means moving range for detecting the focal position, so that the scanning range may be within or below the focusing possible range of the focusing means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a focusing device, an electronic camera, and a focusing method.

[0002]

2. Description of the Related Art As one of automatic focusing (AF) systems, a contrast system (hill climbing system) is known.
This method moves the focusing lens (extends and retracts)
An image signal is acquired while performing the above operation, a position where the high-frequency component (contrast value) becomes a peak is determined as an in-focus position, and the in-focus lens is moved to that position (for example, "NHK Technical Report (Showa 40 Year, Volume 17, Volume 1
No. 86, pages 21 to 37) ").

More specifically, as shown in FIG. 10, first, a focusing lens is driven in an arbitrary direction to determine an increase or decrease in contrast value (Y1; direction determination processing). Subsequently, based on the direction determination result, the focusing lens is driven in the direction in which the contrast value increases, and it is determined that the focusing lens has passed the focusing position by shifting from the increasing direction to the decreasing direction in the contrast value. (Y2: In-focus position over determination processing). afterwards,
The focusing lens is returned to the maximum position (peak position) of the contrast value, that is, the focus position (Y3; focus position return processing), and the AF processing ends.

[0004]

However, conventionally, in consideration of the influence of noise such as flicker, the driving distance of the focusing lens in the direction determination processing and the in-focus position determination processing is increased, so that the AF processing is performed. The time spent on was long. Therefore, in the case of continuous shooting in which continuous shooting is performed at short time intervals, it is difficult to perform the above-described AF processing for each shooting. After that, the photographing is performed in the locked state without performing the AF process.
Therefore, in the second and subsequent shootings, it cannot be said that shooting is always performed at an appropriate focus position.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and can reduce the time spent for focusing processing and can set an appropriate focusing position. It is intended to provide a camera and a focusing method.

[0006]

A focusing apparatus according to the present invention comprises a focus adjusting means for adjusting a focus position so that a subject image is formed on an image sensor, and a moving means for moving the focus adjusting means. Detecting means for detecting a focus position based on a contrast value of an image signal acquired while moving the focus adjustment means, and scanning for moving the focus adjustment means for detecting the focus position Scanning range setting means for setting the range within a range in which the focus adjustment means can adjust the focus and a range narrower than the range.

A preferred embodiment of the focusing device is as follows.

(1) The above-mentioned scanning range setting means sets the above-mentioned scanning range so as to be distributed with reference to a specific position.

(2) The moving means moves the focus adjusting means from the specific position to any one end of the scanning range without acquiring the image signal by the detecting means. The focus adjusting unit is moved toward the other end of the scanning range while acquiring the image signal by the detecting unit.

(3) There is provided a scanning range selecting means for selecting whether the scanning range is the focus adjustable range of the focus adjusting means or the scanning range set by the scanning range setting means.

(4) When the in-focus position cannot be detected by the detection means, the specific position is regarded as the in-focus position.

(5) The scanning range setting means changes the distribution width of the scanning range based on the specific position based on the moving direction of the focusing position up to that time.

An electronic camera according to the present invention includes the above-mentioned focusing device, and a photographing mode selecting means for selecting a continuous photographing mode or a still image photographing mode.
When the continuous shooting mode is selected, the scanning range set by the scanning range setting means is selected.

The preferred embodiment of the electronic camera is as follows.

(1) The scanning range selecting means has a changing means for changing the scanning range set by the scanning range setting means.

(2) The changing means changes the scanning range according to the contrast value of the image signal.

(3) The changing means changes the scanning range according to the luminance value of the subject.

(4) A variable focus photographing system is further provided, and the scanning range setting means sets the scanning range so that the distance range to the subject is constant regardless of the focal length of the variable focus photographing system.

In the focusing method according to the present invention, an image signal is obtained while moving a focus adjusting means within a predetermined scanning range,
This is a focusing method for detecting a focus position based on a contrast value of an acquired image signal, and in a case of a specific shooting mode, a scanning range of the focus adjustment unit is set to a normal position based on a specific position. A focus position is detected by setting the scan range to a range narrower than the scan range in the photographing mode.

[0020]

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

(Apparatus Configuration) FIG. 1 is a block diagram showing a configuration example of a main part of an electronic camera according to an embodiment of the present invention.

The basic configuration of the image pickup unit is the same as that of a normal electronic camera, and includes a photographing lens system 11 (such as a focusing lens),
An image sensor 12 such as a CCD for photoelectrically converting a subject image (subject light) formed by the photographing lens system 11, and an image processing circuit for performing signal amplification, sample hold, A / D conversion, luminance / color conversion, and the like. 13.
The lens of the taking lens system 11 is driven by a lens drive motor 15 based on control from a motor drive circuit 14.

A signal generating circuit (SG circuit) 16 generates a reference signal (horizontal synchronizing signal, vertical synchronizing signal, etc.) necessary for video signal processing and the like. Various timings of the circuit 13 and the like are controlled. The output of the imaging processing circuit 13 is connected to an output terminal unit 17 so that an image signal can be output to a recording / reproducing system (not shown) via the output terminal unit 17.

The output of the image processing circuit 13 is input to a band-pass filter (BPF) 18, which extracts a high-frequency component for evaluating the degree of focusing from the luminance signal. .

The arithmetic processing circuit 19 is for controlling each part of the electronic camera, and includes a CPU, a ROM, a RAM,
It is composed of a timer and the like.

In the arithmetic processing circuit 19, photometric processing (AE processing) is performed by integrating the luminance signal (Y signal) output from the imaging processing circuit 13, and white balance is performed by the color signal (C signal). Processing (WB processing) is performed. Further, the high-frequency component (contrast value) extracted by the band-pass filter 18 is integrated, and an automatic focusing process (AF process) is performed based on the evaluation value (AF evaluation value). At this time, a plurality of integration areas can be set or made variable using a vertical synchronization signal (VD signal) and a horizontal synchronization signal (HD signal). Similarly, a plurality of AE / WB areas can be set or made variable. Further, a function (element shutter function) for making the accumulation integration time of the image sensor 12 variable in the AE processing is also provided.

The arithmetic processing circuit 19 also performs processing relating to the focusing lens position. That is, a function of moving the focusing lens of the photographic lens system 11 to the focusing position by driving the lens driving motor 15 via the motor driving circuit 14 during AF is provided. Also, in the continuous shooting mode, a function for setting the scanning range of the focusing lens to a range narrower than the scanning range in the normal still image shooting mode, the focal length of the shooting lens, the contrast value of the image signal, or the brightness of the subject. It has the function of changing the scanning range according to the value.

The operation unit 20 is composed of various switches such as a release button and a mode switch for switching a shooting mode to a continuous shooting mode or a normal still image shooting mode.

(Operation) Next, the operation of the electronic camera according to the embodiment of the present invention will be described with reference to flowcharts and the like.

FIG. 2 is a flowchart showing a basic operation example of the focusing process in the electronic camera.

First, it is determined whether the continuous shooting mode is selected or the normal still image shooting mode is selected (S1). When the still image shooting mode is selected, the driving range (scanning range) of the focusing lens is set to a normal driving range, that is, a normal focus adjustable range for detecting a focus position (S2). Then, normal AF processing is performed (S3).

If the continuous shooting mode is selected, it is first determined whether or not it is the first frame of continuous shooting (S4). If it is the first frame, the same focusing processing as usual is performed. . If it is the second or subsequent sheet, the driving range (scanning range) of the focusing lens is set within the normal driving range (focusable range) and narrower than that (S5). Since continuous shooting is performed continuously at short time intervals, it is generally difficult to imagine that the subject moves greatly between continuous shootings. Therefore,
In the case of the continuous shooting mode, the driving range of the focusing lens is set narrower than the normal driving range, so that the focusing processing time is shortened. More specifically, as shown in FIG. 3, the drive range is divided into narrow ranges on both sides around the current focus position (the focus position of the previous shooting). The driving range is, for example, about four times the depth of focus.

After setting the driving range of the focusing lens, FIG.
As shown in (5), the focusing lens is moved at high speed to one end point of the driving range. At this time, the focusing lens is moved without performing the conventional direction determination processing, that is, without performing the signal detection processing for the AF processing (S6). Subsequently, the focusing lens is moved to the other end point of the driving range with the determination that the focus position is exceeded, that is, with the signal detection processing for the AF processing (S7). Further, the focus lens is moved to the focus position detected by the focus position over determination (S8). In the process of S7, it is not necessary to move the focusing lens to the other end point of the driving range. If it is determined that the in-focus position has been exceeded during the movement of the focusing lens to the other end point, the process proceeds to that stage. The movement to the other end point may be stopped and returned to the focus position.

As described above, in the present embodiment, the drive range of the focusing lens is set to be smaller than the normal drive range in the continuous shooting mode by utilizing the fact that the focus range is generally narrow during continuous shooting. Since the focus lens is set to be narrow and the focusing lens is moved to one end point without performing the direction determination processing as in the related art, it is possible to significantly reduce the time spent in the AF processing as compared with the related art. Therefore, high-speed continuous shooting can be performed at an appropriate in-focus position.

FIG. 5 is a flowchart showing another operation example of the focusing process in the electronic camera. This operation example relates to processing (error processing) when the in-focus position cannot be detected.

When the continuous shooting mode is selected and the second and subsequent shots of the continuous shooting are performed, the driving range (scanning range) of the focusing lens is shifted from the normal driving range in the same manner as in the example shown in FIG. Is also set to a narrow range (S21), and then the focusing lens is driven from the current focusing position (the focusing position of the immediately preceding photographing, that is, the focusing position of the first photograph when photographing the second photograph) P The focusing lens is moved to one end point of the range at a high speed (S22), and the focusing lens is moved to the other end point of the driving range (S23) while determining that the focus position has been exceeded.

Thereafter, it is determined whether or not the in-focus position determination has been normally performed (S24). If the in-focus position determination has been normally performed, similar to the example shown in FIG.
The in-focus lens is moved to the in-focus position detected by the in-focus position determination (S25). If the in-focus position is not detected by the over-focus position determination, the original in-focus position (the in-focus position of the immediately preceding shooting) P is regarded as the in-focus position, and the focusing lens is moved to that position. Is moved at high speed (S2
6).

By performing such error processing,
Even when the in-focus position cannot be detected, continuous shooting can be reliably performed.

FIGS. 6 and 7 are flowcharts showing another example of the operation of the focusing process in the electronic camera. These operation examples relate to processing for changing the scanning range of the focusing lens according to the brightness value of the subject or the contrast value of the image signal when the continuous shooting mode is selected.

First, with reference to FIG. 6, an operation example in the case where the scanning range of the focusing lens is changed according to the luminance value of the subject will be described.

First, the luminance value obtained by the photometric processing described above is input (S41), and it is determined whether or not the luminance value is greater than a predetermined value K1 (S42). When the luminance value is not larger than K1, that is, when the luminance value is K
If it is equal to or less than 1, the driving range (scanning range) of the focusing lens is set wider than the normal driving range (hereinafter referred to as a normal narrow range) for the second image in the continuous shooting mode (S4).
3). If the luminance value is greater than K1, it is determined whether the luminance value is greater than a predetermined value K2 (where K2> K1) (S44). If the brightness value is not larger than K2, that is, if the brightness value is larger than K1 and equal to or smaller than K2, the driving range of the focusing lens is set to a normally narrow range (S45). If the luminance value is larger than K2, the driving range of the focusing lens is set to be narrower than the normal narrow range (S46). This is because a brighter subject is generally easier to detect the peak value of the contrast.

After setting the driving range of the focusing lens in this way, the focusing lens is moved to the focusing position in the same manner as in steps S5 to S7 shown in the flowchart of FIG. 2 (S47 to S49). .

Next, with reference to FIG. 7, an operation example in which the scanning range of the focusing lens is changed according to the contrast value of the image signal will be described.

First, a contrast value is input (S8).
1) It is determined whether the contrast value is greater than a predetermined value C1 (S82). When the contrast value is not larger than C1, that is, when the contrast value is equal to or smaller than C1, the driving range (scanning range) of the focusing lens is set wider than the normal narrow range in the continuous shooting mode (S83). If the contrast value is greater than C1, it is determined whether the contrast value is greater than a predetermined value C2 (where C2> C1) (S84). When the contrast value is not larger than C2, that is, when the contrast value is larger than C1 and equal to or smaller than C2, the driving range of the focusing lens is set to a normally narrow range (S85). The contrast value is C2
If it is larger, the driving range of the focusing lens is set narrower than the normal narrow range (S86).

After setting the drive range of the focusing lens in this manner, the focusing lens is moved to the focusing position in the same manner as in steps S5 to S7 shown in the flowchart of FIG. 2 (S87 to S89). .

As described above, by changing the scanning range of the focusing lens according to the predetermined parameter values such as the luminance value and the contrast value, it is possible to ensure the focus determination and to speed up the focusing process. Becomes possible.

In the above-described example, the brightness value and the contrast value are used independently as the determination targets for changing the scanning range. However, the determination may be made by combining these values.

FIG. 8 shows a zoom lens (variable focus photographing system).
5 shows the relationship between the subject distance and the position of the focusing lens (focus lens).

As shown in FIG. 8, the focusing curve representing the focusing lens position corresponding to the subject distance changes according to the designated focal length. When the mode is not the continuous shooting mode or the first frame of the continuous shooting, the moving range of the focusing lens is a range a at the tele end and a range b at the wide end. On the other hand, in the second and subsequent frames of the continuous shooting, a fixed narrow range c corresponding to the subject distance is set, and the actual moving range of the focusing lens is range d at the tele end and range e at the wide end. That is, when the zoom lens is used, a constant narrow range c is set corresponding to the subject distance regardless of the designated focal length, and the actual moving range of the focusing lens is designated for the second and subsequent images in continuous shooting. Will change according to the focal length.

FIG. 9 shows a modified example of how to set the scanning range of the focusing lens. The scanning range of the focusing lens may be equally distributed on both sides of the current focusing position, but from the viewpoint described below, the distribution width of the scanning range based on the current focusing position is described below. May be different from each other.

Since continuous shooting is performed continuously at short time intervals, the subject generally moves in the same direction during continuous shooting. Therefore, based on the moving direction of the subject until the previous shooting, that is, the driving direction of the focusing lens until the previous shooting (moving direction of the focus position)
, The in-focus position at the time of the next shooting can be predicted to some extent.

The examples shown in FIGS. 9A to 9C show the respective in-focus positions in three consecutive shootings. In FIG. 9 (c), the previous focus position (FIG. 9 (b)) is used as a reference based on the moving direction of the focus position in the previous (FIG. 9 (a)) and previous (FIG. 9 (b)) shooting. The distribution widths (SC1, SC2) of the scanning ranges on both sides are different from each other. That is, the distribution width in the same direction as the previous moving direction is relatively increased.

As described above, the focusing lens can be efficiently driven by changing the distribution width of the scanning range based on the moving direction of the focusing position until the previous photographing, and the focusing process can be performed. It is possible to increase the speed.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be variously modified and implemented without departing from the gist of the present invention. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining the disclosed constituent elements. For example, even if some constituent elements are deleted from the disclosed constituent elements, they can be extracted as an invention as long as a predetermined effect can be obtained.

[0055]

According to the present invention, by setting the scanning range of the focus adjusting means such as a focusing lens to be narrower than a normal scanning range at the time of continuous photographing or the like, the time spent for focusing processing can be reduced. It is possible to shorten the time and to set an appropriate focus position.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a main part of an electronic camera according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a basic operation example of a focusing process according to the embodiment of the present invention.

FIG. 3 is a diagram showing a scanning range of a focusing lens according to the embodiment of the present invention.

FIG. 4 is a view showing a method of scanning a focusing lens according to the embodiment of the present invention.

FIG. 5 is a flowchart illustrating another operation example of the focusing process according to the embodiment of the present invention.

FIG. 6 is a flowchart illustrating another operation example of the focusing process according to the embodiment of the present invention.

FIG. 7 is a flowchart showing another operation example of the focusing process according to the embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between a subject distance and a focusing lens position according to the embodiment of the present invention.

FIG. 9 is a diagram showing a modified example of how to set a scanning range of a focusing lens according to the embodiment of the present invention.

FIG. 10 is a diagram illustrating a scanning method of a focusing lens according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Photographing lens system 12 ... Image sensor 13 ... Image processing circuit 14 ... Motor drive circuit 15 ... Lens drive motor 16 ... Signal generation circuit 17 ... Output terminal part 18 ... Band pass filter 19 ... Arithmetic processing circuit 20 ... Operation part

Claims (12)

[Claims] A focus adjustment means for adjusting a focus position such that a subject image is formed on an image sensor; a movement means for moving the focus adjustment means; Detecting means for detecting a focus position based on a contrast value of an image signal; and a scanning range in which the focus adjusting means is moved to detect the focus position, within a focus adjustable range of the focus adjusting means. And a scanning range setting means for setting the range to a narrower range. 2. The focusing apparatus according to claim 1, wherein said scanning range setting means sets the scanning range so as to be distributed with reference to a specific position. 3. The moving means moves the focus adjusting means from the specific position to any one end of the scanning range without acquiring an image signal by the detecting means.
3. The focusing device according to claim 2, wherein the focus adjustment unit is moved toward the other end of the scanning range while acquiring the image signal by the detection unit. 4. A scanning range selecting means for selecting whether the scanning range is a focus adjustable range of the focus adjusting means or a scanning range set by the scanning range setting means. The focusing device according to claim 1, wherein: 5. The focusing apparatus according to claim 2, wherein when the in-focus position cannot be detected by the detection means, the specific position is regarded as the in-focus position. 6. The apparatus according to claim 2, wherein the scanning range setting means changes the distribution width of the scanning range based on the specific position based on the moving direction of the in-focus position. Focusing device. 7. A focusing device according to claim 4, further comprising: a photographing mode selecting means for selecting a continuous photographing mode or a still image photographing mode, wherein said scanning range selecting means selects a continuous photographing mode. An electronic camera which selects a scanning range set by the scanning range setting means when the electronic camera is turned on. 8. The electronic camera according to claim 7, wherein said scanning range selecting means has a changing means for changing a scanning range set by said scanning range setting means. 9. An electronic camera according to claim 8, wherein said changing means changes a scanning range according to a contrast value of an image signal. 10. The electronic camera according to claim 8, wherein said changing means changes a scanning range according to a luminance value of a subject. 11. A variable focus photographing system further comprising: a scanning range setting means for setting a scanning range so that a distance range to a subject is constant regardless of a focal length of the variable focus photographing system. The electronic camera according to claim 7, wherein 12. A focusing method for acquiring an image signal while moving a focus adjusting means within a predetermined scanning range, and detecting a focus position based on a contrast value of the acquired image signal. In the case of the photographing mode, the focus position is detected by setting the scanning range of the focus adjusting unit to a range narrower than the scanning range of the normal photographing mode based on a specific position. Focusing method.