JPH11177872A - Electronic camera with focus detection function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To flexibly and appropriately execute the reliability judgement of a focus detected result matched with the exchange of an image pickup unit in an electronic camera with focus detection function. SOLUTION: In this electronic camera with a focus detection function provided with an image pickup means 1 for picking up optical images formed by a photographing optical system Z and outputting the image signals, a focus detection means 2 for detecting the focus adjustment state of the photographing optical system Z and a reliability judgement means 3 for judging reliability for the detected result of the focus detection means 2 and judging whether or not a focus is detectable, a reliability reference change means 5 for changing the judgement reference of the reliability judgement means 3 corresponding to the picture element density of the image pickup means 1 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic camera having a focus detection function. In particular, the present invention relates to an electronic camera that changes a focus detection setting value in accordance with replacement of an imaging unit.

[0002]

2. Description of the Related Art There is known an electronic camera which performs image pickup using a CCD image pickup device or the like instead of a silver halide film.
In this type of electronic camera, focus detection is performed using a known phase difference detection method, a passive distance measurement method, a contrast detection method, or the like.

Hereinafter, a focus detection operation in the phase difference detection method will be described. FIG. 8 is a diagram illustrating the configuration of the focus detection module. In FIG. 8, the photographing optical system 70
A part of the light beam passing through reaches the field mask 71 via a sub-mirror or the like (not shown). This visual field mask 71
Is located near the image plane of the imaging optical system 70 and determines the focus detection area. Behind this field mask 71,
An aperture mask 73 is arranged via a field lens 72. The aperture mask 73 has a pair of openings 73a,
73b is provided, and pupil-divides the light beam passing through the imaging optical system 70.

[0004] The pair of split light beams thus pupil-divided are tilted and imaged through a pair of re-imaging lenses 74a and 74b to form a pair of light images. A focus detection sensor 75 is disposed on the image forming plane of the pair of light images. In such a configuration, a pair of light images are photoelectrically converted in the rows A and B of the focus detection sensor 75, respectively. By performing a correlation operation on the photoelectrically converted optical image pattern while shifting the interval, the image interval between the pair of optical images is detected.

[0005] Based on the image interval between the pair of light images, the focus adjustment state (for example, the defocus amount) of the photographing optical system 70.
Can be calculated. On the camera side, automatic focus control, display of a focus adjustment state, and the like are performed based on the defocus amount calculated in this manner. By the way, when the detected value of the defocus amount becomes zero by the automatic focus control, it can be determined that the imaging optical system 70 is in a focused state.

However, since various noises are mixed in the actual defocus amount, the defocus amount is not always completely zero. For this reason, the imaging optical system 70 does not stop even when the focusing point is reached, which causes a problem that the imaging optical system 70 generates minute vibration near the focusing point. Therefore, in practice, a range that can be recognized as a focused state (hereinafter, referred to as a “focusing recognized range”) is determined in advance according to the depth of focus of the imaging optical system 70. The state in which the defocus amount falls within the in-focus recognition range is determined as the in-focus state, and is set as the target when the automatic focus control is stopped.

[0007] By such a focus determination, a minute vibration does not occur in the photographing optical system 70 near the focal point.
The focusing speed can be further improved. In the case of a low-contrast subject, there is no significant difference in the result of the correlation operation between the pair of light images. For this reason, it is difficult to detect the image interval between the pair of optical images with high accuracy, and the detection accuracy of the defocus amount decreases. In such a case, proper automatic focusing cannot be expected.

Therefore, conventionally, the reliability of the focus detection result is determined based on the following procedure. First, as the numerical value indicating the reliability of the focus detection result, the contrast amount of the subject, the above-described correlation operation result, and the like are obtained (hereinafter, referred to as the following).
A numerical value indicating such reliability directly or indirectly is referred to as “reliability”).

The reliability of the focus detection result is determined by determining the reliability based on a predetermined threshold.
In such a reliability determination, it is determined that the focus can be detected only when the threshold is determined as “reliable”, and the automatic focus control is performed based on the defocus amount. On the other hand, when the threshold is determined to be “no reliability”, it is determined that focus detection is impossible, and the automatic focus control based on the defocus amount is not executed.

With such an operation, it is possible to reliably prevent inappropriate automatic focus control.

[0011]

However, in the case of an electronic camera, the required image quality varies greatly depending on the intended use. For example, in the case of photographing on the premise of print output, it is preferable that the image data has the highest possible resolution. On the other hand, in the case of photographing on the premise that the image data is to be posted on a homepage on the Internet, the image data often has a low resolution due to the transfer rate.

Therefore, when the image pickup device is fixedly mounted on the electronic camera, there arises a problem that the quality of the image required by the photographer is excessively high or only an image of low quality is obtained. . Therefore, the present applicant has considered an electronic camera in which a plurality of imaging units having different types and performances are prepared, and these imaging units can be appropriately replaced and mounted. By replacing such an imaging unit, the photographer can enjoy various shooting variations,
The range of use of electronic cameras is greatly expanded.

By the way, when the imaging unit is replaced,
The image quality of the image data to be captured greatly changes. In such imaging with different image qualities, it is inappropriate to uniformly perform the focus detection operation and the focus control operation. Therefore, in the inventions according to claims 1 to 5,
It is an object of the present invention to provide an electronic camera that can flexibly and appropriately determine the reliability of a focus detection result even when the pixel density of an imaging unit is changed.

It is another object of the present invention to provide an electronic camera which can flexibly and properly determine the focus of the focus detection result even when the pixel density of the image pickup means is changed. I do.

[0015]

FIG. 1 is a principle block diagram for explaining the first to fifth aspects of the present invention. The means for solving the problem will be described below in association with the reference numbers shown in FIG.

According to a first aspect of the present invention, there is provided an image pickup means for picking up an optical image formed by a photographing optical system and outputting an image signal; An electronic camera with a focus detection function, comprising: a focus detection unit 2 for detecting; and a reliability determination unit 3 for performing reliability determination on the detection result of the focus detection unit 2 and determining whether or not focus detection is possible. The pixel density of the imaging unit 1 can be changed, and a reliability criterion changing unit 5 that changes the criterion of the reliability determining unit 3 according to the pixel density of the imaging unit 1 is provided.

According to a second aspect of the present invention, there is provided an electronic camera with a focus detection function according to the first aspect, wherein the image pickup exchange mechanism for interchangeably mounting the image pickup means having different pixel densities. The reliability criterion changing unit 5 obtains data on the pixel density from the imaging unit 1 via the imaging exchange mechanism 4 and changes the criterion of the reliability determining unit 3 according to the obtained data. Features.

With such a configuration, in the electronic camera according to the second aspect, by replacing the image pickup means 1 with the image pickup exchange mechanism 4, it is possible to flexibly change the criterion for determining reliability. (Claim 3) The invention according to claim 3 is the electronic camera with the focus detection function according to claim 1 or 2, wherein the reliability criterion changing means 5 is a pixel density of the imaging means 1 in use. Is characterized by changing to a criterion that demands higher reliability as the value becomes higher.

In general, when the pixel density of the image pickup means 1 is low, fine blur to a certain extent is picked up within a range of about one pixel, so that it is not perceived as out of focus by human eyes.
Conversely, when the pixel density of the imaging unit 1 is high, a fine blur shape is accurately imaged by a large number of pixels. For these reasons,
As the pixel density of the imaging means 1 increases, the practically acceptable circle of confusion (the maximum blur diameter that is not recognized as defocusing by human eyes) decreases, and the depth of focus decreases. Therefore, as the pixel density of the imaging unit 1 increases, higher precision is required for focus control.

Therefore, in the electronic camera according to the third aspect, when the imaging means 1 having a high pixel density is used, the criterion for determining the reliability is a criterion for requesting high reliability (hereinafter, referred to as a criterion).
Change the setting to “high judgment criteria”). By such a setting change, only a focus detection result that passes a high determination criterion is determined to be “reliable”, and it is determined that focus detection is possible.

Conversely, when the image pickup means 1 having a low pixel density is used, the electronic camera according to the third aspect sets the criterion for determining reliability as a criterion for permitting low reliability (hereinafter referred to as a criterion).
"Lower criterion"). Due to such a setting change, the number of cases where it is determined that focus detection is possible increases, and a focus adjustment operation and a display of a focus adjustment state are performed for a wider range of subjects.

According to a fourth aspect of the present invention, in the electronic camera with a focus detection function according to the first to third aspects, the reliability determining means 3 determines a contrast amount of the subject. Thus, the present invention is characterized in that it is means for determining the reliability of the focus detection result. According to a fifth aspect of the present invention, in the electronic camera with the focus detection function according to any one of the first to third aspects, the focus detection means 2 pupil-divides the subject light into a pair of light images. Focus detection optical system for forming the image, and focus detection imaging means 1 for capturing a pair of optical images formed by the focus detection optical system
And a focus calculation unit that calculates a defocus amount based on a phase difference between the “pair of optical images” imaged by the focus detection imaging unit 1. It is a means for determining the reliability of the focus detection result by determining the degree of coincidence.

FIG. 2 is a block diagram showing the principle of the present invention. Hereinafter, means for solving the problem will be described in association with reference numbers shown in FIG. (Claim 6) According to a sixth aspect of the present invention, there is provided an image pickup means 1 for picking up an optical image formed by the photographing optical system Z and outputting an image signal, and a focus for detecting a focus adjustment state of the photographing optical system Z. In an electronic camera with a focus detection function provided with a detection means 2 and a focus determination means 7 for performing a focus determination on a detection result of the focus detection means 2, the focus determination means depends on the pixel density of the imaging means 1. And a focusing criterion changing means 8 for changing the criterion 7.

(Claim 7) According to a seventh aspect of the present invention, in the electronic camera with the focus detection function according to the sixth aspect, the image pickup exchange mechanism 4 in which the image pickup means 1 having different pixel densities are exchangeably mounted. The focusing criterion changing means 8 obtains data relating to the pixel density from the imaging means 1 via the imaging exchange mechanism 4, and changes the criterion of the focusing determining means 7 according to the obtained data. Features.

With such a configuration, in the electronic camera according to the seventh aspect, by replacing the imaging means 1 with the imaging exchange mechanism 4, it is possible to flexibly change the criterion of the focus determination. (Claim 8) The invention according to claim 8 is the electronic camera with the focus detection function according to claim 6 or 7, wherein the focus reference changing means 8 is a pixel density of the imaging means 1 in use. Is changed to a criterion that requires a higher focusing accuracy as the value becomes higher.

In general, when the pixel density of the image pickup means 1 is low, fine blur to a certain extent is picked up within a range of about one pixel, so that it is not perceived as out of focus by human eyes.
Conversely, when the pixel density of the imaging unit 1 is high, a fine blur shape is accurately imaged by a large number of pixels. For these reasons,
As the pixel density of the imaging means 1 increases, the practically acceptable circle of confusion (the maximum blur diameter that is not recognized as defocusing by human eyes) decreases, and the depth of focus decreases. Therefore, as the pixel density of the imaging unit 1 increases, higher focus accuracy is required for focus control.

Therefore, in the electronic camera according to the present invention, when the image pickup means 1 having a high pixel density is used, the criterion for determining the focusing is determined by a criterion for requesting a high focusing accuracy (hereinafter referred to as a criterion).
Change the setting to “high judgment criteria”). as a result,
The focusing accuracy of the focus adjustment is increased. Conversely, when the imaging unit 1 with a low pixel density is used, the criterion for the focus determination is changed to a criterion that allows a low focusing accuracy (hereinafter, referred to as a “low criterion”). As a result, the focusing accuracy of the focus adjustment is appropriately reduced, and the focusing speed and the like are increased instead.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. In addition, this embodiment is Claim 1-
This is an embodiment corresponding to the invention described in FIG. (Configuration of the present embodiment) FIG. 3 is a diagram showing the configuration of the present embodiment.

In FIG. 3, a photographing optical system 12 is mounted on the electronic camera 11. A mirror box including a main mirror 13 and a sub-mirror 14 is arranged along the optical axis of the photographing optical system 12. A focus detection module 15 is arranged in the reflection direction of the sub mirror 14. Inside the focus detection module 15, a field mask 71, a field lens 72, an aperture mask 73, re-imaging lenses 74a and 74b, a focus detection sensor 75, and the like shown in FIG.

An output of the focus detection module 15 is connected to an A / D input terminal of the camera CPU 16. The control output of the camera-side CPU 16 is connected to a motor 17 for moving the photographing optical system 12 back and forth. On the other hand, on the back of the electronic camera 11, an image pickup exchange mechanism 11a for detachably mounting the image pickup unit 18 is provided. The image pickup unit 18 includes an image pickup device 19, an image pickup unit side CPU 20, a memory 21, and the like.

The imaging unit-side CPU 20 and the camera-side CPU 16 perform data communication via a contact terminal or the like provided on the imaging exchange mechanism 11a. (Correspondence between each claim and this embodiment) Hereinafter, the correspondence between each claim and this embodiment will be described. First, regarding the correspondence between the invention described in the first, third, fourth, and fifth embodiments and the present embodiment, the imaging unit 1 corresponds to the imaging unit 18, and the focus detection unit 2 includes the focus detection module 15 and the camera-side CPU 16. , The reliability determination means 3 corresponds to the "function of performing reliability determination" of the camera-side CPU 16, and the reliability criterion changing means 5 corresponds to the "imaging unit 18" of the camera-side CPU 16. From image sensor 1
9 of acquiring the pixel density data and changing the reliability criterion ”.

As for the correspondence between the invention described in claim 2 and the present embodiment, in addition to the above-mentioned correspondence, the imaging exchange mechanism 4 corresponds to the imaging exchange mechanism 11a. Claims 6 and 8
As for the correspondence between the invention described in (1) and this embodiment, the imaging unit 1 corresponds to the imaging unit 18 and the focus detection unit 2
Corresponds to the “function of performing focus detection calculation” of the focus detection module 15 and the camera-side CPU 16,
Corresponds to the “function of performing focus determination” of the camera-side CPU 16, and the focus reference changing unit 8 acquires “pixel density data of the image sensor 19 from the image pickup unit 18 of the camera-side CPU 16, and sets the reliability determination criterion. Function to change ".

As for the correspondence between the invention described in claim 7 and the present embodiment, in addition to the above-mentioned correspondence, the imaging exchange mechanism 4 corresponds to the imaging exchange mechanism 11a. (Explanation of Operation of the Present Embodiment) FIG. 4 is a flowchart for explaining the operation of the camera-side CPU 16 in the present embodiment.

The operation of this embodiment will be described below with reference to FIG. First, the camera-side CPU 16 performs data communication with the imaging unit-side CPU 20, and acquires pixel density data recorded in advance in the nonvolatile memory 21 (S1 in FIG. 4). Next, based on the pixel density data thus obtained, the camera-side CPU 16
It is determined whether or not 8 is a high-density unit (S2 in FIG. 4).

Here, when it is determined that the unit is a high-density unit, the camera-side CPU 16 substitutes the threshold values Ga and Ea that require higher reliability into the determination criteria G1 and E1 used for determining the reliability of focus detection. (FIG. 4S3). Subsequently, the camera-side CPU 16 determines the criterion Fi used for the focus determination.
A threshold value Wa requiring higher focusing accuracy is substituted for n (S4 in FIG. 4).

On the other hand, when it is determined that the unit is a low density unit,
The camera-side CPU 16 determines a threshold G that allows low reliability as the criterion G1, E1 used for the reliability determination of the focus detection.
b and Eb are substituted (S5 in FIG. 4). Then, the camera side C
The PU 16 substitutes a threshold Wb that allows a low focusing accuracy into the criterion Fin used for the focusing determination (FIG. 4S)
6). Note that these reference values have the following magnitude relationship.

Ga <Gb (1) Ea> Eb (2) Wa <Wb (3) Next, the camera-side CPU 16
, A [n] and output signal sequences b [1],..., B [n] are taken in from FIG.

These output signal trains a and b are signal trains which discretely show the luminance patterns of a pair of light images as shown in FIG. The camera-side CPU 16 calculates the following correlation amount C [L] by taking the residual while shifting these output signal sequences a and b by a predetermined amount. (Where L = −Lmax... 0... Lmax) Since the output signal sequences a and b are finite signal sequences,
The first term k and the last term r in the equation (4) are changed as follows depending on the shift amount L.

When L ≧ 0, k = k0 + INT ｛−L / 2｝ r = r0 + INT ｛−L / 2｝ When L <0, k = k0 + INT ｛(− L + 1) / 2｝ r = r0 + INT ｛(− L + 1) / 2} (5) Here, k0 and r0 are the first term k and the last term r when L = 0. INT is a function for rounding down decimal places.

FIG. 6 illustrates the state of the above-described correlation operation. By such a correlation operation, the correlation amount C
A discrete data string of [L] is calculated. Camera side CP
U16 selects data C [Le], C [Le-1], C [Le + 1] near the minimum point from these data strings, and executes the operations of the following equations (6) to (9). I do.

DL = (C [Le−1] −C [Le + 1]) / 2 (6) Cex = C [Le] − | DL | (7) E = MAX ｛C [Le + 1] −C [Le], C [Le−1] −C [Le]｝ (8) Ls = Le + DL / E (9) By the above operation, the correlation amount is minimized as shown in FIG. Value C
ex and the shift amount Ls (corresponding to the shift amount of a pair of optical images) that gives the minimum value Cex can be interpolated (S8 in FIG. 4).

Next, the camera-side CPU 16 executes the following (1)
A reliability judgment is made based on the logical expression (0) (FIG. 4S).
9). (E> E1) and (Cex / E <G1) (10) Here, the numerical value E is a numerical value indicating the steepness of the slope of the correlation amount, and is a value corresponding to the contrast amount of the subject. Therefore, the first term of the expression (10) is an expression for performing the reliability determination based on the contrast amount of the subject.

On the other hand, Cex / E is a value indicating the degree of coincidence between a pair of light images. Therefore, the second term of equation (10) is
This is an expression for determining reliability based on the degree of coincidence of a pair of optical images. In steps S2 to S6 described above, for the imaging unit 18 having a high pixel density, E1 is set to be high and G1 is set to be low. As a result, when the imaging unit 18 having a high pixel density is used, (10)
The expression is set to a logical expression that requires higher reliability.

On the other hand, for the imaging unit 18 having a low pixel density, E1 is set low and G1 is set high. As a result, when the imaging unit 18 having a low pixel density is used, Expression (10) is set to a logical expression that allows lower reliability. The result of such reliability determination (1
When the expression (0) is not satisfied (NO in S10 in FIG. 4), the camera-side CPU 16 determines that "focus cannot be detected" and shifts the operation directly to step S15.

On the other hand, when equation (10) is satisfied (FIG. 4S
(YES side of 10), the camera-side CPU 16 determines that “focus detection is possible”, and calculates the defocus amount DF by multiplying the above-mentioned shift amount Ls by a predetermined proportional constant (FIG. 4).
S11). Subsequently, the camera-side CPU 16 proceeds to the next (1).
Focus determination is performed based on the logical expression of Expression 1) (S1 in FIG. 4).
2).

| DF | <Fin (11) In steps S2 to S6 described above, for the imaging unit 18 having a high pixel density, the in-focus recognition width Fin is set to be small. As a result, the imaging unit 18 having a high pixel density
Is used, Expression (11) is set to a logical expression that requires higher focusing accuracy.

On the other hand, for the imaging unit 18 having a low pixel density, the in-focus recognition width Fin is set to be large. As a result, when using the imaging unit 18 having a low pixel density,
Expression (11) is set to a logical expression that allows lower focusing accuracy. Here, when equation (11) is satisfied (FIG. 4S
13, YES side), the camera-side CPU 16 is in the "focused state".
Therefore, the operation moves to step S15 without executing any further automatic focus adjustment.

On the other hand, when equation (11) is not satisfied (FIG. 4)
(NO side of S13), the camera-side CPU 16 determines that the state is "out of focus", and sets the motor 17 in accordance with the defocus amount DF.
To perform automatic focus adjustment (S14 in FIG. 4). The camera-side CPU 16 returns to step S7 to repeat the operation until the release button is half-pressed or the like is released (S15 in FIG. 4).

Although not shown in FIG. 4, if the release button is fully pressed during the above series of operations, the camera-side CPU 16 shifts to a known imaging operation. With the operation described above, in the electronic camera 11 of the present embodiment, the criterion for reliability determination is flexibly changed according to the pixel density of the imaging unit 18. That is, when the imaging unit 18 with a high pixel density is used, the criterion for the reliability determination is changed to a higher setting. With such a setting change,
Only in cases where a high-precision defocus amount is detected,
Automatic focusing is performed.

Conversely, the imaging unit 1 having a low pixel density
When 8 is used, the criterion for reliability determination is changed to a lower setting. By such a setting change, the number of cases where it is determined that focus detection is possible increases, and automatic focus adjustment is performed for a wider range of subjects. In particular, in the electronic camera 11 of the present embodiment, the reliability is determined from both the “contrast amount of the subject” and the “degree of coincidence of a pair of optical images”.
Therefore, the reliability determination can be performed more accurately. In the present embodiment, in particular, two types of threshold values G1 and E
Since the reliability criterion is changed according to 1, there is an advantage that the degree of freedom for setting the criterion is extremely high and the setting can be flexibly changed to various criterion.

In the electronic camera 11 of the present embodiment,
The criterion of the focus determination according to the pixel density of the imaging unit 18 is also flexibly changed. That is, when the imaging unit 18 having a high pixel density is used, the reference for the focus determination is changed to a higher setting. By such a setting change, automatic focusing can be performed with higher focusing accuracy in accordance with the imaging unit 18 having a high pixel density.

Conversely, the imaging unit 1 having a low pixel density
When the number 8 is used, the setting is changed to subtract the criterion for the focus determination. As a result, the focusing accuracy of the focus adjustment can be appropriately reduced according to the imaging unit 18 having a low pixel density, and the focusing speed can be increased instead. In the above-described embodiment, the determination criteria are changed for both the reliability determination and the focus determination, but the present invention is not limited to this. For example, one of the determination criteria may be fixed, and only the other determination criteria may be changed.

In the above-described embodiment, the threshold value is varied for both the "contrast amount of the subject" and the "degree of coincidence of a pair of light images". However, the present invention is not limited to this. For example, one of the thresholds may be fixed and only the other threshold may be changed. Further, in the above-described embodiment, the numerical value E shown in Expression (8) is used as the contrast amount of the subject, but the present invention is not limited to this. Generally, any detection amount that indicates the magnitude of the contrast ratio of a subject can be used as the contrast amount. For example, a difference (spatial differential value) between an adjacent pixel and one of a pair of light images may be obtained, and the maximum value may be obtained from the absolute values of the differences and used as the contrast amount.

In the above-described embodiment, (Cex / E) is used as the degree of coincidence between a pair of optical images. However, the present invention is not limited to this. Generally, any detection amount that indicates the degree of correlation between a pair of optical images can be used as the degree of coincidence. For example, the minimum correlation amount Cex or the like may be used as the degree of coincidence. Further, in the above-described embodiment, the pixel density data is obtained from the imaging unit 18,
It is not limited to this. Generally, data that can be converted to the pixel density of the image sensor 19 may be obtained.

For example, a drive clock for the image sensor 19 may be obtained. In this case, it is possible to detect the pixel density from the frequency of the driving clock. Further, for example, the type data of the imaging unit 18 or the imaging element 19 may be obtained. In this case, a correspondence table between the type data and the pixel density data is provided in advance on the electronic camera 11 side, and the pixel density can be detected by referring to the table. Of course, a correspondence table between the type data and the data of the criterion (for example, threshold values Ga, Ea, Wa, etc.) is created in advance in consideration of the pixel density, and the data of the criterion is directly created by referring to this table. May be acquired.

In the above embodiment, the reliability judgment in the phase difference detection method has been described, but the present invention is not limited to this. For example, in a hill-climbing type focus adjustment using a contrast detection method, the reliability may be determined by determining the contrast amount of the subject. In this case, the setting of the criterion for determining the contrast amount may be changed according to the replacement of the imaging unit.

For example, in the focus detection by the passive ranging method, the reliability may be determined based on the contrast amount of the subject or the degree of coincidence of a pair of light images. In this case, the setting of the contrast amount or the criterion for determining the degree of coincidence may be changed according to the replacement of the imaging unit. Further, for example, in the focus detection by the active distance measurement method, the reliability may be determined based on the light amount of the light receiving spot and the spread of the light spot. In this case, it is only necessary to change the setting of the criterion for determining the light amount and spread of the light receiving spot in accordance with the replacement of the imaging unit.

In the above embodiment, the case where the automatic focus adjustment (auto focus) is performed has been described, but the present invention is not limited to this. For example, in the display of the focus adjustment state in the manual mode (so-called focus aid), according to the replacement of the imaging unit,
The criterion for reliability determination or focus determination may be changed.

In the above-described embodiment, the case where the image pickup unit 18 is exchangeably mounted on the image pickup exchange mechanism 11a has been described. However, the present invention is not limited to this. For example, in a case where a plurality of image sensors having different pixel densities are provided in a camera or an image pickup unit, and these image sensors are switched and used in an image pickup operation, according to the pixel density of the image sensor used. Then, the setting of the determination criteria for the reliability determination or the focus determination may be changed.

[0060]

As described above, according to the first aspect of the present invention, the criterion for determining the reliability is changed in accordance with the pixel density of the imaging means. Such a change in the criterion makes it possible to flexibly perform the reliability determination in accordance with the pixel density of the imaging unit. According to the second aspect of the present invention, data relating to pixel density is acquired from the side of the imaging means mounted on the imaging exchange mechanism, and the criterion for reliability determination is changed according to the acquired data. Therefore, it is possible to automatically determine the pixel density of the imaging unit and flexibly execute the reliability determination.

According to the third aspect of the present invention, when an image pickup means having a high pixel density is used, the criterion for determining the reliability of the focus detection result is set higher. By such a setting change, only a focus detection result that passes a high determination criterion is determined to be “reliable”, and it is determined that focus detection is possible. Therefore, when using the imaging unit having a high pixel density, it is possible to execute a focus adjustment operation, a display of a focus adjustment state, and the like with high accuracy, limited to only a focus detection result with high accuracy. Such a high-precision focus adjustment operation and display of the focus adjustment state are operations suitable for “imaging means with a high pixel density” for accurately imaging even a minute blur shape.

On the contrary, when the image pickup means having a low pixel density is used, the setting of the criterion for determining the reliability of the focus detection result is changed to a low value. By such a setting change, the focus detection result over a wider range is determined to be “reliable”, and it is determined that focus detection is possible. Therefore, when using an imaging unit having a low pixel density, it is possible to execute a focus adjustment operation, a display of a focus adjustment state, and the like for a wider range of subjects. The focus adjustment operation and the display of the focus adjustment state for a wide range of subjects are operations suitable for “imaging means with a low pixel density” in which minute blur shapes are not conspicuous.

According to the fourth aspect of the present invention, the reliability judging means judges the amount of contrast of the object,
The reliability of the focus detection result is determined. According to the fifth aspect of the present invention, the reliability determination unit determines the reliability of the focus detection result by determining the degree of coincidence between the pair of optical images. In the invention according to claim 6, the criterion of the focus determination is changed in accordance with the pixel density of the imaging means. By such a change of the criterion, it is possible to flexibly execute the focus determination appropriately adjusted to the pixel density of the imaging unit.

According to the seventh aspect of the present invention, data relating to the pixel density is obtained from the side of the image pickup means mounted on the image pickup exchange mechanism, and the criterion for the focus judgment is changed according to the obtained data. Therefore, it is possible to automatically determine the pixel density of the imaging unit and flexibly execute the reliability determination. According to the eighth aspect of the present invention, when an imaging unit having a high pixel density is used, the setting of the criterion for the focus determination is changed to a higher value. As a result, the focus is adjusted with higher focusing accuracy in accordance with the imaging means having a high pixel density. Such a high-precision focus adjustment operation and display of the focus adjustment state are operations suitable for “imaging means with a high pixel density” that requires high focusing accuracy due to a small allowable circle of confusion.

On the contrary, when the image pickup means having a low pixel density is used, the setting is changed to subtract the criterion for the focus determination.
As a result, the focusing accuracy of the focus adjustment can be appropriately reduced in accordance with the imaging means having a low pixel density, and the focusing speed can be increased instead. Such an operation of improving the focusing speed at the expense of the focusing accuracy is performed by a “low-pixel-density imaging unit” in which a low focusing accuracy is allowed because the permissible circle of confusion is large.
The operation is suitable for

[Brief description of the drawings]

FIG. 1 is a principle block diagram for explaining the invention described in claims 1 to 5;

FIG. 2 is a principle block diagram for explaining the invention described in claims 6 to 8;

FIG. 3 is a diagram illustrating a configuration of an embodiment.

FIG. 4 is a flowchart illustrating an operation of a camera-side CPU 16 in the embodiment.

FIG. 5 is a diagram illustrating an output signal sequence output from a focus detection module 15;

FIG. 6 is a diagram illustrating a state of a correlation operation.

FIG. 7 is a diagram illustrating an interpolation calculation of a shift amount Ls.

FIG. 8 is a diagram illustrating a configuration of a focus detection module.

[Explanation of symbols]

 Z imaging optical system 1 imaging means 2 focus detection means 3 reliability determination means 4 imaging exchange mechanism 5 reliability reference changing means 7 focusing determination means 8 focusing reference changing means 11 electronic camera 11a imaging exchange mechanism 12 imaging optical system 13 main Mirror 14 Submirror 15 Focus detection module 16 Camera side CPU 17 Motor 18 Imaging unit 19 Imaging element 20 Imaging unit side CPU 21 Memory 70 Imaging optical system 71 Field mask 72 Field lens 73 Aperture mask 73a, 73b Opening 74a, 74b Re-imaging Lens 75 Focus detection sensor

Claims (8)

[Claims] An imaging unit that captures an optical image formed by an imaging optical system and outputs an image signal; a focus detection unit that detects a focus adjustment state of the imaging optical system; and a detection result of the focus detection unit. In a digital camera with a focus detection function comprising a reliability determination unit for determining whether or not focus detection is possible, a pixel density of the imaging unit can be changed. An electronic camera with a focus detection function, comprising: reliability criterion changing means for changing a criterion of the reliability deciding means in accordance with a pixel density. 2. The electronic camera with a focus detection function according to claim 1, further comprising: an image exchange mechanism for interchangeably mounting said image pickup units having different pixel densities; An electronic camera with a focus detection function, wherein data relating to a pixel density is acquired from the imaging unit via a mechanism, and a criterion of the reliability determining unit is changed according to the acquired data. 3. The electronic camera with a focus detection function according to claim 1, wherein the reliability criterion changing unit increases the reliability as the pixel density of the imaging unit in use increases. An electronic camera with a focus detection function characterized by changing to a required criterion. 4. The electronic camera with a focus detection function according to claim 1, wherein the reliability determination unit determines the reliability of the focus detection result by determining a contrast amount of a subject. An electronic camera with a focus detection function, which is a means. 5. The electronic camera with a focus detection function according to claim 1, wherein said focus detection means comprises: a focus detection optical system configured to pupil-divide subject light to form a pair of light images; A focus detection imaging unit that captures a pair of optical images formed by the focus detection optical system; and a defocus amount calculated based on a phase difference between the “pair of optical images” captured by the focus detection imaging unit. A focus calculation unit that performs a reliability determination of a focus detection result by determining a degree of coincidence between the pair of optical images. With electronic camera. 6. An imaging means for capturing an optical image formed by an imaging optical system and outputting an image signal; a focus detection means for detecting a focus adjustment state of the imaging optical system; and a detection result of the focus detection means. An electronic camera with a focus detection function, comprising: a focus determination unit that performs a focus determination on; a focus criterion changing unit that changes a determination criterion of the focus determination unit according to a pixel density of the imaging unit. An electronic camera with a focus detection function, comprising: 7. The electronic camera with a focus detection function according to claim 6, further comprising: an image pickup exchange mechanism for interchangeably mounting said image pickup units having different pixel densities; An electronic camera with a focus detection function, wherein data relating to pixel density is acquired from the imaging means side via a mechanism, and a criterion of the focus determination means is changed according to the acquired data. 8. The electronic camera with a focus detection function according to claim 6, wherein the focusing reference changing unit has a higher focusing accuracy as the pixel density of the imaging unit in use increases. An electronic camera with a focus detection function, wherein the electronic camera is changed to a criterion that requires the following.