JP3584087B2 - Camera ranging device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a distance measuring device such as a camera, and more specifically, to a so-called active type camera that projects a spot-like light beam on a subject and receives reflected light from the subject with a position detection element to obtain distance information to the subject. It relates to a distance measuring device.
[0002]
[Prior art]
Conventionally, various so-called active type distance measuring devices using a combination of a set of a light projecting element and a light receiving element as shown in FIG. 9 have been proposed. In particular, distance measuring devices using a near-infrared light emitting element (hereinafter abbreviated as IRED) and a semiconductor position detecting element (hereinafter abbreviated as PSD) are widely used. However, when only a part of the light beam projected by the IRED is reflected by the subject (hereinafter, such a state is abbreviated as “beam missing”), the optical center of gravity of the beam image formed on the PSD moves. In some cases, correct distance information could not be obtained.
[0003]
In order to solve this "beam loss", the present applicant disclosed in Japanese Patent Application Laid-Open No. Hei 6-137861 a camera distance measuring device capable of detecting a beam loss of a three-lens system including one light projecting element and two light receiving elements. Suggested. In this camera distance measuring apparatus, the second light receiving element for detecting the beam missing is arranged at a position orthogonal to the first light receiving element, which is the light receiving element for distance measurement, with respect to the light projecting element. Try to eliminate the effects of.
[0004]
[Problems to be solved by the invention]
However, in the range finder for a camera disclosed in Japanese Patent Application Laid-Open No. 6-178661, when a subject is located at a very close distance, a beam comes off the light receiving element. Under normal control, if the output of the light receiving element is not obtained, it is determined that the subject is located at infinity, and the photographing lens is driven to infinity. Become.
[0005]
In order to avoid such a state, it is sufficient to use a longer PSD in the base line length direction. However, it is a problem that the distance measuring device becomes large and the cost increases in order to avoid such a special state. is there.
[0006]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a camera distance measuring apparatus which detects a beam loss with a simple configuration and does not largely defocus a subject located at a close distance.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in a camera distance measuring apparatus according to the present invention, a light projecting means for projecting measurement light to a subject, and the light projecting means being on the same plane orthogonal to an optical axis of the light projecting means. Means and a first light receiving means for receiving the reflected light of the measuring light from the subject, the first light receiving means being arranged at a distance from the first base line length; It receives a reflected light of the measurement light from the object, which is arranged at a vertical position and shifted by 90 ° from the light projecting means with a second base line length shorter than the first base line length. Second light receiving means, calculating means for calculating a distance from the output of the first light receiving means to a subject based on the base line length, and photographing lens control for controlling the amount of extension of the photographing lens from the output of the calculating means. Means, and wherein the calculating means comprises the first and second means. Means for calculating the subject distance from them when the output of both a predetermined level or more of the light receiving unit, and only the output of said second light receiving means in the case of a predetermined level or more is judged that the subject is close means and, and said means only the output of the first light-receiving means for determining an error in the case of more than a predetermined level, and when the output are both less than a predetermined level of said first and second light receiving means is subject there has been turned from a means to determine that what is infinity.
[0008]
Also, there is provided warning means for issuing a warning to the photographer when the calculating means determines that there is an error.
[0009]
A light projecting means for projecting measurement light to the subject; and a light projecting means arranged on the same plane orthogonal to the optical axis of the light projecting means and spaced apart from the light projecting means by a first base line length. First light receiving means for receiving the reflected light of the measurement light, and a position on the plane perpendicular to the first light receiving means and the light projecting means and shifted by 90 ° about the light projecting means; A second light receiving element that is a two-dimensional light receiving element that is disposed at a position separated by a second base line length shorter than the first base line length and receives reflected light of the measurement light from the subject; Calculating means for calculating the distance from the output of the first light receiving means to the subject based on the length; and photographing lens control means for controlling the amount of extension of the photographing lens from the output of the calculating means. in the first base length direction of the second light receiving means Only a force is assumed for calculating the object distance from the output of the second baseline length direction of the second light receiving means in the case of more than a predetermined level.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The configuration of the present invention will be described with reference to FIGS. FIG. 1 is a circuit block diagram of the present invention, FIG. 2 is a three-dimensional view of the optical system of the present invention, and FIG. 3 is a diagram showing a positional relationship of the optical system of the present invention.
[0011]
In FIG. 1, reference numeral 10 denotes an arithmetic circuit (hereinafter abbreviated as CPU), which includes a read-only memory (hereinafter abbreviated as ROM) 10a and a random access memory (hereinafter abbreviated as RAM) 10b.
[0012]
The light projecting circuit 20 includes an IRED driving circuit 21, an IRED 22 driven by the IRED driving circuit 21, and a light projecting lens 23 for condensing light emitted from the IRED 22.
[0013]
The distance detection circuit 30 includes a light receiving lens 31 for condensing light from the outside, a PSD 32 for receiving light condensed thereby, a pair of amplifiers 33 for amplifying currents output from two output terminals of the PSD 32, and 36, a pair of AGCs 34 and 37 for controlling the gains thereof, and IV converters 35 and 38 for converting the outputs of the amplifiers into current and voltage.
[0014]
The beam loss detection circuit 40 includes a light receiving lens 41 for condensing light from the outside, a PSD 42 for receiving light condensed thereby, and a pair of amplifiers 43 for amplifying currents output from two output terminals of the PSD 42. And 46, a pair of AGCs 44 and 47 for controlling their gains, and IV converters 45 and 48 for current-to-voltage conversion of the outputs of the amplifiers.
[0015]
The multiplexer 50 is connected to a contact 51 connected to the IV converter 35, a contact 52 connected to the IV converter 38, a contact 53 connected to the IV converter 45, and connected to the IV converter 48. One of the contacts 54 selected is output to the A / D converter 60. The A / D converter 60 converts the output voltage of the IV converter selected by the multiplexer 50 into a digital value and outputs the digital value to the CPU 10. The lens barrel driving device 70 drives the lens barrel 71. The LED 80 is driven by the CPU 10 to notify the photographer that the result of the distance measurement is abnormal.
[0016]
Next, the operation of FIG. 1 will be described. When the distance measurement starts, the CPU 10 outputs a light emission pulse signal to the IRED drive circuit 21, and the IRED 22 is driven according to the signal to emit light. The light that has exited the IRED 22 is condensed by the light projecting lens 23 and is projected toward the subject OBJ.
[0017]
The optical system of this embodiment has a configuration as shown in FIG. 2, and a light receiving lens 41 and a PSD 42 are added to FIG. 9 which is a conventional distance measuring device. The three lenses of the light projecting lens 23, the light receiving lens 31, and the light receiving lens 41 are on the same plane perpendicular to the optical axis of the light projected by the IRED 22, and their positional relationship is as shown in FIG. I have. Referring to FIG. 3A, the light receiving lens 31 and the light receiving lens 41 are disposed at positions shifted by 90 ° about the light projecting lens 23, and the distance between the light receiving lens 31 and the light projecting lens 23 is It is longer than the distance between the light receiving lens 41 and the light projecting lens 23. The IRED 22 is located on the optical axis rear of the light projecting lens 23, the PSD 32 is located on the optical axis rear of the light receiving lens 31, and the PSD 42 is located on the optical axis rear of the light receiving lens 41 as shown in FIG. ing.
[0018]
Part of the light reflected by the object OBJ is collected again by the light receiving lens 31 and enters the PSD 32 of the distance detection circuit 30. The PSD 32 has two outputs. One output is output to the contact 51 of the multiplexer 50 via the amplifier 33, the AGC 34 and the IV converter 35, and the other output is connected to the amplifier 36, the AGC 37 and the IV converter 38. The signal is then output to the contact 52 of the multiplexer 50. Another part of the light reflected by the object OBJ is again condensed by the light receiving lens 41 and enters the PSD 42 of the beam missing detection circuit 40. The PSD 42 has two outputs. One output is output to the contact 53 of the multiplexer 50 via the amplifier 43, the AGC 44, and the IV converter 45, and the other output is connected to the amplifier 46, the AGC 47, and the IV converter 48. After that, the signal is output to the contact 54 of the multiplexer 50. The multiplexer 50 selects one of the above four contacts according to a signal from the CPU 10 and outputs it to the A / D converter 60. The A / D converter 60 converts the input analog voltage into a digital signal and outputs the digital signal to the CPU 10. The CPU 10 processes the four input signals to the multiplexer 50 in chronological order by switching the contacts of the multiplexer 50, A / D converts each of the input signals, and stores them in the RAM 10b as distance information. When calculating the distance to the subject, the distance information in the RAM 10b is read out, a value X corresponding to the distance to the subject is calculated one by one, and this is compared with a table in the ROM 10a to calculate the distance. A drive signal is output to the lens barrel driving device 70 according to the value, and the lens barrel 71 is driven.
[0019]
Next, the operation of this circuit will be described. Prior to all operations, the CPU 10 switches an analog switch in the multiplexer 50 to the contact point 51. Next, a light emitting signal (for example, a pulse signal of 16 times at a frequency of 500 Hz and a duty ratio of 5%) is output to the light emitting circuit 20, and the IRED 22 is driven accordingly. The light projected from the IRED 22 is reflected by the object OBJ, and a part of the reflected light is collected by the light receiving lens 31 and enters the PSD 32. The photocurrent output from the PSD 32 is converted into a voltage by the amplifier 33, the AGC 34 and the IV converter 35 and amplified. The voltage-converted optical signal is input to the A / D converter 60 through the multiplexer 50, converted to the voltage V1, and output to the CPU 10. The CPU 10 stores the voltage V1 in the RAM 10b. At this time, the voltage V1 is represented by Expression (1) from the nature of the PSD, where the length L1 is the length of the long side of the PSD 32 and α is a proportional constant.
[0020]
V1 = α · (L + ΔL) / L1 (1)
Next, the CPU 10 switches the analog switch in the multiplexer 50 to the contact point 52, performs the same light emitting operation, converts the voltage to the voltage V2 according to the received light signal, and outputs the voltage to the CPU 10, and the CPU 10 stores the voltage V2 in the RAM 10b. I do. At this time, the voltage V2 is expressed as in the equation (2) in the same manner as the voltage V1.
[0021]
V2 = α · [L1− (L + ΔL)] / L1 (2)
Next, the CPU 10 switches an analog switch in the multiplexer 50 to the contact 53, performs the same light emitting operation, converts the voltage to a voltage v1 corresponding to the received light signal, and outputs the voltage to the CPU 10, and the CPU 10 transfers the voltage v1 to the RAM 10b. Store. At this time, from the nature of the PSD, the voltage v1 is expressed as in equation (3), where the length L2 is the length of the long side of the PSD 42 and the proportional constant β is a proportional constant.
[0022]
v1 = β · (L2 / 2 + ΔL) / L2 (3)
Finally, the CPU 10 switches the analog switch in the multiplexer 50 to the contact point 54, performs the same light emitting operation, converts the voltage to the voltage v2 corresponding to the received light signal, and outputs the voltage to the CPU 10, and the CPU 10 stores the voltage v2 in the RAM 10b. . At this time, the voltage v2 is expressed as in the equation (4) in the same manner as the voltage v1.
[0023]
v2 = β · [L2− (L2 / 2 + ΔL)] / L2 (4)
With the above four light projecting operations, two voltages V1 and V2 necessary for calculating the distance to the subject, and voltages v1 and v2 relating to the lack of a beam are obtained.
[0024]
Here, when all of the projection light from the IRED 22 is irradiated on the subject OBJ, the reflected light from the subject OBJ that forms an image on the PSD 32 has a substantially circular shape. When the subject OBJ is slightly shifted to the right from the center of the screen as in a), the reflected light from the subject OBJ that forms an image on the PSD 32 is only a part of a circle as described above. The center of the circle of the light beam is located at a position L away from the end point of the PSD 32 on the IRED 22 side, but since the center of gravity of the light beam is displaced from the center of the circle by a length ΔL away from the IRED 22, this signal is If it is processed as it is, the distance measurement result will be a longer distance than it actually is. However, at this time, since the reflected light from the subject forms an image on the PSD 42 as shown in FIG. 4C, the length ΔL can be calculated using the two voltages v1 and v2 described above. . The CPU 10 reads out the two voltages v1 and v2 from the RAM 10b, deletes the proportionality constant β, and obtains the length ΔL as in equation (5).
[0025]
ΔL = (v1−v2) / (v1 + v2) · L2 / 2 (5)
This length ΔL is compared with a predetermined length ΔLmin. If the length ΔLmin is shorter than the length ΔLmin, there is no beam chipping, or even a very small beam. May be compromised. Therefore, in this case, the CPU 10 reads out the two voltages V1 and V2 from the RAM 10b and calculates the value X as shown in Expression (6).
[0026]
X = (L + ΔL) / L1 = V1 / (V1 + V2) (6)
Here, when the value X is equal to or larger than the fixed value Xnear, that is, when the distance to the subject is shorter than the predetermined distance Lnear, the beam diameter is often sufficiently small with respect to the main subject, so that the value X is not corrected and the value X is used. Is calculated.
[0027]
If the length ΔL is equal to or longer than the length ΔLmin, it is determined that the beam is missing, and the CPU 10 reads out the two voltages V1 and V2 from the RAM 10b, deletes the term of the length ΔL, and obtains the equation (7). Is calculated.
[0028]
X = L / L1 = V1 / (V1 + V2) -L2 · (v1-v2) / {2 · L1 · (v1 + v2)} (7)
If the PSD 32 and the PSD 42 have the same shape, since the length L1 and the length L2 are equal, the equation (7) is further simplified and becomes the equation (8).
[0029]
X = V1 / (V1 + V2)-(v1-v2) / {2 · (v1 + v2)} (8)
From the value X obtained as described above, the CPU 10 can obtain the distance to the subject by referring to a table (FIG. 5) previously provided on the ROM 10a.
[0030]
By the way, the reflected light from the subject may not form an image on the PSDs 32 and 42 depending on the position of the subject. This phenomenon occurs because the light beam of the reflected light deviates from the light receiving surfaces of the PSDs 32 and 42 when the subject is located at a very short distance. Usually, when the reflected light from the subject is extremely weak, the subject is located at a long distance and the reflected light is determined to be weak, and the photographing lens is driven to the infinite position. When driven to the position, an object at a short distance is completely out of focus, and fails as a photograph.
[0031]
Therefore, in order to avoid such a failure, light is projected on the object OBJ prior to the distance measurement. The reflected light is processed by the distance detection circuits 30 and 40 and converted by the A / D converter 60. At this time, the sum of the voltages at the contacts 51 and 52 is the output of the PSD 32 and the sum of the voltages at the contacts 53 and 54. Is the output of the PSD 42, and these outputs are compared with a predetermined level to divide the lens driving method into the following four cases shown in FIG.
[0032]
First, when the outputs of the PSDs 32 and 42 are both equal to or higher than a predetermined level as shown in FIG. 6A, it is determined that the reflected light from the subject is hitting any of the PSDs, and a calculation is performed to determine the position of the subject. Is calculated and the lens is driven. Next, as shown in FIG. 6B, when the output of the PSD 32 is lower than the predetermined level and the output of the PSD 42 is higher than the predetermined level, it is determined that the subject is at a short distance and the light beam is out of the light receiving surface of the PSD 32. Judge, and immediately drive the taking lens to the closest position. Further, when the output of the PSD 32 is equal to or higher than the predetermined level and the output of the PSD 42 is equal to or lower than the predetermined level as shown in FIG. 6C, the LED 80 is turned on because the subject is in a short distance and the lack of the beam cannot be detected. To warn the photographer. Finally, when the outputs of the PSDs 32 and 42 are both lower than a predetermined level as shown in FIG. 6D, it is determined that the subject is at a long distance and the reflected light is weak, and the photographing lens is driven to the infinite position. I do. By dividing the cases in this manner, more accurate lens driving can be performed.
[0033]
As a second embodiment of the present invention, it is conceivable to use a two-dimensional PSD 42a and a switch 42b for determining the output thereof for detecting a missing beam as shown in FIG. When this element is used, the IRED 22 and the PSD 42 can be used as a light emitting and receiving system when a result as shown in FIG. 6B is obtained. That is, normally, the switch 42b is switched to the terminal Tx1 and the terminal Tx2, and the distance is measured using the IRED 22 and the PSD 32. Before the distance measurement, when the result as shown in FIG. The switch 42b is switched to the terminals Ty1 and Ty2 by the CPU 10, and the distance is easily measured using the IRED 22 and the PSD 42. The distance measurement by the IRED 22 and the PSD 42 is slightly less accurate because the base line length is shorter than that of the IRED 22 and the PSD 32. The accuracy is improved. The specific distance measurement operation is substantially the same as that described above, and thus will not be described. The distance is measured by the IRED 22 and the PSD 42, X is calculated from a calculation such as Expression (7) or Expression (8), and the distance to the subject is calculated based on the table shown in FIG. According to this table, the distance of the subject from infinity to a close distance of 0.19 m can be obtained theoretically, which is sufficient as the distance measurement distance for close-up photography.
[0034]
In this embodiment, a position detecting element (PSD) is used as a light receiving element, but another light receiving element such as a divided SPD or a CCD may be used.
[0035]
In this embodiment, the LED 80 is used to warn the photographer of an abnormality in the output of the light receiving element. However, the warning may be made by using a voice or the like.
[0036]
【The invention's effect】
According to the configuration of the present invention, appropriate lens driving can be performed even when outputs of the two light receiving elements cannot be obtained correctly, and a photograph with less defocus can be provided.
[0037]
Also, since the warning means is provided for issuing a warning to the photographer when the calculating means determines that there is an error, the photographer can recognize that a problem has occurred in the light receiving element output.
[0038]
Also, distance measurement can be performed for a subject located at a very close distance, which is advantageous during macro shooting.
[Brief description of the drawings]
FIG. 1 is a circuit diagram according to an embodiment of the present invention.
FIG. 2 is a configuration diagram according to an embodiment of the present invention.
FIG. 3 is a plan view showing an arrangement of an optical system according to an embodiment of the present invention.
FIG. 4 is a state diagram showing a state when a beam break occurs in the embodiment of the present invention.
FIG. 5 is a diagram showing a table on a ROM 10a for calculating a distance from a value X to a subject OBJ.
FIG. 6 is a diagram illustrating a light receiving element output and a lens driving position according to the present invention.
FIG. 7 is a configuration diagram according to another embodiment of the present invention.
FIG. 8 is a diagram showing a table on a ROM 10a for calculating a distance from a value X to a subject OBJ in another embodiment of the present invention.
FIG. 9 is a configuration diagram showing an optical system of a conventional distance measuring device.
[Explanation of symbols]
Reference Signs List 20 light emitting circuit 30 distance detecting circuit 40 beam missing detecting circuit 10 CPU (computing means)
70 Barrel drive

Claims (3)

A light projecting means for projecting the measuring light to the subject,
A first light receiving unit that is located on the same plane orthogonal to the optical axis of the light projecting unit, is arranged at a distance from the light projecting unit and a first base line, and receives reflected light of the measurement light from the subject;
A second position shorter than the first base line at a position on the plane perpendicular to the first light receiving means and the light emitting means and shifted by 90 ° about the light emitting means . A second light receiving unit that is arranged at a base line distance and receives reflected light of the measurement light from the subject;
Calculating means for calculating a distance to an object from an output of the first light receiving means based on the base line length;
A photographing lens control unit that controls the amount of extension of the photographing lens from the output of the arithmetic unit,
The calculating means calculates the subject distance from the first and second light receiving means when both outputs are equal to or higher than a predetermined level, and the calculating means calculates the object distance only when the output from the second light receiving means is equal to or higher than a predetermined level. Means for judging that the subject is in the vicinity, means for judging an error when only the output of the first light receiving means is equal to or higher than a predetermined level, and means for judging the first and second light receiving means. Means for determining that the subject is at infinity when both outputs are below a predetermined level. 2. The distance measuring device for a camera according to claim 1, further comprising a warning unit for issuing a warning to a photographer when the calculation unit determines that an error has occurred. A light projecting means for projecting the measuring light to the subject,
A first light receiving unit that is located on the same plane orthogonal to the optical axis of the light projecting unit, is arranged at a distance from the light projecting unit and a first base line, and receives reflected light of the measurement light from the subject;
A second position shorter than the first base line at a position on the plane perpendicular to the first light receiving means and the light emitting means and shifted by 90 ° about the light emitting means . A second light receiving unit that is a two-dimensional light receiving element that is arranged at a base line distance and receives reflected light of the measurement light from the subject;
Calculating means for calculating a distance to an object from an output of the first light receiving means based on the base line length;
A photographing lens control unit that controls the amount of extension of the photographing lens from the output of the arithmetic unit,
The calculating means calculates a subject distance from an output of the second light receiving means in the second base line length direction when only an output of the second light receiving means in the first base line length direction is equal to or higher than a predetermined level. A distance measuring device for a camera.

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