JPH02118610A - Focus limiter for automatic focusing camera - Google Patents

Abstract

PURPOSE:To arbitrarily set the focus distance range of an automatic focusing device by executing a focusing action within a far-and-near limit distance by means of the automatic focusing device, and preventing it from executing the focusing action exceeding the range of the far-and-near limit distance. CONSTITUTION:A deciding means 12 compares a far-and-near limit distance outputted from a far-and-near limit distance storing means 11 with a distance-measured distance outputted from a distance measuring means 10, whether the distance-measured distance is included within the range of the far-and-near limit distance is decided, and a decided signal is outputted to a focus control means 13. The focus control means 13 receives the distance-measured distance from the distance measuring means 10 and the decided signal outputted from the deciding means 12, and when the decided signal is 'including', a lens driving means 14 is activated, and the focusing action to move a focusing lens 15 to the position focused to the distance-measured distance is executed. When the decided signal is 'not including', the focusing action is not completely executed or the focusing action is executed until it reaches the far-and-near limit distance. Thus, with an easy operation and, moreover, regardless of a photographing lens, a subject distance range, in which the automatic focusing device is operated, can be set.

Description

TECHNICAL FIELD The present invention relates to an autofocus camera, and more specifically to a focus limiter that can arbitrarily set the focusing distance range of an autofocus device.

"Prior art and its problems" Conventional autofocus - The autofocus device of an eye-reflex camera divides the subject ray that is incident on the photographic lens into two within the distance measurement zone, and are guided to the distance measurement sensor (COD), and based on the two-split subject image signal output from the distance measurement sensor, a predetermined focus calculation is performed in the focus control section to obtain a day focus value. In this method, the AF mode was driven based on the AF mode, and the focusing lens was moved to the in-focus position to focus.

The autofocus device is activated by pressing the release button halfway, and in servo AF, while the release button is pressed halfway, distance measurement and focusing operations of the focusing lens continue at predetermined time intervals.

When photographing with the above-mentioned conventional autofocus camera, if a desired subject leaves the distance measurement zone, the camera will focus on a new object captured by the distance measurement zone. In particular, when photographing a moving object, it is often the case that the desired moving object cannot be tracked and the object is sometimes removed from the distance measurement zone.

When a desired moving object leaves the distance measurement zone and a new object that enters the distance measurement zone is at infinity or a short distance, the focusing lens moves to an infinity or short distance focusing position. Therefore, even if a moving object is captured again in the distance measurement zone, it will take a long time for the focusing lens to move to a position where the moving object is brought into focus. When photographing a moving object, the shutter opportunity is often instantaneous, so if it takes a long time to focus on the moving object, there is a great possibility that the shutter opportunity will be missed.

``Object of the Invention'' The present invention was made based on the above-mentioned problems of the conventional autofocus camera, and it is possible to set the subject distance range in which the autofocus device operates with simple operation and regardless of the shooting lens. , an object of the present invention is to provide a focus limiter for an autofocus camera.

"Summary of the Invention" The present invention includes a distance measuring means for measuring a subject distance, a lens driving means for driving a focusing lens of a photographing lens, and a lens driving means for driving a subject distance based on the subject distance measured by the distance measuring means. a focusing control means for driving the focusing lens to a position where it focuses on the subject; a limit distance storage means for storing near and far limit distances of a subject distance range in which the focusing lens performs focusing; and a distance measuring means. and determining means for determining whether the subject distance measured by the distance measuring means is included in the distance limit distance range stored in the limit distance storage means, and the focusing control means is configured to determine whether the subject distance measured by the distance measuring means When the determining means determines that the subject distance is within the distance limit distance, the focusing lens is operated via the lens driving means, and when it is determined that the subject distance is not within the distance limit distance, the lens driving means is activated. or the lens driving means is operated until the focusing lens reaches the distance limit distance.

According to the focus limiter having the above configuration, the automatic focusing device performs a focusing operation within the distance limit distance, and does not perform a focusing operation beyond the distance limit distance. Moreover, since the focus limiter of the present invention detects the distance limit distance without using mechanical or electrical contact means, it does not require mechanical locking means to restrict the movement (focusing operation) range of the focusing lens, or There is no need to provide an electrical contact means on the photographic lens, and the present invention can be applied to conventional autofocus lenses as is.

“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.

The distance measuring means 10 that measures the distance to the subject includes a distance limit storage means 11 that stores distance limit distances;
Determining means 12 for determining whether the current subject distance output from distance measuring means 10 is included within the distance limit distance stored in limit distance storage means 11 and focusing control means 13 are connected. . Further, a determining means 12 is connected to the limit distance storing means 11.
2 is connected to a focusing control means 13.

The focus control means 13 is connected to a lens drive circuit 14 that drives the focus lens 15 of the photographic lens in the focusing direction.

The object distance signal measured by the distance measuring means 10 is output to the limit distance storing means 11 when storing the limit distance, and is output to the determining means 12 and the focusing control means 13 when photographing.

The limit distance storage means 11 has a function of storing two distance limit distances (subject distances), a long distance limit and a short distance limit, which are the limit object distances at which the focusing lens 15 moves and focuses, and the stored distance limits. It has a function of outputting the distance to the determining means 12 at the time of photographing.

The determining means 12 compares the distance limit distance outputted from the distance limit distance storage means 11 and the measured distance outputted from the distance measuring means 10, and determines whether the measured distance is within the range of the distance limit distance. A determination signal indicating whether or not it is included is output to the focusing control means 13.

The focus control means 13 receives the measured distance from the distance measuring means 10 and the judgment signal output from the judgment means 12, and if the judgment signal is "included", starts the lens driving means 14 (in operation). If the determination signal is "not included", the focusing operation is performed to move the focusing lens 15 to the position where the focus lens 15 is focused on the measured distance, and if the determination signal is "not included", the above focusing operation is not performed at all, or Focusing continues until the distance limit is reached.

Next, an embodiment in which the present focus limiter is mounted on a single-lens reflex camera will be described with reference to the block diagram shown in FIG.

The main control unit 20 has a distance measurement calculation function for the distance measurement means 10, functions as the determination means 12 and focus control means 13, and system control and calculation functions for the entire camera.

The main control unit 20 is connected to a CCD 21 as a sensor section of the distance measuring means 10 and a photometric sensor 22 for measuring subject brightness as sensors.

The main control unit 20 further includes a limit distance storage section 23 as a distance limit distance storage section 11 and a lens drive section 1 for driving the focal lens 15 of the photographing lens 25.
A lens drive circuit 24 as 4 is functioning.

As is well known, there is a photographing lens 25 on the light receiving surface of the C0D21.
The image of the subject in the distance measurement zone 30 formed by is divided into two parts and guided respectively.

The CCD 21 outputs an image signal corresponding to the two-part image of the subject, and the image signal is input to the main control unit 20.

The main control unit 20 calculates the object distance from the day focus value and the lens position using a known correlation method. This object distance is stored in the limit distance storage section 23 when the limit distance is set. During normal photographing operation, the focusing lens 15 is driven to the in-focus position via the lens drive circuit 24 based on the subject distance.

When photographing with the focus limiter in operation, the subject distance is compared with the distance limit distance stored in the limit distance storage section 23, and it is determined whether it is within the range of the distance limit distance. If it is determined that the object is within the range, a focusing operation is performed in the same manner as the normal photographing operation, and if it is determined that the object is not within the range, no focusing operation is performed.

Furthermore, a release switch 26 and a limit distance setting switch 27 are connected to the main control unit 20 as switches.

As is well known, the release switch 26 is a two-stage switch.
Press halfway to turn on the range finder switch SWS, press fully to keep the range finder switch on and turn on the release switch S.
WR turns on.

The limit distance setting switch 27 is a switch for setting the focus limit distance. When turned on, the main control unit 20 enters the limit distance setting operation, and when the release switch 26 is pressed halfway, the first limit distance (subject distance) is memorized. Furthermore, the second limit distance is memorized on the condition that the release switch 26 is turned off once and then turned on.

Reference numeral 28 denotes a display in the finder, which not only displays information related to exposure such as shutter speed, but also displays whether or not the camera is in focus, and whether or not the measured distance is within the distance limit distance.

The main control unit 20 is a microcomputer, and in addition to realizing the various functions described above based on programs stored in the ROM, it also executes AE calculations based on the subject brightness signal output from the photometric sensor 22, and controls the shutter speed. It has calculation and control functions for the entire camera, such as speed and aperture setting and control drive functions.

Next, regarding the operation and operation of this embodiment having the above configuration, referring to FIG.
A case will be described in which a person 33 who is active with a person is photographed.

The photographer first turns on the limit distance setting switch 27 to enter the limit distance setting mode.

First, point the camera at the tree 31 and set the distance measurement zone 30.
Put the tree 31 in and press the release button release switch 26.
Press halfway. Then, the main control unit 20, CC
The D21 and the lens drive circuit 24 are activated to start ranging and focusing operations, and the tree 31 is brought into focus. Tree 31 at this time of focus
The distance to is stored in the limit distance storage section 23 as a limit distance.

When focusing is completed, the photographer releases his finger from the release switch 26, points the camera at the rock 32, and aligns the distance measurement zone 30 with the rock 32. Then, press the release switch 26.

Then, as above, the main m unit 20 and the CCD 2
1 and the lens drive circuit 24 are activated, ranging and focusing operations for 32 are started, and the rock 32 is brought into focus. The distance L2 to the rock 32 at this time of focus is stored in the limit distance storage section 23 as a limit distance.

With the above operations, the limit distance setting operation is completed. After that, this camera focuses only on the subject between the tree 31 and the rock 32, and focuses on the subject closer than the tree 31 and the rock 32.
Focusing will not be performed on subjects further away than . Therefore, even if the distance measurement zone 30 moves away from the subject while the photographer is following the person 33, the camera will not focus on a subject closer than the tree 31 or farther than the rock 32. When the person 33 is captured in the distance measurement zone 30 again, the distance measurement zone 30 can be brought into focus in a short time.

Next, the operation of the main control unit 20 will be explained in more detail based on the flowcharts of FIGS. 4 to 6.

When the main control unit 20 is turned on, the main control unit 20 repeatedly checks the 0N10FF status of the release button 26 (distance measurement switch SWS) and the limit distance setting switch 27 at high speed until the distance measurement switch SWS or the limit distance setting switch 27 is turned on. wait until Distance switch S
When the WS is turned on, the process proceeds to the photographing process of the mode set in the mode setting process (step 41).

If the distance measuring switch SWS is off and the limit distance setting switch 27 is on, the process proceeds to the limit distance setting routine, and if it is off, the process proceeds to the END process (step 42).

Therefore, when the photographer turns on the power and turns on the limit distance setting switch 27, the main control unit 20 starts up the limit distance setting software.

When the main control unit 20 enters this limit distance setting mode, it checks whether the release button 26 is pressed halfway and the distance measurement switch SWS is turned on, and if the distance measurement switch SWS is not turned on, it waits until the distance measurement switch SWS is turned on. This check is repeated and waits (step 51). Note that even if the photographer accidentally presses the release button 27 all the way (even if the release switch SWR is turned on), the exposure process does not proceed.

The photographer points the camera at a distant (or near) subject, aligns the distance measurement zone 30 with the subject, and presses the release button 26 halfway.

Then, the distance measuring switch SWS is turned on, so the main control unit 20 activates the CCD 21 to perform a distance measuring operation, activates the lens drive circuit 24 based on the distance, and moves the focusing lens 15 in the direction of the in-focus position. (steps 52 and 53). Then, this distance measurement and lens driving operation is repeated until the object is focused on the condition that the distance measurement switch SWS is turned on (steps 51 to 54).

Once in focus, the main control unit 20 stores the current distance L1 as a limit distance in the limit distance storage section 23 (step 55), and waits for the photometry switch SWS to be turned off.

Because the lens drive circuit 24 has stopped, the photographer can
Alternatively, the user knows that the first distance measurement operation has been completed by lighting up the focus display on the finder display 28. The photographer then takes his finger off the release button 26 and turns the camera into a close-up (
or distant view), capture the subject in the distance measurement zone 30, and then press the release button 26 halfway.

The main control unit 20 detects that the distance measuring switch SWS has been turned on after being turned off, in step 56.5.
7) As above, the CCD 21 is activated to start the distance measuring operation.Step 58) The lens drive circuit 24 is activated based on the distance L2, and the focusing lens 15 is moved in the direction of the in-focus position.

Then, the distance measuring operation and lens driving operation described above are repeated until focus is achieved, provided that the distance measuring switch SWS is turned on (steps 57 to 60).

When the focus is focused, the main control unit 20 stores the distance L2 at the time of focus in the limit distance storage section 23 as the limit distance (step 61), and exits from the limit distance setting routine on the condition that the distance measurement switch SWS is turned off. (Step 62).

Then, the process returns to the switch check process at the predetermined time intervals.

The photographer performs the limit distance setting operation using the lens drive circuit 2.
4 has stopped, or when the in-focus display 28 in the viewfinder turns on, the user releases the release button 26.

The above operations and actions complete the limit distance setting.

Next, a description will be given of the photographing operation and operation in which the limit distance is set and the focus limiter is activated.

The photographer points the camera at the desired composition and selects the distance measurement zone 30.
align it with the desired subject and press the release button 26 halfway.

When the release button 26 is pressed halfway, the distance measurement switch SW
Since S is turned on, the main control unit 20 is C0D2.
1 to start the ranging operation (steps 71 and 72).
). Then, the distance measurement distance obtained in the distance measurement operation, the limit distance L1 stored in the limit distance storage section 23,
Compare each with L2 to determine the distance measurement distance or limit distance L.
1, check whether it falls within the range of L2 (steps 73 and 74).

If it is within the above range, the lens drive circuit 24 is activated to drive the focusing lens 15 in the direction of focusing at the distance measurement distance (step 75), and the release switch SWR controls this distance measurement and lens drive operation. Off, ranging switch SWS
Repeat until focus is achieved with the condition that is turned on (
Steps 71-76).

The photographer presses the release button 26 halfway and moves the camera according to the movement of the subject, but if the subject moves quickly or an obstacle gets between the subject and the photographer, the distance measurement zone 30 may be There are cases where the camera deviates from the subject and captures a subject at an infinite distance or a subject at close range. In this case, if the measured distance is not within the range of the limit distances L+ and L2, the main control unit 20
Only the distance measurement operation is repeated without performing lens drive processing (steps 71 to 74) 6. When the photographer captures the subject in the distance measurement zone 30, the main control unit 20 executes the lens drive processing, so that the camera is aligned with the subject. I feel anxious. In this way, when the distance measurement zone 30 is outside the distance measurement distance of the captured object or the limit distance, L, the focusing lens 15 is not driven.
The movement range of the focusing lens 15 is narrow, and even if the subject is captured in and out of the distance measurement zone 30, the time required for focusing when captured is shortened.

When the photographer fully presses the lens drive circuit 24, the release S is released.
Since the WR is turned on and the main control unit 20 drives the shutter, diaphragm, etc., the film is exposed (step 77).

After exposure, step 78) repeats the distance measurement and focusing operations described above if the continuous release is being used, and step 78) if the distance measurement switch SWS is turned off if the continuous release is not the continuous release.
Proceed to process D (step 79). Note that the continuous release here refers to a release mode in which exposure processing is repeated while the release SWR is on.

As is clear from the above description, according to the focus limiter of the present embodiment, when photographing a subject moving within a certain distance range, if a limit distance is set, the focusing lens 15 will move beyond the limit distance. Since the focus lens 15 does not move, the amount of movement of the focusing lens 15 during the focusing operation is small, and the focusing time is shortened.

Additionally, since the limit distance can be set using software, unlike mechanical limiters that restrict the rotation of the distance ring using a stopper, there is no need to take measures against impact caused by a collision with the stopper member or overload on the focusing lens drive source. . Moreover, since no mechanical configuration is required, conventional interchangeable lenses for autofocus cameras can be used as is.

In the above embodiment, the lens drive operation is not performed when the measured distance exceeds the set limit distance range, but the lens drive operation may be performed up to the limit distance.

Although the distance measuring and focusing operations of the autofocus device are used to set the limit distance, other means may be used to set the limit distance. For example, the configuration may be such that manual focus adjustment is performed, the distance ring of the photographic lens is rotated, and the distance at that time is stored in the limit distance storage section 23 by pressing a setting button at a position where the limiter is desired to operate. In this case, the distance to be memorized uses a distance signal output from the photographic lens in conjunction with the distance ring.

A configuration may also be adopted in which a data pack is provided separately, a desired limit distance is input using a key, and the key-input distance is stored in the limit distance storage section 23.

Further, in the limit distance setting means, one limit distance may be input and the other limit distance may be set to infinity or the shortest photographing distance of the photographing lens depending on the selection.

"Effects of the Invention" As is clear from the above description, according to the focus limiter of the camera of the present invention, the automatic focusing device performs focusing within the distance limit distance, and focuses beyond the distance limit distance. does not focus, so when photographing a subject that moves within a certain range, if you set the movement range as the distance limit distance, the focusing lens will not move beyond the limit distance, so you can focus on the desired subject. can be brought into focus in an extremely short time.

Moreover, the focus limiter of the present invention does not rely on mechanical or electrical contact means to detect the far and near limit distances. There is no need to provide a target contact means on the photographic lens (therefore, it can be applied as is to conventional autofocus lenses.

[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. The diagrams showing the relationships, FIG. 4, FIG. 5, and FIG. 6 are operational flowcharts of this embodiment. DESCRIPTION OF SYMBOLS 10... Distance measurement means, 11... Limit distance storage means, 12... Judgment means 13... Focus control means, 14... Lens driving means 15... Focusing lens, 20... Main control unit (judgment means, focus control means), 21... CCD (distance measuring means), 23... Limit distance storage section, 24... Lens drive circuit (lens drive means) 26...
・Release button, 27...Limit distance setting switch. Patent applicant: Asahi Optical Industry Co., Ltd. Agent: Kunio Miura Figure 3

Claims (5)

[Claims] (1) a distance measuring means for measuring a subject distance; a lens driving means for driving a focusing lens of a photographing lens; and a distance measuring means for driving a focusing lens of a photographing lens; a focusing control means for driving the object to a position where the object is in focus; a limit distance storage means for storing a far and near limit distance of an object distance range in which the focusing lens performs a focusing operation; and determining means for determining whether or not the subject distance measured by the distance measuring means is within the range of distance limit distances stored in the limit storage means; When the determining means determines that the range is within the range of A focus limiter for an automatic focusing camera, characterized in that the driving means is operated until the focusing lens reaches the distance limit distance. (2) A focus limiter for an autofocus camera according to claim 1, wherein the distance limit distance is set based on a subject distance measured by a distance measuring means. (3) A focus limiter for an autofocus camera according to claim 1, wherein the distance limit distance is set by a distance signal input from a distance ring of a photographing lens. (4) The focus limiter for an autofocus camera according to claim 1, wherein the distance limit distance is set by a distance input from a data back by key operation. (5) The focus limiter of an autofocus camera according to any one of claims 2 to 4, wherein one of the distance limit distances is set to infinity or the shortest photographing distance of the photographing lens.