JPS599509A - Active type distance measuring device - Google Patents

Abstract

PURPOSE:To save power consumption, by detecting a light beam, which is directed to the vicinity of a light projecting element, among the reflected light beams from a body whose distance is to be measured, and controlling the light output of the light projecting element when the detected output is a specified level or more. CONSTITUTION:An object 1, a human eye 2, which looks light projecting element 4 at the very close distance, a light projecting lens 3, the light projecting element 4, and a ring shaped optical sensors 5, which are arranged around the light projecting element 4, are provided. A light receiving lens 13 is provided so that the image of the reflected light of the projected light spot is formed on optical sensors 11 and 12, which are light receiving elements. The optical sensors 11 and 12, can be moved up and down at the rack part of a holder 14. The rack part is moved by a gear 15 and a focal point adjusting gear 16. A lens group 17 and its holder 18, which are related to the focal point adjustment, are provided in an image pickup lens system. Moving power is transmitted to the holder 18 from the gear 16. The holder 18 is moved in the axial direction of the image pickup lens system, and the focal point adjustment is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention of this application relates to an active distance measuring device, particularly an active type 611 distance measuring device in an automatic focusing device, which controls the output of a light projecting unit according to the distance of an object to be measured. The problem is the means.

Background technology A number of distance measuring devices V1 based on the principle of triangulation have already been proposed and are in practical use in cameras, etc., but they can be roughly divided into passive types that detect the contrast pattern of the subject and determine the distance to the subject, and It is classified as an active type, in which the distance to the subject is determined by emitting a beam of light toward the subject and determining the imaging position of the reflected light. The invention of this application relates to the latter active type.

FIG. 1 shows the principle of triangulation in a simplified manner. As is well known, when the base line length is L1 and the distance to the object to be measured is R, R=L-tanθ. Therefore, in an active distance measuring device, it is necessary to ensure that the light beam emitted from the light projecting element reaches a sufficient distance, and to increase the length of the base line in order to improve the resolution of distance measurement. By the way, conventional active distance measuring devices, especially active automatic focusing devices, can perform necessary and sufficient distance measurement for 35 mm cameras etc. by using, for example, a near-infrared light emitting device IRED. When used in an 8 mm camera or a video camera, the purpose could not be fully achieved because the light emitting output was not sufficient to achieve the above-mentioned distance.

Therefore, it has been considered to use laser light, which has better monochromaticity, coherence, and focusability, as a light emitting source, and attempts have been made to use semiconductor lasers. By the way, while laser beams used in video discs and measuring instruments use emission wavelengths in the visible range, when used in automatic focusing devices, it is desirable that the emission wavelengths be in the infrared range due to their nature. Therefore, the position of the laser beam cannot be visually recognized, and the laser beam directly enters the eye. Considering the output, it does not cause any major accidents such as blindness, but it does cause discomfort. Therefore, it is inappropriate to use a semiconductor laser in an automatic focusing device such as a camera without a clear countermeasure in this regard.

The invention of this application is applicable not only to semiconductor lasers, but also to light emitting elements suitable for use when using a light emitting element with a large light emitting output or a light emitting element whose emitted light rays cause discomfort to the user. The subject of this study is the means for controlling this.

Purpose of the invention of this application Therefore, the invention of this application is an active measurement system capable of controlling the light output of a light emitting element according to the subject distance, saving power consumption, and taking safety measures. The purpose is to provide a range device.

A further object of the invention of this application is to provide an active distance measuring device that can detect objects located extremely close to the object.

Structure of the invention of this application A first invention of this application includes: a light projecting element; a light receiving element disposed at a position apart from the light projecting element by a baseline length; a detection means (for example, the optical sensor 5 in the specific example of FIG. 2) that detects an object moving toward the vicinity of the optical element; and when the detection output of this detection means is equal to or higher than a predetermined level, the light emission output of the light projecting element is controlled. The present invention is characterized by an active distance measuring device comprising a control means (also an output control circuit 7);

In a second invention of this application, in place of the control means in the first invention, the detection output of the detection means is equal to or higher than a first predetermined level, and the light reception output of the light receiving element is equal to or lower than a second predetermined level. It is characterized by a control means for controlling the light emission output of the light projecting element at certain times.

In the above, the reference to specific examples illustrated later does not limit the scope of the invention of this application in any way, and the invention of this application can be modified as appropriate within the scope of the claims.

Regarding a specific example of the active distance measuring device according to the invention of this application (Fig. 2) Hereinafter, with reference to Fig. 2, a specific example in which the active type distance measuring device according to the invention of this application is applied to an automatic focus adjustment device will be explained. . Figure 2 shows a type in which the light receiving element detects differential output,
This is an example in which a light receiving element and a focusing lens of a photographing lens system are controlled in conjunction with each other. In the figure, xVi subject, 2
shows a human eye looking into the light emitting element at very close range.

3 is a light projecting lens which forms a light projecting spot image on the subject -L. 4 is a light projecting element, which in this example is a laser diode. The SFi optical sensor is composed of a ring-shaped element arranged around the light projecting element 4 or a plurality of elements arranged on a circumference surrounding the light projecting element 4. 6 is an adder, 7 is an output control circuit, 8 is a drive circuit, 9 is a differential amplifier, and 10 is a motor.

11 and 12 Body A of the light receiving element of the invention of this application
This is an optical sensor that is composed of two elements placed close to each other in this example, but even if the element is divided into two regions and output can be taken from each region. good. 13 is a light-receiving lens for forming the reflected light of the projected light spot image on the optical sensors 11 and 12; 14;
1 is a holder for the optical sensors 11 and 12, which has an integral rack part and is movable in the vertical direction in the figure. 15 is a gear for moving the rack section, 16H is a focusing gear, 17
is the lens group involved in focusing operation in the photographic lens system, 1
8 is a holder for the lens group 17. The holder 18 receives power from the gear 16, moves in the axial direction of the photographic lens system, and performs a focusing operation. Reference numeral 19 denotes a close end switch, which operates when the lens group 17 involved in focusing operation is at its most extended position. Note that they are driven in conjunction with gears 15 and 16 motors 10.

To explain the operation of the apparatus shown in FIG. 2, in a normal focus adjustment operation, the laser light emitted from the light projecting element 4 hits the subject 1, is diffusely reflected, and is received by the light receiving element via the light receiving lens 13. Note that the figure shows a state in which light is received by the element 12.

Here, the differential amplifier 9 calculates the difference between the outputs of the elements 11 and 12, and drives the motor 10 based on the result. This control is performed so that the output of the differential amplifier 9 becomes zero, and the optical sensors 11 and 12 are controlled vertically in the diagram through a cam (not shown), a gear 15, 16, and a rack part of the holder 14, 17. Lens group 17 involved in directional movement and focusing operation
In the figure above, the movement in the left and right direction is linked to maintain correct focus.

The adder 6 adds the outputs of the optical sensors 11 and 12, and according to the added output, the output control circuit 7 and the drive circuit 8 control the light emission output of the light projecting element f4. This light emission output is sufficient as long as the amount of light received by the optical sensors 11 and 12 is the minimum necessary amount, so the output control is performed in the first step.
This is done for the purpose of saving power. The second purpose is a safety measure when the subject is at a distance such as infinity or when the reflectance of the subject is low.

As mentioned above, the light emitting output control of the light emitting element 40 is performed by controlling the light emitting element 1
Since the aim is to keep the light within a necessary and sufficient range to enable detection at 1,121c, the farther the subject is or the lower the reflectance of the subject, the greater the light emission output. Since the laser f light is coherent light and has less attenuation and a smaller spread angle than ordinary light when propagating through the air, in this device 1, the projecting lens 3 is designed to have a certain spread angle. As a result, even when the light emitting output is the highest, the light emitting element 4 (laser diode) can be viewed directly at a distance corresponding to the light emitting output without causing any abnormality to the eyes.

Even if safety measures are taken by controlling the light emission output in this way, and the camera is configured to be able to measure distances even for distant objects, there are still some aspects that are insufficient. Here, the third purpose is the optical sensor 11,
Countermeasures are required in case the reflected light does not return to 12. For example, if the front surface of the light receiving lens 13 is covered for some reason, even if the subject is close, the light sensor 11.
No output can be obtained from 2. In this case, the above-mentioned control system operates by determining that the subject is at an infinite distance, and the output of the light projecting element 4 becomes maximum, so it is dangerous to look into the light projecting element in this state. Also, if you suddenly look into the light emitting element from directly in front of the camera when the subject is at infinity, the distance between the face and the camera is too close and the reflected light does not return to the light receiving element (reflected light does not return to the light receiving element area). ), and in this case too, the automatic focus adjustment device determines that the subject is at infinity, and the light projecting element 4 emits light with a large output.

The reason why recreational distance measurement occurs in these cases is that reflected light does not return to the light receiving element.

In the first invention of this application, the above-mentioned detection means, that is, the optical sensor 5 provided near the light projecting element 4 prevents the above-mentioned malfunction. This optical sensor 5 includes a light emitting element 4
Detects the presence and strength of reflected light toward the vicinity. If the subject is actually at infinity, no light reception output will be obtained even if the optical sensors 11 and 12 and 5 are shifted by h.
In the above-mentioned case, the optical sensors 11 and 12 have no output due to the reflected light, and the force tip sensor 5 has a considerably high level of light reception output. Therefore, a specific level is determined in advance for the light receiving output of the optical sensor 5, and when a light receiving output exceeding this level is obtained, the front surface of the light receiving lens 13 is blocked for some reason, or Because the light emitting element was unexpectedly looked into from the front of the camera, the light receiving elements 11 and 12 were unable to receive any output, so the output difference was also zero (more precisely, below a certain threshold). Stop at that position. Alternatively, the output control circuit 7 can be controlled to forcibly stop the motor 10 by detecting that the output of the optical sensor 5 is equal to or higher than the predetermined level. In the normal focus adjustment operation of the apparatus shown in FIG. 2, the output control circuit 7 operates according to the subject distance.1. Therefore, the control device of the same circuit corresponds to 1e of the focusing lens group 17, but only in the above case, the output of the light emitting element 4t is suppressed to the minimum output by the output of the optical sensor 5. This state is canceled when the light receiving output of the optical sensor 5 becomes, for example, below the predetermined level, and thereafter the normal focus adjustment operation described above is performed.

The second invention of this application is that under the above-mentioned condition, the optical sensors 11 and 12 do not receive an output due to the reflected light (more precisely, the output falls below a certain threshold predetermined in consideration of noise). ), and when an output of a predetermined level or higher is obtained from the optical sensor 5, it is determined that for some reason the autofocus W+4 unit was not able to detect the object that was present at a close distance, and the output control circuit 7 controls the drive circuit 8 so that the light emitting output of the light projecting element 40 is minimized. On the other hand, the focusing lens group 17 stops at that position as in the first invention. This state is canceled when one or both of the optical sensors 11 and 12 produces a certain level of light reception output, or when the light reception output of the optical sensor 5 falls below a certain level. After the release, the normal focus adjustment operation described above is performed.

Furthermore, when the light emitting output of the light projecting element 4 reaches the minimum in the above-mentioned special state, the focusing lens group 17 can be driven to the most retracted position instead of being stopped at that position.

That is, through the first and second inventions, the output of the optical sensor 5 is equal to or higher than a predetermined level, and in the second invention,
In addition, the output control circuit 7 may detect that the optical sensors 11 and 12 have no light receiving output and control the motor IO so that the focusing lens group 17 moves to the most retracted position. Also, close end switch 19i1:, focusing lens group 1
7 is extended to the maximum extended position, the motor IO and the output control circuit 7 are controlled, and the focusing lens group 1
This is to maintain the position of 7 and the light emitting output of the laser diode 40 in that state.

Regarding a modification of the automatic focus adjustment device shown in FIG. 2, the device shown in FIG. 2 has optical sensors 11 and 12 in which light-receiving elements are arranged close to each other, or is divided into two regions, and output is taken out from each region. Consists of a light sensor that can
The invention of this application is a differential type that obtains distance information from the difference VC between these outputs, but the invention of this application is a method that obtains distance information from the peak output of a light receiving element, or a method that obtains distance information from the peak output of a light receiving element, or which element among the elements forming a photosensor array. It can also be applied to other ranging methods that obtain distance information based on whether a peak output is obtained.

Next, in FIG. 2, the focusing lens group 17 is connected to the light receiving element 11.1.
Although the control is performed in conjunction with 2, the light emitting element may be moved instead of the light receiving element, or both may be moved together. Note that without moving the light emitting element or the light receiving element itself,
It may also be a means that achieves the same effect as moving the light emitting/receiving element by rotating or moving an optical element such as a lens, a reflecting mirror, or a prism included in the light emitting system or the light receiving system.

Further, as for the light emitting lens 3 or the light receiving lens 13, if the light emitting element or the light receiving element can emit or receive a sharp spot image, 7 is not necessarily essential, and the light receiving lens 1 may also serve as the photographing lens. Can be done. Furthermore, the invention of this application also provides for an internal distance measuring device to have a virtual light emitting element corresponding to the light emitting element and the light receiving element in the invention of this application, respectively, on the central cross section perpendicular to the optical axis of the imaging lens. It can be applied assuming that the element and the light receiving element exist.

Finally, in the device shown in Fig. 2, an optical sensor 5 is installed near the laser diode 4, which is a light emitting element, but as an alternative, the return effect of the semiconductor laser can be used to generate electricity from the semiconductor laser by the reflected light that returns directly to the semiconductor laser. The above-mentioned control can also be performed by detecting resistance changes.

Effects of the invention of this application The invention of this application is based on the above-mentioned configuration and operation, and is a means for detecting reflected light from a distance-measuring object toward the vicinity of a light projecting element according to the distance of the distance-measuring object. When the output of this detection means is above a predetermined level, or the output of this detection means is the first
The light emission output of the light emitting element is controlled when the light receiving output of the light receiving element is above a second predetermined level and the light receiving output of the light receiving element is below a second predetermined level. This has the advantage that safety measures can be taken against such situations, and objects that are located very close to each other can also be detected.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the principle of triangulation, and FIG. 2 is a block diagram of a specific example of an active distance measuring device according to the invention of this application. In the figure, 4 is a light emitting element, 5 is a light sensor, 7 is an output control circuit,
8ii drive circuit, 11.12 indicates a light sensor forming a light receiving element.

Claims (4)

[Claims] (1) A light projecting element, a light receiving element disposed at a position separated by a baseline length from the light projecting element, and a detection means for detecting reflected light from the object to be ranged toward the vicinity of the light projecting element. and a control means for controlling the light emission output of the light projecting element when the detection output of the detection means is equal to or higher than a predetermined level. (2) The active distance measuring device according to claim (1), wherein the detection means is an optical sensor provided near the light projecting element. (3) The active distance measuring device according to claim (1), wherein the control means controls the light emission output of the light projecting element to a minimum when the detection output of the detection means is equal to or higher than the predetermined level. (4) a light projecting element; a light receiving element disposed at a baseline distance from the light projecting element; and a detection means for detecting reflected light from the object to be ranged toward the vicinity of the light projecting element. and a control means for controlling the light emission output of the light emitting element when the detection output of the detection means is above a first predetermined level and the light reception output of the light receiving element is below a second predetermined level. Active ranging device.