JP3015345B2 - Focusing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a focusing device, and more particularly to a focusing device capable of setting a pupil opening to a plurality of pupil positions for calculating a focusing position.

[0002]

2. Description of the Related Art There are two main auto-focusing methods in an electronic camera, a hill-climbing method using an image signal of an image sensor and a phase difference detecting method also used in a silver halide film camera. I have.

The hill-climbing method is a method in which a high-frequency component of an image signal is detected and a position at which the maximum value is obtained is set as a focus position. Therefore, there is no need for a dedicated photometric element or its optical system. However, there is a disadvantage that it takes time to calculate a focus position because the focus lens is sequentially moved to perform detection.

On the other hand, the phase difference detection method is a method in which the in-focus position is calculated by comparing the phases of two images viewed from different directions depending on a plurality of pupil positions. There is an advantage that can be obtained. But,
In this phase difference detection method, a dedicated photometric element is required, so that the space and cost required for the arrangement are increased. Further, when the optical system for the photometric element is arranged independently of the optical system for the imaging element, there is a problem that high accuracy is required for the mounting position, assembling cost is increased, and parallax is generated.

In order to solve these difficulties, a pair of pupil positions symmetrical with respect to the optical axis in the luminous flux are changed by utilizing the fact that an image pickup device for capturing an image is already mounted on the electronic camera. A technique has been proposed in which a phase difference is detected by appearing in time and comparing image signals of an image sensor at these two different pupil positions.

As an example of such a technique, the present applicant has proposed in Japanese Patent Application Laid-Open No. 57-179810.
A beam splitter is provided in the photographing optical system to divide the subject light, and a light-shielding plate having a plurality of openings arranged near the pupil plane of one of the divided optical systems, the opening of which is always on the pupil. There is a configuration in which the rotation is controlled stepwise so as to stop, and an image signal of the image sensor is sampled during the stop period to calculate a focus position.

Japanese Patent Application Laid-Open No. 9-184972 discloses an aperture blade provided with both an aperture opening serving as a light amount control unit and a pair of pupil openings serving as a pupil dividing unit along a circumferential direction of a disk surface. A motor for rotating the diaphragm blade to selectively face the diaphragm opening or the pupil opening in the light beam;
There is described an imaging apparatus including: a light-shielding vane that rotates into and out of a photographic light beam in order to close one of the pair of pupil openings.

When the in-focus state is detected, the aperture blades are rotated by the motor so that a pair of pupil openings are exposed in the photographic light beam, and the pair of pupil openings are alternately closed by the light-shielding blades. The in-focus position is calculated by comparing the phases of the obtained signals of the image sensor. At the time of subsequent photographing, the focus lens is moved based on the focus position calculated in this way, and the motor is used to rotate the aperture blades so that an appropriate aperture opening is exposed in the photographing light beam, and then the image is captured by the image sensor. To record the image signal.

One of the factors that determine the accuracy of the focus position in the above-described phase difference detection method is the position accuracy of the pupil position. That is, since the phase difference detection method is to calculate the focus position by comparing the phase shift of a pair of image signals obtained at different pupil positions, the phase difference detection method is used to calculate the focus position from the center of the imaging optical axis to each pupil position. If there is a relative difference between the distances, an error occurs in the focus position detected due to the relative difference. Therefore, it is important to position the opening that determines the pupil position.

[0010]

However, in the apparatus disclosed in Japanese Patent Application Laid-Open No. 57-179810, the light-shielding plate having the pupil opening itself is rotated by a step motor, and the stop inherent to the step motor is used. Although there is a possibility that a variation in the position and a variation in self-holding after the stop may occur, no particular consideration is given to a technique for ensuring the accuracy of the stop position.

Similarly, in Japanese Patent Application Laid-Open No. 9-184972, the diaphragm blade having the pupil aperture is rotated and moved. However, the variation in the stop positions of the pair of pupil apertures themselves in the photographing light beam is reduced. Not specifically considered.

Therefore, in these conventional techniques, since the stop position of the pupil opening is not always constant, a focusing device capable of improving such a point and further improving the accuracy of the calculated focusing position is desired. It is rare.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a focusing device capable of reducing the uncertainty of a pupil position and calculating a focusing position with higher accuracy. I have.

[0014]

In order to achieve the above object, a focusing apparatus according to a first aspect of the present invention compares an image signal of an image sensor at different pupil positions to calculate a focusing position. A focusing device configured so that a pupil opening, which is a portion through which a light beam passes, can be set at a plurality of pupil positions in a plane perpendicular to the optical axis, and is capable of freely entering and exiting on a passage path of the photographing light beam. A first aperture plate formed with a plurality of pupil openings corresponding to the plurality of pupil positions, a light amount aperture for exposure control, and an auxiliary aperture larger than the pupil aperture; A second aperture plate that can be moved relative to the aperture plate to move the auxiliary aperture to a position where the auxiliary aperture overlaps without causing chipping in the pupil aperture. One of the pupil openings is missing In the case where the pupil apertures are located without overlapping, the other pupil apertures are configured to be in a state where the passage of the photographic light flux is blocked by portions other than the auxiliary apertures of the second aperture plate. .

The focusing device according to a second aspect of the present invention is the focusing device according to the first aspect, wherein the second diaphragm plate has a substantially disk shape, and the plurality of light quantity diaphragms are formed on the disk surface. In addition, a plurality of the auxiliary openings are formed adjacent to these light amount apertures.

Further, in the focusing device according to the third invention, in the focusing device according to the first invention, when the first diaphragm plate enters the passage of the photographing light beam, the stop position is set. Further, a stopper for positioning at a predetermined position is further provided.

A focusing device according to a fourth aspect of the present invention is the focusing device according to the first or second aspect, wherein the auxiliary aperture overlaps the second diaphragm plate without causing a chip in the pupil aperture. A detected part for detecting the position is formed, and a position detector for detecting the detected part is further provided.

A focusing device according to a fifth aspect of the present invention is the focusing device according to the second aspect of the invention, wherein the second diaphragm plate is rotatable about a substantially center of the substantially disk-shaped surface. The plurality of light apertures are arranged along the rotation direction on the disk surface, and the auxiliary aperture is disposed at a position in the rotation direction between the light apertures.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show an embodiment of the present invention. FIG. 1 is a block diagram showing a configuration of an electronic camera. FIG. 2 is a diagram showing a principle of detecting a focus position by different pupil positions. FIG. 4 is a front view showing a state where the diaphragm and the phase difference AF device are opened, and FIG. 4 is a front view showing a state where the diaphragm and the phase difference AF device are at the left pupil position.
FIG. 5 is a front view showing a state where the aperture and the phase difference AF device are at the right pupil position. In this embodiment, a focusing device is applied to an electronic camera.

In this electronic camera, as shown in FIG. 1, a subject image is formed on an image sensor 6 by a photographing lens system 1, and
After the signal photoelectrically converted by the image pickup device 6 is processed in the image pickup circuit 7, the signal is converted into a digital signal by the A / D conversion circuit 8.

The photographing lens system 1 changes the focal length of the entire photographing lens system 1 by moving in the direction of the optical axis, and changes the magnification of a subject image formed on the image sensor 6. A shutter 3 capable of taking a state in which the passage of the light beam from the zoom lens 2 is permitted and a state in which the passage of the light beam is prohibited;
The aperture and phase difference AF device 4 that limits the passage range of the light beam that has passed through the shutter 3 and realizes different pupil positions for performing the phase difference AF, and the focal position of the photographing lens system 1 coincides with the image sensor 6. And a focus lens 5 for performing adjustment.

The output of the A / D conversion circuit 8 is output to an AE circuit 9, a hill-climbing AF circuit 10, and a phase difference AF circuit 11.

The AE circuit 9 detects the brightness of the subject image from the output of the image sensor 6, and controls the exposure so as to control the amount of light reaching the image sensor 6 so as to be appropriate. Outputs the value.

The hill-climbing AF circuit 10 detects a high-frequency component in the video output signal of the image sensor 6 and searches the peak value while moving the focus lens 5 little by little. Is the focus position.

The phase difference AF circuit 11 forms an image of a subject at a different pupil position on the image sensor 6 by the aperture and phase difference AF device 4, and detects a focus position based on the output. Yes, and its principle and details will be described later.

The AE circuit 9, the hill-climbing AF circuit 10,
The detection result by the phase difference AF circuit 11 is input to the system controller 12, and necessary control is performed. That is, the system controller 12
Controls the movement of the zoom lens 2 by controlling a zoom motor 14 via a zoom circuit 13 and drives the shutter 3 by controlling a shutter actuator 16 via a shutter drive circuit 15. By controlling the aperture and the AF motor 18 via the aperture and AF drive circuit 17, the aperture and the phase difference AF device 4 are driven, and the focus motor 20 is controlled via the focus motor drive circuit 19. By driving the focus lens 5, the strobe 29 is controlled via a strobe circuit 28 to emit light. In addition, an operation unit 30 including various switches and buttons is used to emit light. The operation result is input.

The output of the A / D conversion circuit 8 is temporarily stored in a memory 22 after further processing by an image processing circuit 21, converted into a signal for display by an image display circuit 23, and then outputted to an image display unit 24. A subject image is displayed.

When an instruction to perform recording is input through the operation unit 30, the output of the memory 22 is compressed by the compression / expansion circuit 25 to reduce the amount of information, and then the recording medium I / F 26 is used. Through a recording medium 27 such as a removable memory card.

Although not particularly shown, the recording medium 27
The compressed image information recorded in the image display section 24 is read out, subjected to a decompression process, and displayed on the image display section 24.

Next, with reference to FIG. 2, the principle of detecting the focus position with different pupil positions will be described.

A light-shielding plate LS having a pupil opening LS1 is arranged in front of the lens L so as to be rotatable around an axis LS0, and an object OB is imaged through the pupil opening LS1. in this case,
On the in-focus plane Q1, the pupil opening LS1 as shown in FIG. 2A is located above and the pupil opening LS1 as shown in FIG. 2B is located below. Although the image IM is formed at the same position, the image IM 'in the case of FIG. 2A and the image IM' of FIG.
In this case, the image IM ″ is formed at a different position. Therefore, if the image position is adjusted so that the image position does not move even when the light shielding plate LS is rotated, the focus of the lens L is correctly adjusted.

Based on such a principle, the diaphragm and phase difference AF device 4 is configured as shown in FIGS.

That is, the diaphragm and the phase difference AF device 4
Are a diaphragm plate 41 as a second diaphragm plate, an AF shutter 42 as a first diaphragm plate, a stopper 43, and a position detector 4
4.

The aperture plate 41 is a disk-shaped plate member rotatable around a rotation axis 41a disposed in parallel with the photographing optical axis of the photographing lens system 1, and is formed in a circumferential direction. Along the large-diameter light stop 41b, a medium-diameter light stop 41c,
A small-diameter light-amount aperture 41d is provided, and these light-amount apertures 41b, 41c, 41d are incident through the zoom lens 2 and the shutter 3 by rotating the aperture plate 41 around a rotation axis 41a. It can be arranged on the path of the incoming light beam. The range in which the incident light beam passes through the aperture plate 41 is the large-diameter light amount aperture 4 shown in FIG.
1b.

The diaphragm plate 41 is provided with the light amount diaphragm 4.
1b, 41c, 41d in the rotational direction position between each other,
A plurality of auxiliary openings 41e are arranged so as to be adjacent to the respective light amount apertures 41b, 41c, 41d. The auxiliary opening 41e is an opening larger than pupil openings 42b and 42c described later, that is, these pupil openings 42b and 42c.
The opening c is formed as an opening large enough to cover without causing chipping, and is, for example, a large opening with a margin.

Further, near the periphery of the diaphragm plate 41,
Sensing holes 41f, which are a plurality of detected portions, corresponding to the plurality of auxiliary openings 41e, respectively, are formed in the circumferential direction.

The AF shutter 42 includes a support shaft 42a.
It is a plate-like member which is configured to be rotatable around and has a substantially fan shape. The AF shutter 42 has, for example, two pupil openings 42b and 42c corresponding to a plurality of pupil positions.
Are formed so that they can be simultaneously located on the passage path of the photographing light beam.

That is, in a plane perpendicular to the optical axis of the photographic light beam, the pupil openings 42b and 42c are arranged at intervals so that the two pupil openings 42b and 42c can be simultaneously positioned within the passing range of the photographic light beam. Can be arranged at both end positions symmetrical with respect to the optical axis within the photographing light beam passage range.

The stopper 43 is for positioning the stop position of the AF shutter 42 at a predetermined position when the AF shutter 42 rotates around the support shaft 42a and enters the passage of the photographing light beam. .

The position detector 44 detects the sensing hole 41f, thereby detecting the auxiliary opening 41e.
Move to a position where one of the pupil openings 42b and 42c overlaps without causing chipping, and
The other of b and 42c detects that the passage of the photographing light beam is blocked by a portion of the diaphragm plate 41 where the openings and the like are not provided.

Next, the operation of such an embodiment will be described with reference to FIGS.

FIG. 3 shows a state in which a photographing light beam is passed through a large-diameter light amount aperture 41b, for example, when photographing is performed with the aperture opened.

At this time, the AF shutter 42 is retracted from the passage of the photographic light beam. When the aperture of the light amount aperture is changed, the aperture plate 41 is rotated by driving the above-mentioned aperture and the AF motor 18 so that a desired light amount aperture 41b in FIG. What is necessary is just to position the aperture of the light quantity aperture.

FIG. 4 shows the phase difference A due to the left pupil opening 42b.
This shows a state when F detection is being performed.

At this time, the AF shutter 42 enters the photographing light beam passing path by driving the aperture and the AF motor 18, and is positioned within the photographing light beam passing range by the stopper 43. I have.

By driving the aperture and the AF motor 18, the aperture plate 41 is rotated to detect any one of the plurality of sensing holes 41f by the position detector 44, and the position detector 44 detects the position. Aperture, AF motor 1
By stopping the shutter 8, the auxiliary opening 41e is positioned at the left pupil opening 42b, so that the auxiliary opening 41e overlaps without causing chipping. At this time, the right pupil opening 42c is in a state where the passage of the photographing light beam is blocked by the plate surface between the auxiliary opening 41e and the large-diameter light amount aperture 41b,
That is, the photographing light beam reaches the image sensor 6 through only the left pupil opening 42b.

The image sensor 6 formed by the left pupil opening 42b
Then, in order to obtain the output of the image sensor 6 by the pupil opening 42c on the right side, the stop and AF motor 18 constituted by, for example, a stepping motor are rotated by predetermined steps. As a result, as shown in FIG. 5, the auxiliary opening 41e is located at the right pupil opening 42b and is in a state of overlapping without causing chipping. At this time, the left pupil opening 42b is in a state where the passage of the photographing light beam is blocked by the plate surface between the auxiliary opening 41e and the small-diameter light amount aperture 41d. Only the light passes through the image sensor 6.

As described above, the left and right pupil openings 42b, 42c
When the detection is performed, since the AF shutter 42 does not move, the positional relationship between the left and right pupil positions is extremely accurate.

In this way, the output of the image sensor 6 is obtained by the right pupil opening 42c, and the phase difference AF circuit 11
The phase difference AF detection is performed based on the principle shown in FIG. 2 by comparing the detection result obtained by the left pupil opening 42b obtained above.

The aperture and AF motor 18 can rotate the aperture plate 41 by switching its output destination,
The rotation of the AF shutter 42 can be performed. However, a plurality of driving sources corresponding to the aperture plate 41 and the AF shutter 42 are provided, and these are independently driven. No problem.

Based on the detected result, the system controller 12 drives the focus motor 20 via the focus motor drive circuit 19, so that the image pickup surface of the image pickup device 6 can be accurately focused.

When recording on the recording medium 27 after focusing, first, the diaphragm and AF motor 18 is driven to rotate the diaphragm plate 41, and based on the exposure value of the AE circuit 9, Light amount apertures 41b, 41c, 41d selected by
Is moved on the optical path.

The auxiliary aperture 41e and the light quantity stop 41
Since the auxiliary opening 41e is formed adjacent to each of the light amount apertures 41b, 41c, 41d, the movement can be performed quickly, and the time lag can be reduced. It can be shortened.

In the above-described configuration, as the means for detecting the focal position, the hill-climbing AF circuit 10 and the phase difference A are used.
Although the F circuit 11 is provided, as the proper use of these circuits, one that is considered more effective according to the subject may be selected and used, or the phase difference A
The focus position may be roughly detected by the F circuit 11, and then more detailed focusing may be performed by the hill-climbing method.

According to such an embodiment, when performing the phase difference AF at different pupil positions, each pupil position does not move, so that it is possible to perform accurate measurement at the pupil position.

Further, the pupil opening is provided in the AF shutter,
By rotating the AF shutter about the axis so that it can freely enter and exit the optical path of the photographing light beam, it is possible to enter and exit with a simple driving mechanism without increasing the thickness in the optical axis direction.

When the shutter for AF is inserted in the optical path of the photographic light beam, the stop position is accurately positioned using the stopper, so that the phase difference AF
Is performed, the pupil position is accurately stopped.

Further, since an auxiliary aperture for selecting one of the plurality of pupil apertures is formed on the aperture plate, a dedicated member for providing the auxiliary aperture is not required, and the configuration is simplified, and the apparatus is simplified. The overall size can be reduced. In addition, since the auxiliary aperture is formed to be slightly larger than the pupil aperture, it is sufficient to secure a certain degree of stop accuracy for the auxiliary aperture, and the stop position can be easily controlled even by using a step motor or the like. It becomes possible.

Further, since these auxiliary apertures are arranged adjacent to the light amount apertures provided on the aperture plate, the focusing operation is performed using the auxiliary apertures, and the light amount used during the photographing operation is immediately obtained. Since it is possible to move to the aperture, a time lag at the time of shooting can be reduced.

By providing a sensing hole in the aperture plate and detecting the sensing hole with the position detector, the auxiliary aperture can be stopped properly at a position where the auxiliary aperture overlaps without causing the pupil aperture to be chipped. .

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications and applications are possible without departing from the gist of the invention.

[0062]

As described above, according to the focusing apparatus of the first aspect of the present invention, the first aperture plate having the pupil opening does not move during the focusing operation. And the other pupil openings are accurately maintained in position, and the detection accuracy can be improved. Furthermore, since the second aperture plate is formed with the auxiliary aperture and the light amount aperture for exposure control, the number of members can be reduced and the size of the apparatus can be reduced as compared with the case where these are formed on separate members. .

Further, according to the focusing apparatus of the present invention, the same effect as that of the first aspect can be obtained, and since the auxiliary aperture is formed adjacent to the light amount aperture, the second aspect can be obtained. The aperture plate can be quickly moved between the focusing operation and the photographing operation, and the time lag at the time of photographing can be reduced.

Further, according to the third aspect of the present invention, the same effect as that of the first aspect is obtained, and the first aperture plate enters the passage of the photographing light beam. At this time, since the stop position is accurately positioned by the stopper, the pupil positions for each focusing operation can be accurately aligned.

According to the focusing apparatus of the fourth aspect of the present invention, the same effect as that of the first or second aspect of the present invention can be obtained, and the position detection unit detects the detection target part, so that the auxiliary unit can be used. The opening can be appropriately moved to the overlapping position without causing the pupil opening to be chipped.

According to the focusing apparatus of the fifth aspect of the present invention, the same effect as that of the second aspect of the invention is obtained, and the second diaphragm plate is formed in a substantially disk shape so as to be rotatable around its center. Since the light aperture and the auxiliary aperture are arranged along the rotational direction on the disk surface, the light aperture and the auxiliary aperture can be formed simply by rotating the second aperture plate by an inexpensive driving mechanism using a normal motor or the like. You can choose.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electronic camera according to an embodiment of the present invention.

FIG. 2 is a diagram showing a principle of detecting a focus position by different pupil positions in the embodiment.

FIG. 3 is a front view showing a state of the diaphragm and the phase difference AF device in the embodiment when the diaphragm is opened.

FIG. 4 is a front view showing a state in which the stop and the phase difference AF device in the embodiment are in a left pupil position.

FIG. 5 is a front view showing a state in which the stop and the phase difference AF device in the embodiment are at the right pupil position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 4 ... Aperture, phase difference AF device 6 ... Image sensor 10 ... Climbing AF circuit 11 ... Phase difference AF circuit 12 ... System controller 17 ... Aperture, AF drive circuit 18 ... Aperture, AF motor 41 ... Aperture plate (second Aperture plates) 41b, 41c, 41d: Light amount aperture 41e: Auxiliary aperture 41f: Sensing hole (detected portion) 42: AF shutter (first aperture plate) 42b, 42c: Pupil aperture 43: Stopper 44: Position detector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-114007 (JP, A) JP-A-10-186221 (JP, A) JP-A-11-142723 (JP, A) JP-A 10-108 319310 (JP, A) JP-A-1-216308 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B ^7/ 28-7/40

Claims (5)

(57) [Claims] In order to calculate an in-focus position by comparing image signals of an image sensor at different pupil positions, a plurality of pupils in a plane perpendicular to the optical axis are provided with a pupil opening which is a portion through which a photographing light beam passes. A focusing device configured to be able to be set to a position, wherein the focusing device is disposed so as to be able to enter and exit freely on a passage path of the photographing light beam, and has a plurality of pupil openings corresponding to the plurality of pupil positions. A first aperture plate, a light amount aperture for exposure control, and an auxiliary aperture larger than the pupil aperture are formed, and the auxiliary aperture is moved by moving relative to the first aperture plate. A second diaphragm plate that can be moved to a position where the pupil opening overlaps without causing chipping, wherein the auxiliary opening is located at a position where any one of the plurality of pupil openings overlaps without causing chipping. In some cases, the other pupil aperture is The portion other than the auxiliary opening of the second throttle plate focusing device which is characterized in that which has been configured to be the state in which the passage is shielded between the imaging beam. 2. The second diaphragm plate has a substantially disc shape, and a plurality of light quantity diaphragms are formed on the disc surface.
2. The focusing device according to claim 1, wherein a plurality of the auxiliary openings are formed adjacent to the light amount apertures. 3. The apparatus according to claim 1, further comprising a stopper for positioning the stop position at a predetermined position when the first diaphragm plate enters the passage of the photographing light beam. A focusing device according to claim 1. 4. A detection portion for detecting that the auxiliary aperture is located at an overlapping position without causing a chip in the pupil opening, is formed in the second diaphragm plate. The focusing device according to claim 1, further comprising a position detector that detects the position. 5. The second aperture plate is configured to be rotatable around a substantially center of the substantially disk-shaped disk surface, and the plurality of light amount apertures are arranged along a rotation direction on the disk surface. 3. The focusing device according to claim 2, wherein the auxiliary apertures are arranged, and the auxiliary apertures are arranged at rotational positions between the light amount apertures.