JPH04254813A - Subject view depth confirmation mode mechanism for af camera - Google Patents

Abstract

PURPOSE:To confirm subject view depth for a set diaphragm without darkening a finder. CONSTITUTION:A subject view depth confirmation mode switch 7 is to set the mode. A front and back limit switch 8 is to specify the front and back limit focal point mainly for the center of focus depth. When the subject view depth confirmation mode switch 7 is operated and the front and back limit point is specified, an AF control CPU 5 calculates the value of focus depth (+ or -Fdelta) determined by a F number depending on a lens and a diaphragm and a minimum blur circle (delta) as a focus reference, and moves the lens corresponding to a correction value, allowing the depth of subject field depth to be visually acknowledged.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a depth-of-field confirmation mode mechanism for an AF camera that allows the depth of focus relative to the adjusted focal position of a lens to be confirmed using a finder.

0002

2. Description of the Related Art Generally, aperture metering is performed for any aperture value setting, and exposure is determined based on this calculated value. In addition, the viewfinder was not checked using the actual aperture because it was easy to see the viewfinder in a bright state, especially due to wide-open photometry. Therefore, to check the depth of field, a preview button is provided, and by operating this button, the aperture position is narrowed down and confirmed. However, since the actual aperture value is used, the field of view in the viewfinder becomes dark, making it difficult to confirm the depth of the image. Moreover, even if the image could be confirmed in this way, the image actually displayed on the screen was different.

[0003] Another relatively similar prior art related to this type of depth of field is a rangefinder equipped with a mechanism that automatically controls the focus adjustment of the lens to provide the maximum depth of field of the camera. A technique has been disclosed in which, when an object at a close distance cannot be detected, the lens is adjusted to the nearest pan-focal position that matches the adjustment of the lens aperture at that time (Japanese Patent Publication No. 51-14891). ).

0004

[Problems to be Solved by the Invention] However, this technique is far from the required technique for confirming the depth of field. SUMMARY OF THE INVENTION An object of the present invention is to provide a depth of field confirmation mode mechanism for an AF camera that allows a photographer to confirm the depth of field for a set aperture without darkening the finder screen.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the depth of field confirmation mode mechanism for an AF camera according to the present invention provides a mechanism for confirming the depth of field in an AF camera that performs a focusing operation in conjunction with the release. a mode setting means, a means for specifying a front limit position and a rear limit position of the focus centering on the center of the depth of focus, and the depth of field confirmation mode setting means is operated to specify the front limit position or the rear limit position. In this case, the depth of focus (±Fδ) is determined by the F number determined by the lens and aperture value and the circle of least confusion (δ), which is the focal point reference.
The focal position of the lens is calculated based on the focal depth (±F
δ), and is configured so that the width of the depth of field can be visually confirmed through a finder.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in more detail below with reference to the drawings and the like. In general, an AF camera has a system in which the focal position determined by the distance to the subject moves to find the best image point and stops at the in-focus point, regardless of the lens and aperture value. Figure 1 shows the distance S from the subject P0 to the lens.
0 is a diagram showing the relationship between the distance S0' of the image P0' to the lens and the distance S0' of the image P0' to the lens.

[0007] In the AF camera, the image P0 of the subject P0 is
The distance S0 ' is calculated and control is performed to stop the movement of the focal point of the lens. Here, there are depths of field P1 and P2 that can ensure the minimum circle of confusion δ depending on the F number determined by the lens and the aperture value for exposure settings, and by checking this, the photographer can improve his/her own image. There is a desire to take photos that match the situation. The present invention allows this to be confirmed without darkening.

The depths of focus Δs1' and Δs2' can be expressed by the following equations. Δs1'≒ Δs2'=(s0'/D)×δ=Fδ Further, the depth of field Δs1 and Δs2 can be expressed by the following equation. Δs1 = f2 s0 / {f2 +Fδ(s0)}Δ
s2 = f2 s0 / {f2 −Fδ(s0)} where δ is the circle of least confusion, generally δ = 0.033 for Leica format
It is said that F is the F number determined by the focal length and aperture D

FIG. 2 is a schematic block diagram showing an embodiment of a depth of field confirmation mode mechanism of an AF camera according to the present invention. In this figure, only the parts directly related to the present invention are shown. Aperture information of the aperture 1a provided in the lens 1e is sent to the exposure control CPU4. Further, light amount information is also sent to the exposure control CPU 4 from the light receiving section 1f provided at the rear of the pentaprism. Lens information is sent to the AF control CPU 5 from the lens ROM 1b provided on the side of the lens. The lens ROM 1b is an IC that stores information regarding the lens, such as the brightness of the lens and the position of the distance ring. Furthermore, distance information is sent to the AF control CPU 5 from a distance measurement sensor module 1g provided at the bottom of the mirror.

A release button check signal is input to the exposure control CPU 4. Also, AF
The control CPU 5 is connected to a depth of field confirmation mode switch 7 and front and rear limit switches 8. The AF control CPU 5 and the exposure control CPU 4 are connected to exchange information with each other. Driver 6 is AF control CP
A lens drive signal is output based on the control signal from U5 to drive the motor 1c. Thereby, the AF drive unit 1d can drive the focusing lens to focus.

FIG. 3 is a flowchart for explaining the depth of field confirmation operation. When you operate the release button 3 to perform an AF check (step 1), the AF control CPU
5 makes a focus judgment based on the distance information and lens position information (step 2), and if the lens is not in the focus position, sends a control signal to the driver 6 to send out a lens drive signal and drive the AF drive unit 1d. (Step 3). As a result, if the object is in focus, the focus is displayed in the viewfinder (step 4).

Next, it is determined whether or not the depth of field confirmation switch 7 is turned on, that is, whether or not the depth of field confirmation mode is set (step 5). The camera enters the shooting standby state (step 6).
). When the depth of field mode is set, it is determined whether the front limit and rear limit switch 8 is turned to the front limit side. When tilted to the front limit side, depth of focus + Fδ
The AF drive unit 1a is driven by the same amount through the driver 6 (step 8). As a result, the focal point of the lens moves to position P1' and focuses on the position of subject P1.

Next, if the vehicle is not tilted toward the front limit side, it is determined whether or not the vehicle is tilted toward the rear limit side (step 9).
When it is tilted to the rear limit side, the AF drive unit 1a is driven by the depth of focus -Fδ via the driver 6 (step 10). As a result, the focal point of the lens now moves to position P2' and focuses on the position of object P2. On the other hand, when it is not tilted to either side, that is, when the front limit and rear limit switches 8 are in the center position, the camera enters a shooting standby state (step 6). After the lens has been moved by the depth of focus +Fδ or -Fδ, the lens returns to its initial position by a release operation (turning off the depth of field confirmation mode switch 7) and enters a photography standby state (step 6).

[0014] Through the above operations, the photographer can determine how far in front of the center of the focal point with the current aperture setting.
You can check how far the viewfinder is in focus without darkening the viewfinder. If you want to make the depth of field shallower depending on your intention, you can move the aperture to the open side, and if you want to make the depth of field deeper, you can stop down. You can check the focus while the light remains bright. Furthermore, when the depth of field confirmation mode is set, the shutter will not be released even if the release button is pushed to the final shooting start position to prevent malfunctions.

[0015]

As explained above, the present invention provides an AF camera that performs focusing operation in conjunction with the release, by specifying the front and rear limit positions of the focus center around the center of the depth of field, thereby improving the depth of field. By setting the confirmation mode, the value of the depth of focus (±Fδ) determined by the F number determined by the lens and aperture values and the circle of least confusion (δ) that is the focal point reference is calculated, and the focal position of the lens is determined. The depth of focus (±Fδ)
Since the lens is configured to move by the value of , the width of the depth of field can be visually confirmed without darkening the viewfinder.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an optical path of a lens system for calculating a depth of field value.

FIG. 2 is a schematic block diagram showing an embodiment of a depth of field confirmation mode mechanism of an AF camera according to the present invention.

FIG. 3 is a flowchart for explaining a depth of field confirmation operation.

[Explanation of symbols]

1...Camera 3...Release button 4...Exposure control CPU 5...AF control CPU 6...Driver 7...Depth of field confirmation mode switch 8... Front limit and rear limit switch

Claims (1)

[Claims] 1. An AF camera that performs a focusing operation in conjunction with a release, comprising means for setting a depth of field confirmation mode, and means for specifying front and rear limit positions of focus around the center of the depth of focus; When the front limit or rear limit position is specified by operating the depth of field confirmation mode setting means, the F number determined by the lens and aperture values and the circle of least confusion (δ) serving as the focus reference are used. The depth of focus determined (
±Fδ) and moves the focal position of the lens by the depth of focus (±Fδ), and is configured such that the width of the depth of field can be visually confirmed through the viewfinder. Depth of field confirmation mode mechanism for AF cameras.