JPH04261509A - Focusing controlling apparatus and distance measuring method - Google Patents

Abstract

PURPOSE: To perform optimum focusing in a short time by obtaining the moving amount of an image pickup lens to a focusing position with arithmetically calculating operation by fetching data once at least. CONSTITUTION: This device is provided with a sampling means 3 sampling data in the video screen one-dimensional direction of a video signal outputted from an image pickup element 2, and a one-dimensional Z-transformation means 7 Z-transforming the data of the sampled video signal. Also this device includes a moving means 6 moving an image pickup lens 1 or the element 2 to a focusing position arithmetically calculated by zero point set storing means 81 to 8j storing one or more zero points as a set by every optical transfer function(OTF) obtained by one-dimensional Z-transformation, zero point substituting means 101 to 10j , sum calculating means 111 to 11j , a defocusing amount detecting means 12, and a focusing position calculating means 13.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a focusing control (autofocus) device that automatically focuses an optical system of a still video camera, a silver halide film camera, binoculars, etc. It relates to a method of measuring the distance to an object at an arbitrary position.

<Conventional technology> Conventional autofocus methods include an active method in which a distance measurement signal such as an auxiliary light is emitted onto the subject and the returned signal is used, and the other is an active method in which the video signal itself is used in some way. There is a passive method to do this.

The passive method is often used as a highly accurate method because it uses the subject signal itself, but video cameras and the like have an image sensor (CCD) for capturing images of the camera itself, so the signal obtained from the image sensor is A method is often adopted in which autofocus is performed by using the video signal as it is. Like movie video cameras, still video cameras have a built-in image sensor, so if you directly use the video signal obtained from this, there is no need to install a separate optical unit for autofocus, which is advantageous in terms of cost and accuracy. be.

When the conventional imaging surface autofocus method using video signals used in movie video cameras is applied to still video cameras, etc., the outline is as follows.

That is, the high frequency components contained in the video signal etc. have a maximum level at the in-focus position (best focus position), and as the amount of defocus increases, the high frequency components become smaller.

Taking advantage of this, the imaging lens is scanned once at multiple positions a0, a1, a2, etc. from a close distance to an infinite position every time an image is taken, and the high frequency component f0 contained in the video signal during that time is
is extracted by a band-pass filter and the levels are compared one by one to find a position where the high frequency component is maximum, for example a1, and the lens is moved to that position again. Figure 7 (A), (B), (C
) respectively show the hardware configuration of the conventional example, each scan position of the imaging lens, and the high frequency component level at each scan position.

<Problems to be Solved by the Invention> The conventional autofocus method has several problems as described below.

As mentioned above, the active method has a major problem in that it requires a separate optical unit dedicated to autofocus.

Even in the passive method, the lens must first be moved from a close distance to an infinity position in order to find the in-focus position, which takes time.

In addition, in order to improve detection accuracy, it is possible to narrow the bandwidth of the bandpass filter for extracting high-frequency components, but if the bandwidth is too narrow, depending on the type of subject, it may not include many frequency components in that band and may not be sufficient. This may cause problems such as not being able to obtain output.

The present invention was developed in view of these conventional problems, and it is possible to find an accurate in-focus position by capturing a video signal at least once, without having to scan by moving the lens from a close distance to an infinite position. , and does not have dependence on the type of subject such as a specific frequency component of the subject signal, and does not require a special optical system dedicated to autofocus. shall be. At the same time, it is an object of the present invention to provide a method of measuring an object at an arbitrary position using a video signal without having a light emitting mechanism unlike the active method.

<Means for Solving the Problem> Therefore, as shown in FIG. 1, the focusing control device according to the present invention includes sampling means for sampling data in one-dimensional direction of the video screen of the video signal output from the image sensor. , a one-dimensional Z-transforming means for Z-transforming the data of the sampled video signal, and a response function (OTF) obtained by one-dimensional Z-transforming the point spread function of the imaging lens system corresponding to a plurality of defocus amounts. Zero point set storage means for storing one or more zero points as a set for each OTF, and each value obtained by substituting each zero point of the zero point set for each OTF into the polynomial Z-transformed by the one-dimensional Z-transforming means. a zero point substitution means for computing the absolute value of , a summation computing means for computing the sum of each absolute value obtained by substituting the zero point for each OTF, and a sum calculation means for computing the sum of the absolute values obtained by substituting the zero point for each OTF, and comparing the sum of the absolute values for each OTF, a defocus amount detection means for detecting a defocus amount of the OTF corresponding to the minimum value of , and a focus position calculation means for calculating a relative focus position between the image sensor and the imaging lens based on the detected defocus amount. , a moving means for moving the imaging lens or the imaging element to the calculated focus position.

Further, the sampling means samples a plurality of sets of data in the one-dimensional direction in a direction perpendicular to the one-dimensional direction, and the defocus amount detection means detects a value corresponding to an average value of the sum of the absolute values of the plurality of sets. Compare between OTFs,
It can be configured to detect the defocus amount of the OTF corresponding to the minimum value therein.

Further, the sampling means samples a plurality of sets of data in the one-dimensional direction in a direction perpendicular to the one-dimensional direction, and the defocus amount detecting means compares the sum of the absolute values between OTFs in each set. After selecting the minimum value among the minimum values in each set, the defocus amount of the OTF corresponding to the minimum value among the minimum values in each set may be detected.

Further, the sampling means performs sampling with the imaging lens set at an infinity position or a close position, and the moving means moves the imaging lens or imaging element only in one direction to control the relative focusing position. Good too.

Further, the distance measuring method according to the present invention samples data of a video signal of an object obtained on an image sensor through an imaging lens, performs Z transformation, and applies a polynomial that corresponds to a plurality of defocus amounts to the Z-transformed polynomial. Detecting the current amount of defocus by substituting the zero point and finding the zero point of the polynomial,
The distance from the imaging lens or image sensor to the object is measured based on the detected defocus amount.

<Operation> The sampling means samples one or more sets of video signal data in one-dimensional direction of the video screen output from the image sensor.

The one-dimensional Z conversion means converts the data of the sampled video signal (usually data converted into a digital signal by an AD converter for ease of processing) into Z for each set.
Convert.

Each zero of a plurality of OTFs stored in the zero point set storage means is substituted into the Z-transformed polynomial by the zero point substitution means, and the absolute value of each value obtained by the substitution is determined.

The sum calculation means calculates the sum of the respective absolute values obtained by substituting the zero points for each OTF.

The total sum of these absolute values for each OTF is compared by the defocus amount detection means, and the defocus amount of the OTF corresponding to the minimum value among them is detected. In other words, since the OTF that becomes zero when the zero point is substituted is the current true OTF, the OTF for which the sum of absolute values is the smallest is the OTF that is closest to the truth among the given OTFs, so that OTF The defocus amount indicates the current defocus amount well.

Note that in order to improve the detection accuracy of the defocus amount, more OTFs may be prepared.

When the current defocus amount is detected in this way,
Since the position and focal length of the imaging lens are known, the relative focus position can be calculated by the focus position calculation means.

Then, by moving the imaging lens or the imaging element to the calculated focus position using the moving means, the focus position can be satisfactorily adjusted.

Further, the sampling means samples a plurality of sets of data, and the defocus amount detecting means compares a value corresponding to an average value of the sum of the absolute values in the plurality of sets between OTFs, and corresponds to the minimum value among them. In the configuration configured to detect the defocus amount of the OTF, the influence of noise can be reduced and the detection accuracy can be improved compared to the case where the corresponding OTF is determined using only one set of data.

In this method, reliability is particularly given to the average values of multiple sets. In other words, even if there is an OTF that has a set with the minimum absolute value of the sum, reliability is given to the average value of the plurality of sets or the one with the minimum value.

Similarly, the sampling means samples a plurality of sets of data, and the defocus amount detecting means compares the sum of the absolute values in each set between OTFs, selects the smallest one, and then selects the smallest one. A method configured to detect the defocus amount of the OTF corresponding to the minimum value among the minimum values of the set can similarly reduce the influence of noise and improve detection accuracy, but this method Then, if the absolute value of the sum of even one set is the minimum, the corresponding OTF is trusted.

Further, the sampling means performs sampling with the imaging lens set at an infinite position or a close position, and the moving means moves the imaging lens or image sensor only in one direction to control the focusing position. By doing so, it is possible to reliably set the focus position with one calculation process of data acquisition and one movement. In other words, when the imaging lens is at a position other than the infinity position or the close position, even if the amount of defocus is determined, it is difficult to distinguish whether it is defocused toward the close position or towards infinity. Therefore, the moving direction of the imaging lens cannot be determined.

Furthermore, in the ranging method according to the present invention, data of a video signal of an object obtained on an image sensor through an imaging lens is sampled and Z-transformed, and the Z-transformed polynomial is applied to a plurality of defocus amounts. By substituting the zero point of the polynomial, it is possible to find the zero point of the polynomial as explained in the above-mentioned focus control device, and the current amount of defocus can be detected by this, so imaging is performed based on the detected amount of defocus. The distance from the lens or image sensor to the object can be measured. With this method, there is no need for a special light emitting mechanism like the active method, and distance measurement can be performed with high accuracy only by processing the video signal.

<Example> Prior to describing the example, the theory related to the present invention will be explained below with reference to FIGS. 2 and 3.

In a certain imaging optical system, data y of a video signal sampled from an imaging device such as a CCD is determined by the point spread function of the lens.
-n) is g, object data is u, and noise generated in the image sensor system is n, it is generally expressed as follows {see FIG. 2(A)}.

(2) In the formula, all variables are two-dimensional quantities, and * indicates convolution.

The point spread function g is expressed by the following equation according to optical theory.

Here, if d0 is the distance between the object and the imaging lens, and d1 is the distance between the imaging lens and the imaging element, then if d1 is defocused to the smaller side than the distance when it is at the in-focus position, the above W is as follows. Set as a value that satisfies the expression.

Further, when the distance is defocused to the side larger than the distance when d1 is at the in-focus position, W is set as a value that satisfies the following equation.

Further, the lens window function P indicates the lens aperture,
When the imaging lens has no aberration, it is a constant value at any point within the lens aperture, and is 0 at other points.

Now, if we ignore the noise term n in formula (■) for simplification, it becomes as follows, and it can be seen that it is the point spread function g that degrades the image due to convolution, and from formula (■), the point spread function g It is clear that g is only influenced by W. Therefore, if the value of W is determined, i.e., in the formula ■ or ■', the distance d1 between the imaging lens and the imaging element and the focal length f of the imaging lens are known, so if the distance d0 between the object and the imaging lens is determined, the point image spread function g
will be determined uniquely.

From a reverse perspective, this means that if the point spread function g at the current imaging lens position can be specified, the object-imaging lens distance d0 can be known.

As shown in FIG. 2(B), if the imaging lens is at infinity position A when the video signal data is first sampled, then if the distance d0 between the object and the imaging lens is known, the distance between the imaging lens and the imaging element is Since d1 and the lens focal position f are known, the following equation holds true.

Thereby, the lens movement amount Δd for obtaining the in-focus position (B in the figure) is determined.

Next, a method for specifying the point spread function g at the current lens position will be described.

First, the one-dimensional discrete Fourier transform Gk of the point spread function g
is expressed as the following equation. Note that Gk is a response function (optical transfer function
n) and abbreviated as OTF. Its role in an optical system is similar to that of a transfer function in an electrical transmission line such as an amplifier.

Here, gi (i=0, 1...M-1) is a sample value of the point spread function g, and M is the number of samples.

OTFGk is expressed as (
FIG. 3 shows curves drawn for various defocus amounts l/W (k≧0). ■From the formula, when l/W=0, l/
It can be seen from the figure that d0+l/d1=l/f, which is the in-focus position.

If we set ■=exp{-j(2π/M)k} in equation (2) (|■|=l), the following equation holds true.

■As you can see from the formula, the one-dimensional discrete Fourier transform is ■−
It takes the form of a polynomial of 1, therefore, Gk can be expressed as the following equation by factorizing it.

Here, ■i (i=1, 2, . . . M-1) is a zero point of a polynomial with ■-1 as a variable. That is, when ■-1=■i (or ■=l/■i), Gk=0. Even if the zero point of Gk at a certain defocus amount l/W is substituted into -1 of Gk at another defocus amount l/W, it will not become zero. Therefore, when the zero point of each Gk0 for various defocus amounts l/W is investigated and the zero point of each Gk0 for a certain defocus amount l/W0 is substituted into ■-1 of Gk whose defocus amount l/W is unknown. Assuming that Gk=0, it turns out that the defocus amount l/W of this OTFGk is l/W0. In other words, Gk can be specified. However, in Fig. 3, the curve Gk where the defocus amount l/W is smaller than a certain value is 0.
There is no point where In other words, there is no zero point that satisfies |■i|=1. Therefore, Gk cannot be specified in the above case using the one-dimensional discrete Fourier transform.

Therefore, in order to be able to specifically evaluate the OTF even in the above case, we use Z=γexp(jω) with amplitude γ instead of exp{j(2π/M)k} in equation (2) to calculate the one-dimensional point spread function g. Taking Z-transformation gives the following equation.

Using this polynomial G(Z), it is possible to evaluate G(Z) at any point on the complex plane, not only on the unit circumference of γ=1.

■Take the Z transformation of both sides of the equation and express it as follows.

Y(Z)=U(Z)×G(Z)−N(Z) ■Here, Y
(Z), U(Z), G(Z) and N(Z) respectively represent Z transformations of y, u, g and n in formula (2). If we ignore the noise term N(Z), then Zi becomes U(Z) or G(Z)
If it is the zero point of , then Y(Z)=0. Therefore, if the zero point of G0(Z) obtained by Z-transforming the point spread function g corresponding to a certain amount of defocus l/W0 is substituted into Y(Z), then Y(Z)=0, G(Z) at that time
) can be identified as G0(Z) (generally G(Z)
U(Z), which is the zero point of and the Z-transformed value of the sampling data
The zeros of the two do not match).

Therefore, for the imaging lens of the camera used, the point spread function g for different defocus amounts l/W is determined in advance.
Find a formula for OTFGk (Gk1, Gk2...Gk) corresponding to each defocus amount l/W from each point spread function g.
j) by measurement or theoretical calculation, and further calculate each OTF.
Zero point set in Gk (Z0n1, Z0n2...Z0n
i; n=1, 2...J) are calculated in advance.

Then, by substituting the zero point set of each OTFGk into Y (Z) obtained by Z transformation from the sample data of the image sensor output, and finding the OTF for which the sum of their absolute values is the smallest, that OTF becomes the current OTF. It will be equivalent to .

In this way, the OTF is specified, and therefore the point spread function g is specified, so the defocus amount l/W is also determined, and the lens movement amount Δd can be determined.

Further, once the defocus amount l/W is determined, and before the lens movement amount Δd is determined, the distance d0 between the object and the imaging lens is determined using the formula (1) or (2), as described above. In other words, it is possible to measure the distance from the imaging lens or image sensor to an object located at an arbitrary position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a camera focusing control device according to the present invention will be described below with reference to the drawings.

In FIG. 4 showing the configuration of the first embodiment, the initial position of the imaging lens 1 is set to a close distance position during autofocus operation. The light entering from the imaging lens 1 is CC
The image sensor circuit 2 including a D (imaging device) 2A, a signal amplifier 2B, etc. performs photoelectric conversion and amplification processing, and outputs it as a video signal.

The video signal is sampled by a sampling circuit 3 serving as a sampling means, in which data for pixels necessary for autofocus (the video portion to be focused) is sampled, and is converted into a digital signal by an A/D converter 4. ,
K rows of data (see FIG. 5) are temporarily stored in the row buffer memory 5, with n data per row in the one-dimensional direction of the video screen.

On the other hand, OTFGk zero point sets (Z0p1, Z0p2,...
Z0pi; p=1, 2...J) are J registers 81 to 8
Each is memorized in j. That is, these registers 81~
8j corresponds to the zero point set storage means.

Hereinafter, the arithmetic processing executed by each arithmetic unit of the microcomputer will be explained in order.

In the one-dimensional Z conversion unit 7, first, the sample image data g11 of the first row held in the row buffer memory 5 is
~g1n is Z-transformed to obtain Y1(Z) consisting of a polynomial of Z-1 as shown below.

Zero point assignment units 91 to 9 corresponding to each register 81 to 8j
In j, Y1(Z) input from the one-dimensional Z transformation unit 9, respectively.
The absolute value calculation unit 1 sequentially substitutes each zero point Z0p1 to Z0pi of the zero point set stored in the register 8p corresponding to
For 01 to 10j, the absolute value of each substituted value |Y1(Z
0p1)|~|Y1(Z0pi)| That is, these zero point substitution units 91 to 9j and absolute value calculation units 101 to 10
j corresponds to the zero point substitution means.

Absolute value determined as above | Y1 (Z0pi)
|~|Y1(Z0p1)| is sequentially the corresponding addition unit 11
p (p = 1 to j・ is input and added. Then, when the above calculation process is completed for all the zero points of one set, the same calculation process is repeated for the sample image data in the second row. The calculation result is added to the addition value in the first row in the addition section 11p.The addition sections 111 to 11j correspond to the summation calculation means.

The above calculation process |Yr(
Z0pn)| are compared in the comparison unit 12, and the OTF corresponding to the minimum value among them is specified as the OTF corresponding to the current defocus amount l/W.

This comparison section 12 corresponds to defocus amount detection means.

As a result, the current defocus amount l/W has been detected, so the focus position calculation unit 13 calculates the focus position, that is, the lens movement amount Δd.

First, in this embodiment, since the imaging lens 1 is set at a close distance, the object U-
The distance d0 between the imaging lenses 1 is determined. Next, this value is found as the root of the quadratic equation by substituting it into the equation (2). In the case of this embodiment, two roots, positive and negative, are found, and the negative value is selected. The reason is as described above. Note that if the defocus amount l/W is known, the lens movement amount Δd can be obtained as described above, so the lens movement amount Δd obtained in advance for each of a plurality of defocus amounts l/W is
The processing speed can be increased by storing the data in a ROM map table and searching for it.

A signal corresponding to the lens movement amount Δd thus obtained is output to the lens drive circuit 6 as a moving means. As a result, the imaging lens 1 is moved away from the imaging element 2 by Δd, and the focal position is adjusted.

With such a configuration, the amount of movement Δd can be determined by arithmetic operations based on data acquisition once, and the focus position can be adjusted in a short time with only one movement.

Furthermore, since there is no dependence on the type of subject such as the frequency component of the subject, good accuracy can always be obtained, and there is no need for a special optical system dedicated to autofocus, which is advantageous in terms of cost.

In the previous embodiment, the OTF with the minimum sum of |Yr(Z0pn)| for each row (equivalent to the average) was selected, but next, the OTF with the minimum value among all |Yr(Z0pn)|
An example of selecting F will be described based on FIG.

That is, the difference from the first embodiment is that each row is selected in the first comparison section 12A every time the addition section 111 is finished.

)|, (r=1 to k), the second comparison unit 12B selects the OTF having the smallest value among the minimum values for the K rows as the current defocus amount l/W. O corresponding to
Specify as TF. Note that in this embodiment, the first comparing section 12
A and the second comparison section 12B correspond to defocus amount detection means.

Focusing by moving the lens by the amount of movement Δd calculated based on the defocus amount l/W of the specified OTF is the same as in the first embodiment, and therefore the effect is also the same, but as described above. Regarding the identification of OTF, the first
The difference is that in the second embodiment, reliability is placed on the average value of each row in the sum of absolute values, whereas in the second embodiment, reliability is placed on the minimum sum of absolute values in even one row.

In addition, although the image pickup lens is set at a close position during autofocus operation, the function is exactly the same even if it is set at an infinity position. It has the advantage of being compact and portable by retracting the imaging lens under normal conditions.)
In this case, formula (2) is used to calculate the amount of lens movement, and the imaging lens is moved in a direction closer to the imaging element. In addition, as mentioned above, in order to be able to perform focusing control without setting the imaging lens at an infinity position or a close position, the imaging lens is set twice, once at an arbitrary initial position and once at a slightly moved position. A method may be adopted in which the amount of defocus is detected, the amount and direction of lens movement are determined, and the movement is controlled. Furthermore, instead of moving the imaging lens, a method may be adopted in which the imaging element is moved. In that case, the moving amount Δd of the image sensor, with the direction of moving the image sensor away from the imaging lens as the positive direction, is determined by the following equation instead of the equation (2). It should be noted that when the formula (2) is used, Δd is a positive value, and when the formula (2) is used, Δd is a negative value.

In addition, in the above embodiment, since the sampling data of multiple rows (sets) are Z-transformed and compared, the influence of noise on the video signal can be reduced by averaging, but if the influence of noise is small, It is also possible to perform processing using only one row of data. Further, if a sequence is performed in which data is sequentially integrated into each Z-n term of the polynomial each time data is sampled one by one, a temporary storage means such as the row buffer memory 5 is not required.

However, since this method increases the number of calculation steps, it is suitable for devices with high-speed processing capabilities.

<Effects of the Invention> As explained above, according to the present invention, the amount of movement of the imaging lens to the in-focus position can be determined by arithmetic operations based on at least one data acquisition, and the amount of movement of the imaging lens to the in-focus position can be determined in a short time by at least one movement. can be optimally focused.

Furthermore, since there is no dependence on the type of subject such as the frequency component of the subject, good accuracy can always be obtained, and there is no need for a special optical system dedicated to autofocus, which is advantageous in terms of cost.

In addition, multiple sets of data are sampled by the sampling means, and the values corresponding to the average values of the multiple sets of the sums of the absolute values of the Z conversion formula in which zero points are substituted are compared for each OTF, and the value corresponding to the minimum value among them is compared. After detecting the defocus amount of the OTF or comparing the values in each set of absolute value sums for each OTF and selecting the smallest one, the OTF corresponding to the minimum value among the minimum values of each set is detected. If the defocus amount is detected, the influence of noise can be reduced and detection accuracy can be improved.

In addition, if sampling is performed with the imaging lens set at an infinity position or a close position, and the moving means moves the imaging lens or image sensor only in one direction to control the focusing position, it is necessary to perform sampling once. You can reliably set the focus position by moving the lens.

Further, in the distance measuring method according to the present invention, there is no need for a special light emitting mechanism such as an active method, and distance measurement can be performed with high accuracy only by processing the video signal.

Note that the present invention can be applied to telescopes and the like in addition to cameras.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration and functions of the present invention, Figures 2 (A) and (B) are diagrams showing the positional relationship of each part to explain the theory of the present invention, and Figure 3 is the amount of defocus. 4 is a diagram showing the configuration of the first embodiment of the present invention, FIG. 5 is a diagram showing the position of sampled data on the screen, and FIG. 6 is a diagram showing the characteristics of each OTF with different characteristics. 7A is a diagram showing the configuration of the second embodiment of the present invention, FIG. 7A is a diagram showing the hardware configuration of the conventional example, and FIG. 7B is a diagram showing each scan position of the imaging lens. Figure (C) is a diagram showing the high frequency component level at each scan position. 1...Imaging lens 2A...CCD 3...Sampling circuit 6...Lens drive circuit 7...One-dimensional Z conversion section 8
1 to 8j...Registers 91 to 9j...Zero point assignment units 101 to 1
0j...Absolute value calculation units 111 to 11j, 111' to 11j
'...Addition section 12...Comparison section 12A...First comparison section 12B...Second comparison section 13...Focus position calculation section Patent applicant Konica Corporation Patent applicant Edward R. Dowsky Jr. Representative Patent Attorney Fujio Sasashima

Claims (5)

[Claims] 1. Sampling means for sampling data in a one-dimensional direction of a video screen of a video signal output from an image sensor, one-dimensional Z-conversion means for Z-transforming data of the sampled video signal, and a plurality of defocusing devices. zero point set storage means for storing a set of one or more zero points for each response function (OTF) obtained by one-dimensional Z-transforming a point spread function of an imaging lens system corresponding to the amount; and the one-dimensional Z-transforming means. a zero point substitution means for substituting each zero point of the zero point set for each OTF into the Z-transformed polynomial and calculating the absolute value of each value obtained by the substitution; a sum calculation means for calculating the sum of absolute values; a defocus amount detection means for comparing the sum of the absolute values for each OTF and detecting the defocus amount of the OTF corresponding to the minimum value of the sum; The device includes a focus position calculation means for calculating a relative focus position between the image pickup element and the image pickup lens based on the amount of defocus, and a movement means for moving the image pickup lens or the image pickup element to the calculated focus position. A focusing control device characterized by: 2. The sampling means samples a plurality of sets of data in the one-dimensional direction in a direction orthogonal to the one-dimensional direction, and the defocus amount detection means corresponds to an average value of the sum of the absolute values of the plurality of sets. 2. The focusing control device according to claim 1, wherein the OTFs are compared with each other, and the defocus amount of the OTF corresponding to the minimum value among the OTFs is detected. 3. The sampling means samples a plurality of sets of data in the one-dimensional direction in a direction orthogonal to the one-dimensional direction, and the defocus amount detecting means calculates the sum of the absolute values between the OTFs in each set. 2. The focusing control device according to claim 1, wherein the OTF defocus amount corresponding to the minimum value among the minimum values in each set is detected after the comparison is made and the minimum value is selected. 4. The sampling means performs sampling with the imaging lens set at an infinity position or a close position, and the moving means moves the imaging lens or imaging element in only one direction to control the focusing position. A focusing control device according to any one of claims 1 to 3. 5. Sampling and Z-transforming data of a video signal of an object obtained on an image sensor through an imaging lens;
The current defocus amount is detected by substituting zero points corresponding to a plurality of defocus amounts into the Z-transformed polynomial and finding the zero point of the polynomial, and based on the detected defocus amount, the imaging lens or A distance measuring method for measuring the distance from an image sensor to the object.