JP2770317B2 - Reflective telephoto lens capable of outputting lens information - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is detachable from a camera body having a built-in phase difference detection type focus detection device, and stores focus detection lens information in a ROM.
The present invention relates to an interchangeable lens capable of storing this information in a camera body and outputting the information to a camera body, and particularly to a reflective telephoto lens.

2. Description of the Related Art Whether or not focus detection is possible in a combination of a focus detection element (for example, a CCD line sensor) on the camera body side and an optical system of an interchangeable lens depends on a projection image on the exit pupil of the CCD line sensor. Is determined by whether or not it is broken. Therefore, in the case of a general refraction lens, it is possible to determine whether or not vignetting occurs in a state where the aperture stop is smallest due to zooming or focusing, so that the aperture value of the smallest aperture stop aperture is used to determine whether or not focus detection is possible. It has been proposed in, for example, Japanese Patent Application Laid-Open No. 60-4915 to store the value AFAvo in the ROM of the lens.

However, since the open aperture value of the reflective telephoto lens is determined by the area of the light speed sandwiched between the outer light beam and the inner light beam (cut by the secondary mirror), it is determined whether or not focus detection is possible. If this normal aperture value is used as the aperture value for use, the aperture value becomes darker than the aperture value corresponding to the outer light beam when there is no vignetting of the inner light beam by the secondary mirror. That is, there is a possibility that it is determined that the focus detection is impossible with the outer light beam, even though the focus can be detected. Although it is conceivable to determine whether or not focus detection is possible based on the position and diameter of the exit pupil, the determination is complicated and cannot be said to be practical.

An object of the present invention is to make it possible to easily and accurately detect the focus when performing focus detection using such a reflective telephoto lens.

Means for Solving the Problems The present invention provides an aperture value which is determined by an outer light beam when there is no vignetting of an inner light beam by a sub-mirror as an aperture value for focus detection possibility determination stored in a ROM of a reflective telephoto lens. It is characterized by using an aperture value.

The aperture value used for determining whether or not focus detection is possible in a reflective telephoto lens is different from a normal open aperture value determined by the speed of light sandwiched between an outer ray and an inner ray, but is determined by an outer ray that is a factor of whether or not focus detection is possible. Because it is an open aperture value,
Whether or not focus detection is possible can be easily and accurately performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the single-lens reflex camera has a photographic lens 11 provided on an optical axis 10, a main mirror 12 provided behind the photographic lens 11, and a film exposure device provided behind the main mirror 12. A surface 13 is provided, and a light beam for imaging that has passed through the imaging lens 11 is reflected upward by the main mirror 12 and guided to a finder optical system (not shown).

At least a part of the main mirror 12 is formed as a half mirror, and a sub-mirror 14 is provided between the half mirror portion of the main mirror 12 and the film exposure surface 13. The focus detection light flux transmitted through the mirror unit is reflected downward by the sub mirror 14 and guided to the focus detection device 15.

At the time of photographing, the main mirror 12 and the sub-mirror 14 are rotated upward and retracted from the optical axis 10, and the luminous flux for photographing that has passed through the photographing lens 11 forms an image on the film exposure surface 13, and It gives an imagewise exposure.

The focus detection device 15 is provided with a sensor substrate 17 to which line sensors (photoelectric conversion element arrays) 16a, 16b, 16c such as CCDs are attached. Among the line sensors 16a to 16c, one line sensor 16a is disposed at a horizontal position including the optical axis 10, and two line sensors 16b and 16c include the optical axis 10 on both sides of the line sensor 16a. Not located in a vertical position. The line sensors 16b and 16c are set at substantially 90 degrees with respect to the line sensor 16a.

A separator lens plate 18 is provided in front of the sensor substrate 17, and the separator lens plate 18 is integrally formed with separator lenses 18a to 18c corresponding to the line sensors 16a to 16c.

An aperture mask 19 is provided immediately before the separator lens plate 18, and the aperture mask 19 is provided with the separator lens plate.
Openings 19a to 19c corresponding to 18a to 18c are formed.

A reflection mirror 20 facing the aperture mask 19 and the sub mirror 14 is provided. The reflection mirror 20 transmits the focus detection light flux reflected downward by the sub mirror 14 to the aperture mask opening 19a.
To 19c and the line sensors 16a to 16c via the separator lenses 18a to 18c.

Between the reflection mirror 20 and the sub mirror 14, condenser lenses 21a to 21c facing the aperture mask openings 1a to 19c are provided.
An opening 22a is provided on the upper surface of each of the condenser lenses 21a to 21c so as to separate the focus detection light flux so as to correspond to the line sensors 16a to 16c having different positions and directions.
There is provided a visual field mask 22 having .about.22c.

Different areas 11a and 11 on the exit pupil plane of the taking lens 11
b, the reference portion light beam a and the reference portion light beam b passing through 11c and 11d are respectively received by the line sensors 16a to 16c, and the light distribution pattern of the image is converted into an electric signal, and the correlation between them is correlated. Automatic focus detection is performed by a device (not shown), and the photographing lens 11 is moved back and forth by a driving mechanism based on a shift signal from the correlator, thereby performing automatic focus adjustment.

In this case, since the line sensors 16b and 16c are also provided at the vertical position in addition to the line sensor 16a at the horizontal position, the focus detection in the horizontal direction and the vertical direction can be performed simultaneously, and the focus detection such as a horizontal line can also be performed. It became possible.

On the other hand, since the line sensor 16a is arranged at a predetermined length including the optical axis 10, there is no problem.
Since 16b and 16c are arranged at the vertical position not including the optical axis 10, when various interchangeable lenses are considered, the focus detection light flux is hardly vignetted, that is, the pupil margin is maximized. It is important to consider.

Now, as shown in FIG. 2, the projected image of the element on the axis is
AF fits without vignetting between the outer and inner rays
(Ranging) is possible. However, when the aperture is replaced with an equivalent aperture (that is, an open aperture value for passage) when there is no vignetting of the inner light beam by the secondary mirror, vignetting occurs in the projected image of the element (as shown by a broken line), and this value is If the data is output to the camera body as a ROM value, it is determined that the measurement is impossible by comparing with the distance limit aperture value of the camera body itself. Therefore, in the present application, the open aperture value determined only by the outer rays is stored in the ROM as the open aperture value for AF (AFAV ₀ ) and output. In the case where the outer light ray goes down (darkens) due to lens movement such as focusing, the value at that time is used.

Also, a normal lens (AV ₀ ≤ AFAV ₀ ) because the normal aperture value is used as the ROM value as the open aperture value used for exposure control
Unlike, AV _0> since a relationship of AFAV _0, it can be determined to be a reflection telephoto lens.

For example, in the case of a refraction lens with a distance measurement limit aperture value AFAV1 of F6.7, an open aperture value (D = ∞) F5.6 An open aperture value after extension (D = 1m) F6.3 _{0 = 5.6, AFAV 0 = 6.3} AFAV1 (6.7)> AFAV 0 (6.3) , and the is determined possible distance measurement.

For reflective lenses, open aperture value (D = ∞) F8 Open aperture value after extension (D = 1m) F8.5 Open aperture value for outside rays (D = ∞) F6.3 Open aperture after outside rays if the aperture value (D = 1m) F6.69, AV 0 = 8, AFAV 0 = 6.69 AFAV1 (6.7)> AFAV 0 (6.69) becomes, it is determined to be the distance measurement.

If this is set to AFAV ₀ = 8.5 as in the case of a normal lens, AFAV1 (6.7) <AFAV ₀ (8.5), and it is determined that distance measurement is impossible.

Next, determination of whether the lens is a reflective telephoto lens will be described.

Since a reflective telephoto lens generally does not have an aperture adjustment mechanism, the open aperture value (AV ₀ ) is equal to the maximum aperture value (AVmax).

ex AV ₀ = F8, AVmax = F8 Therefore, a method of determining that the lens is a reflective telephoto lens from the relationship AV ₀ = AVmax can be considered.

However, similarly to the reflection telephoto lens, there are lenses for which AV ₀ = AVmax for the ROM signal as described below, and it is dangerous to judge only from this relationship.

For example, in the case of a bellows macro lens This lens has an aperture adjustment mechanism and a manual aperture setting member in the lens itself, but cannot have aperture control from the camera body side because it does not have an automatic aperture preset mechanism. That is, when the manual aperture setting member is set to a certain aperture value, the aperture value is set to the open aperture value, and the lens is treated the same as a lens having no aperture mechanism. Thus, the AV ₀ of the lens AVmax
Should store the same value. Note that the same applies to a tilt lens and a soft lens.

FIG. 3 is a circuit diagram of a camera system to which the present invention is applied. (DT) is a light receiving unit for focus detection, which is indicated by 16 in FIG.
It has CCD image sensor rows indicated by a, 16b, and 16c. (IFC)
Is an interface circuit, which controls the operation of the CCD image sensor array, performs A / D conversion of a signal read from the CCD image sensor array, and transmits the signal to a microcomputer (COM) through a data bus (DBAF). , The end of the charge storage operation of the CCD image sensor array is determined by the interrupt input terminal (IN
It has a function to transmit to T ₁ ). The charge accumulation time in the CCD image sensor array is controlled by the output of a light receiving unit (not shown) that monitors the brightness of the subject.

(MOAF) is a lens drive motor for AF, (MOA)
Is a motor control circuit, and signals from the output ports (p ₀ ) and (p ₁ ) of the microcomputer (COM) are forward rotation, reverse rotation, brake,
Perform each control of OFF. (DPA) is a display unit for displaying a moving direction of the lens, a focus and a focus detection failure warning based on signals from the output ports (p ₂ ) and (p ₃ ) of the microcomputer (COM).

(ENL) is an encoder that outputs a pulse to monitor the lens drive (motor rotation amount) by the lens drive motor (MOAF), and (ENAP) outputs a pulse to monitor the lens stop-down amount It is an encoder. (SEC) is when the output port (p ₄ ) is at “Low” level and when it is at “High” level, the aperture encoder (ENA
P) are data selectors for sending pulses from the input terminal (CNTR) for the event counter. An event counter is provided inside the microcomputer (COM), data is preset in the event counter, and the content of the event counter is counted down every time a pulse is input to the terminal (CNTR), and the content of the event counter is set to 0. , An interrupt is triggered.

(S ₁ ) is a photometry switch that is closed at the first stage of pressing the release button. The closing signal of this photometry switch (S ₁ ) is input to the interrupt input terminal (INT ₀ ) of the microcomputer (COM). is input to the port (p _5). (P ₂ ) is a relays switch that is closed at the second stage of pressing the release button, and a closing signal of the release switch (S ₂ ) is input to the input port (p ₆ ). (S ₃ ) is a reset switch which is closed upon completion of the exposure control operation and opened upon completion of winding and charging. The closing signal of the reset switch (S ₃ ) is inputted to the input port (p ₇ ). You.

(GV) is a power supply circuit that operates when the power supply control signal (PWC) output from the output port (p ₈ ) is at “Low” level. The power supply circuit (GV) outputs a high voltage (HV) and a low voltage (LV) based on the output of the power supply battery (BA). The high voltage (HV) serves as a power source for the light receiving unit (DT) and the interface circuit (IFC). In addition, the low voltage (LV) is indicated by the display unit (DPA), encoder (ENL), (ENAP), data selector (SEC), film sensitivity reading circuit (ISD), lens circuit (LEC), and photometry And power supply for A / D conversion circuit (MEC), decoder driver (DDR), motor control circuit (MDA), (MDF), display unit (DS
P) and the microcomputer (COM) receive power directly from the power battery (BA) via the power line (EV).

(ISD) is a film sensitivity reading circuit which reads ISO data indicating film sensitivity on a film container and outputs a film sensitivity reading circuit selection signal (CS) from an output port (p ₉ ).
When IS) becomes "Low" level, the film sensitivity data is serially transmitted to the serial input terminal (SIN) in synchronization with the serial clock (SCK) from the microcomputer (COM). (LEC) is a lens circuit provided in the interchangeable lens. This lens circuit (LEC) is disclosed in, for example,
It has a circuit configuration disclosed in Japanese Patent No. 40408,
When the lens circuit selection signal (CSL) from the output port (p ₁₀ ) becomes “Low” level, various data stored in the ROM in the lens circuit (LEC) is synchronized with the serial clock (SCK). Transmits serially to the serial input terminal (SIN). Here, data fixedly stored in the ROM in the lens circuit (LEC) will be described.

Table 1 shows the stored contents of the ROM in the lens in the case of the reflective telephoto lens. At address 011, data common to all lenses is fixedly stored as an attachment signal (ICP). Open aperture value (Avo) at address 021, address 03
The maximum aperture value (Avmax) is fixedly stored in 1, and in the case of a reflective telephoto lens, the aperture is fixed, so that Avo = Avmax. The address 041 stores the data of the point distance (f). The conversion coefficient (K) for converting the defocus amount into the drive amount of the lens driving motor (MOAF) is stored at the address 051. Address 061 stores data of the aperture change amount (ΔAv) due to the zooming.
In the case of a reflective telephoto lens, ΔAv = 0. Address 071 contains data on the aperture value (AFAvo) for focus detection,
Address 081 contains areas (PO ₁ ) and (PO ₂ ) off the optical axis
Is stored as to whether or not focus detection is possible. In the case of a reflective telephoto lens, an open aperture value determined from the outer diameter of the exit pupil is stored as AFAvo. Further, as the off-axis distance measurement possible / impossible data, data indicating impossibility is stored.

(DSP) is a display circuit that performs display based on display data sent from the microcomputer (COM). (NEC) is a photometry and A / D conversion circuit. When a low voltage (LV) power supply from the power supply circuit (GV) is started, the photometry operation is started, and the A from the output port (p ₁₂ ) is started. / D conversion enable signal (ADEN)
Becomes "Low" level, A / D conversion is repeated at a constant cycle. Then, photometry and A / D from the output port (p ₁₁ )
When the conversion circuit selection signal (CSME) goes low, A /
The D-converted and latched data is sent to the microcomputer (COM) in synchronization with the serial clock (SCK). (DDR) is a load driving circuit that decodes data sent from the microcomputer (COM) through the data bus (DBDR) and drives a load according to the decoding result. Loads include a release magnet (RLM), an aperture control magnet (APM), a front curtain control magnet (1CM), a rear curtain control magnet (2CM), and a charge motor (MOCH) for film feed and exposure control mechanisms. And its driver (MDF). X is an oscillator.

Hereinafter, the operation of the camera system will be described with reference to the flowcharts of FIGS. In the following description, the symbol “#” means a program step number. When the release button is operated, the photometry switch (S ₁ ) is closed by pressing the first step, an interrupt signal is input to the interrupt input terminal (INT ₀ ), and the microcomputer (CO
M) starts the operation from the interrupt routine INT ₀ of Figure 4. First, the power supply control signal (PWC) output from the output port (p ₈ ) is set to “Low” level to operate the power supply circuit (GV) (# 1). Next, the interface circuit (IF
C), the reference clock (CKOUT) is output to the display circuit (DSP), the photometry and A / D conversion circuit (MEC), and the CCD initialize operation for sweeping out the charge accumulated in the CCD is performed (# 2, #
3). Next, the charge storage operation of the CCD is started. At the end of the charge storage operation, an interrupt signal to the interrupt input terminal (INT ₁ ) is accepted, and an A / D conversion enable signal from the output port (p ₁₂ ) is received. (ADEN) is set to the “Low” level, and the photometric value is A / D converted (# 4, # 5, # 6).

Next, the process proceeds to a photometry routine, in which the lens data from the interchangeable lens and the film sensitivity data (IS
O data) (# 7, # 8). Next, the state of the flags IFF ₁ and IFF ₂ is determined. IFF ₁ is a flag that is set to 1 when the focus state is reached, and IFF ₂ is a flag that is set when photometric data is acquired after the focus state is reached. Therefore, when the subject is out of focus or when the subject is in focus and the photometric data has not been captured, the photometric data is captured. When the data is captured after focusing, the flag IFF ₂ is set to 1 and the process proceeds to the calculation routine. I do. If the flags IFF ₁ and IFF ₂ are both 1,
The process directly proceeds to the calculation routine without inputting the photometric data (# 9 to # 13).

In the calculation routine, first, in step # 14, it is determined whether or not the lens mounting signal ICP has been input. If the signal has been input, the process proceeds to step # 15, and if not, the process proceeds to step # 16. In step # 15, it is determined whether or not the open aperture value Avo is larger than the open aperture value AFAvo for focus detection (Avo> AFAvo). If the reflective telephoto lens is Avo> AFAvo, # 16, and if Avo≤AFAvo, normal replacement is performed. Because it is a lens
Move on to step 19. First, when no lens is mounted and when a reflective telephoto lens is mounted, it is natural that aperture control cannot be performed, and the aperture must be regarded as fixed. Therefore, in step # 16, the exposure time Tv is calculated by adding the ISO value Sv indicating the film sensitivity to (photometric data) = Bv-Av (Bv is the subject brightness, Av is a fixed aperture value). Then, it is determined in step # 17 whether or not the lens is mounted. If the lens is not mounted, the exposure time is displayed in step # 18, and the F value is displayed as a warning (for example, "-"). On the other hand, if the lens is attached, it is a reflective telephoto lens, and the calculated exposure time Tv and the fixed aperture value (open aperture value Avo = maximum aperture value A
vmax) and are displayed in step # 21. If it is determined in step # 15 that the lens is not a reflective telephoto lens, then in step # 19, (photometric data) = Bv− (Avo + ΔAv), and Avo +
The exposure value Ev is calculated by adding ΔAv + Sv, and the aperture value Av and the exposure time Tv are calculated by performing a program exposure calculation (# 20) based on the exposure value Ev, and are displayed (# 2).
1).

When the above operation is completed, 1 is set to the flag AFF. This flag is set to 1 when the exposure calculation ends. Next, the state of the flag CF is determined, and CF is determined.
If = 1, the process proceeds to the AF routine. This flag CF indicates that if the CCD charge accumulation operation is completed during the photometry routine or calculation routine, and if the exposure calculation has not been completed at least once, the remaining exposure is taken after the data from the CCD is fetched. It is provided for performing an operation and then moving from this step to the AF routine.

In step # 24, it is determined whether or not the release switch (S ₂ ) is closed, and in step # 25, it is determined whether or not the exposure control value is calculated from the in-focus photometric data.
If all the conditions are satisfied, the process shifts to the Rochetz routine to perform the exposure control operation. On the other hand, if the condition is not satisfied, it is determined whether or not the photometry switch (S ₁ ) is closed in step # 251. If it is, the process returns to the photometry routine. Performs routine operations.

In the stop routine, first reset all flags, set the output port (p ₄ ) to “Low” level, and display
The data to be turned OFF (state in which nothing is displayed) is displayed on the display circuit (D
SP) to stop the motor (MOAF), stop the output of the reference clock (CKOUT), disable the power supply circuit (GV), disable the A / D conversion by setting the signal (ADEN) to "High" level And the microcomputer (COM) stops operating (# 26 to # 3
2).

Next, the operation of the AF routine will be described with reference to FIG.
When the CCD accumulation operation is completed, the interface circuit (I
FC) to the interrupt input terminal (INT ₁ ), and the operation from # 39 is performed. First, in step # 39, it is determined whether or not the interchangeable lens is attached. If the interchangeable lens is attached, the process proceeds to step # 40. Data acquisition, focus detection, lens driving operation, and the like are not performed. In the step # 40, the analog signals corresponding to the three rows of CCDs output from the light receiving unit (DT) are converted into an interface circuit (IFC).
A / D conversion is performed sequentially and is taken into the microcomputer (COM). Then, the flag CF is set to 1 and the flag AEF is set to 1
If the flag AEF is 0, it means that the first photometry routine and the arithmetic routine have not been completed, so the return address (the execution when the interrupt of INT ₁ is interrupted) is determined. Return to step). When the photometry routine and the calculation routine are completed, CF = 1 is determined in step # 23, and the process returns to the AF routine. If AEF = 1 in step # 42, the process immediately shifts to the AF routine when the capture of the CCD data is completed.

In the AF routine, first, the flag CF is set to 0 and AF
To determine whether or not has become a Avo> K _2. Where K ₂
Represents the aperture value of the limit capable of focus detection by the light receiving section 16a, when the AFAvo> K ₂ processing proceeds to step # 51 because it is impossible to focus detection over the entire light receiving unit 16 a to 16 c.
On the other hand, it is determined whether next AFAvo> or K ₄ when the AFAvo ≦ K _2. K ₁ is the light receiving part 16b, 16c according illustrates the aperture limit that can focus detection, AFAvo ≦ K ₁ i.e. K ₁ <a # 48 only the focus detection in AFAvo ≦ K ₂ if the light receiving portion 16a is possible Move to step. Since the aperture value if AFAvo ≦ K ₁ can be focus detection in all regions, it is next of whether it is possible to focus detection outside the axis determination. This is because off-axis focus detection may not be possible even when the aperture value is bright, for example, when the exit pupil position is close. At this time, only the focus detection by the light receiving unit 16a is performed. On the other hand, when the focus can be detected off-axis, the focus is detected for all the light receiving units 16a to 16c.

Then, it is determined whether or not reliable data is obtained for each light receiving unit (focus detection area). If all the data is unreliable, the process proceeds to step # 51 (# 4).
9, # 50). And sets a flag IFF ₂ to 1 at step # 51. This is to enable the exposure control operation to be performed with or without focusing when focus detection is not possible. Then, a warning indication that it is impossible to detect, to start the CCD storage operation, as allowed the interrupt INT _1, returns to the return address in the metering routine and calculation routines.

If it is determined in step # 50 that at least one reliable data has been obtained, the process proceeds to step # 60 to perform statistical processing. The statistical processing includes, for example, adopting a signal of the rearmost focus, or adopting a defocus amount such that the plurality of subjects fall within the depth of focus when a plurality of data are within a predetermined defocus amount. There is processing. Then, it is determined whether or not the defocus amount obtained by the statistical processing is within the focus area. If the defocus amount is outside the focus area, the process proceeds to step # 62. #
In step 62, the defocus direction is displayed, the defocus amount is multiplied by the conversion coefficient (K), and the drive amount of the lens driving motor (MOAF) is calculated (# 63). ) (# 64). Then, interruption of the event counter is enabled (# 65), and the lens driving motor (MOAF) is operated (# 66). And
Return to the return address of the photometry routine and the calculation routine. Thereafter, the photometry routine and the calculation routine are repeated while driving the lens. Further, a pulse from an encoder (ENL) for monitoring the lens driving amount is input to the event counter from a terminal (CNTR) via a selector (SEC), and the content of the event counter is decremented.

When the content of the event counter becomes 0, an interrupt (EVC interrupt) by the event counter is applied, and the operation from step # 100 in FIG. 6 is performed. # 100 steps, AF
It is determined whether or not the camera is operating. In this case, since the AF operation is being performed, the process proceeds to step # 101, the motor (MOAF) is stopped, and the CCD accumulation operation is started to perform focus detection for confirmation. is (# 102), the interrupt from the interrupt input terminal INT ₁ after the variable (# 103), the process proceeds to photometry routine from the start of # 7. Step # 104 will be described later.

In the flow of FIG. 5, when it is determined in step # 61 that the focus is achieved, the process proceeds to step # 70, and the focus is displayed. Then, in the step # 71, the flag IFF _{1 is set} to 1
Is set, and the process proceeds to the photometry routine from step # 7. Therefore, once the in-focus state can be confirmed,
As long as the photometric switch (S ₁ ) is closed, focus detection and lens driving are not performed.

In step # 24 of FIG. 4, the release switch (S ₂ is closed, the 1 in the flag IFF ₂ is set at step # 25, the process proceeds to a six view exposure control routine. First, The AF display is turned off in step # 75, the release magnet (RLM) is operated in step # 76, and the operation of the exposure control mechanism is started. Is determined (# 77, # 78), and when the lens is not mounted or the reflective telephoto lens is mounted, the process proceeds to step # 83,
No aperture control operation is performed. On the other hand, if a normal lens is attached, first, in step # 79, it is determined whether or not the control aperture value (Av) is equal to the open aperture value (Avo). If it is Avo, similarly, the process proceeds to step # 83. On the other hand, if Av ≠ Avo, the number of steps (Av−Avo) is set in the event counter (EVC), the port (p ₄ ) is set to “High” level, and the pulse from the encoder (ENAP) that monitors the amount of narrowing is set. Is output from the selector (SEC) (# 80, # 81, # 82). And # 8
3, Wait a certain time in step # 84. During this time, the narrowing-down operation is performed, and when the event counter is interrupted, #
At step 104, the aperture magnet (APM) is operated to stop down. And after a certain time,
The raising of the reflection mirror has been completed, and the front curtain magnet (1C
M) to start the running of the front curtain and count the exposure time (# 85, # 86). When the counting is completed, the front curtain magnet (2CM) is operated to start the rear curtain running (# 87). Then, wait for the reset switch travel of the rear curtain is completed (S ₃₎ is ON (# 88). When the reset switch (S ₃ ) is turned on, the motor for charging (MOCH) is operated to wind the film and charge the exposure control mechanism. This operation is completed, and the reset switch (S ₃ ) is turned off. Wait until it becomes (# 89, # 90). When the reset switch (S ₃ ) is turned off, the finger is released from the release button, and waits for the photometry switch (S ₁ ) to be turned off (# 91). When the photometry switch (S ₁ ) is turned off, the operation of the stop routine is performed, and then the operation is stopped until the photometry switch (S ₁ ) is turned on and the microcomputer (COM) is started.

In the above embodiment, the on-axis ranging frame A and the off-axis ranging frames B and C are provided as the ranging frames, and the ranging frames A, B and C are respectively assigned to the ranging areas I to IV. Although the area is divided, the ranging frame is, for example, the ranging frame A,
Only B and ranging frames A and C may be used. Alternatively, only the distance measurement frame A may be divided into regions within the distance measurement frame A as in the embodiment. Alternatively, three distance measuring frames A, B, and C may be provided so that the area within the distance measuring frame A is divided and the area within the distance measuring frames B and C is not divided.

Although only the P mode (program exposure mode) is shown as the exposure control mode, the A mode (aperture priority AE mode), the S mode (shutter speed priority AE mode), the M mode
Also in the mode (manual mode), when a reflective telephoto lens is mounted, it is different from a normal lens, but a response is required. That is, in the A mode, the exposure time is automatically set for the fixed aperture, as in the P mode. In the S mode and the M mode, the exposure time is set to the fixed aperture.

Effects As described above, according to the present invention, the aperture value used for determining whether or not focus detection can be performed by the reflective telephoto lens is determined by the outer light beam when the inner light beam is not vignetted by the secondary mirror of the reflective telephoto lens. Therefore, whether or not focus detection can be performed can be easily and accurately determined.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical system of a focus detection device to which the present invention is applied, FIG. 2 is a diagram showing the principle of the present invention, and FIG. 3 is a diagram showing an overall circuit configuration of a camera system according to an embodiment of the present invention. 4 to 6 are flowcharts showing the operation. : Focus detection device,: Lens ROM

────────────────────────────────────────────────── (5) References JP-A-61-159611 (JP, A) JP-A-60-4915 (JP, A) JP-A-62-75410 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G02B 7/11

Claims (1)

(57) [Claims] 1. An interchangeable lens which is detachable from a camera body having a phase difference detection type focus detection device built therein, and which can store lens information including an aperture value for determining whether or not focus detection is possible in a ROM and output this information to the camera body. 3. A reflective telephoto lens capable of outputting lens information, wherein an aperture value determined by an outer ray of the reflective telephoto lens is stored in a ROM as an aperture value signal for determining whether or not focus detection of the reflective telephoto lens is possible.