JP3005304B2 - Depth of field confirmation mode mechanism of AF camera - Google Patents

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 of an AF camera capable of confirming a depth of focus with respect to a focal position of an adjusted lens by a finder.

[0002]

2. Description of the Related Art Generally, open metering is performed for an arbitrary aperture value setting, and the exposure value is determined by the calculated value. In addition, the viewfinder may be easy to see even in a bright state due to open metering, and the viewfinder is not checked with an actual aperture. Therefore, at present, a preview button is provided for depth of field confirmation, and the preview button is narrowed down to a set aperture position by operating the preview button. However, since the actual aperture value is used, the field of view in the viewfinder becomes dark, and it is actually difficult to confirm the depth. In addition, even if it could be confirmed in this way, it was different from the image actually displayed on the screen.

Another prior art relatively close to this type of depth of field is a mechanism for automatically controlling the focusing of the lens in order to provide the maximum depth of field of the camera. When a subject at a short distance cannot be detected, a technique is disclosed in which the lens is adjusted to the closest pan-focal position suitable for adjusting the aperture of the lens at that time (Japanese Patent Publication No. 51-14891). ).

[0004]

However, it is far from the required technique for confirming the depth of field. SUMMARY OF THE INVENTION It is an object of the present invention to provide a depth-of-field confirmation mode mechanism of an AF camera that allows a photographer to confirm the depth of field with respect to a set aperture without darkening the screen of a viewfinder.

[0005]

In order to achieve the above object, a depth-of-field confirmation mode mechanism of an AF camera according to the present invention is used in an AF camera which performs a focusing operation in conjunction with a release. and mode setting means, and means for specifying the front limit and the rear limit position of the focus around a center of <br/> focal depth of the same subject, the depth of field check mode setting means is an operation with the same object When the front limit or rear limit position is designated, the value of the depth of focus (± Fδ) determined by the F number determined by the lens and aperture values and the minimum circle of confusion (δ) serving as the focus reference is calculated. And control means for moving the focal position of the lens by the value of the depth of focus (± Fδ), so that the width of the depth of field can be visually recognized by a finder.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
I will explain. In general, what kind of lens and AF camera
Focus position determined by subject distance
A system that moves in search of the best image point and stops at the focal point
It has become. FIG. 1 shows the subject P₀Distance S to lens₀
Image P₀ ^'Distance S to lens ₀ ^'Show the relationship
FIG.

In the AF camera, the image P ₀ ^{′ of the} subject P ₀ is obtained.
Is controlled so as to stop the focal point movement of the lens by calculating the distance S ₀ ^′ . Here, the depth of field of the P ₁ and P ₂ which can ensure the minimum circle of confusion δ by F number determined by the aperture value is present for the lens and exposure setting, self by photographer to verify this There is a demand to take a picture that matches the image of the city. In the present invention, this can be confirmed without darkening.

The focal depths Δs ₁ ′ and Δs ₂ ′ can be expressed by the following equations. Δs ₁ ≒ Δs ₂ ′ = (s ₀ ′ / D) × δ = Fδ Further, the depths of field Δs ₁ and Δs ₂ can be expressed by the following equations. Δs ₁ = f ² s ₀ / ｛f ² + Fδ (s ₀ )｝ Δs ₂ = f ² s ₀ / ｛f ² -Fδ (s ₀ )｝ where δ is the minimum circle _of confusion _{, and in} general, the Leica size is δ = 0.033. It is said. F is determined by the focal length and aperture diameter D
Number

FIG. 2 is a schematic block diagram showing an embodiment of a depth-of-field confirmation mode mechanism of the AF camera according to the present invention. This figure shows only those parts directly related to the present invention. The aperture information of the aperture 1a provided in the lens 1e is sent to the exposure control CPU 4. The 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. The lens information is stored in an AF control CPU 5 from a lens ROM 1b provided on the side of the lens.
Sent to The lens ROM 1b is an IC that stores information about the lens, such as the brightness of the lens and the position of the distance ring. Further, the distance information is sent to the AF control CPU 5 from a distance measuring sensor module 1g provided below the mirror.

The exposure control CPU 4 receives a check signal of a release button. Also, AF
The control CPU 5 is connected to a depth-of-field confirmation mode switch 7 and a front limit and rear limit switch 8. The AF control CPU 5 and the exposure control CPU 4 are connected so as to exchange information with each other. Driver 6 is AF control CP
The lens drive signal is output by the control signal from U5 to drive the motor 1c. Thus, the AF driving unit 1d can drive the focus adjustment lens to adjust the focus.

FIG. 3 is a flowchart for explaining the depth of field confirmation operation. When the AF check is performed by operating the release button 3 (step 1), the AF control CPU
5 performs focus determination based on the distance information and the lens position information (step 2), and when there is no lens at the focus position, sends a control signal to the driver 6 to send a lens drive signal to drive the AF drive unit 1d. (Step 3). As a result, when the focus is achieved, 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 camera is in a depth of field confirmation mode (step 5). The camera enters a shooting standby state (step 6). When the mode is the depth of field mode, it is determined whether or not the front limit and rear limit switches 8 are tilted to the front limit side. Depth of focus + F when tilted to the front limit
The AF driving section 1a is driven via the driver 6 by δ (step 8). As a result, the focal point of the lens moves to the position P ₁ ′ and is focused on the position of the subject P ₁ .

Next, if it is not tilted to the front limit side, it is determined whether or not it is tilted to the rear limit side (step 9).
When it is tilted to the rear limit side, the AF driving section 1a is driven via the driver 6 by the depth of focus -Fδ (step 10). As a result, this time, the focal point of the lens moves to the position P ₂ ′, so that the focal point is focused on the position of the subject P ₂ . On the other hand, when it is not tilted to any side, that is, when the front limit switch and the rear limit switch 8 are at the center position, the camera enters a shooting standby state (step 6). After the lens is moved by the depth of focus + Fδ or −Fδ, the lens returns to the initial position by a release operation (turns off the depth-of-field confirmation mode switch 7), and is in a photographing standby state (step 6).

By the above-mentioned operation, the photographer can determine the distance from the center of the focal position in the current aperture setting to
The person behind can check how far focus is achieved without darkening the viewfinder. If you want to reduce the depth of field according to the photographer's intention, move the aperture to the open side, and if you want to increase the depth, operate the aperture to change the depth of field as needed. The state of focus can be confirmed while the subject remains bright.
When the depth-of-field confirmation mode is set, the shutter release is not performed even if the release button is pushed to the final shooting start position, thereby preventing malfunction.

[0015]

As described above, according to the present invention, in an AF camera which performs a focusing operation in conjunction with a release, a front limit position and a rear limit position of a focus are designated around a center of a depth of focus and a depth of field is specified. 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 minimum circle of confusion (δ) serving as the focus reference is calculated, and the focal position of the lens is calculated. The depth of focus (± Fδ)
, The width of the depth of field can be visually recognized without darkening the viewfinder.

[Brief description of the drawings]

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

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

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

[Explanation of symbols]

 DESCRIPTION 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

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B ^7/ 28-7/40 G03B 3/00 G03B ^7/ 00-7/28 G03B 13/36 G03B 17/20

Claims (1)

(57) [Claims] In an AF camera which performs a focusing operation in conjunction with a release, a depth-of-field confirmation mode setting means and a front limit position and a rear limit position of a focal point are designated around a center of a focal depth of the same subject. Means for operating the same depth of field by operating the depth of field confirmation mode setting means.
If the front limit or rear limit position Utsushitai is specified, a minimum circle of confusion ([delta]) and de determined by the depth of focus (± serving as the F number and focal point of reference determined by the value of the lens and the diaphragm
Control means for calculating the value of Fδ) and moving the focal position of the lens by the value of the depth of focus (± Fδ), so that the width of the depth of field can be visually recognized by a finder. Depth of field confirmation mode mechanism of the AF camera to perform.