JP2002244021A - Range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it is impossible to perform focusing by correctly measuring a subject distance in composition where a main subject, an image signal pattern and the image signal pattern of a background interfere in the same amplitude in the conventional range finder. SOLUTION: Sensor arrays 3 and 4 for performing the range-finding of a plurality of range-finding areas on a photographic image plane are arranged in this range finder, which is provided with switches 13 and 14 connected to an output side, and a selection part 15 for switching them. When an interference deciding part 18 decides that the range-finding of the main subject is not accurately performed because the image signal of the subject interferes, the selection part 15 is switched to perform range-finding again by finding out a part where the clear image signal of the main subject is easily obtained, and the clear image signal is obtained from the main subject.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring apparatus mounted on a camera and used for focusing a photographing lens by measuring the distance of a main subject.

[0002]

2. Description of the Related Art In general, there are two types of distance measuring methods of a distance measuring device mounted on a camera: a passive type which takes in an image signal of a subject and uses it; and an active type which uses reflected light of light projected from the camera side. The types are widely known.
In addition, the number of zoom lenses capable of performing zooming from near to the telephoto side is increasing, and there is a demand for correctly focusing a distant subject.

[0003] Originally, the passive type AF does not depend on the arrival distance of the projection light from a strobe device or the like, so that it can perform an appropriate distance measurement for a main subject located at a long distance. However, when the main subject exists at a long distance of 10 m or more, the image signal of the main subject tends to interfere with the image signal of the background rough subject, and accurate distance measurement may not be performed. Therefore, the present applicant has proposed a technique for solving such a problem in Japanese Patent Application Laid-Open No. 10-160456.

[0004]

However, the technique described in the above-mentioned publication discloses an image signal pattern of a main subject as shown in FIG. 4B and an image of a rough subject such as trees in the background. In the case where the signal patterns cause interference with the same amplitude, a sufficient effect could not be exhibited.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a distance measuring apparatus that can accurately measure a distance even when the contrast between a background and a main subject in a composition to be photographed has similar characteristics.

[0005]

In order to achieve the above object, the present invention detects a subject image signal on a photographing screen using a first sensor array pair and measures the distance to the subject. Provided is a distance measuring device that performs interference determination processing for finding the main subject when the subject image signal determines that the main subject and the coarse subject in the background are interfering.

[0006] The interference determination process suggests that a distance different from the point at which the determination is made be re-measured. The interference determination is performed when the result of the distance measurement by the first sensor array is longer than a predetermined distance. The interference determination is performed when the subject image signal from the first sensor array pair changes spatially at a predetermined cycle or more. Further, the interference determination is performed when there is a difference of a predetermined value or more between a distance measurement value of the first area of the first sensor array pair and a distance measurement value of a second area smaller than the first area. Perform

In the distance measuring apparatus having the above-described configuration, a first and a second sensor array for measuring a plurality of distance measuring areas on a photographing screen are arranged, and a switch connected to an output side; A selector is provided for switching between them. If the image signal of the subject is interfered by the interference determination unit and the main subject cannot be accurately measured, a portion where it is easy to obtain a clear image signal of the main subject by switching the selector is found. This is a distance measuring device that performs distance measurement again and obtains a clear image signal from the main subject.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, before describing the embodiment, the basic principle of passive AF will be described with reference to FIG. As shown in FIG. 2A, an image of the main subject (person) 5 is formed on the sensor arrays 3 and 4 via the pair of light receiving lenses 1 and 2. The sensor arrays 3 and 4 are composed of a plurality of pixels arranged at a predetermined pitch. These pixels generate an electric signal according to the brightness of incident light by photoelectric conversion, and thus the electric signal is A / D converted. Then, two digital image signals are obtained from each sensor array.

These image signal positions have a relative position difference of x shown in the figure according to the principle of triangulation. Assuming that the distance between the two lenses is B and the distance between the lens and the sensor array is f, the relative position difference x according to the subject distance L
Varies according to the relationship of x = (B · f) / L (1).
Therefore, the distance L can be obtained by obtaining the position difference x of this image.

In FIG. 2 (a), the two lenses and the sensor array are divided into upper and lower parts for easy understanding.
Actually, as shown in FIG. 3, it is often arranged on the front of the camera on the left and right, and as shown in FIG.
A horizontally long area 30 is monitored. By measuring the distance horizontally as described above, it is possible to focus even if the subject 5 exists at a position deviated from the center of the screen.

Further, if one is added one above and below the center of the sensor array, the arrangement becomes as shown in FIG. 2 (c). When applied to a camera, the monitor area of these sensor arrays is displayed on the screen 6 as shown in FIG.
, Three lines 30a, 30b, 30c are arranged in the horizontal direction.

FIG. 1 shows an example of a configuration in which a distance measuring apparatus of the present invention is mounted on a camera as a first embodiment, and FIG. 3 shows an external configuration of the camera. This camera 2
Reference numeral 0 denotes a front surface on which a photographing lens 7, a finder objective lens 24, and a strobe light emitting unit 8 are arranged. A pair of distance-measuring light-receiving lenses 1 and 2 are provided adjacent to the finder objective lens 24. On the top surface of the camera 20, a release button 6 and a display unit 9 such as an LCD for displaying the number of shot frames, the mode and the like are arranged.

As shown in FIG. 1, this camera is roughly divided into an arithmetic control unit (CP) comprising a one-chip microcomputer or the like.
U) 10 and an integrated circuit unit (AFIC) 12. The CPU 10 includes the release button 6, the strobe light emitting unit 8, and a focusing unit 23 that focuses the photographing lens 7. You. AFIC12,
Each of the sensor arrays 3 (3a, 3b, 3
c), 4 (4a, 4b, 4c), switches 13 and 14 connected to the output terminals of the respective sensor arrays, and a selector 15 for selecting which pixel output is to be obtained by operating these switches. It consists of.

The CPU 10 includes switches 13 and 14
An A / D converter 16 for converting an output taken out through the A / D converter into a digitized image signal, an image signal memory 17 for storing an image signal converted into a digital value, and interference based on the image signal. The image signal is read from the image signal memory 17 and the position of the image signal is compared by the sensor arrays 3 and 4 to determine the position of the image signal. , A distance calculator 21 that calculates a focusing distance based on the output result of the correlation calculator 19, and a focus position that calculates the focus position of the photographing lens 7 based on the calculated focusing distance. And a calculation unit 22.

The correlation calculator 19 compares the positions of the image signals output from the sensor arrays 3 and 4 with the CPU 10.
According to a predetermined program stored in a built-in RAM, the respective pixels of the sensor arrays 3 and 4 are compared to obtain an image shift amount x. Is obtained. The focusing unit 23 focuses the photographing lens 7 based on the focus position calculated by the focus position calculation unit 22. In general, the output of a pixel is a current signal, and therefore includes an integration operation unit that integrates the current signal and converts it into a voltage, and a monitor unit that monitors the integration amount and controls the integration amount to an optimal size. ,
It is not shown here.

Next, a description will be given of a distance measuring operation performed by the distance measuring apparatus thus configured.

In the photographing composition shown in FIG. 4A, a person 5 serving as a main subject is located at the center of the screen, and the scenery is located far behind the person 5. In such a composition, the person 5 has a contrast clearly different from that of the background, and the detected image signal is an image signal in which the person 5 and the background can be clearly distinguished as shown in FIG. A signal is obtained.

However, in the photographing composition shown in FIG. 4B, the person 5 as the main subject is located at the center of the screen, but the shadow of the tree is cast on the face of the person, and the branches and A rough subject such as a leaf is included. In such a composition,
Since the shadow of a tree is formed on the face of the person 5 and the branches and leaves have almost the same shadow as the contrast of the face of the person, as shown in FIG. It is a situation where it is not possible to know just where the person's face is and where the background image is from.

Therefore, in the present embodiment, when accurate distance measurement is not possible in the face portion of the person 5, a portion in which a clear image signal of the main subject can be easily obtained is measured again. For example, in a composition as shown in FIG.
If the image a is acquired, the contrast that hinders the distance measurement is eliminated, and the area occupied by the subject in the monitor area is large.
As shown in FIG. 5C, a clear image signal from the main subject can be obtained. If each line sensor measures the distance at three locations in the horizontal direction, it is possible to measure 9 points on the screen as shown in FIG. Here, for example, the left of each line is indicated as L, the center is indicated as C, and the right is indicated as R.

The distance measuring operation will be described with reference to the flowchart shown in FIG. First, three points L, C, and R shown in FIG. 6 are measured using a sensor array that monitors the line sensor 30b shown in FIG. 6 (step S1). This is because the selection unit 15 shown in FIG.
The A / D converter 16 converts the sensor data of
While performing D conversion, it is stored in the image signal memory 17. Then, the image signals of the two sensor arrays 3b and 4b corresponding to the read L, C and R are compared by the correlation operation unit 19,
From the relationship of the above-described equation (1), the distance L is calculated by the relative position difference x.
Is calculated.

Next, the closest distance (closest distance) is selected from the obtained distances as LP1 (step S1).
2) Subsequently, a predetermined distance L0 stored in advance is compared with this LP1 (step S3). As shown in FIG. 8, the image input to the sensor in the predetermined comparison area in the sensor array 3 monitors the image of the face of the person 5 up to the distance L0, but the person 5 exists at the farther distance L1. When an image is captured, an image of the background subject 5b is input from the side of the face, so that interference occurs in the image signal for distance measurement, and accurate distance measurement cannot be performed. This is because the relationship between the distance L and the relative position difference x according to the equation (1) is not established because images having different distances are used.

In this comparison, when the distance measurement result LP1 is longer than the predetermined distance L0 (YES), the selection unit is configured to use the image of the lower part of the part that outputs the closest distance among L, C, and R. 15 the sensor array 30b is replaced with the sensor array 30a. For example, when the R of the sensor array 30b is the closest distance, the R of the sensor array 30a is
Use the image of In the scene as shown in FIG.
Distance measurement is performed using the image signal of the body part of the person 5, and the obtained result is set as a distance LP2 (step S4). on the other hand,
If the distance measurement result LP1 is shorter than the predetermined distance L0, (N
O), the distance measurement result LP1 is set as the focusing distance LP (step S7), and the process returns.

Then, the calculated distances LP2 and LP1
Are compared (step S5). In this comparison, if the distance LP2 is shorter than the distance LP1 (YES), the closer distance LP2 is set as the focusing distance LP (step S6). However, if the distance LP1 is shorter than the distance LP2 (NO), the process shifts to step S7, where the closer distance L
Let P1 be the focusing distance LP. As described above, when the person 5 is the main subject, if the image is of the body part, an image having a wider width than the face (see FIG. 5C) is obtained. As is apparent from FIG. Since no image signal interference with the background rough subject 5b occurs, accurate distance measurement can be performed. As described above, according to the present embodiment, it is possible to provide a distance measuring apparatus which prevents interference with the background of the main subject image and enables accurate focusing even at a long distance.

Next, a distance measuring apparatus according to a second embodiment will be described. In the scene shown in FIG.
As shown in FIG. 9, the image signals of the main subject and the background of the rough subject interfere with each other, and the main subject image is buried in the same contrast. Therefore, in the present embodiment, it is considered that the area that outputs the closest distance among the respective distance measurement areas of the central sensor array hides the main subject, and the change in the image signal of the selected area is examined. .

The distance measuring operation will be described with reference to the flowcharts shown in FIGS. First, three points L, C, and R are measured using, for example, a sensor array that monitors the line sensor 30b (step S11).
Then, the distance L is calculated for each. Obtained distance L
Is selected (step S12).

Next, for example, when the area C in FIG. 9 is selected, the average value SAV of the sensor data (output data of each pixel of the image signal) of the area C is obtained (step S1).
3). It is checked how many times the sensor output of each pixel crosses the line of the average value SAV, and the number (variable) m of crossings is initialized (step S14). If the number m is large, it can be determined that the scene is a cluttered scene, and the probability of interference increases.

Then, the average value SAV and the first sensor output Sn of the area are compared from the end (step S1).
5). In this comparison, if Sn> SAV, (YE
S), 1 bit of memory (RAM) built in CPU 10
Is set to 1 (step S).
16). If Sn> SAV is not satisfied (NO), the storage flag F_C is set to 0 and reset (step S17).

Next, while incrementing n of Sn (step S18), the comparison with the average value SAV is repeated (step S19). In this comparison, Sn
If it is not> SAV (NO), it is determined that the data has changed by determining whether the storage flag F_C = 1 is set (step S20). Storage flag F_C =
If 1 is set (YES), the storage flag F_C
Is changed to 0 (step S21), and the number of crossings m is incremented (step S22). On the other hand, if Sn> SAV in the determination in step S19, (YE
S) The storage flag F_C indicates that the data has changed.
= 1 is determined (step S23). Here, if 1 is not set in the storage flag F_C (NO), 1 is set in the storage flag F_C (step S24).

However, if the storage flag F_C = 1 (YES), or after changing the storage flag, or if 1 has not been set in the storage flag F_C in step S20 (NO), the area It is determined whether the comparison in C has been completed (step S25). If it has not ended here (NO), the above-mentioned step S18
And repeat the comparison. On the other hand, if the processing has been completed (YES), it is determined whether or not the number of crossings m is greater than a predetermined number of times m0 (step S26). If the number of times of crossing m is greater than the predetermined number of times m0 (YES), the possibility of interference is high. Therefore, the distance measurement using the image signal of the lower part of the main subject is performed, and the obtained result is referred to as the distance LP2.
(Step S27). And the calculated distance LP
2 is compared with the distance LP1 (step S28). In this comparison, if the distance LP2 is shorter than the distance LP1 (YES), the closer distance LP2 is set to the focusing distance LP.
(Step S29). However, if the distance LP1 is shorter than the distance LP2 (NO), the closer distance LP1 is set as the focusing distance LP (step S30). When the main subject is a person in this manner, if the image is of a body part, an image having a wider width than the face (see FIG. 5C) is obtained, and the distance L1 is apparent as shown in FIG. However, since the image signal interference with the background rough subject 5b does not occur, accurate distance measurement can be performed.

As described above, according to the present embodiment,
Judgment as to whether the image signal has changed spatially at a predetermined cycle or more is based on the number of times the sensor data average value within the predetermined area exceeds or does not exceed. did. In this case, it can be determined that accurate distance measurement of the main object becomes difficult due to the influence of the background.
Therefore, at this time, since the distance measurement is performed using another part of the main subject, it is possible to perform photographing with accurate focus.

Next, a third embodiment of the present invention will be described. In the present embodiment, when the distance is measured in the area E1 of the sensor array 3 as shown in FIG.
Although the image of the rough subject 5b in the background other than that is mixed into the image signal for distance measurement, the influence of the background is reduced when the distance is measured in the area E2 smaller than the area E1, and the influence on the image signal is reduced. This is an example in which interference of a background image is determined.

Referring to the flowchart shown in FIG.
The distance measuring operation will be described. First, a distance LP1 is calculated by detecting a distance in a wide ranging area (wide area) E1 (step S31). Next, the predetermined distance L0 is compared with the distance LP1 (step S32). As described with reference to FIGS. 7 and 8 in this comparison, the distance LP1 is equal to the distance L0.
If the distance is farther (YES), it is determined that there is a possibility that the image is affected by a background subject, and the distance is measured using an area (narrow area) E2 smaller than the wide area E1, and the distance is measured. LP2 is obtained (step S33). However, when the distance LP1 is shorter than the distance L0 (NO),
Return without interference determination.

Next, the distance LP1 and the distance LP2 are compared (step S34), and if the distance LP1 is farther (Y
ES), interference determination is performed (step S35). However, if the distance LP1 is shorter than the distance LP2 (NO), the routine returns.

Next, a fourth embodiment according to the present invention will be described. The distance measuring operation will be described with reference to the flowchart shown in FIG. First, the distance Lc is determined by measuring the distance at the center of the screen to be photographed (step S41). In this central portion, it is determined whether or not to perform the interference determination according to the above-described first to third embodiments (step S4).
2). If it is determined that there is interference (YES), the distance of an area other than the center of the screen is measured (step S43). The closest distance (closest distance) LP1 from the distances L obtained in this area is adopted (step S45), and the process returns. If it is determined in step S42 that there is no interference (NO), the distance Lc obtained from the center of the screen is adopted (step S44), and the process returns. According to the present embodiment, in the scene as shown in FIG. 15, even if it is difficult to focus on the subject at the center of the screen, proper focusing can be performed by measuring the distance of the subject on the right.

According to each of the above-described embodiments, even if the background and the main subject have image signals that change in the same manner, the distance to the subject can be accurately determined. Also, when mounted on a camera, even when aiming at a long-distance person with a long focal length zoom lens, it is possible to take a photo that accurately focuses on the main subject without being disturbed by the background rough subject. You can enjoy.

Although the above embodiments have been described, the present invention includes the following inventions. (1) In a distance measuring apparatus that detects a subject image using the first sensor array pair and measures the distance to the subject, if the subject image signal causes interference between a main subject and a background rough subject. When the determination is made, the apparatus further comprises a determination switching means for performing a distance measurement using a signal of a second sensor array provided at a position different from the first sensor array to realize an interference determination process. Distance measuring device. (2) The ranging apparatus according to the above (1), wherein the interference determination is performed when the result of the distance measurement by the first sensor array is longer than a predetermined distance. (3) The distance measuring apparatus according to (1), wherein the interference determination is performed when an image signal from the first sensor array spatially changes at a predetermined cycle or more.

(4) In the interference determination, the distance measured by the first area of the first sensor array and the distance measured by the second area smaller than the first area have a difference of a predetermined value or more. The distance measuring apparatus according to the above mode (1), wherein the determination is sometimes made. (5) The distance measuring apparatus according to the above (1), wherein the second sensor array monitors a lower part of the subject from a monitor area of the first sensor array.

[0038]

As described above in detail, according to the present invention, even when the contrast between the background and the main subject in the composition to be photographed has the same characteristics, a distance measuring apparatus capable of accurate distance measuring is provided. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a block configuration of a distance measuring device mounted on a camera according to a first embodiment.

FIG. 2 is a diagram for describing a basic principle of passive AF.

FIG. 3 is a diagram illustrating an external configuration of a camera according to the first embodiment.

FIG. 4 is a diagram illustrating an example of a shooting composition.

5 is a diagram showing characteristics of a sensor output when a distance is measured in an area in the center of the screen in the composition shown in FIG. 4;

FIG. 6 is a diagram illustrating an example of an arrangement of distance measurement points arranged on a shooting screen.

FIG. 7 is a diagram illustrating a flowchart for describing a distance measuring operation in the first embodiment.

FIG. 8 is a diagram for describing a background based on a positional relationship between a main subject and a sensor.

FIG. 9 is a diagram illustrating characteristics of a sensor output for describing a distance measuring apparatus according to a second embodiment.

FIG. 10 is a flowchart illustrating a distance measuring operation according to the second embodiment.

FIG. 11 is a flowchart illustrating a distance measuring operation according to the third embodiment.

FIG. 12 is a diagram illustrating an example of a shooting composition according to a third embodiment.

FIG. 13 is a diagram illustrating a flowchart for describing a distance measuring operation in the third embodiment.

FIG. 14 is a diagram illustrating a flowchart for describing a distance measuring operation in the fourth embodiment.

FIG. 15 is an example of a scene for explaining a distance measurement operation in the fourth embodiment.

[Explanation of symbols]

1, 2 ... light receiving lens for distance measurement 3, 3a, 3b, 3c, 4, 4a, 4b, 4c ... sensor array 5 ... main subject (person) 6 ... release button 7 ... photographing lens 8 ... strobe light emitting unit 9 ... display Unit 10: Operation control unit (CPU) 12: Integrated circuit unit (AFIC) 13, 14 Switch 15: Selection unit 16: A / D conversion unit 17: Image signal memory 18: Interference determination unit 19: Correlation operation unit 20: Camera 21: distance calculation unit 22: focus position calculation unit 23: focus adjustment unit 24: finder objective lens

Claims (5)

[Claims] 1. A distance measuring apparatus for detecting a subject image signal on a photographing screen using a first sensor array pair and measuring a distance to a subject, wherein the subject image signal is used for a main subject and a background. A distance measuring apparatus for performing interference determination processing for finding the main subject when it is determined that there is interference with a certain rough subject. 2. The distance measuring apparatus according to claim 1, wherein the interference determination processing indicates that a distance different from a point at which the determination is performed is performed again. 3. The distance measuring apparatus according to claim 2, wherein the interference determination is performed when a result of the distance measurement by the first sensor array is longer than a predetermined distance. 4. The measurement according to claim 2, wherein the interference determination is performed when the subject image signal by the first sensor array pair changes spatially at a predetermined cycle or more. Distance device. 5. In the interference determination, a difference between a distance measured by a first area of the first sensor array pair and a distance measured by a second area smaller than the first area is greater than a predetermined value. 3. The distance measuring apparatus according to claim 2, wherein said determination is made at a time.