JPS63259625A - Range finder for camera - Google Patents

Abstract

PURPOSE:To catch a main object within a focusing range at high rate by including a distance range in which the existing probability of the main object is high in the focusing range by preferring range finding information by referring to the depth of the field to be photographed according to object luminance information so as to decide the set position of a photographing lens. CONSTITUTION:A range finding information detection circuit 20 outputs range finding signal from a light receiving sensor 14 as the range finding information. And the range finding information is inputted in a microprocessor unit (MPU) 22. And the set position of the photographing lens 2 is decided by referring to a prescribed distance range besides the range finding signal and the depth of the field to be photographed of the photographing lens according to the luminance of the object. Thus, the main object can be mostly included in the focusing range if the prescribed distance range is set in 1.5-3m in which the main object exists at the highest rate statistically.

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.

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 as described above, the setting position of the photographic lens can be uniquely determined according to this distance measurement signal, but in reality, the main It is rare to have a shooting screen that only shows the subject.In general, in addition to the main subject, the shooting screen often includes a secondary object and background objects.Therefore, from such a general shooting screen, multiple Therefore, 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, 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, in addition to simply prioritizing short distances, the depth of field of the photographing lens is also taken into consideration, and the position is determined so that the closest subject distance is included in the near point of the depth of field. There is a method for setting the photographic lens.

[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 each of the above publications, when multiple distance measurement signals are detected, the one corresponding to the closest subject distance is used, and the focus area is expanded to the far distance side using this as a reference. Therefore, if the obtained distance measurement signal is from the main subject, the depiction of the foreground will deteriorate and only the depiction of the background will be improved, resulting in a photographic image. It's not very desirable.

Additionally, if the main subject is outside the distance measurement range and the distance measurement signal is detected only from the secondary liquid object, only this distance measurement signal will be used, resulting in the main subject being out of focus. The probability becomes much higher.

The present invention has been made in view of the shortcomings of the prior art, such as when multiple distance measurement signals containing noise etc. are detected, or when only the distance measurement signal from the sub-liquid object is obtained. To provide a distance measuring device for a camera that can capture a main subject within the focusing range of a photographic lens with a high probability even in the case of a shooting lens.

[Means for solving problems]

In order to achieve the above object, the present invention includes an initial position determining means for determining the initial set position of a photographing lens based on a distance measurement signal obtained from a light receiving element for distance measurement, and depth detection means for detecting the field depth;
When the photographic lens is set at the initial setting position,
When the specific distance range is not included in the depth of field, an adjustment means is provided for moving the set position of the photographing lens closer to the specific distance range from the initial set position.

[Effect]

According to the above configuration, the set position of the photographic lens can be determined without referring to the specific distance range in addition to the depth of field of the photographic lens according to the distance measurement signal and the subject brightness. Therefore, if you set this specific distance range to, for example, 1.5 to 3 meters, where the main subject exists with the highest probability statistically, it will be possible to include the main subject within the focusing range in most cases. become able to.

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

〔Example〕

In FIG. 6, which shows a camera using the present invention, a camera body 1 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.

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. The reference numeral 8 indicates a photometric element for measuring the brightness of the subject.As is well-known, the photometric output from the photometric element 8 determines the maximum aperture diameter of the program shutter that can obtain proper exposure, that is, the F value of the photographic lens. It will be done.

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 10 that shapes the light from the strobe light emitting tube 9 into a slit shape. , an infrared filter 11 that transmits only near-infrared light, and a cylindrical lens 12. The optical axis 12a of this cylindrical lens 12 is parallel to the optical axis 2a of the photographic 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 11a of the cylindrical lens 11.

Light receiving sensors 1 and 4 arranged on the focal plane of the lens 15
is n light receiving elements A arranged along the base line length.
, ~A, consists of. The light receiving sensor 14 receives the light reflected by the subject out of the slit light projected onto the subject.

For example, when the main subject 1st is at the position shown in the diagram,
Then, the light reflected thereby enters the light receiving element At in the light receiving sensor 14.

A distance measurement information detection circuit 20 is connected to the light receiving sensor 14 . This distance measurement information detection circuit 20 outputs the distance measurement signal from the light receiving sensor 4, that is, the pattern in which the reflected light from the subject is incident on the light receiving elements A, ~A, as distance measurement information. 0 For example, when light is incident only on the light receiving element Az as shown in the figure, roloo
If light is incident on both the light receiving elements A+ and A4, the distance measuring information rlooolo is output. This ranging information is then input to the microprocessor 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 includes a lens set position table 24 . An EE child table 5 and a program ROM 30 are connected. Conceptually, the lens set position table 24, as shown in FIG.
The set positions N+, Nz, Nz...N, 1 are associated with each other. Then, light is incident only on the light receiving element A I of the light receiving sensor 14 (as distance measurement information, r
loooo"), the subject brightness at that time was "EV18J
When , the lens set position information of N is
22, and even if the ranging information is the same, r
EV15. When this is the case, the lens set position information of N is taken into the MPU 22. If such a lens set position table 24 is used, even if a plurality of lights are incident on the light receiving sensor 14, the setting position of the photographic lens can be determined taking into account the distribution of these light incidences! can be determined. Note that when the lens set position surrounded by the broken line in FIG. 2 is selected, the strobe device 33 is activated and the camera is automatically switched to strobe photography.

The EE table 5 associates the aperture of the program shutter 32 with which exposure is appropriate based on the subject brightness information input from the A/D converter 23, and the EE table 5 associates the aperture of the program shutter 32 with which the exposure is appropriate based on the subject brightness information input from the A/D converter 23. The depth of field S of No. 2 is also stored in memory. The program ROM 30 also stores a program related to the photographing sequence after the shutter button 5 is pressed, as well as an algorithm for determining the set position of the photographing lens 2 from distance measurement information and subject brightness information.

FIG. 3 shows the circle of least confusion δ that allows the relationship between lens set position information and subject distance (logarithmic scale) to be regarded as in-focus. The photographic lens 2 is arranged to take a stepwise set position of N, -N, . For example, ro
If the lens set position N is set by the MPU 20 from the distance measurement information of "LOOO" and the subject brightness information of rEV18J, the depth of field for rEV18J is 5ll.
It can be seen that by l, an area beyond the range of subject distances L4 to L8 can be covered within the focusing range. Also, the fourth
In the figure, the photographing lens 2 is set at the lens set position N based on the distance measurement information of "rooloo" and the subject brightness information of "rEV14".
, shows the state when set to . According to the depth of field 314 in this case, the object paths i@L, , L are outside the focusing range. In addition, rEV8. At the subject brightness of , that is, the lowest subject brightness during normal EE photography, the depth of field of the photographing lens 2 becomes the minimum depth of field S. This depth of field S8 defines each lens center position N, to N7, which is set in stages, to a circle of least confusion δ. The width is such that it is continuous within the range of .

The distance range D4 shown in FIGS. 3 and 4 represents a distance range of 1.5 to 3.0 m in which the probability of the presence of the main subject is high. This distance range was determined based on the fact that the distance range to which the main subject belongs was distributed as shown in the table below, as a result of analyzing a large number of photographs in which the main subject was actually shaded. .

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 finder 3, the MPU 22 sends an activation signal to the projector drive circuit 27, and the distance measuring strobe light emitting tube 9 operates to emit light. The light from this strobe light tube 9 is
tryi, 10, cylindrical lens 12
The light is directed towards the subject as a ray of light. Then, as shown in FIG. 1, the reflected light from the main subject 18 enters the light receiving element A2 of the light receiving sensor 14.

When the reflected light from the subject enters the light receiving element A2 in this manner, the MPU 22 determines the set position of the photographic lens 2 according to the flowchart shown in FIG. That is, if the subject brightness detected via the A/D converter 23 is rEV18J, the MPU 22 refers to the lens set position table 24 based on the distance measurement information of "01000" and the subject brightness information of "rEV18", and sets the initial Take in the set position N. Also, the MPU 22 refers to the EE child table 5 and determines the depth of field 311 for rEV18J.
Take in +.

The initial set position Nh and depth of field 31 obtained in this way
8. Furthermore, the circle of least confusion δ. The distance range that can be considered to be in focus can be determined from the relationship.

And in this case the circle of least confusion δ. The near and far points of the following depth of field range 5lll are La, respectively.
Lbl, and partially covers the above-mentioned specific distance range on the short distance side. However, the far point of the depth of field range SI8 covers a distance range in which the main subject is almost never present when distance measurement information is taken into account.

In this state, the MPU 22 moves the set position of the photographic lens 2 closer to the short distance side, that is, closer to the distance range side one step at a time, from the initial set position N6. This process is
This process is repeated until the far point of the depth of field range S18 falls within the minimum depth of field S described above. Then, when the set position reaches N3 and the far point of the depth of field range Sll+ enters the depth of field SIl, the set position is returned by one step from there, as shown in Figure 3. The final set position N4 of the photographic lens 2 is obtained.

At this set position N4, the near and far points of the depth of field are La, Lb! Therefore, the distance range is completely covered within the focusing range, and the minimum depth of field S at the initial set position N6 is also covered.

When the set position N4 is determined in this way, the photographic lens 2 is moved to the set position N4 via the driver 2 and the motor 29.
is brought out. Photographing lens 2 is at lens set position N4
When the shutter button 5 is set, a lock mechanism (not shown) that prohibits the second step of pressing the shutter button 5 is released in response to this set completion signal. Then, when the shutter button 5 is further pressed, the MPU 22 activates the shutter drive circuit 3.
0, and the program shutter 32 is set to rEVL8J.
Exposure is performed by opening and closing with an aperture diameter corresponding to subject brightness information.

By the way, as is clear from the lens set position table 24, even if the distance measurement information is "rooloo" and the subject brightness information is rEV14J, the initial set position of the photographing lens is N as described above.

In this case, the depth of field 314 hardly covers the distance range as shown in FIG.
The MPU 22 moves the set position of the lens toward the distance range side one step at a time according to the flow shown in FIG. However, unlike when the subject brightness information is rEV18J, the set position N4 cannot cover the minimum depth of field S8 at the initial set position N, so in this case, the final set position is set as N. It can be decided. Also,
The subject brightness information is rEV8. In this case, the initial set position N is determined as the final lens set position.

In the above embodiment, the initial set position of the photographing lens is determined by referring to the lens set position table 24 from the distance measurement information, but instead of such a lens set position table 24, a logical operation circuit is used. , it is also possible to perform logical operations based on the binarized object brightness information and distance measurement information, thereby determining the initial set position of the photographic lens. Furthermore, the present invention is applicable not only to the above-mentioned active type distance measuring device using slit light projection, but also to a distance measuring device projecting a spot light toward a subject, as well as various other distance measuring devices using different methods. Can be applied. Furthermore, instead of moving the photographing lens 2 from the initial set position to the final set position one step at a time, calculations are performed in advance from the lens set position N7, minimum depth of field SR + distance range, and the final set position is calculated from the calculation result. It is also possible to determine the correct lens set position.

〔Effect of the invention〕

As explained above, according to the distance measuring device of the present invention, the setting position of the photographing lens is determined based on the depth of field based on the subject brightness information, and the probability of existence of the main subject is determined while giving priority to the distance measuring information. The set position of the photographic lens is determined so that the high distance range is included in the focusing range. Therefore, even if, for example, the distance is incorrectly measured with a secondary liquid object as the main subject, or if noise enters the distance measurement information from the main subject, the main subject can be captured within the focusing range with a fairly high probability. You will be able to do this.

[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 a lens set position table used in the present invention. FIG. 3 is a graph showing the relationship between depth of field and lens set position for rEV 18J. FIG. 4 is a graph showing the relationship between depth of field and lens set position when using rEV14J. FIG. 5 is a flowchart showing the flow of processing according to the present invention. FIG. 6 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 25...EE child table

Claims (3)

[Claims] (1) In a camera distance measuring device equipped with a light receiving element that receives reflected light from the subject and outputs a distance measurement signal corresponding to the subject distance, the depth of field is detected in accordance with the subject brightness and the shooting lens. depth detection means for determining the initial set position of the photographic lens in response to the distance measurement signal; and within the depth of field of the photographic lens at the initial set position;
When the preset specific distance range is not included,
1. A distance measuring device for a camera, comprising: adjusting means for moving a set position of a photographing lens closer to the specific distance range side from an initial set position. (2) The distance measuring device for a camera according to claim 1, wherein the specific distance range is 1.5 to 3 m. (3) A patent characterized in that the set position of the photographic lens set by the adjustment means is a position that covers the distance zone obtained from the distance measurement signal within the depth of field at this set position. A distance measuring device for a camera according to claim 2.