JPH01187510A - Rangefinding device for camera - Google Patents

Abstract

PURPOSE:To cover a main object within a focusing range in high probability and to keep the excellent description of a close view and a distant view by setting the set position of a lens so that the lens is let to come near to a short distance side within a range which is not out of the apoastron of the depth of the field of the lens. CONSTITUTION:A rangefinding information detection circuit 20 outputs rangefinding signals from a light receiving sensor 14 to a microprocessor unit (MPU) 22 as the rangefinding information. The MPU 22 incorporates lens set position information in accordance with the combination of said rangefinding information and the luminance information of the object from a photometric element 8 from a lens set position table 24 and sets the photographic lens 2 so that the lens is let to deviate to the short distance side in the range where an infinity or the position of a specific distance is not out of the apoastron of the depth of the field of the photographic lens 2. Thus, the focusing range can be enlarged to the short distance side while covering a long distance side and not only the main object 18 but also the close view and the distant view can be covered within the focusing range in high probability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photoelectric distance measuring device suitable for photo cameras and video cameras.

[Conventional technology]

Most modern photographic cameras, such as lens-shutter compact cameras, have a built-in autofocus device. This autofocus device generally includes a photoelectric distance measuring device and a lens setting mechanism.

The distance measurement device detects a distance measurement signal that correlates with the distance to the object based on the reflected light from the object, and the lens setting mechanism advances the photographing lens to the position corresponding to the distance measurement signal obtained by the distance measurement device. Control.

Among such distance measuring devices, a floodlight type distance measuring device emits a slit light toward the subject and measures the distance by receiving the light reflected from the subject. The device is known. This eliminates the need for aiming operations when measuring distance compared to those that project a spot light, and also makes it possible to measure the distance between two people, for example, when photographing a subject lined up. So-called hollowing out can prevent distance measurement and is very effective for simple cameras.

By the way, when there is only one distance measurement signal detected by the distance measurement device, the setting position of the photographic lens can be uniquely determined according to this distance measurement signal, but in reality, only the main subject is detected. Photography screens are rare, and in general, in addition to the main subject, secondary liquid objects and background objects are often mixed together in the photographic screen. Therefore, a plurality of distance measurement signals are obtained from such a general photographic screen, and it becomes impossible to unambiguously determine the set position of the photographic lens.

From this point of view, when multiple distance measurement signals are detected, there is a short distance priority method that prioritizes the one with the closest subject distance, or simply prioritizes the short distance as known from Japanese Patent Application Laid-open No. 146028/1983. In addition to this, there is a method of performing a logical operation that takes into account the depth of field of the photographing lens, and setting the photographic lens at a position that includes the closest subject distance within the near point of the depth of field.

[Problems to be Solved by the Invention] However, the short-distance priority method described above has a drawback in that when the main subject is photographed together with a close-up view, the main subject becomes out of focus. Also, JP-A-59-14602
In the method described in Publication No. 8, when multiple distance measurement signals are detected, the focus area is expanded to the far distance side using the one corresponding to the closest subject distance as a reference. If the distance measurement signal obtained is from the main subject, the depiction of the foreground will deteriorate and only the depiction of the background will be improved, which is not very desirable as a photographic image. .

The present invention was made in order to solve the above-mentioned drawbacks of the conventional technology, and even when multiple distance measurement signals are detected, the main subject can be detected within the focusing range with the highest probability. An object of the present invention is to provide a distance measuring device for a camera that can maintain good depiction of both near and distant views while keeping the camera cool.

[Means for solving problems]

In order to achieve the above object, the present invention includes a light receiving sensor that receives reflected light from a subject and outputs distance measurement information corresponding to the subject distance, a photometer that outputs subject brightness information, and a photometer that outputs the distance measurement information and photometry. Based on the output from the means, when infinity or a predetermined distance position on the far side is included within the depth of field of the photographing lens, the infinity or the predetermined distance position is included in the depth of field of the photographing lens. A lens set position determining means is provided for setting the set position of the photographic lens closer to the near distance side within a range that does not deviate from the far point of the lens.

Embodiments of the present invention will be described below with reference to the drawings.

〔Example〕

In FIG. 5, which shows a camera using the present invention, a camera body l has a photographing lens 2 provided almost at the center of its front surface, and a finder 3 and a light emitting unit 4 of a strobe device arranged at the top. There is.

Also, on the top of the camera body 1, there is a shank button = 5-
'5 is provided. The light emitting unit 6 of the distance measuring device is placed between the photographing lens 2 above and below. A light receiving section 7 is arranged,
These are separated by a baseline length. The light projecting unit 6 projects a wide slit light toward the subject in a direction perpendicular to the base line length. The light receiving section 7 has a light receiving surface extending in a direction perpendicular to the base line length, receives light reflected by an object, and outputs a signal indicating the light receiving position. Note that the reference numeral 8 indicates a photometric element for photometrically measuring the subject brightness.

As is well known, the photometric output from the photometric element 8 determines the maximum aperture of the programmed shutter, that is, the F-number of the photographic lens, which allows proper exposure to be obtained.

In FIG. 1 showing the principle of the distance measuring device of the present invention, the light projecting section 6 includes a strobe light emitting tube 9 that emits distance measuring light, and a slit plate that shapes the light from the strobe light emitting tube 9 into a slit shape. 10, and an infrared filter 11 that transmits only near-infrared light.
and a light projecting lens 12. The optical axis 12a of the light projecting lens 12 is parallel to the optical axis 2a of the photographing lens 2. As a result, the light projecting section 6 projects slit light in the near-infrared region and wide in the horizontal direction toward the subject.

Further, the light receiving section 7 includes a light receiving sensor 14, a lens 15, and a visible light cut filter 16. The optical axis 15a of the lens 15 is parallel to the optical axis 12a of the projection lens 12. The light-receiving sensor 14 disposed on the focal plane of the lens 15 includes five light-receiving elements A+, Az, A3, A-, and As arranged along the base line length. The light receiving sensor 14 receives the light reflected by the subject out of the slit light projected towards the subject. For example, when the main subject 18 is in the position shown in the figure, the light reflected by it enters the light receiving element A1 in the light receiving sensor 14, and the secondary liquid photographing object 19
The reflected light is incident on the light receiving element A2.

A distance measurement information detection circuit 2o is connected to the light receiving sensor 14. This ranging information detection circuit 2o includes a light receiving sensor 1
4, that is, in the above case, the distance measurement signal from light receiving element A
1. The signal of the reflected light from the subject entering A2 is rl
It is output to the microprocessor unit 22 (hereinafter referred to as MPU 22) as ranging information of loooJ. Also,
Subject brightness information from the photometric element 8 is also input to the MPU 22 via the A/D converter 23 .

A lens set position table 24 made up of a ROM is connected to the MPU 22 .

Then, the MPU 22 takes in lens set position information from the lens set position table 24 in accordance with the combination of the distance measurement information and the subject brightness information.

Conceptually, as shown in FIG. 2, the lens set position table 24 stores distance measurement information (in the figure, light receiving elements AI, Az,
A's, A4, As (shown as light receiving patterns) and subject brightness information expressed in EV values are associated with the set positions of the photographing lens 2 indicated by N1 to Nlo. be. In other words, the light receiving sensor 1
There is light incident only on the light receiving element A1 of No. 4 (the distance measurement information is "rloooo"), and the subject brightness at that time is "Ev1".
8”, the lens set position information of N5 is M
It is taken into the PU22. Also, in the state shown in Figure 1, rEV
15J, lens set position information of N3 is obtained.

Figure 3 shows lens set position and subject distance (logarithmic scale)
The circle of least confusion δ that can be considered to be in focus. This is shown together with That is, the photographic lens 2 is N, ~N
,. It is possible to take 10 set positions, and at each set position, the optimum focusing position is set at a predetermined subject distance from close range to infinity, as shown in FIG.

A solid line and a broken line drawn from each lens set position indicate the increasing tendency of the circle of confusion at rEV18J and rEV8, respectively, and these are the circles of minimum confusion δ.

The distance between two points that intersect with is the subject distance range included in the depth of field.

By the way, the set position of the photographic lens 2 is basically determined in accordance with the distance measurement information, regardless of whether there is a single reflected light from the subject or a plurality of lights. The lens set position information stored in the memory is determined from distance measurement information and subject brightness information in the following manner. That is, when the EV value is large, for example rEV18J, and the maximum aperture diameter when opening and closing the program shutter is correspondingly small, the set position of the photographing lens 2 determined according to the distance measurement information is, for example, N, When , the diameter of the circle of confusion at the infinite position is small and the circle of minimum confusion δ.

This means that there is a margin (equivalent to 3 steps in terms of lens set position). However, if there is an allowance for the diameter of the circle of confusion with respect to the diameter of the circle of least confusion δ0 at the infinity position, the setting position of the photographing lens 2 is moved closer to the short distance side by this allowance, and the lens setting position is adjusted. MN6 is to be given.

Note that when the lens set position based only on the distance measurement information is N, and the subject brightness information at this time is rEV8, the lens set position N based on the distance measurement information cannot already cover the infinite position.

In such a case, the lens set position is the lens set position N based only on distance measurement information.

will be stored in the lens set position table 24.

Such final lens set position information is obtained by comparing the far point of the depth of field of the photographing lens 2, which changes depending on the subject brightness, with respect to the lens set position corresponding only to distance measurement information, and eliminating confusion at the infinity position. The diameter of the circle is the circle of least confusion δ. If there is a margin for the diameter, it can be determined in advance by shifting the set position of the photographing lens 2 toward the short distance side by the margin. By setting the lens set position information in the lens set position table 24 in advance in this way, it is possible to uniquely determine the final lens set position of the photographing lens 2 from the ranging information and subject brightness information. It is what it is. Note that instead of the infinite distance position, the diameter of the circle of confusion at a specific distance position such as a distance position on the far side (for example, 12 m) is defined as the minimum confusion circle δ. The lens set position information may be set in comparison with the diameter of the lens.

In addition, in the lens set position table 24 shown in FIG. 2, the area surrounded by a broken line indicates the area where strobe photography is performed, and in this area, in addition to the lens set position information, there is information about switching to strobe photography. information about the aperture diameter of the program shack 32 when giving a light emission trigger to the built-in strobe device 33 are also held. This aperture diameter information is determined as an aperture diameter determined by the guide number of the strobe device 33 and lens set position information (subject distance). Therefore, MPU2
2 takes in the lens set position information of this area, it automatically shifts to strobe photography, and while the program shutter 32 is being opened, the aperture is set in accordance with the lens set position information. When the value is reached, the built-in strobe device 33 emits light to illuminate the subject.

The operation of the distance measuring device configured as described above is as follows. When the shutter button 5 is pressed after confirming the subject screen through the viewfinder 3, the MPU 22 sends an activation signal to the emitter drive circuit 27 to activate the strobe light emitting tube 9 for distance measurement.
lights up. The light from the strobe light emitting tube 9 passes through the slit plate 10° projection lens 12 and is irradiated as slit light toward the subject. As shown in FIG. 1, when the main subject 18 and the secondary liquid subject 19 are within the irradiation range of the slit light, the light reflected from them enters the light receiving elements A, A2 of the light receiving sensor 14. do.

A distance measurement signal obtained by the reflected light from the object being incident on the light receiving elements AI and A2 is inputted to the MPU 22 as distance measurement information rl1000J by the distance measurement information detection circuit. At the same time, subject brightness information is input to the MPU 22 via the A/'D converter 23. If the subject brightness at this time is, for example, an EV value of "18", the MPU 22 refers to the data in the lens set position table 24 based on these data and obtains the lens set position N5. This lens set position N5 is a lens extending position that takes into account the field of view when the distance measurement information rl1000'' and the subject brightness information rEV18'' are used.

In other words, the distance measurement information rl1000J means that there is a subject in a short distance area, but rEV 18J
Since the depth of field range expands under the subject brightness of , N5 is given as the lens set position in consideration of this. When the lens set position N5 is obtained, the MPU
22 drives a motor 29 via a driver 28 to control the taking lens 2 to move out to the lens set position N5.

Note that as the motor 29, for example, a servo motor can be used. In this case, the extended position of the photographic lens 2 may be detected using a potentiometer or the like, and this may be fed to the driver 28.

When the photographic lens 2 is set at the lens set position N, the MPU 22 receives this set completion signal and operates the shutter drive circuit 30 to open and close the program shutter 32 at an aperture diameter corresponding to the EV value "18". Exposure will now take place. In this case, as shown in Figure 3,
Even at the lens set position N5, almost the entire subject distance from close to infinity can be contained within the depth of field of the photographic lens 2, so that the main subject 18. Sub-liquid photographic object 1
9 can be clearly photographed.

By the way, when the subject brightness is low, the aperture diameter of the program shutter 32 becomes large, and the depth of field of the photographic lens 2 becomes narrow accordingly. Therefore, in this case, if the lens set position for rlloooJ is set to N as described above as distance measurement information, the closest side will be out of the depth of field. Therefore, in the lens set position table 24, the distance measurement information is “110”.
00'' and the subject brightness is rEV14J, for example, the lens set position N2 is associated. This lens set position KN2 is determined as a position where the subject distance obtained from the ranging information rllooOJ can be covered within the depth of field of "rEV14".

Furthermore, if the subject is located at a far distance and, for example, "00001" is obtained as the distance measurement information, for example, the lens set position N9 is set from this distance measurement information alone. However, if the subject brightness at this time is "EV18", as is clear from FIG. 2, the photographing lens 2 is set at the lens set position N6, which is three steps closer to the short distance side. As shown in Fig. 3, this lens set position N6 is a position that can cover the infinity position within the far point of the depth of field range '5EVIBJ that is considered to be in focus when rEV18J is used. . As a result, rEV 18
It becomes possible to effectively utilize the entire distance range "5EVI8" within the depth of field of J, and the focusing range is greatly expanded. By determining the set position of the photographic lens 2 in this way, it is possible to improve the focus on the short distance side while covering infinity within the depth of field.

Note that when the subject brightness is about rEV14j, the depth of field range that can be considered to be in focus becomes narrower, so the number of steps to move the photographic lens 2 toward the short distance side also becomes smaller.
This is the lens set position for NIl.

Further, as is clear from the lens set position table 24 in FIG. 2, the distance measurement information used to determine the lens set position is a combination of at least two types of distance measurement signals from the short distance side.

That is, when the reflected light from the subject enters only the light receiving element A, distance measurement information of rloooo is obtained, but when the reflected light from the subject enters both the light receiving elements Ar and A2, the distance measurement information of rlloooo' is obtained. Distance information can be obtained.

For example, when light is incident on the light-receiving elements A, A, A4, distance measurement information of rlolloJ is obtained, and the lens set position N is determined for each subject brightness based on this distance measurement information. may be made to correspond.

When the subject brightness is "rEVlo", for example, roloooJ is used as the ranging information.

Even if the distance measurement signal indicating the closest object distance is common, such as rolloo, the lens set position will differ between the two. In other words, even if the subject brightness is rEVloJ, when the distance measurement information is "〇1000j", N3
The lens set position is set, and the distance measurement information is "rolloo".
When , the lens set position is N4. In this way, when two ranging signals are detected by the light receiving sensor 14, there is a high probability that one of them is based on reflected light from the main subject. Therefore, when two distance measurement signals are detected in this way, in order to cover both of them within the depth of field with as much margin as possible, the aperture diameter is set in the lens set position table while the program shank 32 is being opened. When the aperture diameter reaches the value stored in the aperture 24, the strobe device 33 is made to emit light to take a picture with the aperture substantially stopped down.

FIG. 4 shows a flowchart of another embodiment of the present invention in which the lens set position is determined by software. In the case of this embodiment, instead of the lens set position table 24 described above, distance measurement information and lens set position are
An AF child table is used in which the subject brightness information obtained from the photometric element 8 corresponds to the depth of field ~18-S of the photographing lens. This is obtained by associating each optimum lens set position with the light receiving pattern of the AF element table light receiving elements A1 to A. Furthermore, the aperture diameter of the EE child table and program shutter 32 is determined by the output from the photometric element 8, and the depth of field S corresponds to the aperture diameter determined in this way. It can be obtained by associating S.

As is clear from the flowchart, the light receiving element A
When the distance measurement information is obtained from the light reception patterns 1 to A, the AF element table is referred to and the initial lens set position Na is determined regardless of the subject brightness. For the lens initial set position N1 obtained in this way, the depth of field S obtained by referring to the EE table is taken into consideration, and the circle of confusion δ at the infinite position is the minimum circle of confusion δ shown in FIG. It is determined whether the depth of field S at the initial lens set position N is beyond the infinity position.

When the result of this determination is rYEsJ, priority is given to the distance measurement information, this initial lens setting position Ni is determined as the final lens setting position, and the photographing lens is set at that position.

On the other hand, when the result of the determination is "NO", it means that there is a margin due to the depth of field S at the infinity position if the initial lens set position N is maintained. Such a state occurs when the subject brightness is bright and the depth of field S is deep. In this case, the lens set position N is shifted one step toward the short distance side. Then, the depth of field S is taken into consideration at the lens set position Ni-1 shifted to the near distance side, and it is determined whether the infinity position is outside the depth of field S. If so, the same process is repeated.

In the process of repeating the above process, the circle of confusion δ at the infinite position becomes the minimum circle of confusion δ. When it exceeds the current lens center position N. is shifted one step toward the far distance side, and the final lens center position is determined. As a result, the final lens set position is determined to be the closest position that can include infinity within the depth of field S. Of course, processing may be performed based on a predetermined long-distance position instead of the infinite position.
4. The illustrated embodiment has been described above, but the configuration for obtaining the distance measurement signal is not limited to the above-mentioned active method using slit light projection, but also other methods such as an active distance measurement method using spot light projection. , can be used for various things.

[Effects of the Invention] As described above, according to the distance measuring device of the present invention, when determining the set position of the photographing lens in consideration of distance measurement information and brightness information, If the distance position covers the far point side of the depth of field of the photographic lens, move the photographing lens to infinity or within a range where the predetermined distance position does not deviate from the far point of the depth of field of the photographic lens. I try to shift it to the short distance side and set it.

Therefore, as well as the distance position corresponding to the distance measurement information,
It is possible to expand the focusing range to the short distance side while also covering the long distance side, and it is possible to bring near and far objects in addition to the main subject into the focus range with a high probability.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a distance measuring device according to the present invention. FIG. 2 is a conceptual diagram of a lens set position table used in the present invention. FIG. 3 is a graph showing the relationship between the lens set position and the circle of least confusion for rEV8J and "E18". FIG. 4 is a flowchart in another embodiment of the present invention in which the lens set position is determined while changing it step by step. FIG. 5 is a front view of a camera using the present invention. 2... Photographing lens 6... Light emitter 7... Light receiving unit 14... Light receiving sensors A1 to A5... Light receiving element 20... Ranging information detection circuit 22... MPU 24... Lens set position table .

Claims (2)

[Claims] (1) A light receiving sensor that receives reflected light from a subject and outputs distance measurement information corresponding to the subject distance, a photometer that outputs subject brightness information, and based on the distance measurement information and the output from the photometer, When infinity or a predetermined distance position on the far side is included within the depth of field of the photographing lens with a margin, infinity or the predetermined distance position does not deviate from the far point of the depth of field of the photographing lens. and lens set position determining means for setting the set position of the photographing lens to a position closer to the short distance side. (2) The camera according to claim 1, wherein the lens set position determining means is a data table that associates lens set positions with combinations of ranging information and subject brightness information. distance measuring device.