JP2620235B2 - Signal forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal forming apparatus for forming a signal for focus adjustment of a still video camera, a video camera, and the like.

(Prior Art) A disadvantage of the conventional one-point distance measuring type autofocus device that measures the distance only at one point on a screen, that is, “a scene in which two people are lined up or a scene in which the people are biased to the edge, The main subject (mainly a person) deviates from the distance measurement area in the screen, so the main subject is not in focus and the subject is in focus at infinity. " A so-called wide-field (multi-point) ranging method for measuring the distance has been proposed.

Examples of an auto-focusing device conventionally known as such a wide-field distance measurement include: (1) a method of focusing on the closest distance measurement result among a plurality of distance measurement results (for example, GENERAL & MECHANICAL 4582424, JP-A-61-88211
(2) If a plurality of distance measurement results are within the depth of field determined by the focal length of the projection lens and the aperture, focus on the average value, and A method in which all the objects corresponding to the distance measuring points are focused (Japanese Patent Application Laid-Open No. Sho 61-8821)
No. 1, JP-A-61-55619, JP-A-61-53614) (3) Judgment as to whether it is outdoors or outdoors based on luminance information. If outdoors, focus on the furthest object from multiple ranging results. For example, there is a method of focusing on the nearest one in the door (JP-A-61-55619, JP-A-61-53614).

(Problems to be Solved by the Invention) However, in the above-described method (1), a scene in which two persons are lined up or a scene in which a person is biased to the edge is used.
In many cases, the person (main subject) is in focus,
For example, when there is an obstacle ahead or when there is a foreground, it is difficult to cause a problem that these obstacles are focused and a person (main subject) is not focused.

In the method of the above (2), when all of the plurality of distance measurement results fall within the depth of field in the first place, it is rare except when using a short focus lens or when shooting under high brightness shooting conditions. In addition, when using a long focal length lens or shooting under a low luminance condition, there is little possibility that the effect of camera shake will appear on the image or that any of a plurality of distance measurement results will be out of focus.

Further, in the above-mentioned method (3), there is a difficulty in that a person (main subject) is not focused, such as a front obstacle being focused in a door.

As described above, in the autofocusing apparatus of the wide-field distance measuring method according to the conventional proposal, in many cases, a person (main subject) is a scene in which two persons are arranged or a scene in which the persons are shifted to the edge. Although it is possible to obtain the feature that the focus will be focused on the main subject, on the other hand, the main subject will not be focused in the scene that was focused by the conventional one-point distance measurement method (the foreground will be focused) It is difficult to bring another problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a signal forming apparatus that forms a signal for causing a desired object to be focused at a high rate without requiring a complicated operation. Things.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for receiving signals from a plurality of objects scattered in a viewing direction to thereby generate signals related to respective distances of the plurality of objects. A light receiving unit for forming; a determining unit for determining whether an object around the visual field is closer than a predetermined distance; and the determining unit determining that an object around the visual field is closer than a predetermined distance. Signal forming means for forming a signal for focus adjustment by a signal from the light receiving means so as to eliminate a signal related to the distance of the object around the visual field which is closer than the predetermined distance. This is a signal forming device.

(Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

Embodiment 1 FIG. 1 is a diagram showing a principle of distance measurement of an active system applicable to the present invention, and this system utilizes a triangulation method used for a lens shutter camera or the like.

In FIG. 1, the output light of the light projecting element 22 is converged by the light projecting lens 21 and applied to the subject 25 as a thin beam.
The spot light reflected by the light receiving lens 23 forms a real image on the surface of the light receiving element 24 by the light receiving lens 23. The deviation d from the center position of the spot light shown in FIG.
And d increases as the distance decreases, and this relationship is expressed as f / L = d / S (where f is the focal length of the light receiving lens 23, S
Is the baseline length).

The number of points on the screen that are measured in the wide-field ranging method is determined by the application of the camera using the autofocus device,
Although it is appropriately determined according to the cost and the like, the following embodiment will be described by taking as an example a case where distance measurement is performed on three points in the screen shown in FIG. 3 for convenience.

FIG. 2 is a block diagram showing the configuration of the automatic focusing apparatus according to the first embodiment of the present invention. In FIG. 2, 1a, 1b, and 1c are shown.
Denotes a block of a light projecting element and a light projecting lens for performing distance measurement corresponding to three points in the screen, and the light emission control circuit 2 controls light emission. Reference numeral 3 denotes a block of a light receiving element and a light receiving lens, and an output terminal from the light receiving element is
It is connected to a distance measuring circuit 4 for calculating the distance to the subject. Reference numeral 5 denotes an interface circuit having an A / D conversion function, which connects between a microprocessor unit (hereinafter referred to as MPU) 6 and various circuits. Reference numeral 7 denotes a drive circuit for moving the taking lens unit 8 to a focus position based on a control signal from the MPU.

The operation of the automatic focusing apparatus in the present example configured as described above is performed by first turning on a main switch (not shown).
A light emission start signal is supplied from the MPU 6 to the light emission control circuit 2 via the interface circuit 5. Accordingly, the light emission control circuit 2 sequentially turns on the light emitting elements 1a, 1b, and 1c at timings given by various constants preset in the circuit. The output light from the light projecting element is reflected by the subject to form a real image on the surface of the light receiving element 3, and the output from the light receiving element 3 receiving the reflected light is input to the distance measuring circuit 4 in FIG. The distance to the subject corresponding to each of the indicated distance measurement points is sequentially calculated.

The distance measurement information calculated by the distance measurement circuit 4 is read into the MPU 6 via the interface circuit 5 in synchronization with the lighting timing of the light projecting element, and the MPU 6 calculates the focal position as described below. The photographing lens unit 8 is moved to a predetermined position by the drive circuit 7 based on the result.

The feature of the automatic focusing apparatus of the first embodiment having the above-described configuration and operation is that the photographing lens unit 8 is moved based on the information (distance measurement value) of the distance measurement result for the above three points from the distance measurement rotation 4. The operation procedure of the MPU 6 for calculating, calculating and outputting the control signal is performed in accordance with the flowchart shown in FIG.

 Hereinafter, the procedure will be described in detail.

The operation procedure of the MPU 6 of the present example is roughly composed of the following three stages. That is, the first is a step of detecting the closest point LN, the farthest point LF, and the intermediate point LM based on the distance measurement information (hereinafter referred to as a first step). Second, by comparing these LN, LM, and LF with each other or by comparing with other conditions, the focal position required for the scene to be currently photographed is different from the focal position required for another scene. This is a step of determining the situation and separating the corresponding scene from other scenes (hereinafter referred to as a second step). Third
Is a step (hereinafter referred to as a third step) of calculating a focal position suitable for each of the scenes divided as described above by using a predetermined calculating means.

First, the first stage will be described. In this stage, the nearest point LN, the farthest point LF, and the intermediate point are read by the MPU 6 which has read the distance measurement information of three points in the screen input from the distance measurement circuit 4.
LM is required.

Next, the second stage described above will be described. In this stage in the present example, the cases are divided into five cases, and the order of priority is determined first by the intermediate point LM and the nearest point LN.
And the difference (ie | LN−LM |)
A comparison is made with a constant k corresponding to the depth of field determined by the focal length of the photographing lens, the open F value, and the like, and whether the distance measurement result for the nearest point LN is valid or invalid (hereinafter referred to as determination (a)). Case classification is performed. Here, “invalid” means that the data is unnecessary for the detection of the focal position (the same applies hereinafter).

In the above, when the closest point LN is regarded as valid and invalid, the following determination is performed respectively.

That is, for the former (when the nearest point is valid), the difference between the farthest point LF and the intermediate point LM (that is, | LF−LM |) is obtained, and this difference is calculated as the focal length of the photographic lens and the open F value. Is compared with a constant k corresponding to the depth of field determined by the formula (1), and a case is determined by determining whether the distance measurement result for the farthest point LF is valid or invalid (hereinafter referred to as determination (b)). As a result of these determinations, the nearest point LN and the farthest point with respect to the intermediate point LM
When all LFs are effective, it can be said that these three distance measurement values are substantially at similar distances.

In the present example, when the farthest point LF is valid (that is, | LM−LF | ≦ k), it is further determined whether or not the farthest point LF is at the minimum distance (hereinafter, determination (C)). Is performed).

Performing this determination (c) is one of the features of the present embodiment. In other words, ignoring the result of ranging at infinity in this way is that there is almost no possibility that this person is at infinity when the main subject is a person, and 1 if the main subject is not a person. Considering that it is unlikely that only the point will be at infinity, ignoring one of the infinity distance measurement results will prevent the focus from being drawn to the background and becoming sweet. .

Further, in the active type automatic focusing device as in the present embodiment, the projected spot light cannot form a real image on the light receiving element surface due to the influence of the shape reflectance of the subject, and is actually effective. There is a case where a distance measurement result equivalent to infinity is obtained even though there is a subject at a distance. Therefore, in order to remove such unreliable data, it is effective to ignore one of the distance measurement results at infinity.

If the farthest point is not at infinity, the focal position is calculated using the above three points.

On the other hand, when the latter, that is, the difference between the nearest point LN and the intermediate point LM, that is, | LN−LM |, is larger than the constant k (| LN−NM | ≧ k), The determination (hereinafter referred to as determinations (d) and (e)) is performed by determining whether or not the above condition is satisfied. This determination is one of the features of the present embodiment, and it is used to determine whether the distance measurement information at the closest point is the main subject or an obstacle.

The conditions used as references in the above determinations (d) and (e) are the following conditions: The possibility that the nearest point LN is an obstacle estimated from shooting conditions such as the focal length and luminance information of the shooting lens. The distance is longer than the high distance r (for example, about 1 m for a 38 mm lens).

Condition The distance measurement point of the closest point LN is the center.

According to the determinations (d) and (e), the case where at least one of these conditions is satisfied and the case where neither is satisfied are distinguished.
In the latter case (when none of the conditions are satisfied), the case is further determined by determining whether the distance measurement result for the farthest point LF is valid or invalid (hereinafter referred to as determination (f)).

Therefore, when | LN−LM | ≧ k as described above, three cases are eventually performed.

Next, an operation performed in the next stage (third stage) in accordance with the above case classification will be described.

When the difference (| LN−LM |) between the nearest point LN and the intermediate point LM is smaller than the constant k (| L
When (N−LM | ≦ k) is detected and selected, it is as described above that the distance measurement result for the closest point LN is considered to be valid information, and in this case, it is further determined ( b)
And (c), the two scenes are classified, and these scenes are classified into the following two modes a and b.
Appropriate ones are selected from the calculation methods b and the focus position is calculated.

I. (When | LM−LF | ≧ k) or (When the farthest point LF is at infinity) The focal position is calculated from the average value of LM and LN.

B. (If | LM−LF | ≦ k and the farthest point LF is not at infinity according to the determination (c)) The focal position is calculated by averaging three points.

On the other hand, in the above, if the difference (| LN−LM |) between the closest point LN and the intermediate point LM is larger than the constant k (| LN−LM | ≧ k), the determination (a) is detected and selected. In the case described above, the distance measurement result for the closest point LN is regarded as invalid information as described above. In this case, three scenes for which different focus positions are to be determined according to the determinations (d) and (e) are further divided into cases, and the following three modes C, D, and E which are adapted to the three scenes are respectively applied. Is selected and the focal position is calculated.

C. (When at least one of the above conditions is satisfied) The focal position is calculated from LN.

D. (Either of the above conditions is not satisfied and | LM−L
When F | ≧ k) The focal position is calculated from LM.

E. (Either of the above conditions is not satisfied and | LM−L
F | ≦ k) The focal position is calculated from the average value of LM and LF.

In the above embodiment, the results of the determinations (a) to (c), which are the features of the above-described embodiment, are selected as the arithmetic operations to which one of the operation modes (a) and (b) is suitable. You.

That is, in the case of A, | LN−LM | ≦ k and | LM−LF | ≦
It can be said that so-called three points satisfying the condition of k are located at similar (approximate) distances. Even in such a scene, for example, when the farthest point is at infinity, a simple scene is used. When the focal position is calculated based on the average value of the three points, there is a problem that the focal position is pulled backward as described above. Therefore, in the automatic focusing apparatus of the present example, in such a case, the point at infinity is not distance measurement information indicating the main subject, or the reliability of the information at infinity is not always high. It can be said that this is a method in which the focal position is regarded as a scene to be calculated from the average of the point LN and the intermediate point LM.

Embodiment 2 In addition to the case shown in FIG. 1, the distance measuring device used in the present invention may be based on the principle shown in FIG.

The principle of this distance measuring method is that of a passive method called SST, and the distance measuring operation is basically based on a double matching method.

That is, distance data is to be obtained by checking the positional correlation between two images obtained by the two optical systems.

FIG. 5 schematically shows the principle, in which 25 is an object to be measured. The light receiving lens 26 and the mirrors 28 and 29 aim the subject 25 on the optical axis a thereof, and are called a reference side optical system. On the other hand, the light receiving lens 27 and the mirrors 30 and 31 are arranged at a reference length S from the reference side optical system, and are referred to as a reference side optical system.

In the above configuration, the image of the subject 25 captured by the light receiving lenses 26 and 27 is formed on the image sensor 32, the image based on the reference optical system is on the reference visual field A, and the image based on the reference optical system is Are formed on the reference visual field B, respectively.

Here, assuming that the subject 25 is at infinity, the subject 25 is positioned on the axis of each of the reference-side and reference-side optical systems.
Since the images are located on a and b, the subject images by the respective optical systems are formed as IMB on the reference visual field A and IMR1 on the reference visual field B, respectively. On the other hand, when the subject 25 approaches the axis a of the reference side optical system, the optical path from the subject 25 to the reference optical system is inclined. For this reason, the image of the subject 25 by the reference-side optical system shifts on the reference-side visual field B like IMR2. Therefore, by detecting at which position on the reference visual field B the same image as the image IMB on the reference visual field A is formed, it is possible to know the distance to the subject.

FIG. 6 is a block diagram of an automatic focusing device according to a second embodiment of the present invention using the side distance device.

In this figure, reference numerals 9a, 9b, and 9c denote side-distance devices each including a lens, a mirror, and an image sensor; 10a, 10b, and 10c denote side-distance circuits that calculate a distance from the output of the image sensor; and 11, an interface circuit.

In this example, the MPU 6 also reads the results of three side distances via the interface circuit 11 in the same manner as in the first embodiment, and calculates the focal position in accordance with the flowchart of FIG. 4 described in the first embodiment.

The control output to the drive circuit 7 for controlling the taking lens unit 8 is given based on the above calculation result.

Embodiment 3 FIG. 7 is a diagram showing an optical arrangement of an automatic focusing apparatus according to Embodiment 3 of the present invention. In FIG. 7, reference numeral 41 denotes a lens element, and 42 denotes a lens element for recombining an image on a pupil plane. , Generally consisting of 20 or more lenses. Reference numerals 43 to 46 denote pixels of a light receiving element such as a CCD (charge coupled device) element. Pixels 43 and 44 for the small lens 42a, and pixels 45 and 4 for the small lens 42b.
6 corresponds. Pixel 43 is apertured through small lens 42a
The pixel 44 faces the aperture 47 through the small lens 42a. Similarly, pixel 45 is a small lens 42b
Through the aperture 48, the pixel 46 is a small lens 42
It faces the aperture 47 part through b.

Here, assuming that the small lens 42a is the nth small lens and the 42b is the (n-1) th small lens, a pixel facing the aperture 48 through the nth lens is An, a pixel Bn facing the aperture 47,
Pixels facing aperture 48 through the (n-1) th lens
The pixel facing the An-1 and the aperture 47 is Bn-1. The F plane corresponds to the focal plane of the lens 41. Therefore lens 41
By changing the position in the left-right direction on the screen, the subject distance for correctly forming an image on the F-plane differs. When the image of the object at the focal distance is taken as the output of the sensor, An = Bn,
While An-1 = Bn-1, when capturing an image of an object not at the focal distance, An = Bm (n ≠ m).

FIG. 8 is a block diagram showing an automatic focusing apparatus according to a third embodiment of the present invention. In this figure, 12 is a sensor unit composed of the small lens group and the light receiving element array described in FIG. 7, 13 is an A / D converter, and 14 is an output of the A / D converter 13.
Gates 15, 16, and 17 for distributing to one memory are memories and 18 interface circuits.

In the above configuration, the A / D of the signal obtained from the sensor unit 12 is converted into a digital signal by the converter 13, and the pixels are distributed to three memories by the gate 14. As a result, the three points can be distanced, and the contents of these three memories are read by the MPU 6, and the focus position is set in the same manner as in the first and second embodiments according to the flowchart described in FIG. The driving circuit 7 drives and controls the lens unit 8 based on the calculated value.

It is needless to say that the present invention is not limited to the above embodiments, but can be realized in various modified embodiments. For example, the discriminating means for other cases to be combined with the discriminations (a) to (c), and the calculating means prepared to be adapted when each case is divided are not limited to those of the above embodiment. Known technical means can be appropriately selected and adopted according to the performance required for a camera or the like to be designed.

As described above, the number of distance measurement points in the screen may be three or more. When the number of distance measurement points is four or more, the determination of the intermediate point, the farthest point, and the nearest point is performed, for example, by using the distance measurement point. In the case of the four points shown in FIG. 9, the average value of the distance measurement results with the two central points or the distance measurement result on the near side of the two points is determined as the distance measurement result of the central part. The intermediate point, the farthest point, and the nearest point may be determined from the three distance measurement results of the peripheral part and the central part.

If the number of ranging points is 5 as shown in Fig. 10,
As in the four points in the figure, the average value of the distance measurement results of the three central points or the closest distance measurement result of the three points is used as the distance measurement result of the central part, and the left and right peripheral parts and the central part are measured. The intermediate point, the farthest point, and the nearest point may be determined from the three distance measurement results, the closest one of the five distance measurement results is the nearest point, the third one is the intermediate point, and the fifth one. May be set as the farthest point.

<Correspondence between Invention and Embodiment> In the above embodiment, the light receiving element 3, the distance measuring circuit 4 or the light receiving elements 9a to 9c, the distance measuring circuits 10a to 10c or the sensor unit,
The A / D converter corresponds to the light receiving means of the present invention, the first and second steps of the MPU 6 correspond to the determining means of the present invention, and the third step of the MPU 6 corresponds to the signal forming means of the present invention. I do.

(Effect of the Invention) As described above, according to the present invention, there is provided a signal forming apparatus for forming a signal for causing a desired object to be focused at a high rate without requiring a complicated operation. be able to.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining the principle of distance measurement used in an automatic focusing apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram schematically showing the configuration of the automatic focusing apparatus according to the first embodiment. 3
FIG. 4 is a diagram showing an example of a light projecting device used in the first embodiment. FIG. 4 is a flowchart for explaining a procedure for focus detection performed in the microcomputer of the first embodiment. FIG. 6 is a diagram for explaining the principle of distance measurement used in the automatic focusing apparatus, FIG. 6 is a block diagram showing a schematic configuration of the automatic focusing apparatus according to the second embodiment, and FIG. 7 is used in the automatic focusing apparatus according to the third embodiment. Diagram explaining the principle of ranging,
FIG. 8 is a block diagram showing a schematic configuration of the automatic focusing apparatus according to the third embodiment. FIG. 9 and FIG. 10 are diagrams for explaining the case where the number of distance measuring points on the screen is four and five. 1a, 1b, 1c: light emitting element, 2: light emission control circuit 3: light receiving element, 4: distance measuring circuit 5, interface circuit 6: microprocessor unit (MPU) 7: drive circuit, 8: photographing lens unit 9a , 9b, 9c: light receiving element, 10a, 10b, 10c: distance measuring circuit 11: interface circuit 12, sensor unit, 13: A / D converter 14: gate, 15, 16, 17: memory 18: interface circuit 21: Projection lens, 22: Projection element 23: Light reception lens, 24: Light reception element 25: Subject, 26: Projection lens 27: Light reception lens, 28, 29: Mirror 30, 31: Mirror, 32: Image sensor 41: Lens Element, 42: Small lens group 42a, 42b: Small lens, 43, 44, 45, 46: Pixel 47, 48: Aperture

Claims (1)

(57) [Claims] 1. A light receiving means for receiving light from a plurality of objects scattered in a direction of a visual field to form a signal related to a distance of each of the plurality of objects, and an object around a visual field being located at a predetermined distance. Determining means for determining whether or not the distance is closer, and determining whether or not the object around the visual field is closer than a predetermined distance. Signal forming means for forming a signal for focus adjustment based on a signal from the light receiving means so as to eliminate a signal related to the distance of the object.