JPS60233610A - Range finding device - Google Patents

Abstract

PURPOSE:To obtain range finding information matching with a main subject by providing a center weighting means for weighting range finding information on the periphery of the center part of a photographic image plane more than on other parts. CONSTITUTION:A projection lens 2 is formed of three lenses with different optical axes in one body and signal light emitted by an infrared-light emitting element 1 is split and projected on three different places, i.e. the center and peripheral parts of the photographic image plane and all reflected light beams are incident on a photodetecting element 4. The photodetecting element 4 uses a semiconductor position detector and detects the incidence position of reflected light which changes with subject distance to find the range. Then, this semiconductor position detector varies in the rate of outputs of both terminals according to the photodetection position of the incident light and the ratio of the outputs is detected to calculate the subject range. For the purpose, a circuit A is connected as a concrete processing circuit to the photodetecting element 4. Therefore, the range finding information on the subject is obtained without prefocusing operation, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a distance measuring device capable of measuring JJ distances at multiple locations within a screen.

Conventionally, so-called distance measuring devices that detect information corresponding to the distance to the subject in order to automatically perform focus detection, especially when the camera is busy, have performed the above detection only for subjects near the center of the shooting screen. . Therefore, in the case of a composition where the subject is placed at the edge of the shooting screen, first place the subject within the distance measurement mark set in the center of the shooting screen, measure the distance of the subject only, and then move the subject. It was necessary to perform a so-called prefocus operation, in which the camera was placed at the edge of the photographic screen and photographed.

However, this operation is difficult for beginners.

Also, today, as the performance of automatic focus detection devices has improved, most of the out-of-focus photos are caused by forgetting to prefocus or
This also occurs due to an incorrect operation.

In Japanese Patent Application No. 58-145068, the present applicant proposed that the above-mentioned pre-processing method would be implemented by projecting spot light toward various positions on the photographic screen and detecting a plurality of subject distances from the reflected light. 7 We are proposing an automatic focus detection device that does not require an orcus.

However, the method proposed in Japanese Patent Application No. 58-145068 simply averages the plurality of detected subject distances and assumes that the subject is at that distance, and matches the focus position of the photographing lens. This method has the drawback that the subject intended by the photographer and the subject not intended for the photograph are treated in the same way, and although the overall focus is in focus, it is not possible to obtain a sufficiently satisfactory focus on the main subject intended by the photographer.

The present invention has been made in view of the above circumstances, and includes a distance measuring device capable of measuring distances at multiple points within a screen, in which distance measurement information near the center of the screen is compared to distance measurement information in other parts. By providing a center focusing means for heavy handling, if the main subject is placed in the center of the screen, it will be able to focus on the main subject as well as conventional automatic focus detection devices, and the main subject will be in the center of the screen. We would like to provide a distance measuring device with excellent functionality and operability that does not require operations such as placing the main subject within the distance measuring mark provided in the center of the screen to measure the distance even when the main subject is at the edge. That is.

FIG. 1 is a schematic configuration diagram of a distance measuring device according to the present invention, in which 1 is an infrared light emitting element as a light projecting element, and 2 is a light projector for projecting the luminous flux of the infrared light emitting element 1 toward a subject. The projection lens as an optical system projects the projection light emitted from the infrared light emitting element 1 toward three points on the photographic screen by adjusting the optical axis so that three projection light beams exit in different directions. Three different lenses are integrally formed. 3 is a light-receiving lens as a light-receiving optical system for guiding the reflected light of the projected light beam projected onto the object surface to the light-receiving element 4, which is made up of three lenses with different optical axes, similar to the light-emitting lens 2, integrated together. The three projection light beams formed and projected onto the object surface are all formed to enter the light receiving element 4.

Here, the angle formed by the three optical axes of the light projecting lens 20 and the angle formed by the three optical axes of the light receiving lens 3 are the same from a three-dimensional perspective. That is, by moving the three optical axes of the light projecting lens 20 in parallel, it is possible to overlap the three optical axes of the light receiving lens 40.

In this embodiment, the light receiving element 4 is a semiconductor device detector (PSD).
The distance to the object is detected based on the incident position of the signal light, which is the reflected light of the projected light flux that enters the light receiving element 4. As a processing circuit for actual distance measurement, the one disclosed in, for example, Japanese Patent Application Laid-Open No. 54-44809 can be used as is, so its explanation will be omitted here.

In the present invention, three projection light beams are projected, but if each projection light beam hits a subject at the same distance, the reflected light will be incident on the same position of the light receiving element 4, and the distance from the incident position to the subject will be It can be detected. When the projected light beam hits objects at different distances, the reflected light enters the light receiving element 2 at different positions, but in that case, the weighted average position of the amount of incident light at those incident positions is detected as the object distance. It looks like this.

By the way, if only one of the three points on the above shooting screen is measuring the subject, and the other two points are measuring the background of the subject (in reality, this is almost always the case). In the past, the detected object distance was affected by the background and was much further away than the original object distance. For this reason, when such a distance measuring device is used as an automatic focus detection device of a camera, there is an inconvenience that it becomes impossible to obtain a photograph in which the subject originally intended by the photographer is in focus.

So, this photographer is busy thinking about the subject he intends to photograph, and when taking a picture, he generally places the subject in the center of the screen.
80% of the time, the subject is placed in the center of the screen. Therefore, if you can obtain distance information that allows you to always properly focus on the object at the center of the shooting screen among the three points that are measured from the shooting screen, you will be satisfied with high-low shots. Become something.

Figure 2 shows how the distance to the subject is set to 1.
The degree of blurring when the background is gradually moved away from the focal length f = 38 WII 11 aperture F number F2
．． A graph calculated for No. 8 photographic lens is shown.

The intensity of the reflected light is approximately inversely proportional to the square of the distance.
Proportional to reflectance. In FIG. 2, the vertical axis represents the diameter of the circle of confusion of the subject image, and the horizontal axis represents the distance to the background. In the figure, ■ is a graph when the light intensity ratio of the reflected light reflected by the subject and the reflected light reflected by the background for the same distance is set as 1 = 4.
is a graph when the same light amount ratio is set to 1:2, ■ is a graph when the same light amount ratio is set to 1:1, ■ is a graph when the same light amount ratio is set to 221, ■ is a graph when the same light amount ratio is set to 221, and ■ is a graph when the same light amount ratio is set to 1:1. This is the diameter of the circle of confusion of the subject when the background is in focus, which occurs in the detection device.

Generally, the allowable circle of confusion diameter for 35w1 camera is 0.03 to 0.
．． 0.035, but considering general photographing conditions etc., the diameter of the circle of confusion can be tolerated up to about 0.05. In addition, considering the difference in reflectance between the background and the subject, the intensity ratio of the reflected light corresponding to the center of the screen and the reflected light at the other two locations at the same distance and the same reflectance is the center °C reflected light ≧ the other two locations It is necessary that the reflected light be .

In other words, when measuring the distance between the center of the screen and two other points, it is an essential condition that the amount of reflected light as distance measurement information for each point other than the center of the screen must be less than half of the amount of reflected light at the center of the screen. It's coming.

On the other hand, in order for distance measurement information other than the center of the screen to have the effect of being distance information, a certain amount of reflected light from areas other than the center of the screen is required, so this will be discussed.

Considering the case where two people are photographed side by side, which is a common occurrence when conventional automatic focus detection devices fail, the projected light beam at the center of the screen will hit the background, and the projected light beams from two other places will hit the original subject. I can imagine it. In this state, in conventional automatic focus detection devices that measure the distance from the center, the diameter of the circle of confusion as shown in the graph (2) in Figure 2 often results in out-of-focus photographs. In three-point distance measurement, if this can be improved to some extent, it can be said to be effective, but even if the diameter of the circle of confusion changes from 0.3 to 0.2, it is still out of focus. For general outdoor photography, the F number is F5 in most cases.
Since the diameter of the circle of confusion is considered to be narrowed down to about 6 or less, the diameter of the circle of confusion is also less than half, and it can be determined that the effect is effective up to about ■ in Fig. 2. In other words, it can be said that it is effective to make the intensity of reflected light at each point other than the center of the screen about 178 times higher than the intensity of reflected light at the center of the screen. The first means for changing the intensity of reflected light at the center of the screen and the intensity of reflected light at other parts, that is, center-weighted means, is
In the figure, all you have to do is change the area of the lens part with the optical axis aimed at approximately the center of the shooting screen of the projection lens 2 and the area of the lens part with other optical axes, and basically the reflection is proportional to the area. Light intensity changes. The same can be said of the light receiving lens 3.

The ratio of the total amount of signal light is the product of the area ratio of the light emitting lens and the area ratio of the light receiving lens.

As shown in Fig. 3, a specific method for making the light emitting lens or light receiving lens in the first device is to cut out a part of each lens from three lenses 5, 6, and 7 of the same performance and connect them. In combination, a composite lens 8 having three optical axes a, b, and c may be obtained.

FIG. 4 shows another embodiment of the present invention, in which a mirror is used to divide the projected light beam into three directions.

In the figure, 9 is an infrared light emitting element similar to that in FIG. 1, and 10 is a projection lens having only one optical axis.

Reference numeral 11 and 12 refer to a reflecting mirror that reflects the projected light flux from the infrared light emitting element 9 to form a projected light spot image c on the object surface P. Note that a is a projected light spot image formed by a projected light beam directly projected from the infrared light emitting element 9 without passing through the reflecting mirrors 11 and 12. 13 is a light receiving lens which, like the light projecting lens 10, has only one optical axis.

14 is a light receiving element similar to that shown in FIG. A spot image a on the object surface P is directly transmitted to the light receiving element 1 by the light receiving lens 13.
The projected light spot image on the object surface P passes through the light-receiving lens 13, is reflected by the mirror 15, and is imaged on the light-receiving element 14. Further, the projected light spot image C on the object surface P similarly passes through the light receiving lens 13 and is reflected by the mirror 1'6, and is imaged on the light receiving element 14.

In this case, the intensity of each projected spot image (contribution rate to distance measurement) can be adjusted by the effective area of the lens and the size of the reflective surface of the mirror, and the light emission distribution of the infrared light emitting element 9 and the Each area may be set in consideration of reflectance and the like so that the reflected light amount ratio falls within the above range.

By the way, in order to minimize the influence of extraneous light on the membrane, it is necessary to pay attention to the distribution of the transmission light amount ratio between the light projecting system and the light receiving system.

Now, if the energy per unit solid angle of the light source is constant, E1
Pc is the solid angle covered by the part of the light emitting lens that has an optical axis aimed at approximately the center of the screen, Ps is the solid angle covered by each of the other parts with optical axes, and similarly, the optical axis is aimed at approximately the center of the 6 sides of the light receiving lens. If the solid angle from the object of the part with the optical axis is Re, the solid angle covered by each of the other parts with the optical axis is R8, and the external light intensity on the subject surface is N, then the amount of reflected light incident on the light receiving element 8p is Sp = (Pc - assistant P8・R, s・2)・S (reflectance of subject 1) External light amount Np is Np= (Rc+Rs -2) -N
The total ratio of reflected light amount to external light amount is 8 p/Np.

Also, if the ratio of the amount of projected light aimed at approximately the center of the screen and the amount of projected light aimed at other parts is X, then x=Pc-Rc/
(Ps-Rs) It is sufficient to select the light amount ratio around the center 1 of light emission and light reception that maximizes Sp/Np when X is constant. The result is Pc/Ps: , /';i, Rc/Rs =
It's the last time. In other words, the ratio of the amount of reflected light between the central part on the subject plane and other parts is set to T:1, and when the subject plane has uniform brightness, the light-receiving lens has an optical axis almost at the center of the screen. The ratio of the amount of light passing through the lens to the amount of light passing through the light-receiving lens portion having the other optical axis is mema:1.

In this embodiment, in order to measure distances at multiple points, the light emitting and receiving lenses have multiple optical axes, or mirrors are used, but this can also be done by using a prism or the like. good. In this case, the ratio of the amount of reflected light can be selected by adjusting the area or reflectance of the reflecting surface.

Furthermore, it goes without saying that the present invention is applicable not only to the case where the projected light beam is projected to three points on the photographic screen, but also to any number of distance measurement points as required.

As explained above, according to the present invention, in a distance measuring device that measures distances at multiple locations, even when the object lx is located only at the center, compared to conventional distance measuring devices that measure distance only at the center. Almost the same performance can be obtained, and on the other hand, even when there is no subject in the center of the screen, good focus adjustment can be obtained for the subject, which is the biggest drawback of conventional automatic focus detection devices that measure distance only in the center of the screen. It is possible to solve this problem and also prevent the occurrence of new problems caused by obtaining distance measurement information from a plurality of locations on the screen, making it extremely effective as a distance measurement device.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an embodiment of the distance measuring device according to the present invention, Fig. 2 is a graph showing the relationship between the subject and the background with respect to blurring of focus, and Fig. 3 is the projection and light receiving lenses of Fig. 1. FIG. 4 is a schematic diagram showing another embodiment of the distance measuring device according to the present invention. 1.9... Infrared light emitting element, 2.10... Light projection lens,
(, 3, 13... Light-receiving lens, 4.14... Light-receiving element, 11.12.15.16... Reflection mirror. 67 Procedural amendment (voluntary) May 1985 14th Japan Patent Office Commissioner Manabu Shiga 1981 Patent Application No. 90323 2 Name of the invention Camera distance measuring device 3 Relationship to the person making the amendment Case Patent applicant address 3-30 Shimomaruko, Ota-ku, Tokyo 2 names (100
)Representative of Canon Co., Ltd. Ryu Kaku Part 4, Agent address: 3-30-25 Shimomaruko, Ota-ku, Tokyo 146, Specification subject to amendment and drawing 6, Contents of amendment (1) Full text of the specification on MI paper Correct as shown below. (2) Figures 1 to 4 will be corrected as shown in the attached sheet. Amended Description 1, Name of the Invention Camera Distance Measuring Device 2, Claims In a distance measuring device that measures distances at multiple locations on a photographic screen, distance measurement information near the center of the photographic screen is transferred to other parts. A distance measuring device for a camera, characterized in that it is provided with a center-weighted means for handling distance measuring information more seriously. 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an improvement of a distance measuring device for a camera that can measure distances at multiple locations on a photographic screen. (Conventional Wave*> In conventional cameras, the so-called distance measuring device that detects information corresponding to the distance to the subject to automatically perform focus detection only measures objects near the center of the shooting screen. Therefore, when composing a photograph with a subject at the edge of the photographic screen, first place the subject within the distance measurement mark set in the center of the viewfinder, and only measure the distance to the subject. It was necessary to perform a so-called pre-focus operation, which involves holding the distance measurement information, repositioning the subject at the edge of the viewfinder, and then proceeding to shooting.However, this pre-focus operation is difficult for beginners to understand. Today, as the performance of automatic focus detection devices has improved, most of the out-of-focus photos are caused by forgetting or erroneously operating the prefocus operation. In Japanese Patent No. 58-145068, they proposed an automatic focus detection device that does not require the above-mentioned prefocus operation by projecting spot light toward various locations on both sides of the photographic surface and obtaining a plurality of distance measurement information from the reflected light. However, the method proposed in Japanese Patent Application No. 58-145068 simply averages the detected distance measurement results and makes the focus position of the photographing lens correspond to the average distance. The main subject intended by the photographer was treated equally as the intended subject, and although the subject was in focus overall, it was not possible to obtain a sufficiently satisfactory focus on the main subject intended by the photographer. Purpose) The present invention has been made in view of the above circumstances, and in a distance measuring device that can measure distances at multiple points on the photographic screen, distance measurement information near the center of the photographic screen can be used to store distance measurement information on other parts. Compared to conventional automatic focus detection devices, which are equipped with a center focusing means to handle the subject more intensively, and are configured to only measure the distance at the center of the shooting screen when the main subject is located at the center of the shooting screen. A camera distance measurement that enables comparable focusing, and also has excellent functionality and operability to focus on the main subject without performing prefocus operations when the main subject is at the edge of the shooting screen. (Embodiment) An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a strategic configuration diagram of a distance measuring device for a camera according to the present invention; An infrared light-emitting element 2 serves as a light-emitting element, and 2 is a light-emitting lens serving as a light-emitting optical system for projecting the signal light from the infrared light-emitting element 1 toward a subject. A lens is integrally formed to divide and project the signal light emitted from the infrared light emitting element 1 to three different locations at the center and periphery of the photographic screen. 3 is a light-receiving lens as a light-receiving optical system for guiding the light reflected by the subject of the signal light projected onto the three locations on the photographic screen to the light-receiving element 4;
Similar to the light projecting lens 2, three lenses having different optical axes are integrally formed, and all the reflected light is made to enter the light receiving element 4. Here, the angles formed by the three optical axes of the light projecting lens 2 and the angles formed by the three optical axes of the light receiving lens 30 are the same from a three-dimensional perspective. That is, by moving the three optical axes of the light projecting lens 2 in parallel, they can be superimposed on the three optical axes of the light receiving lens 4. In this embodiment, the light receiving element 4 is a semiconductor device detector (PSD).
is used, and distance measurement is performed by the light receiving element 4 detecting the incident position of the reflected light, which changes depending on the distance to the subject. In a semiconductor device detector, the ratio of outputs at both ends changes depending on the light receiving position of the incident light, and by detecting this ratio of outputs, the object distance can be determined. A specific processing circuit for this purpose is published in Japanese Patent Application Laid-Open No. 57-4481.
The circuit A as disclosed in Publication No. 9 etc. is connected to the light receiving element 4.
Just connect to. In this embodiment, the light-receiving element 4 receives reflected light from three locations on the photographic screen, but if the objects at the three points are all at the same distance, the reflected light will be reflected from the light-receiving element 4. Even if they are not incident on the same position, the incident position is directly detected as the subject distance. Furthermore, when the objects at three locations on the photographic screen are at different distances, the reflected light enters the light receiving element 4 at different positions, but in that case, the weighted average position of the amount of incident light at those incident positions is This will be detected as the subject distance. By the way, out of the three points in the above photographic screen where the distance is measured,
In the case where only the yI point captures the subject and the other two points measure the background of the subject (which is actually the case in most cases), what is detected as the subject distance is conventionally Under the influence of the above-mentioned background, a situation has arisen in which the object distance becomes even further away than the original object distance. For this reason, when such a distance measuring device is used as an automatic focus detection device of a camera, there is a problem in that it becomes impossible to obtain a photograph with a sufficiently satisfactory focus on the subject originally intended by the photographer. Therefore, when considering the subject that this photographer intends to photograph, it turns out that when taking a photograph, the subject is generally placed in the center of the screen.
Most of the time, the subject is placed in the center of the screen. Therefore, most photographs will be satisfactory if distance information is obtained that will always properly focus on the object at the center of the photographic screen among the three distance-measured points on the photographic screen. Become something. Therefore, in the present invention, a center emphasis means is provided, which gives more importance to the distance measurement information for the vicinity of the center of the photographic screen among the three points on the photographic screen where the distance is measured, compared to the distance measurement information for other parts.
This allows you to focus on the subject located in the center of the shooting screen. In this embodiment, the area of the lens part of the light projecting lens 2 that projects the signal light toward the vicinity of the center of the photographic screen is used as the center focusing means, and the area of the lens portion that projects the signal light toward the vicinity of the center of the photographic screen is The area of the lens part is also set large. The ratio of the amount of signal light that is split and projected to three locations on the photographic screen is proportional to the ratio of the area of the corresponding lens portion of the projection lens 2, and therefore the ratio of the amount of reflected light is also basically It is proportional to the area ratio of the corresponding lens portion of the light projecting lens 2. Therefore, a larger amount of reflected light from an object present near the center of the photographic screen enters the light receiving element 4 than any reflected light from any object present at the periphery of the photographic screen. The light-receiving element 4 composed of a PSD detects a weighted average value according to the amount of incident light at the incident position as the subject distance, so distance measurement information about the subject near the center of the shooting screen where a lot of reflected light enters is collected from the periphery of the shooting screen. As a result, the output from the light-receiving element 4 becomes object distance information suitable for focusing on an object located near the center of the photographic screen. In addition, in the above description, the center-weighted means is constructed by setting the area of the lens portion that projects the signal light to be larger (compared to any other lens portion) toward the vicinity of the center of the photographing screen for the light projection lens. However, the same can be said about the light receiving lens 3. That is, by setting the area of the light-receiving lens 3 that receives the reflected light from near the center of the photographic screen larger than the area of any other lens part, the center-weighted means can be used as in the case of the light-emitting lens 2. Can be configured. Note that the ratio of the total amount of signal light incident on the light receiving element 4 is the product of the area ratio of the light projecting lens 2 and the area ratio of the light receiving lens 3. As shown in Fig. 2, a specific method for making the light emitting lens 2 or the light receiving lens 3 in the first device is to cut a part of each lens from three lenses 5, 6.7 having the same performance. The composite lens 8 having three optical axes a, b, and c can be obtained by taking out the lenses and joining them together. Next, the ratio of the area of the lens portion of the light projecting lens 2 or the light receiving lens 3 that projects the signal light toward the vicinity of the center of the photographic screen to the area of the other lens portions will be further described. Figure 3 shows how the distance to the subject is set to 1.
A graph is shown in which the degree of blur in focus when the background distance is gradually increased to 5 m is calculated for a photographic lens with a focal length of 38 mm and an open F number of F2.8. Note that the amount of reflected light is approximately inversely proportional to the square of the distance,
Proportional to reflectance. In Figure $3, the vertical axis shows the diameter of the circle of confusion of the subject image, and the horizontal axis shows the distance to the background. In the figure, ■ is a graph when the light intensity ratio of the reflected light reflected by the subject and the reflected light reflected by the background for the same distance is set as 1 = 4.
is a graph when the same light amount ratio is 1:2, ■ is a graph when the same light amount ratio is 1 = 1, ■ is a graph when the same light amount ratio is 2:1, ■ is a graph when the same light amount ratio is 2:1, and ■ is a graph when the same light amount ratio is 1:1. This is the diameter of the circle of confusion of the subject when the background is in focus, which occurs in the detection device. Generally, the allowable circle of confusion diameter for a 35mm camera is 0°03~0.
．． Although it is said to be 0.035, if general photographing conditions are considered, the diameter of the lead part can be allowed up to about 0.035. In addition, considering the difference in reflectance between the background and the subject, the ratio of the amount of light reflected near the center of the shooting screen at the same distance and the same reflectance to the amount of light reflected from other parts is It is preferable that the sum of the amounts of reflected light in the portions≦the amount of reflected light near the central portion. Therefore, when measuring the distance near the center of the shooting screen and two other places, the amount of reflected light near the center of the shooting screen is the amount of reflected light as the distance measurement information for 1fIJ other than the center of the shooting screen. It is preferable to make it about half or less. On the other hand, in order to produce an effect as distance information on distance measurement information other than near the center of the photographic screen, K requires a certain amount of reflected light at areas other than the center of the photographic screen, so this will be discussed. Considering the case of shooting with two people side by side, which is the most common failure when using conventional automatic focus detection devices,
The signal light projected toward the center area is in the background, and the other 2
It can be assumed that the signal light reflected towards the location hits the original subject. In this state, conventional distance measuring devices that measure distance only at the center of the photographic screen often result in out-of-focus photographs with the diameter of the circle of confusion shown in the graph (2) in FIG. 3. In three-point distance measurement, if this can be improved to some extent, it can be said to be effective, but even if the diameter of the circle of confusion changes from 0.3 to 0.2, it is still out of focus. In general outdoor shooting, it is thought that the f-number will be stopped down to about F5.6 or less in most cases, so the diameter of the circle of confusion will be less than half, and it will be effective up to about ■ in Figure 3. It can be determined. The ratio of the amount of reflected light corresponding to the vicinity of the center of the photographic screen to the amount of reflected light from other parts is set to approximately the amount of reflected light near the center/4≦the sum of the amounts of reflected light in areas other than the vicinity of the center. preferable. Therefore, when measuring the distance near the center of the shooting screen and two other places, the amount of reflected light as the distance measurement information for one point other than the center of the shooting screen is the amount of reflected light near the center of the shooting screen. It is preferable to set it to about 1/8 or more. To summarize the above, in a general 35 mm camera, it is preferable that the ratio of the amount of light reflected near the center of the photographic screen to the amount of light reflected from other parts be approximately the same. In addition, when measuring distances near the center of the shooting screen and two other locations, the ratio of the amount of reflected light at one point other than near the center of the shooting screen to the amount of reflected light near the center of the shooting screen is approximately the same. It would be a good thing to do. By using the above light quantity ratio as the area of the lens part and other lens parts in the vicinity of the center of the photographing screen in the light emitting lens or the light receiving lens, it is possible to construct a "center weighted means" that provides the above light quantity ratio. It is possible to obtain distance measurement information that is extremely suitable for In the above embodiment, the ratio of the amount of reflected light is set by the area of the lens portion corresponding to each optical axis direction of the projecting and receiving lenses, but the ratio of the amount of reflected light can be set by changing the transmittance of the lens portion. is also possible. In this case, it is also possible to adjust by providing a filter or the like on the front surface of the lens. FIG. 4 shows another embodiment of the present invention, in which mirrors are used to divide and project the signal light in three directions on the photographic screen. In the figure, 9 is an infrared light emitting element similar to that in FIG. 1, and 10 is a projection lens, which has only one optical axis. Reference numeral 11 and 12 reflect the signal light from the infrared light emitting element 9 with a reflecting mirror to form a projected spot image c on the object surface P. Note that a is a projected spot image formed by the signal light directly projected from the infrared light emitting element 9 without passing through the reflecting mirrors 11 and 12. 13 is a light receiving lens which, like the light projecting lens 10, has only one optical axis. 14 is the first
This is a light receiving element similar to the one shown in the figure. The spot image a on the subject surface P is directly focused on the light receiving element 14 by the light receiving lens 13, and the projected spot image on the subject surface P is formed by the light receiving lens 1.
3, is reflected by a mirror 15, and is imaged on a light receiving element 14. The projected light spot image C on the object surface P is also reflected by the mirror 16 through the light receiving lens 13,
An image is formed on the light receiving element 14. In this case, the light intensity (contribution rate to distance measurement) of each projected spot image can be adjusted by the effective area of the lens and the size of the reflective surface of the mirror, and the light emission distribution of the infrared light emitting element 9 and the above-mentioned Taking into consideration the reflectance of the mirror, etc., each area may be set so that the reflected light amount ratio falls within the above-mentioned range. By the way, in order to minimize the influence of extraneous light on the membrane, it is necessary to pay attention to the distribution of the transmission light amount ratio between the light projecting system and the light receiving system. Now, if the energy of the unit solid angle beam of the light source is constant, E1
The solid angle covered by the part of the light emitting lens with an optical axis aiming at approximately the center of the screen is Pc1 The solid angle covered by each of the other parts with optical axes is Ps, Similarly, the light receiving lens has an optical axis aiming at almost the center of the screen. Assuming that the solid angle from the subject of the part is Rc, the solid angle covered by each of the other parts with optical axes is Rs, and the external light intensity on the subject surface is N, the amount of reflected light that enters the light receiving element Sp is 8p= (Pc-Rc+Ps-Rs・2)・S (reflectance of subject 1) The amount of extraneous light NP is Np=(Ro+R8・2)・N The ratio of the total amount of reflected light to the amount of extraneous light is S P / NP. Also, if X is the ratio of the amount of projected light aimed at approximately the center of the shooting screen and the amount of projected light aimed at other parts, then x=Po-Ro/(Pg-Rs) When X is constant, 8P/NP is maximized. What is necessary is to select the light intensity ratio of the center 2 and periphery of light emission and light reception such that The result is P O / P 8 '' 6t R' / R♂ = i.Press the tab so that the ratio of the amount of reflected light near the center of the shooting screen and other parts becomes 6 = 1, and When the upper side has uniform brightness, the ratio of the amount of light that passed through the light-receiving lens part that has an optical axis relative to the fuzzy central part of both sides and the light amount that passed through the light-receiving lens part that has other optical axes is 6 = 1. Note that in this embodiment, in order to measure distances at multiple points, the light emitting and receiving lenses have multiple optical axes, or a mirror is used. However, this may be achieved by using a prism or the like.In this case, the reflected light amount ratio can be selected by N sections based on the area of the reflecting surface or the reflectance.In the above embodiment, the signal light is set at the center of the photographic screen. The case where the signal light is projected toward a total of three locations, one near the center and two at the periphery is shown, but if you follow the premise that the signal light is projected near the center of the shooting screen and other points, then how many points can the signal light be projected onto the shooting screen? It goes without saying that the present invention can be applied to any of these cases. (Effects of the Invention) As explained above, the present invention allows the distance measuring device to measure multiple locations on the photographic screen near the center of the photographic screen. Since the camera is equipped with a center-weighted means to handle distance measurement information more heavily than other distance measurement information, even if the main subject is not near the center of the shooting screen, the main subject can be photographed without performing prefocus operations. If you can obtain distance measurement information that allows you to focus on the subject, and if the main subject is near the center of the shooting screen, focusing on the main subject, which tends to be difficult with this type of rangefinder, is difficult compared to conventional methods. The effectiveness of this method is extremely high, as it allows you to obtain distance measurement information that is comparable to distance measurement devices that measure only the center of the photographic screen.4. Explanation Fig. 1 is a schematic configuration diagram showing an embodiment of a distance measuring device for a camera according to the present invention, Fig. 2 is an illustration of the projection of Fig. 1. A graph showing the relationship between a subject and a background with respect to blur, and FIG. 4 is a schematic configuration diagram showing another embodiment of a distance measuring device for a camera according to the present invention. 1.9... Infrared light emitting element, 2.10... ... Light projecting lens, 3.13 ... Light receiving lens, 4.14 ... Light receiving element, 11, 12, 15.16 ... Reflecting mirror. Distance of patent applicant Canon Co., Ltd.

Claims (2)

[Claims] (1) In a distance measuring device capable of measuring distances at multiple points within the screen, a center emphasis means is provided to handle distance measurement information near the center of the screen more heavily than distance measurement information from other parts. A distance measuring device characterized by: (2) Other parts for distance measurement information near the center above