JP4887570B2 - Interchangeable shooting lens - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention also relates to a replaceable photographing lens that can be attached to the camera.
[0002]
[Prior art]
There is known a camera in which a horizontal sensor extending in a horizontal direction and a vertical sensor extending in a vertical direction are arranged in a cross shape with respect to a shooting screen, and the focus detection of the same focus detection area is performed by these vertical and horizontal sensors. Yes. In such a focus detection method, there may be a deviation between the image plane position of the image whose focus is detected by the horizontal sensor and the image plane position of the image whose focus is detected by the vertical sensor. The amount of deviation varies depending on the photographic lens attached to the camera, but generally increases as the focus detection area is further away from the optical axis and the photographic magnification is higher.
[0003]
[Problems to be solved by the invention]
Originally, the in-focus position of the photographic lens with respect to a subject at the same distance is only one point in the optical axis direction, but if there is a deviation in the image plane position of the two sensors, in-focus determination is made at two locations. For this reason, for example, in a camera that employs a focus aid, the focus display is lit at two different positions during manual focusing, and the photographer may be confused.
[0004]
An object of the present invention is to provide a camera, an interchangeable photographic lens, and a camera system in which the inconvenience due to the shift amount of the imaging plane position between the two sensors is eliminated.
[0005]
[Means for Solving the Problems]
The interchangeable photographic lens according to the first aspect of the present invention can be attached to a camera having a first sensor and a second sensor arranged to extend in different directions to perform focus detection in the same focus detection area. Output of deviation information relating to the deviation amount between the image forming position of the M image plane and the image forming position of the S image plane with respect to the same subject to the camera as information specific to the interchangeable photographing lens Equipment . The output deviation information is information for preventing in-focus determination at two lens positions.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows the configuration of a camera system comprising a camera body 10 and an interchangeable photographic lens 20. First, the optical system will be described. The taking lens 20 includes first to third lens groups L1, L2, and L3, and each lens group L1 to L3 is individually moved in the optical axis direction to perform zooming. Focusing is performed by moving the two lens units L2 independently.
[0007]
The light beam that has passed through the lens groups L1 to L3 in order is incident on the camera body 10, part of which is reflected by the main mirror 11 and guided to the finder optical system (not shown), and the other part is transmitted through the main mirror 11. Then, it is reflected by the sub-mirror 12 and enters the focus detection device 13.
[0008]
The focus detection device 13 employs a well-known phase difference detection method, and in the present embodiment, as shown in FIG. 2, focus detection of three regions (focus detection areas) AR1, AR2, AR3 in the screen is possible. The focus detection area AR1 is located at the center of the screen, and the focus detection areas AR2 and AR3 are set at positions separated from each other by a distance h. Reference numerals 13h and 13v in the figure denote images obtained by projecting the sensors constituting the focus detection device 13 onto the photographing screen, corresponding to the three areas AR1 to AR3, respectively, and horizontal sensors 13h extending in the horizontal direction of the screen, A vertical sensor 13v extending in the vertical direction is arranged in a cross shape. Each of the sensors 13h and 13v is composed of a pair of CCDs, receives the incident light beam, and outputs a focus detection signal corresponding to the received light amount. Hereinafter, the sensors 13h and 13v that perform focus detection in the left and right areas AR2 and AR3 are referred to as side area sensors.
[0009]
The camera performs focusing based on the focus detection result in any one of the three areas AR1 to AR3. Which area to select may be determined by the photographer's operation, or the camera may determine based on the focus detection result.
[0010]
Focus detection signals (electrical signals corresponding to received light fluxes of the subject) from the sensors 13h and 13v are input to a microprocessing unit (hereinafter referred to as MPU) 14. For example, the MPU 14 inputs a focus detection signal in response to a half-press operation of a release button (not shown), and calculates a defocus amount corresponding to a shift amount of the photographing lens 20 from the in-focus position based on the input signal. The calculation result is sent to the MPU 21 on the photographing lens 20 side, and the lens side MPU 21 outputs a drive signal corresponding to the defocus amount to the motor drive circuit 22. The motor drive circuit 22 rotates the motor 23 based on the input drive signal, and drives the lens groups L <b> 1 to L <b> 3 via the transmission mechanism 24. The motor encoder 25 detects the amount of rotation of the focusing motor 23 and inputs it to the lens side MPU 21, and based on this, the MPU 21 feedback-controls the motor 23. The photographing lens 20 is focused on the subject by this focusing control.
[0011]
The zoom encoder 26 detects the zooming state (focal length) of the taking lens 20 and inputs it to the MPU 21. The distance encoder 27 detects the position of the second lens unit L2 as shooting distance related information and inputs it to the MPU 21. In the MPU 21, image plane displacement information (described later) corresponding to each focal length and shooting distance is stored in advance as a table.
[0012]
Next, the displacement of the imaging plane position with respect to the vertical sensor 13v and the horizontal sensor 13h will be described.
In general, in a photographing optical system, the position of the image plane of the meridional ray bundle (M image plane) and the position of the image plane of the sagittal ray bundle (S image plane) coincide with each other for an object at the same distance. Is ideal, but it is not always the same. The presence / absence of this image formation position is determined by the lens to be mounted. In recent years, for example, as shown in FIG. There are many photographic lenses that cause deviation. Such a shift amount of the image forming position becomes larger as the photographing magnification becomes high, that is, the telephoto side and the photographing distance is closer, and as the image height becomes higher as can be seen from FIG. The photographic lens 20 of this embodiment has the characteristics shown in FIG.
[0013]
FIG. 2 shows an example in which a side area sensor is present at the position of the image height h, and the deviation amount of the image plane position of the S / M image at this position is ΔD (FIG. 3). Consider the case where a person (subject) wearing a horizontal stripe shirt exists at the position of the image height h as shown in FIG. For the horizontal stripe object, the horizontal sensor 13h cannot detect the focus because of the low contrast, but the vertical sensor 13v can detect the focus because the contrast can be detected. In the case of a horizontal stripe, an S image is obtained, and the image formation position is Ds in FIG. On the other hand, in the case of a person wearing a vertical-striped shirt as shown in FIG. 5, the focus detection is possible only with the lateral sensor 13h contrary to the above, and in this case, since the M image is obtained, the imaging position is Dm. It becomes. In the examples of FIGS. 4 and 5, since focus detection cannot be performed by one of the sensors, the problem due to the shift of the imaging position does not occur.
[0014]
Next, consider a case where a person wearing a diagonally striped shirt exists at the position of the image height h as shown in FIG. In this case, the image is an intermediate image, not an S image or an M image, and focus detection can be performed by both the vertical direction sensor 13v and the horizontal direction sensor 13h. For this reason, the conventional camera may recognize the imaging position as Ds or Dm, and even with the same subject, the in-focus position of the lens differs depending on the focus detection timing. is there. For example, when focus detection and focusing are attempted again on the same subject while the photographing lens 20 is focused on the subject, the photographing lens 20 should not move if the photographing distance remains unchanged. However, the photographing lens 20 may move by an amount corresponding to the amount of deviation ΔD of the imaging position, which gives the photographer distrust. In addition, in a camera with a focus aid, when the lens is driven from one end (infinity or closest) side, focus marks are displayed at two locations (Ds, Dm), and the photographer is confused. There is. In order to eliminate such an image plane position shift, it is necessary to narrow the zoom range and increase the size of the lens barrel.
[0015]
Therefore, in the present embodiment, the image formation surface position deviation information unique to the lens is stored in the MPU 21 of the photographic lens 20, and either one of the vertical and horizontal sensors is disabled based on the information. The above-described problem is prevented from occurring even in a camera in which a surface position shift occurs. The details will be described below.
[0016]
FIG. 7 shows an example of deviation information stored in the lens side MPU 21. In this example, a flag (1 or 0) is assigned corresponding to the zooming state of the lens (Z0 (WIDE) to Z10 (TELE)) and the shooting distance (D0 (infinity) to D10 (closest)). The flag is more than the range (imaging plane position width) where the camera main body side determines that the in-focus state is in particular when the shift amount ΔD of the imaging plane position (here, the best image plane position) is relatively small. “0” is set when the amount of deviation is small and it is considered that the above-described problem does not occur. On the other hand, when the deviation amount ΔD is larger than the focus determination range and the above problem is considered to occur, “1” is set. As can be seen from the figure, the flag is set to 1 on the telephoto side and the close side, that is, when the photographing magnification is high. The state of this flag is determined based on the result of obtaining the deviation amount ΔD in advance by calculation or experiment.
[0017]
FIG. 8 is a flowchart showing the focus detection operation in this embodiment.
In step S1, the side area (AR2 or AR3) is selected as the focus detection area, and when the half-press operation of the release button is confirmed in step S2, the processes in and after step S3 are executed. In step S <b> 3, the imaging plane position deviation information (flag) is read from the lens-side MPU 21. That is, the lens-side MPU 21 reads the outputs of the zoom encoder 26 and the distance encoder 27, determines the current state of the photographing lens 20 (focal length and photographing distance), and sets the flag state corresponding to the state from the table of FIG. This is selected and output to the camera body MPU 14.
[0018]
The main body side MPU 14 determines whether or not the flag input from the lens side MPU 21 is 1 (step S4). If the flag is 0, the imaging plane position shift amount ΔD in the current state of the photographing lens 20 is determined. Is less than or equal to a predetermined value, both the vertical and horizontal sensors 13v and 13h corresponding to the focus detection area are validated (step S5).
On the other hand, if the flag is 1, it is determined that the imaging plane position deviation amount ΔD exceeds a predetermined value in the current state of the photographing lens 20, and either the vertical or horizontal sensor (in this case, the horizontal sensor) is disabled. (Step S6).
[0019]
In step S7, focus detection processing and focusing processing are performed based on the settings in steps S5 and S6. That is, when passing through step S6, focusing is performed based only on the focus detection output of one sensor. In this case, focus detection by the other sensor may be prohibited, or focus detection may not be prohibited and the output may not be used.
On the other hand, when passing through step S5, focusing is performed based on the focus detection outputs of both the vertical and horizontal sensors as before.
[0020]
Here, when the flag is determined to be 1, basically any of the vertical and horizontal sensors may be invalidated. However, if one of the sensors cannot detect the focus at low contrast, the sensor is necessarily invalidated. It becomes. In the above, the processing of steps S3 to S6 is performed immediately after the half-pressing operation. However, if both sensors are enabled to perform focus detection immediately after the half-pressing operation and focus detection is possible with both sensors, steps S3 to S6 are performed. If the process of S6 is performed and one of the sensors cannot detect the focus due to low contrast, the process of steps S3 to S6 may not be performed.
[0021]
Note that the above processing is performed when the side areas AR2 and AR3 are selected. When the center area AR1 is selected, the image height is almost zero, so that the image plane position shift does not occur. The processing shown in steps S3 to S6 is not performed.
[0022]
According to the above, when the deviation amount ΔD between the image plane position of the image detected by the horizontal sensor 13h and the image plane position of the image detected by the vertical sensor 13v exceeds a predetermined value, Since one of the sensors becomes invalid, the focus determination is not performed at two places as in the conventional case. Therefore, for example, when focus detection and focusing are attempted again on the same subject while the photographing lens 20 is focused on the subject, the photographing lens 20 does not move if the photographing distance remains unchanged. Further, there is no inconvenience that focus marks are displayed at two positions in the focus aid.
[0023]
In the above embodiment, the vertical and horizontal sensors 13v and 13h constitute the first and second sensors, the main body side MPU 14 constitutes a control device, and the lens side MPU 21 constitutes an output device.
[0024]
The deviation information input from the lens side MPU 21 is not limited to the flag as shown in FIG. 7, and may be information obtained by quantifying the deviation amount ΔD itself as shown in FIG. In this case, the main body side MPU 14 inputs the deviation amount ΔD from the lens side MPU 21, and if the deviation amount ΔD is equal to or smaller than a predetermined value, both sensors are enabled. ) One sensor may be invalidated. According to this method, there is an advantage that a threshold value for determining whether to disable one of the sensors can be set according to circumstances on the camera body side. For example, in a camera with a narrow range (image forming position width) for determining focus, that is, a camera with severe focus determination, the focus determination marks are likely to be lit at two locations when using the focus aid. May be set to a low value, and conversely, in a camera where the focus determination is not so severe, the threshold value for the determination may be set high.
[0025]
In addition, although the camera which can replace | exchange a lens was demonstrated above, this invention is applicable also to the camera with which the lens was fixedly provided. In this case, the image plane position shift information may be stored in the main unit MPU. Further, although the description has been made with the camera capable of autofocusing, it can be applied to a manual focus camera as long as it has a focus aid. Alternatively, an autofocus camera having no focus aid function may be used. Furthermore, the arrangement of the first and second sensors is not necessarily limited to the horizontal direction and the vertical direction, and may not be a cross shape.
[0026]
【Effect of the invention】
According to the present invention, when the camera receives from the photographic lens displacement information related to the amount of displacement between the imaging position of the M image plane and the imaging position of the S image plane with respect to the same subject, the displacement of the imaging plane position. It is possible to easily avoid the problems caused by .
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a camera system according to an embodiment.
FIG. 2 is a diagram showing an arrangement of focus detection areas and focus detection sensors in a camera.
FIG. 3 is a diagram for explaining a shift in image plane position between an S image and an M image.
FIG. 4 is a diagram showing an example in which a horizontal stripe subject exists in a side area.
FIG. 5 is a diagram showing an example in which an object with vertical stripes exists in a side area.
FIG. 6 is a diagram illustrating an example in which a subject with diagonal stripes exists in a side area.
FIG. 7 is a diagram showing deviation information stored in the lens side MPU.
FIG. 8 is a flowchart showing a procedure of focus detection and focusing processing.
FIG. 9 is a diagram showing another example of shift information.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Camera main body 13 Focus detection apparatus 14 Camera main body side MPU
20 Shooting lens 21 Lens side MPU
23 Focusing motors L1-L3 Lens group

Claims (6)

An interchangeable photographic lens that can be attached to a camera having a first sensor and a second sensor arranged to extend in different directions so as to perform focus detection in the same focus detection area, the deviation information related to the shift amount between the imaging position of the imaging position and the S image plane of the image plane, an output device for outputting to the camera as the interchangeable photographing lens-specific information, the deviation information to be the output Is information for preventing in-focus determination at two lens positions .   The interchangeable photographic lens according to claim 1, wherein the output deviation information is information indicating whether the deviation amount exceeds a predetermined value.   The interchangeable photographic lens according to claim 1, wherein the output shift information is information indicating the shift amount.   The interchangeable photographic lens according to claim 1, wherein the photographic magnification is variable, and the output deviation information is information according to a set photographic magnification.   5. The interchangeable photographic lens according to claim 1, further comprising a storage device that stores the shift amount according to a focal length and a photographic distance of the interchangeable photographic lens. 6.   6. The exchange according to claim 1, wherein the output deviation information is information for determining whether to invalidate one of the first sensor and the second sensor. Type photography lens.

Images