JPH0237314A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To facilitate automation of microarea focusing from normal automatic focusing and to improve operability by using a zoom encoder for detecting the focal length position of a zoom lens as a member which detects an infinite distance or the nearest distance in microphotographing and also detects whether microphotographing or not. CONSTITUTION:The device is provided with the zoom encoder 8 indicating the focal length position of the zoom lens 1 extended to the microarea, and the detecting means detecting not only the infinite and nearest distances in microphotographing but also whether microphotographing or not. As the member detecting the infinit and nearest distances in microphotographing and whether micro photographing or not, the zoom encoder 8 for detecting the focal length position of the zoom lens 1 is used. Thus, switching from normal automatic focusing to automatic focusing of the microarea is readily automated to improve operability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to an automatic focus adjustment device for a camera, and particularly to an improvement of an automatic focus adjustment device for a camera equipped with a zoom lens capable of macro photography.

(Background of the Invention) Conventionally, in automatic focus adjustment of a camera equipped with a zoom lens capable of macro photography, a camera that can perform automatic focus adjustment not only for normal automatic focus adjustment but also for macro photography has already been proposed. For example, Japanese Patent Application Laid-Open No. 61-26015 discloses a method in which the output of a focus detection circuit using a video signal from a video camera is switched using a switch to select between normal automatic focus adjustment and macro area automatic focus adjustment. ing. In this case, it was necessary to operate a switch when switching from normal automatic focusing to macro area automatic focusing.

(Object of the Invention) An object of the present invention is to provide an automatic focus adjustment device that can easily automate switching from normal automatic focus adjustment to macro area automatic focus adjustment and improve the operability of the device. That's true.

(Features of the Invention) In order to achieve the above object, the present invention provides a zoom encoder that extends to the macro area and indicates the focal length position of a zoom lens, and a signal from the zoom encoder that is extended to the macro area, and a signal from the zoom encoder. A detection means for detecting the near end and detecting whether or not macro photography is in progress, and thereby serves as a member for detecting the infinite end or close end during macro photography and detecting whether or not macro photography is being performed. , is characterized in that it also serves as a zoom encoder for detecting the focal length position of the zoom lens.

(Embodiment of the Invention) FIG. 1 shows an embodiment of the present invention, in which 1 is a zoom lens, a distance ring 2.degree. zoom ring 3. Macro switching lever 3a, index line 4, distance ring encoder 6
, a distance ring drive motor 7, a zoom ring encoder 8. It consists of a motor 9 for driving the zoom ring. 10 is an image sensor such as a CCD, 11 is a preamplifier, 12 is a video camera signal processing circuit, 13 is a video camera signal output terminal, and 14 is an AF
(autofocus) circuit, 15 is AF switch, 16
is the power zoom switch.

Figure 2 shows the zoom lens used in Figure 1, which is known per se.The front lens F moves in the optical axis direction by the rotation of the distance ring 2, and can perform normal focusing from infinity to about 1 meter. conduct. Variator (2) and convencator (C) are moved on trajectories (3) and (3), respectively, by a cam (not shown).

When the zoom ring 3 is brought into the competition focus range from the wide end, only the convencator C is extended toward the subject without changing the position of the variator V, and as it goes, the focus is brought into focus and the focusing distance shifts to a short distance direction. .

FIG. 3 shows the position of the distance ring 2, the position of the zoom ring 3 and the zone division of the respective encoders 6.8.

The distance ring encoder 6 is divided into three zones: (1) an end detection zone, a normal zone, and a close end detection zone. In so-called passive automatic focusing devices, including automatic focusing devices that use video signals, if the contrast of the subject is low or the brightness is below the low brightness limit, the AF flaw signal disappears and focus adjustment becomes impossible. On the other hand, when the focal point is greatly defocused, the AP multiplied signal also disappears. Therefore, in the case of passive method, if AF flaw signal cannot be obtained,
It is necessary to move the focus lens from end to end to search for AF flaw signals, a so-called search operation. At this time, an encoder or switch is required to detect the edge. If there is an AP double signal, the lens performs a hill climbing motion and adjusts the focus.

In the case of low contrast, the focus lens is often set to a common focal length of 3 m or the like. (2) The lens is set to the normal focal length by driving the motor 7 for a predetermined period of time from the end or the closest end at a known speed.

The zoom ring encoder 8 detects the focal length of the lens,
Correct the gain of the servo loop of the automatic focusing system. That is, when the focal length is closer to telephoto, the amount of change in focus on the focus plane when the distance ring 2 is rotated by a certain amount is large, so the speed of the motor 7 is set to be slow. On the other hand, if the vehicle is wide, the speed of the motor 7 is set faster. Thereby, even if the focal length changes, automatic focus adjustment operation is performed at an appropriate speed and stably.

Assume that the AF switch 15 is now turned on and the first mode, that is, normal automatic focus adjustment is performed, and a subject at 2 m is in focus.

When the macro switching lever 3a is operated to move the zoom ring 3 into the macro area, that is, the competition focus range, the signal of the zoom ring encoder 8 is switched (76 or Z7 in FIG. 3). As a result, the AF circuit 14 automatically shifts to the second mode. That is, the motor 9 is controlled to move the convencator C to perform automatic focus adjustment. At this time, the distance ring 2 is automatically set to the ■ end. When the convencator C moves from one end to the other, automatic focus adjustment becomes possible for all subjects from ■ to just in front of the lens. Edge detection for reversing the search mode is performed by the zoom ring encoder 8. In other words, ω end detection is performed in the wide end zone (Zs in Figure 3).
and the boundary of the competition focus range (Fig. 3, 26).

(1) A dedicated zone may be added for edge detection. If the AF flaw signal cannot be obtained even after searching, do the same as in the normal case (move the convencator C to a common focal distance of 3 m, etc.).

By the way, if a power zoom operation is performed in the first mode, the lens will go beyond the wide end and enter the competition focus range unless some consideration is taken. Normally, the macro switching lever 3a also serves as a mechanical stopper at the wide end, and the motor 9 slips at the wide end and does not enter the competition focus range. However, if there is no macro switching lever 3a, the AP circuit 14 can detect the boundary between the wide end and the competition focus range using the zoom ring encoder 8, and logically prohibit further rotation of the zoom motor. be.

Furthermore, since inadvertently performing power zoom in the second mode will cause the camera to move out of the competition focus range, it is possible to logically prohibit this.

To shift from the second mode to the first mode, manually rotate the zoom ring 3 and forcibly switch the signal of the zoom ring encoder 8, but it is also possible to provide a dedicated mode switching button. good.

Next, another embodiment of automatically shifting from the first mode to the second mode will be described.

Now, as shown in Figure 3, the subject is initially at a distance of 2 meters,
Assume that it is in focus.

Consider a case where this subject approaches the camera. Distance ring 2 rotates in the close direction and follows the subject, but when the subject is 1
If it approaches less than m, for example 0.5 m, the distance ring 2 will stop at the closest end, making mountain climbing operation impossible.

As described above, when it stops at the close end and detects that it is out of focus for a predetermined period of time, the system automatically shifts to the second mode. That is, the zoom ring 3 is moved to the competition focus range, and as shown in FIG. 4, a mountain climbing operation is performed using the competition focus.

In Figure 3, from position A ((), (B), (C))
Perform the following actions to reach position B. At this time, if you control the system to set distance ring 2 (front lens F) to the best edge while performing a mountain climbing motion with compensator C, the subject will be 1 m.
Even if the object is far away, focusing can be performed using the compensator C.

According to this embodiment, there is a first mode in which automatic focusing is performed continuously in a range from infinity to about 1 m, and a first mode in which automatic focusing is continuously adjusted in a range from infinity to just in front of the lens (for example, about 1 cm). In addition, the zoom ring encoder 8 can be extended to the macro area, and the zoom ring encoder 8 can also be used to detect the infinite end during macro focusing, detect the close end, and detect whether or not the macro shooting state is in progress. Since the automatic focus adjustment device is configured to be able to operate in the above-mentioned mode, it is possible to provide an automatic focus adjustment device with good operability, which does not require operation of a changeover switch when changing between the first mode and the second mode.

Furthermore, if there is no AP flaw signal in the second mode, the compensator C is moved to a normal focal distance of 3 m, etc., as in the normal case, as a measure against distance measurement failure.

Furthermore, if a power zoom operation is performed inadvertently in the second mode, there is an inconvenience that the power zoom operation goes out of the competition focus range, but in this embodiment, the detection can be confirmed from the signal from the zoom ring encoder 8, so the logic can be easily prohibited. Furthermore, if a power zoom operation is performed during the first mode, there is a risk that the lens will pass the wide end and enter the competition focus range, but this detection has also been confirmed from the signal from the zoom ring encoder 8. Therefore, it can be easily prohibited logically.

(Correspondence between the invention and the embodiments) In this embodiment, the zoom ring encoder 8 corresponds to the encoder of the present invention, and the AF circuit 14 corresponds to the detection means.

(Effects of the Invention) As described above, according to the present invention, there is provided a zoom encoder that indicates the focal length position of a zoom lens that extends to the macro area, and a signal from the zoom encoder that is used to determine the position at the infinity end during macro photography. A member for detecting the close end and detecting whether or not macro photography is being performed, and thereby detecting the infinite end or close end during macro photography and detecting whether or not macro photography is being performed. Because it also serves as a zoom encoder for detecting the focal length position of the zoom lens,
It becomes possible to easily automate the switching from normal automatic focus adjustment to macro area automatic focus adjustment, and improve the operability of the apparatus.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a functional explanatory diagram of the zoom lens shown in FIG. 1, and FIG. 3 is a diagram to help explain the operation of the embodiment of the present invention. FIG. 4 is a diagram showing the same change in the AF signal. 1...Zoom lens, 2...Distance ring,
3...Zoom ring, 6...Distance ring encoder, 8...Zoom ring encoder, 14...
...AF circuit.

Claims (1)

[Claims] (1) In an automatic focus adjustment device that performs focus adjustment based on a light flux that has passed through a zoom lens capable of macro photography, a zoom encoder that extends to the macro area and indicates the focal length position of the zoom lens; 1. An automatic focus adjustment device comprising: a detection means for detecting an infinity end or a close end during macro photography and detecting whether or not a macro photography state is in progress based on the signal.