JPH022292A - Camera with automatic focus function - Google Patents

Abstract

PURPOSE:To attain smooth and natural focusing without eliminating need for decision of the moving direction of a focusing lens system at the start of the AF operation by mounting an infrared-ray unit forming a range finding system of the active system to a contrast detection AF camera. CONSTITUTION:A camera has an infrared ray(IR) range finding unit 60 forming the active system range finding system. In the simple IR unit 60, a near infrared ray is projected to an object through a illuminance lens 64 from a near infrared ray LED 62 and the reflected light from the object inputted through a detection lens 66 is received by a semiconductor position detection element PSD 68 split into plural blocks. The PSD 68 outputs a signal representing which block of the PSD 68 receives the reflected near infrared ray from the output 160 to the MPU 24. The MPU 24 collates the position information of the focusing lens system of the pickup lens 50 inputted at all times from the output 118 of the camera section 10 with the area information inputted from the output 160 of the simple unit 60 to decide the moving direction of the focusing lens system.

Description

[Detailed description of the invention] Technical field TECHNICAL FIELD The present invention relates to cameras, and more particularly to automatic focusing mechanisms thereof.

Background technology Cameras with automatic focus function (AF cameras), such as CC
Conventional AF cameras have a contrast detection AF mechanism that uses video signals obtained from image sensors such as D.
The high-frequency components of the video signal are sampled in a predetermined image area, integrated over a predetermined period, and the integrated value (1QCAF evaluation data) is compared with the previous AF evaluation data. The focusing lens of the optical system was driven to always achieve the best possible focus.

This A F 4j9. In the case of autofocus, there is no prior AF evaluation data to compare when the autofocus starts, such as when the camera is turned on or when the subject goes out of focus. Therefore, it was not possible to determine whether the optical system lens should be driven to close range or to infinity. Therefore, when the focusing lens is moved in any direction, the A at that time is
The system calculates F evaluation data, determines whether the direction of movement is a direction in which the AF evaluation data increases, and then adjusts the focus.

However, 1. With this method, when shooting a movie, the movement direction of the AF mechanism's lens is determined during shooting, and the resulting image changes are included in the shot video signal. , there was a problem that the image became unnatural.

Additionally, when there are both far and near objects in the area where the video signal is sampled, there is a problem in which, for example, even if you want to focus on the far object, the near object will be in focus. Ta.

OBJECTIVE OF THE INVENTION It is an object of the present invention to provide a camera that eliminates the drawbacks of the prior art and has an automatic focusing function that allows smooth and natural focusing operations and allows focusing on a desired subject. purpose.

DISCLOSURE OF THE INVENTION According to the present invention, an imaging lens for imaging a subject, an imaging means for converting light input through the imaging lens into a video signal, a sampling means for sampling the video signal for a predetermined period, and a A camera with an autofocus function, which has a calculation means for calculating at least the direction of focus adjustment of an imaging lens using a video signal, and a drive means for moving the lens necessary for focus adjustment according to the calculation result, is provided when the subject is the camera. includes a simple ranging means for detecting an approximate area in front of the
The direction in which the focus of the imaging lens should be adjusted is determined by referring to the approximate area projected by the projection device.

Further, according to the present invention, the simple distance measuring means of the camera described above includes:
The image forming apparatus may include an infrared unit having a light emitting unit that emits infrared rays toward the subject, and a light receiving unit that receives the infrared rays reflected by the subject and outputs a signal indicating an approximate area.

. Further, according to the present invention, the calculation means of the camera calculates at least the direction of focus adjustment of the imaging lens using a rising control method.

DESCRIPTION OF EMBODIMENTS Next, embodiments of a camera with an autofocus function according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, the configuration of an example of a video camera in which the camera with an autofocus function of the present invention is applied is shown. Infrared rays (IR) that make up the system
Δ11 distance unit) 60, contrast detection is performed using the video signal obtained by the solid-state image sensor 30,
A predetermined lens group of the optical system lens 50 is controlled by referring to the distance information obtained from the R unit 80.

The camera a1110 includes, for example, a solid-state image sensor 30 made of a charge transfer device such as a CCD that includes an imaging cell array 32 in which a plurality of imaging cells are arranged, and an optical system lens 50 that constitutes, for example, four groups of zoom lenses. The incident light from the subject passing through the system lens 50 is converted into a video signal. The converted video signal is separated into a luminance signal and a composite synchronization signal. The luminance signal after separation is output 102
The composite synchronization signal is output from the output 108 to the video signal processing circuit 12, and the composite synchronization signal is output from the output 108 to the synchronization signal processing section 16. Note that the luminance signal separated by one is the AF signal according to the present invention.
The signal is output to the mechanism, and is also output from the output 130 to other circuits such as the recording system.

Camera department lO again. It has a zoom motor 34 and a focus motor 38 for moving the zoom lens system and focusing lens system of the optical system lens 50, and each motor is driven according to control signals input from the output +24 and the output 128 of the motor control circuit 26.

The video signal processing circuit 12 includes a bandpass filter and a clamp circuit. The video signal processing circuit 12 extracts a high frequency component from the luminance signal input from the output 102 of the camera section 10, clamps the extracted high frequency component signal, and then outputs it from the output 104 to the A/D converter 14.

The A/D converter 14 outputs the output 10 of the video signal processing circuit 12.
The analog signal of the high frequency component input from 4 is converted into digital and output to the gate circuit 20.

On the other hand, the synchronization signal processing unit 16 outputs the output 10 of the camera unit lO.
The composite synchronization signal input from the vertical synchronization signal (Vsy
nc) and horizontal synchronization signal (Hsync).

Each signal after a minute a is output from the output 110 to the gate signal generation circuit 1. Note that these synchronization signals Vsync
and Hsync can be taken out directly from the camera unit 10, for example, if the camera unit 10 is equipped with a synchronization separator.

The gate signal generation circuit 18 is set with horizontal and vertical setting values of the image area processing shown in FIG. The scanning status of the screen scanning line by Vsync and Hsync will be compared. Based on the comparison result, a control signal for controlling the sampling timing in the gate circuit 20 is outputted to the output 112.

The gate circuit 20 has an AND gate circuit (not shown), and has an A/D input from the output 10B of the A/D converter 14.
The converted luminance signal is sent to the output 11 of the gate signal generation circuit 18.
According to the control signal input from 2, sampling is performed for a predetermined period. The sampled signal is output from the output 114 to the arithmetic circuit 22 .

The arithmetic circuit 22 integrates the sampled signal input from the output 114 of the gate circuit 20 for a predetermined period. The data after integration (AF evaluation data) is output from output 118 to M
It is output to PU 24.

Simple IR-L Knee/Toro 0 (t, near infrared! IaLE
D 82, a light emitting lens 64, a light receiving lens 66, and, in this embodiment, a semiconductor device detection element (PSD) 138 divided into eight blocks. The number of blocks to be divided is not limited to this, and may be plural. Near-infrared light is projected from the near-infrared LE[] 82 to the subject through the light-emitting lens 64, and is reflected from the subject and input through the light-receiving lens 66. PSD 138 receives the light. PSD 6
8, a signal indicating which block of the PS Ro 68 received the reflected near-infrared rays is transmitted from the output IEIO to the MPU.
24. This signal is used to determine the distance to the subject, and the distance is calculated by the MPU 24 based on a conversion value between each block of the PSD 88 and the distance, which is stored in the MPU 24 in advance.

It should be noted that the simple IR unit 60 is set so that, for example, an object existing within an area (3) approximately in the center of the screen 300 in FIG. 3 is to be measured. In addition, near-infrared LE
The near-infrared rays at D82 are periodically pulsed.

The position information of the focusing lens system of the imaging lens 50 is constantly input to the MPU 24 from the output 11B of the camera unit 10, and this information is stored in the focus position information table 24.
It is stored in a. The MPU 24 compares this with the area information input from the output 180 of the simple unit 60 and determines the moving direction of the focusing lens system.

The MPU 24 also uses the AF evaluation data input from the output 1113 of the arithmetic circuit 22 to perform time-series comparison calculations using the so-called hill-climbing servo method. According to the result of the comparison calculation in the mountain climbing servo method, the table 24 described above is
Determine the rotation direction and drive time (stopping point It of the focusing lens system) of the focus motor 36 that drives the focusing lens system with reference to a. When the zero rotation direction and drive time are determined, the control signal that controls the focus motor 3B is determined. is from output 12El to motor control circuit 2B
is output to.

The motor control circuit 26 is connected to the MPU 24 and the camera unit 10, and outputs a focus motor drive signal 1 according to the control signal υ input from the output 12B of the MPU 24.
Output to 28.

Here, the operation of the MPU 24 at the start of the AF operation of the camera shown in FIG. 1 will be described with reference to the flowchart in FIG. 2.

When the main power of the camera is turned on and the above-mentioned area information of the subject is input from the simple IR unit (IR unit) 80, the MPU
24 compares the focusing lens system position information stored in the focus position information table 24a with its area information (202). When the focus position of the focusing lens system corresponds to the subject area indicated by the area information, focus control is performed using the hill-climbing servo method using the AF evaluation data input from the arithmetic circuit 22 ( 20B).

In step 202, if the two do not correspond 71, the focus motor 36 is driven in a direction in which the focusing position of the focusing lens system corresponds to the subject area (204), and the process moves to step 206, where the mountain climbing servo method is used. Performs focus control.

As described above, according to this embodiment, when the focusing lens system is in an out-of-focus position at the start of the AF operation, it is easy to use! By using the subject area information input from the R unit 60, it is possible to move the focusing lens system toward a position where it is almost in focus before focusing control is performed using the hill-climbing servo method. Therefore, since there is no need to determine the driving direction of the focusing lens system at the start of focusing control using the mountain climbing reservo method, smooth and natural focusing operations can be performed. Note that these operations are not limited to when turning on the main power of the camera, but also during shooting when the focusing lens system changes from an in-focus state to an out-of-focus state due to movement of the subject, etc.
It is also done at the start of the action.

Furthermore, the camera of this embodiment can be advantageously used even when far and near objects coexist within the region I where the video signal is sampled. For example, in FIG.
An example is shown in which a distant object A, which is the target of photographing, and a close object B coexist in the sampling area 1 used for the F operation.

When a conventional contrast AF camera performs AF operation on a target subject A and a nearby subject B is mixed in as shown in Figure 3, for example, the ratio of the area occupied by subject B in sampling area 1 is Although it is smaller than that of subject A, depending on the contrast condition of subject B, the focus position by AF operation may be smaller than that of subject B.
Sometimes it moved to . However, in the camera of this embodiment, the camera is simply set almost at the center of one screen 300! Since priority is given to the AF operation for the subject within the ranging area II of the R unit 60, the e AF operation is performed for the target subject A without being affected by the subject B at a short distance. However, it goes without saying that when the subject B enters the distance measurement area II, the target of the AF operation shifts from the subject A to the subject B.

In this embodiment, the AF operation has been described, but in the case of a so-called zoom operation, the same operation as that of a normal zoom lens is performed. In this case, the MPU 24
The zoom lens system position information input from 0 and the focusing lens system position information are compared, and control signals for driving each lens system are output from output 122 and output 12B to motor control circuit 2B. . The motor control circuit 26 sends a zoom motor drive signal and a focus motor drive signal from outputs 124 and 128 to the camera unit 10 to drive the zoom motor 34 and focus motor 36. Such an operation realizes a zoom operation of the optical system lens 50.

In this embodiment, the camera with an autofocus function of the present invention is applied to a video camera, but it can also be applied to other cameras other than video cameras, such as an electronic still camera having a solid-state imaging device.

Further, in this embodiment, an infrared method is used as the simple distance measuring means, but other methods other than the infrared method, such as an ultrasonic method, may be used.

Effects According to the present invention, a contrast detection AF camera that performs automatic focus adjustment using high frequency components of a video signal,
Equipped with an infrared unit that makes up the active 3111 distance system, there is no need to judge the direction of movement of the focusing lens system when the AF operation starts, allowing smooth and natural focusing operations. .

In addition, even if there are both far and near subjects in the area where contrast detection is performed on the screen, priority is given to data from the infrared unit that measures the distance in the area set approximately in the center of the screen, so there is no influence from other subjects. It is possible to perform an AF-off operation on a target subject without being affected.

FIG. 3 is a diagram showing an example of an image when far and near objects are mixed in the area where the contrast detection of the camera of FIG. 1 is performed.

10° 22゜ 24° 26.

38° 50° 60° 62° 68° Explanation of symbols of main parts , camera section , arithmetic circuit , MPU , motor control circuit , focus motor , optical system lens , simple IR unit , near-infrared LED , semiconductor device detection element

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing an embodiment of a camera with an autofocus function according to the present invention. FIG. 2 is a flowchart showing an example of the operation of the MPU of the camera shown in FIG. 1. Patent applicant: Fuji Photo Film Co., Ltd. People Katori Roo Maruyama Takao Figure 2

Claims (1)

[Claims] 1. An imaging lens for imaging a subject; an imaging means for converting light input through the imaging lens into a video signal; a sampling means for sampling the video signal for a predetermined period; A camera with an autofocus function, comprising: arithmetic means for calculating at least the direction of focus adjustment of the imaging lens using a video signal obtained by the camera; and a drive means for moving the lens necessary for the focus adjustment according to the result of the calculation. In this case, the camera includes a simple distance measuring means for detecting an approximate area where the subject exists in front of the camera, and the calculating means refers to the approximate area detected by the simple ranging means. A camera with an autofocus function, characterized in that the direction in which the focus of the imaging lens should be adjusted is determined by adjusting the focus of the imaging lens. 2. In the camera according to claim 1, the simple distance measuring means includes a light emitting means that emits infrared rays toward the subject, and a signal that receives the infrared rays reflected by the subject and generates a signal indicating the general area. A camera with an autofocus function, comprising an infrared unit having a light receiving means for outputting light. 3. The camera according to claim 1 or 2, wherein the calculation means calculates at least the focus adjustment direction of the imaging lens using a hill-climbing control method.