JPH0547815B2 - - Google Patents

Description

[Detailed description of the invention] The present invention projects light onto a subject from a light projecting element,
The present invention relates to an improvement of a device that measures reflected light from a subject and measures the distance to the subject.

Conventionally, in distance measurement systems that project light onto a subject, scan it, and measure distance, increasing the field of view reduces the accuracy of distance measurement, and in order to increase accuracy, it is necessary to It is necessary to increase the baseline length between the light receiving element and the light receiving element, and the field of view becomes wider when viewed from the light receiving element side, which increases the influence of noise from external brightness or light sources such as fluorescent lights. Currently, it is not possible to increase the angle of light, so we are currently using it as narrowly as possible, and the projection angle is about 1 to 2 degrees. For this reason, when photographing a subject, the distance-measuring field of view is normally located at the center of the photographic viewfinder frame, but this narrow distance-measuring field of view must be aligned toward the subject, which limits the composition of the shot. Because of the risk of missing the subject, I had to use pre-focus when shooting two people.

The present invention has been made in view of the above points and in order to eliminate the above drawbacks, and provides a distance measuring device that can measure distances with high accuracy from short distances to long distances without worrying about the composition of the photograph. A light source projects light toward a target, the reflected light is received by a light receiving element located a predetermined baseline length away from the light source, and a distance-dependent distance measurement signal is generated based on the received light signal. A distance measuring device that obtains a distance measuring device includes a light projecting means for sequentially scanning and projecting light toward a plurality of targets in different directions, and receiving reflected light of the light projected by the light projecting means from a plurality of different ranging fields of view. a light-receiving means for independently outputting a light-receiving signal corresponding to the reflected light from each field of view; a delay circuit for outputting each light-receiving signal with a different time delay corresponding to each distance-measuring field of view; and a focus adjustment means for performing focus adjustment based on the earliest output of the delayed outputs for the received light signal.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the principle of distance measurement related to the present invention, in which the LED is a light emitting element such as an infrared light emitting diode or a semiconductor laser, and is swung in the direction of arrow a.
The object OB is scanned from close range to infinity through lens _L1 . D is lens L ₁ and lens L ₂
The baseline length is the interval of . SPC1, SPC2, SPC
3. SPC4 is a light-receiving element, which receives the light image of the image projected onto the object OB by the LED by the lens _L2 by movement of the lens _L2 in the direction of arrow b. Therefore, the movement of the lens _L2 is such that when the light emitting element LED changes from close to the subject side to infinity, the light beam of the LED intersects the optical axis of the lens _L2 , and an image is formed at the intersection point. moves so that the image thereof is formed on one of the surfaces of the light receiving elements SPC1 to SPC4 through the lens _L2 . for example,
When using the distance measuring device of the present invention for automatic focusing of a camera, the light receiving elements SPC1 to SPC4 are placed at positions conjugate to the film surface placed behind the lens _L2 , or the light receiving elements SPC1 to SPC4 are placed at positions conjugate to the film surface placed behind the lens L2, or the lens L2 is placed separately from the photographic lens. ₂ ,
All you have to do is move the lens _L2 as described above.
In the state shown in Fig. 1, _the light receiving elements SPC1 to
The light image of SPC4 is focused through lens _L2 . The images are SPC1' to SPC4' (this image is not actually formed because no light beam is emitted from the light receiving element). Conversely, if the light emitter LED
Scan the range from SPC1' to SPC4' to capture the object OB.
All the images projected above are formed on the light receiving elements SPC1 to SPC4 by the lens _L2 . Therefore, the subject
At the OB position, the range of images of SPC1' to SPC4' becomes the distance measurement field of view. In this way, the object OB is scanned by the projection light of the light emitting element LED, and the scanned image is sent to the light receiving elements SPC1 to SPC4 via the lens _L2 .
The distance is measured by processing the signal from the light receiving element.

Figure 2 is a circuit diagram showing an example of an evaluation circuit that processes signals from photodetectors. OP1 to OP4 are operational amplifiers, and the photocurrents of photodetectors SPC1 to SPC4 are converted into voltages by feedback resistors 1 to 4, respectively. . Light emitting element
Since the LEDs are pulse driven, the outputs of OP1 to OP4 are AC signals. 5 to 8 are AC amplifiers OP1
~ Amplify each AC signal from OP4. 9-1
Reference numeral 2 denotes a synchronous detection circuit, which performs synchronous detection using a pulse synchronized with the driving pulse of the light projecting element LED, and converts the AC signals from the AC amplifiers 5 to 8 into DC signals. 29
32 are lines connecting the synchronous detection circuits 9 to 12 and the peak detection circuits 13 to 16, respectively. 33~
36 is the synchronous detection circuit 9 to 12 and the AND gate 21
The scanning of the light projector LED ends when the signal component, which is scanned by the light projector LED and converted into DC by the synchronous detection circuits 9 to 12, exceeds a certain detection level on the line connecting each of ~24 input terminals. Until
It transmits a "high" level signal, and at other times transmits a "low" level signal. 13 to 16 are peak detection circuits which are combined with timer circuits 17 to 20 to determine the exact timing of the signal peak.
Lines 37 to 40 connect the input terminals of the timer circuits 17 to 20 and the AND gates 21 to 24, respectively, and transmit peak signals. AND gate 21-2
The outputs of 4 are connected to each other so as to be provided as inputs to a NOR gate 25. Its output is connected to be input to the base of a transistor 27 via a current limiting resistor 26. 28 is the fourth
This is a magnet coil for moving a stop pawl that locks the lens barrel that holds the photographic lens shown in the figure. magnet coil 2
8 is connected to the power supply Vbat and the transistor 27.

FIG. 3 is a drawing showing signal waveform diagrams of each of lines 29-32.

FIG. 4 is a drawing of an embodiment of a lens barrel locking device that locks the movement of a lens barrel holding a photographic lens etc. upon completion of distance measurement. TL is a lens barrel that holds a photographic lens, etc. inside, and a spring is attached perpendicular to the plane of the paper.
Driven by the force of SP2. Spring SP2
The lens barrel TL is driven in the direction of arrow c, and since the lens barrel TL is threaded in a direction perpendicular to the page and is screwed into a fixed part (not shown), it can be driven in the direction of arrow c. Move perpendicular to the page. A gear GR is notched on the side of the lens barrel TL. ST is a stop pawl for stopping the movement of the lens barrel TL, which is rotatably supported by a shaft 41, and the tip of the stop pawl bites into the gear GR to lock the lens barrel TL. SP1 is a spring used to direct the tip of the stop pawl toward gear GR. Numeral 42 is a magnet around which a magnet coil 28 is wound, and when a current flows through the magnet coil 28, the tip of the stop claw ST is separated from the gear GR of the lens barrel TL.

Next, the operation of the embodiment of the present invention configured as above will be explained.

For example, if we consider an object with uniform reflectance,
The light projecting element LED is driven in pulses and scanned in the direction from close range to infinity, as described above.
The purpose of pulse driving of the LED is to improve the S/N ratio of the evaluation circuit and enable highly accurate distance measurement. The reflected light projected onto the subject is detected by light receiving elements SPC1~
The AC current enters the SPC 4, and is converted into an AC voltage by operational amplifiers OP1 to OP4 and resistors 1 to 4. The converted signal is amplified by AC amplifiers 5 to 8, and passes through synchronous detection circuits 9 to 12 to extract signal components. Convert to direct current. For example, in the case of a signal output on line 29, the DC signal is passed through the peak detector 13 and the timer circuit 17.
As a result, as shown in FIG. 3, a peak signal indicating the peak is output on line 37 at T ₁ hours after the peak. Similarly line 3
The signal waveform that appears on line 31 is detected by the peak detector 14 and timer circuit 18, and the signal waveform that appears on line 31 is detected by the peak detector 15 and timer circuit 19.
The signal waveform appearing on the line 32 is detected by the peak detector 16 and the timer circuit 20 from the respective peak points.
T ₂ , T ₃ , T ₄ hours later, the peak signal is on line 3, respectively.
8, 39, and 40. Therefore, the peak signals of objects located at the same distance are output at timings Q to Q' in FIG. 3, and are at the same time. The peak signals output to these lines 37 to 40 are initially at "low" level, and when the peak signal is output, they become "high".
level. Therefore, while the peak signal does not arrive,
The outputs of the AND gates 21 to 24 become "low" level, and the output of the NOR gate 25 becomes "high" level, so the transistor 27 connected to its base via the resistor 26 becomes conductive, and the magnet coil 28 becomes conductive. is in a energized state.
However, when the peak signal is output to line 37, for example, the signal exceeds the detection level of synchronous detection circuit 9, and line 33 is at a "high" level, so the output of AND gate 21 is "high". " level, and the output of the NOR gate 25 becomes a "low" level, making the transistor 27 non-conductive and cutting off the current to the magnet coil 28. Then, as shown in FIG. 4, the stop claw ST, which had been attracted by the magnet 42, is pulled by the spring SP1, and the tip of the stop claw ST is pulled toward the lens barrel TL, which is rotating in the direction of arrow c by the force of the spring SP2. gear notched on the side
By jumping into the GR, the lens barrel is locked, distance measurement is completed, and the closest subject, the main subject, is brought into focus. And then filming begins. If the projected image of the light projecting element LED from the subject is present in any of the light receiving elements divided in this way, accurate distance measurement and focus adjustment will be performed.

In the above embodiment, the light projecting element LED and the lens _L1 correspond to the light projecting means of the present invention, and the light receiving elements SPC1 to SPC4, the lens _L2 ,
Operational amplifiers OP1 to OP4, feedback resistors 1 to 4, AC amplifiers 5 to 8, synchronous detection circuits 9 to 12, peak detection circuits 13 to 16, timer circuits 17 to 20,
AND gates 21-24 and lines 29-40
corresponds to a light receiving means, and the NOR gate 25, current limiting resistor 26 and transistor 27 correspond to an evaluation circuit.

The present invention is configured and operated as described above to widen the field of view for distance measurement, making it easier for the photographer to take a free composition, and from the viewpoint of performance, the beam diameter of the light projecting means can be made small. Therefore, the power per unit area can be increased, the S/N ratio can be increased, and distance measurement can be performed even to objects with low reflectance. Furthermore, since the base line length can be shortened, there is an effect that the distance measuring device can be downsized. Note that this effect will be tremendous if a semiconductor laser, which is expected to become cheaper in the future, is used for the light projecting element. Furthermore, the light receiving means
By using a CCD array, etc., it is possible to configure any distance measurement field of view.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle of distance measurement related to the present invention, and Fig. 2 is a diagram showing the processing of the signal received by the light receiving element.
FIG. 3 is a circuit diagram of an embodiment of the evaluation circuit of the present invention, FIG. 3 is a signal waveform diagram of each of lines 29 to 32, and FIG. 4 is a diagram of an embodiment of the lens barrel locking device. 1-4...Feedback resistor, 5-8...AC amplifier,
9-12... Synchronous detection circuit, 13-16... Peak detection circuit, 17-20... Timer circuit, 21
~24...AND gate, 25...NOR gate,
26... Current limiting resistor, 27... Transistor, 28... Magnet coil.

Claims (1)

[Scope of Claims] 1. Light is projected from a light source toward a target, the reflected light is received by a light receiving element located a predetermined baseline length away from the light source, and distance dependent based on the received light signal. A distance measuring device that obtains a distance measurement signal that includes a light projection means that sequentially scans and projects light toward a plurality of targets in different directions, and a light projection means that projects light from a plurality of different distance measurement fields of view. a light receiving means for receiving the reflected light from each field of view and independently outputting a light reception signal corresponding to the reflected light from each field of view, and outputting each light reception signal with a different time delay corresponding to the distance measurement field of view. 1. A distance measuring device comprising: a delay circuit; and a focus adjustment means for performing focus adjustment based on the earliest output of the delay outputs for each light reception signal.