JPH0617930B2 - Distance measuring device for interchangeable lens type camera - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for an interchangeable lens camera equipped with an automatic focusing device, and more particularly, to a camera focusing device for determining whether a photographing lens is in focus or not in focus. The present invention relates to an apparatus for detecting focus distance information from a camera in which a photographic lens is in focus when the focus adjustment is performed by the signal.

2. Description of the Related Art In the conventionally proposed triangulation type automatic focusing device, information on the distance between the camera and the subject, that is, the subject distance can be obtained from the distance measurement result, but it seems to be proposed for a single-lens reflex camera. The detection system is in focus, out of focus, or out of focus when the focus is off, that is, when the focus is closer to the subject than the target (so-called front focus) or at a long distance. In the case of an automatic focus adjustment device of the type that detects whether the subject is in focus (rear focus) and drives the focus adjustment optical system of the shooting lens according to the detection result to detect the focus, You cannot get distance information. Conventionally, it is known that the position information of the focus adjusting mechanism of the taking lens is converted into a resistance value or the like and transmitted to the camera body, but when accurate information cannot be obtained and the taking lens is an exchangeable type. It is necessary to provide such a conversion device and a signal transmission device for each lens.

It is an object of the present invention to provide a circuit or mechanism on the camera side for automatic focus adjustment in a lens interchangeable camera that automatically detects and adjusts the in-focus and out-of-focus directions as described above. It is an object of the present invention to provide a distance measuring device that can obtain object distance information in a form that can be electrically processed by utilizing the above.

In order to achieve this object, in the present invention, a pulse is generated according to the momentum of the mechanism on the camera side of the lens drive mechanism of the automatic focusing device, and the pulse is generated from a predetermined initial position of the mechanism to the in-focus position. The subject distance information is obtained from the count value according to the amount of movement of the subject and a predetermined conversion coefficient from the interchangeable lens side.

Embodiment FIG. 1 is a sectional view showing an essential part of a focus adjusting mechanism according to an embodiment of the present invention. Among the illustrated members, reference numerals (2) to (56)
Those with a mark are built into the camera body, and reference numerals (60) to (76)
Those marked with are built into the interchangeable lens. In the figure, (2) is a drive shaft of a motor which will be described later, and a pinion (4) is fixed to the tip thereof. The pinion (4) meshes with the friction gear (6), and the friction gear (6) is connected to the intermediate gear via the friction spring washer (8).
Friction-coupled to (10). The intermediate gear (10) is fixed to the shaft portion by caulking so as to rotate integrally with the first reduction gear (12), and the rotation of the intermediate gear (6) rotates with the first reduction gear (12) and The second reduction gear (1
It is transmitted to the lens drive gear (16) via 4) and
It is directly transmitted to an encoder gear (20) that rotates integrally with an encoder plate (18) described later. The friction gear (6)
The friction spring washer (8) is loosely fitted on the shaft portion of the first reduction gear (14).

The encoder plate (18) is fixed to the encoder gear shaft (22), and as shown in FIG. 2, a large number of light shielding pieces (18a) and light shielding portions (18b) are alternately formed at the same pitch. , Is shaped like a quiver. (24) is a photocoupler, in which the light emitting diode and the light receiving element face each other across the passage of the light shielding piece (18a), and the light incident from the light emitting diode to the light receiving element is accompanied by the rotation of the encoder plate (18). It is periodically blocked by the light blocking piece (22a). The rotation direction detection rod (26) is located in front of the encoder plate (18) (left side in FIG. 1) of the encoder gear shaft (22).
The annular portion (26a) is elastically wound around the detection rod (26), and when the encoder plate (18) is rotated in either the clockwise or counterclockwise direction, the detection rod (26) first moves to the encoder plate (22). Rotate together to abut the contact piece (28) or (30) and bring the contact piece (28) or (30) into contact with the ground terminal (32) or (34). Slip occurs with the annular portion (26a) and only the encoder plate (18) rotates. When the rotation of the encoder gear shaft (22) stops, the detection rod (26) is pushed back by the contact piece (28) or (30) and slips in the opposite direction to the encoder gear shaft (22). , Return to the neutral position shown by the solid line in the figure.

The lens drive gear (16) is movably supported in the axial direction by bearings (36) and (38), and is urged toward the front of the camera (left side in FIG. 1) by a spring (40). Lens drive gear (1
A cylindrical hollow portion (16a) and a hole (16b) with an oval cross section following it are formed in the inside of 6), and a connecting shaft (42) is fitted into this, and the connecting shaft (42) is at the rear end. A washer is fitted and is coupled to the lens drive gear (16) for pivotal movement therewith. The tip end of the connecting shaft (42) is fitted and coupled to the lens lock sleeve (44), and the lens lock sleeve (44)
Is rotatably supported by the interchangeable lens mounting bayonet seat plate (46) in the axial direction. The tip of the connecting shaft (42) is formed with a projection (42a) in the shape of a horizontal line, and the lens lock sleeve (4
It is exposed to the outside through the tip opening of 4). The lens lock sleeve (44) is fitted into the bayonet mount part of the camera, and when the mount part of the interchangeable lens described later is fitted and rotated by a predetermined amount, it fits into the lock hole (64) on the rear end surface of the interchangeable lens barrel,
Lock the interchangeable lens in the mounting position so that it does not rotate. Reference numeral (48) is a lens lock release button, which is axially movably supported by a camera front cover (50) and a support plate (52) inside the camera body, and is moved forward by a spring (54) (to the left in FIG. 1). ) Is urged to protrude. The connecting plate (56) fixed to the lens lock release button (48) fits into the circumferential groove (44a) of the lens lock sleeve (44), and the lens lock release button (48) resists the spring (54). When pushed in, the lens lock sleeve (44) is also retracted toward the inside of the camera (right side in the figure), and retracts from the lock hole (64) of the interchangeable lens together with the connecting shaft (42).

Reference numeral (60) denotes a driven shaft which is connected to the connecting shaft (42) and is rotatable together with the connecting shaft (42), and a horizontal one-character concave portion (recessed with a tip projection of the interlocking shaft (42) fitted and engaged at its rear end. 60a) is formed, a helicoid drive gear (66) is fixed near the tip, and the rear end is a lock hole (6) on the rear end surface of the fixed barrel (62) of the interchangeable lens barrel.
4). The helicoid drive gear (66) meshes with the helicoid gear (68a) formed on the helicoid ring (68), and the lens holding cylinder (7
A helicoid screw (68a) that fits into the helicoid screw (70a) formed on the outside of (0) is formed.When the helicoid ring (68) is rotated by the rotation of the driven shaft (60), the lens holding cylinder (70) is guided in a straight groove (not shown) and the shooting lens (7
2) Move forward or backward in the optical axis direction of (74) to move the lenses (72) and (74) back and forth in the optical axis direction. The linear movement of the lens holding cylinder (70) or the rotation of the helicoid ring (76) is restricted so as to stop at the positions corresponding to the infinity focus position and the closest focus position of the lenses (72) (74). . (76) is an operation part for manual focus adjustment, and when this is rotated, the helicoid screw (68a)
The lenses (72) and (74) are moved forward or backward via the (70a), and the helicoid gear (68a) and the helicoid drive gear (6
6), the driven shaft (60), the connecting shaft (42), the lens drive gear (16), the second, the first reduction gear (14) (12) is transmitted to the intermediate gear (10), the intermediate gear (10). Although the encoder plate (18) is rotated by 10), the motor drive shaft (2) side is not driven by the slip of the friction spring washer (8).

In such a configuration, when the mount portion of the interchangeable lens is fitted into the opening of the bayonet seat plate (46) of the camera body,
When the lens lock sleeve (44) is pushed in by the rear end surface of the fixed barrel of the interchangeable lens barrel and the interchangeable lens is rotated in the prescribed direction by a predetermined amount, the lens lock sleeve (44) is fitted into the lock hole (64) and the interchangeable lens Is locked and connected to the camera, and the connecting shaft (42) is connected to the driven shaft (60).
At this time, the projection (42a) at the front end of the connecting shaft (42) and the driven shaft (60)
Even if it does not fit well into the recess at the rear end, it fits if the interlocking shaft (42) is slightly rotated by the motor as described later.

When the motor shaft (2) is rotated by being controlled by an automatic focusing circuit as described later, the friction gear (6) and the intermediate gear (1
The lenses (72) and (74) are moved forward and backward through the conduction system from 0) to the helicoid gear (68a). At the same time, the intermediate gear (6) is connected to the encoder plate (1) via the encoder gear (22).
8) is rotated, and the light shielding piece (18a) intermittently and periodically interrupts the optical path from the light emitting element to the light receiving element of the photocoupler (24), and the light receiving element changes the rotation amount of the code plate (18). A corresponding number of pulse signals are output. Even when the lenses (72) (74) are manually moved forward and backward by the manual operation part (76), the encoder plate (18) is rotated as described above, and the pulse corresponding to the rotation amount is output. . When the lenses (72) (74) are stopped at infinity or at the most recently focused position, the friction gear (6) slips and the motor shaft (2) can continue to rotate, but after the intermediate gear (10) The conduction system of is stopped, the encoder plate (18) does not rotate, and no pulse is generated.

FIG. 3 shows a pulse counting circuit using the configuration of FIG. The contacts (28) (30) for detecting the rotation and the direction of the encoder plate (18) are provided with the ground terminal (32) when the detection rod (26) is rotated clockwise or counterclockwise as described above. Alternatively, it is brought into contact with (34) and grounded. These contacts (28) and (30) are connected to the power source (Vcc) through the resistors (R ₁ ) and (R ₂ ), respectively, and the OR gates through the inverters (INV ₁ ) and (INV ₂ ). (O
It is connected to the input end of R ₁ ). The output terminal of the OR gate (OR ₁ ) is connected to the one shot (OS ₁ ) and the contact (28) or
When (30) is grounded, a high level (hereinafter referred to as "H") signal is output from the OR gate (OR ₁ ) and one shot (OS ₁ )
One pulse signal is output from S, and the pulse signal is S
The signal is input to the set input terminal (S) of the R flip-flop (SR ₁ ), and the “H” signal is output from the Q output terminal of the SR flip-flop (SR ₁ ). As a result, the transistor (Tr ₁ ) becomes conductive and the light emitting diode (LED) of the photocoupler (24) is turned on. The light enters the photodiode (PD) as the light receiving element of the photocoupler (24), and when the encoder plate (18) rotates, the light from the light emitting diode becomes intermittent, and from the photodiode (PD), A signal corresponding to the incident light by the light emitting diode (LED) and the encoder plate (18) is output, and this pulse signal is amplified by the operational amplifier (OP ₁ ),
This output is converted to a pulse signal by the comparison circuit (COP) and input to the programmable frequency divider (PFD), which is
An output obtained by dividing the input pulse is generated according to a program value described later. On the other hand, the contacts (28) and (30) are also connected to the set terminal (S) and the reset terminal (R) of the SR flip-flop (SR ₂ ), respectively, depending on which contact is grounded, S
An "H" signal or a low level (hereinafter referred to as "L") signal is output from the Q output terminal of the R flip-flop (SR ₂ ), and a programmable frequency divider (PFD) and an up / down counter (UDC) are output according to the signal. ) Up-counts or down-counts the pulse output from the comparison circuit (COP). Pulse oscillator
(OC), AND gate (AN ₁ ) Counter (CNT) is OR gate
Counter from one-shot (OS ₁ ) at falling edge of (OR ₁ ) output
After the pulse signal is input to the reset terminal (Re) of (CNT), the counter (CNT) counts the pulse signal from the oscillator (OC), and when it reaches a predetermined value, that is, after a certain period of time, S
This is for applying a signal to the reset terminal (R) of the R flip-flop (SR ₁ ), setting its Q output to “L”, and turning off the diode.

4 and 5 show a circuit unit for automatic focus adjustment and focus distance detection, FIG. 4 shows a circuit unit for automatic focus adjustment, and FIG. 4 shows an automatic focus adjustment unit. FIG. 4 shows a circuit for utilizing the data in the shift register until the control circuit for inputting the information and inputting the information on the focusing distance to the shift register. In FIG. 4, the focus detection device (80)
Detects the light at the position optically equivalent to the film surface of the camera, that is, the light on the imaging surface of the taking lens (72, 74), and the focusing lens is focused farther than the target object. When it is necessary to extend the taking lens to focus closer, it is necessary to extend the "H" signal from the terminal (b) so that the taking lens is focused closer and the taking lens is focused farther. The "H" signal is output from the terminal (a) at certain times, and the "H" signal is output from both terminals (a) and (b) when the shooting lens is focused on the target subject, and the subject is dark. This is a publicly known one which outputs the "H" signal from the terminal (c) when the focus cannot be detected because it is too far or the subject has no contrast. (82) is a lens driving motor, the output shaft of which is the driving shaft (2) of FIG. 1, and its rotation is composed of the friction gear (6), the friction spring washer, etc. of FIG. A lens drive mechanism (86) from the intermediate gear (10) of FIG. 1 to the helicoid gear (68a) via the friction clutch mechanism (84) and the encoder plate of FIGS. 1 and 2.
Reached to (18). The encoder (88) is composed of the encoder plate (18) shown in FIGS. 2 and 3, a photocoupler (24), a light emitting diode (LED), a photodiode (PD), an operational amplifier (OP ₁ ) and the like in the photocoupler. .

The output terminal (c) of the focus detection device is connected to each one input terminal of the AND gates (AN ₁ ) (AN ₂ ) via the inverter (INV ₃ ), and the other input end of the AND gate is The output terminals (b) and (a) of the focus detection device (80) are connected to each other. AND gate (AN ₁ )
The third terminal of is connected to the SR flip-flop (SR ₃ ) via the inverter (INV ₄ ), and the set input terminal (s) of the SR flip-flop indicates that the interchangeable lens has been attached to the camera. One shot (OS ₂ ) that outputs a pulse signal to which the "H" signal is given from the inverter (INV ₅ ) by closing the switch (SW ₁ ) when the lens lock release button (48) returns
Are connected. The output of the AND gate (AN ₁ ) is the OR gate (O
If the "H" signal is input only from the OR gate (OR ₃ ), the motor drive circuit (92) is connected to the motor drive circuit (92) through R ₃ ). Drive the motor (82) in the direction in which the focus is adjusted to (1). The output terminal of the AND gate (AN ₂ ) is the OR gate (OR ₄ ) (OR ₅ )
Connected to the motor drive circuit (92) via an OR gate (O
When only the output of R ₅ ) is “H”, the motor drive circuit (92)
The motor (82) is driven in the lens retraction direction (direction in which the taking lens focuses more on a long distance). The motor drive circuit (92) stops the motor (82) when the “H” signal is input from both OR gates (OR ₃ ) and (OR ₅ ). The output terminals of the OR gates (OR ₃ ) and (OR ₅ ) are further connected to the discriminator (90) via the OR gate (OR ₆ ). When the focusing optical system of the taking lens reaches the infinity focus position or the closest distance focus position and is stopped, the encoder plate (18) stops as described above, and the encoder plate (18) stops.
No pulse is output from (88). Discriminator (90) is OR
The “H” signal is input from the gate (OR ₆ ) and the encoder (88)
When there is no input from the terminal (d), give the "H" signal to the motor drive circuit to stop the motor and
The "H" signal is also applied to the AND gate (AN ₃ ) from (d ′), and at this time S
If the Q output of the R flip-flop (SR ₃ ) is at "H" level, AN
“H” signal from D gate (AND ₃ ) is SR flip-flop (SR ₃ )
Input to the reset terminal (R) of the SR flip-flop (SR
₃ ) is reset and its Q output becomes "L" level.

According to such a configuration, the focus detection device (80) terminal (a)
Or, when the "H" signal is output from (b), the motor drive circuit
Reference numeral (92) rotates the motor (82) in either forward or reverse direction according to which terminal outputs a signal, and the focus detection optical system of the taking lens (in the embodiment of FIG. , The lenses (72) and (74) are driven, and the focus detection device (8
Focus is adjusted according to the output of 0). When the interchangeable lens is attached to the camera body and the switch (SW ₁ ) is closed, the "H" signal from the Q output terminal of the SR flip-flop (SR ₃ ) changes to the OR gate (OR ₄ ), ( It is given to the motor drive circuit (92) through OR ₅ ) and inverted by the inverter (INV ₄ ) and given to the AND gate (AN ₁ ) to send out the signal from the terminal (a) of the focus detection device (80). To the motor drive circuit, and the motor drive circuit drives the motor (82) to drive the focusing optics to the infinity in-focus position.
When the focusing optical system reaches the infinity in-focus position, the pulse output from the encoder (88) is lost, and at this time the OR gate
Since the “H” signal of the SR flip-flop (SR ₃ ) is input from (OR ₃ ), the “H” signal is input from the discrimination circuit (90) to the motor drive circuit (92).
A signal is given and the motor (82) is stopped. As a result, the focus adjustment optical system of the interchangeable lens is set to the infinity in-focus position as the initial position.

FIGS. 6 and 7 show other circuit examples for setting the focusing optical system to the infinity in-focus position when the interchangeable lens is attached to the camera, and the same elements as in FIG. Are given the same reference numerals. In FIG. 6, when the interchangeable lens is attached to the camera body, the switch is switched as in the circuit of FIG.
(SW ₁ ) is closed, the “H” signal from the inverter (INV ₅ ) causes the “H” signal to be output from the one-shot (OS ₂ ) and the SR flip-flop (SR ₄ ) is set. (94) is an AND gate (AN ₄ ) when the power switch of the electronic flash device is turned on.
The "H" signal is applied to one input of. As will be described later with reference to FIG. 5, the terminal (e) outputs the "H" signal when the photometric switch of the camera is closed. Therefore,
The interchangeable lens is attached to the camera, and the electronic flash device (94)
When the power switch of is turned on and the photometric switch is closed, the AND gate (AN ₄ ) applies the “H” signal to the set terminal (s) of the SR flip-flop (SR ₃ ), and its Q output terminal outputs “H” signal. "A signal is output. In general, subject distance information is often used for aperture control during flash photography, so
The circuit shown in FIG. 6 is adapted to set the initial position of the focus adjusting optical system in connection with the flash photographing preparation operation.
The SR flip-flop (SR ₃ ) is reset by a signal from the terminal (d ') of the discriminator (90) shown in FIG. The circuit in Fig. 7 shows "H" from the AND gate (AN ₅ ) when the photometry switch is closed after the interchangeable lens is attached to the camera.
The signal is used to set the SR flip-flop (SR ₃ ). In the embodiment shown in FIG. 4, the lens may be driven immediately after the completion of mounting the interchangeable lens, and the operator may be surprised. With the configuration shown in FIG. 7, the lens is driven only after the operation of the photometric switch. This can be prevented. Moreover, the metering switch is always operated during shooting.

Returning to FIG. 4, the decoder (94) decodes the signal of the exchange coefficient (described later) determined for each interchangeable lens and outputs it to the output terminal (P ₀ ).
~ (P ₇ ) to output a binary signal and set the programmable frequency divider (9
6) divides the output pulse of the encoder (88) with a frequency division ratio according to the signal from the decoder (94), and the same number of pulses for the same focusing distance change amount for both interchangeable lenses. The signal is given to the up / down counter (98). This divider
(96) and up / down counter (98) are (PED) and
Corresponds to (UDC). The output terminal of the OR gate (OR ₄ ) is connected to the control terminal (U / D) of the up / down counter (98), and when the lens retraction signal is output through the OR gate (OK ₄ ), the minute The cycle output is counted up, and when the same signal is not input, it is counted down. Divider (96) and the up-down counter (98) is reset by signal "H" of the AND gate (AN _3), i.e., during initial positioning of the focal optics.

FIG. 8 shows a binary signal generating mechanism for inputting a signal corresponding to the conversion coefficient of each interchangeable lens to the decoder. In the figure, the hatched portion is a conductive portion, on which the contact pieces of the brush (108) fixed to the support arm (108) slide, and the brush is moved according to the position of the support arm (108). "L" from the terminals (j, k, l in the figure) connected to the contacting conductive pieces
The signal, the "H" signal is output from the terminal (i in the figure) of the non-contact conductive piece. The support arm (108) is integrally formed with a sliding plate (116) that is movable in the left and right directions in the figure by pins (112) and (114), and is biased to the right in the figure by a spring (118). Has been done. Reference numeral (120) is a conversion coefficient information transmission pin received by the fixed cylinder of the interchangeable lens, and is provided at a position converted into the conversion coefficient of each interchangeable lens. When the interchangeable lens is attached to the camera body, the transmission pin (120) engages with the support arm (108),
The supporting arm is set at a position according to the conversion coefficient.

Here, the conversion coefficient will be described. Generally, the amount of extension x from the infinite focus position of the focus adjustment optical system of the overall extension type photographing lens and the focusing distance are Can be approximated by Therefore, when the focus adjustment optical system of the photographing lens is moved from the infinity in-focus position by x, the output pulse number n from the encoder (88) and the in-focus distance D are also set. Holds, and K changes when the interchangeable lens changes. Here, if K ₁ = k ₁ · Ko …… (3-1) for a certain lens, equation (2) becomes With other lenses, Ki = ki · ko (3-2) Becomes Therefore, in the lens that satisfies the expression (3-1), if k ₁ is given to the frequency divider (96) in other lenses as the conversion coefficient, the counter that counts the output of the frequency divider (96)
The output of (98) is always data Koφ corresponding to the shooting distance regardless of the lens, as shown in equations (4-1) and (4-2). The decoder (94) and the frequency divider (96) are therefor.

The up / down counter (98) consists of 8 bits, and outputs "H" from any of the output terminals (C ₀ ) to (C ₇ ) according to the count value.
Output a signal. Fixed data output device (102), decoder (10
4), comparator (106), OR gate (OR ₆ ) (OR ₇ ) AND gate (AN ₆ )
(AN ₇ ) is for setting the lens to a predetermined distance focus position (for example, normal focus position) when focus detection is impossible. The predetermined focus distance output from the fixed data output device (102). Is decoded by the decoder (104), the output of the decoder is compared with the output of the amplifier down counter (98) by the comparator (106), and when the latter is large, the "H" signal is given to the OR gate (OR ₆ ). To be The "H" signal from the C terminal of the focus detection device (8C) is input to one input end of the AND gate (AN ₆ ),
The "H" signal input from the OR gate (OR ₆ ) outputs the "H" signal from the output end, and that signal is input from the OR gate (OR ₃ ) to the motor drive circuit (92) and the motor (82) is turned on. Drive in the lens extension direction. When the output of the decoder (104) is larger, the OR gate (OR ₇ ), AND gate (AN ₇ ), OR gate (OR ₇ )
"H" signal is given to the motor drive circuit (92) via ₅ ),
The motor (82) drives in the lens retraction direction. When the outputs of the up / down counter (98) and the decoder (104) are equal, both OR gates (OR ₆ ) (OR ₇ ), both AND gates (AN ₆ ) (AN ₇ )
Output becomes "H", and the motor drive circuit (92) stops the motor (82) in the same manner as when focusing.

In FIG. 5, (SW ₂ ) is a photometric switch that is closed to operate the photometric circuit, and (SW ₃ ) is a release switch that is closed to release the shutter. If the metering switch (SW ₂ ) is closed, the inverter (INV ₆ )
The "H" signal is applied to one input terminal of the AND gate (AN ₈ ) from the divider (122) that divides the clock pulse and the pulse signal is input to the other input of the AND gate (AN ₈ ) at a predetermined cycle. Each time it is applied to the edge, the "H" signal is input to the latch control terminal (L) of the shift register (100) via the OR gate (OR ₈ ), and the shift register (100) outputs the up / down counter (98). Take in.
Also, when the release switch (SW ₃ ) is closed, the one sailboat (OS ₂ ) is given a “H” signal from the inverter (INV ₇ ) and outputs a pulse signal, which signal is output from the OR gate (OR ₈ ). Input to the latch control terminal of the shift register (100) via the shift register (100)
Capture the output of (98).

The presettable down counter (124) is for detecting where the highest "1" of the signal taken in the shift register (100) is, and one of its output terminals is at "H" level. When the output of NOR gate (NOR) is “L” level, the output of (SO) terminal of shift register is still “L” level, and AND gate (AN ₉ ) is opened, the clock is output through it. The pulse is given to the shift register (100) and the down counter (124), the data in the shift register is shifted by one bit to the most significant position side (MSB) every clock pulse, and the down counter (124) Count down. When the least significant “1” of the data in the shift register reaches (MSB) and the “H” signal is output from the terminal (SO), the AND gate (AN ₉ ) is closed and the shift register (1
(00) and the down counter (124) are no longer input with a clock pulse, and a signal is given to the latch circuit (126) through the OR gate (OR ₉ ), and the parallel output end (r ₆ ) of the shift register is The signals on the second, third, and fourth rows are latched from (r ₅ ) and (r ₄ ). Down counter (124) counts to 0 and outputs
NOR gate (NOR) even when all of (Q ₀ ) (Q ₁ ) (Q ₂ ) become “L”
Becomes "H", the AND gate (AN ₉ ) is closed and the latch circuit (126) is latched. Here, the down counter (124) receives "5" by the "H" signal from the OR gate (OR ₈ ).
Are preset, and the number of shifts of the shift register (100) by the clock pulse and the count value of the down counter (124) have the relationship shown in Table 1 below.

If R ₇ which is the least significant bit MSD of the shift register is “1” from the beginning, “H” is output from the terminal (S ₀ ) before any shift pulse is input from the AND gate (AND ₉ ). After the signal is output, the subsequent shift is prohibited, and the output of the latch 126, which latches the latch 126, is decoded by the decoder 128 as shown in Table 2 below. The counter (140) is reset by the pulse from the OR gate (OR ₈ ) and the AND gate (AN ₉ )
In the counter that counts the clock pulse from, the outputs (Q ₀ ) to (Q ₂ ) correspond to the number of shifts in the shift register (100).

The outputs of this decoder (128) and counter (140) are subtraction circuits.
Input to (142). Here, the input of the subtraction circuit (142) is shown in Table 3.
Is weighted like.

Therefore, in the subtraction circuit (142), (Q ₂ × 2 ³ + Q ₁ × 2 ² tQ ₀ × 2)-(F _{3
^{× 2 0 + F 2 × 2}} -1 + F 1 × 2 -2 + F 0 × 2 -3) by performing calculation of calculating the D _v, as described later, and inputs the data to the arithmetic circuit.

Also, the sensitivity of the film used and the guide number data of the electronic flash light emitter are input to the arithmetic circuit (130) from the respective data output devices (132) (134), and the diaphragms obtained as the arithmetic results of the input data The value data is output from the arithmetic circuit (130) and displayed by the display (136) or the aperture control device (13
It is used for diaphragm control in 8).

FIG. 9 is another example of obtaining the data of the conversion coefficient from the lens, and FIG. 10 is a time chart showing the operation of each part of FIG. The left side of the chain line in the figure is the camera body side, and the right side is the interchangeable lens side circuit.

When the metering switch (SW ₂ ) is closed, the one-shot circuit (OS
₃ ) outputs a "High" pulse to set the SR flip-flop (SR ₄ ), and (10 Figure SR ₄ Q) The Q output of the D flip-flop (DF) becomes "Hi" at the falling edge of the next clock pulse.
gh "(B figure DF ₁₀ Q), body side counter (CO ₁₀ ),
The reset state of (CO ₁₁ ) is released. Further, this signal is also sent to the lens side through the terminals (JB ₂ ) and (JL ₂ ) to release the reset state of the counters (CO ₁₂ ) and (CO ₁₃ ) on the lens side. This starts the transfer of various data of the interchangeable lens from the lens to the body.

Counters (CO ₁₀ ), (CO ₁₂ ) are 3-bit binary counters, (CO ₁₁ ), (CO ₁₃ ) are 5-bit binary counters, and counters (CO ₁₁ ), (CO ₁₃ ) are counters (CO ₁₀ ). ), (CO ₁₂ )
It counts up at the falling edge of each of the most significant bits. Decoder (DE ₁₀ ) is counter (CO ₁₁ )
Depending on the output of, the output terminals (do) to (dn) are sequentially set to "High", and these output terminals (do) to (dn) are respectively connected to the data latch registers (LA ₁₀ ) to () from the lens. It is connected to the latch terminal of LA _1n ). Also, the decoder (DE ₁₁ ) is a counter (C
The output terminals (C ₀ ) to (C ₇ ) are sequentially set to “High” according to the output of O ₁₂ ), and these output terminals are connected to the AND circuit (AN
It is connected to one of the input terminals of ( ₃₀ ) to (AN ₃₇ ). The output of the counter (CO ₁₃ ) is connected to the lower 5 bit address terminal of the ROM (RO), and the upper 3 bit address terminal of the ROM (RO) is grounded. Therefore, ROM (R
For O), addresses from "00000000" to "00011111" can be specified.

When the counters (CO ₁₀ ), (CO ₁₁ ), (CO ₁₂ ), and (CO ₁₃ ) are released from reset, ROM (RO) is fixedly stored at this address because address "00000000" is specified. Data is being output, and AND circuit (AN ₃₀ ) ~
It is connected to the other input terminal of (AN ₃₇ ). When the output of the counter (CO ₁₂ ) is “000”, the terminal (C ₀ ) is “High”, so the most significant bit data from the AND circuit (AN ₃₀ ) is the OR circuit (OR ₃₀ ) and the terminal (JB _It is input to the shift register (SR ₁₀ ) via ₃ ) and (JB ₃ ) and is captured at the falling edge of the clock pulse. When the next clock pulse rises, the output of the counter (CO ₁₂ ) becomes “001” and the pin (CB ₁ ) becomes “High”. As a result, the second most significant bit of data is output from the AND circuit (AN ₃₁ ) and is taken into the shift register (SR ₁₀ ) at the falling edge of the clock pulse. Similarly, 8-bit data is sequentially fetched into the shift register (SR ₁₀ ), and when the next clock at which the 8th bit data is fetched rises, the decoder (DE ₁₀ )
Output terminal (bo) rises to "High" (Fig. 9, bo)
Thus, the data of the address is loaded to the shift register (SR ₁₀₎ "00000000" is latched in the register (LA _10).

Further, the counter (CO ₁₂ ) counts the rising edges of the clock pulses described above, so that the most significant bit of the counter (CO ₁₂ ) falls and the output of the counter (CO ₁₃ ) becomes “00001”. Therefore, the address "00000001" is specified in the ROM (RO), and the data from this address is output. Then, similarly to the above, the most significant bit is sequentially loaded into the shift register (SR ₁₀ ), and when the loading is completed, it is latched in the register (LA ₁₁ ). In the same way, proceed to ROM (R
O) address data increases, and the data at that address is transferred through the shift register (SR ₁₀ ) to the register (LA ₁₂ ) ~
It will be latched to (LA _1n ).

The conversion coefficient data described above may be fixedly stored at a predetermined address, and the data of the register corresponding to the address may be connected to the programmable frequency divider (96) via the decoder (94).

When the terminal (bn) of the decoder (DE ₁₀ ) becomes "High", the data required for this camera is read. Therefore, when this terminal (bn) becomes "High", the flip-flop (Fn)
F ₁₀ ) is reset and D is generated at the falling edge of the clock pulse.
The Q output of the flip-flop (DF ₁₀ ) becomes “Low”, the counters (CO ₁₀ ), (CO ₁₁ ), (CO ₁₂ ), and (CO ₁₃ ) are reset and the operation is stopped.

In the case of a zoom lens, if the upper 3 bits of ROM (RO) are designated by data corresponding to the focal length, data that changes depending on the focal length can be obtained. In this case, since the data changes, it is necessary to read it repeatedly.

Here, the count value n / ki of the up / down counter (98)
The principle of the circuit of FIG. 5 for converting the distance into the distance apex value Dv will be described. First, n / ki = N, and Dv = 2log ₂ D, so equations (4-1) and (4-2) give Dv = ko−2log ₂ N (5) (ko = 2 · log ₂ Ko) Become. Here, the value of N is N = 2 ^l・ (1 + a ₁・ 2 ^-1 + a ₂・ 2 ^-2 + a ₃・ 2 ^-3 ) …… (6) (a ₁ , a ₂ , a ₃ are 0 or 1) (l; integer), so equation (5) is Dv = ko-2l-log ₂ (1 + a ₁ 2 ^-1 + a ₂ 2 ^-2 + a ₃ 2 ^-3 ) …… ( 5 ′). Therefore, to find Dv, log ₂ (1 + a ₁ 2
^-1 + a ₂ · 2 ^-2 + a ₃ 2 ^-3 ) should be subtracted. Therefore, if the frequency division ratio and ko are determined in advance so that the relationship in Table 4 can be obtained between the count data of the counter (98) and the distance. The number of shifts, that is, the output α of the counter (140) is 2 ^l · 2 ^α = ²⁵ and α = 5-1. Then, this data is shifted by 1 bit and input to the subtraction circuit (142), so that it becomes 10 −2 l. Also, the decoder (128) converts the data of a ₁ , a ₂ and a _{3 into} the data of log ₂ (1 + a ₁ 2 ^-1 + a ₂ 2 ^-2 a ₃ 2 ^-3 ) as shown in Table 2. Therefore, the subtraction circuit (142) ends up performing the operation (5 ′), and the subtraction circuit (142) outputs Dv.
Data will be calculated.

In the above embodiment, a method for obtaining information on the focal length (or shooting distance) from information specific to the interchangeable lens such as the conversion coefficient and information on the drive amount of the interchangeable lens or the focus adjustment optical system by the encoder in the camera is Even in a manual focus adjustment type camera or lens, the interchangeable lens is temporarily set to an initial position such as an infinite position, the setting is mechanically detected, the counter, frequency divider, etc. are reset, and the subsequent drive amount is detected. It can be used by doing. For this purpose,
If the motor in the drive mechanism as shown in the figure is driven while the manual button is operated to perform manual focus adjustment,
The automatic focusing unit in FIG. 4 can be omitted. Even if the motor is not provided in the camera, the encoder in the camera may output a number of pulses corresponding to the amount of lens extension by the rotation of the distance ring by an appropriate interlocking mechanism.

Further, since the exchange coefficient depends on the focal length of the lens, in a zoom lens other than the front lens extension type, the position of the pin (120) or the position of the pin (120) in FIG. The output data from the interchangeable lens in FIG. 9 may be changed. In the latter case, the ROM in the interchangeable lens is detected by detecting the position of the member (for example, zoom operation ring) that occupies the position corresponding to the focal length of the zoom lens.
The address may be designated, and the data fixedly stored at that address may be read by the camera body.

In the camera, the number of rotations of the lens drive motor is simply counted, and the ROM address in the interchangeable lens is specified by a signal according to the count value. It is also possible to obtain the focal length information. Further, in the above embodiment, the division ratio is changed according to the lens unique data, but the count value of the output pulse of the encoder is logarithmically converted, and the value according to the lens unique data is subtracted from the value. Can also obtain distance information.

As described above, according to the present invention, it is possible to obtain accurate focus distance information for various interchangeable lenses by utilizing the circuit and mechanism for automatic focus adjustment provided in the camera body.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a focus adjusting mechanism according to an embodiment of the present invention, FIG. 2 is a schematic plan view of an encoder section in the mechanism of FIG. 1, and FIG. 3 is a pulse counting circuit utilizing the configuration of FIG. Circuit diagram of FIG. FIG. 5 is a circuit diagram of an embodiment of the present invention, FIG.
Fig. FIG. 7 is a circuit diagram showing a modification of the initial position setting circuit of the interchangeable lens, FIG. 8 is a schematic plan view of the conversion coefficient information output section of the interchangeable lens, and FIG. FIG. 10 is a block diagram showing the other side of the output, and FIG. 10 is a time chart showing the operation of the circuit of FIG.

Claims (4)

[Claims] 1. A focus detection device that receives a subject light that has passed through an interchangeable photographing lens and calculates a defocus amount that is a difference between an image formation position and a planned focus position, and a defocus amount calculated based on the calculated defocus amount. Data for inputting from the taking lens a lens drive control means for driving the taking lens, a pulse generating means for outputting a pulse indicating a lens driving amount for driving the taking lens, and a coefficient indicating a lens movement amount per unit defocus amount Detection means, setting means for setting the taking lens to the initial position, calculation means for calculating the distance to the subject by the defocus amount, the coefficient input from the data detection means, and the pulse generated after being set at the initial position. A distance measuring device for an interchangeable lens type camera, comprising: 2. The setting means for setting the photographing lens to the initial position, wherein the infinity position is set as the initial position, and the photographing lens is driven to the infinity position when the photographing lens is mounted. A distance measuring device for an interchangeable lens type camera according to item 1. 3. The setting means for setting the taking lens to the initial position is characterized by setting the infinity position as the initial position and driving the taking lens to the infinity position when a switch for setting the camera to the operating state is operated. A distance measuring device for an interchangeable lens type camera according to claim 1. 4. The setting means for setting the photographing lens to the initial position, with the infinity position as the initial position, drives the photographing lens to the infinity position when operating a switch for photographing with the flash light emitting device. A distance measuring device for an interchangeable lens type camera according to claim 1.