JP3297179B2 - Camera focus correction mode mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera in which a flange back is defined with respect to a lens mount surface, and more particularly, to a focus correction mode mechanism capable of correcting a flange back in the camera back and forth.

[0002]

2. Description of the Related Art Currently, there is no commercially available AF single-lens reflex camera having a mechanism for correcting focus. For example, in a single-lens reflex camera of an AF control method using a lens driven by a dedicated lens, if the focus position is intentionally corrected, after the focus operation, the mode is switched from the AF mode to the MF shooting mode to enable manual operation. In this case, the procedure of turning the distance ring of the lens for correction is performed, and the operation is complicated.

[0003]

Recently, AF machines for single-lens reflex cameras have become widespread, and the AF market has reached the high-end camera market. As described above, while the convenience of the AF camera has been recognized, professionals still have doubts about the AF operation and often use a conventional manual camera or a high-quality AF single-lens reflex camera in the MF mode. Can be seen. This is because the AF camera automatically determines the focus according to the physical detection method, so the focus state intended by the photographer or the focus position that the photographer determines as the best image point differs depending on the scene, This is because the AF camera cannot take such a case into account. Furthermore, AF
When the subject is in focus due to the operation, or due to the characteristics of AF,
This is because a shift may occur, and the screen may not always be satisfactory for the photographer.

[0004] In view of the above, there has been a demand for a mechanism capable of performing focus correction as intended by a photographer, for a camera in which a flange back is defined for a lens mount, including a manual and an AF single-lens camera. . An object of the present invention is to provide a camera focus correction mode mechanism capable of correcting a back focus back and forth in accordance with a subject or AF characteristics. Another object of the present invention is to divide a camera into which a conventional lens can be mounted and exchanged into a front fixed block and a rear movable block, perform focus adjustment by moving the rear movable block, and automate this to perform AF photography. In the AF single-lens reflex camera of the back focus control system which is made possible, a correction value before and after a required focus position is set in advance according to a subject or AF characteristics, and a focus determination reference position is set according to the correction value. The present invention is to provide a focus correction mode mechanism which shifts forward and backward by a predetermined amount and determines that focus is achieved at that position.

[0005]

In order to achieve the above object, a camera focus correction mode mechanism according to the present invention comprises:
At least a taking lens and a lens for the taking lens
Camera body front block including mount, at least
A camera body rear block including a film opening;
Camera body front block and camera body rear block
Between the front and rear blocks to adjust the distance
And the lens unit of the front block of the camera body.
Drive that adjusts the distance between the und and the opening in the rear block
And the flange back of the photographing lens.
AF single-lens reflex camera that performs focusing by adjusting
The flange bar specified for the lens mount surface.
Enter the amount of correction to correct the lock position forward or backward
Focus correction input means for
The position is calculated, and a correction amount is previously calculated by the focus correction input means.
Is set or the correction amount is set
Is shifted from the focal point position according to the correction amount.
The back position to the front or back, and
Control means for performing focus determination with the adjusted position as the focal point.
There is a digit structure.

[0006]

According to the above arrangement, when it is known that the focal position of the camera is shifted to the front or rear pin side, the correction of the position of the flange back can be set in advance.
It is also possible to correct the position of the flange back after viewing the image on the finder screen. In the back focus control type AF single-lens reflex camera, the user first holds the camera as a photographing operation, starts the AF operation by half-pressing the release button, and starts the AF operation substantially at the center of the viewfinder screen.
According to the distance information of the subject incident on the sensor, the rear block side having the focal plane of the camera body moves to a focusing position at a different distance depending on the type of the mounted photographic lens. When it is determined that the focal point has been reached, the movement of the rear block of the main body is stopped. Since the photographer can check the in-focus state on the finder screen, if the in-focus state can be satisfied, the release button may be further pressed to shift to the photographing operation. However, if you are dissatisfied with this focus state,
Or, when the focus position is intentionally shifted by the photographer's intention, the correction dial is turned to the front focus side or the rear focus side, and only a correction amount of a small unit (for example, 50 μmm) is added according to the correction value indicated on the dial. The focal plane at the rear of the body moves back and forth.

Further, if it is known in advance that the best image intended by the photographer can be obtained with a slight front focus or a slight back focus from the AF characteristics, the correction dial is pre-corrected and post-corrected from the beginning. If you set it to
The focus determination on the camera side is performed at the corrected back focus position, and the focus is automatically corrected each time shooting is performed. For this reason, the photographer can create an arbitrarily corrected image while taking into account the best image point due to the composition and characteristics of the viewfinder screen. This focus correction employs a method of directly correcting the back focus distance, but the focus state differs depending on the aperture value. That is, depending on the depth of focus, a minute correction may not affect the focus image characteristic. For this reason, it is also possible to perform correction in consideration of the depth of focus by the aperture.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings. FIG. 1 is a schematic front view showing an embodiment of a camera employing a focus correction mode mechanism according to the present invention,
This is an example of a case where the flange back is manually corrected forward and backward. This embodiment may be an AF camera driven by a lens or an MF camera driven by a lens distance ring. The film opening 9 is constituted by a movable opening 10 which can move back and forth with respect to the reference position of the flange back. The movable opening 10 is supported by the camera body by the linear guide 6 and the lead screw 1.
The linear guide 6 is for always holding and guiding the film surface 5 of the movable opening 10 at right angles to the optical axis.
The linear screw 1 performs the same function as the lead guide 6 and moves the movable opening 10 back and forth by rotating.

A gear 8 is fixed to the lead screw 1, and a gear 7 fixed to the shaft of the FB correction dial 2 meshes with the gear 8. The FB correction dial 2 can perform three-stage correction on the front focus side and the rear focus side, respectively. Any of 0.05 mm, 0.1 mm and 0.15 mm can be selected for the front pin side. On the rear pin side, any one of -0.05 mm, -0.1 mm and -0.15 mm can be selected. After manually focusing by operating the lens distance ring, by operating this focus correction mechanism, the flange back can be corrected quantitatively (0.1 mm, -0.05 mm, etc.). In AF by lens driving, if the amount to be corrected is known in advance, the correction can be performed by operating the FB correction dial 2 before the AF operation. After the AF operation is performed, the focus state of the image is viewed on the film screen, and the flange back can be quantitatively corrected by the FB correction dial 2.

FIG. 2 is a schematic front view showing another embodiment of a camera employing the focus correction mode mechanism according to the present invention, in which a flange back is corrected back and forth by a motor drive. This embodiment may be an AF camera driven by a lens or an MF camera driven by a lens distance ring, as in FIG. The film opening, the linear guide 11 and the FB (flange back) drive lead screw 12 are functional parts similar to the film opening 9, the linear guide 6 and the lead screw 1 in FIG. The FB drive lead screw 12 has a gear 18
Is fixed, and the gear 18 is engaged with the gear 19. FB
A gear 19 and a rotating part of the FB movement amount detection encoder 13 are fixed to the shaft of the correction drive motor 16.

The FB moving amount detecting encoder 13 can detect the moving amount of the movable opening 17 before and after.
In the AF by lens driving, if the amount to be corrected is known in advance, the FB correction driving motor 16 can be driven by a switch (not shown) or the like before the AF operation to correct the flange back forward and backward. Further, after the AF operation is performed, the FB correction drive motor 16 is similarly driven by observing the focus state of the image on the film screen, and the flange back can be corrected back and forth.

FIG. 3 is a schematic front view showing still another embodiment of a camera employing the focus correction mode mechanism according to the present invention, and is an example applied to an autofocus single-lens reflex camera of a back focus control system. FIG. 4A is a partial plan sectional view for explaining the details of the shape of the camera body front block of FIG. 3, and FIGS. 4B and 4C are coupling mechanisms of the camera body front block and rear block of FIG. FIG. 3 is a schematic diagram for explaining an example of the first embodiment. 3 and 4, the camera body front block A includes an interchangeable lens 29, a lens mount 21, an AF drive mechanism 27, and a grip 37 having a release button 34. The camera body rear block B includes an up-down mirror 33, a finder mechanism 25, an aperture 30, an exposure mechanism, a film feeding mechanism, and a distance measuring mechanism 23.

Light from a subject (not shown) passes through the interchangeable lens 29, the optical path of which is guided upward by the up-down mirror 33, and enters the finder mechanism 25. The optical path is changed by the pentaprism 25a so that the light becomes parallel to the main optical axis, and reaches the eyepiece 25b. Part of the subject light passing through the interchangeable lens 29 is transmitted to the AF mirror 2 of the distance measuring mechanism 23.
The light also enters the lens 3a, is guided downward, and reaches the AF sensor 23c via the AF lens 23b. The AF drive mechanism 27 includes an FB drive motor 27a, an encoder 26 for detecting the rotation speed of the motor 27a, gears 27b and 27c, a lead screw 27d, and a female screw 27e. F
The rotational output of the B drive motor 27a is transmitted to the lead screw 27d through the gears 27b and 27c at a reduced speed. The lead screw 27d is screwed into a female screw 27e provided at the base of the rear block B of the camera body, and the rotation of the lead screw 27d changes the distance in the optical axis direction between the front block A and the rear block B of the camera body. I do. Thus, the lens mount 21 and the aperture (opening)
The distance of 30 or the flange back can be adjusted.

FIG. 3A shows a state in which the rear block B is set to an infinity shooting position, and FIG. 3B shows a state in which the rear block B is set to a closest shooting position. The flange back is configured to be adjustable to a super infinity side which is shorter than the infinity shooting position (reference flange back). Information indicating the positional relationship between the front block A and the rear block B of the camera body can be detected by the position detection switch 28. Code pattern board 28 constituting position detection switch 28
a is fixed to the base of the camera body front block A, and the end of the contact 28b is fixed to the base of the camera body rear block B, respectively. When the distance between the front and rear blocks A and B changes, the code pattern board 28
The code of “a” changes, and an FB position detection signal can be obtained. As the position detection switch 28, another method such as one that detects the sliding resistance may be used.

In FIG. 4, a camera body front block A
A pair of upper rails 36a, 36
b and lower rails 35a and 35b are provided. On the other hand, rollers 37a, 37b and 3
9a and 39b are provided. Rollers 37a, 37b
And 39a, 39b are configured to roll on the upper surfaces of the upper rails 36a, 36b and the lower rails 35a, 35b when the AF driving mechanism 27 operates. With such a configuration, the distance between the front block A and the rear block B of the camera body can be changed smoothly so as to minimize the load. Note that a linearly moving bearing or the like may be used as the other connecting member.

A guide rod 46 is provided on the front block A of the camera body at a position opposite to the lead screw 27d with the up-down mirror 33 interposed therebetween. A guide hole 47 is provided in the rear block B of the camera body as a member for guiding this. The guide rod 46 slides in the guide hole 47 with the rotation of the lead screw 27d, and the lead screw 2
The camera body rear block B is guided to the camera body front block A in cooperation with 7d. Thus, the blocks can be moved so that the optical axis between the two blocks does not shift, and in a state where the aperture surface and the lens mount surface are kept parallel.

FIG. 5 is a block diagram showing an embodiment of a control circuit of the AF single-lens reflex camera of FIG. An FB position detection signal based on a code signal is output from the code pattern substrate 28a, an encoder signal is output from the encoder 26, and a distance measurement signal (AF information) is output from the AF sensor 23c, which are input to the FB drive motor drive circuit 43. AF
The above information is input to the control circuit 40 via the FB drive motor drive circuit 43. Further, an aperture value signal and focus correction information from the focus correction dial 44 are also input. When the focus correction information is input, the position where the flange back is corrected back and forth according to the focus correction amount is determined to be the focus position, and the FB drive motor drive circuit 43 is controlled so as to be the focus position. I do. When the release button 45 is half-pressed, the first release switch 45a is turned on, an AF operation start signal is sent to the AF control circuit 40, and an AF check is performed. Further, when the release button 45 is depressed, the second switch 45b at the next stage is turned on, and a camera operation start signal is input to the camera operation CPU 41, and the camera operation CPU 41
The drive circuit 42 performs mirror up based on the above control, and the shutter mechanism is operated by the camera operation CPU 41 to perform photographing. Subsequently, operations such as mirror down and film winding are performed by the drive circuit 42, and the camera photographing operation is completed.

FIG. 6 is a flowchart for explaining the operation when the absolute amount of the flange back distance is corrected as the focus correction amount of the single-lens reflex camera of FIG. 6, the correction values indicated by ± a, b, and c of the focus correction dial 44 in FIG. 5 represent absolute values for correcting BF. For example, a = 0.05 mm, b = 0.1 mm, c = 0.15 mm, and the like. When the power sw is turned on and the power is turned on (S601), the circuit starts. At this time, the AF control circuit 40 accurately checks the current flange back position based on the FB position detection signal to confirm the read position (S602). Next, the light beam from the subject passing through the photographing lens is
3, the light is guided from the auxiliary mirror 23a to the AF sensor 23b, and the AF control circuit 40 starts the AF control operation (S603). The defocus amount is calculated based on the AF sensor signal, and the back focus distance f ₀ at the in-focus position is determined from the calculation result such as the shift amount from the current position of the BF to the in-focus point (S604).

Here, when the check switch 45a linked with the release is turned on, it is confirmed whether or not a command of the focus correction is issued by the photographer's will (S606). The operation is divided into the following operations according to the type of the front focus (positive correction) or the rear focus (minus correction) and the correction amount Δf. That is, when the correction command is not issued, it is determined whether or not the flange back is positioned at the shift amount f ₀ calculated at S604 (S607), and the shift amount f is determined.
_When the position has not reached the position of _0, the FB drive is performed, and the FB drive is repeated until the position of the shift amount f ₀ is reached (S60).
7, S608). Then, when FB = f ₀ is reached, the driving is stopped, the focus is determined (S609, S610), and the process proceeds to the next sequence of the photographing operation.

On the other hand, if a correction command has been issued, it is determined whether this correction is on the rear side (S611). Y
In the case of ES, the position of FB = f ₀ −Δf is regarded as the focal point,
Next, it is determined whether or not the flange back position has reached this position (S616). If not, the FB is driven (S617), and the FB is repeated until f ₀ −Δf is reached. When f ₀ −Δf is reached, the motor is stopped (S618), and focus determination is performed with the −Δf corrected (S619). If the correction is not on the rear side (NO), the front focus is corrected, so it is determined whether or not the position of the flange back has reached f ₀ + Δf (S61).
2) If not reached, FB is driven (S61)
3) Repeat FB until f ₀ + Δf is reached. When f ₀ + Δf is reached, the motor is stopped (S614).
Focus determination is performed in the state where the correction has been made by + Δf (S615).
Move to the next sequence.

Next, since it is more practical to correct the focus correction photographing in relation to the depth of focus, FIG. 7 shows a flowchart in the case of performing the correction in consideration of the depth of focus as the focus correction amount. In this case, the values indicated by ± a, b, and c of the focus correction dial 44 in FIG. 5 represent the correction magnification, and have the following values. Now, the aperture value (Fn) of the exposure condition for shooting
Assuming that the depth of focus, which is a function of o), is Δs, the following equation is obtained. Δs = δ × Fno where δ represents the minimum circle of confusion, and generally in the Leica format, δ =
It is said to be 0.033. Assuming that the correction magnification is m, the correction amount Δf is as follows: Δf = mΔs = m × δ × Fno. Table 1 specifically shows the correction amount for each correction magnification.

[Table 1]

In FIG. 7, steps from turning on the power (S701) to the release check (S705) are the same as those in S601 in FIG.
To S605. When the release check is performed in S705, it is confirmed whether or not there is a focus correction command according to the photographer's will (S70).
6). The operation is divided as follows depending on whether the correction is a front focus (plus correction) or a rear focus (minus correction) and the correction magnification m. That is, when the correction command is not issued, it is determined whether or not the flange back is positioned at the shift amount f ₀ calculated in S704, and the shift amount f is determined.
_If it has not reached the position of _0, the FB drive is performed, and the FB drive is repeated until the position of the shift amount f ₀ is reached (S70).
7, S708). Then, when FB = f ₀ is reached, the driving is stopped, the focus is determined (S709, S710), and the flow shifts to the next sequence of the photographing operation.

On the other hand, if a correction command has been issued, aperture information Fno is input to calculate a correction value (± m × Δs) (S711). It is determined whether this correction is on the rear side (S712). When YES, FB = f ₀ −Δf = f ₀
The position of −m × δ × Fno is regarded as the focal point, and it is determined whether the flange back position has reached this position (S717). If not, the FB is driven (S717).
718), FB is repeated until f ₀ −Δf is reached. When f ₀ −Δf is reached, the motor is stopped (S71).
9) In-focus determination is performed in the state where the correction is performed by -Δf (S72).
0). When the correction is not on the rear side (NO), the front focus correction is performed, so that the position of the flange back is BF = f
_{0 + Δf = f 0 + m} × determines whether reached δ × Fno (S713), reached in the case no drives the FB (S714), and repeats the FB until a f ₀ + Δf. When f ₀ + Δf is reached, the motor is stopped (S
715), the in-focus determination is performed in the state where the correction has been performed by + Δf (S
716), and proceeds to the next sequence. As described above, an example in which the focus correction amount is displayed at the correction magnification based on the depth of focus,
Although the back focus control type AF single-lens reflex camera of FIG. 3 has been described, the correction magnification can be similarly applied to FIGS. 1 and 2.

[0024]

As described above, according to the present invention, in a camera in which a flange back is defined for a lens mount, a focus correction mode mechanism capable of correcting the flange back by a predetermined correction amount in advance or after focusing is realized. Is what you do. Therefore, the following various effects can be obtained. In conventional cameras, the flange back is fixed,
Focus correction was limited on the lens side. That is, when photographing the closest object, it is impossible to perform correction on the closer side. However, in a camera to which the focus correction mode mechanism according to the present invention is applied, it is possible to make the reference flange back of the lens shorter or longer than the reference flange back. When the present invention is used together with a lens drive AF camera, the flange back on the main body side is a reference position in general photographing, the AF operation is performed by driving the lens, and when performing focus correction, the correction amount is specified in advance. Alternatively, the FB moves back and forth only by specifying the correction amount after the AF operation, and the correction intended by the photographer can be performed.

When the present invention is applied to an MF camera instead of an AF camera, that is, to a camera having no built-in AF sensor, if the mechanism for accurately controlling the position of the FB is used, the distance ring of the lens may be used. After focusing, the FB can be finely adjusted and corrected on the main body side. In addition, correction is possible in consideration of the depth of focus in consideration of the aperture F-number function, and accurate correction cannot be performed by a photographer's manual lens adjustment operation. By simply instructing the correction amount, the correction of the amount intended by the photographer can be performed by a simple operation. Further, continuous focus automatic photographing for photographing while automatically shifting the focal position back and forth by using the focus correction mode mechanism according to the present invention is also possible. When the focus correction mode mechanism according to the present invention is applied to an AF single-lens reflex camera of a back focus control method, if a correction amount is specified in advance, the position of the flange back including the correction amount is determined as the focus position. Thus, correction before and after the flange back can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing an embodiment of a camera employing a focus correction mode mechanism according to the present invention, which is an example of a case where a flange back is manually corrected forward and backward.

FIG. 2 is a schematic front view showing another embodiment of a camera employing a focus correction mode mechanism according to the present invention, in which a flange back is corrected back and forth by a motor drive.

3A and 3B are schematic front views showing an embodiment of an autofocus single-lens reflex camera employing a focus correction mode mechanism according to the present invention, wherein FIG. 3A shows a state in which a rear block B is set to an infinity shooting position, and FIG. Indicates a state set to the closest shooting position.

4A is a partial plan sectional view for explaining the details of the shape of the camera body front block of FIG. 3, and FIGS. 4B and 4C are views of the camera body front block and rear block of FIG. It is the schematic for demonstrating an example of a connection mechanism.

FIG. 5 is a diagram showing an embodiment of a control circuit part of FIG. 3;

FIG. 6 is a flowchart for explaining the operation of the focus correction mode mechanism according to the present invention, in which the absolute amount of the flange back distance is corrected.

FIG. 7 is a flowchart for explaining the operation of the focus correction mode mechanism according to the present invention, in which the in-focus position of the AF in consideration of the depth of focus is corrected.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Lead screw 2 ... FB correction dial 4, 14 ... Film pressure plate 5, 15 ... Film surface 6, 11 ... Linear guide 7, 8, 18, 19 ... Gear 9 ... Film opening 10, 17 ... Movable opening 12 ... FB drive lead screw 13 ... FB movement amount detection encoder 16 ... FB correction drive motor 21 ... Lens mount 22 ... Film surface 23 ... Distance measurement mechanism 25 ... Finder mechanism 26 ... Encoder 27 ... AF drive mechanism 28 ... Position detection switch 29 ... Replacement Lens 30 Aperture 31 Pressure plate 33 Up / down mirror 34 Release button 35, 36 Rail 37 Grip 40 AF control circuit 41 Camera operation CPU 42 Drive circuit 43 FB drive motor drive circuit 44 Focus correction dial 45 ... Release button

Claims (2)

(57) [Claims] At least a photographing lens and the photographing lens are provided.
Camera body front block including lens mount for lens
And a camera body rear block including at least a film opening.
Lock, the camera body front block and the camera book
Adjustable connection to the posterior block
Connecting part between the front and rear blocks,
The distance between the lens mount of the
And a drive mechanism for adjusting the position of the photographing lens.
AF single-lens for focusing by adjusting the lunge back
For reflex cameras, the flange back position specified with respect to the lens mount surface
Enter the correction amount to correct the position forward or backward.
Point correction input means, and calculates the position of the focal point based on the focus information;
When the correction amount is set in advance by the positive input means,
When the correction amount is set, the correction amount is set according to the correction amount.
Forward or back from the focal point position to the flange back position.
Move it back and focus on the moved position as the focal point.
Camera focus correction mode, characterized in that a control means for determining focus, the provided
Mechanism. 2. The operation of the flange back correction dial.
Amount, the amount of motor drive, or the focus
The depth of focus is a function of the lens aperture value
2. The power of claim 1, wherein
Mera's focus correction mode mechanism.