JPH0160802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a distance measuring device for measuring the distance to a subject used for automatic focusing of optical lenses of photographic cameras, television cameras, etc. The present invention relates to a distance measuring device that uses an ultrasonic distance measuring method and an optical distance measuring method, which is effective for television cameras equipped with high zoom lenses.

Conventional configurations and their problems In recent years, high magnification (4x to 12x) TV cameras for home use aimed at general amateurs have been
Zoom lenses have been put into practical use as standard equipment; It had a problem that caused blurring. Against this background, television cameras with autofocus functions have begun to be put into practical use. 2. Description of the Related Art Cameras equipped with an automatic focus adjustment device that uses an optical method such as triangulation using light projected onto a subject are emerging.

However, in the case of the former ultrasonic method, since it measures the time until the ultrasonic wave is reflected, it is not affected by the amount of natural light or the shape of the subject, and the distance measurement accuracy is high. There is a limit to the distance that can be emitted, and the range that can be measured is limited to relatively short distances.

On the other hand, in the latter optical distance measurement method, when triangulation is used, the distance that can be measured is limited by the characteristics of the light projection part, and the distance measurement is limited by the characteristics of the mirror. There is a problem with accuracy, that is, the range of distance measurement cannot be made small, and in those without a light projecting section, distance measurement becomes impossible regardless of the distance when natural light decreases, and in addition, in the case of a device that does not have a light projecting section, distance measurement is impossible regardless of the distance. Similarly, there is a problem that the range of distance measurement cannot be made small.

Furthermore, a reflection method in the optical ranging method is used. In other words, the method of detecting the level of light from the subject does not use a mirror, so the distance measurement accuracy as described above is improved, but the ultrasonic method detects the level and uses the detected amount as a distance signal. Unlike the triangulation method, this time the shape of the subject,
This method has a problem in that it is greatly affected by the reflectance, and different distance information will be output if the object is different, even though the distance is the same.

As described above, the distance measuring devices used in automatic focusing devices that have been put into practical use so far have their own merits and demerits, and the reality is that none of them can be guaranteed to be perfect.

Purpose of the Invention The present invention has been made in view of the above-mentioned points, and it effectively combines the high distance measurement accuracy of the ultrasonic method with the far-point distance measurement of the optical method, and is capable of further improving the distance measurement accuracy. An object of the present invention is to provide a distance measuring device suitable for a high-power zoom lens in a television camera.

Structure of the Invention A distance measuring device according to the present invention includes an ultrasonic distance measuring means that measures the distance to the object by directing ultrasonic waves toward the object and detecting reflected waves; First and second starting circuits start the respective operations of the optical distance measuring means, and receive the distance measuring signal from the ultrasonic distance measuring means and determine whether or not it corresponds to a predetermined distance. A first determining circuit outputs either a distance signal or an operation start signal of the second starting circuit described above, and receives a distance measurement signal from the optical distance measuring means and determines whether or not it corresponds to a predetermined distance. , and a second discrimination circuit that outputs either the distance measurement signal or the operation start signal of the first activation circuit according to the result.

DESCRIPTION OF EMBODIMENTS Hereinafter, a distance measuring device according to the present invention will be described with reference to the drawings, but before that, two distance measuring methods that have been put into practical use in the past will be briefly explained.

FIGS. 1A and 1B show schematic configuration diagrams of conventionally known distance measuring methods, where A is an ultrasonic method and FIG. 1B is an optical method.

In FIG. 1A, when a starting signal is applied from the terminal 1a, the oscillation circuit 1 starts operating and supplies a predetermined resonant frequency to the transmitting/receiving circuit 3.

Therefore, the ultrasonic sensor 2 starts oscillating and starts irradiating the subject 6 with ultrasonic waves.

On the other hand, the distance/time storage circuit 5 also starts operating at the same time in response to the starting force signal at the terminal 1a, and starts measuring the time corresponding to the distance. Thereafter, after a period of time corresponding to the distance from the subject 6, the received wave from the subject is received by the transmitting/receiving circuit 3 and transmitted to the distance/time storage circuit 5 via the received signal amplification circuit 4. 5, the time measurement is stopped and the distance to the subject is stored as a time value.

Next, in the case shown in FIG. Therefore, an example of an optical reflection method that is equivalently converted is shown.

Generally, when an infrared light source is used, the reflectance is almost constant regardless of the type of object, so measuring the reflectance can equivalently calculate distance conversion. It is possible.

First, when an activation signal is applied from the terminal 9a, the light transmitter 9 including a power source for causing the infrared light source 7 to emit light is operated, and provides infrared light having a desired wavelength to the subject 6'. At the same time, the reflected light is received by the light receiving sensor 8, and an amplified output signal is transmitted to the switch circuit 11 through the light receiving amplifying circuit 10. The switch circuit 11 is configured to operate for a short period of time in response to a start signal from the terminal 9a, and is a circuit that transmits the output signal to the peak hold circuit 12 at the next stage every time the infrared light source 7 emits light. be.

The peak hold circuit 12 is a circuit for storing the peak value of the output signal, and
It has a refresh function that stores the peak value of the output signal every time it is transmitted.

Therefore, the distance to the subject can finally be expressed by the peak value of the peak hold circuit 12.

The distance measuring device according to the present invention is a combination of an ultrasonic distance measuring method and an optical reflection distance measuring method that perform the basic operations, and one embodiment thereof has a configuration as shown in FIG.

In the illustrated embodiment, when measuring the distance to the subject, priority is given to ultrasonic distance measurement, and when the distance information exceeds the limit distance of ultrasonic distance measurement, optical distance measurement is performed over ultrasonic distance measurement. The operation flow will be described in detail below with reference to the pulse chart of FIG. 3.

First, at the time of T ₁ from the external input terminal 14a connected to an external circuit (not shown), the signal shown in FIG.
When a starting signal as shown in FIG. 1 is applied, the starting circuit 14 starts operating and sends an operating signal as shown in FIG.
to enter the operating state.

Now, if the distance to the subject 6'' is 5 m, which is shorter than the distance that can be measured by the ultrasonic method, for example 7 m, the ultrasonic distance measuring means 13 will have the distance shown in FIG. A time signal corresponding to a subject distance of approximately 29 ms is stored.

On the other hand, if the object distance is longer than the measurable distance of the ultrasonic distance measuring means 13, for example 8 m, the ultrasonic distance measuring means 13 stores an object distance time of approximately 47 ms, as shown by the dotted line. It turns out.

In the present invention, the first step is to determine the subject distance time.
The first discrimination circuit 15 is connected to the ultrasonic distance measuring means 13, and when the time _T2 corresponding to the subject distance of 7 m, that is, 41 ms, is exceeded, the first discrimination circuit 15 detects the 1 discrimination signal is generated from the terminal 16, the operation of the starting circuit 14 is stopped, and the operation of the ultrasonic distance measuring means 13 is stopped.

At the same time, the first discrimination signal is transmitted to the optical activation circuit 1.
7, the optical activation circuit 17 is activated, generates an optical activation signal as shown in FIG. 3e, and puts the optical ranging means 18 having the configuration shown in FIG.

Therefore, the optical distance measuring means 18 performs optical distance measurement corresponding to the reflectance of the subject 6'' and performs the second optical distance measurement described later.
A distance signal corresponding to the desired subject distance is sent to a terminal 21 via a buffer circuit 20 via a discrimination circuit 19.
Output to. Furthermore, when the object distance is 7 m or less during ultrasonic distance measurement, the first discrimination circuit 15 does not operate, so the distance signal from the ultrasonic distance measurement means 13 is buffered via the first discrimination circuit 15. circuit 2
0 and is operated to provide a distance signal to the terminal 21.

One embodiment of the distance measuring device according to the present invention performs the above-mentioned operation, but in general, since a television camera constantly photographs a dynamic subject, the distance measuring operation is performed continuously. There is a need,
In particular, although not shown, when the object distance is 7 m or less during ultrasonic distance measurement, the ultrasonic distance measuring means 13 repeatedly performs the above-described one cycle of distance measurement at a desired interval. If it becomes more than that,
It goes without saying that the optical distance measuring means 18 repeatedly measures distances at desired intervals.

Furthermore, when the subject distance becomes 7 m or less during optical distance measurement, the second discrimination circuit 19 generates a second discrimination signal at the terminal 22 as shown in _FIG . Stop the operation of the circuit 17,
On the other hand, the starting circuit 14 is placed in an operating state. Therefore, the optical distance measuring means 18 becomes inactive, and the ultrasonic distance measuring means 13 is turned back into an active state, and the distance measuring device according to the present invention is placed in the ultrasonic distance measuring mode. .

In addition, in the illustrated embodiment, an infrared reflection method is used as an optical distance measuring method, which uses the reflectance of the object to equivalently calculate the distance to the object, but the method is not necessarily limited to this method, and as explained at the beginning. Of course, the same effect can be achieved by combining with the triangulation method.

Effects of the Invention The distance measuring device according to the present invention takes advantage of the excellent distance measurement accuracy of the ultrasonic distance measurement method when the object distance is relatively short, and when the object distance becomes long and ultrasonic distance measurement becomes impossible. In such cases, distance measurement is performed using an optical distance measurement method, and in order to effectively utilize the features of each distance measurement method, the activation configuration of each distance measurement method is determined by a discrimination circuit that operates according to the subject distance. Since it is characterized by controlling the operation, it has the effect of enabling more accurate distance measurement of the object.

[Brief explanation of drawings]

Figures 1A and 1B are schematic configuration diagrams showing distance measuring methods of conventional distance measuring devices, in which Figure 1A uses an ultrasonic method, Figure 1B uses an optical method, and Figure 2 shows the method of the present invention. FIG. 3 is a block diagram of one embodiment of the present invention, and FIG. 3 is a pulse chart showing the operating state of one embodiment of the present invention. 13... Ultrasonic distance measuring means, 14... Starting circuit,
15...first discrimination circuit, 17...optical activation circuit,
18... Optical ranging means, 19... Second discrimination circuit, 20... Buffer circuit.

Claims (1)

[Scope of Claims] 1. Ultrasonic distance measuring means that measures the distance to the object by emitting ultrasonic waves toward the object and detecting reflected waves, and light from the object or projecting light onto the object. an optical distance measuring means that measures the distance to the object by triangulation or optical reflection using the reflected light of the object, and controls the start of operation of each of the ultrasonic distance measuring means and the optical distance measuring means. a first and second starting circuit that compares a first ranging signal from the ultrasonic ranging means with a predetermined distance signal, and depending on the comparison result, the first ranging signal or the second starting circuit; a first discrimination circuit that outputs one of the operation start signals for operating the
A second ranging signal from the optical ranging means is compared with a predetermined distance signal, and depending on the comparison result, either the second ranging signal or an operation start signal for operating the first starting circuit is output. and a second discrimination circuit, wherein the first and second discrimination circuits selectively output the first and second distance measurement signals from different distance measurement means depending on the distance to the subject. Features a distance measuring device. 2. The first recording circuit has an external input terminal into which a predetermined signal is input, and is operated with priority over the second starting circuit, so that the ultrasonic ranging means is operated before the optical ranging means. A distance measuring device according to claim 1.