JPS61246725A - Range finder for camera - Google Patents

Abstract

PURPOSE:To focus a camera on a main subject even if the main subject is located on the edge of a photographic picture plane by setting up the quantity of projection of a projecting element for range-finding a position near the center part of the photographing picture plane larger than that of projecting elements for range-finding the priphery. CONSTITUTION:The projecting element 1 for range-finding a position near the center part of the photographing picture plane is constituted of a light emitting element having high performance such as a semiconductor laser and the projecting elements 2, 3 for range-finding the peripheral part are constituted of inexpensive infrared ray emitting diodes so that the reflected light of signal light from the projecting element 1 is made incident upon a photodetecting element 6 and the reflected light of signal light from the projecting elements 2, 3 is made incident upon the photodetecting element 6 through mirrors 7, 8. The resistance ratio of resistors 15, 16 is set up so that the quantity of projection of the projecting element 1 is larger than that of the projecting elements 2, 3. Even if the main subject is located on the edge of the photographing picture plane, the camera can be focused on the main subject without pre-focusing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a distance measuring device for a camera that can measure distances at multiple locations within a photographic screen.

(Prior art) In conventional cameras, the so-called distance measuring device that detects information corresponding to the distance to the subject in order to automatically perform focus detection only measures the distance near the center of the shooting screen. was being carried out. Therefore, in the case of a composition with the subject at the edge of the shooting screen, first place the subject within the distance measurement mark provided approximately in the center of the viewfinder, perform only distance measurement for the core subject, and then It is necessary to perform a so-called prefocus operation, which involves repositioning the subject at the edge of the viewfinder and proceeding with the shooting operation while retaining distance measurement information.

However, this prefocus operation is difficult for beginners to understand, and now that the performance of automatic focus detection devices has improved,
Most of the out-of-focus photos are caused by forgetting or erroneously using this prefocus operation.

Therefore, in Japanese Patent Application No. 58-145068, the present applicant proposed the above-mentioned prefocus operation by projecting spot light toward various parts of the photographic screen and obtaining a plurality of distance measurement information from the reflected light. We are proposing an automatic focus detection device that does not require

However, the method proposed in Japanese Patent Application No. 58-145068 simply averages the results of multiple distance measurements detected, and the focus position of the photographing lens corresponds to the average distance. The main subject intended by the photographer and the other subject are treated equally, and although the main subject is in focus overall, it is difficult to achieve a sufficiently satisfactory focus on the main subject intended by the photographer. For example, when measuring distance at 93 different locations on the shooting screen, one of the three locations may be
If only one spot captures the main subject and the other two spots measure the background of the main subject (5j!, this is almost always the case), the book will be detected as the subject distance. Due to the influence of the background mentioned above, the distance of the main subject is shifted to a distance of 9 points from the original distance of the main subject.

(Object of the Invention) The present invention has been developed based on the above-mentioned circumstances, and has a plurality of light emitting elements that project signal light. The amount of light emitted by a light emitting element that enters the distance measuring device of the camera to measure the distance near the center of the photographic screen is the amount of light emitted by each light emitting element used to measure the distance around the periphery of the photographic screen. If the main subject is located at the edge of the shooting screen by configuring the camera so that it is larger than the amount of light, surface distance measurement information can be obtained to focus on the main subject without performing prefocus operations. , if the camera is close to the center of the shooting screen, it is possible to obtain distance measurement information that enables focusing to be as good as conventional distance measuring devices that only measure the center of the shooting screen. It is a turtle trying to provide a distance measuring device.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a distance measuring device for a camera according to the present invention. In the figure, 1.2.3 are light projecting elements that emit signal light to measure the distance to the subject. Among them, light projecting element 1 is a high-performance light emitting element such as a semiconductor laser, and the signal light is used as a light projecting optical system. The signal light is projected toward the approximate center of the photographic screen through the projection lens 4, and the signal light is an inexpensive infrared light emitting diode used in remote controls for televisions with two or three projection elements. The light is projected through the lens 4 toward different neighboring areas of the photographic screen. In this way, the signal light projected toward three different locations on the photographic screen is reflected by the subject, and the signal light reflected from the light projecting element 1 is transmitted directly to the light receiving element via the light receiving lens 5. 6 and the signal light reflected from the light projecting elements 2 and 3 is once reflected by a mirror 7.8 as a reflecting member.
The light is incident on the light receiving element 6. A semiconductor device detector (P8D) is used in the light receiving element 6, and outputs object distance information according to the incident position of the three reflected lights and the amount of incident light. The position of incidence on the light receiving element 6 changes depending on the subject distance, and the position of incidence on the light emitting element 1,
2.3 are arranged in a line in a direction perpendicular to the baseline length, and mirrors 7.8 are arranged so that a common perpendicular surface to their reflecting surfaces is perpendicular to the baseline length, and the above three reflections Of the light, the reflected light reflected by the subject at the same distance is made to enter the light receiving element 6 at the same position.

In the light-receiving element 6, the output ratio at both ends changes depending on the weighted average position of the incident light amount at the incident position of the reflected light, and this output ratio becomes object distance information.

Figure 2 shows a circuit diagram for driving the light projecting elements 1, 2, and 5 in Figure 1. In Figure 2, 9 is a power source, for example, a 9-lithium battery that has been popularly used in cameras in recent years. It has an open circuit power supply of approximately 6V, such as a battery. ・10 is a switch for starting distance measurement, which is usually also used as a release button, and when turned on, turns on power 9 to each circuit element. ・1, 2.3 are switches for starting distance measurement. In the light projecting elements shown in FIG. 1, the light projecting elements 2.3 are connected in series to the power source 9, and connected in parallel to the light projecting element 1. 11
The distance measurement control circuit including the light receiving element 26 shown in the tl/IJ1 diagram starts operation when the distance measurement start switch 100 is turned on.
Forming object distance information according to the output of the light receiving element 6.
Note that the distance measurement control circuit 11 is based on Japanese Patent Application Laid-Open No. 57-4480.
The circuit disclosed in Japanese Patent No. 9 can be applied.

Reference numeral 12 designates a known light emitting element drive circuit, in which when the distance measurement l start switch 10 is turned on, a transistor 13 connected to the light emitting element 1 and a transistor 140 connected to the light emitting element 2.3 are turned on. The same voltage is applied at a predetermined period. When a voltage is applied to the base of the transistor 13.14, a current flows through the light emitting elements 1, 2.3, and the light emitting elements 1, 2.
．． As described above, signal light having nine predetermined frequencies according to the period of the voltage applied to the bases of the transistors 13 and 14 is projected from 5 to three locations on the photographing screen. A resistor 15 for setting the current value flowing through the light emitting element 1 is connected to the side of the transistor 13, and the voltage generated at the connection point aK is fed back to the light emitting element drive circuit 12. - A voltage proportional to the current value flowing through the light emitting element 1 is generated at the connection point a, and the light emitting element drive circuit 12
Now, transistor 1 is connected so that the voltage at connection point a remains constant.
On the other hand, the voltage applied to the base of the transistor 14 is also applied from the light emitter drive circuit 12 to the base of the transistor 130. Since the same voltage is applied to the light emitting elements 2 and 3, the current flowing through the light emitting elements 2 and 3 is made constant, and the ratio of the current flowing through the light emitting elements 2 and 3 to the current flowing through the light emitting element 1 is reduced. is the resistor 1 connected to the emitter side of the transistor 14
It can be set with only a resistance value of 6. In other words, if the resistance value of the resistor 16 is set to the same value as the resistance value of the resistor 15, a current value approximately equal to the current value flowing through the light emitting element 1 will flow through the light emitting element 2. 15
If the resistance value is made larger than the resistance value of b, a current value smaller than the current flowing through the light emitting element 1 will flow through the light emitting element 2.5.
In this case, it is assumed that the characteristics of the transistors 13 and 14 are the same.

It goes without saying that the same effect as described above can be obtained even if the voltage on the emitter side of the transistor 14 is fed back to the light emitting element drive circuit 12#c instead of the voltage at the connection point a.

In the above configuration, in this embodiment, the amount of light projected by the light projecting element 1 which projects the signal light toward the approximate center of the photographing screen is different from that of the light projecting element 1 which projects the signal light toward the peripheral part of the photographing screen. , 2, resistor 15 and resistor 1 so that the amount of light emitted is greater than that of any of
A resistance ratio of 6 is set. As a result, basically, the amount of reflected light from the subject near the center of the photographic screen is incident on the light receiving element 6 in a larger amount than the reflected light from any of the objects located at the periphery of the photographic screen. P8D
The light-receiving element 6, which is comprised of Distance information] This is reflected in the fact that it is treated with great importance. As a result, when the main subject is near the center of the shooting screen, the signal light projected towards the center of the shooting screen out of the three signal lights will capture the main subject and will be directed toward the periphery of the shooting screen. Even if the other two projected signal lights capture the background, it is possible to obtain distance measurement information that enables satisfactory focusing on the main subject without being affected by the background. become. When taking pictures, the main subject is generally placed in the center of the shooting screen, and in fact, in 70 to 80% of snapshots, the main subject is placed in the center of the shooting screen. If you pay more attention to the distance measurement information near the center of the photographic screen, you will be able to obtain satisfactory photographs in most cases. By the way, when setting the resistance ratio between the resistor 15 and the resistor 16, the luminous efficiency of the light emitting element 1.2.3 is a problem.
In this embodiment, as described above, the light emitting element 1 is equipped with a light emitting element with high luminous efficiency, such as a semiconductor laser, and the light emitting elements 2 and 3 are equipped with light emitting elements with low luminous efficiency, such as infrared light emitting diodes. Therefore, even if the resistance ratio of the resistor 15 and the resistor 16 is made almost equal and the current values flowing through the light emitting element 1 and the light emitting element 2.5FC are almost the same, the light emitting element 1 will not emit light due to the light emitting efficiency. The amount of light is greater than the amount of light emitted by any of the light projecting elements 2.3.

Next, a preferable ratio of the amount of light emitted by light projecting elements 1 and 3 will be described. .

Figure 3 shows the distance to the subject L5 using the amount of reflected light reflected by the subject and the amount of reflected light reflected from the background as parameters.
m, and the degree of blurring when the background distance is gradually moved away is the focal length f=e38tII, wide open? Number F2.
A graph calculated for No. 8 photographic lens is shown.

Note that the amount of reflected light is approximately inversely proportional to the square of the distance,
Proportional to reflectance. In FIG. 3, the vertical axis shows the diameter of the circle of confusion of the subject, and the horizontal axis shows the distance to the background. (1) # in the diagram
i''The graph when the light intensity ratio of the reflected light from the subject at the same distance and the reflected light reflected from the background is set to 1:4, (2) is when the light intensity ratio is set to 1:2. The graph of (
3) is a graph when the same light amount ratio is 1 = 1, (4) is a graph when the same light amount ratio is 2:1 and is a graph at 9 o'clock, (51a) When the background is in focus, which occurs with a conventional automatic focus detection device is the diameter of the circle of confusion of the subject.

The allowable circle of confusion diameter for a typical KS5I3+ camera is 0.03~
Although it is said that the diameter of the circle of confusion is approximately 0.05, considering general photographing conditions and the like.

In addition, considering the difference in reflectance between the background and subject, the ratio of the amount of light reflected near the center of the photographic screen at the same distance and the same reflectance to the amount of light reflected from other parts is different from that near the center. It is preferable that the total amount of reflected light in the portion ≦the amount of reflected light in the vicinity of 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 distance measurement information for one point 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, a certain amount of reflected light near the center of the photographic screen is required, so this will be discussed.

Considering the case where two people are photographed side by side, which is the case when conventional automatic focus detection devices fail in most cases, the signal light projected towards the center of the photographic screen may be projected onto the subject in the background and two other places. It can be assumed that the signal light projected towards the subject hits the original subject. In this state, in a conventional distance measuring device that measures only the center of the shooting screen, the diameter of the circle of confusion shown in the graph in Figure 3 (5) It can be said that it will be effective if this can be improved to some extent in distance measurement at 03 points, which often resulted in out-of-focus photos, but even if the diameter of the circle of confusion is 0.3, it will still be out of focus. It's out of focus. Most of the time in general outdoor shooting? Since it is considered that the number is narrowed down to about F5.6 or less, the diameter of the circle of confusion is also less than half, and it can be determined that it is effective up to about (1) in Fig. 5. -1 - Calculate the ratio of the amount of reflected light near the center of the shooting screen to the amount of reflected light from other parts: amount of reflected light near the center/4≦
It is preferable that the amount of reflected light be approximately the sum of the amounts of reflected light in areas other than the vicinity of the center.

Therefore, when measuring distance near the center of the shooting screen and two other locations, the amount of reflected light as distance measurement information for one point other than the center of the shooting screen is 178 times the amount of reflected light near the center of the shooting screen. It is preferable to set it to the above range.

To summarize the above, in a general 35-view camera, it is preferable that the ratio of the amount of light reflected near the center of the photographing screen to the amount of light reflected from other parts be approximately the same.

In addition, for those that measure distances near the center of the shooting screen and two other locations, the ratio of the amount of reflected light per 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 〇For that reason, the light emitting elements 1, 2. ! If you want to make the amount of light emitted by light emitting element 1 greater than that of light emitting elements 2 and 3, assuming a luminous efficiency of 1, by setting the resistance ratio of resistor 15 to resistor 16 to be small, light emitting element 2 , 31C, the ratio of the current flowing through the light projecting element 14C becomes larger, and the current flowing through the light projecting element 1 increases.
As the ratio of the amount of light emitted increases, the amount of light emitted from the light emitting element 1 is made smaller than the amount of light emitted from the light emitting element 2.3.
By setting a large resistance ratio of the resistor 15 to the resistor 6, the ratio of the current flowing through the light emitting element 1 to the light emitting elements 2 and 3 can be reduced. can. It goes without saying that even if the light emitting element 1 and the light emitting elements 2 and 3 are light emitting elements with the same efficiency, the resistance ratio of the resistor 15 and the resistor 16, etc. will cause the light emitted by the light emitting element 2 and 3 to be different. By increasing the proportion of the current flowing through the optical element 1, it is possible to construct a center-weighted means that treats the distance measurement information near the center of the photographic screen more heavily than the distance measurement information of other parts of the photographic screen, as described above.

In this embodiment, the amount of light emitted by the light emitting element for distance measuring near the center of the photographic screen is made smaller than the amount of light emitted by the light emitting element for distance measuring the peripheral part of the photographic screen. Although the focus means is configured, it is also possible to make the amount of light emitted by the light projecting element uniform and configure the center focus means on the light receiving element side. In this case, the mirror 7.8 in Fig. 1 is not provided, and the reflected light from two places, one near the center of the shooting screen and the other at the periphery of the shooting screen, is received by separate light-receiving elements (PODs). Either use a light-receiving element that receives reflected light from near the center of the photographic screen with a higher sensitivity than other light-receiving elements, or use a light-receiving element that receives reflected light from near the center of the shooting screen. The output of the element can be reduced using a resistor or the like.

Incidentally, in these cases, if the outputs from both ends of each light receiving element are finally added together, an output equivalent to the output from both ends of the light receiving element 60 shown in FIG. 1 can be obtained as ranging information.

In the above embodiment, the current value is used as a means for changing the amount of light emitted by the light emitting element, but for a light emitting element whose light amount changes depending on the voltage value, a circuit that converts the current value into a voltage value is used. Bye.

Further, as a means for changing the current value, a transistor, an operational amplifier, etc. may be used in addition to the above-mentioned resistor. Furthermore, the first
DKyt for mirror 6.7 in the figure.

Optical systems such as compound lenses or prisms with different axial directions may also be used.

In this embodiment, the light emitting amount of the plurality of light emitting elements is differentiated by combining a high output light emitting element and a low output light emitting element, so that the center weighting means can be configured extremely easily. In this embodiment, a light projection element that projects a signal light near the center of the photographic screen and a light projection element that projects signal light around the peripheral part of the photographic screen are driven in parallel, and the driving state of only one element is fed back. Since both elements are driven and controlled by the feedback signal, only one control circuit is required for this purpose, and the ratio of the amount of light emitted to form the center-weighted means can be set extremely easily. has.

In the above embodiment, the case where the signal light is projected toward a total of three locations, one near the center of the photographic screen and two at the periphery, was shown, but the signal light is projected toward three locations, one near the center of the photographic screen and two other locations. It goes without saying that as long as the premise is followed, any number of locations for projecting the signal light onto the photographic screen may be provided, and the present invention can be applied to any of these cases.

(Effects of the Invention) As explained above, the present invention has a plurality of light emitting elements that project signal light, and the camera measures distances at different points on the photographic screen in correspondence with each light emitting element. In a range device, one light emitting element is used to measure the distance near the center of the shooting screen, and the amount of light emitted from the light projecting element is used to measure the distance near the center of the shooting screen.)
Since the amount of light emitted is larger than that of the camera, even if the main subject is near the center of the shooting screen, it is possible to obtain distance measurement information that allows you to focus on the subject without performing prefocus operations. When the main subject is near the center of the photographic screen, this type of distance measuring device is particularly difficult to focus on. It is possible to obtain ranging information that is comparable to that of distance measuring devices, and the effect is extremely high.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an embodiment of a close range device for a camera according to the present invention. Fig. 2 is a circuit diagram of the device shown in Fig. 91. Fig. 3 shows the relationship between the subject and the background with respect to out-of-focus. graph. 1.2.5-... Light emitting element 4... Light emitting lens 5... Light receiving lens 6... Light receiving element 7.8... Reflecting mirror 11... Distance measurement Control circuit 12...Light emitter drive circuit 13th

Claims (1)

[Claims] In a camera distance measuring device that has multiple light emitting elements that project signal light and measures distances at different points on the photographic screen corresponding to each light emitting element, it is used to measure the vicinity of the center of the photographic screen. A distance measuring device for a camera, characterized in that the amount of light emitted by a light emitting element for distance measurement is larger than the amount of light emitted by each light emitting element for measuring a peripheral part of a photographic screen. .