JPH041885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an active autofocus device.

In recent years, various types of electrical distance measuring devices have been used, especially for cameras. One way to classify these methods is into active methods and passive methods.The former projects infrared light etc. from the device side onto the object and uses the reflected light, while the latter uses the reflected light from the object itself. It uses imaging light. Although active methods consume more power than passive methods because they project energy, they have the advantage of being able to measure distances even in the dark, and due to this merit, they are likely to become more widely used in the future. There is.

The biggest drawback of the active method is that the energy can only reach a finite distance. However, in recent years, high-output infrared light emitting semiconductor lasers have been developed as infrared light emitters, and have become capable of projecting light over longer distances, replacing conventional infrared light emitting diodes.

The issue here is eye safety when looking into a high-output light source at a very close distance. For example, it is known that a distance measuring device receives the reflected light from an object within the measurable distance range and controls the emitted energy so that the received light energy is constant, but this is a separate safety measure. It's not that.

The present invention provides a safety device that is effective when, for example, an object is located at a close range (hereinafter referred to as an ultra-close range) that is closer than the measurable range of a distance measuring device. In order to achieve the above object, the present invention projects a luminous flux toward an object to be measured, and receives reflected light from the object at a sensor section that is a predetermined distance from the light source that projects the luminous flux, An active autofocus system detects the receiving position of the reflected light on the sensor section to perform focusing, and controls the intensity of the luminous flux projected from the light source based on the output level of the sensor section using an intensity control circuit. In the cass device, the sensor section is disposed so as to receive the reflected light when the object to be measured is located farther than a position corresponding to a movable limit position on the short distance side of the photographic lens, and providing a sensor section separate from the sensor section that receives the reflected light when the object to be measured is located at a distance closer than a position corresponding to a movable limit position on the short distance side of the photographing lens;
An active device that achieves the above purpose by setting the intensity of the luminous flux controlled by the intensity control circuit to below a predetermined level or to zero when the separate sensor unit detects that reflected light is received. The purpose of this invention is to provide a type autofocus device.

In the embodiment described below, the pair of sensors 11 and 12 in FIG. 1 correspond to a sensor section, the sensor 13 in FIG. 1 corresponds to a separate sensor section, and the adder 7 in FIG. The output control circuit 6 corresponds to an intensity control circuit.

Hereinafter, an embodiment of the present invention will be described. In FIG. 1, projection light from a light emitting element 4 such as a semiconductor laser fixed to a camera is projected onto a subject 1 by a projection lens 3, and its diffusely reflected light is A part of the light is received by the light receiving lens 10 and guided onto a pair of sensors 11 and 12. As a pair of sensors, for example, 3
A terminal pin photodiode, etc. can be used. The difference between the outputs of the sensors 11 and 12 is taken, and the photographing lens drive motor 9 is controlled according to the positive, negative, and magnitude of the signal. Further, the focusing movement of the photographic lens 16 and the pair of sensors 11 and 12 are linked.
In FIG. 1, since the output of the sensor 12 is large, the motor 9 drives the lens 16 in a direction toward the focusing surface 19, and in conjunction with this, the sensor 12
The holders 14 1 and 12 are moved downward in the figure. When the center of gravity of the reflected light intensity from the subject 1 reaches the boundary between the sensors 11 and 12, the difference signal between the sensors becomes zero, the motor stops, and the lens focuses.

In other words, when the sensor 12 receives reflected light, the photographic lens is extended, when the sensor 11 receives reflected light, the lens is retracted, and when both sensors receive reflected light of equal intensity, the lens is stopped. do.

The above is based on the principle of triangulation with a baseline length.

Now, the outputs of sensors 11 and 12 are added,
The sum signal controls the light emission output so that the sum signal remains constant. As a result, the light emission output is suppressed to a level that is safe for the eyes within the measurable distance range.

In FIG. 1, the photographing lens 16 does not focus on a subject that is closer than the subject 1.
In other words, this is because the amount of movement of the photographic lens 16 and the holder 14 is limited from being infinite to being correlated only within the distance to the subject 1.

Further, in FIG. 1, the photographing lens and holder 14 are in a position to focus on an object at an infinite distance.
In this state, if a subject, especially an eye, comes within close range, conventionally, there is no sensor to receive the reflected light, so the sum signal becomes zero and the light emission output reaches its maximum, which is not desirable. Furthermore, even if the lens is located at a very close position, there is still a very close distance at which the sensor 12 cannot receive reflected light.

In the embodiment of the present invention, a sensor 13 is provided at a position further extending from the sensor 12, and the sensor 13 is provided at a position where the sensor 12 is further extended.
1 and 12 in a holder 14 to receive reflected light from an extremely close object, and with this output,
Controls light output. At this time, the output control circuit 6 may set the emission energy to a predetermined value or may set it to zero. 21, the lens is in a close position, and sensor 1
2 or 13 is a close switch that stops the light emission and motor drive when receiving reflected light.

FIG. 2 shows another embodiment, in which a reflector 31 is used to guide reflected light from an extremely close object to the sensor 12.
It has been established. In this case, the output from the sensor 12 is proportional to the square of the subject distance and proportional to the subject reflectance, so it is extremely close.
This becomes extremely large, and the AGC circuit 601 significantly reduces the light emission power.

FIG. 3 is an improved version of the embodiment of FIG. Second
In the figure, there is a risk that reflected light from an extremely close object may reach the boundary between the sensors 11 and 12 and generate a focus signal. For this reason, in the improved example shown in FIG. 3, the reflecting mirror 32 has a curved surface so that all reflected light from any object at a very close distance is guided onto the sensor 12.

Here, the present invention is also effective for variations based on the triangulation principle. That is, contrary to FIG. 1, the light emitting element may be linked to the photographic lens. In this case, the sensor is fixed to the camera. Alternatively, both the light emitting element and the sensor may be linked with the photographing lens. Furthermore, both the light emitting element and the sensor are
It may also be unlinked, ie, fixed to the camera. Alternatively, one or three or more sensors may be used.

As explained above, according to the present invention, by detecting the reflected signal from an object at a very close distance, it becomes possible to control the projection output, which was impossible in the past.
In particular, it has the effect of increasing eye safety at very close range.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIGS. 2 and 3 are partial block diagrams showing only modified parts of other embodiments. 4 is a projection signal source, 1 is an object to be measured, 11, 1
2 is a distance measurement sensor, 13 is a super close detection sensor, 6 is an output control circuit, 21 is a close proximity switch, 3
1 and 32 are reflecting mirrors.

Claims (1)

[Scope of Claims] 1. A light beam is projected toward an object to be measured, and the reflected light from the object to be measured is received by a sensor section that is a predetermined distance away from a light source that projects the light beam, and the light beam on the sensor section is In an active autofocus device that detects a receiving position of reflected light and performs focusing, and controls the intensity of the luminous flux projected from the light source based on the output level of the sensor section using an intensity control circuit, the sensor The part is arranged to receive the reflected light when the object to be measured is located further away than a position corresponding to the movable limit position on the near side of the photographing lens, and a sensor unit separate from the sensor unit that receives the reflected light when the device is located closer than the position corresponding to the movable limit position on the short distance side;
An active autofocus system, characterized in that when the separate sensor section detects that reflected light is received, the intensity of the light flux controlled by the intensity control circuit is set to below a predetermined level or to zero. scum device.