JPS6310135A - Distance information output device for lens interchangeable type camera - Google Patents

Abstract

PURPOSE:To obtain a focused photograph without losing a chance for photographing, by calculating a different fixed focal position at every photographic lens, in case a distance measurement cannot be executed due to a low contrast of an object to be photographed, and moving the photographic lens to its position. CONSTITUTION:In case an object to be photographed is in a low contrast, in accordance with focal distance information of a photographic lens, which is read from a lens data circuit 18, a fixed focal position in its focal distance, or a position (pan-focus position) where a focused range becomes the widest is derived from a conversion table of an internal ROM of an AFCPU 22. For instance, the pan-focus position is Xm. Subsequently, in case a photographic lens is moved to a position of Xm, a value of an absolute distance counter is counted back, and next, a value of the absolute distance counter in a position where the photographic lens is stopping at present is compared with a value of the absolute distance counter in the pan-focus position, and the number of target moving pulses is calculated. Subsequently, the moving direction of the lens is set, and the photographic lens is moved to the pan-focus position, and returned.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a distance information output device for an interchangeable lens camera, more specifically, a device for obtaining absolute distance information for autofocus (hereinafter referred to as AP) driving, etc. The present invention relates to a distance measuring means in a distance information output device when the contrast is low.

[Prior Art] Distance information output from an interchangeable lens includes absolute distance information and relative distance information. Absolute distance information in autofocus is something that outputs a signal that corresponds to the distance itself, and relative distance information is information about how far the object deviates from the current distance. The relative distance information is, for example, comb Iii! Since it can output distance information with only one electrode, it has the advantage of simplifying the configuration as a distance information output device for interchangeable lenses, but it is more convenient to use absolute distance information for single-lens reflex cameras as system cameras. becomes.

Therefore, the applicant first developed a lens with a configuration suitable for a system camera that allows accurate absolute distance measurement by performing simple calculations on the count output according to the relative distance from the interchangeable lens barrel. A distance information output device for a cross-sectional camera was provided (Japanese Patent Application No. 1983-275251).

By the way, in an autofocus camera equipped with a passive distance measuring device that detects the distance to the subject using subject light information from reflected light from the subject, distance detection becomes impossible if the subject has low contrast. Become.

Therefore, conventionally, many technical means have been provided in which the photographing lens is forcibly moved to the normal focus position when the contrast of the subject is low.

[Problems to be Solved by the Invention] However, when trying to apply this conventional technical means to an AF right-hand camera with an interchangeable lens type, since the common focal point position is different for each taking lens with a different focal length,
- The disadvantage is that it is generally not possible to determine the common focal point position, so that conventional technical means cannot be used.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a distance information output device for an interchangeable lens camera that can be suitably used for an AP left camera with an interchangeable lens.

[Means and effects for solving the problem] In the present invention, when the subject has a low contrast, the focal length of the photographic lens is read, and the normal focal position of the photographic lens or the photographed position is determined based on the read focal length and the absolute distance. Sometimes, the position where the range of focus is widest is determined, the photographing lens is moved to that position, and then the release is made possible.

[Example] Hereinafter, an example in which the present invention is applied to an interchangeable lens type AF right camera will be described.

FIG. 1 is an overall block diagram mainly showing the power supply of a camera system to which the present invention is applied. Power battery 1
1 voltage V. 0 is D C/ when the power switch 12 is opened.
The voltage is boosted by the DC converter 13, and the voltage between the lines R and R is kept at a constant voltage vDD. The main CPU 14, bipolar ■ circuit 15, bipolar 1 circuit 16, strobe control circuit 17, lens data circuit 18, and data pack circuit 19 are connected between the lines Ω0''1, and the power supply control for the bipolar ■ circuit 15 is performed by the main CPU. The power supply control of the bipolar circuit 16 to the data pack circuit 19 is performed by the signal from the power control circuit of the bipolar circuit 15.
This is done using a power control signal from

Focus sensor 20. A/D converter 21. AF CPU
The AF block consisting of 22 is a power supply control transistor 2
3 through the line Do, 1. The main CPU 14 controls the power supply to this AF block.
This is done by controlling the transistor 23 on and off using a signal from the AF power control circuit.

The AF river PU 22 is a circuit for performing AF algorithm calculations, and is connected to an AF display circuit 24 that displays in-focus/out-of-focus. The main CPU 14 is a circuit for controlling sequences of the entire camera such as winding, rewinding, and exposure sequences, and is connected to a display circuit 25 for displaying other than the above-mentioned focus display. Bipolar ■Circuit 1
Reference numeral 5 denotes a circuit including various drivers necessary for camera sequences such as winding and rewinding motor control, lens drive, and shutter control, and is connected to an AF motor drive circuit 26, an AP auxiliary light circuit 27, and the like. The bipolar 1 circuit 16 is a circuit mainly responsible for all light, and has an i11 optical element 28. The strobe control circuit 17 is built-in,
Alternatively, it is used to control light emission of an external strobe 29. The lens data circuit 18 has an AF that differs for each interchangeable lens.

This circuit stores unique lens data necessary for photometry and other camera controls. Among the lens data contained in this lens data circuit 18, data necessary for AF includes a lens magnification coefficient (zoom coefficient), a macro identification signal, and an absolute distance coefficient fia+b.

AF accuracy threshold ETh, lens movement direction.

This is the open F value, etc.

The bipolar ■circuit 15 monitors the state of the power supply voltage VDD, and when the electric FA voltage drops below the specified voltage, it sends a system reset signal to the main CPU 14, and supplies power to the bipolar ■circuit 15 to data pack circuit 19.
Furthermore, the power supply to the AP labbook consisting of the focusing sensor 20° A/D converter 21 and the AF CPU 22 is cut off. Power is supplied to the main CPU 14 even if the voltage is below the specified voltage.

FIG. 2 is a system diagram showing the transmission and reception of signals centering on the AP lab book. The AF CPU 22 and the main CPU 14 transmit and receive data through a serial communication line, and the direction of the communication is controlled by a serial control line. The content of this communication is
These are unique lens data within the lens data circuit 18 and absolute distance information. In addition, from the main CPU 14, the AF C
Camera mode (AF single mode/AP
Each information (sequence mode/other mode) is decoded through the model line. Furthermore, the main CPU
14 to AFJT] AFENA (AF
The enable) signal is a signal that controls the start and stop of AF, and the EOFAF (end-off AF) signal sent from the AP CPU 22 to the main CPU 14 is a signal that is issued at the end of AF operation and allows transition to the exposure sequence.

In addition, the bipolar circuit 15 decodes the AP motor control line signal from the AF river PU 22, and
Drives the F motor drive circuit 26. The AF motor (lens drive motor) is driven by the output of the AF motor drive circuit 26.
31 rotates, the slits 32 provided at equal intervals in the rotating member of the lens barrel rotate, and a photointerrupter 33 is formed in which a light emitting part 33a and a light receiving part 33b are arranged facing each other across the path of the slits 32. Count the slits 32. That is, the slit 32 and the photo ink printer 33
constitutes an address generation section 34, and the address signal (count signal of the slit 32) generated from the address generation section 34 is waveform-shaped and taken into the AF CPU 22.

A sub-lamp (hereinafter abbreviated as S-lamp) signal sent from the AFCPU 22 to the bipolar circuit 15 is a signal that controls the AF auxiliary light circuit 27, and turns on the S-lamp 27a when the subject is in low light (low brightness) LL.

The AF display circuit 24 connected to the AF CPU 22 includes an LED (light emitting diode) 24a that lights up to indicate focus is OK when focusing, and an LED that lights up to indicate that focusing is not possible.
It has D24b. Note that a clock oscillator 35° reset capacitor 36 is connected to this AF CPU 22.

Further, the AF CPU 22 and the A/D converter 21 exchange data via a pass line, and the direction of the data transmission is controlled by a pass line control signal. A sensor switching signal and a system clock signal are sent from the AF CPU 22 to the A/D converter 21. The A/D converter 21 is, for example, a C
A CCD drive clock signal and a COD control signal are sent to the focus sensor 20 consisting of a CD, and the focus sensor 20
Read the D output and display the read analog value on the CCD.
The output is digitally converted and sent to the AF CPU 22.

Next, a flowchart of the program operation of the microcomputer centered on the AF labbook shown in FIG. 2 of the camera having the distance information output device of the present invention will be explained. As shown in Figure 1, the AF lab book has a main CP
By activating the AF power control circuit U14, the transistor 23 is turned on and the power supply voltage V
DD is supplied, thereby beginning execution of the power-on reset routine shown in FIG.

When this power-on reset routine is started, first, the drive circuit of the AF lab book is initialized in the subroutine ``I10 initialize''. Specifically, the AP display circuit 24°, the AF motor drive circuit 26, the AF auxiliary light circuit 27, etc. are turned off, and the main CPU 1
Initialization of the serial communication line with 4 is performed.

Next, a lens reset operation is performed. Lens reset means forcibly retracting the lens to the infinity (flash) position, thereby generating a relative distance signal, that is, the focusing sensor 2.
This is an initialization operation to convert the distance measurement output signal outputted from 0 to an absolute distance signal by replacing it with the number of pulse movements from the position at infinity (OA), that is, an operation to clear the absolute distance counter.

Following the lens reset operation, the low light flag (hereinafter referred to as
(abbreviated as LL flag) is set to "L", and the LSTOP flag and LDIR flag are set to "Ho".The LSTOP flag is set to "H" when the distance ring of the lens reaches infinity.
”, becomes “L” when it hits close.Also, LDIR
The flag is a flag that sets the moving direction of the lens, and is "Ho" if it is in the infinite direction, and "Lo" if it is in the close-up direction.

Next, the AFJ11CPU22 waits for the AFENA signal from the main CPU14 to become "H".

After outputting the shooting mode set by the user to the mode line, the main CPU 14 waits for the user to operate the first stage of the release button. AFENA signal is “L”
When the state changes from o to “Ho,” the AF CPU 22
As soon as the A signal becomes "Ho", immediately read the mode line state.
FSEQ)> and execute it.

Here, the operation in the <AFSIN> mode is a one-shot AF operation, and the focus is locked after the AF operation for the subject. Furthermore, the <AFSEQ> mode is continuous AF, and in this mode, the AF operation is performed continuously as long as the first step of the release button is kept operating.

Next, we will explain the operation of each lens drive mode in Figures 4 to 8.
This will be explained using the flowchart shown in the figure.

First, if the <AFS IN> mode is selected,
The <AFSIN> routine shown in FIG. 4 is executed, and <
AFSIN2> subroutine is called. however,
The second stage of the release button is activated by A.
This is when the F operation is completed, a focused state is obtained, and the exposure sequence is started. In <AFSIN2>, as will be described later, CCD integration of the focus sensor 20, calculation of 1l) J distance output, lens driving, etc. are performed. and,
Focusing is the result of the AF operation of this <AFSIN2>.

Out of focus is displayed by monitoring the AF status flag after the <AFSIN2> operation. The AF status flags are the low contrast flag (a flag set to 1° when the subject is low contrast, hereinafter abbreviated as the LC flag), and the movement flag (when the subject is moving).
A flag set to "1" (hereinafter abbreviated as M flag) and a closest approach flag (a flag set to "1" when an attempt is made to extend the lens beyond the closest distance, hereinafter abbreviated as N flag), It has an over flag (for example, a flag that is set to "1" when the lens is not in focus even after driving the lens 8 times, hereinafter abbreviated as oV flag), and when any of these flags is O, Focusing is possible, and if any of the above flags is set, focusing is not possible.As a result of monitoring the AF status flag, if the AF status flag is 0, the AF display will indicate that the focus is OK. LEI)!4a of the circuit 24, and if the AF status flag is not 0, the LED 24b indicates that the focus is not possible.If the AF status flag is 0, the LED 24b indicates that the focus is not possible.If the AF status flag is 0, the LED 24b indicates that the focus is not possible. The CPU 14 enters a state where it waits for the second operation of the release button, that is, the start of the exposure sequence.In other words, once focusing is completed, subsequent lens operation is prohibited even if the AFENA signal is active. The focus OK display LED 24a remains lit and the focus is locked.AF from the main CPU 14
When the ENA signal becomes "L" level (inactive), the AF of the power-on reset flow shown in Figure 3
Return to ENA signal test.

While operating in the above <AFS IN> mode, <AFSIN2
The program operation of the subroutine > is performed as shown in FIG.

First, the LL flag used as a flag for controlling the AF operation is cleared, and then the counter AFCNT for counting the number of AF operations is cleared.

Next, 1 is added to AFCNT, and the AF operation starts. First, all AF status flags are cleared and an autofocus <AF> routine for distance measurement is called. In this <AF> routine, the distance to the subject is detected and the AF calculation output value (ERR
OR) and set the direction in which the lens should be moved in the DIR flag (“H” if it is in the infinite direction, “L” if it is in the close direction). However, if the subject has low brightness during all distance, the LL flag is set to "H" and the distance is measured while lighting the S lamp 27a.

Also, if the subject has low contrast, set the LC flag to “
Make it Ho.

Next, a lens read routine <LENSRD> is called, and data for each lens contained in the lens data circuit 18 is read. Of the loaded lens data,
<ERROR
TH> subroutine determines the AF accuracy threshold (ETh). After this, the LC flag is determined.

If the subject is not of low contrast, the LC flag remains cleared, so if the LC flag is "L", the pulse <PULSE> routine is called and the amount of lens drive is calculated.In other words, this <PULSE> The rule of
In order to convert the AP (distance measurement) calculation output value obtained by the upper focus <AF> operation into the amount of distance movement for each interchangeable lens, information such as the magnification coefficient is read from the lens data circuit 18. , the number of pulses (address signals) corresponding to the amount of movement to the in-focus point is calculated from the read magnification coefficient and the AF calculation output value.

After this, the AF calculation output value (ERROR) and the A
The AF calculation output value (ERROR) is compared with the AF accuracy threshold (ETh).
Th), it is judged to be in focus <CALDIST>
Proceed to. Otherwise, proceed to check AFCNT. If the value of AFCNT is 8, it means that 8 AF operations have already been performed, and assuming that it will not be possible to focus even if AF operations continue, the Ov flag is set to "H".
Proceed to CALDIST>. If the value of AFCNT is not 8, then it is checked whether it is 1 or not. If it is 1,
Proceed to check the LSTOP flag. If the LSTOP flag is "H", the lens has already touched the end, so compare the LDIRDIR flag, which indicates the direction in which it has touched, with the DIR flag, which indicates the direction in which it is moving, and make sure that they match. If so, proceed to check the DIR flag. Here, if the DIR flag is "H", the moving direction of the lens is pointing further to the infinity side than the end of the lens on the infinity side, so in this case, it is considered that the focus is <C
Proceed to ALD I ST>. On the other hand, the DIR flag is “L”.
”, the subject is closer than the close end of the lens. In this case, it is assumed that the object is out of focus, and the N flag is set to “H” and the process proceeds to <CALD I ST>. If not, clear the LSTOP flag, and then set the AF calculation output value (ERROR) to the previous ER.
RORF? tt delivery register (LERROR), and the DIR flag indicating the moving direction is also changed to the LDIRDIR flag indicating the direction in which the end of the lens is applied.

If you go back and the LSTOP flag is not “H”, also set it to “L”.
ERROR, proceed to LDIRDIR flag. continue,
Call the <MDRIVAF> routine and press <PULSE
The lens is moved in the direction indicated by the DIR flag by the number of pulses calculated in the routine >. If the lens comes into contact with the end of the lens while moving, the lens drive motor 31
Stops power supply to , sets the LSTOP flag to "H", and returns. Also, while the <MDRI VAF> routine is being executed, the AFENA signal is checked at any time.

Therefore, if the user stops operating the first stage of the release button while the lens is being driven, the main C
Since the PU 14 changes the AFENA signal from "H" to "Lo," the AFCPU 22 immediately stops lens driving and returns when detecting "L" of the AFENA signal.

After returning from the <MDRrVAF> routine, first check the AFENA signal, and if the AFENA signal is “
If it is "L", proceed to <CALDIST>. If it is "H", proceed to ■ to start the second AF operation.

The AF operation from the second time onwards is the same as the first time, but the AFC
In determining whether NT is 1, AFCNT≠1
Therefore, it is checked whether the AF calculation output value (ERROR) is four times or more the AF accuracy threshold (ETh). If it is less than 4 times, proceed to check the LSTOP flag as in the first time. If it is 4 times or more, - Next, compare the current AF calculation output value (ERROR) and the previous AF calculation output value (LERROR), and find that ERROR≧LERR.
If it is not OR, proceed to check LSTOP like the first time. If ERROR≧LERROR holds, the M flag is set to “H” and the process proceeds to <CALDI ST>. This is because the AF calculation output value becomes larger than the previous value in a large range of defocus amount, which is more than 4 times the AP accuracy threshold, because the subject is moving at high speed, and the AF operation is no longer required. This is because it was decided that there was no point in continuing.

Next, a case where the LC flag is set to "H" in the <AF> routine because the subject has low contrast will be described. <LENSRD>.

The <ERRORTH> routine is executed in the same way, but the LC
In flag determination, if the LC flag is “H”, <P
ANFOCUS> routine is called. <PANFO
CUS> routine is a subroutine for moving the photographing lens to the common focal position determined by the focal length of the photographing lens, and will be explained using FIG. 6.

First, from the focal length information of the photographic lens read from the lens data circuit 18 in the <LENSRD> routine, the normal focal position or the position where the in-focus range is the widest at that focal length (hereinafter these positions will be referred to as the pan focus position) is determined. ) is obtained from the conversion table in the internal ROM of the AFCPU 22. Now, for example, the pan focus position is
Suppose that it is m. Next, when the photographic lens is moved to the position Xm, the absolute distance counter is calculated backwards. Next, the value of the absolute distance counter at the current position where the photographing lens is stopped is compared with the value of the absolute distance counter at the pan focus position to calculate the target number of movement pulses. Next, the MDRI VAF> routine is called to set the direction of movement of the lens, the photographing lens is moved to the pan focus position, and the process returns.

Returning to Fig. 5, after returning from the <PANFOCUS> routine, clear the AF status flag and <C
Proceed to ALDIST>. This is to create a pseudo focus at the pan focus position. Therefore, <CALD
When the routine of IST> is ended and the routine of AFS IN> is returned to, an in-focus display is made.

Here, the <CALDIST> routine is a subroutine that calculates the distance to the subject from the value of the absolute distance counter and the absolute distance coefficients a and b in the lens circuit 18, and sends it to the main CPU 14.

The <AFSIN2> routine ends here, and the <AFSIN2> routine ends.
Return to the IN> routine.

Next, in the flow shown in FIG.
> mode is selected, the <AF mode shown in Fig. 7 is selected.
SEQ> routine is called. This <AFSEQ
> Then, when the first step of the release button is activated,
After this, the first AP operation until the EOFAF signal becomes active is exactly the same as in the case of <AFSIN>. In other words, <AFS IN> is also <A
FSEQ> also performs the operation of <AFSIN2>, and when focusing is not possible, the lens is actively driven abnormally and the user is notified.

By the way, in <AFS IN2>, as mentioned above,
In low light (low brightness), the S lamp 27a is used to assist distance measurement for AF operation, but <
If the S lamp 27a is similarly used when the AF operation is continued in the <AFSEQ> mode, the S lamp 27a will continuously light up and emit light during the CCD integration operation in the <AF> mode. This results in an increase in current consumption and a decrease in efficiency due to heat generated by the S lamp 27a, and the lens continues to be driven abnormally when focusing is not possible, giving the user a sense of anxiety.

Therefore, in <AFSEQ>, after the AF operation is executed once and the EOFAF signal is set, the AFENA signal is determined, and if the signal is active, the operation of the first stage of the release button is continued. <AFS>
The routine EQ2> is called. If the AFENA signal is inactive, the process returns assuming that the first stage of the release button has been turned off, and the second stage of the release button has been turned on. As described later, in <AFSEQ2>, CCD integration of the focus sensor 20, AF calculation, lens drive, etc. are performed, but active focus failure display due to lens abnormal drive and S for Δp1 distance are performed.
The lamp 27a is also not lit. And this <A
As a result of the operation of FSEQ2>, the AF status flag is determined, and if the flag is 0, an indication that the focus is OK is displayed, and if it is not 0, an indication that the focus is not possible is displayed. After the in-focus OK signal is displayed, the EOFAF signal is generated, and it becomes possible to start the exposure sequence by operating the second step of the release button. After this EOFAF signal is issued,
Or, after the inability to focus is displayed, try AFE again.
Since the NA signal test begins, as long as the first stage of the release button is kept on, the AF operation centered on <AFSEQ2> will be performed continuously. And AFE
When the NA signal becomes non-active, the process returns to the power-on reset flow shown in FIG.

[2] In the <AFSEQ> mode flowchart of FIG. 7, the program operation of the <AFSEQ2> subroutine is performed as shown in FIG.

First, in AFSEQ mode, the EOFAF signal is set to “L” once.
”, the S lamp 27 will be used for subsequent distance measurement operations.
In order to prevent a from lighting up, the use of the S lamp 27a is prohibited at the beginning of the <AFSEQ2> routine, and then the A
Clear the F status flag. Thereafter, in the <AF> routine, an AF calculation output value (ERROR) is calculated, and the lens movement direction is set in the DIR flag. However, as described above, even if the subject is of low brightness, the S lamp 27a does not light up.

Next, in the routine <LENSRD>, data for each lens contained in the lens data path 18 is read, and then in the routine <ERROR>, the AF accuracy threshold <ET h) is determined.

Next, double the AF accuracy threshold (ETh). In <AFSEQ> mode, this is already <A
This is to prevent the photographic lens from moving and becoming prohibited from releasing if the subject moves slightly within a range of about twice the AF accuracy threshold (ETh), since focusing is performed using the routine FSIN2>.

Next, the LC flag is determined and the LC flag is “H”.
If distance measurement is not possible due to low contrast, the process proceeds to <CALD IST> without driving the lens. L
If the C flag is "L", the check of the LSTOP flag progresses, and if the LSTOP flag is "H", that is, the lens is applied to the infinity side or the close side, the LDIRDIR flag indicating the direction of the application is moved from there. Compare the DIR flags that indicate the direction that should be taken, and if they do not match, <
Proceed to routine PULSE>. Conversely, if they match, the process proceeds to checking the DIR flag. Here, if the DIR flag is "Ho", the moving direction of the lens is pointing further toward infinity than the end of the lens on the infinity side, so in this case, it is considered to be in focus and the process proceeds to <CALDIST>.On the other hand,
If the DIR flag is "Lo", it means that the subject is closer than the close end of the lens, and in this case it is assumed that the focus is out of focus, and the N flag is set to "H" and <CALD
Proceed to IST>.

Returning to the previous step, if the LSTOP flag is not "Ho," in the <PULSE> routine, after calculating the target movement pulse number, the AF accuracy threshold (ETh), which is doubled by the AF calculation output value (ERROR) ), and if ERROR≧ETh does not hold, it is determined that the focus is in the in-focus area, executes the routine <CALD I ST), and returns.If ERROR≧ETh holds, the EOFAF signal is set to “H”. ” and main C
Notify the PU 14 that the focus is out of the in-focus area. Next, the focus OK display LED 24a and the focus failure display LED 24b are turned off, and the contents of the DIR flag indicating the lens movement direction are changed to the LDI flag indicating the previous movement direction.
Transfer to R flag.

Next, call the <MDRIVAF> routine and execute <P
DIR for the number of pulses calculated by the routine ULSE>
Move the lens in the direction indicated by the flag. <MDR
After returning from the IVAF> routine, first perform AFE.
Check the NA signal, and if it is “Ho”, return to ■ and repeat the same process.

If not “H”, execute <CALD I ST> and return.

Next, a method for calculating the absolute distance will be explained.

The absolute distance counter is set with the number of pulses (address signals) that correspond to the amount of movement of the lens from the infinity (oo) position, so if the amount of lens movement can be approximated as a linear function, the absolute distance can be obtained by calculation. . Now, if the lens movement ff1 (absolute distance counter) is Y and the absolute distance is X, the relationship between the two can be approximated as (1).

Y-b/ (X-a)...-=...(1) Here a
, b is an absolute distance coefficient specific to the lens.

Therefore, by determining a and b for each lens and storing them as information in the lens data circuit 18, the absolute distance can be determined from the amount of lens movement.

In the embodiments described so far, the focal length information is read from the lens data circuit 18 and the pan focus position is determined from the conversion table stored in the internal ROM of the AFCPU 22. The same effect can be achieved by using a method of calculating the position of the pants as shown in FIG.

In addition, when the release is enabled as a pseudo-focus at the pan-focus position, the range of focus will be wider if the exposure aperture is narrowed down as much as possible, so the shutter speed should be adjusted manually only during the pseudo-focus at the pan-focus position. It is also possible to control the aperture to be as slow as possible so that no blurring occurs and to narrow the aperture as much as possible.

[Effects of the Invention] As described above, according to the present invention, when the subject has low contrast and the 4-1 distance is not possible, a different common focus position is calculated for each photographing lens, and the photographing lens is moved to that position. Since the camera is designed to release the camera at that position, it can be suitably used in an AP camera with interchangeable lenses, and it is possible to avoid missing a photographic opportunity and obtain a photograph in focus.

[Brief explanation of drawings]

Figure 1 is a professional diagram of an electric circuit that mainly supplies power to an interchangeable lens AF camera to which the present invention is applied, and Figure 2 is a diagram of the exchange of signals centered around the AF block in Figure 1 above. The block system diagrams shown in FIGS. 3 to 8 are flowcharts showing program operations centered on the AF river PU shown in FIG. 2 above.

Claims (1)

[Claims] In an interchangeable lens camera having means for calculating absolute distance information and moving a photographing lens to a designated position using the absolute distance information, when the subject has low contrast, the focal point of the photographing lens is adjusted. a means for reading the distance; a means for calculating the normal focal position of the photographing lens or a position where the range of focus is widest from the focal length information read by the reading means; and a means for moving the photographing lens to the position calculated by the calculation means. A distance information output device comprising: means for moving the lens; and means for enabling release after the photographing lens has moved to the calculated position.