JPH0521052Y2 - - Google Patents

Description

[Detailed explanation of the invention] (Technical background) Cameras with built-in automatic focusing devices have already become everyday tools, but recently single-lens reflex cameras are also capable of high-performance, high-speed focusing. A camera is appearing.

One of the advantages of single-lens reflex cameras is that lenses can be replaced, but if you attach a telephoto lens to the camera body and try to take handheld shots, the focus information detected by the focus detection device will be lost due to camera shake. This resulted in the problem that it was difficult to focus on the subject.

That is, when camera shake or the like occurs, it is difficult to keep the original subject within the distance measurement field of view, and other objects may enter the field of view. Under such a situation, even if focusing is performed according to the distance measurement result, it will not be possible to focus on the original subject.

[Purpose] The present invention was developed in view of the above matters, and includes a focus detection circuit that has a sensor that receives light flux from a subject, performs focus detection based on the output of the sensor, and forms a focus signal, and the detection circuit. In a camera equipped with an autofocus device having a drive circuit that drives a photographic lens based on a focus signal from A detection circuit and a prohibition circuit that prohibits the drive circuit from driving the photographing lens based on the focus signal from the detection circuit when the amount of camera shake detected by the camera shake is equal to or greater than a predetermined amount are provided. This is intended to prevent focusing on objects other than the subject.

(Example) An example of the present invention will be described below with reference to the drawings. In the figure, 1 is a positive power focusing lens, 2A is a variator, 2B is a compensator,
Reference numeral 3 denotes a relay lens, and these lenses constitute an exchangeable zoom lens, and the variator 2A and compensator 2B move in a predetermined relationship to realize zooming. A lens driver 4 moves the focusing lens 1 via a coupling member to adjust the focus of the zoom lens. 5 is a rotary encoder,
It is coupled with a lens driver 4 to indirectly detect the position of the focusing lens 1. A linear encoder 6 is coupled to, for example, a variator lens to indirectly detect the focal length of the zoom lens. In this example, the lens driver 4, rotary encoder 5, and linear encoder 6 are shown as being housed in the lens barrel, but they can be modified to be housed on the camera body side and detected via a relay member. It's okay. Also, if the lens is a short focus lens,
When a lens is replaced, its focal length is detected.

On the other hand, on the camera body side, 10 is a quick return mirror, 11 is a submirror, and the submirror 11 is swingably coupled to the quick return mirror 10. 12 is an image receiving surface of a silver halide film or a video solid-state image sensor. 13 is a condenser lens, 14 is a pentagonal prism, and 15 is an eyepiece. 16 is a field lens arranged on the image formation plane; 17 is a secondary imaging system that forms a plurality of images with suggestions; 18 is a focus detection element equipped with a sensor array that receives a plurality of images; and 19 is a focal point. The error detection circuit detects the phase difference of the image from the photoelectric conversion signal of the focus detection element 18, and outputs information corresponding to the amount of out-of-focus. Note that the focus detection method may be any other method.

Reference numeral 20 denotes an acceleration detection element that is characteristic of this example, and is preferably arranged near the image receiving surface 12. For example, a gravimeter commonly used in vibration measurement is effective as the acceleration detection element 20. An example of a gravimeter measures acceleration by utilizing the property that when a mass point is completed, a mass point holder is deflected, and a strain gauge attached to the surface of the holder expands and contracts, changing the resistance surface.

21 is an image blur detection circuit, and an acceleration detection element 20
The signal applied to the image receptor is detected from the output of the image receptor. The amount of blur of the image on the focus detection element changes depending on the focal length of the optical system that reaches the focus detection element 18. For example, if the focal length is doubled, the amount of image movement will be approximately doubled due to rotational blur. That is, in addition to evaluating the vibration level, at least the focal length must also be considered.

Note that members numbered 16 or less may be provided on the lens barrel side. 22 is a focus adjustment calculation circuit;
It has a function of calculating the amount by which the focusing lens 1 should be moved based on the out-of-focus amount of the focus error detection circuit 19 and the current focal length information from the linear encoder 6. The calculation result is input to the drive control circuit 24 via the gate circuit 23, and the driver 4 is operated to move the focusing lens 1. The position of the focusing lens 1 is constantly measured by a rotary encoder 5 and fed back to the drive control circuit 24.

Reference numeral 25 denotes an adjustment discrimination circuit that uses vibration information during focus detection detected by the image blur detection circuit 21, focal length information from the linear encoder 6, and more preferably sampling required for detection obtained from the focus error detection circuit 19. If the evaluation value determined by the time information is less than a certain value, focus adjustment is allowed; if it exceeds this value, the gate circuit 23 is closed, and the calculation result of the focus adjustment calculation circuit 22 is input to the drive control circuit 24. The focus detection is performed again.

The circuit configuration diagram in FIG. 2 shows a specific configuration of the discrimination circuit 25. 25A designates memory means M ₁ ;
The memory means converts the allowable amount of image blur for each focal length of the zoom lens into a signal and outputs each corresponding comparison signal according to the focal length information.
It consists of ROM (Read Only Memory), etc.

The focal length information is obtained by converting the positional information of the zoom lens 2A into focal length information using the information from the linear encoder 6.

Reference numeral 25B denotes a first comparing means, which compares the output signal of the information 21a of the shake detection circuit and the output signal of the memory _M1 .

In the above configuration, if there is no vibration, the operation is as follows. The amount of movement of the focusing lens 1 calculated by the focus adjustment calculation circuit 22 from the out-of-focus amount detected by the focus error detection circuit 19 based on the output of the focus detection element 18 and the current focal length information from the linear encoder 6. Information is transmitted to the drive control circuit 24 via the gate circuit 23.

The focusing lens 1 is moved by the output of the drive control circuit 24, and the lens movement amount detected by the encoder 5 is fed back, and when a predetermined movement amount is reached, the power to the driver 4 is cut off.

Here, detection is performed again to confirm that the detected amount is within the permissible range, and if it is not within the permissible range, the above operation is repeated until the object is in focus.

If there is vibration, the focal length information based on the output signal of the linear encoder 6 will be stored in memory M1, ₂ .
5A and the image blur amount information from the image blur detection circuit 21 is sent to the first comparing means 25B.

A comparison signal corresponding to the focal length information is outputted from 25A of the memory _M1 and is compared by the first comparing means. If the amount of image blur is smaller than the comparison signal, it is determined that the amount of image blur does not adversely affect the focus adjustment operation with respect to the focal length information, and the lens movement information calculated by the focus adjustment circuit 22 is sent to the drive circuit via the gate 23. 24.

If the amount of image blur is large relative to the focal length information,
For example, considering the case of a short focal length zoom and the case of a long focal length zoom, for the same amount of image blur, the short focal length has a smaller effect on the focusing operation than the long focal length. Therefore, when there is no adverse effect as in the case of short focal length zoom, the comparing means 25C outputs a signal to open the gate 23.

In the case of a long focal length zoom, even a small amount of image blur can have a large effect on the focusing operation depending on the zoom ratio. Arithmetic means 22
Since it is difficult to obtain a correct state even if the lens 1 is moved by the signal of the gate 2
Outputs a signal to close 3.

(Effects) As described above, in the present invention, since focusing is prohibited during camera shake, unnecessary focusing can be prevented in cases where it is difficult to keep the original subject in the distance measurement field of view.

Applications such as outputting a blur warning by using the image blur signal are also possible.

[Brief explanation of drawings]

FIG. 1 shows an overall configuration diagram of a focus adjustment device according to the present invention, and FIG. 2 shows a specific configuration diagram of a discrimination circuit 25. As shown in FIG. 25A...Multiplication circuit, 25B...Storage means, 2
5C...Means of comparison.

Claims (1)

[Scope of utility model registration request] It has a sensor that receives light flux from the subject,
In a camera equipped with an autofocus device that has a focus detection circuit that performs focus detection and forms a focus signal based on the sensor output, and a drive circuit that drives a photographic lens based on the focus signal from the detection circuit, vibration an acceleration detection means for detecting the state; a shake detection circuit for detecting the amount of shake based on the output of the acceleration detection means; and a focus signal from the detection circuit when the amount of shake detected by the shake detection circuit is greater than or equal to a predetermined amount. A camera characterized by being provided with a prohibition circuit that prohibits a driving circuit based on a signal from driving a photographing lens.