JP2003005022A - Interchangeable lens and camera system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the speeding-up and the enhancement of the accuracy of autofocusing compatible. SOLUTION: This system possesses two focus detecting means and two actuators to make a lens perform focusing operation, and the lens is driven to a specified first range by a first focusing actuator according to the detected result by a 1st focus detecting means and driven to a specified second range by a second focusing actuator according to the detected result by a 2nd focus detecting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device such as a video camera or a still camera.

[0002]

2. Description of the Related Art Conventionally, there are a phase difference detection method and a contrast method as focus detection means for autofocus. The phase difference detection method divides the subject image incident through the shooting lens into two light fluxes, and detects the defocus amount and its direction by the positional deviation of the re-imaging position of the subject by the two split light fluxes. Since the lens extension amount is obtained from this defocus amount, there is an advantage that the detectable defocus range is wide. On the other hand, the contrast method captures the subject image incident on the image pickup unit through the image pickup lens, extracts the high frequency component, moves the lens, and searches for a position where the extracted signal becomes maximum,
In the final method, the image plane is brought to the in-focus surface, and it takes a long time to focus because the defocus amount and its direction are not known immediately, but there is a merit that high-precision focusing accuracy can be obtained. In, since the image sensor that photoelectrically converts the subject image can be used as it is as the focus detection unit,
High focusing accuracy can be obtained without the influence of the relative position accuracy between the focus detection unit and the image sensor.

In view of the respective merits of the above two focus detections, the two focus detection means are used together to speed up the focusing by the phase difference method, while the focusing operation is partially performed by the contrast method. , An invention that achieves more accurate focusing is disclosed.

[0004]

However, in the above-mentioned conventional example, although focus detection means for achieving both high-speed and high-precision autofocus is considered, the drive control of the lens accompanying it is considered. Not considered. For example, when driving a lens with a stepping motor, in order to achieve high accuracy, the feed amount of the lens driven in one step of the motor needs to be set to a minimum pitch determined by the focusing accuracy or less, Therefore, if the pulse rate is set so that the stepping motor is not out of step, the autofocus drive time becomes longer as the lens extension amount increases, and the autofocus speed cannot be increased. In other words, conventionally, although a focus detection method that achieves both high speed and high accuracy of autofocus has been presented, it cannot be realized without the lens drive control that realizes it.

(Object of the Invention) An object of the present invention is to use a plurality of focus detection means together in order to achieve both high-speed autofocus and high-precision autofocus, and to achieve both high-speed autofocus and high-precision autofocus. The purpose is to make it a reality.

[0006]

In order to achieve the above object, the present invention has two focus detecting means and two actuators for focusing a lens, and the first focus detecting means is provided within a first predetermined range. The second focus adjusting actuator drives the first focus adjusting actuator, and the second focus detecting means drives the second focus adjusting actuator within the second predetermined range.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the illustrated embodiments.

FIG. 1 is a sectional view of an interchangeable lens type digital single lens reflex camera showing an embodiment of the present invention.

An interchangeable lens 1 has a camera body 2 attached thereto. The camera body 1 and the interchangeable lens 2 are composed of the following components. Reference numeral 3 denotes a half mirror, which is on the optical axis of the light beam that has passed through the lens 2 before the start of shooting. A part of the light beam is divided into the image pickup unit and a part of the light beam into the finder optical system. Save. Reference numeral 4 denotes an image sensor, which forms an image of the light rays that have passed through the lens 2 during photography and photoelectrically converts the imaged subject image. It becomes a focus detection unit of the capture contrast method. The finder optical system is composed of 5 pentaprisms and 6 finder optical systems, and the pentaprism 5 splits a part of the incident light beam into the focus detection unit 7. The focus detection unit 7 is a condenser lens 7a that divides the incident light beam into two light beams.
And two separator lenses 7b that re-image the light rays,
This is a so-called phase difference method which is composed of a line sensor such as a CCD for photoelectrically converting the formed subject image and detects a Def amount which is a shift amount of a focus from a shift of the image formed on each line sensor. A focus lens 307 is driven in response to a focusing instruction. 9 is a focus lens 307
Is a lens barrel holding frame that holds the lens barrel 9 movably in the optical axis direction. Reference numeral 304 denotes a stepping motor which is a first actuator, the output shaft of which is a lead screw, which is held on the fixed portion of the lens 2 so as to drive the lens barrel holding frame 10 in the optical axis direction. A stepping motor 306 is a second actuator, and its output shaft is a lead screw and is fixedly held on the lens barrel holding frame 10 so as to drive the lens barrel 9 in the optical axis direction.

FIG. 2 is a block diagram of a lens interchangeable digital single lens reflex camera system according to the present invention.

In the figure, reference numeral 200 denotes a digital camera main body, 30
Reference numeral 0 indicates the interchangeable lens body.

Reference numeral 201 denotes a camera CPU composed of a microcomputer, which controls the operation of various devices in the camera body 200 as will be described later, and the lens body 30.
When 0 is attached, the lens CPU is connected via the camera contact 202.
It transmits and receives to and from 301. The camera contact 202 is composed of a signal transmission contact for transmitting a signal to the lens side and a power contact for supplying power to the lens side. Two
Reference numeral 03 denotes a power source SW means that can be operated from the outside, and is a switch for starting up the camera CPU 201 to supply power to each actuator and sensor in the system and enable the system to operate. Reference numeral 204 denotes a two-step stroke type release SW means that can be operated from the outside, and the signal thereof is input to the camera CPU 201. When the first stroke switch (SW1) is ON, the camera CPU 201 determines the exposure amount by the photometric means 205 and the focus detection by the first focus detection means 206 if the first stroke switch (SW1) is ON, according to the signal input from the release SW. Based on the output of the focus detection means, the focusing means in the lens, which will be described later, is controlled to perform the focusing operation, and the photographing preparation state is entered. When it is detected that the second stroke switch (SW2) has been operated to ON, the lens CPU 30 in the lens body 300
1 (which controls the operation of various devices in the lens body 300 as described later and also communicates with the camera CPU 201 via the lens contact 302 when mounted on the camera body 200) to a diaphragm operation command described later. Along with the transmission, an exposure start command is transmitted to the exposure unit 208, and the image pickup unit 209 photoelectrically converts the subject image formed on the image pickup element through the image forming optical system including the lens groups in the lens body. , Output the image signal. The image processing means 210 digitizes the image signal and compresses it, and the image recording means 21.
At 1, an image signal is recorded and stored in a recording medium such as a semiconductor memory such as a flash memory, a magnetic disk, an optical disk or the like. Reference numeral 302 denotes a lens contact (21 in FIG. 1), which is composed of a signal transfer contact for transmitting a signal from the camera side and a power contact for supplying power from the camera side. Reference numeral 303 denotes a first drive control unit, and reference numeral 305 denotes a second drive control unit, which are selected by a drive control selection unit in the lens CPU 301 according to a flowchart described later. A stepping motor 304 is a first focusing actuator,
The output shaft is a lead screw, which is drive-controlled by the first drive control means 303. Reference numeral 306 denotes a stepping motor which is a second focusing actuator, and like the stepping motor described above, the output shaft is a lead screw and is drive-controlled by the second drive control means 305. The lead of the lead screw of the stepping motor 304 has a larger relationship than the lead of the lead screw of the stepping motor 306, and is configured such that the stepping motor 304 performs coarse movement and the stepping motor 306 performs fine movement. A focus lens 307 is configured to be driven by both actuators of the stepping motor 304 and the stepping motor 305. A diaphragm device (12 in FIG. 1) 308 is driven by the lens CPU 301 in accordance with the diaphragm operation command transmitted from the camera CPU 201 as described above, and determines the aperture area.

In the above structure, the CPU 201 in the camera follows the flow chart described later to detect the focus by the first focus detecting means, and if the defocus amount is out of the first predetermined range, rotate the DC motor 304 at a high speed to focus. The lens 307 is driven at high speed until the defocus amount falls within the first predetermined range. After that, the focus is switched to the second focus detection means 305, and if the defocus amount is outside the second predetermined range, the focus lens 307 is driven by the stepping motor 306 and is driven to a position where the contrast within the second predetermined range is maximized. A highly accurate focusing operation is performed.

When the defocus amount is small from the beginning and is within the first predetermined range, the driving by the stepping motor 304 is omitted, and the stepping motor 306 moves the focus lens to a position where the contrast becomes maximum within the second predetermined range. The focusing operation of 307 is performed.

FIG. 3 is a flow chart showing the main operation of focus adjustment in the system shown in FIG.

First, the camera CPU 201 releases the release SW.
It is determined whether or not the SW1 signal of the means 204 has been generated (# 5001), and if so, the first focus detection means 2
Def calculation is performed by the phase difference method which is 06 (# 500
2) It is determined whether the calculated Def amount is within the first predetermined range (# 5003), and if it is outside the first predetermined range, #
To 5004, if it is within the first predetermined range, proceed to # 5005.
In step # 5004, the in-lens CPU 301 selects the first drive control means, and the stepping motor 304 rotates it at a high speed to drive the focus lens 307 by the amount corresponding to the calculated Def amount.

After the lens is stopped, the Def calculation is performed again by the phase difference method which is the first focus detecting means 205 (# 5002), and it is again determined whether the calculated Def amount is within the predetermined range ( # 5003), if it is outside the predetermined range, the operation proceeds to # 5004 again and the previous operation is repeated. If it is within the predetermined range, proceed to # 5005 to perform initial setting # 5
Proceed to 006. This initial setting is for extracting the high frequency component of the formed subject image, which is the focus detection of the contrast method described later, and setting the value of β for storing the maximum value to zero.

Next, the contrast type focus detection which is the second focus detection means 207 is started (# 5006), the high frequency component of the formed subject image is extracted and the maximum value is output (# 5007), Compare that value with β (# 500
8) If it is smaller than β, proceed to # 5011, otherwise proceed to # 5009. In # 5009, after β is updated to the maximum value, the second drive control unit selected by the lens CPU 301 causes the stepping motor 306 to move in the same direction as the driving direction of the focus lens 307 driven in # 5004 described above and the depth of focus width. The unit drive is performed by an amount corresponding to, and the process returns to # 5006. # If it proceeds to 5011, it is determined whether β has been updated, and if there is no update, it is considered to be abnormal #
Return to 5002. If β has been updated, it is determined that the maximum value of the peak has been exceeded, and the process proceeds to step # 5012, where the stepping motor 306 is driven in a unit corresponding to the depth of focus in the opposite direction to the end of focus adjustment. .

In the embodiment, the lens interchangeable type digital single lens reflex camera system is described, but the present invention is also applicable to a lens integrated type digital camera.

Further, although the first actuator and the second actuator are stepping motors in the embodiment, the present invention is not limited to this and may be a DC motor or an ultrasonic motor.

[0021]

As described above, the first focus detecting means has the two focus detecting means and the two actuators for focusing the lens, and the first focus detecting means brings the first focus into the first predetermined range. It is driven by the adjusting actuator and driven by the second focus adjusting actuator within the second predetermined range by the second focus detecting means. In addition, there is an effect that smooth focus adjustment can be performed by performing high-precision driving for fine adjustment at low speed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a lens barrel according to an embodiment of the present invention.

FIG. 2 is a block diagram of a lens interchangeable single-lens reflex camera system according to the present invention.

FIG. 3 is a flowchart showing the main operation of focus adjustment in the system shown in FIG.

[Explanation of symbols]

1 camera body 2 interchangeable lenses 3 half mirror 4 image sensor 5 penta prism 6 Finder optical system 7 Focus detection section 9 lens barrel 10 Lens barrel holding frame 304,306 Stepping motor 307 Focus lens

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02B 7/36 G02B 7/11 N G03B 13/36 C 17/14 D H04N 5/232 G03B 3/00 A // H04N 101: 00 G02B 7/04 E (72) Inventor Masatetsu Ishikawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Co., Ltd. (72) Seiichi Kashiwaha 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 in Canon Inc. (72) Inventor Shigeki Sato 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H011 AA03 BA21 BA31 BB04 CA16 CA21 CA26 2H044 BE03 BE09 BE14 DA01 DB03 DC02 DC10 DD13 DD18 2H051 AA00 BA02 BA47 DA02 FA04 FA09 FA38 FA41 FA47 2H101 EE08 EE22 5C022 AA13 AB28 AC42 AC54 AC69 AC74

Claims (5)

[Claims] 1. An automatic focus adjusting device having two different focus detecting means and two different focus adjusting actuators, wherein the first focus detecting means drives the first focus adjusting actuator within a first predetermined range. Then, the camera system is characterized in that the second focus detecting means drives the second focus adjusting actuator within a second predetermined range. 2. An automatic focus adjustment device having two different focus detection means built into a camera and two different focus adjustment actuators built into an interchangeable lens,
Driving by the first focus adjusting actuator to the first predetermined range by the first focus detecting means, and driving by the second focus adjusting actuator to the second predetermined range by the second focus detecting means. A camera system characterized by. 3. An automatic focus adjustment device having two different focus detection means built into a camera and two different focus adjustment actuators built into an interchangeable lens,
Driving by the first focus adjusting actuator to the first predetermined range by the first focus detecting means, and driving by the second focus adjusting actuator to the second predetermined range by the second focus detecting means. A camera characterized by. 4. An automatic focus adjustment device having two different focus detection means built into a camera and two different focus adjustment actuators built into an interchangeable lens,
Driving by the first focus adjusting actuator to the first predetermined range by the first focus detecting means, and driving by the second focus adjusting actuator to the second predetermined range by the second focus detecting means. Interchangeable lens featuring. 5. The camera system according to claim 1, wherein the first predetermined range includes the second predetermined range.