JPH0795137B2 - Focus correction device for camera with zoom lens - Google Patents

Description

The present invention relates to a focus correction apparatus for a camera with a zoom lens, and more specifically, in a camera with a zoom lens having a non-TTL distance measuring means, the variation is caused by each lens. The present invention relates to a focus correction device that corrects a focus shift.

[Prior Art] In a camera with a zoom lens that performs focus control by an inner focus method, the extension position of the rear lens group is different if the focal length is different even if the subject distance is the same.
The amount of lens extension must be changed according to zooming. Therefore, the applicant stores the respective curves of the lens extension amount at infinity (∞) at each focal length and at the closest distance, and divides the curve from ∞ to the closest distance into 64 to obtain the focal length and the subject. We proposed a focus adjustment device that calculates the amount of lens extension from each distance data (Japanese Patent Application No. 61-128745).

[Problems to be Solved by the Invention] However, in reality, since the camera causes variations during lens assembly or the dimensions of lens parts themselves vary, if the calculation result of the above-mentioned feed amount is used as it is. Especially, there is a possibility that out-of-focus shooting may be performed with a lens having a longer focal length.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a focus correction device for a camera with a zoom lens, which stores such variations from the reference position of the camera lens for each one and corrects the lens extension amount.

[Means and Actions for Solving the Problem] In the focus correction apparatus for a camera with a zoom lens according to the present invention, as shown in FIG. 1, the object distance information obtained from the non-TTL distance measuring means 1 and the set focus are set. The amount of movement of the focusing lens from the reference position is calculated based on the distance information. On the other hand, a difference from the above-described calculated movement amount, which is generated at the time of assembling the lens or due to a variation in the lens component size, is stored in the storage means 2 in correspondence with each focal length. Is input to the calculation means 3, the values between the plurality of stored values are interpolated by the calculation means 3.
Then, the focusing lens is driven by the lens driving means 4 based on the final movement amount obtained by adding the value calculated by interpolation to the calculated movement amount from the reference position.

[Example] First, a basic system of a zoom lens camera to which the present invention is applied will be described with reference to FIG. A CPU (Central Processing Unit) 11 is composed of a one-chip microcomputer that controls the entire camera, a basic clock is input from an oscillation circuit 12, and an operation is started by resetting a reset circuit 13. The reset circuit 13 operates when a battery is inserted and a power switch (not shown) is turned on and off.

The E ² -PROM 14 is a non-volatile memory that stores the camera status (number of frames, winding, etc.) and adjustment data (shutter control, lens drive). Therefore, the camera can return to the previous state even if the battery is removed. In addition, E ² -PROM14 is,
As will be described later, the deviation amount of the lens extension amount caused by the variation for each lens is stored. While the E ² -PROM14 writing the data reset operation of the reset circuit 13 is inhibited. When you read mode E ² -PROM14,
First, the DX code is input to the E ² -PROM 14 from the DX terminal 15, and then input to the CPU 11 via the serial line. After that, the data of the E ² -PROM 14 is input to the CPU 11.

AFIC16 is a phase-difference AF that is provided at a non-TTL range-finding position.
(Auto focus) sensor, the distance data is CPU1
Sent to 1. The CPU 11 lights the auxiliary light lamp 17 in accordance with the operation of the AFIC 16 when the photometric value is below a certain value (dark). The EXT terminal 18 is a connection terminal with an external device, and is connected with an option, an automatic adjuster, or the like. E ² -PROM14, AFIC16
The EXT terminal 18 and the EXT terminal 18 are connected to the same serial line in order to effectively use the port of the CPU 11, and exchange data with the CPU 11 by serial communication.

SW19 is a camera operation switch, and includes a release switch and mode switch. LED20 is a light emitting diode in the viewfinder, and includes a light emitting diode for strobe light emission notice, focus display, and the like. The LCD 21 is a liquid crystal display panel for displaying the number of frames, camera mode, and the like. IF
The IC 22 is an interface IC that has a decoding function for performing photometry with the photometry unit 23 and selecting a motor in the camera according to a command from the CPU 11.

M _S 24, M _W 25, and M _Z 26 are a shutter motor, an upper winding / rewinding motor, and a zoom motor, respectively, which are driven by a decode signal of the IFIC22 via a motor driver IC27. The M _S 24 drives the lens during forward rotation and drives the shutter during reverse rotation.
When the lens is driven, the reset position of the lens is confirmed by the ON (closed) state of the switch 28, and the control position is confirmed by the pulse number of the photo interrupter 29. At the time of driving the shutter, the reset position is confirmed by turning on the switch 30, and aperture control is performed by adjusting the pulse width of M _S 24. This adjustment value is stored in the E ² -PROM 14.
The M _W 25 winds the film in the forward direction and rewinds it in the reverse direction. The single frame feed control of the film is performed by counting the number of pulses of the photo interrupter 31. The photo interrupters 29 and 31 are turned on only when M _S 24 and M _W 25 are selected, and the photo interrupter output is input to the CPU 11 via the IFIC 22. The zoom position of M _Z 26 can be detected by the zoom encoder 32.

DATEM33 is a date module that prints data such as date and time on film, and STRB34 is a strobe.

Here, the zoom encoder 32 will be described. As shown in FIG. 3, the zoom encoder 32 includes a thin film conductor pattern integrally provided on the outer peripheral surface of the zoom ring 40, a conductive contact piece slidably contacting the conductor pattern, a resistor group, and the like. It is composed by. When the M _Z 26 (see FIG. 2) rotates, the zoom ring 40 rotates, and the cam (not shown) in the zoom ring moves the zoom lens back and forth to change the focal length. The focal length is obtained by detecting the position of the zoom encoder 32 on the zoom ring 40.

Eight contact pieces for detecting the position of the zoom encoder 32
T ₀ through T ₇ is attached to a fixed frame 41, respectively CPU1
One ground terminal AD _GND and one end of each of the resistors R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , and R ₇ . The value of the resistance is (R ₁
It is set such that / R ₂ ) = (R ₃ / R ₄ ) = (R ₅ / R ₆ ) = 1.67. The other ends of the resistors R ₁ and R ₂ are connected to each other
It is connected to the A / D conversion pin AD _ZMA of U11. Resistors R ₃ and R
The other end of ₄ is also connected to each other and the A / D conversion terminal AD _{ZMB of} CPU 11
The other _ends of the resistors R ₅ and R ₆ are similarly connected to the A / D conversion terminal AD _ZMC . The other end of the resistor R ₇ is connected to the terminal AD _Vref to which the reference voltage Vref of the CPU 11 is applied. In the unlikely event that this resistor R ₇ has a reference voltage Vref of ground terminal G
It is a protection resistor when short-circuited to ND.

The conductor pattern of the zoom encoder 32 is developed and shown in FIG. The eight contact piece T conductive pattern P ₀ which contact piece T ₀ and T ₇ at both ends in sliding contact with each of ₀ through T ₇ and P ₇
Is formed of a conductor that is continuous over the entire zoom region along the circumferential direction of the zoom ring 40, and is provided with the ground potential GND and the reference voltage Vref, respectively. The patterns P _{1 to} P ₆ in each row with which the contact pieces T _{1 to} T ₆ contact each other are each made of a conductor formed in a discontinuous shape in the circumferential direction of the zoom ring 40 as illustrated. The patterns P _{1 to} P _{6 in} each column are electrically connected to the conductive pattern P ₀ partially as shown in the drawing, and the electrode pattern P to which the ground potential GND is applied.
_G (indicated by a fine diagonal line on the upper right side), and an electrode pattern P _V (indicated by a coarse diagonal line in the lower right direction) connected to the conductive pattern P ₇ and applied with the reference voltage Vref,
It is composed of an electrodeless portion where none of the electrode patterns exists. Therefore, by rotating the zoom ring 40,
When the contact pieces T _{1 to} T ₆ slide on the patterns P _{1 to} P ₆ of the zoom encoder 32, respectively, the contact pieces T _{1 to} T ₆ are moved to the zoom ring 40 by the shape of the patterns P _{1 to} P _6. 64 combinations of code signals from the start point 0 to the end point 63 of the zoom encoder position are detected in accordance with the rotational position of. In addition, the fourth
In FIG. 3A, the dot-formed portions on the electrode patterns P _G and P _V are auxiliary patterns for preventing malfunctions, so basically the electrode patterns in these portions may be removed to form electrodeless portions. .

The patterns P ₁ ~ read by the contacts T ₁ ~ T ₆
64 types of code signals of P ₆ are shown in FIG. 4 (B). In this code signal table, the contacts T _{1 to} T ₆ are the reference voltage Vref.
It is "1" when it is given, and it is "0" when it is given the ground potential GND.

Here, focusing on only the patterns P ₁ and P ₂ , the contact pieces T ₁ and T ₂ read these two patterns, and thereby four states (0,0), (0,1), (1,1) , (1,0) can be determined, so that the A / D conversion terminal AD _ZMA of the CPU 11 can determine four levels by the resistors R ₁ and R ₂ as shown in the following table.

That is, the input to the A / D conversion terminal AD _ZMA by the combined resistance of the resistors R ₁ and R ₂ is R ₁ : R ₂ = 1.67 when the reference voltage Vref is 1, so that the above table 0 as shown in
It is divided into four levels: ~ 0.22,0.27 ~ 0.47,0.52 ~ 0.72,0.77 ~ 1. Since the A / D conversion terminal AD _ZMA of the CPU 11 has a high impedance, when _{one of} the patterns P ₁ and P ₂ is off, the level becomes the level of the other pattern.

The other two A / D conversion terminals AD _ZMB and AD _ZMC of the CPU 11 have the same configuration.

Since the zoom encoder 32 has six patterns, it is possible to detect 64 (0 to 63) encoder positions in total. Encoder position 1 is a wide (wide-angle) end position, encoder position 60 is a tele (telephoto) end position, and encoder position 63 is a macro position. Encoder position 61,62
Is an intermediate area where a picture cannot be taken, and encoder position 0 is a wide-angle position.

If the inputs to the A / D conversion terminals AD _ZMA , AD _ZMB , and AD _ZMC are divided into four levels as described above, post-processing becomes very simple. That is, the result of A / D conversion becomes a 6-bit signal in total, but the upper 2 bits of these are “00”, “01”, “1”.
Corresponding to 0 "and" 11 "(binary), it is already divided into 4 levels, so there is no need to divide the new A / D conversion input into levels. Also, because the variation range is very large,
Even if there are variations in resistance and variations in the reference voltage Vref, stable results can always be obtained.

Further, as shown in FIG. 3, the other ends of the resistors R ₁ and R ₂ which are connected to each other and connected to the A / D conversion terminal AD _ZMA of the CPU 11 are connected via a resistor R ₈ having a high resistance value. Therefore, even if both of the contact pieces T ₁ and T ₂ are in contact with the electrodeless portion (OFF), it can be determined to be “11” (binary number) by hanging the reference voltage Vref. Such a configuration helps prevent malfunction in the case where the distance between the _two patterns P ₁ and P ₂ is narrow, and
The configuration of the electrode pattern will be simplified.

Next, the calculation of the lens extension amount for autofocus will be described. The distance data L corresponding to the subject distance 1 is given from the AFIC 22 to the CPU 11 as adjusted 6-bit and decimal 6-bit data. Since this camera is of the inner focus type, as shown in FIG. 5, the lens extension amount (lens extension pulse) S varies depending on the zoom position (focal length) even at the same distance. That is, in FIG. 5, the curves in the tele end, standard (standard) and wide end positions are shown as representatives, but the curves from the wide end position 1 to the tele end position 60 are different.
The lens feeding is performed according to the lens feeding curve of the book. However, since the CPU 11 does not have enough capacity to store all the curves, the lens extension amount S of 20 points from 0 to 20 at which the distance data L is an integer is stored in the ROM only for the telephoto end curve 45. ing. The lens extension amount S data at the telephoto end is set to ST
_j (j = 0 to 20). The curve of each focal length other than the tele end is the distance data L for the curve 45 at the tele end.
Also in (1), since it is on a line that is internally divided by a certain ratio, the curve of each focal length other than tele can be approximately obtained by multiplying the zoom coefficient on the curve 45 at the tele end. Therefore, the zoom factor for each focal length is stored in the ROM in CPU11.
Cf _i is the zoom factor Cf corresponding to the 60 curves
_i (i = 1 to 60) is stored. That is, the zoom coefficient Cf _i corresponding to the encoder value i of the zoom encoder 32
Is stored in the ROM in the CPU 11.

Therefore, when the zoom encoder value i is set by operating the zoom ring 40, the zoom coefficient Cfi corresponding to the set encoder value _i is read from the ROM. On the other hand, the lens extension amount at the telephoto end position is read from the ROM corresponding to the object distance measured by the AFIC 16. Then, based on the lens extension amount at the tele end position, the CPU 11 performs an operation using the zoom coefficient Cf _i to obtain the lens extension amount at the set zoom encoder value i.

Here, when the integer part of the data of the AFIC 22 is a and the decimal part is b, the feed amount (feed pulse) S at the zoom encoder value i can be obtained by the following simple formula.

_{S = {b (ST a +} 1 -ST a) + ST a} · Cf i ...... (1) can also be fully calculated in such a formula if the operation instruction fewer 4-bit microcomputers. Incidentally, since the curve is completely different from that shown in FIG. 5 in the macro mode, the macro curve is specially stored in the CPU 11. The calculation formula is the same except that the zoom coefficient Cf _i is removed from the above formula (1).

The above-mentioned matter is the case where the zoom lens is as designed, but in reality, since there is variation in each lens, the curve shown in FIG. 5 may be translated upward or downward by this variation. Will result. Of course, the amount of this parallel movement differs depending on the lens, but the tele end position,
Even if the deviation amount is adjusted to 0 at the wide end position, the deviation amount does not become 0 at the zoom position between them, and for example, the sixth
As shown in the figure. As can be seen from FIG. 6, since it is adjusted at the wide end position 1 and the tele end position 60,
The amount of deviation is 0.

Therefore, in this camera, the above deviation data is converted into five data.
It is stored in the E ² -PROM 14 as D _k (k = 0 to 4). As the stored data, at least the lower 4 bits of the A / D converted value are all "0000". Zoom encoder value 0 (hexadecimal OH, the same applies below), 16 (10H), 32 (20H), 4
5 data of 8 (30H) and 64 (40H), which are D ₀ , D ₁ and
It is stored as D ₂ , D ₃ and D ₄ . However, it is not possible to measure the points where the zoom encoder position is 0 and 64, so when measuring, 1 (1H), 16 (10H), 32 (20H), 48 (30H), 60 (3
The number of shift pulses at each point (CH) is calculated. Among them, the zoom encoder position is measured from the measurement data D ₀ ′ at the wide end position 1 and the measurement data D ₄ ′ at the tele end position 60, and the zoom encoder positions 0 and 64 The data D ₀ , D _{4 at} is obtained. That is, D ₀ and D ₄ are given by the following equation (2),
It is obtained by the equation (3).

D ₀ = D ₀ ′ − (D ₁ −D ₀ ′) / 15 (2) D ₄ = D ₃ + (D ₄ ′ −D ₃ ) / 12 (3) And the zoom encoder position i The number of shift pulses at other unstored zoom encoder positions i is obtained by interpolation calculation based on the shift data stored at the five points. Here, the feed pulse movement amount Zs in the case of the zoom encoder value i is obtained as follows.

Zs = _Dia + D _{(ia + 1) −Dia} ) · ib (4) In this equation (4), ia is the zoom encoder value i of 2
It is the integer value of the upper 2 bits when expressed in a decimal number, ib
Is a decimal value of the lower 4 bits. The feed pulse movement amount Zs of the above formula (4) can also be sufficiently calculated by a 4-bit microcomputer.

From the above calculation results, the actual feed amount is S + Zs. As is clear from the above equations (2) and (3), even if the adjustment at the tele end position and the wide end position is deviated (even if it is not 0), this is stored in the E ² -PROM 14. It is possible to make a correction by setting in advance.

As described above, in this embodiment, first, the distance information is obtained from the AFIC 16, the data of the lens extension amount at the time of telephoto stored in the CPU 11 is searched from the data, and then the zoom coefficient Cf _i is calculated from the zoom encoder value _i. Then, calculation is performed in the CPU 11 to obtain the lens extension amount at the currently set focal length. Then, here, the zoom encoder value i
The variation data D _k for each camera is read from the E ² -PROM 14, and the above-mentioned amount of extension is corrected to obtain the actual amount of extension of the lens.

[Effects of the Invention] As described above, according to the present invention, it is possible to correct the lens variation for each camera, and further, it is possible to correct even if the optical adjustment is deviated.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the outline of a focus correction apparatus for a camera with a zoom lens according to the present invention, and FIG. 2 is a block diagram showing a basic system of a zoom lens camera to which the present invention is applied. 2 is an electric circuit diagram showing the configuration of the zoom encoder in FIG. 2, and FIGS. 4 (A) and 4 (B) are developed views of encoder patterns on the zoom ring in FIG. 3 and encoder positions thereof. FIG. 5 is a diagram showing a code for the above, FIG. 5 is a diagram for explaining the lens extension amount with respect to the AF sensor output, and FIG. 6 is a line for explaining the correction movement of the lens extension amount with respect to the zoom encoder position. It is a figure. 1 …… Non-TTL distance measuring means 2 …… Storage means 3 …… Calculation means 4 …… Lens driving means 11 …… CPU (calculation means) 14 …… E ² -PROM (storage means) 16 …… AFIC (non-TTL) Distance measuring means)

Claims (2)

[Claims] 1. A camera with a zoom lens that calculates the amount of movement of a focusing lens from a reference position based on subject distance information obtained from a non-TTL distance measuring unit and set focal length information. Storage means for storing a difference between the calculated movement amount caused by variations in component dimensions corresponding to each focal length; calculation means for interpolating a value between the plurality of stored values; A focus correction apparatus for a camera with a zoom lens, comprising: a lens driving unit that drives the focusing lens based on a final movement amount obtained by adding the interpolated calculation value to the calculated movement amount. 2. The focus correction apparatus for a camera with a zoom lens according to claim 1, wherein the storage means is an electrically writable non-volatile memory that is written after the camera is assembled.