JP3284325B2 - 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 so-called active type camera distance measuring device for projecting irradiation light onto a subject to obtain a distance signal.

[0002]

2. Description of the Related Art In a distance measuring apparatus using a triangulation method,
A method for correcting a distance detection error due to uneven reflection intensity on a subject or a shift in the center of gravity of a light-receiving spot caused when a part of a projected light beam hits an edge of the subject (hereinafter, referred to as non-uniform irradiation). For example, JP-A-63-
As disclosed in JP-A-235909 and JP-A-5-52557, a so-called trinocular system using one light projecting element and two light receiving elements is known.

[0003]

In a three-lens type active distance measuring device, two light receiving elements are arranged on both sides of one light projecting element, so that it is twice as large as a normal two-lens type distance measuring device. This is very disadvantageous in terms of space when it is mounted on a compact camera that requires a small size. The object of the present invention is to provide a camera distance measuring apparatus having the same size as the twin-lens system and the same effect as the three-lens system.

[0004]

In order to solve the above-mentioned problems, in a camera distance measuring apparatus according to the present invention, a first light projecting means for projecting irradiation light to an object and a light projecting device are provided. A first light receiving unit that is arranged at a fixed base line distance and receives light reflected by the subject from irradiation light of the first light projecting unit;
A second light projecting means disposed near the first light receiving means for projecting light to a subject, and an irradiation light of the second light projecting means arranged near the first light projecting means; Has a second light receiving means for receiving light reflected by the object, and a distance signal generating means for generating a distance signal to the object based on output signals of the first and second light receiving means.

Further, the distance signal generating means obtains a distance signal by averaging output signals of the first light receiving means and the second light receiving means.

[0006]

In an active type two-lens distance measuring device, a light projecting element is arranged at a focal position of each lens, and a one-dimensional semiconductor light receiving element is arranged near the outside of the lens. Each light receiving element receives the projected light projected through another lens, and outputs a current corresponding to the incident position to each light receiving circuit. The arithmetic circuit obtains distance information from the output of each light receiving circuit.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. Prior to the distance measurement operation, an arithmetic circuit (hereinafter referred to as a CPU) 1 turns on the power of the light emitting circuit 2 and the light receiving circuits 10 and 20, and subsequently outputs a light emitting signal composed of a digital pulse train to the light emitting circuit 2. The light emitting circuit 2 receives two near-infrared light emitting elements (hereinafter referred to as IRED) 1 according to the light emitting signal.
1 and 21 are alternately driven under predetermined conditions (for example, a cycle of 2 milliseconds and a light emission duty of 5%). IRED 11, one-dimensional semiconductor light receiving element (hereinafter referred to as PSD) 13, IR
It is most desirable that the ED 21 and the PSD 23 each have two light emitting parts molded in the same plastic package 14 as shown in FIG.
D13 may be arranged in close proximity.

The infrared light projected from the IRED 21 is collected by the lens 22 and projected on the subject 3. The light reflected by the subject 3 is collected again by the lens 12 and
An image is formed on the light beam 13 as a beam image 13a. The PSD 13 has signal light currents IN1 and I1 corresponding to the imaging position of the incident light.
Output F1. The signal light current IN1 is extracted from the stationary light current extracting circuit 15a by the stationary light current component, is logarithmically compressed by the logarithmic compression circuit 16a, is amplified by the current amplifier circuit 17a, and is input to the arithmetic unit 18. Signal light current IF1
Also the steady photocurrent extraction circuit 15b and the current amplification circuit 17
(b) Similar processing is performed in the logarithmic compression circuit 16b, and the result is input to the arithmetic unit 18. The arithmetic unit 18 outputs the signal light current IN1
And IF1 to output the voltage V1 shown in equation (1) to the averaging circuit 4. Here, Vc is a predetermined voltage.

V1 = Vc · IF1 / (IN1 + IF1) (1) As shown in FIG. 5, the voltage V1 is L, the length of the PSD in the base line length direction, and from one end in the adjacent PSD direction to the center of the beam image. Assuming that the distance is X1 and the current supplied from the terminal TC1 is the current I1, it is expressed by the following equation (2). Here, c is a proportional constant having a dimension of electric resistance.

V1 = c · (X1 / L) · I1 (2) The above is the case where the infrared light is projected from the IRED 21, but the case where the infrared light is projected from the IRED 11 is exactly the same.
The image is formed by the PSD 23 as a beam image 23a, and is output as the signal light current IN2 and IF2.
2, the stationary photocurrent component is extracted by a stationary photocurrent extraction circuit 25a, logarithmically compressed by a logarithmic compression circuit 26a, amplified by a current amplification circuit 27a, and input to an arithmetic unit 28. The signal light current IF2 is also a steady light current extraction circuit 25.
b, the same process is performed in the current amplification circuit 27b and the logarithmic compression circuit 26b, and the result is input to the arithmetic unit 28. Arithmetic unit 2
8 outputs to the averaging circuit 4 a voltage V2 represented by Expression (3) from the signal light currents IN2 and IF2.

V2 = Vc · IF2 / (IN2 + IF2) (3) Similarly to the voltage V1, the voltage V2 is the distance from one end in the adjacent PSD direction to the center of the beam image, and the current supplied from the terminal TC2 is the current. I2 is represented by the following equation (4).

V2 = c · (X2 / L) · I2 (4) The averaging circuit 4 is a circuit for averaging the voltages V1 and V2 as in equation (5).

V0 = (V1 + V2) / 2 (5) The light projecting circuit 2 drives the IRED 11 and the IRED 21 alternately, and each time the CPU 1 operates the A / D converter (hereinafter referred to as an AD converter).
At C5, the output voltage V0 of the averaging circuit 4 is detected. From the distance table in the memory 1a uniquely determined by the voltage V0, the distance D to the subject can be obtained. If non-uniform irradiation has not occurred, the voltages V1 and V2 are substantially the same voltage, and the average voltage V0 may also be considered to be substantially equal to the voltages V1 and V2.

Here, the case where uneven irradiation has occurred will be described with reference to FIGS. 4 and 5
The same components as those described above are denoted by the same reference numerals. In FIG. 6, IRE
The projection light from D is radiated only to a part of the person who is the subject, so that the reflected light from the subject is also only a part of the arc. Hereinafter, this state is referred to as “beam missing”. When the beam is chipped, the image on the PSD also becomes a part of the arc, and the center of gravity of the light shifts to cause erroneous distance measurement. FIG. 7 is an enlarged view of PSD13 and PSD23 in FIG.
It can be seen that the beam is shifted to the far side by the value Δx1 in the PSD 13 and to the near side by the value Δx2 in the PSD 23. That is, Expression (6) and Expression (7) hold.

V1 = c · (X−ΔX1) / L · I1 (6) V2 = c · (X + ΔX2) / L · I2 (7) A voltage V0 obtained by averaging these is given by equation (8).

V0 = c · ((X−ΔX1) · I1 + (X + ΔX2) · I2) / L (8) Here, when the subject is sufficiently large with respect to the base line length B,
The beam irradiation amount to the subject is approximately equal, and PSD13
Thus, an image having substantially the same intensity and substantially the same shape is drawn on the PSD 23. Therefore, the value Δx1 is substantially equal to the value Δx2, and the currents I1 and I2 are also substantially equal in that the light intensity is substantially the same. From the above, the value Δ of equation (8)
Since the term of x1 and the value Δx2 are canceled out, Expression (8) is almost equal to Expression (5), and it can be seen that the influence of the beam missing disappears.

As described above, the range finder for a camera according to the present invention comprises two pairs of light emitting and receiving elements having two optical systems each including one light emitting element and one light receiving element. When the light emitting element of one optical system is turned on, the light receiving element of the other optical system is driven to be turned off. By driving the two light emitting elements alternately a predetermined number of times and causing the averaging circuit 4 to perform the calculation of the equation (5), the influence of the beam missing can be removed, and the distance D to the subject can be correctly obtained. The CPU 1 drives the motor 6 according to the distance D to move the photographing lens barrel 7 to an appropriate position.

In this example, only the case where the beam is missing is shown. However, it is obvious that the influence can be similarly reduced in the case of general non-uniform irradiation.

Further, in this embodiment, the photographer cannot know the occurrence of the non-uniform irradiation. However, a notifying means such as a buzzer or a lamp is added to notify the photographer of the occurrence of the non-uniform irradiation. Is also good.

Further, in the present embodiment, the correction of the non-uniform irradiation is always performed. However, when the influence of the non-uniform irradiation is slight, the error of the distance measurement result is increased by the error of the correction calculation. In order to avoid this, correction of the distance measurement result may be prohibited when the influence of the non-uniform irradiation is equal to or less than a predetermined value.

[0021]

According to the present invention, since the countermeasure for non-uniform irradiation is realized by the two-lens system, it is not necessary to increase the base line length unlike the three-lens system, thereby contributing to downsizing of the camera.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional example.

FIG. 3 is an example of an arrangement of a light emitting element and a light receiving element used in an embodiment of the present invention.

FIG. 4 is an explanatory diagram in a case where a beam is not chipped in the embodiment of the present invention.

FIG. 5 is an enlarged view of a light receiving element in FIG.

FIG. 6 is an explanatory diagram in a case where a beam break occurs in the embodiment of the present invention.

FIG. 7 is an enlarged view of a light receiving element in FIG.

[Explanation of symbols]

 11 IRED (first light emitting means) 13 PSD (first light receiving means) 21 IRED (second light emitting means) 23 PSD (second light receiving means) 1 CPU (distance signal generating means)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 7/32 G03B 13/36

Claims (2)

(57) [Claims] 1. A first light projecting element for projecting irradiation light to a subject, and a light projecting element disposed at a predetermined base length from the light projecting element and reflected by the first projecting element. A first light-receiving element for receiving the light, a second light-emitting element disposed near the first light-receiving element and projecting irradiation light to a subject, and a second light-emitting element near the first light-emitting element. Placed in the second
A second light receiving element for receiving the light reflected by the object from the light emitted from the light projecting element, and a distance signal generating means for generating a distance signal to the object based on the output signals of the first and second light receiving elements And a distance measuring device for a camera. 2. A distance measuring apparatus for a camera, wherein said distance signal generating means obtains a distance signal by averaging output signals of said first light receiving circuit and said second light receiving circuit.