JPS63259626A - Range finder for camera - Google Patents

Abstract

PURPOSE:To grasp a main object in a focusing range by obtaining range finding information based on at least two kinds of range finding signals on a short distance side at the time of detecting plural range finding signals and executing photographing by using an illumination means at the same time. CONSTITUTION:A range finding information detection circuit 20 outputs the range finding information from the range finding signals from a light receiving sensor 14. And also object luminance information from a photometry element 8 is inputted in a microprocessor unit 22 (MPU 22) through an A/D converter 23. At the time of detecting at least two kinds of range finding signals when it is less than a specified luminance level an object illumination means is lighted with an actuation signal supplied from a illumination signal generation means, according to which the diaphragm aperature of a photographing lens 2 is narrowed and the depth of a field to be photographed is expanded so as to cover the respective distance of object corresponding to two kinds of range finding signals in the depth. Thus, the object can be grasped in the focusing area at 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 set mechanism moves and controls the photographic lens to a position corresponding to the distance measurement signal thus detected.

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 ranging signals are obtained from such a general color photographing screen, and it becomes impossible to unambiguously determine the set position of the I lens.

From this point of view, when multiple distance measurement signals are detected, a short distance priority method is used in which the one with the closest subject distance is prioritized, and
As is known from each publication of No. 46029, it is important to not only give priority to short distances (but also consider the depth of field of the photographing lens and include the nearest object distance in the near point of the depth of field). There is a method of setting a photographic lens in a certain position.

[Problem that the invention seeks to solve]

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. In addition, in the methods described in the above publications, when a main subject at a close distance is photographed together with a distant view, a focusable area is created on the far side so that the main subject is included in the near point of the depth of field. Since it is intended to be expanded, if the distance measurement signal from a short distance is from the main subject, the depiction of the foreground will deteriorate and only the depiction of the background will be improved. This is not very desirable as a photographic image. In addition, as the subject brightness decreases, the aperture of the photographic lens becomes larger and the depth of field becomes narrower.If multiple ranging signals are detected, the subject distance corresponding to these ranging signals becomes smaller. It becomes impossible to cover each of them within the depth of field.

The present invention has been made in view of the shortcomings of the conventional technology, and it is possible to capture the main subject within the focusing range with a high probability even when a plurality of distance measurement signals are output from the distance measurement light receiving element. The purpose of the present invention is to provide a distance measuring device for a camera that can perform the following functions.

[Means for solving problems]

To achieve the above object, when a plurality of distance measurement signals corresponding to different subject distances are output from a distance measurement light receiving element, at least two types of distance measurement signals on the short distance side among these distance measurement signals are output. A distance measurement information detection means for sampling the distance measurement signal of lens position determining means for determining the set position of the lens; and object illumination means built into or attached to the camera for detecting that the at least two types of distance measurement signals are obtained when the subject brightness is below a predetermined level. A lighting signal generating means for supplying an activation signal to the lighting device is used.

[Effect]

According to the above configuration, when at least two types of ranging signals are detected when the brightness level is below a predetermined brightness level, the object illumination means is turned on by the actuation signal supplied from the illumination signal generation means, and the photographing lens is accordingly turned on. The aperture aperture is narrowed and the depth of field is expanded to cover each of the subject distances corresponding to the two types of distance measurement signals within the depth range, and which of the two types of distance measurement signals is from the main subject. This makes it possible to capture objects in the in-focus area with a high probability.

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 built-in strobe are arranged at the top. There is.

Further, a shutter button 5 is provided on the top surface of the camera body 1. The light emitting unit 6 of the distance measuring device is placed between the photographing lens 2 above and below. The light receiving sections 7 are arranged respectively, and these are separated by the base line 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 diameter of the program shutter, that is, the F-number of the photographic lens, which will allow appropriate 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 10 that emits distance measuring light;
It consists of a slit plate 11 that shapes the light from the strobe light emitting tube 10 into a slit shape, an infrared filter L2 that transmits only near-infrared light, and a cylindrical lens 13. The optical axis 13a of this cylindrical lens 13 is connected to the photographing lens 2.
It is parallel to the optical axis 2a of. As a result, the light projecting section 6
The camera now projects a horizontally wide slit light in the near-infrared region 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 13a of the cylindrical lens 13.

The light receiving sensor 14 arranged on the focal plane of the lens 15 is
Five light receiving elements A arranged along the base line length,
A,,A3. It consists of A,,A,. 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 I8 is at the position shown in the figure, the light reflected by it enters the light receiving element A7 in the light receiving sensor 14, and in addition to this main subject I8, there is a copper subject 1.
9, the reflected light from this copper object 19 enters the light receiving element A3.

A distance measurement information detection circuit 20 is connected to the light receiving sensor 14 . This ranging information detection circuit 20 includes a light receiving sensor 1
The distance measurement information is output from the distance measurement signal from 4, that is, the light incident signal to the light receiving elements A1 to A. For example, as mentioned above, if a copper subject is also in the slit light irradiation area N in addition to the main subject I8, distance measurement information of rollooJ is obtained from the light incident signal to the light receiving elements Ax and A3, and this is sent to the microprocessor. It outputs to the unit 22 (hereinafter referred to as MPU 22). Furthermore, subject brightness information from the photometric element 8 is also input to the MPU 22 via the A/D converter 23 .

The MPU 22 is connected to a lens set position table 24 and an EE child table 5, which are configured by ROM, as well as a built-in strobe device 33. The lens set position table 24 associates the combination of the distance measurement information and the brightness information with lens set position data divided into 10 stages from close distance to infinity. Based on the obtained data, the motor 29 is driven via the driver 28 to move the photographing lens 2 to a position corresponding to the distance measurement information.

In addition, the EE child table 5 associates the subject brightness information with the opening/closing time of the program shutter 32, and the MPU
22 refers to this EE child table 5 and controls the operation of the shutter drive circuit 30.

Note that when the subject brightness information is below rEV8J, the EE child table 5 sends a signal for performing strobe photography to the MPU 22, and the built-in strobe device 33 is activated when the program shutter 32 is activated.

During this strobe photography, based on the relationship between the lens set position information and the guide number of the built-in strobe, a light emission trigger is given to the built-in strobe device 33 when the program shutter 32 reaches a predetermined aperture diameter.

Conceptually, the lens set position table 24, as shown in FIG.
, As, Aa, As) and object brightness information expressed in EV value, N, to N,. This shows the correspondence between the set positions of the photographic lens 2 shown in , and in addition to cases in which light is incident on only one of the light receiving elements A+-As of the light receiving sensor 14, two adjacent light receiving elements on the short distance side The lens set position is also associated with the case where there is light incidence.

For example, when light is incident on the light receiving element A (the distance measurement information is '100OOJ), the subject brightness at that time is r.
When EVlB, the lens set position information of N is taken into the MPU 22. Also, as shown in Figure 1, light is incident on the light receiving elements A, A3 (the distance measurement information is rol
loo”), the subject brightness information at that time is rEVlB,
When this is the case, the lens set position information of Nb is obtained.

FIG. 3 shows the relationship between lens set position information and subject distance (logarithmic scale) together with the circle of least confusion δ0 that can be considered to be in focus. That is, the photographing lens 2 is N1
~N. As shown in FIG.
to is the optimum focusing position. And N, illustrated in the same figure.

The dashed-dotted lines drawn from the lens set positions of Ns and Nq indicate the tendency of the circle of confusion to increase when the lowest subject brightness is rEV8j, which is performed with a normal EE camera without using a strobe, and these lines are the circle of least confusion δ. . Between the two points that intersect with
The depth of field for rEV8J is S8.

Therefore, the subject brightness is at the lower limit of the EE interlocking range,
Even when the aperture diameter of the program shutter 32 becomes the largest, the circle of least confusion δ remains the same. When taking this into consideration, even if the lens set position is set in stages, the subject distance L+-L+o
It is possible to focus on all subject distances between Of course, as the subject brightness increases, the E
Since the maximum aperture diameter of the program shutter during Eli shadow is small, that is, the photograph is taken with a small aperture, the depth of field at each lens set position can be widened.

The lens set position table 24 is created taking such depth of field characteristics into consideration.

That is, when the subject brightness is high and the depth of field is wide, the photographing lens 2 is not set at the lens set position N even when the distance measurement information is "rloooO". For example, when the brightness information is rEV18, the distance measurement information is r100.
When 00J is detected, lens set position N5 is used to cover the close range side within the depth of field while simultaneously capturing the far distance side within the depth of field as much as possible.

Also, when light is incident on two adjacent light receiving elements, especially when the luminance information is "EV8" to "rEV12",
In principle, the lens set position is selected at an intermediate position when light is incident on each light receiving element, and
At this point, you will be asked to take photos with a strobe. Note that the area surrounded by a broken line in the lens set position table 24 in FIG. 2 indicates an area where flash photography is automatically switched to. Data and aperture diameter data of the program shutter 32 when giving a light emission trigger to the built-in strobe device 33 are also held. therefore,
When the MPU 22 takes in the lens set position data of this area, it automatically shifts to strobe photography, and while the program shutter 32 is opening, the aperture becomes the value corresponding to the lens set position data. The built-in strobe device 33 emits light at the appropriate timing 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 a slit plate 10° and a cylindrical lens 12, and is irradiated as slit light toward the subject. 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 obtained by sampling at least two types of distance measurement signals from the short distance side. That is, the light receiving element A.

When the reflected light from the subject is incident only on rlo
ooo, + distance measurement information is obtained, but the main subject 18 and the open subject 19 exist at the positions shown in FIG.
Light receiving element A! , A, when the reflected light from the subject is incident on both, distance measurement information of "01100J" is obtained.

In this way, distance measurement information ro1100'' is input to the MPU 22, and object brightness information is input from the A/D converter 23. The subject brightness information at this time is, for example, the EV value "
18'', the MPU 22 refers to the data in the lens set position table 24 based on this information and obtains the lens set position N. When the lens set position N6 is obtained, the MPU 22 drives the motor 29 via the driver 28.
is driven to control the taking lens 2 to move out to the lens set position N6. 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 is detected using a potentiometer, etc.
This should be fed back to the second driver.

When the photographing lens 2 is set at the lens set position N6, upon receiving this set completion signal, the MPU 22 activates the shutter drive circuit 30, opens and closes the program shutter 32 at an aperture diameter corresponding to the EV value "18", and performs exposure. will be carried out. In this case, as shown in Figure 3,
Even with the lens set position N, it is possible to cover a wide area from subject distance L2 to Llo within the maximum depth of field of 5llll when using rEV18J.
Main subject 18. Both of the auxiliary liquid photographic objects 19 can be photographed clearly.

By the way, even if the distance measurement information is rollooJ, when the subject brightness is "E10", the lens set position WN4 is taken from the lens set position table 24. At this lens set position N4, the subject brightness information is r.
EV10. Lens set position N's corresponding to distance measurement information '0100OJ and distance measurement information r00100J
It is located midway between the lens set position N corresponding to .

Then, according to the flowchart shown in Figure 4, M
An activation signal is output from the PU 22 to the built-in strobe device 33, and the object is illuminated by the built-in strobe device 33 during photographing.

When the built-in strobe device 33 operates, the MPU 22
The program shutter 32 is opened and closed with a predetermined aperture diameter in accordance with the data taken in from the EE table 5, but during the opening, the built-in strobe device 33 emits light to illuminate the subject. As mentioned above, the light emission timing of the built-in strobe device 33 is stored in the lens set position table 24 for each lens set position (correlated with the subject distance), so strobe photography using so-called flashmatic control is possible. You will be killed.

According to such control during strobe photography, rEVlo
Since the built-in strobe device 33 fires and photographs with a smaller aperture than the maximum aperture diameter during EE exposure control under the subject brightness of J, as shown in FIG. The depth of field is determined by the lens set position N3 at rEVloJ. - Now covers the depth of field at N, and even if the reflected light from the main subject is incident on any of the light receiving elements A, A, it can now be covered within the focusing range. become.

Furthermore, as shown in the flowchart of FIG. 4, the lens set position Na fetched from the lens set position table 24 corresponds to a subject distance (a≧7) that is farther than the reach range of the strobe illumination light. or when the subject brightness is higher than rEV 13'',
Furthermore, when there is a single distance measurement signal, that is, only one of the light receiving elements A1 to A receives light, the MPU 22 does not output an activation signal to the built-in strobe device 33.

Note that when the subject brightness is less than rEV8J, it is outside the EE interlocking range, so strobe shadowing is performed regardless of distance measurement information.

Furthermore, in the state of object brightness of rEVloJ, [0
When distance measurement information for OO11J is obtained, the lens set position is set to N, and the distance measurement information rooo10. The lens set position N7 and distance measurement information roooootJ
An intermediate position N8 between the lens set position N and the lens set position N8 is not selected, and priority is given to the lens set position N on the short distance side. This is because when the subject distance becomes long, the focusing range can be expanded by giving more importance to the distance measurement signal on the short distance side than on the long distance side. When the photographic lens 2 is set to focus on a subject distance ML or beyond, no activation signal is output to the built-in strobe device 33 because this subject distance L7 is outside the range of the strobe illumination light.

The subject brightness is within the EE interlocking range, and the light receiving sensor 1
The effect when light is incident on two adjacent light receiving elements in 4 can be summarized as shown in the table below.

In this way, when the subject brightness is low even if it is within the EE interlocking range, by using the built-in strobe device 33, it is possible to take a picture with the aperture diameter of the program shutter 32 substantially narrowed down. Even if light is incident on two adjacent light-receiving elements A + "" A s, these can be reliably covered within the depth of field. Therefore, regardless of which of the reflected lights is reflected from the main subject, the image can be photographed with good focus.

By increasing the data in the lens set position table 24, the built-in strobe device can be used not only when light is incident on two adjacent light receiving elements, but also when light is incident on three or more adjacent light receiving elements. It is also possible to switch to shooting using 33. Furthermore, the lens set position determined by the lens set position table 24 covers a subject distance of, for example, 1.5 to 3 m, even considering the depth of field at that time, that is, a distance range in which the main subject has a high probability of existence. It is also very effective to switch to shooting using the built-in strobe device 33 even when the focal range cannot be completely covered.

The illustrated embodiment has been described above, but instead of using the lens set position table 24, a logical operation circuit is used to obtain distance measurement information (multi-bit binary signal) based on a combination of distance measurement signals and object brightness. It is also possible to perform calculations using the information as input and obtain the lens set position from the calculation results. Furthermore, as a configuration for obtaining ranging signals, in addition to the above-mentioned active method using slit light projection, various configurations can be used as long as they can detect ranging signals from multiple subjects at different distances. Can be done.

〔Effect of the invention〕

As described above, according to the distance measurement device of the present invention, when a plurality of distance measurement signals are detected, at least two distance measurement signals on the short distance side are detected.
Obtain distance measurement information based on the distance measurement signal of the species, and when the subject brightness at that time is below a predetermined level,
Even if the camera is within the EE interlocking range, a lighting device such as a strobe is used in conjunction with the camera to take pictures. This results in
It is now possible to take pictures with the aperture of the photographic lens or the maximum aperture of the program shutter stopped down, and in most cases it is possible to capture the main subject within the in-focus range.

[Brief explanation of drawings]

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 one 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. FIG. 4 is a flowchart showing the flow of processing according to the present invention. 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 sensor A, ~A,...Light receiving element 20...Distance information detection circuit 22...MPU 24...Lens set Position table 32...Program shutter 33...Built-in strobe device.

Claims (1)

[Claims] (1) In a distance measuring device for a camera having a light receiving element that receives reflected light from a subject and outputs a distance measurement signal corresponding to the subject distance, a luminance information detection means for detecting subject brightness, and a plurality of light receiving elements from the light receiving element. distance measurement information detection means for sampling at least two types of distance measurement signals on the short distance side and outputting the same as distance measurement information when the distance measurement signal is output; and the luminance information detection means and the distance measurement information. lens position determining means for determining the set position of the photographing lens in response to both outputs from the detecting means; detecting that the subject brightness is below a predetermined level and that the two types of distance measurement signals are obtained; 1. A distance measuring device for a camera, comprising: illumination signal generation means for outputting an activation signal to object illumination means attached to the camera.