JPH02110414A - Automatic focusing device for camera - Google Patents

Abstract

PURPOSE:To execute field depth photographing with simple operation by providing a field depth arithmetic and control means to determine a diaphragm value and a focusing subject distance and to move a focus lens so that the both subjects of a maximum distance and a minimum distance, which are decided by a perspective distance deciding means, can be included in the field depth of a photographic lens. CONSTITUTION:A distance measuring means 10 measures plural subject distances in a photographic frame respectively and the distances are stored in a subject distance storing means 11. The stored subject distances are respectively outputted to a perspective deciding means 12 and the maximum and minimum distances are decided out of the distances. In a field depth arithmetic and control means 13, the inputs of the maximum and minimum subject distances and photographic lens information are received and prescribed arithmetic is executed. Then, a diaphragm F and a focus subject distance (a) are obtained and a photographic lens (focusing lens 15) is focused to the focus subject distance through a lens driving means 14. After that, the diaphragm is narrowed down through a diaphragm driving means 16. Thus, the field depth photographing can be speedily executed by the simple operation.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an autofocus device for a camera, and more specifically to an autofocus device capable of autofocus photography using depth of field.

"Prior art and its problems" The autofocus device in a conventional single-lens reflex camera splits the subject image ray included in the distance measurement zone into two, and guides each of the two divided image rays to a distance measurement sensor (CCD). Based on the two-split subject image signal from the distance measurement sensor, the focus calculation section performs a predetermined focus calculation to obtain a day focus value, and based on this day focus value, the AF motor is driven to adjust the focus lens. This method focused by moving to the focus position.

Therefore, in a camera with a conventional autofocus device,
When photographing multiple subjects at different distances, such as one person and a mountain in the background, the focus is set between the person and the background to clearly capture both the person and the background, in other words, photography using depth of field ( (hereinafter referred to as "depth of field photography") was not possible.

Autofocus devices for cameras that enable the above-described depth of field photography have been developed in recent years.

However, this conventional camera equipped with an autofocus device capable of performing depth-of-field photography cannot perform depth-of-field photography with -1 operations. The operation will be explained with reference to FIGS. 7(A) and (B).

First, decide on the farthest subject (distant view) and the closest subject (nearview) that you want to photograph clearly with the desired composition (
Figure 7(A)). In this explanation, the foreground is a person and the distant view is a mountain. In this desired composition, since a person is in the distance measurement zone 31, the user first presses the release button to measure the distance of the person. Next, move the camera to distance measurement zone 3 on the mountain in the distance.
1 (Fig. 7 (B)), press the release button, and measure the distance. After that, in order to return the camera to the desired composition including the distant view and the foreground (FIG. 7(A)), it was necessary to press the release button to release the shutter. In other words, I had to decide on the composition three times and press the release button after each composition.

In other words, the above-mentioned conventional apparatus cannot photograph a moving object because its operation is complicated and requires skill, and even if the user is skilled, it takes time.

``Object of the Invention'' The present invention has been made based on the above-mentioned problems of the conventional camera autofocus device, and it is an object of the present invention to provide a camera autofocus device that can quickly perform depth-of-field photography with simple operations. With the goal.

"Summary of the Invention" In order to achieve the above object, the present invention provides a distance measuring means that has a plurality of distance measuring zones and measures a subject distance for each distance measuring zone, and a distance measuring means that measures a subject distance in each distance measuring zone; A subject distance storage means for storing respective distances, a lens drive means for driving a focal lens of a photographing lens to a focusing position, and a farthest distance and a nearest distance are determined from a plurality of subject distances stored by the subject distance storage means. determining an aperture value and a focused subject distance so that both the farthest and closest objects determined by the distance determining means are included within the depth of field of the photographing lens, and the aperture is adjusted; Depth of field calculation/control means for narrowing the aperture to the aperture value via the aperture drive means and moving the focusing lens to a position where the object is focused at the in-focus object distance via the lens drive means. It has the following characteristics.

According to the above configuration, the aperture value and focused subject distance required for distance measurement of the farthest and closest objects and depth of field photography can be set by operating -degrees, so as in normal shooting, - Depth of field shooting can be done by setting the composition and operating the release switch.

“Embodiments of the invention” The invention will now be described with reference to illustrated embodiments.

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a block diagram showing the main configuration of a single-lens reflex camera to which the present invention is applied.

The distance measuring means 10 measures a plurality of object distances within one photographic frame, and each of the measured object distances is output to and stored in the object distance storage means 11.

The subject distance stored in this distance measurement distance storage means 11 is
Each of the distances is output to the distance determining means 12, from which the farthest distance and the shortest distance are determined. Perspective determination means 12
The farthest distance and closest distance determined by are outputted to the depth of field calculation/control means 13 which performs predetermined calculations of the automatic focusing device of the present invention and comprehensively controls the operation.

The depth of field calculation/control means 13 receives input of the farthest and nearest object distances and photographing lens information (focal length f, minimum circle of confusion d, minimum aperture F value, etc.) and executes predetermined calculations. The aperture F and the in-focus subject distance a are determined so that the subject is included in the depth of field of the photographic lens.

Then, the depth of field calculation/control means 13 drives the photographing lens (focusing lens 15) via the lens drive means 14 to a position where it is brought into focus at the above-mentioned in-focus object distance a, and the aperture drive means 16 causes the aperture Narrow down to F value.

With the above operations, both the farthest object and the closest object are included within the depth of field of the photographic lens.

Next, an embodiment in which the automatic focusing device described above is mounted on a single-lens reflex camera will be described with reference to FIG. 2.

The main control unit 20, which also functions as the depth of field calculation/control means 13 and performs system control and calculations for the entire camera, includes a CCD 21 as a sensor section of the distance measuring means 11, and a photometric sensor as sensors. 22 are connected.

The CCD 21 has three sets of light receiving sections, and the subject images within the three distance measurement zones 30a, 30b, and 30c are divided into two and formed on each light receiving section. The photometric sensor 22 has a photoelectric conversion element for measuring subject brightness, and the output of the photoelectric conversion element is logarithmically compressed and A/D converted and output to the main control unit 20.

The main control unit 20 includes, as a drive device, a lens drive means 1 for driving a focusing lens 15 of a photographing lens.
A lens drive circuit 23 as reference numeral 4, an aperture drive circuit 24 that drives the aperture of the photographic lens, and an exposure circuit 25 that exposes the film by running the shutter curtain are connected.

The switches include a release button 26, which activates the main control unit 20, CCD 21, photometric sensor 22, and lens drive circuit 23 when pressed halfway, and activates the aperture drive circuit 24 and exposure circuit 25 when pressed fully, and an exposure mode; A mode selection switch 27 for selecting a mode such as AF mode is connected.

Further, a lens ROM 28 mounted on the photographing lens is connected to the main control unit 20 through a connection via a connection bin provided on the mount surface. This lens RO
From M28, lens information such as the focal length f, aperture, minimum aperture F value, and minimum circle of confusion d of the photographing lens is entered manually.

Reference numeral 29 denotes a display in the finder, which displays information related to exposure such as shutter speed, as well as an aperture warning when an appropriate aperture does not exist in depth-of-field photography, which will be described later, and a camera shake warning when the shutter speed is slow.

The main control unit 20 includes a CPU, ROM, RA
A microcomputer equipped with R, OM, etc.
Based on the program stored in the camera, various calculations such as distance measurement calculations, storage of measured distances, nearest and farthest distance determination, depth of field calculations, and drive control of lenses, apertures, shutter curtains, etc. are executed.

Next, we will discuss the operation of this embodiment with the above configuration in the third section.
This will be explained with reference to the figures.

When a user wants to take a picture with a composition that focuses on a person and the background (trees and mountains), the user first selects the depth of field priority mode. Next, point the camera at the desired composition. At that time, compose the shot so that the farthest subject (mountain), the closest subject (person), and the subject in between (tree) that you want to focus on are in one of the distance measurement zones 30a, 30b, and 30c ( (See Figure 3). Once the composition is decided, press the release button 26 halfway.

Then, main III (wholesale unit 20 is CCD2
1 is activated, a pair of subject image signals are input to each of the distance measuring zones 30b, 30b, and 30a in this order, and subject distances are calculated and stored in order.

After determining and storing all the object distances, the main control unit 20 determines the farthest pressure IILmax and the closest distance resistance n from among the object distances. Then, based on this distance L min and L max,
Using a predetermined calculation formula, the aperture F value and in-focus subject distance a
seek.

Then, the focusing lens 15 is driven via the lens drive circuit 23 based on this in-focus object path 1iifta, and the object is brought into focus at the in-focus object distance a.

Furthermore, the main control unit 20 activates the photometric sensor 22 to output a subject brightness signal, and calculates a shutter speed by a predetermined exposure calculation based on this subject brightness signal, the aperture F value, and film sensitivity information.

When the user fully presses the release 26 after the above focusing operation and exposure calculation are completed, the main control unit 20
The aperture drive circuit 24 and the exposure circuit 25 are driven using the aperture F value and shutter speed determined by the above calculation, and the person, tree, and mountain are clearly exposed on the film.

The above are the main operations of the camera to which the present invention is applied, and the depth of field can be determined by the following formula.

Ru.

D = Depth of field (+: Front depth, -: Back depth) a: Subject distance (mm) F: Aperture value (F value) f: Focal length (mm) d: Circle of least confusion (mm) (f = (0.035 mm with a 35n+m lens) Here, if the front depth is DI and the rear depth is D2, the above equation (1) can be transformed as follows. In the above equation,
The focal length f and the circle of least confusion d are constants unique to the lens, and the aperture F value is a value that can be set within the aperture range of the lens on the camera side. Further, front depth DI≦nearest distance L min, and rear depth D2≧farthest distance L max
, I have to yell.

By combining equations (2) and (3) above and solving them based on the above conditions, the in-focus subject distance a and the aperture F value can be determined.

At the aperture F value determined above, if the focusing lens 15 is moved to the position where the object is focused at the in-focus object distance a, the farthest distance L
max and the closest distance L min can be contained within the depth of field.

In addition, if the aperture F value obtained by the above calculation is larger than the minimum aperture F value of the lens, or if the difference between the farthest distance L max and the closest distance L min is too large, There are cases where it is not possible to fit both of the closest objects within the depth of field. In such a case, display an aperture warning on the viewfinder display 29.
Alternatively, the shutter may not be released to prevent photographing errors.

Next, the operation of the main control unit 20 that controls the operation of the automatic focusing device will be explained in more detail based on the flowcharts shown in FIGS. 4 to 6. First, when the power is turned on, the main control unit 20 accepts the mode selection switch 270 input. Here the user:
By operating the mode selection switch 27, the depth of field photography mode (depth of field (priority program)) is selected (step 51).By operating this switch, the main control unit 20 prepares the depth of field priority program. At step 52), the process proceeds to END processing. When the release button 26 is pressed after this END processing, the main control unit 2
0 executes focus and exposure calculation processing based on a depth of field priority program.

Furthermore, when the power is turned on, the main control unit 20 starts an interwoven timer and executes the status input process of the release button 26 at predetermined time intervals (step 61), and if the release button 26 is pressed halfway, The process proceeds to photometry and focusing processing (step 62), and if the button is not pressed halfway, the process proceeds to END processing and waits until the timer interrupt is activated.

If it is determined in step 62 that the release button 26 is pressed halfway, focusing processing is started using the depth of field priority program selected in the program selection operation. Here, in order to facilitate understanding of the gist of the present invention, other determination processing related to photography, such as determination processing of so-called single mode or continuous shooting mode, etc., will be omitted.

In step 71, first, the CCD 21 is activated to start distance measurement, and distance measurement calculations are executed in the order of distance measurement zones 30c, 30b, and 30a.Step 72) The calculated values are stored in the RAM. The process then proceeds to step 73.

In step 73, the farthest distance L max and closest distance L min are determined from the subject distance memory value, and the process proceeds to step 74, where the focal length, open aperture F value, and minimum aperture F value are retrieved as lens information from the lens ROM 28. and the circle of least confusion d, and the process proceeds to step 75.

In step 75, the above calculation formula is added to the focal length f, the circle of least confusion d, the virtual aperture F value, the farthest and closest subject distances Lmax,
, L min, to obtain the subject distance a and the aperture F value, and the process proceeds to step 76.

In step 76, it is checked whether the aperture F value is included in the aperture value range of the photographic lens, and if it is, the process proceeds to step 77. If it is not included, proceed to step 81, display an aperture warning on the viewfinder display 29, and press EN.
Proceed to process D. In other words, if the calculated aperture F value exceeds the range of the aperture F value of the photographic lens, exposure will not be possible (
The exposure circuit 25 is set in an inactive state to prevent blurry photography.

In step 77, the aperture F value and the IS of the film are determined.
The shutter speed is determined based on the O sensitivity, and in step 78,
It is checked whether there is a risk of camera shake at that shutter speed, that is, whether this shutter speed is smaller than a fixed value (for example, 1/f). If there is no risk of camera shake, proceed to step 79. If there is a risk of camera shake, proceed to step 82.
Then, a camera shake warning is issued using the viewfinder display 29, and the process proceeds to END processing. In other words, if there is a risk of camera shake, a warning is given and exposure is not performed. Note that if there is a risk of camera shake, only a warning may be given and exposure may be allowed.

In step 79, the lens driving circuit 23 is activated to move the focusing lens 15 to a position where the subject at the subject distance a is focused, and the process proceeds to step 80.

In step 80, on condition that the focusing lens 15 has moved to this in-focus position and the release button 26 is fully pressed, the aperture drive circuit 24 and the exposure circuit 25 are driven to adjust the aperture to the above aperture F value. The aperture is stopped down, the shutter is driven at a speed based on the exposure value, the subject image shown in FIG. 3 is exposed on film, and the process proceeds to END processing.

With the above operations, shooting of one frame is completed. Normally, when the above-mentioned exposure is completed and the process proceeds to END processing, the film is wound one frame by an autowind device, and at the same time, a mechanical charge such as a shutter is performed.

Then, in the END process, each condition is initialized on the condition that the release button 26 is returned to at least the half-pressed state, and the main routine can be interrupted again by the timer included.

As described above, according to the automatic focusing device of this embodiment, just by pressing the release button 26 once, focusing and exposure can be done taking into account the depth of field, just like in conventional shooting, so anyone can easily do it. Depth photography becomes possible.

In the above embodiment, there are three distance measurement zones, and each distance measurement zone is located on the horizontal line passing through the optical axis. It is.

Furthermore, if the distance measurement zone used for distance measurement can be selected by operating a switch, the types of subjects that can be photographed will increase, which will be very convenient.

Even if the subject you want to focus on is in the distance measurement zone in a certain composition, if it is not the desired composition, half-press the release button to perform a predetermined calculation and focus, then lock the focus and achieve the desired composition. After changing the exposure, you can press the release button all the way to expose.

If the distance difference between the distant view and the foreground is large, the depth of field may not include the distance. For such a case, a priority mode may be provided in which a distant view, a close view, or an intermediate view is preferentially included in the depth of field range.

Furthermore, this automatic focusing device can also be provided with a mode that focuses on a subject in one focusing zone selected by the user out of three focusing zones, or a mode that focuses on a subject in one ranging zone selected by the user, or a mode that focuses on a subject in one ranging zone selected by the user, or a mode that focuses on a subject in one ranging zone selected by the user. It is also possible to provide a mode for focusing on the subject.

``Effects of the Inventionj'' As is clear from the above explanation, according to the automatic focusing device of the camera of the present invention, depth of field photography can be performed with a desired composition by - number of release operations, so there is no need to change the composition. It is very easy to operate, and allows for easy depth-of-field photography of moving subjects.

0... Distance measuring means, 11... Distance measuring distance storage means, 2.
... Far and near distance determination means, 3. Depth of field calculation/control means, 4. Lens driving means, 15. Focal lens, O.
・・Main system (wholesale unit, 21...CCD2...
Photometry sensor, 23... Lens drive circuit, 4... Aperture drive circuit, 25... Exposure circuit, 6... Release button, 28... Lens ROM.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing the configuration of an embodiment of a camera to which the present invention is applied, and FIG. 3 shows the relationship between the finder field of view and the distance measurement zone. 4, 5 and 6 are operation flowcharts of this embodiment, and FIGS. 7(A) and 7(B) are diagrams showing the depth of field photographing operation in a conventional autofocus camera. FIG. Patent applicant: Asahi Optical Industry Co., Ltd. Agent: Kunio Miura Figure 1 Figure 2 Figure 4 Figure 3 Figure 5 Figure 6

Claims (1)

[Scope of Claims] A distance measuring means having a plurality of distance measuring zones and measuring a subject distance for each distance measuring zone; a subject distance storing means storing each of the subject distances measured by the distance measuring means; a lens driving means for driving a focusing lens of a photographing lens to a focus position; a distance determining means for determining a farthest distance and a nearest distance from a plurality of subject distances stored in the subject distance storage means; and a distance determining means for determining a farthest distance and a nearest distance. The aperture value and the in-focus subject distance are determined so that both the farthest distance and the closest subject determined by are included within the depth of field of the photographing lens, and the aperture is narrowed down to the above aperture value via an aperture driving means. An automatic focusing device for a camera, comprising: depth of field calculation/control means for moving the focusing lens to a position where the focus lens is brought into focus at the in-focus object distance via the lens driving means.