JPH07111499B2 - Interchangeable lens for autofocus camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention corresponds to the amount of deviation of the image formation position of a focusing object from an expected focus position by receiving light from the focusing object that has passed through an interchangeable lens. The amount of defocus is detected, the driving means on the camera body side is driven based on this defocus amount, and the driving force is transmitted to the focus adjusting member of the interchangeable lens to move the image forming position for automatic focus adjustment. The present invention relates to an automatic focus adjustment method and device.

(Prior Art) Since the detected defocus amount and the drive amount of the driving unit are in a substantially proportional relationship, the drive amount is calculated by multiplying the defocus amount by an appropriate conversion coefficient. The conversion coefficient data changes depending on the focal length of the interchangeable lens, optical characteristics such as the lens configuration, and the focus adjustment mechanism. That is, the conversion coefficient data differs for each interchangeable lens. Therefore, this conversion coefficient data can be set in the interchangeable lens, the conversion coefficient data can be read from the interchangeable lens by the camera body, and the drive amount can be calculated from this data and the defocus amount. However, some interchangeable lenses, such as a front-lens extension type variable power lens, have conversion coefficient data that changes as the focal length changes due to a variable power operation. In the case of such a variable power lens, a storage element such as a ROM is provided on the variable power lens side, and conversion coefficient data is fixedly stored in this ROM according to the focal length, and the focus set by the variable power operation is set. A device is already known in which conversion coefficient data of an address corresponding to a distance is read by a camera body and a drive amount is calculated from this data and a defocus amount. Conventionally, in this type of device, only the conversion coefficient data for the lens is stored in the ROM, and it is necessary to produce a dedicated ROM for each lens, which raises the problem of increasing the price of lenses manufactured in small quantities. It was

As a device for solving this problem, ROM is provided with a type code generating means for fixedly storing a plurality of types of conversion coefficient data and generating a lens type code.
The conversion coefficient data of the lens is read from the ROM by the camera body, and the drive amount is calculated from this data and the defocus amount. However, even in this device, there is a limit to the capacity that can be stored in ROM, and a large capacity R
On the contrary, the problem that the cost becomes high if the OM is provided remains. In addition, conversion coefficient data that is fixedly stored in the ROM is required to develop the ROM. Therefore, the optical design and lens barrel design of the lens corresponding to the common ROM must be completed. There was a problem that design and ROM development could not proceed at the same time, and the lead time until mass production was prolonged only during the ROM development period.

Further, since the conversion coefficient data is fixedly stored in the ROM, it is impossible to change the conversion coefficient data by partially changing the lens specifications, and there is a problem that the improvement of the product is greatly limited.

ROM of conversion coefficient data as a solution to the problem described above
It is conceivable to use a calculation method according to the set focal length by a variable magnification operation, instead of fixedly storing it in a storage element such as. However, there are the following problems.

If the conversion coefficient data is made to be compatible with a very variable lens such as a front-lens variable power lens, the number of bits will increase. Therefore, such conversion coefficient data is composed of an exponent part and a significant figure part, and the camera body calculates the driving amount of the driving means from the conversion coefficient data consisting of the exponent part and the significant figure part and the defocus amount. . However, although it is easy to store fixedly the conversion coefficient composed of the exponent part and the significant figure part in the ROM, it is very difficult to calculate it according to the set focal length by the zooming operation. It was

(Object) The present invention provides a conversion coefficient for converting the defocus amount detected by the camera body into the transmission drive amount from the camera body to the interchangeable lens, which is always appropriate data with respect to the set focal length by the zooming operation. An object of the present invention is to provide an automatic focus adjustment method and device which can be transmitted to the main body, enable accurate automatic focus adjustment, and can respond to a reduction in lead time until mass production and a change in specifications.

(Means for Solving the Problem) According to the present invention, the conversion coefficient for converting the defocus amount into the transmission drive amount from the camera body to the interchangeable lens is logarithmically compressed in correspondence with the set focal length by the zooming operation. Data is calculated on the interchangeable lens side and output serially to the camera body, and the conversion coefficient data read from the interchangeable lens on the camera body side is logarithmically expanded (indexed), and from this data and the defocus amount, the focus adjustment member It is configured to calculate the drive amount.

(Examples) Hereinafter, the present invention will be described with reference to Examples.

FIG. 1 is a block diagram showing a camera system for automatic focus adjustment to which the present invention is applied, where the left side of a constant chain line is an interchangeable lens (X) and the right side is a camera body (Y) side. The clutch (1), Mechanically through (2), the terminal (P ₀ )
~ (P ₄ ) and (B ₀ ) to (B ₄ ) are electrically connected.

The light from the focusing object that has passed through the focus adjustment lens (FL) of the interchangeable lens (X), the variable magnification lens (ZL), and the master lens (ML) is reflected by the reflection mirror (3) of the camera body (Y). It is configured so that it passes through a semi-transparent mirror portion provided in the center, is reflected by the sub mirror (4), and is received by the focus position detection element (5).

The distance measurement processing circuit (6) calculates the defocus amount ΔL and the defocus direction corresponding to the shift amount with respect to the planned focus position based on the signal from the focus position detection element (5). The drive mechanism (8) selectively rotates the motor clockwise and counterclockwise based on the defocus direction data, and after decelerating the rotation, the transmission mechanism of the interchangeable lens via the clutches (1) and (2). (DR) and focus adjustment lens (F
L) is moved to adjust the focus.

The lens information output circuit (LD) on the side of the interchangeable lens is provided with an encoder (ENC) that works in conjunction with the zooming operation member (ZR), and data corresponding to the set focal length is input.
Based on this data, the conversion coefficient data for converting the defocus amount to the movement amount of the focus adjustment lens is logarithmically compressed data and the terminals (P ₀ ) to (P ₄ ) and (B ₀ ) to (B ₄ ) are It is read by the lens information reading circuit (LR) on the main body side. The logarithmic expansion circuit (LL) expands the logarithmically compressed conversion coefficient data read by the lens information reading circuit (LR) logarithmically (exponentially) and converts it into data that can be easily handled by the next multiplication circuit (7). There is. The multiplication circuit (7) multiplies the conversion coefficient K from the logarithmic expansion circuit (LL) by the defocus amount ΔL from the distance measurement processing circuit (6) to move the focus adjustment lens (FL) to the in-focus position. The amount of drive to move is calculated. The drive mechanism (8) is provided with an encoder (10), and outputs a pulse signal each time the drive mechanism (8) moves the focus adjustment lens (FL) by a predetermined amount, and the counter (11) counts this pulse. To do. The comparison circuit (9) compares the data from the multiplication circuit (7) with the data from the counter (11), and if both data match, it is determined that the focus adjustment lens (FL) has moved to the in-focus position, and drive A motor stop signal is output to the mechanism (8).

In the above description, the overall function of the present invention has been shown by a block diagram. Next, the lens information output circuit (LD) on the interchangeable lens side will be described in detail.

FIG. 2 is a block diagram showing the transmission of lens information. The left side of the alternate long and short dash line is the camera body (X) and the right side is the interchangeable lens (Y) side lens information output circuit.

The terminal (B ₀ ) on the camera body side is the power output terminal and is connected to the power input terminal (P ₀ ) on the interchangeable lens side. (B ₁ ) on the camera body side is connected to the reset terminal (RE) of the counters (CO ₁ ) and (CO ₂ ) via the input terminal (P ₁ ) on the interchangeable lens side and the inverter (IN).

This input terminal (P ₁ ) is "High" while receiving information from the interchangeable lens, and the counters (CO ₁ ) and (CO ₂ ) are in the reset release state.

The output terminal (B ₂ ) on the camera body sends a clock pulse from the camera body to the interchangeable lens side via the input terminal (P ₂ ) of the interchangeable lens in order to synchronize the electrical operation between the interchangeable lens and the camera body. Connected to the terminal (CL) of the counter (CO ₁ ).

The counters (CO ₁ ) and (CO ₂ ) are 3-bit binary counters, and the counter (CO ₁ ) counts the rising edge of the clock pulse from the input terminal (P ₂ ) and from the rising edge of the 8th clock pulse. The carry pin (CY) is set to "High" until the next clock pulse rises. The counter (CO ₂ ) counts the falling edge of the carry terminal (CY), and the count value of the counter (CO ₂ ) is incremented by 1 at every rising edge of the first pulse of the eighth clock pulse.

Counter 3-bit output of the _{(CO 2) (E 2 ~E} 0) is input to the decoder (DE _2), from the decoder (DE _2),
Output terminal (S ₀ ), depending on the content of the counter (CO ₂ ),
(S ₁ ), (S ₂ ), (S ₃ ), and (S ₄ ) are sequentially set to “High”,
Output a select signal to the data selector (DS ₁ ). The data selector (DS ₁ ) is the lens specific information (AI) set in the input terminals (AI _{5 to} AI ₀ ) when the data select signal (S ₀ ) from the decoder (DE ₂ ) is "High".
To the output terminals (I _{5 to} I ₀ ), and when the data select signal (S ₁ ) becomes “High”, the lens specific information (BI) set to the input terminals (BI _{5 to} BI ₀ ) is output. Terminals (I _{5 to} I ₀ )
Output to. Similarly, the data select signal is (S ₂ ),
At the same timing as proceeding to (S ₃ ) and (S ₄ ), input terminal (CI
_{5 to} CI ₀ ), (DI _{5 to} DI ₀ ), and (EI _{5 to} EI ₀ ), set the lens specific information (CI), (DI), and (EI) to the output terminals (I ₅ to
It is sequentially output to I ₀ ). Table 1 shows the relationship between the counter (CO ₂ ), the decoder (DE ₂ ) and the data selector (DS ₁ ).

The lens specific information (AI) set in the input terminal of the data selector (DS ₁ ) is the information identification code "00" that identifies the quantity and content of the lens specific information set and output by the lens.
0001 "is set, and if the lens has a large amount of information, the information identification code" 000010 "is set. The camera body reads this identification code and selects the subsequent information reading method. Set to (BI). If the built-in automatic diaphragm mechanism (BI ₀ ) is set to "High", the function code is set to "High" if the coupling mechanism for driving the focusing lens from the camera body side is built in (BI ₁ ). If the focus adjustment lens is rotated counterclockwise, (BI ₂ ) is set to “High.” (CI) is the AV value (AV = log ₂ F ² ) is set in units of 1/8 EV. For example, when the aperture value is F: 2.5, the AV value is 2 + 5/8, so it is set to “010101”. In the case of a lens whose open aperture changes with, the maximum aperture value is set For (DI), if the lens has a fixed focal length, the focal length of the lens is set, and if the lens has a variable focal length, the logarithmic value 8log ₂ f with the base 2 of the focal length f on the shortest focal side as the base is set. ing.
For example, when the focal length is f = 35 mm, it is “101001”. Then, (EI) is the amount by which the focus adjustment lens is moved toward the planned focus position from the defocus amount Δd corresponding to the amount of deviation of the imaging position of the subject to be focused detected from the camera body with respect to the planned focus position. A conversion coefficient K for setting ΔL is set. Let Kd = ΔL / Δd be the ratio of the amount of movement Δd and ΔL of the image plane when the lens is moved by ΔL, and let the helicoid lead of the focus adjustment member be HL and the reduction ratio of the transmission mechanism be GL. , K = Kd / (GL × HL) is obtained. Further, it is known that the above Kd generally has a relationship of Kd = ff ² / f ² approximately when the focal length of the entire optical system is f and the focal length of the optical system for focus adjustment is ff. There is. Therefore, like a variable power lens of the front lens extension type, the focal length f
Is doubled, the Kd value and the change conversion coefficient K change 1/4 times in a very wide range, so that the number of input terminals (EI) cannot be compared. Therefore, the coefficient KL that makes the conversion coefficient K a logarithmically compressed value is expressed by KL = 16log ₂ K + 64, and this KL value is set to the input terminal (EI).
For example, when the conversion coefficient K is 0.1, it is “001011”. In the case of a variable power lens, the conversion coefficient on the long focus side, which has the smallest conversion coefficient, is set.

The decoder (DE ₂ ) outputs the data select signal (S _{0 to} S ₄ ) to the data selector (DS ₁ ), and at the same time, outputs a part (S _{2 to} S ₄ ) of the output signal to the data selector (DS ₂ ).
Also output to. Data selector (DS ₂₎ when the data select signal from the decoder (DE ₂₎ (S ₂₎ is "High", the unit movement corresponding to the focal length is set to the input terminal (CJ ₂ ~CJ ₀₎ The information change amount (CJ) is output to the output terminals (J _{5 to} J ₀ ), and similarly when the data select signal advances to (S ₃ ), (S ₄ ), the input terminals (DJ
₄ ~ DJ ₁ ), (EJ ₅ ~ EJ ₃ ) set information change amount (D
J), are sequentially output to the (EJ) an output terminal (J ₅ ~J _0). Table 2 shows the relationship between the counter (CO ₂ ), decoder (DE ₂ ) and data selector (DS ₂ ).

The information change amount (CJ) set at the input terminal of the data selector (DS ₂ ) is set as the open aperture change amount ΔAV per unit movement amount that corresponds to the focal length of the lens whose open aperture value changes due to the zoom operation. Has been done.

For example, when the open aperture value F1 = 2.5 on the short focus side and the open aperture value F2 = 3.5 on the long focus side, the total variation AVO is AVO = log ₂ F2 _2- log ₂ F1 ² = log ₂ (3.5) ^2- log ₂ (2.5) ² = 1 (EV) Since the resolution of the encoder (ENC) is 15 steps, the change amount of the open aperture per unit movement amount ΔF = 1/15 (EV),
"101" is set with this as 1/64 EV unit. (D
In J), the focal length change amount Δf per unit movement amount is set. For example, f1 = 35mm on the short focus side, f2 = 13 on the long focus side
The total change fO at 0 mm is fO = 8log ₂ f2-8log ₂ f1 = 8log ₂ 130-8log ₂ 35 = 15.15 The focal length change per unit movement amount Δf = 15.15 / 15, which is 1/4 unit It is set as "0100" in binary expression. The change coefficient change amount per unit movement amount is selected for (EJ). For example, if the conversion factor K1 = 1.37 for the short focal length side 35 mm, and the focal length changes 3.7 times to the long focal length side 135 mm, then the conversion factor is 1 / K2 from the relation if Kd = ff ² / f ^2.
13.7 times, that is, the conversion coefficient K2 on the long focal length side of 135 mm becomes K = 0.1, and the total variation KLO of the coefficient KL, which is the logarithmically compressed value of K1 and K2, is KLO = 16log ₂ K1−16log ₂ K2 = 16log ₂ 1.37−16log ₂ 0.1 = 60.4 Conversion coefficient change amount per unit movement amount ΔK = 60.4 / 15 and "100" is set. In addition, in the case of a fixed focus lens or a lens that does not change each information due to zooming operation,
Input terminals (CJ _{2 to} CJ ₀ ), (DJ _{4 to} DJ ₁ ), (EJ _{5 to} EJ ₃ ).
Is set to "0". Also, due to the difference in accuracy required to set each information change amount and the possible value of the change amount,
The number of input terminals of the data selector (DS ₂ ) and the signal output position when the input information is output to the output terminals (J _{5 to} J ₀ ) are determined corresponding to each information change amount.

Lens specific information (AI), (BI), (CI), (D) input to the input terminal of the data selector (DS ₁ ) described above
The information change amounts (CJ), (DJ), and (EJ) to be input to the input terminals of I), (EI), and the data selector (DS ₂ ) are set at the time of incorporating this circuit in the lens barrel or at the preparation stage. Can be set. To set each bit of information to "0", connect the corresponding input terminal to ground, and to set it to "1", connect the corresponding input terminal to the power supply line (+ VF).

In the case of a variable power lens, an encoder (ENC) that outputs a 4-bit signal corresponding to the relative movement amount from the reference position to the set position by operating a focal length variable power operation member (not shown) is provided. Has been. The conduction pattern of the encoder (ENC) is set so that the information change amount per unit movement amount (1 step of the encoder) set in the input terminal of the data selector (DS ₂ ) and the change amount indicated by the actual lens are synchronized. Has become.

The sliding member (VC) is interlocked with the focal length varying operation member, and is set at any one of the focal length setting positions (1) to (3). Conductive pattern (COM) is grounded, the other conductive pattern (EC ₃ ~EC ₀₎ is connected to a power supply line (+ VF) through respective resistors. Therefore, when the contact piece of the sliding member (VC) comes into contact with any of the conduction patterns (EC _{3 to} EC ₀ ), the conduction pattern (COM) and the conduction pattern (EC _{3 to} EC 0
The sliding member (VC) in ( ₀ ) that is in contact with the sliding member (VC) is short-circuited by the sliding member (VC), and the signal output becomes "Low". In addition, the signal output of the non-contact type becomes "High".

The output of the conduction pattern (EC ₃ ) of the encoder (ENC) is connected to one of the input terminals of AND gates (AN A) and (AN B), and the other input terminal is the output terminal (S ₄ ) of the decoder (DE ₂ ). The outputs of the AND gates (AN A) and (AN B) are connected to the exclusive OR gate (E) via the OR gate (OR ₃ ).
It is connected to one input terminal of R ₂ ) and the input terminal (K ₃ ) of the multiplication circuit (MLT). The output of the conductive pattern (EC ₂₎ is connected to the other input terminal of the inverter exclusive OR gate through the _{(IN 2) (ER 2)} , the output of the exclusive OR gate (ER ₂₎ is one of an exclusive OR gate (ER ₁₎ It is connected to the input terminal and the input terminal (K ₂ ) of the multiplication circuit (MLT). The output of the conduction pattern (EC ₁ ) is connected to the other input terminal of the exclusive OR gate (ER ₁ ) via the inverter (IN ₁ ), and the output of the exclusive OR gate (ER ₁ ) is connected to _one of the exclusive OR gate (ER ₀ ). It is connected to the input terminal and the input terminal (K ₁ ) of the multiplication circuit (MLT). Further, the output of the conduction pattern (EC ₀ ) is connected to the other input terminal of the exclusive OR gate (ER ₀ ) via the inverter (IN ₀ ), and the output of the exclusive OR gate (ER ₀ ) is the input of the multiplication circuit (MLT). Connected to terminal (K ₀ ). At this position, set the focal length to the encoder (EN
C) output (EC _{3 to} EC ₀ ) and decoder (DE ₂ ) output (S ₄ )
Table 3 shows the relationship between the output signals to the input terminals (K _{3 to} K ₀ ) of the multiplication circuit (MLT).

Encoder (ENC) conduction pattern is output (EC _{3 to} EC ₀ )
Is provided so that it becomes a gray code. When the output terminal (S ₄ ) of the decoder (DE ₂ ) is "Low", the relative movement amount to the set position of the focal length setting position is the input terminal of the multiplication circuit (MLT). (K ₃ ~ K ₀ )
Is output to. When the output terminal (S ₄ ) of the decoder (DE ₂ ) is “High”, the relative movement amount to the set position when the set position of the focal length is the reference position is the input of the multiplication circuit (MLT). It is output to the terminals (K _{3 to} K ₀ ). In this way, the output terminal (S ₄ ) signal of the decoder (DE ₂ ) is "High".
The reason why the reference position of the focal length is switched to in the case of will be described with reference to FIG.

In FIG. 3, the horizontal axis shows from the setting position of the encoder (ENC), and the vertical axis corresponds to the lens unique information value. In this lens, the lens-specific information that changes due to the focal length varying operation is the three types of open aperture value, focal length, and conversion coefficient shown in FIG. Among them, the open aperture value and the focal length change in the direction in which the lens specific information increases as the encoder (ENC) setting position advances to.
However, the conversion coefficient changes in the opposite direction. Therefore, for the maximum aperture value and focal length, the encoder (ENC) setting position where the information value is the minimum is specified as the reference position, and the maximum aperture value at this reference position is input to the data selector (DS ₁ ) input terminal (CI ₅ ~ Input the focal length to CI ₀ ) (DI _{5 to} DI ₀ )
Are set respectively. In addition, the encoder (ENC) setting position where the conversion coefficient is the minimum is set to the reference position, and the conversion coefficient at this reference position is selected by the data selector (DS ₁ ).
Are set to the input terminals (EI _{5 to} EI ₀ ) of. Then, it is switched as shown in Table 3 relative movement amount to the set position from the reference position to the input terminal (K ₃ ~K ₀₎ of the multiplier circuit (MLT) by the reference position or differences.

The multiplier circuit (MLT) uses the 6-bit unit information change amount from the output terminals (J _{5 to} J ₀ ) of the data selector (DS ₂ ) as the multiplicand, and the relative movement amount from the reference position at the encoder (ENC) setting position. 4 bits of input terminals (K _{3 to} K ₀ ) for inputting are used as multipliers and multiplied to obtain the amount of change.

The right side of the left chain in FIG. 4 is the circuit configuration of the multiplication circuit (MTL). The multiplication here uses the method of bit shift addition, and the principle will be described by the following equation.

The multiplicand (6 bits) is shifted one bit to the left and arranged by the number of digits of the multiplier (4 bits) and added.

At this time, the multiplication bits (K ₀ ), (K ₁ ), (K ₂ ),
(K ₃₎ is what going on, "1" if the sum, "0", the multiplication value by not adding is being asked. Next, a multiplication circuit (MLT) on the right side of the one-point left chain in FIG. 4 configured according to this principle will be described. The multiplication circuit (MLT) is composed of the following four circuits.

First, the 6-bit input terminal (J ₅
To J ₀ ) the unit information change amount is input as a multiplicand, and the 4-bit input terminals (K _{3 to} K ₀ ) are input the relative movement amount as a multiplier. If the input signal of the input terminal (K ₀ ) is "1", AND gate (AN 05), (AN 04), (AN 03), (AN 0
2), the gates of (AN 01) are opened, and the unit information change amount of the 6-bit input terminals (J _{5 to} J ₀ ) is output to B (multiplier K ₁ , K ₀ digit adder circuit). If the input signal of the input terminal (K ₀ ) is "0", AND gate (AN 05), (AN 04), (AN 0
3), (AN 02), (AN 01) gates closed, B (multiplier K
All "0" s are output to the ₁ and K ₀ digit adder circuits, so that the multiplier (K ₀ ) digit is not added. Similarly, if the input signal of the input terminal (K ₁ ) is “1”, AND gate (AN 1
5), (AN 14), (AN 13), (AN 12), (AN 11),
Gate open (AN 10), the unit information amount of change of the input terminal (J ₅ through J ₀₎ is outputted to the B (multiplier K _1, K ₀ digit adder circuit). If the input signal of the input terminal (K ₂ ) is "1", AND gate (AN 25), (AN 24), (AN 23), (AN 22), (AN
The gates of 21) and (AN 20) open, and the unit information change amount of the input terminals (J _{5 to} J ₀ ) is output to C (multiplier K _2- digit addition circuit). If the input signal of the input terminal (K ₃ ) is "1", AND gates (AN 35), (AN 34), (AN 33), (AN 3
2), (AN 31), (AN 30) gates open and input terminal (J
The unit information change amount of _{5 to} J ₀ ) is input to D (multiplier K _3- digit addition circuit).

The unit information change amount output from A (addition digit determination circuit) is B (multiplier K ₁ , K ₀ digit addition circuit), C (multiplier K ₂ ) for each digit of the multiplier.
Digit adder circuit), D (multiplier K ₃ digit adder circuit), and the unit information conversion amount (6 bits), which is the multiplicand, is added by shifting it to the left by 1 bit as shown in the previous expression. The gate of the D (multiply K ₃ digit adder circuit) (OR 2
3), Exclusive OR gate (ER 39), (ER 37), (ER 3
5), (ER 33), (ER 31), (ER 29) outputs a 7-bit change amount as a multiplication result.

The adder circuit (ADD) on the left side of the one-point left chain in FIG. 4 has the circuit configuration of the adder circuit (ADD) in FIG. The change amount output from the multiplication circuit (MLT) on the right side of the left chain in FIG. 4 when the lens-specific information at the reference position is input from the data selector (DS ₁ ) to the 6-bit input terminals (I _{5 to} I ₀ ). Input the multiplication result of, the change amount is added to the lens unique information at the reference position,
The addition result is output to the output terminals (O _{7 to} O ₀ ). By this addition, the open aperture value at the focal length setting position, the focal length, and the conversion coefficient are obtained. Since the information identification code and the function code are information that does not change due to the focal length scaling operation, the amount of change output from the multiplication circuit (MLT) is all "0", and therefore the information content by the addition circuit (ADD) There is no change.

Returning to FIG. 2 again, description will be made.

Counter (CO ₁₎ 3-bit output of the (C ₂ ~C ₀₎ is input to the decoder (DE _1), from the decoder (DE _1),
The signals shown in Table 4 are output according to the contents of the counter (CO ₁ ).

The output terminals (D _{0 to} D ₇ ) of the decoder (DE ₁ ) are connected to one input terminals of the AND gates (AN _{0 to} AN ₇ ), and the other are output terminals (O _{0 to} O ₇ ) of the adder circuit (ADD). ), And outputs of the AND gates (AN _{0 to} AN ₇ ) are output to the camera body side (X) via the OR gate (OR), terminals (P ₃ ) and (B ₃ ).

When the counter advances by 1 at the rising edge of the clock pulse, the output terminal (D ₀ ) of the decoder (DE ₁ ) becomes “High”, the gate of the AND gate (AN ₀ ) is opened, and the output terminal (O _{0 of the} adder circuit Signal is output via the OR gate (OR). In this way, every time the clock pulse rises, the signals of the output terminals (O _{0 to} O ₇ ) of the adder circuit are sequentially bit by bit from the least significant bit AND gate (AN _{0 to} AN ₇ ), OR gate (OR), terminal (P3 ), (B3), and a signal is output to the camera body side (X).

Here, returning to FIG. 1 again, description will be made.

The conversion coefficient data KL output from the lens information output circuit (LD) is logarithmically compressed data as terminals (P ₀ ) to (P ₄ ),
It is read by the lens information reading circuit (LR) on the main body side through (B ₀ ) to (B ₄ ). The conversion coefficient KL is a value for multiplying the defocus amount by the multiplication circuit (7) to calculate the drive amount for moving the lens for focus adjustment lens (FL) to the in-focus position. However, the value KL read from the interchangeable lens side is logarithmically compressed by the formula shown by KL = 16log ₂ K + 64, so it is difficult to multiply as it is. Therefore, the logarithmic expansion circuit (LL) for logarithmically expanding (exponentializing) this KL value to the conversion coefficient K before logarithmic compression calculates data that is easy to handle in the multiplication circuit (7).

For logarithmic expansion (exponentiation), the conversion coefficient K can be calculated by the formula K2 = 2 ^{(KL−64) / 16,} but the calculation becomes complicated. Therefore, logarithmic expansion (exponentiation) is performed by the following approximation method. . Transform coefficient data KL as logarithmically compressed data from the interchangeable lens
Are divided into upper 4 bits as shown below.

The lower 4 bits are set as a decimal part, and 1 is added as an integer part to obtain (1).

1.K ₃ K ₂ K ₁ K ₀ (1) Then, subtract 4 from the binary value consisting of E ₃ E ₂ E ₁ E ₀ , and calculate the value of (1) above by the value calculated by this By shifting, the approximate value of the conversion coefficient K is easily calculated. Table 5 shows the conversion coefficient KL as logarithmically compressed data output from the interchangeable lens, the conversion coefficient KA calculated by numerical calculation, and the conversion coefficient KB calculated by the above approximation method to examine the accuracy of the approximation value.

The KB value calculated by the approximation method is slightly larger than the KA value calculated by the numerical calculation. If the K value is larger than the actual data in this way, the drive amount for moving the focus adjustment member becomes large, and the target focus position may pass and hunting may occur before and after the planned focus position. . Therefore, as a measure to bring the KB value calculated by the approximation method as close as possible to the KA value, the conversion factor on the long focus side set in the input terminal (EI) of the data selector (DS ₁ ) in Fig. 2 is set to a slightly smaller value. It may be set to.

Transform coefficient K logarithmically expanded by the logarithmic expansion circuit (LL)
And the defocus amount ΔL from the distance measurement processing circuit (6) are multiplied by the multiplication circuit (7) to calculate the drive amount for moving the focus adjustment lens (FL) to the in-focus position. Drive mechanism (8)
Selectively rotates the motor clockwise or counterclockwise based on the defocus direction data from the distance measurement processing circuit (6), and exchanges the rotation through the clutches (1) and (2) after deceleration. Move the lens (FL). Then, the encoder (10) interlocking with the drive mechanism (8) outputs a pulse signal each time the focus adjustment lens (FL) is moved by a predetermined amount, and the counter (11) counts this pulse. The comparison circuit (9) compares the data from the multiplication circuit (7) with the data from the count (11), and when both data match, it is determined that the focus adjustment (FL) has moved to the in-focus position, and the drive mechanism The motor stop signal is output to (8).

In the above-described embodiment, the circuit portion of the present invention is composed of individual circuit elements, but the circuit portion on the camera body side of FIG. 1 and the entire lens information output circuit portion of FIG. 2 are each formed by a microprocessor such as a one-chip microcomputer. It may be configured to control the automatic focus adjustment device of the present invention in sequence.

(Effect of the invention) The present invention sets the conversion coefficient at the reference focus position (long focus side) as logarithmic compression data, and outputs the relative movement amount from the reference focus position to the set focus position by the scaling operation, in units of It is configured so that the conversion coefficient change amount per movement amount can be set, the relative movement amount and the conversion coefficient change amount are multiplied to obtain the change amount, and this change amount and the conversion coefficient at the reference focus position (long focus side) By adding, the conversion coefficient is logarithmically compressed corresponding to the focal length variable magnification operation and the conversion coefficient is output as data to the camera body.The conversion coefficient read from the interchangeable lens on the camera body side is logarithmically expanded, and this data and the data are decompressed. Since the drive amount of the focus adjustment member is calculated from the focus amount,
The conversion coefficient at the reference focus position (long focus side) and the conversion coefficient change amount per unit movement amount can be set at the time of incorporating the information output circuit in the lens barrel. Therefore, it is no longer necessary to manufacture and stock ICs including ROM for each lens as in the past, which reduces development costs and inventory burdens, and reduces the unit price due to the mass production effect of manufacturing only one IC. effective.

Further, according to the present invention, since it is not the method of outputting the fixed storage information of the ROM, there is an effect that the problem that the lead time until the mass production is prolonged only during the development period of the ROM is eliminated.

Even if the conversion coefficient changes due to a partial change in the lens specifications, before incorporating the information output circuit in the lens barrel,
This can be dealt with by changing the setting of the conversion coefficient or the conversion coefficient change amount per unit movement amount, which has the effect of increasing the degree of freedom in improving the product.

Since the conversion coefficient transmitted from the interchangeable lens to the camera body is logarithmically compressed data, an information output circuit for always calculating an appropriate conversion coefficient corresponding to the variable magnification operation can be easily realized. Then, on the camera body side, it is necessary to logarithmically expand the conversion coefficient which is the logarithmically compressed data read from the interchangeable lens. Therefore, I tried to find the logarithmic expansion by the approximation method,
The circuit or operation algorithm has become simpler.

[Brief description of drawings]

FIG. 1 is a block diagram showing a camera system for automatic focus adjustment to which the present invention is applied, FIG. 2 is a block diagram showing transmission of lens information, and FIG. 3 is a relationship diagram showing functions of lens unique information and encoder setting position. FIG. 4 is a circuit diagram showing the circuit configurations of the adder circuit and the multiplier circuit. CO ₁ , CO ₂ …… Counter, DE ₁ , DE ₂ …… Decoder, AI, BI, C
I, DI, EI …… Lens specific information, DS ₁ , DS ₂ …… Data selector, CJ, DJ, EJ …… Information change amount, ADD …… Adding circuit, MLT
…… Multiplier circuit, ENC …… Encoder.

Claims (1)

[Claims] 1. A focus adjusting member for moving an image forming position of an object to be focused by a focus adjusting optical system, and a driving means on the camera body side when the body is mounted on the camera body. A transmission mechanism for transmitting to the adjustment member, a reference conversion coefficient setting means for setting a conversion coefficient at the reference focus position, and a relative movement amount detection means for detecting a relative movement amount from the reference focus position to the set focus position by a magnification change operation. A change amount setting means for setting a conversion coefficient change amount per unit movement amount; a calculation means for obtaining conversion coefficient data by calculation from a relative movement amount, a conversion coefficient change amount and the reference conversion coefficient; An interchangeable lens for an autofocus camera, comprising a data output means for serially outputting to the main body.