JPH02300730A - Auto-focus camera - Google Patents

Abstract

PURPOSE:To enable a user to select a picture where his intended part is focused from plural pictures by successively photographing objects from the closest object to the most distant object in plural range finding areas while shifting the focus. CONSTITUTION:Distance information to objects in plural range finding areas set in a photographic screen is detected by a detecting means 1, and information indicating the longest distance and information indicating the shortest distance are extracted from detected distance information of plural range finding areas. Based on information indicating intermediate distances of one or more positions newly determined by these two information, the focus of an objective lens 100 is shifted to photograph objects from the closest object to the most distant object by a photographing control means 3. Thus, the picture including his intended object is properly taken through this object is not in the range finding area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an autofocus camera having a plurality of ranging areas within a photographic screen.

[Prior Art] Conventionally, in an autofocus camera that has a plurality of distance measurement areas within the shooting screen, distance measurement information indicating the distance to the subject for each distance measurement area, that is, the absolute distance to the subject or Detects the amount of defocus that indicates the focus adjustment state of the objective lens, selects one that satisfies a predetermined condition from among these multiple distance measurement information, and moves the objective lens to the in-focus position based on the selected distance measurement information. It is driven to take pictures.

Here, the predetermined conditions for selecting one of the plural distance measurement information include, for example, information indicating the closest distance, information showing the highest contrast, and information located in the center.

[Problems to be Solved by the Invention] However, in conventional autofocus cameras that select one distance measurement information that satisfies a predetermined condition from among a plurality of distance measurement information, The subject with the highest contrast is not necessarily the subject intended by the photographer.

For example, considering the case of photographing a close-up of a person's face as shown in FIG.
, Z2. It is assumed that Z3 is set. in this case,
In the distance measurement areas Zl and Z3, distance measurement information indicating the distance to the subject's ear is obtained as shown in FIG. 8(b).
In step 2, distance measurement information representing the distance to the subject's nose is obtained. Normally, when taking close-up shots of people's faces, it is basic to focus on the subject's eyes, but in this case, no matter which distance measurement area you select, the focus will be on the nose or ears. There was a problem where only the photos that were available were taken.

The present invention has been made in view of such conventional problems, and provides an autofocus camera that can appropriately take a photo that includes the intended subject even if the intended subject is not within the distance measurement range. The purpose is to

[Means for Solving the Problems] First, the present invention includes a detection means for detecting distance information to a subject in a plurality of distance measurement areas set within a photographing screen, and an objective lens based on the detection distance information of the detection means. The object of the present invention is an autofocus camera having a lens driving means for driving the lens to the in-focus position.

In the present invention for such an autofocus camera, information indicating the farthest distance and information indicating the shortest distance are extracted from the distance information of the plurality of ranging areas detected by the detection means. and a photographing control means that sequentially drives the objective lens by a predetermined shift amount within the distance range of the two distance information and performs a photographing operation for each lens position. It is.

[Function] According to the autofocus camera of the present invention having such a configuration, the photographer takes pictures while shifting the focus from the nearest subject to the farthest subject. You can choose from multiple photos the one that focuses on what you want. For example, in the case shown in Figure 8, a new setting is made based on information representing the distance to the farthest subject's ear, and information representing the distance to the subject's nose, which is the closest distance. The objective lens is sequentially driven based on the information representing the intermediate distance of one or more locations, and images are taken at each lens position. You can select a photo that is in focus.

[Example] FIG. 1 is a block diagram showing the basic configuration of the present invention.

In FIG. 1, 100 is an objective lens, and 1 is a detection means, which detects distance measurement information regarding the distance to the subject in a plurality of distance measurement areas set within the photographic screen. 2 is a lens driving means for driving the objective lens 100; 3 is a photographing control means; information indicating the farthest distance among distance information in a plurality of distance measurement areas detected by the detection means 1;
closest = 5 - information indicating the distance, and driving the objective lens 100 to the focusing lens position of each subject based on information indicating the intermediate distance of one or more points newly determined by these two pieces of information,
A photographing operation is performed at each lens position.

In the following explanation, the shooting mode in which the shooting control means 3 performs shooting while shifting the focus from the nearest subject to the farthest subject is referred to as a bracketing mode or AFB (auto focus bracketing). I'll call you.

Next, details of the detection means 1 shown in FIG. 1 will be explained.

Normally, the distance measurement information used in autofocus cameras to express the distance to the subject includes the absolute distance to the subject or the amount of defocus as the amount of deviation between the current objective lens position and the in-focus position. .

First, the TTL phase difference detection method for determining the amount of defocus is used.
This will be explained using figures.

= 6 = In FIG. 2, the field mask 200 is located near the film surface, and the opening of the field mask 200 becomes the detection area. A light flux incident through a region 101 of the objective lens 100 passes through a field mask 200, a field lens 300, an aperture aperture 401, and a re-imaging lens 501, and forms an image on the image sensor array A. Similarly, the light flux incident through the area 1-02 of the objective lens is transmitted to the field mask 200.
, the field lens 300, the diaphragm aperture 402, and the re-imaging lens 502 to form an image on the image sensor array B.

The pair of subject images formed on these image sensor arrays A and B move away from each other in the so-called front focus state where the objective lens 1 forms a sharp image of the subject in front of the planned focal plane, and conversely, the pair of subject images formed on the image sensor arrays A and B move away from each other in the so-called front focus state where the objective lens 1 forms a sharp image of the subject in front of the planned focal plane. In the so-called post-focus state in which a sharp image of the object is formed, the image sensor array A approaches each other, and in the so-called focusing state in which a sharp image of the object is formed in the intended focal plane, the image sensor array A,
The subject images on B relatively match. Therefore, the pair of subject images are photoelectrically converted into electrical data by the image sensor arrays A and B, and these data are processed to determine the relative position of the pair of subject images, thereby defocusing the objective lens 100. You will know the amount.

Next, as a method for determining the defocus amount from the data of the pair of image sensor arrays A and H, a method proposed by the present applicant in Japanese Patent Application Laid-open Nos. 60-37513 and 1982-245123 will be explained.

Now, let a pair of data strings be a (1), a (2), ・
... a (n) and b (1), b (2), ... b (n
), first, a correlation calculation is performed while each data string is relatively shifted by a predetermined amount of data. Specifically, the correlation amount C(L) is calculated using the following formula.

C(L) = Σl a (i) −b (D I...
- (1) Formula % Formula % Here, L is an integer corresponding to the shift amount of the data string as described above, and the first term and the final class r may be changed depending on the shift amount. The value obtained by multiplying the shift amount that gives the minimum correlation amount among the correlation amounts C(L) obtained in this way by a coefficient determined by the pitch width of the photoelectric conversion elements of the optical system and image sensor array shown in FIG. This is the amount of defocus.

However, the correlation amount C(L) is a discrete value as shown in FIG. 3(a), and the minimum detectable unit is limited by the pitch width of the image sensor array. Therefore, the present applicant has disclosed in Japanese Patent Laid-Open No. 60-37513 a method in which the minimum value Cex is newly calculated by performing an interpolation operation from the discrete correlation 1c(L), and precise focus detection is performed.

This is a method of calculation using the correlation amount CO, which is the minimum value, and the correlation amounts C-1, C1 at the shift amounts on both sides, as shown in FIG. 3(b), and the shift amount Fm that gives the minimum value Cex.
and the defocus amount DF are derived from the following equation.

DF=KfXFm F m = L + D L / E DL- (C-1-CI)/2 Cex=CO-IDL l E=MAX (CI-CO, C-1-CO)
・(2) Formula % Formula % This means selecting the larger one of the equations, and Kf is a coefficient for converting the shift amount into the defocus amount.

It is necessary to judge whether the defocus amount DF obtained in this way truly indicates the in-focus point or whether it is due to fluctuations in the correlation amount due to noise etc. When the following conditions are met, the defocus amount DF is Assume that there is trust.

E>Esl, and Cex/E<Csj.

(Esj, Cst are certain predetermined values)... Equation (3) As a method of providing multiple distance measurement areas within the shooting screen using this phase difference detection method, the optical system excluding the objective lens and the Either a plurality of pairs of image sensors are provided, or a pair of image sensor arrays A and B are used as shown in FIG.
one block IAB.

Divided into 2AB, 3AB, IBB, 2BB, and 3BB, each corresponding pair of blocks IAB and IBB,
There is a method of calculating a plurality of detected amounts by calculating the defocus amount using data of 2AB and 28B, 3AB and 38B = 10 = data.

Next, the active method for determining the absolute distance based on the subject's weight will be briefly explained using FIG.

In FIG. 5, ①R is a light emitting diode, and PSD is a position detection element, which outputs a signal representing the position of the spot light incident on the light receiving surface.

Lenses L'l and L2 are located in front of the light emitting diode IR and the position detection element PSD, respectively.

The light emitted by the light emitting diode IR is turned into a spot light by the lens L1 and projected onto the subject.

For example, if the subject is DH in Figure 5,
The spot light is reflected by the subject DH, passes through the lens L2, and enters the position N1 of the position detection element PSD. On the other hand, if the subject is PT, which is farther away than DH, the spot light is reflected by the subject PT and enters the position N2 of the position detection element PSD. Therefore, by detecting the position where the reflected spot light from the subject is incident on the position detection element PSD, the absolute distance to the subject can be determined.

= 11- As a method of providing a plurality of ranging areas within the shooting screen using this active method, for example, a plurality of light emitting diodes are provided, and each light emitting diode emits a spotlight in a different direction. Each spot light is received by a plurality of position detection elements PSD.

Next, the operation of an embodiment to which the present invention is applied in an autofocus camera using the method of determining the amount of defocus of an objective lens shown in FIGS. 2 and 3 will be described with reference to the flowchart shown in FIG.

First, in step S1, the defocus amount for each of the plurality of distance measurement areas is determined by the method shown in equations (1), (2), and (3) above. Among the defocus amounts calculated in step S1, the closest one is hm in,
Let hmax indicate the farthest distance.

Next, in step S2, it is checked whether or not the bracketing mode is selected. If the bracketing mode is not selected, the process proceeds to step S3 to select, for example, the maximum defocus amount from among the plurality of defocus amounts obtained by the calculation in step S1. Select those that meet predetermined conditions, such as those that indicate proximity,
Step S4 based on the selected defocus amount
The objective lens is driven to the focusing lens position in step S5.
After the release is performed and the photograph is taken, the film is wound to the next frame in step S6, and the series of processing is completed.

On the other hand, if it is determined in step S2 that the bracketing mode is selected, the process proceeds to step S8, and it is determined whether there are a plurality of blocks or only one block for which a reliable defocus amount has been calculated.

The bracketing mode in the present invention cannot be performed unless there are two or more defocus amounts. Therefore, when only one defocus amount is obtained, in this embodiment, a warning is given in step S7 that bracketing photography is not possible, and the operation is ended. Of course, processing may be performed such as forcibly switching to a mode in which a single photograph is taken by driving the objective lens based on a single calculated defocus amount.

If it is determined in step S8 that a plurality of defocus amounts have been obtained, the process proceeds to step S9, where a lens shift amount S for bracketing photography is set.

Here, the shift amount S can be set by the photographer inputting an arbitrary value, or by automatically setting it based on the depth of focus achieved by the aperture value or maximum aperture value of the objective lens used at the time of shooting. Make it.

Next, the process proceeds to step 10, where a variable indicating the amount by which the objective lens is driven is set to the defocus amount hmin indicating the closest distance, and further, in step 811, a variable Th indicating the total amount of movement of the objective lens during bracketing photography is set. Initialize hmin. Then, in step S12, the objective lens is
After the camera is driven by mhmin and the camera is released and photographed in step S13, the film is wound to the next frame in step S14, and the photographing of the first frame is completed.

Next, the process proceeds to step S15, where the driving amount is set to hms in order to set the next objective lens driving amount to the shift amount S set in step S9, and in step S16, the total assembly amount Th
is updated to T h = T h + h. In other words, Th at this time indicates how much the total assembly movement of the objective lens will be when the objective lens is driven by h next time.

Subsequently, in step S17, it is determined whether Th>hmax, and Th is the defocus amount h indicating the farthest distance.
If it is determined that the value is smaller than max, the process returns to step S12, and operations such as lens driving, release, and winding are repeated. In step S17, T h > h m a
If it is determined that
If driven by =s, the total assembly amount will exceed hmax, and the objective lens will be driven further away than the value indicating the farthest distance among the defocus amounts calculated in step S1, so h = s Then, the process proceeds to step S18, where the driving amount is set to h=hmax-(Th 10 seconds) so that the total assembly movement of the objective lens will be 11 m ax the next time the objective lens is driven. Then, in step S19, the objective lens is driven by h, and in step S20, the camera is released and photographed, and then in step S21, the film is wound to the next frame, and the operation is completed.

In the embodiment described above, if the next time the lens is driven by the amount of shift S, the focus will be farther away than hmax, which indicates the farthest distance, the total amount of movement of the objective lens will be exactly hmax. The next lens drive is performed at
Or, if you set it based on the depth of focus determined by the aperture value at the time of shooting, hmax, which indicates the farthest distance by this lens drive, will be within the depth of focus, so hm
A photograph is taken in which the subject indicating the ax is also sufficiently focused. Therefore, when the shift amount S is set based on the depth of focus in this way, in step S17
> h max, bracketing photography can be ended, so the operations of steps 818 to S21 can be omitted.

Next, an embodiment in which the present invention is applied to an autofocus camera using the method of determining the absolute distance to the subject as outlined in FIG. 5 will be described with reference to the flowchart in FIG.

First, absolute distances of objects in a plurality of distance measurement areas are determined in step S1 using the method shown in FIG. Among the absolute distances calculated here, the closest one is dmin
, let dmax indicate the farthest distance. Next, in step S2, it is determined whether or not the bracketing mode is selected. If the bracketing mode is not selected, the process proceeds to step S3, and from among the plurality of absolute distances obtained by the calculation in step S1, for example, the nearest The objective lens is driven in step S4 based on the selected absolute distance, and the shutter is released in step S5 to take a picture, followed by step S6.
Wind the film to the next frame and end the series of processing.

On the other hand, when the bracketing mode is determined in step S2, the process proceeds to step S8, and it is determined whether there are a plurality of blocks or only one block for which a valid absolute distance has been calculated. Here, the absolute distance that is not effective is, for example, a distance where the subject is closer than the closest distance that can be photographed by the objective lens. The bracketing mode in the present invention cannot be performed unless there are two or more absolute distances.

Therefore, if only one absolute distance cannot be obtained in step S8, in this embodiment, the process proceeds to step S7, where a warning is given that bracketing photography is not possible, and the operation is ended. Of course, processing may be performed such as forcibly switching to a mode in which one photograph is taken by driving the objective lens based on only one calculated absolute distance.

If it is determined in step S8 that a plurality of absolute distances have been obtained, the process proceeds to step S9, where the distance dmin indicating the closest distance calculated in step S1 is set as the variable d indicating the position at which the objective lens is driven, and step S10 to drive the objective lens to the dmdmin position, and step Sl.
After the release is performed with l to take a picture, the film is wound up to the next frame in step S12.

Next, the process proceeds to step S13, where a lens shift amount e for bracketing photography is set. Here, the shift amount e can be set by the photographer by inputting an arbitrary value, or by automatically setting it based on the depth of field determined by the objective lens used during shooting or the open aperture value and subject distance. do it like this.

Next, the process proceeds to step S14, where e is added to d and this is newly set as d as the objective lens position for the next photographing.

In the next step S15, it is determined whether the value of d newly set in step S14 is greater than or equal to dmax. If it is determined that it is not greater than or equal to dmax, the process returns to step S10, and operations such as lens drive, release, and winding are performed. repeat.

When it is determined in step S15 that d>dmax, if the objective lens is driven by d next time, the objective lens will exceed dmax indicating the farthest distance, so the objective lens will move to the position d set in step S14. Stop driving the lens, proceed to step S16, set d=dmax so that the objective lens will be driven to the -19= position of dmax next time, drive the objective lens to the dmax position in step 817, After the film is released and photographed in step 818, the film is wound to the next frame in step S19, and the operation ends.

In the embodiment of FIG. 7 described above, the next step S
If the lens is driven to the position d set in step 14, the focus will be farther away than dmax, which indicates the farthest distance, then set dmax as the next objective lens drive position.
Although we have reset x, if we set the amount of shift e based on the depth of field determined by the open aperture of the objective lens or the aperture value at the time of shooting, dmax, which indicates the farthest distance from the subject, will be Since it is within the depth of field, d
A photograph is taken that is sufficiently in focus even for the subject that indicates max. Therefore, when the shift amount e is set based on the depth of field, in step S15, d>
As soon as it is determined that dmax is reached, it is okay to end bracketing shooting, so step 8
Operations 16 to S19 can be omitted.

Furthermore, when a subject whose absolute distance can be regarded as infinite, such as a distant mountain, enters the distance measurement area, dmax becomes infinite, and d does not exceed dmax in step 815, and steps S''10 to S15 are repeated. Therefore, for example, the depth of field is set to a distance d inf that allows a sufficiently focused photograph to be taken even for an object at infinity, and the distance d inf is set between steps S12 and 313. It may be determined whether the photographed distance d exceeds dif, and if it exceeds dif, the photographing may be terminated at that point.

Alternatively, at the stage of distance measurement, all distances greater than df may be set to df.

[Effects of the Invention] As described above, according to the present invention, the photographing operation can be performed sequentially while shifting the focus from the nearest subject to the farthest subject in a plurality of distance measurement areas. This allows the photographer to select from among multiple photos the one that focuses on the area he/she intended.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the basic configuration of the present invention; Fig. 2 is an explanatory diagram of the optical system used in the TTL phase difference detection method; Fig. 3 is a diagram for determining the amount of defocus in the TTL phase difference detection method. An explanatory diagram of the calculation method; Fig. 4 is an explanatory diagram showing an example of a method of providing multiple detection amounts in the TTL phase difference detection method; Fig. 5 is an explanatory diagram of the principle of the active method; Fig. 6 is an illustration of the present invention A flowchart showing the operation when the present invention is applied to an autofocus camera that detects the amount of defocus: Fig. 7 is a flowchart showing the operation when the invention is applied to an autofocus camera that detects absolute distance; Fig. 8 is an explanatory diagram of a photographing state showing a conventional problem. Explanation of symbols of main parts]: detection means 2, lens drive means 3/imaging control means Zl, Z2. Z3: Ranging area

Claims (1)

[Claims] (1) A detection means that detects distance information to the subject in multiple distance measurement areas set within the shooting screen, and a lens that drives the objective lens to the in-focus position based on the distance information detected by the detection means. In an autofocus camera having a driving means, information indicating the farthest distance and information indicating the shortest distance are extracted and set among distance information of a plurality of ranging areas detected by the detection means. and a photographing control means that sequentially drives the objective lens by a predetermined shift amount within a distance range between the closest distance and the farthest distance, and performs a photographing operation for each lens position. Autofocus camera.