JP3358639B2 - Camera focus control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a focus control method for an AF camera having a range finder adjusted to a magnification according to the type (angle of view) of an interchangeable lens and performing external distance measurement.

[0002]

2. Description of the Related Art A lens interchangeable range finder AF camera having a replaceable photographing lens, a range finder adjusted to a magnification corresponding to the type of the interchangeable lens, and adopting an AF passive distance measuring method is conceivable. In a normal single-lens reflex camera, light branched from a principal ray passing through an interchangeable lens is received by an AF sensor, AF information is calculated based on a phase difference or the like, and the interchangeable lens is driven to perform focusing. There is no need to obtain lens type information such as the focal length of the lens.

[0003]

However, the above-mentioned lens interchangeable range finder AF camera employs an external distance measuring method, and the amount of movement of the lens differs from the amount of rotation of the drive motor for each interchangeable lens. You need to get Another problem is how to accurately bring the lens to the in-focus position with respect to actual lens driving. SUMMARY OF THE INVENTION It is an object of the present invention to provide a focus control method that can accurately and quickly bring a focus position to a focus position in a lens replacement range finder AF camera.

[0004]

In order to achieve the above object, a focus control method for a camera according to the present invention is provided in a range finder camera with an interchangeable lens, wherein a lens type indicating the type of focal length of the lens is provided on the interchangeable lens side. signal
Is provided on the lens side , and further infinity than the infinity code pattern edge which is the infinity reference position of the lens.
To the initial lens position on the infinite code pattern
The brush of the infinity cord.
When the contact piece of the lens brush comes off from the turn edge
A lens reference position switch for turning off the camera is provided, and the camera has switching means for switching between the AF mode and the MF mode. The distance to the subject can be set arbitrarily by the focus dial for setting the distance independent of the lens, and the focus dial
Set value or enter the lens type signal and the distance information by the external ranging unit and arithmetic by, endless code pattern
It calculates the number of pulses from the edge to the in-focus position, and drives the lens is configured with a control circuit for the focusing control in accordance with the number of pulses issued calculated.

In addition, in the present invention, in addition to the above configuration, the lens type signal is indicated by a voltage value from the lens side, and the control circuit obtains focal length information of the lens by determining the voltage value. Have been. Further, in addition to the above configuration, the present invention further provides a flange-back adjustment circuit with a volume for outputting a voltage value for flange-back adjustment in the lens, and adjusts the volume to adjust the flange-back correction voltage for each lens. set the value, it reads the camera start-up time of the correction voltage value, the full
Set value by the focus dial or the external distance measurement unit
Distance information, the lens type signal, and the flange
The focus correction voltage value is input and calculated, and the focus control is performed by adjusting the flange back.

[0006]

According to the above arrangement, focus control can be performed at high speed and with high accuracy.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a perspective view showing the appearance of an interchangeable lens range finder AF camera employing a focus control method according to the present invention. A focus dial 4 is arranged at an end of the upper surface of the camera body 1. An AF / MF switching button 4a is provided at the center of the focus dial 4. By pressing the AF / MF switching button 4a, the AF
Mode and MF mode are switched, and the focus dial 4 is fixed in the AF mode. In the MF mode, the focus dial 4 is rotatable from close to infinity. In addition, a main switch 5 and a release button 6 are arranged on the upper surface of the camera body 1.

[0008] A range finder section 3 which is adjusted to a magnification corresponding to the interchangeable lens 2 and a passive distance measuring section 7 are arranged at an upper portion of the front of the camera. The passive distance measuring unit 7 obtains information on the light receiving position of the light from the subject incident from the reference side lens and the reference side lens whose optical axes are apart from each other by the base line, and calculates the distance to the subject. A camera-side electrical contact pin 9 is provided below the mount 22 of the camera body 1.
However, a lens driving coupler 8 is disposed on the lower right side. The interchangeable lens 2 is mounted on the mount 22 with the electric contact pad 24 and the coupler 21 (see FIG. 2) facing the camera-side electric contact pin 9 and the lens driving coupler 8, and rotates a part of the interchangeable lens 2 by a fixed angle. By fitting. Note that the parts without reference numerals in FIG. 1 are not directly related to the present invention, and the description thereof will be omitted.

FIG. 2 is a circuit diagram showing an embodiment of a focus control circuit according to the present invention. The CPU (control circuit) 12 performs arithmetic processing and the like for focus control and performs other necessary control for the camera. A sliding resistance substrate 11 is fixed to the axis of the focus dial 4, and a resistance pattern is formed on the upper surface of the sliding resistance substrate 11. A contact piece 23 is provided on the upper surface of the sliding resistance substrate 11, and in the MF mode, the sliding resistance value changes according to the amount of rotation of the focus dial 4 (setting of the distance to the subject). In the AF mode, a signal indicating AF is output.

FIG. 3 shows the relationship between the AF position of the focus dial and the voltage value output from the resistance value of the sliding resistance substrate 11 with respect to the MF from infinity to close proximity. A
At the position F, a voltage of _VA is output. V∞ the infinite position MF is, V _M is outputted at close range, CPU 1
Sent to 2. A lens-side circuit 18 is provided in the interchangeable lens 2. The lens side circuit 18 includes a lens type determination signal output circuit 18a and a flange back correction signal output circuit 18b as shown in FIG. The lens type determination signal output circuit 18a outputs a voltage corresponding to the focal length (angle of view) of the interchangeable lens. For example, a wide-angle lens,
Standard lens, a telephoto lens and outputs a voltage value of the pre when prepared to have a lens type determination signals of the respective lenses output circuit 18a respectively _{V S, V N, V T} .

Flange back correction signal output circuit 18b
Is composed of a flange-back adjustment circuit IC with a volume, and outputs a flange-back correction signal during focus control. The flange back is corrected by a coarse adjustment and a fine adjustment. The coarse adjustment is performed by a single lens, and is adjusted by a mechanical method such as washer insertion. The fine adjustment is performed with the flange back correction signal output from the flange back correction signal output circuit 18b, and the flange back correction signal is set by adjusting the volume at the time of lens assembly. Even for interchangeable lenses having the same angle of view, this flange back correction is adjusted individually.

The lens type determination signal and the flange back correction signal are sent to the CPU 12 via the lens-side electric contact pad 24 and the camera-side electric contact pin 9. CPU 12
Determines which type of interchangeable lens is attached based on the voltage value of the lens type determination signal, and reads lens information corresponding to the interchangeable lens from the nonvolatile memory 13.
The CPU 12 controls the number of motor drive pulses to bring the focus ring 20 from the infinite code pattern edge (see FIG. 6) to the in-focus position based on the ranging information, the lens information, and the flange back correction signal from the passive ranging unit 7 in the AF mode. Is calculated. In the MF mode, the number of motor drive pulses is similarly calculated based on distance information set by the focus dial 4 instead of distance measurement information from the passive distance measurement unit 7.

The CPU 12 controls the motor drive circuit 14 to rotate the motor 16. The rotation of the motor 16 is reduced by the reduction gear group 17, and the focus ring 20 is rotated via the lens driving coupler 8 and the coupler 21 to move the lens forward and backward. An encoder 15 is provided in the reduction gear group 17.
Is provided, and the encoder 15 outputs a pulse waveform shifted by １ ／ λ phase using a two-phase photocoupler. The direction of rotation can also be determined from the timing of the shift between the two pulse waveforms. The interchangeable lens 2 has a lens code board 1
9 is provided so that the lens brush contacts and slides on the code pattern of the lens code board 19 according to the rotation of the focus ring 20.

FIG. 5 is a schematic front view showing an embodiment of the lens code board. The lens code board 19 has an annular shape, a ground pattern 28 is formed along the annular portion, and a near-end code pattern 26 and an infinite code pattern 27 are formed in parallel at both ends of the ground pattern. . The lens brush 25 has two contact pieces 25a, 25
b are arranged side by side, and the contact piece 25b is
The contact piece 25a moves on the pattern so that it comes into contact with the nearest code pattern 26 and the infinite code pattern 27. A flange back correction signal output circuit 18b is provided on the lower right side of the annular portion.
However, a lens-side electric contact pad 24 is provided at a lower portion.

FIG. 6 is a diagram in which the pattern is extended linearly. This figure is a case where FIG. 5 is viewed from the back, and the close side code pattern and the infinity side code pattern are in opposite positions. This will be described below with reference to FIGS.
Infinite mechanical stop position A and closest mechanical stop position G
Is a mechanically stopped position where the lens brush 25 cannot move further outward. Lens start
The lens initial position B, which is the position, is a position where the lens first waits when performing focus control. Lens infinity
The infinite code pattern edge C, which is the reference position, is a position at which encoder pulses start counting. The optical infinity position D is a position where the lens is focused on the infinity position. The closest code pattern edge E indicates a fixed position before reaching the optical closest position F. Optical closest position F
Is a position where the lens is focused on the closest position.

The lens reference position SW is set at the lens brush 25
When the contact piece of the lens brush 25 reaches the infinite code pattern 27, the contact piece and the infinite code pattern 27 are electrically connected to each other to be turned on and infinite. A code signal is output. On the other hand, when the lens brush 25 reaches the close code pattern 26, the close code pattern is output. At the time of focusing, the lens is brought between the optical infinity position D and the optical closest position F.

FIGS. 7 and 8 are flow charts for explaining the focus control operation of the present invention. First,
When the main switch 5 is turned on, the control circuit in the camera is activated (S ₁ ). When the main switch 5 is turned on, the CPU 12 starts the control operation. CPU12 lens lock switch (not shown) is turned on or not is determined (S _2). When no interchangeable lens is attached, the lens lock switch is not turned on. When the lens lock switch is determined to be ON state, the lens reference position switch is turned on or not is determined (S _3). When the lens reference position switch is ON, it is determined that the lens brush 25 has stopped at the lens initial position B. In this case, S
_It will go to ₇ . However, when the lens reference position switch is off, the CPU 12 controls the motor drive circuit 14 to rotate the motor 16 in the infinite direction because the lens reference position switch is at a position apart from the infinite code pattern 27 (S ₄ ).

Then, it is determined whether or not the lens reference position switch has been turned on (S ₅ ). When the lens reference position switch is turned on, the lens driving is stopped (S
₆ ). As a result, since the lens brush 25 is brought into the lens initial position B, then the process proceeds to S _7. In S ₇ CPU
12 reads the interchangeable lens corresponding voltage value from the lens type determination signal output circuit 18a, to determine which type of the interchangeable lens than the voltage value (S _7). Based on the determination result, and accesses the non-volatile memory 13, it reads the lens corresponding lens information (S _8). Then taking the voltage value of the flange back correction signals from the flange-back correction signal output circuit 18b (S _9).

The CPU 12 calculates an infinite position adjustment amount pulse number for adjusting the infinite position with respect to the optical infinity position D from the lens information and the voltage value of the flange back correction signal (S ₁₀ ). This adjustment amount range is within the range of the flange back adjustment width 29. Then the release button 6, it is determined whether the pressed for photography (S _11). Where A
If the AF mode is designated by the F / MF switching button 4a, the distance measuring information is sent from the passive distance measuring unit 7 and the CPU
12 and calculates the distance to the object (S _12). And
The number of lens drive pulses up to the in-focus position is calculated based on the infinite code pattern edge (infinite reference) C (S ₁₃ ), and S ₁₀
In adding the lens drive pulse number calculated in infinite position adjustment amount pulse number and S ₁₃ calculated (S _14). The number of added pulses is the number of pulses up to the focus position.

The CPU 12 controls the motor drive circuit 14 to drive the motor in the closest direction (S ₁₅ ), and detects the position where the lens reference position switch is turned off (S ₁₆ ). That is, the infinite code pattern edge C is detected. Upon detection of the infinite code pattern edges C, and starts counting the number of pulses sent from the encoder 15 from the time (S _17). While continuing to count the number of pulses by comparing the number of pulses of the count value from the pulse count and the encoder calculated in S _14, to detect whether they match (S _18). If it matches to stop counting pulses to stop the driving of the motor _{16 (S 19) (S 20} ). With the above, the lens is brought to the in-focus position,
After the shutter control is made, the process returns to S _1, operation is executed to S ₁₀ again. Although receiving distance information from the passive distance measuring unit 7 when the S ₁₂ AF mode, and thus obtaining distance information set by the focus dial 4 when the MF mode.

[0021]

As described above, according to the present invention,
In the lens interchangeable range finder AF camera, there is an effect that a focus control method capable of accurately and quickly bringing a focus position to a focus position can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of an interchangeable lens rangefinder AF camera employing a focus control method according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of a focus control circuit according to the present invention.

FIG. 3 is a diagram showing a relationship between a focus position by a focus dial and a voltage.

FIG. 4 is a circuit diagram showing details of a lens-side circuit.

FIG. 5 is a schematic front view showing an embodiment of a lens code board.

FIG. 6 is a diagram showing a positional relationship when the lens code pattern of FIG. 5 is extended in a linear direction.

FIG. 7 is a flowchart illustrating an operation from when a main switch is turned on until a release button is pressed.

FIG. 8 is a flowchart illustrating an operation from when a release button is turned on until shutter control is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Camera main body 2 ... Interchangeable lens 3 ... Finder part 4 ... Focus dial 5 ... Main switch 6 ... Release button 7 ... Passive distance measuring part 8 ... Lens drive coupler 9 ... Camera side electric contact pin 10 ... Lens detachable button 11 ... Slide Dynamic resistance board 12 CPU (control circuit) 13 Nonvolatile memory 14 Motor drive circuit 15 Encoder 16 Motor 17 Reduction gear group 18 Lens circuit 19 Lens code board 20 Focus ring 21 Coupler 22 Mount 24 ... Lens side electrical contact pad 25 ... Lens brush 26 ... Nearest code pattern 27 ... Infinite code pattern 28 ... Ground pattern 29 ... Flange back adjustment width 30 ... Focus range

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Oda 2-14-9 Tamagawadai, Setagaya-ku, Tokyo Kyocera Corporation Tokyo Yoga Office (72) Inventor Takakazu Kobayashi 2-14 Tamagawadai, Setagaya-ku, Tokyo No. 9 Kyocera Corporation Tokyo Yoga Office (72) Inventor Masao Tsujimura 2-14-9 Tamagawadai, Setagaya-ku, Tokyo Kyocera Corporation Tokyo Yoga Office (56) References JP-A-57-195223 (JP, A) JP-A-63-70834 (JP, A)

Claims (3)

(57) [Claims] 1. An interchangeable lens range finder camera, wherein a lens side circuit for outputting a lens type signal indicating a type of a focal length of the lens is provided on an interchangeable lens side,
And the infinite code pattern
On the infinite code pattern located further infinity than the edge
Bring the contact piece of the lens brush to the initial position of the lens
From the edge of the infinite code pattern
Lens reference position that is turned off when the contact strip comes off
A switch is provided, and the camera has switching means for switching between the AF mode and the MF mode. In the AF mode, information on the distance to the subject is obtained by an external distance measuring unit. In the MF mode, the distance is set independently of the lens. It was arbitrarily settable the distance to the object by focusing dial for, measurement set value or the external by the focusing dial
And Starring <br/> calculated by entering the lens type signal and due to the distance information距部, calculates the number of pulses from an infinite code pattern edge to the in-focus position, the lens is driven according to the number of pulses issued calculated focus control A focus control method for a camera, comprising: 2. The camera according to claim 1, wherein the lens type signal is indicated by a voltage value from a lens side, and the control circuit obtains focal length information of the lens by determining the voltage value. Focus control method. 3. A lens-mounted flange-back adjusting circuit for outputting a voltage value for flange-back adjustment in a lens, and adjusting the volume to set a flange-back correction voltage value for each lens. ,
When the camera is started, the correction voltage value is read, and the focus value obtained by inputting the set value by the focus dial or the distance information by the external distance measuring unit, the lens type signal, and the flange back correction voltage value is calculated, and the flange back is adjusted. 3. The control according to claim 1, wherein the control is performed.
The focus control method of the camera described.