JP4228430B2 - Focus position determination method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a focal position determination method and apparatus for photographing a focused image in a video device such as a video camera or a digital still camera.
[0002]
[Prior art]
Various methods for determining a focus position for capturing a focused image are conventionally known. As the first method, for example, as disclosed in Japanese Patent Laid-Open No. 62-2385109, the focal position is moved from one of the most object side position and the most photographer side position to the other. The difference between the contrast of the image at the previous position and the contrast at the next position is obtained, and the focal position at the time when this difference turns from positive to zero or negative is determined as the position where focusing can be obtained. It was. This contrast is calculated from a high-frequency component obtained from the image signal, and the higher the focus is, the higher the value is.
[0003]
As a second method, for example, as disclosed in Japanese Patent Application Laid-Open No. 6-118297, first, contrast is obtained for the three points of the center of the movable range of the focal position and the positions of both end positions. If the contrast at the position is maximum, this is determined as the position where the focus can be obtained. Otherwise, it is determined which side has the higher contrast, and the contrast detection range is set to the higher contrast. While shifting to the position side, the in-focus state is sequentially determined based on whether or not the position is the maximum contrast position.
[0004]
[Problems to be solved by the invention]
However, in the above conventional method, when the obtained contrast is higher than the contrast obtained at other positions, the focus position is set to a position where the focus can be obtained. In order to obtain the contrast, the interval between the focal positions for obtaining the contrast must be reduced. For this reason, especially when the focus movement start position and the position where the focus can be obtained are separated from each other, it is necessary to repeat the focus movement and the contrast detection a considerable number of times. was there.
[0005]
In view of the above, it has been desired to realize a focus position determination method and apparatus capable of performing automatic focus adjustment in a short time.
[0006]
[Means for Solving the Problems]
The present invention employs the following configuration in order to solve the above-described problems.
<Configuration 1>
In the focal position determination method for determining the position of the imaging system so that the contrast of the image captured by the image sensor is maximized, By preparing at least two methods for determining the position of the imaging system, calculating the evaluation value related to the contrast of the captured image and comparing the evaluation value with the threshold value. A focal position determination method characterized by determining.
[0011]
<Constitution 2 >
Constitution 1 In the described focal position determination method, one of at least two methods is that the amount of movement to the position of the imaging system where the contrast of the image is maximum is preliminarily used as a function of the evaluation value related to the contrast of the captured image. When setting and determining the amount of movement to the position of the imaging system where the contrast of the image is maximum, first determine the evaluation value of the image captured by the image sensor, and then move based on the function from the evaluation value The other is a method for determining the amount, and the other is to calculate evaluation values relating to the contrast of images taken at three different imaging system positions, and based on these positions and evaluation values, A method for determining a focal position, characterized in that it is a method for calculating and determining the position of an imaging system that maximizes contrast.
[0016]
<Constitution 3 >
In a focal position determination apparatus that determines the position of an imaging system so that the contrast of an image captured by an imaging device is maximized, at least two means provided as means for determining the position of the imaging system, and at least two A focal position determination device comprising: a switch unit that determines which one of the means to adopt is calculated by calculating an evaluation value related to a contrast of a captured image and comparing the evaluation value with a threshold value .
[0017]
<Constitution 4 >
Constitution 3 In at least one of the two means for determining the focal position, the one of the means is a function of an evaluation value relating to the contrast of the photographed image, the amount of movement to the position of the imaging system where the contrast of the image is maximum. In order to obtain the amount of movement to the position of the imaging system where the contrast of the image is maximized, first, the evaluation value of the image captured by the image sensor is obtained, and then, based on the function from the evaluation value A first movement amount calculation unit that determines a movement amount, and another means calculates an evaluation value relating to a contrast of a video imaged at three different imaging system positions, and each position and A focal position determination device, which is a second movement amount calculation unit that calculates and determines the position of an imaging system that maximizes the contrast of an image based on each evaluation value.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail using specific examples.
<< Specific Example 1 >>
<Constitution>
FIG. 1 is a flowchart showing a specific example 1 of the focus position determination method of the present invention. Prior to this, a focus position determination apparatus for realizing the focus position determination method of the present invention will be described.
[0019]
FIG. 2 is a block diagram showing the focal position determining apparatus according to the first embodiment of the present invention.
The apparatus shown in the figure includes a lens 101, an image sensor 102, an A / D conversion unit 103, an evaluation value calculation unit 104, a movement amount calculation unit 105, an evaluation value storage unit 106, and a focal position movement unit 107.
[0020]
The lens 101 is an optical system that is moved by the focus position moving unit 107 and performs focus adjustment. The image sensor 102 is an element for capturing an image input via the lens 101 and outputting the image as a video signal.
[0021]
The A / D conversion unit 103 is a functional unit that converts an analog video signal output from the image sensor 102 into a digital image signal. The evaluation value calculation unit 104 is a functional unit that calculates an index value as an evaluation value indicating the degree of contrast from the digital image converted by the A / D conversion unit 103. The movement amount calculation unit 105 receives the index value obtained by the evaluation value calculation unit 104, stores the index value in the evaluation value storage unit 106 as the index value of the current image, and stores the index value in the evaluation value storage unit 106. It has a function of determining the moving amount and moving direction of the next focal position based on the previous index value. The evaluation value storage unit 106 is a storage unit for storing an index value as an evaluation value at least once in the past. The focal position moving unit 107 is a control unit that moves the lens 101 based on the output of the moving amount calculating unit 105.
[0022]
<Operation>
First, the operation of the A / D conversion unit 103 will be described.
The image is captured by the image sensor 102, and the output from the image sensor 102 is output as one frame of information as the voltage value changes. The A / D conversion unit 103 converts the change in voltage value into an integer value (density value) from 0 to 255, and expresses one frame of the video as an array of the integer values. Hereinafter, one frame of video represented as an array of integer values is referred to as a digital image. Also, the constituent elements of the digital image are called pixels.
[0023]
Generally, there are two parameters, a brightness adjustment parameter b and a contrast adjustment parameter c, when converting to an integer value. That is, the voltage value v is once converted into a converted value c (v + b) by the parameters b and c, and this value is converted from 0 to 255 depending on where the voltage range is divided into 256 equal parts. . The brightness adjustment parameter b is an offset of the voltage value v, and the contrast adjustment parameter c is an enlargement ratio of the voltage value v.
[0024]
In the following description, it is assumed that the digital image obtained by the A / D conversion unit 103 is composed of W × H pixels (horizontal W pixels, vertical H pixels), and this pixel position is the origin at the upper left pixel of the image. Expressed in the x, y coordinate system. The density value of the pixel at the position (x, y) is represented as I (x, y).
[0025]
Next, processing of the evaluation value calculation unit 104, the movement amount calculation unit 105, and the evaluation value storage unit 106 will be described with reference to FIG. First, the process of the evaluation value calculation unit 104 will be described.
[0026]
The evaluation value calculation unit 104 calculates an index value that is an evaluation value (step S1 in FIG. 1). This index value includes a pixel of interest (x, y) set at an interval of 2 s pixels in a processing range of horizontal w pixels and vertical h pixels set at the center of the image, and reference pixels adjacent to the upper, lower, left, and right sides at an s pixel interval. Based on the density difference, the following formula is used.
[0027]
Index = Σ {(I (x−s, y) −I (x, y)) ² + (I (x + s, y) -I (x, y)) ² + (I (x, ys) -I (x, y)) ² + (I (x, y + s) -I (x, y)) ² } (1)
However, the summation is performed for all pixels of interest.
[0028]
FIG. 3 is an explanatory diagram of the setting position of the target pixel.
In the figure, the processing range is a rectangular area of horizontal w pixels and vertical h pixels with the position (x, y) as the position of the upper left pixel. The target pixel is indicated by a black circle, and the reference pixel is indicated by a white circle. The pixel of interest is set at intervals of 2 s pixels in the horizontal direction, and pixels whose setting positions are shifted from each other by s pixels are alternately set in the vertical direction by s pixels.
[0029]
Note that the processing range and the position of the pixel of interest are set in advance depending on the object to be imaged, and the processing range may be, for example, not the entire screen but a limited area at the center of the image. Further, an interval s = 2 between adjacent pixels (every other pixel) may be set.
[0030]
Next, as a process of the movement amount calculation unit 105, a function set in advance will be described.
The movement amount calculation unit 105 determines the movement amount and movement direction of the focal position using the index value. In order to determine the amount of movement, the index value Index (P) of the image obtained at the focal position P is expressed as a function as a function of the amount of deviation ΔP from the focal position P and the position where the focus is obtained as shown in the following equation. Turn into.
[0031]
Index (P) = f (ΔP) (2)
Then, using the inverse function F of this function f, the movement amount is determined from the current index value In.
Movement amount = F (In) (3)
[0032]
Further, the moving direction is assumed to be toward the higher index value. Here, the calculated index value is compared with the index value stored in the evaluation value storage unit 106 calculated last time. If the current value is larger than the previous value, the current direction is the same as the previous movement. If the item is small, the direction is reversed.
[0033]
FIG. 4 is an explanatory diagram showing a change in index value and a function.
This figure shows the relationship between the focal position and the index value for a certain subject. The index value changes so that the focus position reaches a peak at the most focused position. The state of the change can be approximated using a hyperbola or the like. In the figure, a change in index value modeled by y = 200,000 / ΔP is shown. ΔP is the amount of movement up to the in-focus focal length, and ΔP = | 50−P | in FIG.
[0034]
According to such a modeling equation, the movement amount can be determined as ΔP = 200,000 / y. In this way, Equation (2) obtains changes in the focal position and index value relating to the subject in advance and sets them in advance to approximate this change.
[0035]
Next, the movement amount calculation process in the movement amount calculation unit 105 will be described.
The movement amount calculation unit 105 receives the current index value In output from the evaluation value calculation unit 104 (step S2). Next, in step S3, the end determination is performed by inspecting whether or not this In is greater than or equal to a preset threshold value Ie.
[0036]
If the index value In is less than the threshold value Ie as a result of the inspection in step S3, the index value In received from the evaluation value calculation unit 104 is stored in the evaluation value storage unit 106 (step S4). The focal position movement amount ΔP is calculated according to the equation (3) (step S5).
[0037]
Next, the previous index value Ip calculated last time and stored in the evaluation value storage unit 106 is read (step S6). Then, the latest index value In is compared with the previous index value Ip to determine the moving direction. That is, when In ≧ Ip, the moving direction of the focal position is the same as the previous direction, and when it is not, the reverse direction is set. The direction of movement from the camera side to the subject side is a plus direction, and the direction from the subject side to the camera side is a minus direction, and a sign representing this direction is added to the movement amount ΔP. This signed movement amount is stored in the movement amount calculation unit 105 and is referred to in the next movement amount determination. In step S8, a signed movement amount ΔP is output.
[0038]
<effect>
As described above, in this specific example, an index value related to the contrast of the captured video is calculated in advance, and this index is calculated. value And the amount of movement to the in-focus position are set, and the amount of movement to the in-focus position is determined based on this function, so that the imaging system can be focused with a small number of focal point movements. It can be moved to a position, so that a focused image can be taken at high speed.
[0039]
5 is shown in FIG. Close In the case of using a similar expression, the focal position when moving by the amount of movement obtained for each focal position before movement is shown.
[0040]
It can be seen that the focal position of the movement destination is generally within the range of the focal position ± 10 where the in-focus is obtained, and the focal position can be moved to a position that is substantially in focus by one movement. Here, the more accurately the function used for modeling reproduces the actual change in the index value, the more the focal position calculated by the inverse function becomes the position where a better focus can be obtained.
[0041]
In this specific example, the previous index value needs to be calculated in order to determine the moving direction, but the previously calculated index value cannot be used for the first movement. In this case, the initial focal position may be the most focal position from the camera, and the first moving direction may be the object side direction.
[0042]
<< Specific Example 2 >>
In the second specific example, a change in the index value is observed while moving the focal position, and the position where the in-focus is obtained is determined based on the result.
[0043]
<Constitution>
FIG. 6 is a configuration diagram of the focal position determining apparatus in the second specific example.
The apparatus shown in the figure includes a lens 201, an image sensor 202, an A / D conversion unit 203, an evaluation value calculation unit 204, a movement amount calculation unit 205, a history storage unit 206, and a focal position movement unit 207.
[0044]
Here, the lens 201, the image sensor 202, the A / D conversion unit 203, the evaluation value calculation unit 204, and the focus position moving unit 207 are the lens 101, the image sensor 102, the A / D conversion unit 103, and the evaluation value in the specific example 1. This is the same as the calculation unit 104 and the focus position moving unit 107.
[0045]
The movement amount calculation unit 205 has a function of calculating the in-focus position based on the index values of the images captured at three different imaging system positions calculated by the evaluation value calculation unit 204. That is, the movement amount calculation unit 205 calculates the in-focus position by using the index value of the video imaged at the center position among the three different focal positions, and the index value of the video imaged at the remaining two positions. When the above condition is satisfied, the change amount per unit section width of the index value from the central position to the remaining two positions is obtained, and the two positions that become the section where the change amount is large If one of the positions is set as one position, the remaining position is set as the other position, and the relationship of the index value with respect to the focal position is considered as a point in the XY coordinate system, the index value of one position is indicated. The straight line connecting the point indicating the index value of the center position from the point is extended to one straight line, and the other position is tilted opposite to this straight line. The straight line passing through the point indicating the index value as the other straight, and has a function of calculating a focal position of one line and the other lines and intersect point as focus position.
[0046]
The history storage unit 206 is a storage unit that can store the focus position and the index value at that time for at least the past three times.
[0047]
<Operation>
Since the image obtained by the image sensor 202 is converted into a digital image signal by the A / D converter 203 and the index value is calculated based on this, the description is omitted here. The operation after the movement amount calculation unit 205 will be described.
[0048]
FIG. 7 is a flowchart showing the operation of the movement amount calculation unit 205 in the focal position determination device.
[0049]
The movement amount calculation unit 205 receives the latest index value In from the evaluation value calculation unit 204 (step S21). Thereby, the movement amount calculation unit 205 checks whether or not the index value In is greater than or equal to a preset threshold value (step S22), and if so, the process ends. This threshold value is a threshold value for preventing an erroneous calculation of the in-focus position by inputting an index value that does not exist for some reason.
[0050]
Next, the current focus position Pn and the index value In are stored in the history storage unit 206 (step S23). In step S24, the focus positions and index values for the past two times are read from the history storage unit 206, respectively. In the following description, the previous and previous focal positions are Pp and Po, respectively, and the previous and previous index values are Ip and Io, respectively.
[0051]
Next, it is checked whether the movement from the previous focal position to the previous focal position and the movement from the previous focal position to the current focal position are in the same direction (step S25). Determine if it can be determined. This is done by determining whether the sign of the following value V is positive.
[0052]
V = (Pn−Pp) × (Pp−Po) (4)
If the direction is the same (V> 0), the previous index value Ip and the current index value In are compared in the next step S26. If Ip> In, the process further proceeds to step S27, where the previous index value Ip and the previous index value Io are compared. If Ip> Io in this step S27, that is, if Ip is larger than In or Io, the in-focus position is estimated in the next step S28.
[0053]
Here, the focal position determination method performed in step S28 will be described.
As a result of the determination in step S26 or step S27, the focal position and the index value from the previous time to the current time are as follows.
[0054]
FIG. 8 is an explanatory diagram of the operation of the movement amount calculation unit 205 and shows the status of index values.
In FIGS. 8A and 8B, the x-axis represents the focal position and the y-axis represents the index value, and the points A, B, and C represent the previous and current focal positions and index values, respectively. Yes. At this time, considering that the change in the index value is bilaterally symmetrical as shown in the figure, the two straight lines L1 and L2 having the same inclination and different signs are applied as shown in the figure. The focal position where the in-focus is obtained can be determined as the x coordinate of the intersection P. The straight line L1 is obtained by extending the larger one of the line segments AB and BC, and the straight line L2 is drawn so as to pass through the remaining one point.
[0055]
As shown in FIG. 8A, when the straight line L1 coincides with the line segment AB, the value S of the following equation is positive.
S = (Pp−Pn) (Ip−Io) + (Ip−In) (Pp−Po) (5)
[0056]
When S> 0, the x-coordinate Xp of the intersection P is obtained by the following equation.
Xp = {(Pp-Pn) Io + (Ip-In) Po-InPp + IpPn} / 2 (Ip-In) (6)
[0057]
When the straight line L1 coincides with the line segment BC as shown in FIG. 8B, the x coordinate Xp of the point P is obtained by the following equation.
Xp = {(Pp−Po) In + (Ip−Io) Pn−IoPp + IpPo} / 2 (Ip−Io) (7)
This value Xp is the focal position determined in step S28.
[0058]
Next, in step S29, the amount of movement from the current focal position to the determined focal position is output. This is Xp-Pn.
[0059]
If it is determined in step S25 and step S26 that the focal position where the in-focus is obtained cannot be determined, the standard movement amount is output in step S32. This standard movement amount is set in advance as a parameter for observing the index value. However, the moving direction is the reverse direction when Ip ≦ In.
[0060]
Further, as a result of the determination in step S27, when Ip ≦ Io, the index value gradually decreases. In this case, in step S31, the previous focus position Pp and index value Ip stored in the history storage unit 206 are replaced with the current focus position Pn and index value In. In step S32, the standard movement amount is output. However, the moving direction is the direction opposite to the current focal position from the previous focal position. This is to change the history so that the movement of the focal position is in the direction in which the index value increases.
[0061]
In step S <b> 30, the movement destination position is held in the movement amount calculation unit 205. This value is used as the current focal position in the next operation.
[0062]
<effect>
As described above, according to the second specific example, the index value is sequentially calculated while moving the focal position by the standard movement amount. If this position passes the position where the in-focus is obtained, the movement amount calculation unit 205 performs the focusing. The resulting position is determined and the focal position is moved to that position. Therefore, even if the basic movement amount is increased and rough movement is performed, the position where the in-focus can be obtained can be determined, and high-speed and accurate automatic focus adjustment can be performed.
[0063]
In addition, since the index value varies depending on the subject, it is difficult to apply the specific example 1 uniformly to various subjects, but the specific example 2 is an index as shown in FIG. Since only the left-right symmetry in the change in value is used, and this property is common to various subjects, automatic focus adjustment that does not limit the object can be realized.
[0064]
Further, in this specific example, since only three points of data are always used in the movement amount calculation process, the storage capacity of the history storage unit 206 and the processing amount of the evaluation value calculation unit 204 and the movement amount calculation unit 205 are also small. The effect of being finished is obtained.
[0065]
<< Specific Example 3 >>
In the third specific example, means for determining the positions of at least two imaging systems are prepared, and which one of these means is adopted is determined by comparing the index value with a threshold value. .
[0066]
<Constitution>
FIG. 9 is a configuration diagram of the focal position determining apparatus of the third specific example.
The illustrated apparatus includes a lens 301, an image sensor 302, an A / D conversion unit 303, an evaluation value calculation unit 304, a switch unit 305, a first movement amount calculation unit 306, a second movement amount calculation unit 307, and history storage. Part 308 and a focal position moving part 309.
[0067]
Here, the lens 301, the image sensor 302, the A / D converter 303, the evaluation value calculator 304, and the focus position moving unit 309 are the lens 101, the image sensor 102, the A / D converter 103, and the evaluation value in the specific example 1. This is the same as the calculation unit 104 and the focus position moving unit 107.
[0068]
The first movement amount calculation unit 306 has the same configuration as the movement amount calculation unit 105 in the first specific example. That is, when the amount of movement to the in-focus position is set in advance as a function of the index value of the captured image and the amount of movement to the in-focus position is obtained, first, the index value of the image captured by the image sensor 302 is determined. Next, the movement amount is determined from the index value based on the function.
[0069]
Further, the second movement amount calculation unit 307 has the same function as the movement amount calculation unit 205 in the specific example 2. That is, it has a function of calculating index values of videos taken at three different focal positions, and calculating and determining a focus position based on each position and each index value.
[0070]
Further, the switch unit 305 holds a certain threshold value, compares the threshold value with the index value obtained by the evaluation value calculation unit 304, and compares the first movement amount calculation unit 306 and the second movement amount calculation unit. 307 is a functional unit that performs switch processing for selecting which of 307 to perform movement amount calculation processing.
[0071]
Further, the history storage unit 308 is a storage unit that can store the focal position and the index value at that time for at least the past three times, as in the second specific example.
[0072]
<Operation>
First, since the operation up to the evaluation value calculation unit 304 is the same as that in the first and second specific examples, the subsequent operation will be described.
[0073]
The switch unit 305 is a part that controls which of the two movement amount calculation units 306 and 307 is driven. This determination is performed by setting the current index value In calculated by the evaluation value calculation unit 304 in advance. This is done by comparing with the threshold It.
[0074]
That is, if In ≦ It, the first movement amount calculation unit 306 is driven, and if In> It, the second movement amount calculation unit 307 is driven. However, the switch unit 305 stores the movement amount calculation unit that is currently driven, and after driving the second movement amount calculation unit 307, drives the first movement amount calculation unit 306 even if In ≦ It. The second movement amount calculation unit 307 is set to be driven as it is. Here, the threshold It may be set in advance as about 1/2 to 1/3 of the maximum value in the change in the index value of the subject shown in FIG.
[0075]
The first movement amount calculation unit 306 operates in the same manner as the movement amount calculation unit 105 in the first specific example. However, the movement amount calculation unit 105 in the specific example 1 internally stores the focal position of the movement destination and stores the received current index value in the evaluation value storage unit 106. Are stored in the history storage unit 308.
[0076]
On the other hand, the second movement amount calculation unit 307 operates in the same manner as the movement amount calculation unit 205 in the second specific example. The second movement amount calculation unit 307 also causes the history storage unit 308 to store the current focus position and index value. Therefore, even after the movement amount calculation unit driven by the switch unit 305 is switched from the first movement amount calculation unit 306 to the second movement amount calculation unit 307, the second movement amount calculation unit 307 does not change the first movement amount calculation unit 307. The past focal position and index value determined by the movement amount calculation unit 306 can be referred to.
[0077]
<effect>
As described above, according to specific example 3, as the movement amount calculation unit, first movement amount calculation unit 306 that performs the same processing as movement amount calculation unit 105 of specific example 1, and movement amount calculation of specific example 2 The second movement amount calculation unit 307 that performs the same processing as that of the unit 205 is provided, and these are selectively driven by comparing a preset threshold value with the current index value. Automatic focus adjustment can be performed.
[0078]
That is, the movement amount calculation unit of the first specific example can determine the position at which focusing can be achieved at a high speed by one movement even if the current focal position is considerably away from the position at which focusing is achieved. However, if the function used for modeling the index value is different from the actual change in the index value due to the difference in the subject or the like, the determined position includes a slight error. At this time, if the second movement amount calculation unit 307 is driven by the switch unit 305, the position where the focus is obtained can be determined by a method that is not limited to the subject. Here, by appropriately setting the threshold It in the switch unit 305, it is possible to perform automatic focus adjustment at high speed for an assumed subject and with high accuracy for an unexpected subject.
[0079]
In the specific example 3, the movement amount calculation unit is the first movement amount calculation unit 306 and the second movement amount calculation unit 307. However, the movement amount is calculated by another method. An amount calculation unit may be provided. For example, another moving amount calculation unit may be configured to measure the distance to the subject using sound waves, infrared rays, or the like and calculate the moving amount based on the distance measurement result.
[0080]
Further, in each of the above specific examples, the evaluation value is an index value as shown in Expression (1), but any value may be used as long as it indicates the degree of contrast of the video.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a specific example 1 of a focal position determination method according to the present invention.
FIG. 2 is a configuration diagram of a focal position determining device for realizing a specific example 1 of the focal position determining method of the present invention.
FIG. 3 is an explanatory diagram of a setting position of a target pixel in the focal position determination method and apparatus of the present invention.
FIG. 4 is an explanatory diagram showing a change in index value and a function in Example 1 of the focal position determination method and apparatus of the present invention.
FIG. 5 is an explanatory diagram showing the relationship between the pre-movement focal position and the post-movement focal position in the first specific example of the focal position determination method and apparatus of the present invention.
FIG. 6 is a configuration diagram of a specific example 2 of the focal position determining apparatus according to the invention.
FIG. 7 is a flowchart showing an operation of a movement amount calculation unit in the specific example 2 of the focal position determination device of the present invention.
FIG. 8 is an operation explanatory diagram of a movement amount calculation unit in a specific example 2 of the focal position determination device according to the invention.
FIG. 9 is a configuration diagram of a specific example 3 of the focal position determining apparatus according to the invention.
[Explanation of symbols]
101, 201, 301 lens
102, 202, 302 Image sensor
104, 204, 304 Evaluation value calculation unit
105, 205 Movement amount calculation unit
107, 207, 309 Focus position moving unit
305 Switch part
306 First movement amount calculation unit
307 Second movement amount calculation unit

Claims (4)

In the focal position determination method for determining the position of the imaging system so that the contrast of the image captured by the image sensor is maximized,
Preparing at least two methods for determining the position of the imaging system;
A method for determining a focal position, wherein which of the above methods is adopted is determined by calculating an evaluation value related to a contrast of a captured image and comparing the evaluation value with a threshold value. The focal position determination method according to claim 1,
Of at least two methods
One is that the amount of movement to the position of the imaging system where the contrast of the image is maximized is set in advance as a function of the evaluation value related to the contrast of the captured image, and the imaging system where the contrast of the image is maximized is set. In the case of obtaining the movement amount to the position, first, the evaluation value of the video imaged by the image sensor is obtained, and then the movement amount is determined from the evaluation value based on the function,
The other is to calculate evaluation values related to the contrast of images taken at three different imaging system positions, and based on each position and each evaluation value, an imaging system that maximizes the contrast of the image. A method for determining a focal position, wherein the position is calculated and determined. In the focal position determination device that determines the position of the imaging system so that the contrast of the image captured by the imaging element is maximized,
At least two means provided as means for determining the position of the imaging system;
A switch unit that determines which one of the at least two means is to be used is calculated by calculating an evaluation value related to a contrast of a captured image and comparing the evaluation value with a threshold value. Focus position determination device. In the focal position determination apparatus according to claim 3,
Of at least two means
One means presets the amount of movement to the position of the imaging system where the contrast of the image is maximum as a function of the evaluation value relating to the contrast of the captured image, and the imaging system where the contrast of the image is maximum In order to obtain the movement amount to the position, first, an evaluation value of a video imaged by the image sensor is obtained, and then a first movement amount calculation for determining the movement amount based on the function from the evaluation value. Department,
The other means calculates the evaluation value related to the contrast of the video imaged at the positions of three different imaging systems, and based on each position and each evaluation value, the image forming the image with the maximum contrast. A focal position determination device, being a second movement amount calculation unit that calculates and determines the position of a system.

Images