JP2002267923A - Focusing method of photographic lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focusing method of photographic lens capable of taking measures based on actual photographing of a general subject having high accuracy and realizing the shortening of the adjusting time. SOLUTION: In the focusing method of photographic lens, the chart images of a center chart part 5a and peripheral chart parts 5b to 5e on the optical axis of a chart unit 5 are converted into an image pickup signal by an image pickup device 13, and fetched in a CPU 21. The MTF value of the chart image of each chart part is arithmetically calculated by an MTF arithmetic operation part 22, and the focus position to each chart part is detected by a focus position arithmetic operation part 23 based on the MTF value. By arithmetically averaging the focus positions of the center chart part and the peripheral chart parts, the middle focus position of the photographic lens 64 is obtained and written in the EEPROM 65 of the camera 6 as focus lens extending amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus adjustment method for adjusting the focus of a photographic lens.

[0002]

2. Description of the Related Art Conventionally, as a method of detecting the focus position of a photographing lens in a camera and adjusting the focus of the photographing lens, focus adjustment is performed by visually observing a chart image of a chart set at a predetermined position using an optical bench. There was a way to do it. There has also been a method of adjusting a focus position by measuring a chart light amount by a photoelectric collimator using a photoelectric collimator.

[0003]

However, in the method of performing focus adjustment using the above-described optical bench, since the sensory test is used, the variation between operators is large.
It was difficult to quantify the contrast and the number of resolutions, and accurate adjustment was not possible. In addition, the adjustment work time was long, the fatigue of the measurer was great, and the work efficiency was poor.

On the other hand, in the method of performing focus adjustment using a photoelectric collimator, there is a problem in that it is not possible to properly cope with a real photograph of a general subject because the amount of light is evaluated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and corresponds to an optimum focus position in actual photographing for photographing a general subject, has high accuracy, and can shorten an adjustment time. An object of the present invention is to provide a method for adjusting the focus of a lens.

[0006]

According to a first aspect of the present invention, there is provided a photographing lens focus adjusting method, comprising: an image pickup means for picking up a chart image obtained by a photographing lens for picking up a chart at a predetermined position; MTF of imaging from means
MTF calculating means for calculating the focus position of the photographing lens with respect to the chart at the predetermined position.
And a photographing lens position determining means for determining the MTF of the imaging at each of the plurality of points on the optical axis by the MTF calculating means.
The focus position of the photographing lens is determined based on the output obtained by the MTF calculating means.

According to a second aspect of the present invention, a focus adjustment method for a photographing lens is provided by a photographing lens for photographing a chart at a predetermined position on an optical axis and a plurality of charts at a predetermined position off the optical axis. Imaging means for imaging a chart image, and MTF for calculating MTF for imaging from the imaging means
Calculating means; and a photographic lens position determining means for determining a focus position of the photographic lens with respect to a chart at a predetermined position on the optical axis and a plurality of charts at a predetermined position off the optical axis by an output obtained by the MTF. And calculating the MTF of each image by the MTF calculation means at each of the plurality of points on the optical axis.
The focus position of the photographing lens is determined based on the average value of the outputs obtained by the F calculating means.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a focus adjustment device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the focus adjustment device. Note that, in the imaging unit (described later) that configures the focus adjustment device 10 of the present embodiment, the imaging optical axis Oc and the imaging optical axis Od
A direction parallel to the Z direction is defined as a Z direction, a direction orthogonal to the Z direction, a horizontal direction is defined as an X direction, and a vertical direction is defined as a Y direction.

The focus adjustment apparatus 10 of the present embodiment has an MTF (Modulation Transfer Func) that can correspond to a real image as a scale of evaluation of a captured image of the camera 6 as an object to be adjusted.
option) is measured at a plurality of points on the optical axis Oc and the camera 6
This is a device for adjusting the focus position. In the camera 6, the overall focus position usually changes due to dimensional errors and assembly errors of the components of the lens barrel, or the RDN of the single lens, lens thickness, air gap, eccentricity, and the like. That is, the peak position of the MTF value changes. The change of the focus position is detected by the focus adjusting device 10 in the MTF.
The focus is adjusted by detecting the value based on the value measurement and recording the focus position data in the camera 6.

In the focus adjustment apparatus 10, the focus state of the photographed image is evaluated by using the chart unit 5 based on the MTF value on the photographing lens optical axis Oc at the center of the chart screen and the MTF value around the chart screen. Is done. Then, the optimum focus position of the entire screen is obtained in consideration of the amount of defocus at each point on or around the optical axis Oc, and the information is recorded on the camera side.

As shown in FIGS. 1 and 2, the focus adjustment device 10 includes an imaging unit 1, a focus adjustment control unit 2, a keyboard 3, a monitor 4, and a chart unit 5.
The camera 6 serving as the adjusted unit is provided with an imaging main body 18 of the imaging unit 1.
Mounted on top.

As shown in FIGS. 1 and 2, the image pickup section 1 includes an image pickup head 11, which is an image pickup means, an image pickup control section 14, a head drive section 15, and an image pickup section main body 18.

The image pickup head 11 includes an image pickup lens 12 having an optical axis Od, and an image pickup device 13 having a CCD as an image pickup device and an image pickup processing circuit. CC above
In D, the chart image captured by the photographing lens 64 of the camera 6 is formed on the image plane of the CCD via the imaging lens 12, and is converted into an electric signal by the CCD. The imaging processing circuit processes the imaging output signal of the CCD and outputs image data to the CPU 21 side.

The imaging control unit 14 controls the C of the imaging device 13
It drives and controls the CD and the imaging processing circuit.

The head drive unit 15 includes an imaging unit main body 18.
XY axis drive stage (XY axis drive section)
16 and a Z-axis drive stage (Z-axis drive unit) 17. The imaging head 11 is mounted on the XY-axis driving stage 16.
Drive in the direction. The XY-axis driving stage 16 is attached to the Z-axis driving stage 17,
The Y-axis drive stage 16 is driven in the Z direction, and the imaging head 11 is driven in the Z direction.

The focus adjustment control section 2 comprises a CPU 21 for controlling the inside of the adjustment control section and the image pickup section 1, and a RAM section 29 for storing arithmetic expression information and the like.

The CPU 21 includes an imaging unit 1 and
In addition to the control unit of the camera 6, an MTF calculation unit 22 as MTF calculation means and a focus position calculation unit 23 as photographic lens position determination means are incorporated. MTF calculator 22
Captures the chart image data output from the imaging device 13 and calculates the MTF value of the chart image by calculation. The focus position calculator 23 calculates the focus position of the camera 6 based on the MTF value output from the MTF calculator 22 and calculates the focus position of the camera 6.
The focus position data is written to the CPU 65 via the CPU 61.

The keyboard 3 is used to make various settings when executing the focus adjustment process, and the monitor 4 is used to check the operation state during the focus adjustment process.

The chart unit 5 is provided with a standard photographing distance L1 which is a subject distance applied at the time of normal camera photographing.
For example, a test chart on a shooting image frame arranged at a position separated by 3 m, which is a center chart portion 5a located on the shooting lens optical axis Oc of the camera 6 and a position near the shooting image frame on the XY plane It has a peripheral chart section 5b in the first quadrant, a peripheral chart section 5c in the second quadrant, a peripheral chart section 5d in the third quadrant, and a peripheral chart section 5e in the fourth quadrant. The center chart section 5a has a predetermined pitch (spatial frequency f0 = 10 lines / m) in the X and Y directions.
m), which is composed of a vertical pattern and a horizontal pattern. Each of the peripheral chart portions has a pattern of a predetermined pitch (spatial frequency f0 = 10 lines / mm) in the radial direction (S direction) and the circumferential direction (M direction). The spatial frequency f0 = 10 lines / mm is applied to the focus adjustment because the spatial frequency f0 is higher than that described later.
This is because, in comparison with 1, f2, etc., the quality of the shooting screen at the time of actual shooting is better.

The camera 6 includes a photographing lens 64 having an optical axis Oc, a CPU 61 for controlling the entire camera, a lens driving unit 63 for driving the photographing lens 64 forward and backward, and a CPU 6.
A drive control unit 62 that controls the lens drive unit 63 under the control of 1 and an EEPROM 65 that stores data for photographing such as focus position data of the photographing lens 64. At the time of the focus adjustment process, the image pickup unit 12 is mounted on the image pickup unit main body 18 with an optical axis Oc of the image pickup lens 64 kept parallel to an image pickup optical axis Od of the image pickup lens 12 described later.

Next, a description will be given of processing operations such as measurement of the MTF value of the camera 6 by the focus adjustment device 10 having the above-described configuration. The camera 6 and the head driving unit 15 are set to the MTF value measurement state around the optical axis O or around the screen. That is, the camera 6 is attached to the imaging section main body 18 of the imaging section 1 with the rear lid 66 opened. At this time, it is confirmed that the optical axis Oc of the photographing lens 64 of the camera 6 coincides with the center of the central chart portion 5a of the chart unit 5. Further, the photographing lens 64 is extended to a designed focusing position with respect to the standard photographing distance L1. In the above-mentioned camera set state, the position of the aperture surface (film surface) 67 is a virtual imaging position in the chart design.

In order to measure the MTF value at the center of the optical axis O, the XY axis stage 16 of the head driving unit 15 is driven to move the imaging head 11 (imaging lens 12) to the center of the optical axis Oc of the aperture 67 of the camera 6. The optical axis Od is matched.

In order to measure the peripheral MTF value, the above X
By driving the Y-axis stage 16, the imaging head 11 is moved to the peripheral pattern image position of any one of the first to fourth quadrants to be measured on the aperture surface 67 of the camera 6.
The optical axis Od of the (imaging lens 12) is matched.

At the time of measuring the MTF value at or around the center of the optical axis O, the imaging head 11 is moved by the Z-axis driving stage 17 to the Z-axis.
By driving in the direction, the focal point of the imaging lens 12 is moved in the front-back direction of the aperture surface 67, and the MTF value of the chart image is measured. At that time, the imaging head 11
When the focal point of the (imaging lens 12) is on the aperture surface 67, a shift position Zd = 0, which is the reference shift amount in the Z direction (defocus amount), is set on the rear side (back side) of the aperture surface 67. The Z-direction shift position Zd is defined as + side, and the Z-direction shift position Zd when located on the front side (subject side) is defined as-side.

When the imaging head 11 is shifted in the Z direction
, The image of the center chart 5a or the image of the peripheral chart (in this case, the peripheral chart 5e in the fourth quadrant) captured by the photographing lens 64 is formed on the image forming surface of the CCD, and is formed on the CCD. Is converted into an electrical imaging signal. The imaging signal of the chart image is transmitted to the CP via the imaging device 13.
It is output to the U21 side. Then, the MTF calculation unit 22 calculates the MTF value of the chart image.

FIG. 3 is a diagram showing a change in the measured value of the MTF value for the image of the central chart portion 5a with respect to the Z position. This diagram shows a shift position Zd = 0 on the aperture 67.
5 shows a change in the MTF value of the chart image at a deviation position Zd in the Z direction (optical axis direction) from the position. In the figure, the curves of f0, f1, and f2 in the center chart section are respectively represented by spatial frequencies f0 = 10 lines / mm and f1 = 20 lines / chart of the chart.
mm, f2 = 30 lines / mm The change of the MTF value of the vertical or horizontal pattern.

In the focus adjustment apparatus 10 of the present embodiment, for example, the spatial frequency f0 of the vertical chart pattern most corresponding to normal subject photographing is f0 = 10 /
The MTF data of the mm curve (solid line) is applied to focus adjustment. Further, an average value of data of the vertical pattern and the horizontal pattern may be adopted as the MTF value.

In the measurement results shown in FIG. 3, the MTF value has a peak at Zd = 0.00 mm with respect to the image of the central chart portion 5a (peak point P0). That is, this indicates that the focus position is on the surface of the aperture 67. The calculation of the peak point is performed by the focus position calculation unit 23 of the CPU 21.
Done in

Next, when measuring the MFT value around the photographic image frame, for example, when measuring the peripheral MFT value in the fourth quadrant, the peripheral chart section 5e in the fourth quadrant of the chart unit 5 on the aperture section 67 is used. The XY-axis stage 16 of the head drive unit 15 is driven so that the optical axis Od of the imaging lens 12 of the imaging head 11 coincides with the image position, and M
The MTF value is measured while driving the imaging head 11 in the Z direction in the same manner as the TF value measurement.

FIG. 4 is a diagram showing a change in the measured value of the MTF value with respect to the image of the peripheral chart section 5e. In the figure, the curves of f0, f1, and f2 in the peripheral chart section are as follows:
The spatial frequency of the chart is f0 = 10 lines / mm, f
MT when 1 = 20 / mm, f2 = 30 / mm
The change of the F value is shown. The solid line shows the MTF value of the S direction pattern, and the broken line shows the MTF value of the M direction pattern. In the focus adjustment device 10 of the present embodiment, the change in the MTF value of the curve (solid line) of f0 when the spatial frequency f0 of the S-direction chart pattern is 10 lines / mm is applied.

MT of the image of the peripheral chart section 5e in FIG.
The F value peaks at the deviation position Zd = + 0.20 mm (peak point P4). That is, the peak position P4, which is 0.20 mm rearward from the surface of the aperture 67, is the focus position of the peripheral chart 5e in the fourth quadrant. The calculation of the peak point is performed by the focus position calculation unit 23 of the CPU 21.

When the focus adjustment is actually performed by the focus adjustment device 10, the change of the MTF value with respect to each shift position Zd around the aperture surface of the peripheral pattern of the first to third quadrants other than the fourth quadrant is also measured. . According to the measurement result, the peak position P1 indicating another focus position with respect to the peripheral pattern
, P2, P3.

Thereafter, each peak position (focus position) P0, P1, P2, P3,
The focus position calculating unit 23 in the CPU 21 calculates the focus position Pm of the entire image frame of the photographing lens 64 based on the shift position Zd data of P4 by a predetermined average calculation method.
Ask for. The data of the focus position Pm is used as the data of the focus extension amount of the camera 6 (providing a conjugate plane with respect to the standard subject distance L1).
1 and written to the EEPROM 65.

Next, the focus adjustment operation by the focus adjustment device 10 will be described with reference to the flowchart of FIG.
This will be specifically described with reference to FIG. FIG. 6 is a diagram showing an example of the measurement result of the MTF value for each chart.
6A is a central chart 5a, FIG. 6B is a peripheral chart 5b in the first quadrant, FIG. 6C is a peripheral chart 5c in the second quadrant, and FIG. 6D is a peripheral chart in the third quadrant. Chart 5d
FIG. 6E shows a change in the MTF value for the peripheral chart 5e in the fourth quadrant. FIG. 7 is a diagram showing each focus position image plane based on the MTF value measurement result.

When performing focus adjustment, first, the focus adjustment device 10, the chart unit 5, and the camera 6 are set to the MTF value measurement state described above. That is, the camera 6 is set on the imaging unit main body 18 and the optical axis O of the photographing lens 64 is set.
c and the center of the center chart portion 5a of the chart unit 5 are matched. Further, the photographing lens 6 of the camera 6 is extended to the designed focusing position with respect to the standard photographing distance L1, and the focus adjustment processing of FIG. 5 is started.

In step S1, the optical axis Od of the imaging head 11 is moved by the XY-axis driving stage 16 to the optical axis Oc.
And the chart image of the central chart section 5a can be picked up. While the imaging head 11 is moved in the Z direction by the Z-axis drive stage 17, each shift position (shift amount) Zd of the MTF value of the chart image at the center of the optical axis O (center chart portion 5e) of the chart unit 5 shown in FIG. Is measured (see FIG. 6A).

In step S2, the XY-axis driving stage 16 is driven so that the optical axis Od of the imaging head 11 is sequentially matched with the image forming positions of the peripheral chart portions 5b, 5c, 5d, 5e in the first to fourth quadrants. Each of the peripheral chart images is set to a state in which it can be captured. By driving the imaging head 11 in the Z direction by the Z-axis drive stage 17, the change of the MTF values of the peripheral chart images in the first to fourth quadrants with respect to each shift position (shift amount) Zd is measured (FIG. 6 ( B) ~
(E)).

In step S3, step S1
The shift position Zd (P0) of the focus position, which is the optical axis image plane position that gives the peak point P0 of the MTF value at the center of the optical axis O measured at
) Is calculated by the focus position calculator 23. For example, when the measurement result of 6 (A) is obtained, the shift position Zd (P0) of the optical axis center image plane that gives the MTF value peak point P0 =
0.00 mm is required. That is, the MTF value peak point P0 coincides with Zd = 0. FIG. 7 shows an image plane 71 including the position of the peak point P0 and a shift amount Zd (P0) that gives the point P0. If the taking lens 64 is extended so that the image forming position of the taking lens 64 coincides with the shift position Zd (P0), at least the optical axis O
You can shoot in focus on the center subject.

In step S4, step S2
Points P1 to P4 of the peripheral MTF value in each quadrant of the screen measured in
Each shift position Zd of the image plane position (focus position) giving P4
Is obtained by the focus position calculation unit 23. For example, when the measurement results of FIGS. 6B to 6E are obtained, the shift position that gives the peripheral MTF value peak point P1 in the first quadrant is Z
d (P1) =-0.30 mm. Around the second quadrant M
The shift position giving the TF value peak point P2 is Zd (P2)
= + 0.20 mm. The shift position giving the peripheral MTF value peak point P3 in the third quadrant is Zd (P3) = + 0.1
0 mm. The shift position giving the peripheral MTF value peak point P4 in the fourth quadrant is Zd (P4) = + 0.20
mm. Therefore, the focus position calculation unit 23 calculates the shift position Zd (P1 / 4) that gives the average image plane position (peripheral average focus position) that is in average focus on the entire periphery by arithmetic arithmetic averaging. That is, Zd (P1 / 4) = {Zd
(P1) + Zd (P2) + Zd (P3) + Zd (P4)} / 4 ...
Determined by (1).

By substituting each shift position data shown in FIG. 6 into the above equation (1), the peripheral average image plane shift position Zd (P1 / 4
) = + 0.05 mm. FIG. 7 shows the positions of the peak points P1, P2, P3, and P4 in the Z direction, the peripheral average image plane deviation position Zd (P1 / 4), and the deviation position Zd.
An image plane 72 including (P1 / 4) is shown. If the photographing lens 64 is extended to a position corresponding to the shift position Zd (P1 / 4), it is possible to perform photographing that is at least focused on a subject around the screen on average.

In step S5, the deviation position (displacement amount) Zd (P1 / 4) of the peripheral average image plane and the deviation position (displacement amount) Zd (P0) of the optical axis center image plane are calculated by arithmetic mean. A shift position (shift amount) Zd (Pm) that gives an intermediate position (focus adjustment point) is calculated. That is, Zd (Pm) = {Zd (P1 / 4) + Zd (P0)} / 2 (2)

In the equation (2), the shift position Zd (P1 / 4) =
+0.05 mm and shift position Zd (P0) = 0.00 mm
Is substituted, the shift position Zd (Pm) = + 0.025 m
m is obtained. The above calculation is performed by the focus position calculation unit 2
3 is performed. FIG. 7 shows the shift position Zd (Pm).
And the image plane 71 including the shift position Zd (Pm).

In step S6, step S5
The shift position Zd (Pm) data which gives the intermediate position (focus adjustment position) obtained in the step (3) is taken as the focus extension amount data of the photographing lens 64 corresponding to the film surface position.
And writes it to the EEPROM 65.

Thereafter, the camera 6 is detached from the image pickup unit main body 18 of the focus adjustment device 10, and the focus adjustment processing ends.

In the camera 6 which has performed the focus adjustment described above, at least when the subject is at the standard distance L1,
By focusing the taking lens 64 based on the lens extension amount data written in the EEPROM 65, it is possible to take a picture with the best focus state on the image around the optical axis O and the periphery of the screen.

The focus adjustment device 10 of the present embodiment described above.
According to the method described above, an image pickup signal of a chart image at the center of the optical axis and the periphery thereof is taken in while moving the image pickup head 11 in the optical axis direction, and a focus position is automatically obtained by a change in the MTF value based on the chart image. From applying,
It is possible to adjust the focus of a photographic lens, which is compatible with a real photograph of a general subject, has high accuracy, and can reduce the adjustment time.

In the focus adjustment device 10 of the above embodiment, the shift position Zd (Pm) giving one kind of intermediate position (focus adjustment position) is written in the EEPROM 65. However, the present invention is not limited to this. Is calculated according to the characteristic of each of the focus adjustment deviation positions to obtain the EEPR
By writing the data in the OM 65, it is possible to correspond to a photographing lens of various specifications.

For example, focus adjustment position data Zd (P0) based only on the MTF value at the center of the optical axis O is separately written in the EEPROM 65 as the shift position Zd (Pm) 'of the focus position with respect to the portrait taking lens which emphasizes the center. In this case, a preferable portrait photographing can be performed. In addition, when calculating a shift position that is a focus adjustment position with respect to the center-oriented portrait shooting lens,
The shift position Zd of the intermediate position (focus adjustment position) obtained by multiplying the peripheral shift position Zd (P1 / 4) by a predetermined ratio so as to emphasize the shift position Zd (P0) side of the optical axis center.
If (Pm) "is separately written in the EEPROM 65, a more practical portrait photographing can be performed.

Since the macro lens often shoots a fine subject, the spatial frequency is increased, and the above-mentioned f1 = 20 lines / mm or f2 = 30 lines / mm.
If a focus position based on the MTF value is obtained by applying a chart adopting the formula (1) and separately written into the EEPROM 65, good macro photography can be performed.

Based on the above-described embodiment of the present invention, (1) an image pickup means for picking up a chart image obtained by a photographing lens for picking up a chart at a predetermined position, and calculating an MTF of the image picked up by the image pickup means A focus adjustment device for a photographing lens, comprising: an MTF calculating unit that calculates the focus position of the photographing lens with respect to the chart at the predetermined position based on an output obtained by the MTF. Can be suggested.

(2) Image pickup means for picking up a chart image obtained by a photographing lens for picking up a plurality of charts at predetermined positions, MTF calculating means for calculating the MTF of the image picked up by the image pickup means, and the predetermined position The focus position of the taking lens with respect to a plurality of charts
And a photographing lens position determining unit that determines the photographing lens position based on the output obtained by F.

(3) The above (1), wherein the imaging means is movable in the optical axis direction.
The photographing lens focus adjusting device according to the above (2) can be proposed.

(4) imaging means for imaging a plurality of chart images obtained by a photographing lens for photographing a plurality of charts at predetermined positions on the optical axis at a plurality of points on the optical axis;
M for calculating the MTF for each chart image by the imaging means at each of the plurality of points
TF calculating means, and photographing lens position determining means for determining, by the output, a focus position of the photographing lens with respect to the plurality of charts at the predetermined position based on the output obtained by the MTF calculating means. It is possible to propose a focus adjusting device for a photographing lens to be used.

(5) The focus adjusting device for a photographing lens according to any one of (1) to (3), wherein the imaging means is movable in the optical axis direction and in a direction perpendicular to the optical axis. Can be suggested.

(6) Image pickup means for picking up a chart image obtained by a photographing lens for picking up a chart at a predetermined position, MTF calculation means for calculating the MTF of the image picked up by the image pickup means, A photographing lens position adjusting device for determining a position of the photographing lens based on an output obtained by the MTF so as to determine a conjugate plane of the chart image with respect to the chart; be able to.

[0056]

According to the present invention, it is possible to provide a method of adjusting the focus of a photographic lens which can take measures based on actual photographing of a general subject, has high accuracy, and can reduce the adjustment time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a focus adjustment device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a focus adjustment device according to the embodiment of FIG. 1;

FIG. 3 is a diagram showing an example of the focus adjustment apparatus according to the embodiment shown in FIG. 1;
FIG. 4 is a diagram illustrating a change in a measured value of an F value with respect to a Z position.

FIG. 4 is a diagram showing an example of the focus adjustment apparatus according to the embodiment of FIG. 1;
FIG. 4 is a diagram illustrating a change in a measured value of an F value with respect to a Z position.

FIG. 5 is a flowchart of focus adjustment processing in the focus adjustment apparatus according to the embodiment of FIG. 1;

6 is a diagram illustrating an example of a measurement result of an MTF value for each chart in the focus adjustment apparatus according to the embodiment of FIG. 1; FIG.
6 (B) is a peripheral chart of the first quadrant, FIG. 6 (C) is a peripheral chart of the second quadrant, FIG. 6 (D) is a peripheral chart of the third quadrant, and FIG. The change of each MTF value with respect to a four-quadrant peripheral chart is shown.

FIG. 7 is a diagram showing image planes at respective focus positions based on MTF value measurement results in the focus adjustment apparatus according to the embodiment of FIG. 1;

[Explanation of symbols]

5... Chart unit (chart) 5a... Central chart portion (chart at a predetermined position on the optical axis) 5b, 5c, 5d, 5e... Peripheral chart portion (a plurality of charts at a predetermined position outside the optical axis) 11 imaging head (imaging means) 12 imaging lens (imaging means) 13 imaging device (imaging means) 22 MTF calculating section (MTF calculating section) 23 focus position calculating section (taking lens position determination) Means) 64 ...... photographic lens

Claims (2)

[Claims] An imaging unit that captures a chart image obtained by a photographing lens that captures a chart at a predetermined position; an MTF calculation unit that calculates an MTF for imaging from the imaging unit; and a chart at the predetermined position. And a photographing lens position determining means for determining a focus position of the photographing lens with respect to the above based on an output obtained by the MTF calculating means, wherein the MTF is determined at each of a plurality of points on the optical axis.
The MTF of the imaging is calculated by the calculating means, and the MTF is calculated.
A focus adjustment method for a photographic lens, wherein the focus position of the photographic lens is determined based on an output obtained by a calculation unit. 2. An image pickup means for picking up a chart image obtained by an image pickup lens for picking up a chart at a predetermined position on the optical axis and a plurality of charts at a predetermined position off the optical axis; MTF calculation means for calculating an MTF for imaging, and a focus position of the photographing lens with respect to a chart at a predetermined position on the optical axis and a plurality of charts at a predetermined position outside the optical axis, based on an output obtained by the MTF. A photographing lens position determining means for determining the MTF at each of a plurality of points on the optical axis.
A focus adjustment method for a photographing lens, wherein a MTF of each image is calculated by a calculation means, and a focus position of the shooting lens is determined based on an average value of outputs obtained by the MTF calculation means.