JP3713793B2 - Focus adjustment device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a focus adjustment device that automatically adjusts the focus state of an optical device, and in particular, a focus state range (hereinafter, referred to as a focus state) that is recognized as a focus state by repeating focus determination with an appearance probability associated with the focus state. The present invention relates to a focus adjustment device in which a desired slope is provided in this range (referred to as “focusing recognition width”).
[0002]
[Prior art]
Conventionally, an optical apparatus such as a camera is equipped with a focus adjustment device in order to automatically adjust the focus of the optical system.
[0003]
In these automatic focus adjustment apparatuses, a focus state such as a defocus amount is sequentially detected by using a known focus detection method (such as a phase difference detection method or an external light passive method).
Based on the latest defocus amount detected in this way, the target driving position of the photographing optical system is sequentially calculated, and the photographing optical system is controlled so as to reach the target driving position.
[0004]
Ideally, when the photographing optical system reaches the target drive position, the defocus amount becomes zero, and the photographing optical system stops at that position.
However, practically, the detection value of the defocus amount varies slightly due to noise generated in the focus detection CCD or the like. For this reason, even when the photographing optical system reaches the target drive position, the detection value of the defocus amount does not become completely zero. Therefore, the photographing optical system is continuously driven, and slight vibration (hunting) occurs.
[0005]
Therefore, in this type of focus adjustment device, a focus-authentication range as shown in FIG. 18A is set in advance.
In this setting, the “defocused state” is uniformly determined when the defocus amount is less than 100 μm. The focus adjustment device stops updating the target drive position according to the determination of the in-focus state.
[0006]
Therefore, even if the defocus amount fluctuates within the in-focus range, the target drive position does not fluctuate and hunting does not occur in the photographing optical system.
Further, as shown in FIG. 18B, there is also known one in which a hysteresis is provided in the in-focus authorized width.
In such a setting, once the defocus amount falls within the range of the in-focus recognition range, the in-focus determination range is widened. For this reason, the defocus amount rarely comes out of the range of the in-focus authorized range, and hunting of the photographing optical system can be strongly prevented.
[0007]
[Problems to be solved by the invention]
By the way, in the conventional example shown in FIG. 18A, when the defocus amount is in the vicinity of the boundary of the in-focus recognition width, the determination of the in-focus state is changed twice or more due to the detection variation of the defocus amount.
Therefore, as shown in FIG. 19, the actual in-focus recognition range is a convolution of “a pulse-like probability distribution indicated by the in-focus determination authentication range” and “a probability distribution of the true defocus amount”. It becomes the form of integration.
[0008]
Therefore, the range of “actual focus recognition width” is widened by “establishment distribution of true defocus amount”.
Since this widened area (bottom part) is located outside the range of the “setting focus recognition width”, it is an area that is erroneously determined to be in focus while the detection error of the defocus amount remains large.
[0009]
In such an erroneously determined region, the target drive position is fixed based on the defocus amount with a large detection error (actually the defocus amount immediately before that). For this reason, there is a problem in that the remaining defocus amount becomes larger than expected when the photographing optical system reaches the target drive position.
In particular, in the conventional example shown in FIG. 18B, since hysteresis is provided, once it is erroneously determined to be in focus, it is less likely to be correctly determined to be out of focus thereafter. For this reason, there has been a problem that the above-described residual defocus amount occurs almost definitely.
[0010]
In addition, in a moving subject, the defocus amount changes every moment as the subject distance changes. When focus adjustment is performed on this moving subject, the value of the defocus amount often changes beyond the in-focus recognition range.
As described above, since the target drive position is not updated during the period in which the defocus amount passes the in-focus recognition range, it acts as a non-linear dead zone in terms of control operation.
[0011]
For this reason, the “following ability of focus adjustment” with respect to the moving subject is impaired, and there is a problem that the settling time of the focus adjustment is delayed.
The above problems can be improved to some extent by extremely narrowing the focus recognition range. However, if the in-focus recognition width is simply narrowed, hunting of the photographing optical system is caused. For this reason, it was necessary to balance the two, and it was very difficult to obtain a sufficient improvement effect.
[0012]
In order to solve such problems, the inventions described in claims 1 to 3 provide a focus adjustment device that can further reduce the remaining defocus amount while sufficiently suppressing hunting of the photographing optical system. The purpose is to do.
In addition to the object of claim 1, the inventions of claims 4 to 6 provide a focus adjustment device that can flexibly and appropriately determine the in-focus state in accordance with the detection state of the in-focus state. For the purpose.
[0013]
According to the seventh and eighth aspects of the present invention, in addition to the object of the first aspect, a focus adjustment device capable of flexibly changing the balance of the focusing accuracy and the focusing speed according to the shooting situation of the camera. The purpose is to provide.
[0014]
[Means for Solving the Problems]
FIG. 1 is a block diagram for explaining the inventions according to claims 1 to 8. Hereinafter, the solving means of the present invention will be described with reference to FIG.
[0015]
According to the first aspect of the present invention, the focus detection means 2 for detecting the focus state of the photographing optical system 1 and the “adaptability degree of the in-focus state” determined in advance in association with the focus state are obtained, and the suitability level is indicated. The focus determination means 3 that determines the in-focus state with the appearance probability, and when the in-focus state is determined by the in-focus determination means 3, the previous target drive position is maintained, and in other cases, the focus detection is performed. A target setting unit 4 for updating the target drive position based on the focus state detected by the unit 2 and a control unit 5 for driving and controlling the imaging optical system 1 according to the target drive position set by the target setting unit 4 are provided. Constitute.
[0016]
According to a second aspect of the present invention, in the first aspect of the invention, the in-focus determination means 3 obtains a “degree of suitability of the in-focus state” predetermined in association with the focus state, and the degree of fit and the random number. The in-focus state is determined based on the comparison with.
According to a third aspect of the present invention, in the first aspect of the invention, the in-focus determination means 3 obtains a random number distributed with a probability density equal to the magnitude of the “differential value of fitness according to the focus state”, and the random number and The in-focus state is determined based on the comparison with the focus state.
[0017]
According to a fourth aspect of the present invention, in the first aspect of the invention, the in-focus determination unit 3 selects or corrects the fitness according to the reliability information of the focus state detected by the focus detection unit 2. Features.
According to a fifth aspect of the present invention, in the focus adjustment apparatus according to the fourth aspect, when the focus determination unit 3 improves the reliability information of the focus state, the distribution width of the degree of fitness distributed corresponding to the focus state It is characterized by narrowing.
[0018]
In the invention described in claim 6, in the invention described in claim 4 or 5, the reliability information of the focus state is obtained by performing a correlation operation on a set of optical images obtained by dividing and forming the subject luminous flux. Or the minimum correlation amount, the moving speed of the subject image, or the contrast of the subject image.
The invention described in claim 7 is characterized in that, in the invention described in claim 1, the focus determination means 3 selects or corrects the fitness according to the setting state of the camera.
[0019]
In the invention described in claim 8, in the invention described in claim 7, the setting state of the camera is the setting state of the focus adjustment mode, the setting state of the film feeding mode, or the F value of the photographing optical system 1. Alternatively, it is a focal length of the photographing optical system 1.
[0020]
(Function)
In the focus adjustment apparatus according to the first aspect, the focus state (for example, defocus amount) of the photographing optical system 1 is detected via the focus detection means 2.
[0021]
In association with the focus state detected in this way, the “degree of focus state suitability” as shown in FIG. 2 is set in advance.
The focus determination unit 3 obtains a matching degree corresponding to the detection value of the focus state, and performs a focusing determination according to the appearance probability indicated by the matching degree.
That is, even when the detection value of the focus state takes the same value, there is a possibility that it is determined as both “in-focus state” and “out-of-focus state”. At this time, the ratio determined to be the in-focus state follows the appearance probability indicated by the fitness.
[0022]
Here, when it is determined as “in-focus state”, the target setting unit 4 maintains the previous target drive position.
On the other hand, when it is determined as “in-focus state”, the target setting unit 4 updates the value of the target drive position based on the detection value of the focus state.
By repeating such an update or non-update operation stochastically, the frequency at which the target drive position is updated gradually changes corresponding to the focus state, as shown in FIG.
[0023]
By adjusting the update frequency in this manner, the detection value of the focus state approaches the center focus point, so that the update time interval can be gradually increased. As a result, “minor vibration of the photographic optical system” (hunting) that occurs because the update interval of the target drive position is short is accurately suppressed.
On the other hand, since the update frequency of the target drive position changes gradually, the area where the target drive position is not updated at all can be made sufficiently narrow. Therefore, since the target drive position is repeatedly updated (although the update interval is long) even near the in-focus point, the remaining defocus amount is reliably reduced.
[0024]
Further, FIG. 4 shows a convolution integral of “the degree of suitability of the focused state” and “the probability distribution of the true focus state”. As shown in this figure, the actual focus recognition width is narrower than that of the conventional example (broken line shown in FIG. 4). In particular, the region (bottom portion) that is erroneously determined to be in focus is small while the focus state detection error remains large.
This is different from the conventional example (FIG. 18) in which the in-focus state is determined deterministically with the in-focus determination range as a boundary, and the ratio for determining the in-focus state is gradually increased from a small value. This is because it can be increased.
[0025]
Therefore, it is less likely that the focus state is erroneously detected while the focus state detection error remains large, and the remaining defocus amount is reliably reduced from this point.
Furthermore, since the region where the target drive position is not updated at all can be sufficiently narrowed, the dead zone (DeadZone) when performing focus control can be made as narrow as possible for the moving subject. As a result, the “focus adjustment followability” for the moving subject is improved, and the focus adjustment settling time is shortened.
[0026]
In the focus adjustment apparatus according to the second aspect, the focus determination unit 3 obtains a “degree of focus state suitability” that is predetermined in association with the focus state.
Next, the focus determination means 3 compares the degree of matching with a random number. Here, the probability that the random number falls below the fitness is equal to the probability indicated by the fitness.
By determining the in-focus state based on such a comparison result, the “ratio determined to be in-focus state” becomes equal to the “appearance probability indicated by the degree of fitness”. The focus adjustment apparatus according to claim 1 is realized by using such arithmetic processing.
[0027]
FIG. 5 shows a determination process for the focus adjustment apparatus according to the third aspect.
Here, the degree of suitability of the in-focus state (FIG. 5A) is defined as an ambiguous (fuzzy) value indicating how much the focus state fits into the in-focus state.
When this goodness of fit (a kind of probability distribution function) is differentiated on a number line representing the focus state, the magnitude of the differential value (FIG. 5B) is the probability density of the “focus state applicable to the in-focus state”. Indicates.
[0028]
The focus determination means 3 generates random numbers distributed at a probability density (FIG. 5C) indicated by the magnitude of the differential value on the “number line representing the focus state”.
When a ratio (probability distribution) distributed up and down with respect to an arbitrary focus state is obtained for random numbers distributed in such a form, it becomes equal to the fitness value corresponding to the focus state.
[0029]
By determining the focus state using such a random number as a boundary value (FIG. 5D), the “ratio determined to be in focus” becomes equal to the “appearance probability indicated by the fitness”. Using such a determination process, the focus adjustment apparatus according to claim 1 is realized.
In the focus adjusting apparatus according to the fourth aspect, the fitness is selected or corrected according to the reliability information of the focus state.
[0030]
In general, the “reliability for detecting the focus state” varies greatly according to the image pattern and moving speed of the subject. Along with such a change in reliability, the variation in detection of the focus state changes, and the occurrence rate of hunting changes greatly.
Therefore, by selecting or correcting the fitness according to the reliability information of the focus state, it is possible to flexibly and appropriately balance the hunting allowance and the focusing accuracy.
[0031]
In the focus adjustment apparatus according to the fifth aspect, the reliability information of the focus state is improved and the distribution width of the fitness is narrowed.
Usually, when the reliability information of the focus state is improved, the detection variation of the focus state is reduced. In such a state, the possibility of hunting occurring in the photographing optical system is low.
By narrowing the distribution of conformity in a timely manner in accordance with such hunting allowance, it is possible to improve the overall focusing accuracy.
[0032]
In the focus adjustment apparatus according to claim 6, as the reliability information of the focus state, the steepness of the correlation curve or the minimum correlation amount when the correlation calculation is performed on a set of optical images obtained by dividing and forming the subject light beam, Alternatively, at least one of the moving speed of the subject image or the contrast of the subject image is used.
[0033]
When the correlation curve has a high degree of steepness, the image pattern contains a lot of high-frequency and large-amplitude spatial frequency components, and the residual of the correlation amount becomes large when the spatial phase difference is slightly shifted. It is. In such a case, the reliability of focus detection increases.
Further, when the minimum correlation amount is small, the correlation is high for a set of split images. In such a case, the reliability of focus detection increases.
[0034]
Furthermore, when the moving speed of the subject image is low, the exposure flow of the subject image is reduced. In such a case, the reliability of focus detection increases.
In addition, when the contrast of the subject image is high, the image pattern includes a lot of high-frequency and large-amplitude frequency components, and a large residual amount of correlation occurs even if the phase difference in space is slightly shifted. In such a case, the reliability of focus detection increases.
[0035]
By determining “reliability of focus detection” based on the above values, it is possible to appropriately and easily select or correct the fitness.
In the focus adjustment apparatus according to the seventh aspect, the fitness level is selected or updated according to the setting state of the camera.
Usually, the focusing performance (focusing accuracy, focusing speed, etc.) required for the shooting situation differs depending on the setting state of the camera. Therefore, the focusing performance can be flexibly changed by changing the fitness distribution according to the setting state of the camera.
[0036]
In the focus adjustment apparatus according to claim 8, as the setting state, the setting state of the focus adjustment mode, the setting state of the film feeding mode, the F value of the photographing optical system 1, or the focal length of the photographing optical system 1 is set. Adopt at least one.
Hereafter, some examples of changing the fitness level will be shown (of course, depending on the design intention of the camera, the fitness level may be changed in the reverse direction).
[0037]
When the focus adjustment mode is a continuous mode (a mode in which focus adjustment is continuously performed in a state where the release is half-pressed), since the photo opportunity is given priority, the fitness distribution is widened. As a result, a quick focusing speed can be obtained.
When the focus adjustment mode is the single mode (the mode that locks the focus adjustment when the in-focus state is reached), the focus is given priority, and thus the distribution of the fitness is narrowed. As a result, high focusing accuracy can be obtained.
[0038]
When the focus adjustment mode is a manual focus adjustment mode (a mode in which focus adjustment is performed manually), the focus is given the highest priority, and therefore the distribution of fitness is narrowed. As a result, high focusing accuracy can be obtained.
When the film feeding mode is a mode that feeds and stops one frame at a time, focus is given priority, so the distribution of fitness is narrowed. As a result, high focusing accuracy can be obtained.
[0039]
When the film feeding mode is the continuous shooting mode, priority is given to the photo opportunity, so the distribution of fitness is widened. As a result, a quick focusing speed can be obtained.
When the F value (open F value or photographing F value) of the photographic optical system 1 is low, the depth of field is deep and the focusing accuracy is not required to be high. As a result, a quick focusing speed can be obtained.
[0040]
When the F value of the photographic optical system 1 is high, since the depth of field is narrow, a high focusing accuracy is required, so the fitness distribution is narrowed. As a result, high focusing accuracy can be obtained.
When the focal length of the photographing optical system 1 is short, since the depth of field is deep, high focusing accuracy is not required, so the distribution of fitness is widened. As a result, a quick focusing speed can be obtained.
[0041]
When the focal length of the photographic optical system 1 is long, since the depth of field is narrow, a high focusing accuracy is required, so the fitness distribution is narrowed. As a result, high focusing accuracy can be obtained.
By such a change in the degree of adaptation, it is possible to appropriately obtain a focusing performance that is different for each photographing situation.
[0042]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 6 is a diagram showing a first embodiment (corresponding to claims 1 and 2).
In the figure, a main mirror 13 and a sub mirror 14 are disposed on the optical axis of the taking lens 11. An AF module 15 is arranged in the reflection direction of the sub mirror 14.
[0043]
The photoelectric output of the AF module 15 is connected to the input / output terminal of the microprocessor 17 via the sensor drive circuit 16. The input terminal of the microprocessor 17 is individually connected to a lens information storage circuit 18 in the photographing lens 11, an encoder 20 for reading the lens position of the photographing lens 11, and an operation member 23 including a release button.
[0044]
The output terminal of the microprocessor 17 is connected to the motor 21 via the motor control circuit 19. The driving force of the motor 21 is transmitted to the lens moving mechanism 22 on the photographing lens 11 side via the lens mount portion.
As for the correspondence relationship between the first and second embodiments of the present invention, the focus detection means 2 corresponds to the focus detection function of the AF module 15 and the microprocessor 17, and the focus determination means 3 Corresponding to the focus determination function of the microprocessor 17, the target setting means 4 corresponds to the target value update function of the microprocessor 17, and the control means 5 corresponds to the microprocessor 17, the motor 21, the lens moving mechanism 22 and the encoder 20. .
[0045]
7 to 9 are flowcharts for explaining the operation of the first embodiment.
Hereinafter, the operation of the first embodiment will be described with reference to these drawings.
First, when the power supply on the camera side is turned on, the microprocessor 17 initializes the memory and the flag (step S1).
Here, when the release button is half-pressed (step S2), the microprocessor 17 causes the focus detection CCD in the AF module 15 to start accumulating photocharges (step S3).
[0046]
During this accumulation operation, the microprocessor 17 counts the feedback pulses from the encoder 20, and obtains the average lens position LPint at the accumulation center time t0 shown in FIG.
Furthermore, the microprocessor 17 executes data communication with the lens information storage circuit 18 at the accumulation center time t0, and the lens information at the accumulation center time t0 (the conversion coefficient LD of the defocus amount and the lens driving amount, the open F). Value).
[0047]
On the other hand, the photocharge accumulated in the focus detection CCD is transferred as an analog image signal, subjected to A / D conversion, and stored in the memory (step S4).
The microprocessor 17 performs a known correlation operation on the image signal thus captured to calculate a defocus amount DF0 (step S5).
Here, the microprocessor 17 uses “defocus amount DF0”, “average lens position LPint”, and “conversion coefficient LD between the defocus amount and the lens drive amount”,
P0 = LPint + LD · DF0 (Formula 1)
Is calculated to obtain the target drive position P0 (step S6).
[0048]
Subsequently, an in-focus determination routine is executed (step S7).
Hereinafter, the details of the focus determination routine will be described with reference to FIG.
First, when the defocus amount DF0 exceeds the predetermined value IFth2 (step S11), the microprocessor 17 stops determining the in-focus state. Generally, the predetermined value IFth2 is set to a value of about 400 μm to 1 mm.
[0049]
When the defocus amount DF0 is equal to or smaller than the predetermined value IFth2, the microprocessor 17 obtains the lens position LPinf at the in-focus determination time tinf.
Next, using “lens position LPinf”, “target drive position P0” and “conversion coefficient LD between defocus amount and lens drive amount”,
DFinf = (P0−LPinf) / LD
And a defocus amount DFinf at the in-focus determination time tinf shown in FIG. 10B is obtained (step S12).
[0050]
In this state, the microprocessor 17 obtains the “focus state fitness IFth1” corresponding to the defocus amount DFinf based on the correspondence shown in FIG. 11 (step S13).
Here, the correspondence relationship shown in FIG. 11 defines how much the defocus amount DFinf representing the focus state is applied to the in-focus state with a fitness IFth1 of 0 to 1.
[0051]
For example, when the defocus amount DFinf is 100 μm or more, the fitness IFth1 = 0, and when the defocus amount DFinf is 50 μm or less, the fitness IFth1 = 1. When the defocus amount DFinf is 50 to 100 μm, the fitness IFth1 takes an intermediate value of 0 to 1.
Next, the microprocessor 17 generates randomly distributed random numbers RND (0 ≦ RND ≦ 1) (step S14).
[0052]
When the random number RND falls below the fitness IFth1 (step S15), the microprocessor 17 determines that the focus state is in focus and sets a focus flag (step S16).
On the other hand, when the random number RND exceeds the fitness level IFth1 (step S15), the microprocessor 17 determines that the in-focus state has occurred and resets the focus flag (step S17).
[0053]
By such a determination operation, the ratio determined to be in focus is equal to the appearance probability indicated by the fitness IFth1.
Subsequently, a target drive position update routine is executed.
Hereinafter, the details of the update routine will be described with reference to FIG.
First, when the focus flag is in a reset state (step S21), the current target drive position is updated to “the latest target drive position obtained in step S6” (step S22).
[0054]
On the other hand, when the focus flag is in the set state (step S21), it is determined whether or not the lens moving speed of the taking lens 11 is equal to or less than a predetermined value (step S23).
Here, when the lens moving speed exceeds a predetermined value, there is a high possibility that the photographing lens 11 will move away from the target drive position, so the current target drive position is updated to “the latest target drive position obtained in step S6”. (Step S22).
[0055]
When the lens moving speed is equal to or lower than the predetermined value, the current target drive position is maintained as it is (step S24).
Based on the target drive position determined through such an update routine, the extension amount of the photographic lens 11 is controlled (step S9).
The above operation returns to step S2 and is repeated.
[0056]
By the operation described above, in the first embodiment, the update interval of the target drive position gradually changes according to the defocus amount DFinf.
Therefore, the region where the target drive position is not updated at all can be sufficiently narrowed. Therefore, even near the focal point (although the update interval becomes longer), the target drive position is repeatedly updated, and the remaining defocus amount can be reliably reduced.
[0057]
Further, as shown in FIG. 4, since the distribution of the in-focus recognition width is narrowed, the region (the base portion) that is erroneously determined as the in-focus state can be reduced while the focus state detection error remains large. .
[0058]
Therefore, it is less likely that the focus state is erroneously detected while the focus state detection error remains large. From this point, the remaining defocus amount can be reliably reduced.
Furthermore, since the update interval of the target drive position can be sufficiently opened in the vicinity of the focal point, hunting that has occurred due to the short update interval can be reliably suppressed.
[0059]
Further, since the in-focus state is simply determined by comparing the random number value RND with the fitness level IFth1, the amount of calculation processing of the microprocessor 17 can be reduced.
Next, another embodiment will be described.
FIG. 12 is a diagram showing an in-focus determination routine in the second embodiment (corresponding to claims 1, 2, 4 to 6).
[0060]
Note that the overall configuration of the second embodiment is the same as that of the first embodiment except for the focus determination function of the microprocessor 17, and therefore the description thereof is omitted here.
Further, regarding the correspondence relationship between the invention described in claims 1, 2, 4 to 6 and the second embodiment, the focus detection means 2 corresponds to the focus detection function of the AF module 15 and the microprocessor 17 and is in focus. The determination means 3 corresponds to the focus determination function of the microprocessor 17, the target setting means 4 corresponds to the target update function of the microprocessor 17, and the control means 5 is the microprocessor 17, the motor 21, the lens moving mechanism 22 and the encoder 20. Corresponding to
[0061]
Hereinafter, based on FIG. 12, the operation | movement of the focusing determination in 2nd Embodiment is demonstrated.
First, the microprocessor 17 compares the defocus amount DF0 with the predetermined value IFth2 (step S31), and then calculates the defocus amount DFinf at the focus determination time tinf (step S32).
Here, the microprocessor 17 captures the reliability information of the focus state. This reliability information is a value indicating the reliability of the defocus amount. For example, the steepness (slope) of the correlation curve (FIG. 13) obtained when the correlation calculation is performed on the image signal of the focus detection CCD, The minimum correlation amount, the moving speed of the subject image, or the contrast of the subject image is used.
[0062]
If the reliability of the defocus amount is low due to such reliability information, the fitness level A (FIG. 14) having a generally high fitness level is selected.
When the reliability of the defocus amount is high, the fitness B (FIG. 14) having a generally low fitness is selected (step S33).
As described above, after the fitness is selected based on the reliability information of the defocus amount, the in-focus state is determined in the same manner as in the first embodiment (steps S34 to S38).
Through the operation described above, the second embodiment can obtain the same effects as those of the first embodiment.
[0063]
Furthermore, in the second embodiment, when the reliability of the defocus amount is high, the focusing accuracy can be improved by making use of the hunting margin by narrowing the distribution of the fitness.
Further, when the reliability of the defocus amount is low, hunting can be reliably prevented by widening the distribution of fitness.
[0064]
Next, another embodiment will be described.
FIG. 15 is a diagram showing an in-focus determination routine in the third embodiment (corresponding to claims 1, 2, 7, and 8).
Note that the overall configuration of the third embodiment is the same as that of the first embodiment except for the focus determination function of the microprocessor 17, and thus the description thereof is omitted here.
[0065]
As for the correspondence relationship between the invention described in claims 1, 2, 7, and 8 and the third embodiment, the focus detection means 2 corresponds to the focus detection function of the AF module 15 and the microprocessor 17 and is in focus. The determination means 3 corresponds to the focus determination function of the microprocessor 17, the target setting means 4 corresponds to the target update function of the microprocessor 17, and the control means 5 is the microprocessor 17, the motor 21, the lens moving mechanism 22 and the encoder 20. Corresponding to
[0066]
Hereinafter, the operation of focusing determination in the third embodiment will be described with reference to FIG.
First, the microprocessor 17 compares the defocus amount DF0 with the predetermined value IFth2 (step S41), and then calculates the defocus amount DFinf at the focus determination time tinf (step S42).
Here, the microprocessor 17 captures the setting state of the camera. As the setting state of the camera, the setting state of the focus adjustment mode, the setting state of the film feeding mode, the F value of the photographing optical system 1, the focal length of the photographing optical system 1, or the like is used.
[0067]
In such a camera setting state, when a focusing speed is required, a fitness level A (FIG. 14) having a generally high fitness level is selected.
If the focusing accuracy is required, the fitness B (FIG. 14) having a generally low fitness is selected (step S43).
As described above, after the degree of fitness is selected according to the setting state of the camera, the in-focus state is determined in the same manner as in the first embodiment (steps S44 to S48).
[0068]
By the operation described above, the third embodiment can obtain the same effects as those of the first embodiment.
Furthermore, as an effect peculiar to the third embodiment, it is possible to flexibly adapt to the setting state of the camera and obtain the required focusing performance as appropriate.
Next, another embodiment will be described.
[0069]
FIG. 16 is a diagram showing a focus determination routine in the fourth embodiment (corresponding to claims 1 and 3).
Note that the overall configuration of the fourth embodiment is the same as that of the first embodiment except for the focus determination function of the microprocessor 17, and thus the description thereof is omitted here.
[0070]
Further, regarding the correspondence relationship between the first and third aspects of the invention and the fourth embodiment, the focus detection means 2 corresponds to the focus detection function of the AF module 15 and the microprocessor 17, and the focus determination means 3 Corresponding to the focus determination function of the microprocessor 17, the target setting means 4 corresponds to the target update function of the microprocessor 17, and the control means 5 corresponds to the microprocessor 17, the motor 21, the lens moving mechanism 22 and the encoder 20.
[0071]
Hereinafter, the operation of focusing determination in the fourth embodiment will be described with reference to FIG.
First, when the defocus amount DF0 exceeds the predetermined value IFth2 (step S51), the microprocessor 17 stops determining the in-focus state.
If the defocus amount DF0 is equal to or smaller than the predetermined value IFth2, the microprocessor 17 obtains the defocus amount DFinf at the in-focus determination time tinf (step S52).
[0072]
Here, the microprocessor 17 is based on a uniformly distributed random number RND (0 ≦ RND ≦ 1),
IFth3 = IFmin + RND ・ (IFmax−IFmin)
Is calculated and the current in-focus authorization range IFth3 is determined (steps S53 and S54).
Here, when the magnitude of the defocus amount DFinf is less than the in-focus authorized width IFth3 (step S55), the microprocessor 17 determines that the in-focus state is set and sets the in-focus flag (step S56).
[0073]
On the other hand, when the defocus amount DFinf exceeds the in-focus recognition width IFth3 (step S55), the in-focus state is determined and the in-focus flag is reset (step S57).
By such a determination operation, the ratio determined to be the in-focus state becomes equal to the appearance probability indicated by the fitness shown in FIG.
[0074]
By the operation described above, the same effect as that of the first embodiment can be obtained also in the fourth embodiment.
In each of the embodiments described above, the slope of the fitness is linear, but the present invention is not limited to this, and the slope of the fitness may be curved, broken, or stepped.
[0075]
Moreover, in each embodiment mentioned above, although the range of the conformity is set to 0-1, since it is not a probability value, it is not limited to the range of such a value, It can take the range of arbitrary values. it can. For example, the fitness may be an integer value in the range of 0-255.
Furthermore, in each of the embodiments described above, the defocus amount is used as the focus state, but the present invention is not limited to this, and any amount that represents the focus state may be used. For example, the difference between the “shooting distance of the shooting optical system” and the “distance value to the subject”, the contrast value of the subject image, and the like can be used.
[0076]
In the second embodiment and the third embodiment, the two matching degrees A and B are selected, but the present invention is not limited to this. For example, one of two or more fitness levels may be selected according to the reliability information or the camera setting state, and a new value can be obtained by performing correction such as interpolation processing on these fitness levels. The goodness of fit may be synthesized.
[0077]
【The invention's effect】
As described above, in the first aspect of the present invention, the update interval of the target drive position can be gradually changed, so that the update interval of the target drive position can be sufficiently opened in the vicinity of the focal point. Therefore, it is possible to sufficiently suppress “minor vibration of the photographing optical system” (hunting) that has occurred because the update interval of the target drive position is short.
[0078]
On the other hand, since the update frequency of the target drive position gradually changes, the region where the target drive position is not updated at all can be made as narrow as possible. Therefore, since the update of the target drive position is repeated even near the focal point (although the update interval is somewhat long), the remaining defocus amount can be reliably reduced.
[0079]
Further, as shown in FIG. 4, since the distribution of the actual focus recognition width can be narrowed, a region (base portion) that is erroneously determined to be in focus with a large focus state detection error remains. It can be made sufficiently small. Also from this point, the remaining defocus amount can be surely reduced.
Furthermore, since the area where the target drive position is not updated at all can be sufficiently narrowed, the dead zone (DeadZone) when performing focus control can be made as narrow as possible for the moving subject. Accordingly, the “focus adjustment followability” for the moving subject is improved, and the focus adjustment settling time can be shortened.
[0080]
In the focusing apparatus according to claim 2, the degree of matching and the random number are compared in magnitude. Since the probability that such a random number value falls below the goodness of fit becomes equal to the appearance probability indicated by the goodness of fit, the focused state is determined according to the appearance probability indicated by the goodness of fit.
Therefore, the focus adjustment apparatus according to claim 1 can be accurately realized based on simple arithmetic processing.
[0081]
In the focus adjustment apparatus according to claim 3, a random number having a probability density indicated by the magnitude of the differential value of the “degree of focus state suitability” is obtained, and the focus determination is performed based on a comparison between the random number and the focus state. Do.
Such a probability distribution of random numbers is equal to the appearance probability indicated by the fitness. Therefore, the ratio determined to be in focus can be made equal to the appearance probability indicated by the fitness.
[0082]
Therefore, the focus adjustment apparatus according to claim 1 can be accurately realized based on simple arithmetic processing.
In the focus adjusting apparatus according to the fourth aspect, the fitness is selected or corrected according to the reliability information of the focus state.
Normally, the detection variation of the focus state varies depending on the reliability information of the focus state, and the occurrence rate of hunting changes greatly.
[0083]
Therefore, by selecting or changing the degree of fitness according to the focus state reliability information, it is possible to flexibly and appropriately balance the hunting allowance and the focusing accuracy.
In the focus adjusting apparatus according to the fifth aspect, the reliability information of the focus state is improved and the distribution of the fitness is narrowed. Therefore, according to the hunting allowance, the fitness distribution can be narrowed in a timely manner, and the overall focusing accuracy can be improved.
[0084]
In addition, when the reliability information is low, it is possible to widen the distribution of conformity in a timely manner and reliably prevent hunting.
In the focus adjustment apparatus according to claim 6, as the reliability information of the focus state, the steepness of the correlation curve or the minimum correlation amount when the correlation calculation is performed on a set of optical images obtained by dividing and forming the subject light beam, Alternatively, at least one of the moving speed of the subject image or the contrast of the subject image is used.
[0085]
Therefore, it is possible to determine “reliability of focus detection” appropriately and simply, and to select or correct the degree of fitness accurately.
In the focus adjustment apparatus according to the seventh aspect, the fitness level is selected or updated according to the setting state of the camera.
Usually, the focusing performance (focusing accuracy, focusing speed, etc.) required for the shooting situation varies depending on the setting state of the camera. Therefore, it is possible to appropriately respond to the request for focusing performance (focusing accuracy and focusing speed) by changing the distribution of the matching degree according to the setting state of the camera.
[0086]
In addition, since these focusing performances are automatically switched in conjunction with the setting state of the camera, it is not necessary for the photographer to operate with consciousness, and operability can be improved.
In the focus adjustment apparatus according to claim 8, as the setting state, the setting state of the focus adjustment mode, the setting state of the film feeding mode, the F value of the photographing optical system 1, or the focal length of the photographing optical system 1 is set. Adopt at least one.
[0087]
Therefore, it is possible to promptly respond to the demands for different focusing performances for each set state.
Further, since the focusing performance is automatically switched in conjunction with the setting state of these cameras, there is no need for the photographer to operate with consciousness, and operability can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining an invention according to claims 1 to 8;
FIG. 2 is a diagram illustrating a degree of adaptation (setting example) of an in-focus state.
FIG. 3 is a diagram illustrating the update frequency of a target drive position.
FIG. 4 is a diagram for explaining a change in a focus recognition width.
FIG. 5 is a block diagram for explaining an invention according to claim 3;
FIG. 6 is a diagram showing a first embodiment (corresponding to claims 1 and 2);
FIG. 7 is a diagram illustrating a main flowchart of focus adjustment.
FIG. 8 is a focus determination routine in the first embodiment.
FIG. 9 is a diagram showing a target drive position update routine.
FIG. 10 is a diagram illustrating calculation of a lens position.
FIG. 11 is a diagram illustrating an example of setting a fitness level in the first embodiment.
FIG. 12 is a diagram showing an in-focus determination routine in the second embodiment (corresponding to claims 1, 2, 4 to 6).
FIG. 13 is a diagram showing reliability information of a focus state.
FIG. 14 is a diagram illustrating a setting example of fitness according to the second embodiment.
FIG. 15 is a view showing an in-focus determination routine according to a third embodiment (corresponding to claims 1, 2, 7, and 8);
FIG. 16 is a diagram showing an in-focus determination routine in the fourth embodiment (corresponding to claims 1 and 3);
FIG. 17 is a diagram showing a focus authorization width in the fourth embodiment.
FIG. 18 is a diagram showing a conventional in-focus recognition range.
FIG. 19 is a diagram for explaining a change in a focus recognition width in a conventional example.
[Explanation of symbols]
1 Shooting optics
2 Focus detection means
3 Focus determination means
4 Target setting means
5 Control means
11 Shooting lens
13 Main mirror
14 Submirror
15 AF module
16 Sensor drive circuit
17 Microprocessor
18 Lens information storage circuit
19 Motor control circuit
20 Encoder
21 Motor
22 Lens movement mechanism
23 Operation members

Claims (8)

Focus detection means for detecting the focus state of the imaging optical system;
Corresponding to the focus state, a predetermined “in-focus state adaptability” is obtained, and an in-focus determination means for determining the in-focus state with an appearance probability indicated by the adaptability;
When the in-focus state is determined by the in-focus determination unit, the previous target drive position is maintained; otherwise, the target drive position is updated based on the focus state detected by the focus detection unit. Setting means;
A focus adjustment apparatus comprising: control means for driving and controlling the photographing optical system in accordance with a target drive position set by the target setting means. In the invention of claim 1,
The focus determination means includes
A focus adjustment device that obtains a “degree of matching of a focused state” that is determined in advance in association with the focus state, and determines the focused state based on a comparison between the degree of matching and a random number. In the invention of claim 1,
The focus determination means includes
A random number distributed is obtained at a probability density indicated by the magnitude of the “derivative value of the goodness of fit according to the focus state”, and the focus state is determined based on a comparison between the random number and the focus state. Focusing device. In the invention of claim 1,
The focus determination means includes
The focus adjustment device, wherein the fitness is selected or corrected according to reliability information of a focus state detected by the focus detection means. The focus adjustment apparatus according to claim 4.
The focus determination means includes
A focus adjustment device that narrows the distribution width of the fitness distributed according to the focus state when reliability information of the focus state is improved. In the invention according to claim 4 or claim 5,
The focus state reliability information is
A focus characterized by the steepness or minimum correlation amount of a correlation curve, the moving speed of a subject image, or the contrast of a subject image when performing a correlation calculation on a set of optical images obtained by dividing and forming a subject luminous flux. Adjusting device. In the invention of claim 1,
The focus determination means includes
A focus adjustment apparatus that selects or corrects the fitness according to a setting state of a camera. In the invention of claim 7,
What is the setting state of the camera?
A focus adjustment apparatus characterized by a setting state of a focus adjustment mode, a setting state of a film feeding mode, an F value of a photographing optical system, or a focal length of a photographing optical system.

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