JP3283058B2 - Camera ranging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for a camera, and more particularly, to a finder optical system for observing a subject through an optical path different from a photographic optical system, and to the subject via an optical path different from the photographic optical system. And a distance measuring optical system for detecting the distance by a triangular distance measuring method.

[0002]

2. Description of the Related Art A distance measuring method for a camera includes a passive method of measuring a distance based on luminance information of a subject and a method of emitting a signal, for example, infrared light from the camera toward the subject, and receiving reflected light from the subject. And an active method for distance measurement. This active type is widely used in so-called compact cameras because its components are inexpensive and simple in construction. However, the active type has a projection lens of a distance measuring optical system for projecting light for distance measurement, and a finder optical system. If there is a difference in position between the system and the objective lens, parallax occurs between the actual ranging point and the ranging frame in the finder. Therefore, attempts to project light for distance measurement using an objective lens of a finder optical system have been made, for example, in JP-A-57-64217 and JP-A-Hei.
No. 29723.

[0003] This utilizes the fact that infrared light is used as the light for distance measurement, and uses a cold mirror which has a temporality such that infrared light is transmitted and visible light required for a finder is reflected. Has been achieved. That is, as shown in FIG. 13, when visible light from the subject 104 enters the viewfinder / light projection lens 1a, it is reflected by the cold mirror 8 toward the viewfinder objective lens 1b to form an intermediate image near the field frame 16. I do. Further, the intermediate image is guided to the photographer's eye 10 through the prism 7 and the eyepiece 15 for turning the intermediate image into an erect image and observed as a finder image.

On the other hand, infrared light for distance measurement is emitted from the IRED 4, passes through the light projecting lens 1c, the cold mirror 8, and the finder / light projecting lens 1a, and is emitted as a substantially parallel light beam toward the subject. Accordingly, the finder incident optical axis and the light emission optical axis coincide with each other, and no parallax occurs between the distance measuring frame in the finder and the actual distance measuring point.

[0005]

However, even a viewfinder / projection optical system utilizing the above-mentioned cold mirror is not a single-lens reflex camera, so the parallax between the viewfinder optical system and the photographing optical system of the camera is required. Can not be lost. This will be described below with reference to FIG.

Reference numerals 12 and 13 denote photographing lenses of a photographing optical system, and 14 denotes a film surface. The range that can be photographed at the subject distance L3 is shown as 17, and the range that can be photographed at the subject distance L4 is shown as 18.

On the other hand, reference numeral 10 denotes a photographer's eye, and reference numerals 1 and 15 denote an objective lens and an eyepiece of a finder optical system. In a single-lens reflex camera, parallax basically does not occur because the lens 12 of the photographing optical system and the objective lens 1 of the finder optical system are basically the same, but in a compact camera in which the positions 1 and 12 are different, the parallax is It always occurs at some distance.

For example, as shown in the figure, if the design is performed with no parallax at the subject distance L3, only the portion from the left when viewed through the viewfinder at the subject distance L4 cannot actually be photographed. Accordingly, in the viewfinder of the conventional compact camera, as shown in FIG. 15, a display indicating a short-range photographable range as indicated by 19 is displayed inside the photographable range 16. In the drawing, reference numeral 20 denotes a distance measurement frame.

That is, when a main subject is photographed in a short distance, for example, in a macro area, the distance measurement frame is located at a position considerably right of the actual photographing range.

[0010] With such a display, when the photographer tries to take a picture at once, he or she tends to take a failed photograph.
For example, when the main subject flower is aligned with the distance measurement frame 20, the main subject flower is shifted laterally as shown in FIG. 16. On the other hand, as shown in FIG. 17, the main subject flower is aligned with the parallax display. However, the flowers are out of focus, and the back wall is in focus, resulting in a failed photo.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a camera having a distance measuring device for projecting distance measuring light by sharing a part of an optical path of a finder optical system with a simple configuration. It is an object of the present invention to provide a camera distance measuring device that enables distance measurement to a closest side.

[0012]

A distance measuring apparatus for a camera according to the present invention includes a finder optical system for observing a subject through an optical path different from a photographic optical system, and a finder optical system through an optical path different from the photographic optical system. A distance measuring optical system for detecting the distance to the subject by triangulation, wherein the distance measuring optical system projects distance measuring light on the optical axis of the finder optical system. The first optical path for detecting the distance to the subject and the distance measuring light projected outside the optical axis of the viewfinder optical system and at the center of a short-range shooting range displayed on the viewfinder. And a second optical path for detecting the distance to the subject.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Prior to describing the embodiments of the present invention, the basic concept of the present invention will be described with reference to FIGS. SUMMARY OF THE INVENTION The present invention provides a distance measuring apparatus capable of taking a photograph without failure even in close-up photographing, by utilizing the property of a cold mirror used for finder projection AF.

The basic concept will be described with reference to FIG. Reference numerals 1a and 1c denote light projecting lenses, 4 denotes an infrared light emitting diode (hereinafter referred to as IRED), 3 denotes a light receiving lens,
Reference numeral 5 denotes a known light position detecting element (hereinafter, abbreviated as PSD), and reference numeral 6 denotes a dedicated IC (AFIC) for calculating a subject distance from an output signal of the PSD. ing.

First, the relationship between the output current of the PSD 5 and the subject distance L will be described based on the above components. Floodlight lens 1
The distance between the light receiving lens 3 and the light receiving lens 3 is defined as a base length S.
Assuming that the interval between the image signal and the PSD 5 is f as shown in the figure, the relationship between the incident position x of the reflected signal light and the subject distance L is expressed by the following equation (1).

X = S · f / L (1) Assuming that the distance from the end of the PSD 5 on the IRED side to the optical axis of the light receiving lens 3 is a as shown in the figure, and the total length of the PSD 5 is t, PSD From the characteristics of (1), i1 = {(a + x) / t} (i1 + i2) (2) Therefore, the reciprocal 1 / L of the subject distance L is

(Equation 1) More required. Here, since t, a, s, and f are constants, the AFIC 6 needs a function capable of calculating i1 / (i1 + i2).

As for the distance measurement limit of the PSD 5, as is apparent from the figure, when x reaches the end of the PSD 5, distance measurement cannot be performed any further. Therefore, in the distance measuring optical system including the light projecting lenses 1a and 1c and the light receiving lens 3 in the drawing, the distance cannot be measured beyond the subject distance L1. Therefore, if the base length S is defined as a first base length S1 and the distance is measured with a second base length S2 which is different from the first base length S1, in this case, the subject distance which can be measured is as follows. It will approach L2. Therefore, if the light is projected by the projection lens 2, the distance can be measured up to the macro range.

In this case, if the light projecting lens 1a is located at the position of the light projecting lens 2 from the beginning, the macro area becomes stronger even without the lens 2, but the distance measuring accuracy at a long distance deteriorates. This point is also evident from the above equation (1). Since x increases as the base line length S increases, the PSD can easily detect it.

Next, the finder optical system will be described.
In this case, the light projecting lens 1a in the distance measuring optical system functions as a light receiving lens for entering visible light from a subject in the finder optical system. Reference numeral 8 denotes a cold mirror that transmits the infrared light from the IRED 4 and reflects the visible light incident from the lens 1a. The reflecting function of the mirror 8 and the prism 7 guide the subject image to the finder eyepiece lens 15.

In other words, a part of the optical path of the finder optical system is common to the first optical path for measuring the distance at the first base line length S1 of the distance measuring optical system. Thus, the photographer 10 can observe the subject image via the projection lens 1a of the distance measuring optical system without causing parallax as in the case where the finder optical system and the distance measuring optical system are separately provided.

Incidentally, the cold mirror 8 does not actually have an infrared transmittance of 100%,
20 to 30% of the infrared light emitted from the ED 4 is reflected in the direction of the mirror 9 and is lost. By effectively utilizing the infrared reflected light, the light is projected by the mirror 9 through the light projecting lens 2 as light for macro range finding. The projection path of the light for distance measurement in this case is
As shown by the broken line in the figure, the second optical path is not common to the optical path of the finder optical system, and is used for distance measurement at a second base line length S2 different from the first base line length S1. .

By providing the second optical path that is not common to the optical path of the finder optical system by effectively utilizing the reflection loss light of the distance measuring light emitted from the IRED 4, a part of the optical path of the finder optical system is provided. The basic concept of the present invention is to extend the distance measurement limit on the closest side to the macro area in a camera having a first optical path that uses the same optical path.

FIG. 2 is an external view of a camera equipped with the distance measuring optical system of the present invention. The lenses 1a, 2 and 3 are arranged on the front surface of the body 11 above the taking lens 12.
As shown in FIG. 3, the macro distance measuring optical system is designed so that the distance measuring light can be projected to the center of the photographing range 18 in the macro area.

Therefore, as shown in FIG. 4, in addition to the conventional finder display, the macro-based distance measuring frame 20 is correctly displayed at the center of the shooting angle of view in the macro area. If you aim at the subject at the point, you can take pictures without failure.

Next, an embodiment of the present invention will be described. FIG. 5 is an external perspective view of a camera to which one embodiment of the present invention is applied. In the distance measuring apparatus of the present invention, two distance measuring lights passing through the first and second optical paths are projected at the same time. Therefore, it is necessary to eliminate crosstalk between these distance measuring lights. So Figure 5
As shown in FIG. 2, two PSDs are used, and the first PSD 5a receives the light for distance measurement by the first optical path shown by the solid line, and the second PSD 5b receives the light for distance measurement by the second optical path shown by the broken line. I do. Therefore, by using a prism 9b shown in FIG. 6 instead of the mirror 9 in FIG.
The light projecting lens 2 is disposed so as to extend in the vertical direction from the base line length direction connecting the points a and 3, and the distance measuring lights are separated in position by separating the light on the PSD side. The selection of each PSD output is performed by the CPU as described later with reference to FIGS.

FIG. 7 shows the first and second PSDs 5a and 5a.
b, a block diagram of a distance measurement system having
1, 39 and 40 are preamplifiers which absorb the current output of the PSD with low input impedance and amplify the current.
Is a compression diode. The output of the preamplifier flows into the compression diode. If these outputs are I1 and I2, the differential circuits 36 and 3 via the buffers 34 and 35, respectively.
The currents I3 and I4 flowing through 7 become I3 + I4 = I0 (4). Here, I0: the current value of the current source 38. Therefore, VTln (I1 / I2) = VTln (I3 / I4) (5) Here, from the relationship of VT; thermal voltage, (I1 / I2) = (I3 / I4) = I3 / (I0-I3) I1 (I0-I3) = I2.I3 I3 (I1 + I2) = I0. = I0.I1 / (I1 + I2) (6) These I1 and I2 are the values of i in the above equation (3).
1 and i2 are amplified.

(Equation 2) I can write

Therefore, the integrating capacitor 43

(Equation 3) Is integrated. Here, CINT is the capacitance value of the integration capacitor, and tINT is the integration time, which is the on-time of the current source 38 synchronized with the light emission of the IRED.

The CPU 42 inputs VOUT through the A / D converter 44, and obtains VOUT from the above equations (8) and (3).

(Equation 4) Is calculated to obtain the focus position. Note that CP
The U 42 controls the light emission of the IRED 4 via the other driver 41. Also, preamplifiers 30, 31, 39, 40
Is selected under the control of the CPU 42, whereby the PSDs 5a and 5b are selected.

FIG. 8 is a flowchart of the present embodiment on the premise of such a circuit. When this flow starts, in step 1, the CPU 42 sets the preamplifier 39,
40 is selected to start distance measurement by the PSD 5b. That is, when the IRED 4 emits light, it receives only light rays for short distance measurement. This distance measurement result Lb is a predetermined distance L0 (for example, 1
If the distance is greater than m) (step 2), the process proceeds to step 3, and distance measurement is performed by the PSD 5a having a larger amount of light and a higher resolution.

If Lb is closer than L0 in the above step 2,
The process proceeds to step 6 via step 4, and Lb is focused. On the other hand, from step 3
When the process proceeds to step 5, in step 6, La is focused. This focusing operation is performed under the control of the CPU 42 via the focusing means 45 shown in FIG. 7 which includes a motor and an encoder.

Next, the structure of the light projecting lens 2 will be described in more detail. As shown in FIG. 1, the infrared light emitted from the IRED 4 passes through the light projecting lens 1c, and about 80% of the light amount is transmitted by the cold mirror 8 to the finder / light projecting lens 1a side and projected toward the subject. Is done.

On the other hand, after about 20% of the light quantity is reflected by the mirror 8, it is further reflected by the mirror 9 toward the subject.
The light projecting lens 2 projects a substantially parallel light beam to the subject. This light projecting lens 2 may be the same as the finder / light projecting lens 1a at a position conjugate to the light projecting lens 1c, but is set for a long distance as shown in FIG. In some cases, the size of the projected light beam 101 is larger than that of the subject 102 for macro shooting, and accurate distance measurement cannot be performed.

Therefore, as shown in FIG. 9B, the light projecting lens 2 is set so that the combined focal length of the light projecting lenses 2 and 1c is longer than the combined focal length of the light projecting lenses 1a and 1c. It is desirable that the size of the projected light beam 103 be smaller than that of the subject 102.

FIG. 10 is a perspective view showing a case where a common light projecting lens is used. This will be described below as a modification of this embodiment. This is to guide the infrared light component reflected by the cold mirror 8 to the light projecting lens 1a by placing a prism such as 9c at the position of the mirror 9 in FIG.

As shown in FIG. 11, the prism 9c has three reflecting surfaces, and is formed by combining two triangular prisms. As a result, the light reflected by the cold mirror 8 can be returned below the cold mirror 8 and output in a direction substantially aligned with the optical axis of the lens 1c. Therefore, as shown in FIG. 12, it may be considered in the same manner as a light projecting system having two IREDs 4, 4b.

In this case as well, the light receiving side has two PSDs, which may be switched to separate the two light sources according to the incident angle.

According to the above modification, the light projecting lens 2 becomes unnecessary.

According to the above embodiment and the modification, [1] parallax between the photographing optical system and the distance measuring frame can be reduced in a wide range. [2] The range that can be measured in the macro range can be widened while ensuring long-distance ranging accuracy.

[0039]

As described above, according to the present invention, the first optical path for projecting the distance measuring light on the optical axis of the finder optical system and detecting the distance to the subject is provided. A second optical path for projecting light for distance measurement to the center of a short-range shooting range displayed on the finder, which is outside the optical axis of the finder optical system, and for detecting the distance to the subject. Since the parallax is provided, parallax between the photographing optical system and the distance measuring optical system can be reduced, and a remarkable effect that accurate distance measurement on the close side becomes possible with a simple configuration is exhibited.

[Brief description of the drawings]

FIG. 1 is an optical layout diagram illustrating a basic concept of the present invention.

FIG. 2 is an external perspective view of a camera equipped with the distance measuring device of the present invention.

FIG. 3 is a view for explaining a relationship between a shooting range of a macro area and light for macro distance measurement in the camera shown in FIG. 2;

FIG. 4 is a view for explaining a finder display in FIG. 3;

FIG. 5 is an external perspective view of a camera to which one embodiment of the present invention is applied.

FIG. 6 is a perspective view of the prism in FIG. 5;

FIG. 7 is a block diagram of a camera distance measuring apparatus according to an embodiment of the present invention.

FIG. 8 is a flowchart of the embodiment.

9A and 9B are views for explaining distance measuring spot light from a light projecting lens arranged at a second base line distance, and FIG. 9A is a view showing the light projecting lens arranged at a first base line distance. FIG. 7B is a diagram illustrating a case where the optical lens is placed at a position conjugate with the optical lens, and FIG.

FIG. 10 is an optical arrangement diagram of a light projecting system in which a light projecting lens of a distance measuring optical system is shared in a modification of the embodiment.

FIG. 11 is a perspective view of the prism shown in FIG. 10;

FIG. 12 is an optical arrangement diagram in which the light projecting system of FIG. 10 is replaced with a system having two IREDs.

FIG. 13 is an optical arrangement diagram of a main part of a finder optical system and a distance measuring optical system in a conventional camera distance measuring device that projects distance measuring light using an objective lens of the finder optical system.

FIG. 14 is a diagram illustrating parallax between a finder optical system and a photographing optical system in the conventional camera distance measuring apparatus shown in FIG.

FIG. 15 is a diagram illustrating a viewfinder field of view of a conventional compact camera.

FIG. 16 is a diagram showing an example of a photograph taken with a flower serving as a main subject aligned with a distance measurement frame in the viewfinder visual field shown in FIG. 15;

FIG. 17 is a diagram showing an example of a photograph taken by combining a flower as a main subject with parallax display in the viewfinder visual field shown in FIG. 15;

[Explanation of symbols]

1a: finder / light projecting lens (finder optical system, distance measuring optical system) 1b: objective lens (finder optical system) 1c: light projecting lens (distance measuring optical system) 2: light projecting lens (distance measuring optical system) 3 ... Receiving lens (distance measuring optical system) 4. IRED (distance measuring optical system) 5, 5a, 5b PSD (distance measuring optical system) 7. Prism (finder optical system) 8. Cold mirror (distance measuring optical system, finder) 9) Reflection mirror (ranging optical system) 9b, 9c ... Prism (ranging optical system) 10, 104 ... Subject 12 ... Objective lens (photographing optical system) 13 ... Eyepiece lens (photographing optical system) 15 ... Eyepiece Lens (finder optical system) 16: Field of view (finder optical system) S1: First base line length S2: Second base line length

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-209424 (JP, A) JP-A-63-229439 (JP, A) JP-A-58-100840 (JP, A) 34117 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 7/32

Claims (1)

(57) [Claims] 1. A finder optical system for observing a subject via an optical path different from the photographing optical system, and a distance measuring device for detecting a distance to the subject via an optical path different from the photographing optical system by triangulation. A distance optical system, comprising: a first optical path for projecting light for distance measurement on an optical axis of the finder optical system and detecting a distance to the subject; Outside the optical axis of the finder optical system ,
A second optical path for projecting light for distance measurement to a central portion of the displayed close-up photographing range and detecting a distance to the subject, and a distance measuring apparatus for a camera.