JPS6310136A - Distance information output device foe lens interchangeable type camera - Google Patents

Abstract

PURPOSE:To raise the probability that a distance can be measured, by utilizing absolute distance information and moving a photographic lens to the effective position of an auxiliary illuminating light, in case of executing a distance measurement by using the auxiliary illuminating light. CONSTITUTION:When a low contrast (LC) flag is set to H due to the low contrast of an object to be photographed, and a position having the highest possibility for measuring a distance when an auxiliary illuminating light S lamp 27a for an AF is used is assumed to be the position of Xm as an absolute position, the value of an absolute distance counter in the position of Xm is counted back by using absolute distance coefficients (a), (b) which are read. Subsequently, this value is compared with the value of the absolute distance counter in a position where the present photographic lens is stopping, and the number of target moving pulses from the present position and the moving direction of the lens are calculate. Next, the photographic lens is moved to the most effective position of the auxiliary illuminating light and the AF operation of the second time is started.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a distance information output device for an interchangeable lens camera;
Specifically, the present invention relates to an all-sizing method using low-intensity illumination in a distance information output device that obtains absolute distance information for autofocus (hereinafter referred to as AF) driving and the like.

[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. For example, relative distance information can be output using only comb-teeth electrodes, so
Although it has the advantage of simplifying the configuration as a distance information output device for an interchangeable lens, it is more convenient to use absolute distance information for a single-lens reflex camera as a system camera.

Therefore, the applicant first performed a simple C calculation on the count output according to the relative distance from the interchangeable lens barrel, so that the absolute distance could be obtained with high accuracy using a configuration suitable for a system camera. The present invention provides a distance information output device for an interchangeable lens camera (Japanese Patent Application No. 60-275251).

By the way, in an autofocus camera that has a passive distance measuring device that detects the distance to the subject using subject light information from reflected light from the subject, it is impossible to detect the distance unless the subject has a predetermined level of brightness. become.

For this reason, when the subject brightness falls below the above-mentioned predetermined level, a technical means that automatically irradiates auxiliary illumination light to raise the subject brightness above the above-mentioned predetermined level has been proposed in the prior art.
It is known from Publication No. 8-7130 and the like.

[Problems to be Solved by the Invention] However, even if the brightness of the subject is improved by irradiation with auxiliary illumination light, the photographing lens during distance measurement may be placed at a position where the amount of defocus is large, such as at the extreme far end position or at the closest point. When the lens is at the end position, the contrast of the image plane decreases, resulting in a problem that distance measurement becomes impossible despite the use of auxiliary illumination light.

Therefore, an object of the present invention is to provide a distance information output device for an interchangeable lens camera that skillfully utilizes absolute distance information to increase the probability of achieving an 11-1 distance when using auxiliary illumination light. be.

[Means and effects for solving the problem] In the present invention, when ill distance is not possible despite using auxiliary illumination light, the amount of lens movement is calculated from the absolute distance coefficient and absolute distance specific to the lens. Then, from this amount of movement, the amount of movement of the photographic lens where the auxiliary illumination light is most effective is calculated backwards, and based on this, the photographic lens is moved to the position where the auxiliary illumination light is most effective, and the auxiliary illumination light is used again at that position. and measure the distance.

[Example] Hereinafter, an example in which the present invention is applied to an interchangeable lens camera having an AF function 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 DC/D when the power switch 12 is closed.
The voltage is boosted by the C converter 13, and the line g fI
Between line No. 1 and No. 1, the main CPU 14 and
Bipolar ■Circuit 15. Bipolar 1 circuit 16, strobe control circuit 17. A lens data circuit 18 and a data pack circuit 19 are connected, and power supply control of the bipolar circuit 15 is performed by a signal from the power control circuit of the main CPU, and power supply control of the Pipo 91 circuit 16 to data pack circuit 19 is performed. is bipolar■circuit 1
This is done by the power control signal from 5.

Focus sensor 20. A/D converter 21. AF CPU
The AP lab book consisting of 22 is a power supply control transistor 2
The power supply control for this AF block is controlled by the main CPU 14.
This is done by controlling the transistor 23 on and off using a signal from the AF power control circuit.

The AF CPU 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 status. The main CPU 14 is a circuit for controlling the entire sequence of the camera such as winding, rewinding, and exposure sequences, and is connected to a display circuit 25 for displaying other than self-focus display. The bipolar circuit 15 is a circuit that includes various drivers necessary for the camera sequence, such as winding and rewind motor control, lens drive, and shutter control, and the AF motor drive circuit 26 and A
The F auxiliary optical circuit 27 and the like are connected. The bipolar 1 circuit 16 is a circuit mainly responsible for photometry, and has a photometry element 28. The strobe control circuit 17 is for controlling the light emission of a built-in or 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 the lens data circuit 18, the data necessary for AF includes a lens magnification coefficient (zoom coefficient), a macro identification signal, and absolute distance coefficients a and 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 VDo, and when the power supply 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, and Focus sensor 20° A/D converter 21 and A
The power supply to the AF labbook consisting of the F CPU 22 is cut off. Power is supplied to the main CPU 14 even if the voltage is below the specified voltage.

Figure 2 is a system diagram showing the transmission and reception of signals centered on the AF labbook, and shows the AFJII CPU 22 and main CPU 14.
sends and receives data through a serial communication line, and the direction of the communication is controlled by a serial control line. The contents of this communication include unique lens data within the lens data circuit 18,
This is absolute distance information. Also, from the main CPU 14
Information on camera modes (AF single mode/AF sequence mode/other modes) is decoded by the F 11 CPU 22 through the model line. moreover,
AFENA from main CPU 14 to AF CPU 22
The (AF enable) signal is a signal that controls the start and stop of AF, and is a signal that controls the start and stop of AF.
An EOFAF (end-off AF) signal sent from 22 to the main CPU 14 is a signal that is issued at the end of the AF operation and allows transition to the exposure sequence.

In addition, the bipolar circuit 15 decodes the AF motor control line signal from the AF CPU 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 photo ink printer is formed in which a light emitting part 33a and a light receiving part 33b are arranged opposite to each other with the passage of the slits 32 in between. 33 counts the slit 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.

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

The AF display circuit 24 connected to the AP CPU 22 includes an LED (light emitting diode) 24a that lights up to indicate focus OK when focusing, and an LED (light emitting diode) to indicate focus failure that lights up when focusing is not possible.
D24 b. In addition, this AF CPU 22
Clock oscillator 35° Reset capacitor 36
is connected.

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 CCD 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 program 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 main C
By activating the AF I power control circuit of the PU 14, the transistor 23 is turned on and the power supply voltage vDD is supplied, thereby starting 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 a subroutine <I10 initialization>. 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 (oo), that is, an operation to clear the absolute distance counter.

Following the lens reset operation, the low light flag (hereinafter referred to as
The LL flag (abbreviated as LL flag) is set to "L", and the LSTOP flag and LDIR flag are set to mH'. The LSTOP flag is the “H” flag when the lens range ring reaches infinity.
o, it becomes 'L° when it hits close. Also, LDIR
The flag is a flag that sets the moving direction of the lens, and is "H" if it is in the infinite direction, and 0L if it is in the close-up direction.

Next, the AF CPυ22 receives the A from the main CPU14.
Wait until the FENA signal becomes "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 it becomes “Ho”, AFJI CPU 22
As soon as the FENA signal becomes "H", read the mode line state. Depending on the status of this mode, <AFS IN> and <AFS IN>
Hereinafter, one of the subroutines (AFSEQ)> is selected and executed.

Here, the operation in the <AFS IN> 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 AP, and in this mode, the AF operation is performed continuously as long as the first stage 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, when the <AFSIN> mode is selected, the <AFSIN> routine shown in FIG.
FSIN2> subroutine is called. However, the second operation of the release button is only supported by AF.
This is when the operation is completed, a focused state is obtained, and the exposure sequence is started. In <AFSIN2>, as described later, the CCD integration of the focus sensor 20, ? IN distance output calculation, lens driving, etc. are performed. Then, the focus is the result of the AF operation of this <AFSIN2>.

Out of focus is displayed by monitoring the AP 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 O, the AP display will indicate that focusing is OK. This is done by the LED 24a 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 focus is in focus, an EOFAF signal is issued, the AF operation is completed, and the main CPU 14 The state waits for the second operation of the release button, that is, the start of the exposure sequence.In other words, once focusing is completed, further lens operation is prohibited even if the AFENA signal is active, and the focus is not activated. The 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 is activated.
Return to ENA signal test.

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

First, the PAN flag is a flag for controlling the AF operation.

The NF flag (the PAN flag and the NF flag will be described later) is cleared.The LL flag is cleared, and then the counter AFCNT for counting the number of AF operations is cleared.

Next, 1 is added to 1 and AFCNT, and the -th AF operation is started. 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 (ERROR
), and also calculate the direction in which the lens should be moved by DI.
Set the R flag (“Ho” if the direction is infinite, “Lo” if the direction is close). However, if the subject has low brightness during distance measurement, the LL flag is set to "H" and the distance is 11-1 while lighting the S lamp 27a.

Also, if the subject has low contrast, set the LC flag to '
Set to “H”.

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 AP 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 distance movement amount for each interchangeable lens, information such as the magnification coefficient is sent 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 based on 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).
If it is less than Th), it is judged to be in focus and <CALDI ST
Go to >. Otherwise, proceed to check AFCNT. If the value of AFCNT is 8, it means that 8 AF operations have already been performed, and considering that it will not be possible to focus even if AF operations continue, the OV flag is set to "H" and <CALDI Proceed to ST>. If the value of AFCNT is not 8, then check whether it is 1. If it is 1, proceed to check the LSTOP flag. If the LSTOP flag is "Ho", the lens has already been terminated. Since it is directed to the LDIR flag indicating the direction of the direction,
It compares it with the DIR flag indicating the direction in which it is about to move, and if the two match, it proceeds to check the DIR flag. Here, if the DIR flag is "H", the moving direction of the lens is pointing further toward infinity than the infinity end of the lens, so in this case, consider it to be in focus and proceed to <CALD I ST>. move on. On the other hand, if the DIR flag is L°, the subject is closer than the close end of the lens, and in this case it is considered out of focus.
Set the flag to “Ho” and proceed to <CALD I ST>.

If the two do not match, the LSTOP flag is cleared, and then the AF calculation output value (ERROR) is set to the previous ERROR.
It is transferred to the RROR storage register (LERROR), and the DIR flag indicating the direction of movement is also transferred to the LDIR flag indicating the direction in which the end of the lens is applied.

Go back and set the LSTOP flag to “L” even if it is not “Ho”.
Proceed to set ERROR and LDIR flags. 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
The program stops supplying power to the program, sets the LSTOP flag to "Ho", and returns. Also, while the <MDRIVAF> 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 CPU 14 changes the AFENA signal from "H" to "L", and the AFCPU 22 changes the AFENA signal from "H" to "L". “Lo
When it detects this, it immediately stops driving the lens and returns.

After returning from the <MDRIVAF> routine, first check the AFENA signal, and confirm that the AFENA signal is
If “L”, proceed to <CALDI ST>. If it is “H”, proceed to ■ and start the second AF operation.

The AF operation from the second time onwards is the same as the first time, but the AFC
AFCNT#1 in determining whether NT is 1 or not.
Note: Check 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, then this A
Compare the F calculation output value (ERROR) and the previous AF calculation output value (LERROR), and find that ERROR≧LERRO
If it is not R, 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 AF accuracy threshold, because the subject is moving at high speed, and the AF operation is no longer required. Even if you continue j)! (Because I decided it was no good.

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”, LL
Proceed to flag determination. Now, the subject is not in low brightness, but in LL
If the flag is "L", proceed to LENSNF>, and if the subject has low brightness and the LL flag is "H" (when using the auxiliary illumination light S lamp 27a), proceed to PAN flag determination. move on. The PAN flag is a control flag that is cleared at the beginning of the <AFSIN2> routine and set to “H” immediately before the <5POS lTl0N> routine.
is set to If the PAN flag is not ``H'', then set the PAN flag to ``H'', then <5POS lT
10N> routine is called.

The routine <5PO3lTl0N> will be explained using FIG. 6.

The routine <5POS lTl0N> is a subroutine for moving the photographing lens to a position where it is most likely to achieve all distance when using the AFJIJ auxiliary illumination light S lamp 27a. Now, assume that the position is an absolute distance of Xm. First of all, using the absolute distance coefficients a and b read in the <LENSRD> routine,
The value of the absolute distance counter at the position m is calculated backwards. Next, this value is compared with the value of the absolute distance counter at the current position where the photographing lens is stopped, and the target movement pulse number and lens movement direction from the current position are calculated.

Next, in the <MDRIVAF> routine, the photographing lens is moved to the auxiliary illumination light amount effective position, and the process returns.

After returning, proceed to ■ to start the second AF operation.

Even at the Xm position, if the subject has low contrast, check the LL flag and PAN as in the first case.
The process proceeds to check the flag, but since the PAN flag has already been set to "H" at this time, the process proceeds to check the NF flag.

The NF flag is a control flag for executing the <LENSNF> routine only once, and is cleared at the beginning of the <AFSIN2> routine and set immediately before the <LENSNF> routine. If the NF flag is not “Ho”, then set the NF flag to “H”, then <LENSN
Call the routine F>. In the <LENSNF> routine, the lens is first extended to the closest position, then retracted to the infinity (ao) position, and the user is actively notified of the inability to focus by moving the lens significantly. However, while the lens is moving, the low contrast of the object is always determined, and if the object no longer has low contrast, the movement is immediately stopped and the process returns. Furthermore, the AFENA signal changes from “H” to “L”
If it changes to , it also stops moving and returns. Also,
When the lens reaches the infinite end and stops, the absolute distance counter (a counter that saves the number of moving address signals from the infinite (oo) position of the lens distance ring) is reset, and the LSTOP flag is set to "H".

Set to .

Next to the <LENSNF> routine, the AFENA signal is checked, and if it is not “H”, <CALD
Proceed to IST>. If it is "H", the state returns to ■ and normal AF operation is started. However, at this time, if the subject has low contrast again, check the LL flag,
The process passes through the PAN flag check and proceeds to the NF flag check, but since the NF flag has already been set to "H", the <LENSNF> routine is not executed again (the process proceeds to the <CALDIST> routine).

The <CALDI ST> routine calculates the absolute distance to the subject from the value of the absolute distance counter for counting the number of driving pulses from the infinite position of the lens distance ring and the absolute distance coefficient in the lens circuit 18. In the routine to
The determined absolute distance is sent 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.
The routine SEQ> is called. This <AFS
In EQ>, when the first operation of the release button is performed, the first AF operation after this until the EOFAF signal becomes active is exactly the same as in the case of <AFS IN>. do. In other words, <AFS IN>
For both <AFSEQ> and <AFSIN2>, the operation of <AFSIN2> is performed, 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,
During low light (low brightness If), the S lamp 27a is used to assist distance measurement for AF operation.
If you use the S lamp 27a in the same way when performing continuous AF operation in the <AFSEQ> mode, the S
The lamp 27a will be lit and emit light continuously during the CCD integration operation in <AF>, which will increase current consumption and reduce efficiency due to heat generation of the S lamp 27a. Abnormal driving occurs continuously, giving the user a sense of anxiety.

Therefore, in <AFSEQ>, after one AF operation is performed 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, it is assumed that the first stage of the four-nose button is turned off, and the second stage of the button is turned on, and the process returns. In <AFSEQ2>, as will be described later, CCD integration of the focus sensor 20, AF calculation, lens drive, etc. are performed, but the S lamp 27a is used to actively display the inability to focus due to abnormal lens drive and to measure the distance. is not lit either. And this <AF
As a result of the operation SEQ2>, the AF status flag is determined, and if the flag is 0, a display indicating that the focus is OK is displayed, and if it is not 0, a display indicating 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 emitted or after the display indicating that the focus is not possible, turn the AFEN again.
Since a test of the A signal is started, 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.

In the flowchart of the <AFSEQ> mode shown in FIG. f87 above, 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.
If set to o, 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. After that, <AF>
Calculate the AF calculation output value (ERROR) with the routine
Set the lens movement direction to 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 circuit 18 is read, and then in the routine <ERROR>, the AF accuracy threshold (ETh) is determined.

Next, double the AF accuracy threshold (ETh). In <AFSEQ> mode, this is already <A
Since focusing is performed using the FSIN2> routine, this is to prevent the photographic lens from moving and causing a release prohibition condition if the subject moves slightly within a range that is approximately twice the AF accuracy threshold (ETh). .

Next, the LC flag is determined and the LC flag is “H”.
If the distance measurement is not possible due to low contrast, the process proceeds to <CALDIST> without driving the lens. L
If the C flag is “L”, the LSTOP flag is checked, and if the LSTOP flag is “H”, that is, the lens is applied to the infinity side or the close side, the LDIR flag indicating the direction in which it was applied, and the LDIR flag from now on. Compare the DIR flags indicating the direction to move, 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 "H", this means that 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 lens is in focus and the process proceeds to <CALDI ST>. On the other hand, if the DIR flag is "L", it means that the subject is closer than the close end of the lens, and in this case, it is assumed that the subject 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 "H", in the <PULSE> routine, after calculating the target movement pulse number, the AF calculation output value (ERROR) is multiplied by the AF accuracy threshold ( ETh), and if ERROR≧ETh does not hold, it is determined that the focus is in the in-focus range, executes the routine <CALD I ST), and returns. ERROR'≧ETH
If this is true, the EOFAF signal is set to “Ho” to notify the main CPU 14 that the focus is out of focus range.Next, set the focus OK left display ED24a and the focus failure display LED24b to 0FFL The content of the DIR flag indicating the movement direction is changed to the LDI indicating the previous movement direction.
Transfer to R flag.

Next, call the <MDRI VAF> routine and execute <
DI for the number of pulses calculated by the PULSE> routine.
Move the lens in the direction indicated by the R flag. <MD
After returning from the RIVAF> routine, first
Check the ENA signal, and if it is "H", return to step 3 and repeat the same process.

If it is 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 to the number of pulses (address signal) that corresponds to the amount of movement of the lens from the infinity (■) 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 amount (absolute distance counter) is Y and the absolute distance is X, then
The relationship between the two can be approximated as shown in (1).

Y/(X-a) (1) Here, a and b are absolute distance coefficients 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. Therefore,
If it is assumed that the auxiliary illumination light is most effective when the photographic lens is at the position Xm, then the movement ffl (Y) of the photographic lens to the target position can be calculated backwards from the above equation (1).

In addition, in the embodiments described so far, when the subject is of low brightness, the auxiliary illumination light is irradiated once at the position where the photographing lens is currently stopped, and the distance measurement operation is performed. If the distance cannot be determined, the photographic lens is moved to a position where the auxiliary illumination light is most effective. However, if it is certain that 1111 distance cannot be achieved in the first all distance operation, for example, if the photographic lens is located at a position extremely far from the effective position of the auxiliary illumination light, the position where the photographic lens is currently stopped Of course, the photographing lens may be directly moved to the position where the auxiliary illumination light is most effective without performing the All distance operation using the auxiliary illumination light.

[Effects of the Invention] As described above, according to the present invention, when performing distance measurement using auxiliary illumination light, absolute distance information is used to move the photographing lens to the effective position of the auxiliary illumination light. Therefore, it is possible to provide a distance measurement information output device for an interchangeable lens camera that can increase the probability that distance measurement is possible and eliminate the problems that conventional devices of this type have.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an electric circuit mainly for power supply of a camera system to which the present invention is applied, and Fig. 2 is a block diagram showing signal exchange centered on the AF lab book in Fig. 1 above. , FIGS. 3 to 8 are flowcharts showing program operations centered on the AF 711 CPU shown in FIG. 2 above. 27...AP auxiliary optical circuit 27a...
...Sub-lamp (auxiliary illumination light) A3 Decoy procedure amendment (voluntary) 3. Relationship with the case of the person making the amendment Patent applicant 4, agent 5, subject of amendment 4 (name of the invention in the specification, claims in the specification, details of the invention) Explanation column" 6, Contents of amendment (1) Name of the invention as stated in the third line of page 1 of the specification "Interchangeable lens type" (2) "Claims" as stated in page 1 of the specification
amended as shown in the attached sheet. (3) The sentences from "This invention is carried out" at the beginning of the third line from the bottom of page 1 to "conducted." at the end of page 4, line 10 of the specification shall be replaced with the following sentences. ``This invention relates to improving the distance measurement performance for low-brightness objects in an automatic focusing camera, specifically an automatic focusing camera with interchangeable lenses. Autofocus cameras that have a passive distance measuring device that uses a passive distance measuring device to detect the distance to the subject cannot detect the distance unless the subject has a brightness level above a predetermined level.For this reason, conventional autofocus cameras Then, when the subject brightness falls below the above-mentioned predetermined level, a technical means is presented in Japanese Patent Application Laid-Open No. 7130/1983, etc., which automatically irradiates auxiliary illumination light to raise the subject brightness above the above-mentioned predetermined level. , and has been commercialized. [Problems to be solved by the invention] However, even if the subject brightness is improved by irradiation with auxiliary illumination light, the position of the focus adjustment lens during distance measurement causes a large amount of defocus. For example, at the infinity end position or the closest end position, the contrast of the image plane decreases,
Despite using auxiliary illumination light, there was a problem in which distance measurement was not possible. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an automatic focusing camera that increases the probability that distance measurement is possible when using auxiliary illumination light and can quickly complete an automatic focusing operation. [Means and effects for solving the problem] In the present invention, the shift amount detection operation is performed by irradiating the low-luminance object with auxiliary illumination light. If this is not possible, the photographing lens is moved to a position where the auxiliary illumination light is effective, and the shift amount detection operation is performed again at that position using the auxiliary illumination light. (4) "is" stated at the beginning of line 8 on page 31 of the specification.
Add the following line to the next line. "By the way, in the above embodiment, in order to move the photographing lens to a predetermined position, the absolute distance is calculated and the lens is moved to the predetermined position based on the absolute distance information. However, there is an even simpler method. It is also possible to place the photographic lens against the closest end or the infinite end and then drive the photographic lens by a predetermined amount using that position as a reference point.'' (5) Page 31 of the specification, beginning of line 10, ``The above Replace the text from ``as stated'' to ``may.'' at the end of the fifth line from the bottom of the same page with the following sentences. ``As described in the above embodiments, according to the present invention, when performing the misalignment detection operation using auxiliary illumination light, the photographing lens is moved to the effective position of the auxiliary illumination light. The possibility of automatic focus adjustment for low-brightness objects can be greatly improved, and the defects that conventional cameras of this type have can be eliminated.'' (Attachment) ``2. An automatic device characterized by comprising: a range means; an output means; a control means; and a means for re-irradiating the auxiliary illumination light at a position to which the photographing lens has moved to perform the shift amount detection operation. Focus adjustment camera.”

Claims (1)

[Claims] In an interchangeable lens camera having means for calculating absolute distance information and moving the photographing lens to a specified position using the absolute distance information, automatic assistance is provided when the subject has low brightness. means for performing a distance measurement operation by irradiating illumination light; means for moving a photographing lens to a predetermined distance position when distance measurement is not possible despite irradiation of the auxiliary illumination light; At the position where the photographic lens has moved, turn on the auxiliary illumination light again.
A distance information output device comprising means for performing a distance measurement operation by irradiating light.