JP2003066317A - Focusing method and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focusing method for a camera capable of realizing accurate focusing by taking measures based on actual photographing that a general subject is photographed. SOLUTION: This camera is provided with a photographic lens 101 having a focus lens 101a, a CPU 107 being a driving control part, an MTF focusing information storage part 108 storing focus position information obtained from the MTF characteristic by a focusing device 10, a photographing mode selection part 106 and a focusing condition setting part 109. In the case of focusing the lens 101, a focusing condition corresponding to a photographing mode selected by the selection part 106 is set by the setting part 109, and the focus position information according to the MTF characteristic based on the focusing condition is read out from the storage part 108, so that the lens 101 is focused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus adjusting method for performing focus adjustment by reading out focus adjusting information stored according to a set photographing mode, and a camera for performing focus adjusting by the focus adjusting method.

[0002]

2. Description of the Related Art Conventionally, as one of focus adjusting methods for obtaining a focus position (focus position) of a photographing lens for adjusting a focus of a camera, a method of visually observing a chart using an optical bench is used to set a predetermined position. This is a method in which a set chart (Siemen star image, etc.) is passed through a photographic lens, projected onto a position corresponding to the photographic film surface, and the sharpness of the projected image is visually observed to adjust the focus. In addition, as another method, the method of measuring the brightness of the chart image with a photoelectric collimator is to project the light source chart set to a predetermined distance with a collimator lens with a photographic lens and measure the brightness of the image to detect the focus position. It is a method of adjusting the focus.

Information concerning the focusing amount of the taking lens is recorded in the camera on the basis of the focus position information of the taking lens obtained by the above adjusting method, and at the time of photographing, it relates to the focusing amount of the taking lens recorded in the camera. Focusing operation, that is, focus adjustment is performed based on the information.

[0004]

However, in the method of adjusting the focus using the above-mentioned optical bench, since it is a sensory test, there is a large variation depending on the measurer.
There is also a problem that the weighting raters for the contrast of the chart and the number of resolutions are not uniform among the raters. Moreover, the adjustment work time becomes long, and the fatigue of the evaluator is large,
The work efficiency was also poor. Further, there is a problem that the optimum focus position for the subject at the time of actual photographing does not match.

On the other hand, in the method of adjusting the focus by using the photoelectric collimator, the brightness as the light flux convergence degree of the chart is evaluated as a substitute characteristic, so that the optimum focus position for photographing a general subject is determined. Has a problem that an error easily occurs.

The present invention has been made in order to solve the above-mentioned problems, and a focus adjusting method capable of accurately setting an optimum focus position for a subject in correspondence with a real image, particularly in a photographing mode, and the above focus. It relates to a camera to which the adjustment method is applied.

[0007]

According to a first aspect of the present invention, there is provided a focus adjusting method for selecting a photographing mode, and a focus adjusting condition setting for selecting a focus adjusting condition of a photographing optical system. Means and a focus adjustment information storage means that stores focus adjustment information determined from the MTF characteristics of the image-taking optical system, wherein the focus adjustment condition setting means includes the focus adjustment condition setting means. The focus adjustment setting condition of the photographing optical system is determined according to the photographing mode selected by the mode selection means, and the focus adjustment information stored in the focus adjustment information storage means based on the determined focus adjustment setting condition. Use to adjust the focus.

According to a second aspect of the present invention, there is provided a camera including: a photographing optical system; photographing mode selecting means for selecting a photographing mode; and focus adjusting condition setting means for selecting a focus adjusting condition of the photographing optical system. Focus adjustment information storage means for storing focus adjustment information determined from MTF characteristics of the photographing optical system, focus adjustment conditions determined by the focus adjustment setting means, and focus adjustment information stored in the focus adjustment information storage means. Drive control means for adjusting the focus of the photographing optical system based on the above, and the drive control means adjusts the focus of the photographing optical system based on the focus adjustment information.

According to a third aspect of the present invention, in the camera according to the second aspect, the focus adjustment information is at least one of a position on a photographing screen, a spatial frequency, an evaluation image plane, a photographing magnification, and color information. MT of the above-mentioned photographing optical system as a parameter
It consists of F characteristics.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a camera to which a focus adjusting method according to an embodiment of the present invention is applied. In addition, the photographing optical axis Oc of the camera 100 of the present embodiment,
Alternatively, the direction parallel to the imaging optical axis Od of the focus adjustment device 10 is the Z direction, the direction orthogonal to the Z direction, the horizontal direction is the X direction, and the vertical direction is the Y direction.

The camera 100 of this embodiment has a photographing optical axis O.
A photographing lens (taking lens) 101 of a photographing optical system having c, a CPU 107 that is a drive control unit that controls the entire camera, a focus driving unit 102 for driving the focus lens 101a forward and backward, and the focus driving unit 102. Drive control unit 103 for performing drive control of
And a zoom drive unit 104 that drives the zoom lens 101b and the focus lens 101a forward and backward based on the zoom information of the CPU 107, a zoom value setting unit 111, a distance measuring unit 105, a film information detecting unit 110, and a shooting mode selecting unit. Shooting mode selection unit 106, focus adjustment condition setting unit 109 that is a focus adjustment condition setting unit, and MTF focus information storage unit 108 that is a focus adjustment information storage unit.
And a shutter mechanism unit, a film feeding drive mechanism unit and the like (not shown).

The photographing lens 101 comprises a focus lens 101a and a zoom lens 101b. The drive control unit 103 and the focus drive unit 102 are the CPU 10
In step 7, the focus lens 101a is driven back and forth to a focus position calculated based on distance measurement information and focus position information corresponding to various conditions.

The zoom value setting unit 111 is a setting unit in which the user sets the zoom value of the taking lens 101, and the zoom value is output to the CPU 107.

The distance measuring unit 105 measures the object distance via the distance measuring optical system, and the object distance information is stored in the CPU 1
It is output to 07.

The film information detector 110 detects film information such as film sensitivity of the film 112 loaded in the camera, and the film information is output to the CPU 107.

The photographing mode selection unit 106 is a mode selection unit which is composed of a mode selection switch, and the photographing mode is selected and set by the user. The photographing mode information is output to the CPU 107. The shooting modes include snap, landscape, portrait, macro, sports, night view, and infinite modes.

The focus adjustment condition setting unit 109 fetches the image pickup mode information selected by the image pickup mode selection unit 106 from the CPU 107, and determines the focus for determining the focus position of the photographing lens according to the photographing mode information. The adjustment setting condition is set and output to the CPU 107.

The focus adjustment setting conditions include the spatial frequency, image height, evaluation image plane, color information, subject distance, photographing magnification, etc. set corresponding to each photographing mode as shown in Table 1 described later. And at least one of them applies.

The MTF focus information storage unit 108 stores the MTF (Mo measured by the focus adjusting device 10 described later).
This is a storage unit that stores focus position information obtained by evaluation of the value of dulation transfer function, and is composed of an EEPROM. The focus position information is a focus position determined by evaluating the MTF value based on each spatial frequency, image height, evaluation image plane, and the like.

When performing focusing control of the taking lens 101, the taking mode selected by the taking mode selecting section 106 by the CPU 107, the zoom value information set by the zoom value setting section 111, and the distance measuring section 10 are selected.
The focus adjustment condition for setting the focus position is read from the focus adjustment condition setting unit 109 based on the subject distance information measured in step 5 and the film sensitivity information by the film information detection unit 110. Then, the CPU 107 causes the MTF focus information storage unit 108 based on the focus adjustment condition.
The focus position information stored in is read and the focus position is calculated. Then, the focus drive unit 10
The focus lens 101a is driven to the above focus position via 2 or the like. Details of this focusing operation are shown in FIG.
This will be described later with reference to the flowchart of FIG.

Here, the MTF focus information storage unit 10
The structure and operation of the focus adjustment device 10 for measuring and calculating the focus position information stored in the reference numeral 8 will be described in detail.

In the above-mentioned camera 100, usually, due to dimensional errors and assembly errors of the components of the lens frame, RDN (curvature, wall thickness, refractive index) of the lens itself, air gap between the lenses, eccentricity, etc. The total focus position changes. That is, the peak position of the MTF value changes. Therefore, the focus adjusting device 10 is applied, and the MTF value that corresponds to the actual image is measured at a plurality of points on the optical axis Oc as a measure of the evaluation of the captured image of the camera 100 that is the object to be adjusted to measure the focus of the camera 100. The position is required. The focus position data is recorded in the MTF focus information storage unit 108 of the camera 100 and is read during focusing during actual shooting.

The focus state of the photographed image in the focus adjusting device 10 is evaluated by 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 using the chart unit 5. . Then, the focus position at each point on or around the optical axis Oc is obtained.

As shown in the system diagram showing the configuration of FIG. 2 and the block diagram of FIG. 3, the focus adjusting device 10 has an image pickup section 1, a focus adjustment control section 2, a keyboard 3, a monitor 4, and a chart. It consists of unit 5. The camera 100 as the adjusted part is mounted on the imaging body 18 of the imaging unit 1. During the focus adjustment process, the camera 100 is mounted on the imaging unit body 18 with the optical axis Oc of the imaging lens 101 kept parallel to the imaging optical axis Od of the imaging lens 12 described later.

As shown in FIGS. 2 and 3, the image pickup section 1 comprises 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 section 18.

The image pickup head 11 comprises an image pickup lens 12 having an optical axis Od, and an image pickup device 13 having a CCD as an image pickup element and an image pickup processing circuit. CC above
In D, the chart image captured by the taking lens 101 of the camera 100 is CC through the taking lens 12.
An image is formed on the image forming surface of D and converted into an electric signal by the CCD. The image pickup processing circuit processes the image pickup output signal of the CCD and outputs the image data to the CPU 21 side.

The image pickup control section 14 is a C of the image pickup device 13.
The drive control of the CD and the image pickup processing circuit is performed.

The head drive unit 15 is composed of an image pickup unit main body 18
XY axis drive stage (XY axis drive section)
16 and a Z-axis drive stage (Z-axis drive unit) 17. An imaging head 11 is mounted on the XY axis drive stage 16, and the imaging head 11 is moved in the X direction and the Y direction.
Drive in the direction. Further, the XY-axis drive stage 16 is attached to the Z-axis drive stage 17, and the X-axis drive stage 16 is attached to the X-axis drive stage 16.
The Y-axis drive stage 16 is driven in the Z direction to drive the imaging head 11 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 image pickup section 1 and
In addition to the control unit that controls the camera 100, an MTF calculation unit 22 that is an MTF calculation unit and a focus position calculation unit 23 that is a photographing lens position determination unit are incorporated. Above MT
The F calculation unit 22 takes in the chart image data output from the imaging device 13 and outputs the MTF of the chart image.
Calculate the value. The focus position calculation unit 23,
The focus position of the camera 100 is calculated based on the MTF value output from the MTF calculation unit 22, and the focus position data is written to the EEPROM (MTF focus information storage unit) 108 via the CPU 107 of the camera 100.

The keyboard 3 is for making various settings when executing the focus adjustment processing, and the monitor 4 is for confirming the operating state during the focus adjustment processing.

The chart unit 5 has a standard shooting distance L1 which is a subject distance applied during normal camera shooting.
, For example, a test chart on a photographing image frame arranged at a position separated by 3 m, and a central chart portion 5a located on the photographing lens optical axis Oc of the camera 100, and XY
The peripheral chart portion 5b of the first quadrant, the peripheral chart portion 5c of the second quadrant, the peripheral chart portion 5d of the third quadrant, and the peripheral chart portion 5 of the fourth quadrant in the peripheral position of the photographing image frame on the plane.
with e.

The central chart portion 5a has a predetermined pitch in the X and Y directions (spatial frequency f0 = 10 / m).
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 / mm) in the radial direction (S direction) and the circumferential direction (M direction). The above spatial frequency f0 = 10 lines / mm is applied to the standard of focus adjustment because the spatial frequency corresponds well with the quality of the shooting screen at the time of actual shooting, as compared with the higher spatial frequencies f1 and f2 described later. Is.

However, the spatial frequency f0 = 10 lines / mm
In addition to this, for example, it is necessary to simultaneously perform focus position measurement using a chart portion having a high spatial frequency f2 = 30 lines / mm necessary for focus position adjustment such as macro photography, landscape photography, and infinity photography. .

Next, the adjustment processing operation such as the measurement of the MTF value of the camera 100 by the focus adjusting apparatus 10 having the above-mentioned configuration will be described. The camera 100 and the head drive unit 15 are set in the MTF value measurement state around the optical axis O or around the screen. That is, the camera 100 is attached to the rear lid 1.
13 is opened and attached to the imaging unit main body 18 of the imaging unit 1. At that time, it is confirmed that the optical axis Oc of the taking lens 101 of the camera 100 and the center of the central chart portion 5a of the chart unit 5 coincide with each other. Also,
The taking lens 101 is extended to the designed in-focus position with respect to the standard photographing distance L1. In the camera set state, the position of the aperture (film surface) 112 is the designed virtual image formation position of the taking lens 101 with respect to the chart.

To measure the MTF value around the optical axis O, the XY axis stage 16 of the head driving section 15 is driven to move the imaging head 11 (imaging lens 12) to the center of the optical axis Oc of the aperture section 112 of the camera 100. The optical axes Od are matched.

To measure the surrounding MTF value, use the above X
By driving the Y-axis stage 16, the optical axis Od of the imaging head 11 (imaging lens 12) is placed on the aperture 112 of the camera 100 at the peripheral pattern image position in one of the first to fourth quadrants to be measured. Match.

When measuring the MTF value at or around the center of the optical axis O, the Z-axis drive stage 17 moves the imaging head 11 to the Z direction.
The focus point of the imaging lens 12 is moved in the front-back direction of the aperture plane 112 by driving in the direction, 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 112, the displacement position Zd = 0, which is the reference Z-direction displacement amount (defocus amount), is set as Zd = 0, and Z when it is on the rear side (back side) of the aperture 112. The direction shift position Zd is the + side, and the Z direction shift position Zd when it is on the front side (subject side) is the − side.

The image pickup head 11 is displaced in the Z direction by the position Zd.
In the case of, the image of the central chart 5a or the image of the peripheral chart (in this case, the peripheral chart 5e of the fourth quadrant) captured by the taking lens 101 forms an image on the image forming plane of the CCD, and the image is formed on the CCD. Are converted into electrical image signals. The image pickup signal of the chart image is transferred to C via the image pickup device 13.
It is output to the PU 21 side. Then, the MTF calculator 22 calculates the MTF value of the chart image.

FIG. 4 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 position Zd = on the surface of the aperture 112.
The change in the MTF value of the chart image at the shift position Zd in the Z direction (optical axis direction) from 0 is shown. In the figure, the curves of f0, f1 and f2 in the central chart portion are the vertical or horizontal of the spatial frequencies f0 of the chart = 10 lines / mm, f1 = 20 lines / mm, f2 = 30 lines / mm, respectively. The change of the MTF value of a direction pattern is shown.

In the measurement result of FIG. 4, 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, it indicates that the surface of the aperture 112 is in the focus position. The calculation for obtaining the peak point is performed by the focus position calculation unit 23 of the CPU 21.

Next, when measuring the MFT value around the photographing frame, for example, when measuring the peripheral MFT value in the fourth quadrant, the peripheral chart portion 5e in the fourth quadrant of the chart unit 5 on the aperture 112 is displayed. The XY axis stage 16 of the head driving unit 15 is driven so that the optical axis Od of the imaging lens 12 of the imaging head 11 matches the image position, and the imaging head 11 is moved to the Z axis in the same manner as the MTF value measurement of the optical axis O center. The MTF value is measured while driving in the direction.

FIG. 5 is a diagram showing the change in the measured MTF value with respect to the image of the peripheral chart portion 5e. In the figure, the curves of f0, f1 and f2 in the peripheral chart part are
Spatial frequency f0 of each chart = 10 / mm, f
MT when 1 = 20 lines / mm and f2 = 30 lines / mm
The change of the F value is shown, and the solid line shows the MTF value of the S direction pattern and the broken line shows the M direction value of the M direction pattern.

MT of the image of the peripheral chart portion 5e shown in FIG.
The F value has a peak at the shift position Zd = + 0.20 mm (peak point P4). That is, the aperture 112
It is shown that the peak position P4 which is set back 0.20 mm from the plane is the focus position of the peripheral chart 5e in the fourth quadrant. The calculation for obtaining the position of this peak point is performed by the CPU.
This is performed by the focus position calculation unit 23 of 21.

When the focus adjustment device 10 actually performs the focus adjustment, the change in the MTF value with respect to each shift position Zd around the aperture plane of the peripheral pattern in the first to third quadrants other than the fourth quadrant is also measured. . A peak position P1 indicating another focus position with respect to the peripheral pattern according to the measurement result
, P2, P3 are obtained.

After that, each peak position (focus position) P0 for each of the above patterns, and P1, P2, P3,
The shift position Zd data of P4 is transferred to the CPU 107 on the camera 100 side as the focus extension amount (giving a conjugate plane to the standard subject distance L1) of the camera 100 and written in the EEPROM 108.

Next, the focus adjusting operation by the focus adjusting device 10 will be described with reference to the flowchart of FIG. 6 and FIGS.
Will be specifically described. FIG. 7 is a diagram showing an example of the measurement result of the MTF value for each chart, where FIG. 7A is the central chart 5a, FIG. 7B is the peripheral chart 5b in the first quadrant, 7C is a peripheral chart 5c in the second quadrant, FIG. 7D is a peripheral chart 5d in the third quadrant, and FIG. 7E is a peripheral chart 5e in the fourth quadrant.
The change of the MTF value with respect to is shown, and an example in the case where the spatial frequency of the chart is f0 = 10 lines / mm is shown. FIG. 8 is a diagram showing each focus position image plane based on the MTF value measurement result.

When performing the focus adjustment, first, the focus adjusting device 10, the chart unit 5, and the camera 100 are set to the above-described MTF value measurement state. That is, the camera 100 is set on the imaging unit main body 18 and the photographing lens 10
The optical axis Oc of 1 and the central chart portion 5 of the chart unit 5
Match the centers of a. Further, the photographing lens 101 of the camera 100 is extended to the designed in-focus position with respect to the standard photographing distance L1, and the focus adjustment processing of FIG. 6 is started under the control of the CPU 21 of the focus adjustment device 10.

In step S1, the optical axis Od of the image pickup head 11 is moved to the optical axis Oc by the XY axis drive stage 16.
And the chart image of the central chart portion 5a can be captured. While moving the imaging head 11 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 of the optical axis O center (center chart portion 5e) of the chart unit 5 shown in FIG. Is measured (see FIG. 7A).

In step S2, the XY axis drive stage 16 is driven to sequentially align the optical axis Od of the image pickup head 11 with the image forming positions of the peripheral chart portions 5b, 5c, 5d, 5e in the first to fourth quadrants. The respective peripheral chart images are set in the imageable state. By driving the imaging head 11 in the Z direction by the Z-axis drive stage 17, changes in the MTF values of the peripheral chart images in the first to fourth quadrants with respect to each shift position (shift amount) Zd are measured (see FIG. 7 ( B) ~
(See (E)).

In step S3, the above step S1
The shift position Zd (0) of the focus position, which is the image plane position of the optical axis that gives the peak point P0 of the MTF value of the optical axis O center measured in
Is calculated by the focus position calculator 23. For example, above 7
When the measurement result of (A) is obtained, the MTF value peak point P
The optical axis center image plane shift position Zd (0) = 0.0 that gives 0
0 mm is required. That is, the MTF value peak point P0
Matches Zd = 0. Further, FIG. 8 shows the image plane 71 including the position of the peak point P0 and the shift amount Zd (0) giving the point P0. The shift position Zd (0)
When the taking lens 101 is extended so that the image forming positions of the taking lens 101 coincide with each other, at least a subject at the center of the optical axis O can be taken in focus.

In step S4, the above step S2
Peak point P1 of MTF value around each quadrant measured in
Each shift position Zd of the image plane position (focus position) that gives P4
Is calculated by the focus position calculation unit 23. For example, in FIG.
When the measurement results of (B) to (E) are obtained, the shift position that gives the peripheral MTF value peak point P1 in the first quadrant is Zd.
(1) =-0.30 mm. Around the second quadrant MTF
The shift position giving the value peak point P2 is Zd (2) = +
It is 0.20 mm. The shift position that gives the peripheral MTF value peak point P3 in the third quadrant is Zd (3) = + 0.10 mm.
Is. Then, the peripheral MTF value peak point P4 in the fourth quadrant
The shift position that gives Zd (4) = + 0.20 mm.

Therefore, the focus position calculation unit 23 gives a peripheral average image plane position (peripheral average focus position) which is in focus on all the above-mentioned peripheral regions, and a shift position Zd (1/4)
Is calculated by the arithmetic mean. That is, Zd (1/4) = {Zd (1) + Zd (2) + Zd (3) + Zd (4)} / 4 (1)

Substituting the respective displacement position data shown in FIG. 7 into the above equation (1), the peripheral average image plane displacement position Zd
(1/4) = + 0.05 mm. FIG. 8 shows the positions of the peak points P1, P2, P3 and P4 in the Z direction, the peripheral average image plane displacement position Zd (1/4) and the displacement position Zd.
An image plane 72 including (1/4) is shown. If the taking lens 101 is extended to the position corresponding to the above-mentioned shift position Zd (1/4), at least the subject in the periphery of the screen can be photographed in focus on average.

In step S5, the focus position calculating unit 23 shifts the shift position (shift amount) Z of the peripheral average image plane.
The deviation position (deviation amount) between d (1/4) and the image plane of the optical axis center Z
A shift position (shift amount) Zd (m) that gives an intermediate position (focus adjustment point) between the two is obtained by an arithmetic mean with d (0). That is, Zd (m) = {Zd (1/4) + Zd (0)} / 2 (2)

The shift position Zd (1/4) = + in the above equation (2)
Substituting 0.05 mm and the displacement position Zd (0) = 0.00 mm, the intermediate displacement position Zd (m) = + 0.025 mm
Is required. The above-mentioned calculation is performed by the focus position calculation unit 23.
Will be held in. FIG. 8 shows the intermediate shift position Zd (m).
And the image plane 73 including the shift position Zd (m).

In step S6, the above step S5
The EEPR of the camera 100 is used as the focus extension amount data of the photographing lens 101 in which the shift position Zd (m) data that gives the intermediate shift position obtained in step S1 corresponds to the film surface position.
Transfer to OM 108 and write.

After that, the camera 100 is attached to the focus adjusting device 1
The image pickup unit main body 18 of 0 is removed, and the focus adjustment processing ends.

Next, regarding the focus adjusting operation for the photographing optical system, f0 = 10 lines / mm as a plurality of spatial frequencies.
The process of obtaining the focus position shift position Zd data according to the MTF value at f2 = 30 lines / mm will be described below. This processing is performed by the CPU of the focus adjustment device 10.
It is executed under the control of 21 according to the flowchart of FIG. The MTF calculation unit 22 and the focus position calculation unit 23 of the CPU 21 determine the change in each MTF value, each peak point position, the optical axis center image plane deviation position, each peripheral average image plane deviation position, each intermediate image plane deviation position, and the like. Is calculated by.

In FIGS. 9A to 9E, the spatial frequency f0 =
MTF for 10 / mm and f2 = 30 / mm
It is a diagram which shows the result of having measured the change of a value. The measurement results show the average values of the MTF values of the two types of evaluation image planes in the radial direction (sagittal S direction) and the circumferential direction (meridional M direction) of each chart, and the subject distance L1 is the standard subject distance. It will be 3m.

FIG. 9A is an MTF characteristic diagram for the center chart 5a. The MTF value characteristic line 80 of f0 = 10 lines / mm and the MTF value characteristic line 90 of f2 = 30 lines / mm.
And indicates. Deviation position Zd (0,10) = 0.00 of the optical axis center image plane indicated by the peak point P10 of the MTF value characteristic line 80.
Let mm be the Z-direction reference position for all MTF characteristic measurements.
On the other hand, from the MTF value characteristic line 90, the shift position Zd (0,30) =-0.
15 mm is obtained.

FIG. 9B is a peripheral chart 5 in the first quadrant.
It is an MTF value characteristic diagram for b, and f0 = 10 / m
MTF value characteristic line 81 of m, MTF of f2 = 30 lines / mm
A value characteristic line 91 is used. The shift position Zd that gives the peripheral MTF value peak point P11 of the first quadrant of the MTF value characteristic line 81.
(1,10) = 0.45 mm is obtained. Further, a shift position Zd (1,30) = 0.1 mm which gives the peripheral MTF value peak point P31 of the first quadrant of the MTF value characteristic line 91 is obtained.

FIG. 9C is a peripheral chart 5 in the second quadrant.
It is an MTF value characteristic diagram for c, and f0 = 10 / m
m MTF value characteristic line 82, f2 = 30 lines / mm MTF
A value characteristic line 92 is used. The shift position Zd that gives the peripheral MTF value peak point P12 in the second quadrant of the MTF value characteristic line 82.
(2,10) = 0.25 mm is obtained. Further, a shift position Zd (2,30) = 0.05 mm giving the peripheral MTF value peak point P32 of the second quadrant of the MTF value characteristic line 92 is obtained.

FIG. 9D shows a peripheral chart 5 in the third quadrant.
It is an MTF value characteristic diagram for d, and f0 = 10 / m
m MTF value characteristic line 83, f2 = 30 lines / mm MTF
The value characteristic line 93 is used. The shift position Zd that gives the peripheral MTF value peak point P13 of the third quadrant of the MTF value characteristic line 83
(3,10) = 0.2 mm is obtained. Further, a shift position Zd (3,30) =-0.2 mm giving the peripheral MTF value peak point P33 in the third quadrant of the MTF value characteristic line 93 is obtained.

FIG. 9E shows a peripheral chart 5 in the fourth quadrant.
Is a characteristic diagram of respective MTF values for f 0 = 1
0 line / mm MTF value characteristic line 84, f2 = 30 lines / mm
Of the MTF value characteristic line 94. The MTF value characteristic line 84
A shift position Zd (4,10) = 0.38 mm giving the peripheral MTF value peak point P14 in the fourth quadrant of is obtained. Also, MT
Peripheral MTF value peak point P34 of the F value characteristic line 94 in the fourth quadrant
A shift position Zd (4,30) = 0.1 mm is obtained.

The marginal average image plane displacement position Zd (1 / 4,10) for the spatial frequency f0 = 10 lines / mm is expressed by the above equation (1) based on the displacement position Zd of the MTF value peak point in each quadrant. It is calculated using the same formula.

That is, the peripheral average image plane shift position Zd (1 /
4,10) is obtained by Zd (1 / 4,10) = {Zd (1,10) + Zd (2,10) + Zd (3,10) + Zd (4,10)} / 4 (11). Substituting the respective displacement position data shown in FIG. 9 into the equation (11), the peripheral average image plane displacement position Z
d (1 / 4,10) = 0.32 mm is obtained.

Further, the spatial frequency f0 = 10 lines / m
The intermediate image plane displacement position Zd (m, 10) with respect to m is obtained using the same arithmetic expression as the above-mentioned expression (2).

That is, the intermediate image plane shift position Zd (m, 10)
Is calculated by Zd (m, 10) = {Zd (1 / 4,10) + Zd (0,10)} / 2 (12). Substituting the respective displacement position data shown in FIG. 9 into the equation (12), the intermediate image plane displacement position Zd
(M, 10) = 0.16 mm.

The spatial frequency f2 = 30 lines / mm
The peripheral average image plane shift position Zd (1/4, 30) with respect to is also obtained from the shift position Zd of the MTF value peak point in each quadrant by the same calculation formula as the above formula (1).

That is, the peripheral average image plane shift position Zd (1 /
4,30) is obtained by Zd (1 / 4,30) = {Zd (1,30) + Zd (2,30) + Zd (3,30) + Zd (4,30)} / 4 (13). Substituting the respective displacement position data shown in FIG. 9 into the equation (11), the peripheral average image plane displacement position Z
d (P1 / 4,30) = 0.32 mm is obtained. further,
The intermediate image plane shift position Zd (m, 30) for the spatial frequency f2 = 30 lines / mm can also be calculated by the same calculation formula as the above formula (2).

That is, the intermediate image plane shift position Zd (m, 30)
Is calculated by Zd (m, 30) = {Zd (1 / 4,30) + Zd (O, 30)} / 2 (14). Substituting the respective displacement position data shown in FIG. 9 into the equation (12), the intermediate image plane displacement position Zd
(M, 30) = 0.069 mm is required.

FIG. 10 shows that the spatial frequency f0 is 10 lines / mm.
FIG. 6 is a diagram showing each focus position image plane based on the above MTF value measurement result for FIG.

In FIG. 10, each P point is the peak point P10 to P of the MTF value characteristic line on the optical axis center and each quadrant.
14 is shown. The image plane 85 has a peak point P10 at the center of the optical axis.
And a surface including the reference optical axis center image plane shift position Zd (O, 10). The image plane 86 has a peripheral average image plane shift position Zd (1 / 4,1
0) and the corresponding virtual peak point P (1 / 4,10) are included. The image plane 87 is a plane including the intermediate image plane shift position Zd (m, 10) and the corresponding virtual peak point P (m, 10).

On the other hand, FIG. 11 is a diagram showing each focus position image plane based on the MTF value measurement result for the spatial frequency f2 = 30 lines / mm.

In FIG. 11, each P point is the peak point P30 to P of the MTF value characteristic line on the center of the optical axis and on each quadrant.
34 is shown. The image plane 95 has a peak point P30 at the center of the optical axis.
And a surface including the reference optical axis center image plane shift position Zd (0,30). The image plane 96 has a peripheral average image plane shift position Zd (1 / 4,3
0) and the corresponding virtual peak point P (1 / 4,30) are included in the plane. The image plane 97 is a plane including the intermediate image plane shift position Zd (m, 30) and the corresponding virtual peak point P (m, 30). However, the image plane 85 has the spatial frequency f0 = 10 shown in FIG.
A surface including a reference optical axis center image plane shift position Zd (0, 10) including a peak point P10 of the MTF value characteristic line in the case of lines / mm is shown.

The optical axis center image plane shift position Zd (0,1) obtained by calculation in the focus position calculation unit 23 of the CPU 21.
0), Zd (0,30), and the intermediate image plane shift position Zd
(M, 10), Zd (m, 30), etc. are transferred from the CPU 21 to the camera 1
00 is transferred to the CPU 107, and the EEPROM 108
The focus adjustment by the focus adjustment device 10 is completed.

Although the subject distance has been described as the standard distance L1 in the above-mentioned example, actually, the shift position Zd data of each focus position with respect to a plurality of distances before and after the standard subject distance L1 are also measured and calculated. , E on the camera 100 side
It is written in the EPROM 108. On the camera 100 side, the actual shift position Zd data of the focus position is obtained by interpolating the shift position Zd data of the plurality of distances according to the subject distance measured by the distance measuring unit 105, and focusing is performed.

Similarly, for each zoom state of the taking lens 101, a change in the shift position Zd data of each focus position is calculated and obtained, and similarly, the EEPROM 10 of the camera 100 side.
Written in 8. Shift position Z for this zoom state
With the d data, accurate focusing can be performed even in each zoom state.

The focus adjustment condition setting unit 109 provided in the camera 100 of the present embodiment sets the focus adjustment setting condition for determining the focus position of the photographing lens according to the photographing mode information as described above. However, as the focus adjustment setting condition, there are various conditions shown in Table 1 corresponding to the photographing mode.

[0081]

[Table 1]

As shown in Table 1, shooting modes selectable by the mode selection unit 06 include snap mode, landscape mode, portrait mode, macro mode, sports mode, night view mode, and infinite mode. As conditions for evaluating the MTF value for focus position calculation according to each mode, spatial frequency, image height, evaluation image plane, color information, shooting distance,
There is a zoom position (magnification). Parameters for each condition are set according to the shooting state, and the MTF focus information storage unit (EE
The focus position information stored in the PROM) 108 is read.

As the spatial frequency, as shown in the above example, for example, the spatial frequency 10 shown in the example of FIG. 9 is used.
Lines / mm, 30 lines / mm are applied.

The image height gives a position on the photographic screen. The image height is 0 at the center of the screen (on the optical axis Oc) and the maximum image height is at the four corners (periphery) of the photographic screen. To do.
And, with regard to the image height, the central point is M at image height 0.
It indicates that the TF evaluation value is adopted as the focus position information. As the MTF evaluation value, in the examples of FIGS. 10 and 11, the optical axis center image plane deviation amounts Zd (0,10) and Zd (0,30) are used.
Corresponds. Further, the whole surface average means that the average value of the MTF evaluation values at the image height of 0 (center) and the maximum (around 70% of the diagonal length) is adopted as the focus position information. In the examples of FIGS. 10 and 11, the MTF evaluation values correspond to the intermediate image plane deviation amounts Zd (m, 10) and Zd (m, 30).

The above-mentioned evaluation image planes are the image plane types in the S direction (sagittal direction) and the M direction (meridiorial direction) that indicate the inclination of the pattern of the test chart, and the S and M averages are S.
It shows that the MTF values obtained on the image planes in the direction M and the direction M are evaluated by the average value.

With respect to the above color information, when evaluating the MTF value, the method of weighting the wavelength of the subject light is shown, and is matched with the human visual sensitivity. Further, the luminosity is switched between the color film and the monochrome film.

Regarding the above-mentioned photographing distance and zoom position, when evaluating the MTF value, the evaluation value of the MTF value is corrected by the measured subject distance or the set scaling factor. Data is interpolated to correct the MTF value.

The evaluation data of the MTF value using each condition such as the spatial frequency to the zoom position as a parameter is EE.
It is stored in the PROM 108.

Next, a photographing sequence including a focusing process by the camera 100 of the present embodiment having the above-described structure will be described with reference to the flowchart of FIG. It should be noted that the processing of the shooting sequence is performed by the CPU 107.
It is executed under the control of.

In step S11, the photographing mode selection unit 106
The CPU 107 sets the shooting mode by detecting the on / off state by operating the mode selection switch.

In step S12, it is checked whether the 1st release switch is turned on or off by the first step operation of the release operation button, and if it is turned on, the process proceeds to step S13.

In steps S13 and S14, the distance measuring unit 1
The distance measurement of the subject is performed by 05, and the distance measurement data is C
It is taken into the PU 107.

In step S15, the zoom value data set by the output of the zoom value setting unit 111 is confirmed.

In step S16, the CPU 107
Condition setting parameters of the focus adjustment condition setting unit 109 are set based on the photographing mode, the distance measurement data, the zoom value data, the film information read by the film information detection unit 110, and the like.

In step S17, the CPU 107 reads the focus position information based on the MTF value evaluation stored in the EEPROM 108 based on the condition setting parameters. Then, the focus drive amount of the focus lens 101a that provides the optimum focus position is calculated from the focus position information.

In step S18, it is checked whether the second release switch is turned on or off by the second operation of the release operation button. If it is turned on, the process proceeds to step S19.

In step S19, the CPU 107 drives the focus lens 101a by the focus drive amount via the drive control unit 103.

In step S20, the shutter is opened and closed under the optimum focus condition to expose the film 112, and the main photographing sequence is completed.

According to the camera 100 in which the focus is adjusted by the focus adjusting device 10 as described above, the EEPRO
Focusing position information suitable for the shooting mode is read out from the focusing position information written in M108, and focusing of the shooting lens 101 is executed. Therefore, it is possible to perform shooting in a state in which the shooting is performed in a state in which the shooting corresponds to a general shooting of a general subject and which is most suitable for each shooting mode.

Further, in the camera 100, there are variations in the component dimensions and assembly dimensions of the lens frame that holds the taking lens,
Also, the peak point of the MTF value changes depending on the image height (position on the photographic screen) due to RDN (curvature, thickness, refractive index) of the photographic lens alone, the air gap between the lenses, eccentricity, and the like. However, those influences can be removed by performing the focus adjustment using the focus adjustment device 10.

In the camera 100, a distance measuring optical system different from the taking lens optical system is applied as the distance measuring unit 105, but the scope of the present invention is not limited to this.
It can also be applied to a focusing method (TTL method) for evaluating an image by a taking lens.

Based on the above-described embodiment, (1) photographing optical system, photographing mode selecting means for selecting photographing mode, and focus position setting condition selecting means for selecting focus position setting condition of the photographing optical system. And MT of shooting optical system
The focus position information storage means stores the focus position information determined from the F characteristic, the focus position setting condition determined by the focus position setting condition selection means, and the focus position information stored in the focus position information storage means. Drive control means for adjusting the focus of the photographing optical system based on the above, and the focus position information is a parameter of at least one of a position on a photographing screen, a spatial frequency, an evaluation image plane, a photographing magnification, and color information. It is possible to propose a camera characterized by having the MTF characteristic of the above-mentioned photographing optical system.

(2) Shooting optical system, shooting mode selecting means for selecting a shooting mode, focus position setting condition selecting means for selecting focus position setting conditions of the shooting optical system, and MTF characteristic of the shooting optical system. And a focus position information stored in the focus position information storage means, the focus position setting condition defined by the focus position setting condition selecting means, and the focus position information stored in the focus position information storage means. The focus of the photographing optical system is set on the basis of, and the photographing position information is obtained by using at least one of the position on the photographing screen, the spatial frequency, the evaluation image plane, the photographing magnification, and the color information as the parameter. It is possible to propose a focus setting method for a camera, which is characterized by comprising the MTF characteristic of the optical system.

(3) When the portrait mode is selected,
It is possible to propose the camera focus setting method described in (2) above, characterized in that focus adjustment information based on an MTF value of a low spatial frequency of about 10 lines / mm is selected in the center of the screen.

(4) When the macro mode is selected, MT with a high spatial frequency of about 30 lines / mm is displayed at the center of the screen.
It is possible to propose the camera focus setting method described in the above (2), which is characterized in that focus adjustment information based on an F value is selected.

(5) When the general snap mode is selected,
It is possible to propose the camera focus setting method described in (2) above, characterized in that focus adjustment information based on an MTF value of a low spatial frequency of about 10 lines / mm is selected in the center of the screen.

(6) When the landscape mode is selected, the average value is about 30 lines / mm in the central part of the screen and the peripheral part of the screen.
It is possible to propose the camera focus setting method according to the above (2), which is characterized in that focus adjustment information based on the MTF value of a high spatial frequency is selected.

(7) When the sport mode is selected, M at a low spatial frequency of about 10 lines / mm is displayed at the center of the screen.
It is possible to propose the camera focus setting method described in (2) above, which is characterized in that focus adjustment information based on a TF value is selected.

(8) When the night view mode is selected, the MTF having a low spatial frequency of about 10 lines / mm is displayed at the center of the screen.
It is possible to propose the camera focus setting method described in the above (2), which is characterized in that focus adjustment information based on a value is selected.

(9) When the infinite mode is selected, the focus adjustment information based on the MTF value of the high spatial frequency of about 30 lines / mm on average is selected in the central portion and the peripheral portion of the screen (2). The described camera focus setting method can be proposed.

(10) Focus position storing means for storing the focus position of the photographing lens, photographing mode selecting means, photographing mode selected by the photographing mode selecting means,
Selecting means for selecting an optimum focus setting condition based on focus setting information having an MTF value as an evaluation value, and the focus position of the photographing lens stored in the focus position storing means is a predetermined position. An image pickup means for picking up a chart image obtained by the photographing lens for photographing a chart, an MTF calculating means for photographing from the photographing means, and a focus position of the photographing lens with respect to the chart at the predetermined position are MTF values. By using the photographing lens position determining means determined by the output obtained by the calculating means, the MT at each of a plurality of points on the chart.
At the focus position of the taking lens obtained by the focus adjustment method, the MTF value of the image pickup is calculated by the F value calculating means, and the focus position of the taking lens is determined by the output obtained by the MTF value calculating means. It is possible to propose a camera characterized by being present.

[0112]

According to the present invention, the focus adjusting method for a camera capable of accurately and automatically setting the optimum focus position for an object, particularly in a state corresponding to the actual shooting according to the shooting mode, or the above focus adjusting method is applied. A camera can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of a camera to which a focus adjustment method according to an embodiment of the present invention is applied.

FIG. 2 is a system diagram showing a configuration of a focus adjustment device applied to the camera of the embodiment of FIG.

FIG. 3 is a block configuration diagram showing a configuration of the focus adjustment device of FIG.

FIG. 4 is a diagram showing a change in a measured value of an MTF value with respect to an Z position with respect to an image of a central chart portion at the time of measuring the MTF in the focus adjusting apparatus of FIG. 2;

FIG. 5 is a diagram showing a change of a measured value of an MTF value with respect to an image of a peripheral chart portion with respect to a Z position at the time of measuring the MTF in the focus adjustment apparatus of FIG. 2;

6 is a flowchart of focus adjustment processing in the focus adjustment apparatus of FIG.

7 is a diagram showing an example of measurement results of MTF values for each chart in the focus adjustment apparatus of FIG. 2, wherein FIG. 7 (A) is the central chart and FIG. 7 (B) is the first quadrant. 7C is for the peripheral chart of the second quadrant, FIG. 7D is for the peripheral chart of the third quadrant, and FIG. 7E is for the peripheral chart of the fourth quadrant. The change in MTF value is shown.

FIG. 8 shows the focus adjustment device of FIG.
The figure which shows the image surface of each focus position based on the MTF value measurement result of (A)-(E).

9 is a diagram showing another example of the measurement result of the MTF value for each chart in the focus adjustment apparatus of FIG. 2, FIG. 9 (A) being the central chart and FIG. 9 (B) being the first chart; 9C is a peripheral chart of the second quadrant, FIG. 9D is a peripheral chart of the third quadrant, and FIG. 9E is a peripheral chart of the fourth quadrant. The change of each MTF value with respect to is shown.

10 is an image of each focus position based on the measurement result for the spatial frequency f0 = 10 lines / mm among the MTF value measurement results of FIGS. 9 (A) to 9 (E) in the focus adjustment apparatus of FIG. 2; FIG.

11 is an image of each focus position based on the measurement result for the spatial frequency f2 = 30 lines / mm among the MTF value measurement results of FIGS. 9 (A) to 9 (E) in the focus adjustment apparatus of FIG. 2; FIG.

FIG. 12 is a flowchart of a shooting sequence including focusing processing by the camera 100 of the present embodiment of FIG.

[Explanation of symbols]

101 ... Shooting lens (shooting optical system) 106 ... Mode selection means (shooting mode selection means) 107 ... CPU (drive control means) 108 ... MTF focus information storage unit (focus adjustment information storage means) 109 ... Focus Adjustment condition setting section (focus adjustment condition setting means)

Continued front page    F term (reference) 2F065 AA06 DD10 FF01 JJ03 JJ26                       PP02 QQ24 QQ25 QQ28 RR00                       TT02 UU07                 2H011 AA01 BA31 BB04 CA01 DA00                 2H051 AA01 BA47 EB13 EB20 FA52                       GB12 GB19

Claims (3)

[Claims] 1. A photographing mode selection means for selecting a photographing mode, a focus adjustment condition setting means for selecting a focus adjustment setting condition of a photographing optical system, and a focus adjustment determined from an MTF characteristic of the photographing optical system. A focus adjustment information storage unit that stores information, and a focus adjustment method for performing focus adjustment using the focus adjustment condition setting unit, wherein the focus adjustment condition setting unit is the photographing optical system according to the photographing mode selected by the photographing mode selecting unit. The focus adjustment method is characterized in that the focus adjustment setting condition is determined, and the focus adjustment is performed using the focus adjustment information stored in the focus adjustment information storage means based on the determined focus adjustment setting condition. 2. A photographing optical system, a photographing mode selecting means for selecting a photographing mode, a focus adjusting condition setting means for selecting a focus adjusting setting condition of the photographing optical system, and an MTF characteristic of the photographing optical system. The focus adjustment information storage means for storing the adjusted focus adjustment information, the focus adjustment information determined by the focus adjustment setting means, and the focus adjustment information stored in the focus adjustment information storage means. A camera comprising: a drive control unit for performing focus adjustment. 3. The focus adjustment information comprises MTF characteristics of the photographic optical system with at least one of a position on a photographic screen, a spatial frequency, an evaluation image plane, a photographic magnification, and color information as a parameter. The camera according to claim 2.