JPS63261212A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To obtain a proper focusing speed corresponding to photographic conditions by making a focusing speed fast if an object distance measurement range of switching is small when a video camera is operated on an automatic focus basis, and making the focusing speed faster than an automatic focusing speed when automatic focusing is selected in manual focusing mode. CONSTITUTION:An image of a subject 1 is recorded on a video tape through an image pickup lens 2, a CCD 4, etc. An AF interface 7, on the other hand, finds a focusing position by detecting a phase difference from diffracted light from a half-mirror 3 and controls a driving motor 10 through a control circuit 8 to move a lens 2. At this time, the circuit 8 is provided with a multi-stage distance measurement range changeover switch 11 and the focusing speed is made fast when the distance measurement range is narrow. Further, the circuit 8 is provided with an automatic/manual focusing switch 12 and when a one- punch automatic SW13 is turned on in manual focusing mode, focusing is performed faster than the automatic focusing. Consequently, the focusing is performed at the proper speed corresponding to the photographic conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an autofocus device capable of quick autofocus (hereinafter referred to as autofocus).

<Prior Art> Unlike still cameras, autofocus devices in video cameras cannot achieve very high autofocus speeds. This is because if something other than the subject crosses the viewfinder during shooting, the faster the focusing speed will cause the focusing distance to change accordingly.

<Problems to be Solved by the Invention> Various types of automatic focusing devices have been proposed, but among these, one that has a function of switching the size of the distance measurement range in the finder is known. ing. For example, an autofocus method uses the fact that the high-frequency component of the video signal is at its maximum when the image is focused, or a separator lens is used to separate the light beam into left and right sides.
These methods include a method (so-called phase difference detection method) in which the in-focus position is determined by correlation of electrical signals of images projected onto a charge-coupled device (D) and extracted from pixels of the COD.

When a photographer selects a narrow distance measurement range using these methods, he or she wants to reliably autofocus on a subject within a narrow range, so it would be convenient if autofocus could be done quickly.

However, in the past, there was no device that changed the focusing speed depending on the size of the distance measurement range.

In addition, autofocus devices in video cameras perform continuous autofocus, but manual focusing (hereinafter referred to as "manual focusing") involves canceling autofocus and manually moving the shooting lens.
It is common to be able to switch to manual focus (also called manual focus). Furthermore, even when using manual focus, the shooting lens may have been moved manually.
Since this may not be possible in time, a switch is often added that allows you to select temporary autofocus. For example, there are known types that perform autofocus as long as the switch is held down, and types that perform autofocus once the switch is pressed until the subject in the viewfinder is brought into focus.

However, when selecting ~-temporary autofocus during manual focus, the focusing speed was no different from that during continuous autofocus, even though quick focusing is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic focusing device that can change focusing speed in accordance with photographing conditions.

Means for Solving the Problems〉 The configuration of the automatic focusing device of the present invention to achieve such an objective is an automatic focusing circuit that focuses on a subject within a distance measurement range by moving a photographing lens. A video camera or the like equipped with a switch for changing the distance measurement range, a circuit for changing the moving speed of the photographing lens to a higher speed as the distance measurement range switched by the circuit is smaller, and continuous automatic focusing by the autofocus circuit. a switch for switching between focusing and manual focusing in which the photographing lens is manually moved; a switch for selecting temporary automatic focusing by the automatic focusing circuit during manual focusing; and a switch for selecting temporary automatic focusing by the automatic focusing circuit during manual focusing; The camera is characterized by including rHI#t for switching the moving speed of the photographic lens faster than continuous automatic focusing.

Effect> When the distance measurement range is changed to a smaller value, the focusing speed becomes faster, and conversely, when the distance measurement range is changed to a larger value, the focusing speed becomes slower.

On the other hand, when temporary autofocus is selected during manual focus, the focusing speed becomes faster than continuous autofocus.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

An embodiment of the present invention is shown in FIGS. 1 and 2. FIG. As shown in both figures, the image of the subject 1 passes through the photographic lens 2 and the half mirror 3, is converted into an electrical signal by the C0D4, and is then recorded on a videotape (not shown) through signal processing [t5]. There is.

On the other hand, the light beam refracted by the eight-familar mirror is
The line sensor 6 is reached, and the AF interface 7 determines the in-focus position using a phase difference detection method. The control circuit 8 controls the lens drive motor 10 via the motor drive circuit 9 based on the determined focus position.

Here, the above IIIi! A ranging range changeover switch 11 is connected to the 1 circuit 9. This distance measurement range changeover switch 11 is capable of changing the size of the distance measurement range in the finder in several stages, and the in-focus position of a subject within the distance measurement range is determined.

Normally, when a photographer switches to a narrow distance measurement range, it is presumed that he or she wants to reliably focus on that range, so quick autofocus is desirable. Therefore, in this embodiment, the control circuit Ig758 includes a circuit that changes the moving speed of the photographing lens 2 to a higher speed as the distance measurement range becomes smaller. Therefore, in response to switching the distance measurement range,
Appropriate focusing speed can be obtained. Also, when the distance measurement range is wide, if something other than the subject crosses the subject,
Focusing is performed with an appropriate time constant so that the focusing distance does not change accordingly.

Further, as shown in FIG. 2, connected to the control device 8 are a switch 12 for switching between autofocus and manual focus, and a one-button auto switch 13 for temporarily selecting autofocus during manual focus. Temporary autofocus is required during manual focus when rapid autofocus is required, such as when suddenly focusing on a nearby object while photographing a distant object. Therefore, in this embodiment, when temporary autofocus is selected in the control circuit 8 during manual focus, the moving speed of the photographing lens 2 is set higher than when continuous autofocus is selected. Therefore, when autofocus is temporary, quick focusing is performed.

In the above embodiment, a phase difference detection method is used to determine the focus position, but the invention is not limited to the above embodiment as long as it is an automatic focusing method that can switch the distance measurement range. In addition, the above-mentioned CCD is used to convert the image of the subject into an electrical signal.
4, other solid-state imaging elements may be used.

<Effects of the Invention> As explained above in detail based on the embodiments, the present invention can be used in a wide variety of situations, from beginners to advanced users, since it is possible to set an appropriate focusing speed depending on the shooting conditions. You can use various techniques to take pictures the way you want.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are block diagrams each showing an embodiment of the present invention. In the drawings, 1 is the subject, 2 is the photographic lens, 3 is the half mirror 1, and 4 is the COD. 5 is a signal processing device, 6 is a COD line sensor, 7 is an AF interface, 8 is a printing unit circuit, 9 is a motor drive circuit, 10 is a lens drive motor, 11 is a ranging range changeover switch, 12 is an autofocus-manual focus 13 is a one-button auto switch.

Claims (1)

[Claims] In a video camera, etc. equipped with an autofocus circuit that focuses on a subject within the distance measurement range by moving the photographic lens, there is a switch that switches the distance measurement range, and the smaller the distance measurement range switched by the circuit, the smaller the distance measurement range switched by the circuit. a circuit for switching the moving speed of the photographic lens to high speed; a switch for switching between continuous automatic focusing by the autofocus circuit and manual focusing for manually moving the photographic lens; It is characterized by comprising a switch for selecting temporary automatic focusing by a focusing circuit, and a circuit that changes the moving speed of the photographing lens to be faster in the case of temporary automatic focusing than in continuous automatic focusing. Automatic focusing device.