JP2013130683A5 - - Google Patents

Description

In order to solve the above-described problems, the present invention provides an imaging unit that sequentially generates an imaging signal by photoelectrically converting light from a subject while the focus lens is moving, and a contrast of the subject from the imaging signal corresponding to a predetermined area. an imaging apparatus comprising: a generating means for generating a focus signal, a control unit for controlling the driving of the focus lens based on the focus signal indicating the control unit, a scan for driving the focus lens in one direction in operation, the gradient of the focus signal with respect to the position of the focus lens based on whether the first threshold value or more to change the driving speed of the focus lens, the first threshold value, the contrast value of the subject, the subject frequency, size of the predetermined area, aperture state, to at least one group of the driving speed of the current of the focus lens There characterized in that it is set.

The present invention is a method for controlling an imaging apparatus , the step of photoelectrically converting light from a subject while a focus lens is moving to sequentially generate an imaging signal, and the imaging signal corresponding to a predetermined region from the imaging signal. The focus signal with respect to the position of the focus lens in a step of generating a focus signal indicating contrast, a step of controlling driving of the focus lens based on the focus signal, and a scanning operation of driving the focus lens in one direction Changing the driving speed of the focus lens based on whether or not the gradient is equal to or higher than a first threshold, wherein the first threshold is the contrast value of the subject, the frequency of the subject, and the predetermined region setting of the basis of size, aperture state, to at least one of the driving speed of the current of the focus lens Characterized in that that.

The present invention is a program to be executed by a computer of an imaging apparatus, the step of photoelectrically converting light from a subject during the movement of a focus lens to sequentially generate an imaging signal, and the imaging signal corresponding to a predetermined area Generating a focus signal indicating the contrast of the subject from the image, a step of controlling the driving of the focus lens based on the focus signal, and a scan operation for driving the focus lens in one direction with respect to the position of the focus lens. Changing the driving speed of the focus lens based on whether or not the gradient of the focus signal is equal to or higher than a first threshold, wherein the first threshold is the contrast value of the subject, the frequency of the subject, the size of the predetermined area, aperture state, little of the driving speed of the current of the focus lens Characterized in that it is set based on one both.

Next, calculation of the gradient evaluation value slope threshold SlopeThr in S309 of FIG. 3, S409 of FIG. 4, and S503 of FIG. 5 will be described with reference to FIG. FIG. 8 is a flowchart showing processing for calculating the gradient evaluation value slope threshold SlopeThr in S309 of FIG. 3, S409 of FIG. 4, and S503 of FIG.
First, in step S801, the system control unit 113 checks the current aperture and the state of the shutter 102, and acquires the current aperture value. Then, the process proceeds to S802.
In step S802, the system control unit 113 acquires the size of the distance measurement area set in step S301. Then, the process proceeds to S803.
In step S803, the system control unit 113 acquires the contrast value in the distance measurement area set in step S301. Then, the process proceeds to S804. The “contrast value in the distance measurement area” is the difference between the maximum value and the minimum value of the luminance values in the distance measurement area set in S301. Thereby, even if the subject is not in focus, the contrast of the subject in the distance measurement area can be grasped to some extent.
In step S804, the system control unit 113 acquires the frequency within the distance measurement area set in step S301. Then, the process proceeds to S805. Various known methods can be applied to obtain the frequency within the distance measurement area. Therefore, detailed description is omitted.
In step S <b> 805, the system control unit 113 acquires the current focus speed of the focus lens 104. Then, the process proceeds to S806.
In S806, a reference value SlopeThr0 is determined. The reference value SlopeThr0 is a value that serves as a reference for the focus evaluation value gradient threshold SlopeThr when calculating the focus evaluation value gradient threshold SlopeThr in S807 described later. The reference value SlopeThr0 is determined in the setting of the reference subject and the electronic camera 1. Further, how to determine the reference value SlopeThr0 may be changed depending on the application. For example, in the initial focus drive in S303 of FIG. 3, the focus speed may be reduced at a position that exceeds the peak of the focus evaluation value of the subject so that the peak of the focus evaluation value of the subject can be detected during the AF scan operation performed later. . On the other hand, during the AF scan operation, the focus lens speed must be reduced before the peak position of the focus evaluation value of the subject is exceeded in order to ensure the necessary AF accuracy. Therefore, SlopeThr0 is changed in S409 or S502 during initial focus driving before AF scan and in S309 during AF scan operation. Specifically, the reference value SlopeThr0 in the initial focus drive is set to be larger than the reference value SlopeThr0 in the AF scan operation. Therefore, the value of the gradient threshold value SlopeThr of the focus evaluation value in the initial focus drive is larger than the value of the gradient threshold value SlopeThr of the focus evaluation value in the AF scan operation. According to such a configuration, in the initial focus drive, the focus lens 104 can be quickly moved to a predetermined scan start position. In the AF scan operation, AF accuracy can be increased. Then, the process proceeds to S807.
In step S <b> 807, the system control unit 113 calculates a focus evaluation value gradient threshold SlopeThr. The focus evaluation value gradient threshold SlopeThr is calculated by, for example, the following equation.

SlopeThr = SlopeThr0 × MMP × WinSize × Freq × (1 / Speed) × (1 / FNum)

FNum: coefficient determined by the aperture value MMP: coefficient determined by the contrast in the distance measurement area Freq: coefficient determined by the frequency in the distance measurement area WinSize: coefficient determined by the size of the distance measurement area Speed: coefficient determined by the focus speed

Hereinafter, the method of determining the above-described SlopeThr0 and each coefficient will be described. First, the F value (FNum0), the subject contrast value (MMP0), the subject frequency (Freq0), the distance measurement area size (WinSize0), and the focus speed (Speed0), which are the references, are temporarily determined. From the focus evaluation value peak shape under the condition, the slope of the focus evaluation value peak at the timing when the focus speed is desired to be decelerated is set to SlopeThr0. FNum is a coefficient determined by the aperture value. When the aperture value changes, the depth of focus changes and the gradient of the focus evaluation value peak changes. Therefore, FNum is used as a coefficient for changing SlopeThr according to the aperture value. As the aperture value increases, the depth of focus becomes deeper and the gradient becomes smaller.

FNum = current F value / FNum0

Calculate and decide on. MMP is a coefficient determined by the contrast in the distance measurement area. Since the gradient of the focus evaluation value peak increases as the contrast value increases, the MMP is, for example,

MMP = current subject contrast value / MMP0

Calculate and decide on. Freq is a coefficient determined by the frequency in the ranging area. Since the gradient of the focus evaluation value peak increases as the frequency of the subject increases, Freq is, for example,

Freq = Current subject frequency / Freq0

Calculate and decide on. WinSize is a coefficient determined by the size of the distance measurement area. As the size of the distance measurement area increases, the signal amount increases and the gradient of the focus evaluation value peak also increases.

WinSize = current WiSize / WinSize0

Calculate and decide on. Speed is a coefficient determined by the focus speed. Since the gradient of the focus evaluation value peak increases as the speed increases, the speed is, for example,

Speed = Current focus speed / Speed0

Calculate and decide on.
In this calculation formula, the gradient threshold value SlopeThr of the focus evaluation value is calculated using all of the coefficients as the reference value SlopeThr0. However, the calculation formula may be calculated using at least one of the coefficients. . According to such a calculation method, the gradient threshold value SlpeThr of the focus evaluation value is determined based on at least one of the contrast value of the subject, the frequency of the subject, the size of the ranging area, the aperture state, and the focus speed.
Thereby, even when the shape of the focus evaluation value differs depending on the setting of the subject and the camera, it is possible to appropriately determine the subject peak position. Then, the process proceeds to any of S310, S409, and S503.

Claims (14)

An imaging unit that sequentially generates an imaging signal by photoelectrically converting light from the subject while the focus lens is moving; a generating unit that generates a focus signal indicating the contrast of the subject from the imaging signal corresponding to a predetermined region; an imaging apparatus and a control section for controlling the driving of the focus lens based on the focus signal,
The control unit, in a scan operation for driving the focus lens in one direction, changes the driving speed of the focus lens based on whether a gradient of the focus signal with respect to the position of the focus lens is equal to or higher than a first threshold,
Wherein the first threshold value, characterized the contrast value of the subject, the frequency of the subject, the size of the predetermined area, aperture state, to be set based on at least one of the driving speed of the current of the focus lens An imaging device. The controller, when driving the focus lens at a first speed during the scanning operation, when a gradient of the focus signal with respect to the position of the focus lens is equal to or higher than the first threshold, The imaging apparatus according to claim 1, wherein a driving speed of the focus lens is changed to a second speed smaller than the first speed. The controller performs an initial operation for driving the focus lens in a direction opposite to the scan operation before the scan operation, and starts the scan operation based on the focus signal acquired during the initial operation. The imaging apparatus according to claim 1, wherein a driving speed of the focus lens at the time of performing is set. The controller performs an initial operation of driving the focus lens in a direction opposite to the scan operation before the scan operation, and the gradient of the focus signal acquired at the end of the initial operation with respect to the position of the focus lens is The imaging apparatus according to claim 2, wherein when it is equal to or higher than a second threshold, the driving speed of the focus lens when starting the scanning operation is set to the second speed. When the gradient of the focus signal acquired at the end of the initial operation with respect to the position of the focus lens is smaller than the second threshold and satisfies a predetermined imaging condition, the control unit is configured to start the scan operation. The imaging apparatus according to claim 4, wherein the driving speed of the focus lens is set to the first speed. The imaging apparatus according to claim 4, wherein the second threshold is larger than the first threshold. The first threshold value when the contrast value of the subject is a first value is larger than the first threshold value when the contrast value of the subject is a second value lower than the first value. The imaging apparatus according to claim 1, wherein the imaging apparatus is set. The first threshold value when the frequency of the subject is a third value is set to be larger than the first threshold value when the frequency of the subject is a fourth value lower than the third value. The image pickup apparatus according to claim 1, wherein the image pickup apparatus is an image pickup apparatus. The first threshold value when the size of the predetermined area is a fifth value is compared with the first threshold value when the size of the predetermined area is a sixth value smaller than the fifth value. The imaging device according to claim 1, wherein the imaging device is set to be large. The first threshold value when the aperture state is the first state is set smaller than the first threshold value when the aperture state is the second state on the open side with respect to the first state. The image pickup apparatus according to claim 1, wherein the image pickup apparatus is an image pickup apparatus. The first threshold value when the current driving speed of the focus lens is the first speed is the first threshold value when the current driving speed of the focus lens is a second speed smaller than the first speed. The imaging apparatus according to claim 1, wherein the imaging apparatus is set to be smaller than a threshold value. The contrast value of the subject, the imaging apparatus according to any one of claims 1 to 11, wherein the is a value based on the difference between the maximum value and the minimum value of the luminance values in a predetermined region. A method for controlling an imaging apparatus ,
During the movement of the focus lens, photoelectrically converting light from the subject to sequentially generate imaging signals;
Generating a focus signal indicating a contrast of a subject from the imaging signal corresponding to a predetermined region;
Controlling the driving of the focus lens based on the focus signal;
In a scan operation for driving the focus lens in one direction, changing a driving speed of the focus lens based on whether a gradient of the focus signal with respect to the position of the focus lens is equal to or higher than a first threshold;
The first threshold value is set based on at least one of the contrast value of the subject, the frequency of the subject, the size of the predetermined region, the aperture state, and the current driving speed of the focus lens. A method for controlling the imaging apparatus. A program to be executed by a computer of an imaging apparatus ,
During the movement of the focus lens, photoelectrically converting light from the subject to sequentially generate imaging signals;
Generating a focus signal indicating a contrast of a subject from the imaging signal corresponding to a predetermined region;
Controlling the driving of the focus lens based on the focus signal;
In a scan operation for driving the focus lens in one direction, changing a driving speed of the focus lens based on whether a gradient of the focus signal with respect to the position of the focus lens is equal to or higher than a first threshold;
The first threshold value is set based on at least one of the contrast value of the subject, the frequency of the subject, the size of the predetermined region, the aperture state, and the current driving speed of the focus lens. Program.