JPH01287611A - Focus detector equipped with auxiliary lighting device - Google Patents

Abstract

PURPOSE:To perform sufficient focus detection with the title focus detector by repeating the turning-on and turning-off of an auxiliary lighting device in an intermediate luminance zone in addition to the focus detection in the high and low luminance zones and obtaining signals of large contrasts from the difference between the light receiving outputs obtained at the time of turning-on and turning-off. CONSTITUTION:The focus detecting mode of this focus detector is made selectable among a 1st detecting mode in which the focus detection 2 is performed without auxiliary light 6a, a 2nd detecting mode in which the focus detection 2 is made based on the difference in each light receiving output between the state where the auxiliary light 6a is not used and another state where the focus detection 2 is performed with the light 6a, and a 3rd detecting mode in which the focus detection 2 is performed with the auxiliary light 6a. Then a control means which controls mode switching and auxiliary lighting is caused to perform the focus detection 2 with the 1st detecting mode in a high-luminance zone, with the 2nd detecting mode by repeating the turning-on and turning-off of the auxiliary light 6a in an intermediate-luminance zone, and with the 3rd detecting mode in a low-luminance zone. Therefore, sufficient focus detection can be performed on a low-contrast object when the luminance is high.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a passive focus detection device that performs focus detection based on the light output of a subject image formed by a focus detection optical system.

[&HEW( With this type of focus detection device, proper focus detection cannot be performed for dark objects or objects with low contrast.

Therefore, it is common practice to project auxiliary illumination light (for example, spora) onto the subject to partially increase the brightness of the subject and to provide contrast between light and dark to enable focus detection.

However, while the above-mentioned focus detection using auxiliary illumination light is effective when lighting a dark subject, it does not work effectively when shooting a subject with low frontal light, especially when the brightness is high. There was a sigh of relief. That is, when the subject brightness is high, the proportion of the auxiliary illumination light component in the amount of light received for focus detection is small, making it difficult to obtain sufficient contrast for focus detection.

SUMMARY OF THE INVENTION An object of the present invention is to provide a focus detection device that can perform focus detection using auxiliary illumination light at a brightness level as high as possible compared to conventional methods.

In addition, the present invention measures which of three brightness regions (high, middle, and low) the subject brightness belongs to, and sets the mode of focus detection using auxiliary illumination according to the brightness region. It is characterized by switching the V and controlling the auxiliary illumination. Specifically, the focus detection means performs focus detection without auxiliary illumination (i.e., with only constant light illumination). A first detection mode, and a detection mode of fjS2 in which focus detection is performed based on the difference between each received light output in a state without auxiliary illumination and in an auxiliary illumination state (i.e., a state in which the auxiliary illumination is added to the constant light illumination). , a third detection mode in which focus detection is performed in the auxiliary illumination state, and the control means for performing the mode switching and auxiliary illumination control turns off the auxiliary illumination in a high brightness area and operates in the first detection mode. In the intermediate brightness area, the auxiliary illumination is repeatedly turned on and off to perform focus detection in the second detection mode V. In the low brightness area, the auxiliary illumination is turned on and focus detection is performed in the third detection mode. I〒
It is configured so that it can be adjusted.

Production 1 With the above configuration, the t! S1. Focus detection is performed using fIS3 detection mode, and in the intermediate brightness region, the auxiliary illumination is repeatedly turned on and off, and the auxiliary illumination light component is extracted by taking the difference between the received light output when it is on and the received light output when it is off, and the auxiliary illumination light component is extracted with a large contrast. This becomes a signal and sufficient focus detection can be performed.

FIG. 1 is a principle diagram for explaining the principle of focus detection using auxiliary illumination.

In the figure, a focus detection section 2 receives light from a subject 7 that enters through a photographic lens 1, and performs focus detection based on the received light data. The range indicated by 5a to 5b is the focus detection area. The auxiliary illumination optical system consists of a light source 4 and a condensing floodlight lens 3, and when the amount of light on the subject is insufficient such as at night, or when the subject has no contrast, it projects illumination light onto the subject and uses the reflected light to focus. The detection unit 2 is configured so that focus detection can be performed. 6a-6
The range indicated by b indicates the area of the projected light beam.

FIG. 2 is a perspective view of a camera incorporating a focus detection device based on the above principle. In the figure, 10 is a camera body, and 11 is a photographic lens. The camera body 10 is provided with a window 12 for projecting illumination light onto a subject.

FIG. 3 is an example of a focus detection optical system having a plurality of focus detection areas. In the figure, 100a to 100d indicate areas on the pupil plane of the photographing lens 100 through which the focus detection light flux passes. Reference numeral 101 denotes a focus detection area mask placed immediately after the planned focal plane (not shown), and is provided with three apertures 101a, 10 lb, and 101c as shown in the figure, and these are arranged on the photographic screen. Three focus detection areas are determined.

The opening 101b is provided approximately at the center of the photographic screen, and the openings 101a and 101c are provided in one area other than the central portion of the photographic screen. and openings 101a, 10l
b, 101c have a rectangular shape, and the opening 101
b is provided at a position corresponding to the center of the photographing screen, and is arranged with the longitudinal direction being the left and right direction. or,
The apertures 101a and 101cli are provided on the left and right sides of the aperture 101b, at symmetrical positions with respect to a straight line passing through the optical axis of the photographing lens, and are arranged with the longitudinal direction facing up and down.

Note that this arrangement shows one example, and
102a, 102b,
102c are the openings 101a, 101b, 1, respectively.
A condenser lens placed immediately after 01c,
It functions to form an image of aperture mask apertures 103a to 103r, which will be described later, on the exit pupil plane of the photographing lens 100. That is, the aperture mask apertures 103a and 103b are formed into images 100a and 1005, respectively, on the exit pupil plane of the photographic lens 100 by the condenser lens 102b, and the aperture mask apertures 103c and 103d are formed on the exit pupil plane of the photographic lens 100 by the condenser lens 102a. 100d and 1 on top respectively
00c, and the aperture mask apertures 103e and 103f
is a condenser lens 102cl photographic lens 100
The images are formed on the exit pupil planes of 100d and 100c, respectively. In this way, the diaphragm mask openings 103a to 103f function to determine the focus detection light flux area within the exit pupil plane of the photographing lens 100.

Immediately after the aperture mask 103, an imaging optical member 104 is arranged. The imaging optical member 104 includes an imaging lens 104.
a to 104f are formed and arranged in the optical path of the aperture mask openings 103a to 103f, respectively. These imaging lenses 7: 104a to 104f are for re-forming the image formed near the focal plane onto the focus detection light receiving element surface 105. 106a, 106b, 106
c is a focus detection sensor composed of a one-dimensional sensor such as a CCD, and sensor 106a is a focus detection sensor composed of a one-dimensional sensor such as a CCD.
a.

The sensor 106b is located at a position where it receives the image formed by the imaging lenses 103e and 103f, and the sensor 106C is located at a position where it receives the image formed by the imaging lenses 103c and 103d. It is placed in a position to receive light. That is, these sensors are connected to the aperture mask openings (103a and 103b, 103c and 103d)
, 103e and 103F) are arranged in the line direction,
For example, the focal state of the photographic lens is detected by taking a phase diagram of an image formed through the aperture mask aperture 103a and an image formed through the aperture mask aperture 103b.

The aperture mask openings 103a and 1' 03b are arranged along the longitudinal direction of the aperture 101b, and the aperture mask apertures 103c and 103d are arranged along the longitudinal direction of the aperture 101b.
Since the pattern mask openings 103e and 103f are arranged along the longitudinal direction of the opening 101c, the direction of the sensor 106a and the direction of the sensors 106b and 106c are the same. It is 90° different from the Since the sensors 106a are arranged in the horizontal direction, they have a focus detection ability for subjects with contrast in the horizontal direction, and since the sensors 106b and 106c are arranged in the vertical direction, they can detect subjects with contrast in the vertical direction. In contrast, it has focus detection ability.

FIG. 4 shows an example of a viewing field image, where 200 indicates the entire photographic screen, and 200
Areas indicated by a, 200b, and 200c indicate focus detection areas. These focus detection areas are the sensor 106
This corresponds to the light receiving areas a, 106b, and 106c.

FIG. 5 shows an embodiment of a light projecting optical system suitable for the present invention.

In FIG. 5, 401 is a light projecting lens for directing and projecting light from a light emitting unit 402 such as an LED toward a subject. The light from the light emitting unit 402 is transmitted by the light projection lens 401.
It is projected as a bright area 402' on the subject. Further, on the light emitting part 402, electrodes 403, 404, 4
05, 4.06 are arranged, and these electrodes are projected as dark areas on the subject by the projecting lens 401.
They are projected as 404', 405', and 406', giving a contrast of brightness and darkness on the subject. Further, the electrode 403 and the electrode 404 are connected to the same lead C1,
The electrode 405 is connected to the lead C3, and the electrode 406 is connected to the lead C3.
2, and the 7 nodes of the light emitting section 402 are connected to the substrate 407.
It is common to each electrode on the top and is connected to lead A.

In this way, the reason why leads are placed separately for each electrode is f! This will be explained using diagram IJ6. In FIG. 6, the focus detection section within the camera body 10 is 1. Focus detection is performed using the luminous flux in the range indicated by -12. On the other hand, the auxiliary lighting device inside the camera body
Since it is located above 0 by Δy, a disparity of Δy occurs. Therefore, the optical axis A of the auxiliary lighting VC. teeth,
It is tilted downward by Δθ with respect to ro, and the luminous flux of the auxiliary illumination at this time has an upper limit A1 and a lower limit A2. At this time, the focus detection area 60 when the subject distance is short like Ll
The relative positional relationship between 1 and the auxiliary lighting area 602 is as shown in the upper right of Fig. 6 (y-z plane sectional view (x = L 1 )). Focus detection area 601' and auxiliary illumination area 602'
Relative position rI! The relationship is as shown in the upper left of figure fjS6 (y-z plane cross-sectional view (x = L 2 )).Generally, as the illumination distance increases, the illuminance decreases in proportion to the reciprocal of the distance, so The farther the distance, the more it is necessary to increase the illuminance of the auxiliary lighting.

In other words, in FIG. 6, the illuminance (
It is desirable to increase the illuminance at the subject distance L2 (at the top of the auxiliary lighting area) than at the bottom of the auxiliary lighting area. For this reason, by varying the amount of current flowing through each electrode, a difference in illuminance is created in the auxiliary lighting area. Specifically, electrode 4
03,404, a small amount of current is applied to the electrodes 405,404.
06 can be achieved by applying a large amount of current.

In addition, in FIG. 6, the focus detection area 20 of FIG.
0a is explained.

FIG. 7 is a block diagram showing an example of a focus detection system.

The configuration will be explained below.

300a, 300b, and 300c are CCD focus detection sensors (for example, 106a and 106a in FIG. 3, respectively);
106b and 106c). 301 is COD
A drive circuit, the focus detection sensor 300a,
The focus detection sensors 300a, 300b send signals for driving the focus detection sensors 300b, 300c.

<Margin below> Output to 300c. 302 is an A/D conversion circuit that converts analog signals from each focus detection sensor sent from the CCD drive circuit 301 into digital signals;
The signal is supplied to the control calculation circuit 303. Control calculation circuit 303
controls the system, and stores the signals outputted from the focus detection sensors 300a, 300b, and 300c, passed through the CCD drive circuit 301, and converted into digital data by the A/D conversion circuit 302 in a predetermined memory.
Processing is performed according to a predetermined algorithm to calculate the defocus amount and defocus direction of the photographing lens.

304 is a subtraction circuit, into which the output signal of the control calculation circuit 303 and correction data (C) regarding the spherical aberration of the photographing lens outputted from the register 313 are input, and the correction data (C) is subtracted from the defocus amount. and is output together with a direction signal. Reference numeral 305 denotes an adder circuit, into which the output signal (defocus amount and direction signal) of the above-mentioned control calculation circuit 303 and correction data (C) regarding the spherical aberration of the photographing lens outputted from the register 313 are inputted, and the defocus amount is calculated. Correction data (C) is added to the direction signal and output together with the direction signal. 306 is a selector circuit, into which the output of the subtraction circuit 304 and the output of the addition circuit 305 described above are input, and further a positive or negative signal is given from the register 313, and according to this signal, if the signal is negative, the subtraction circuit 304 If the signal is a positive signal, the output data and V signal of the adder circuit 305 are selected and output. This defocus data output from the selector circuit 306 is input to a multiplier circuit 310 and a display comparison circuit 307.On the other hand, the defocus data is inputted to a multiplier circuit 310 from a register 314 as a conversion coefficient (K) for focus adjustment.
) is given. This conversion coefficient (K) includes the focal length necessary to obtain the lens movement equivalent to the amount of defocus, the lens movement*PS angle (information on the contracted configuration (for example, information on the helicoid lead, etc.) , the required rotation speed (N) of the motor can be obtained by multiplying the defocus amount by the conversion coefficient.This motor rotation speed (N)
The data and the signal indicating the rotation direction are sent to the motor drive circuit 31.
given to 1. Reference numeral 307 is a display comparison circuit, into which the above-mentioned defocus amount and focusing range data from the in-focus data circuit 308 are input, and both of these data are compared to display in-focus or out-of-focus data. Output. 30
9 is a display circuit, and the output of the display comparison circuit 307;
A defocus direction signal output from the selector circuit 306 is input, and the in-focus or out-of-focus direction is also displayed if the focus is out of focus. As described above, data on the motor rotation speed N and a signal on the rotation direction are input to the motor drive circuit 311, and the motor M is rotated according to these information. The rotation of the motor M is transmitted to the drive shaft DA via a gear train GT and a slip mechanism SL as shown by dotted lines. An encoder consisting of seven automatic couplers PC is provided at a position after passing through the slip Ff11vtSL, and monitors the rotation of the drive shaft DA and feeds it back to the motor drive circuit 311 to rotate the motor a predetermined number of times. Reference numeral 324 denotes a bird 1 circuit, which generates a fish/α detection start signal in response to the ON/OFF of the shirt button or a separate switch, and this signal is sent to the control calculation circuit 30.
3.

312.313.314 is a register circuit and a reading circuit R
Focal length information (f) of the photographic lens, correction data (C) regarding aberrations of the photographic lens, and conversion coefficient (K) for focus adjustment are read from D and inputted, respectively.

315 is a photometry circuit that measures the subject brightness, and compares two reference brightness values (for example, By, = 4 and Bv2 = O) with the measured subject brightness By, and determines whether the subject brightness is in a high brightness area (
Bv>Bv+), but when installed at low brightness (Bv<Bv2)
However, a signal indicating which brightness region is present is input to the control arithmetic circuit 303 to determine whether the brightness is in the open brightness region (Bv, ≦Bv≦By,).

Signal #1 (k) from the control circuit 303 is connected to the LED drive circuit, and when the signal line (k) is at a high level, the LED drive circuit shown in FIG. 8 is activated and the light emitting diode L is activated.
Turn on D. In other words, the signal line from the control calculation circuit
When k'' becomes high level, the transistor Tr4 becomes conductive, and the operational amplifier OP1 becomes operational for the first time. The potential of R1 is input. Initially R
Since the potential of 1 is GND level, the output of OPI is “Hi”
As a result, the transistor Tri.

Tr2. Each Tr3 becomes conductive.

OPI is set so that the potential of R1 becomes a predetermined reference voltage.
In order to control i, Tr2, Tr3, constant current I II
I 2. I 3 (L E D terminals C1, C2, C3
This makes it possible to create a current that flows through the When the predetermined reference voltage is 0.5v, R1=5Ω, R2=R3=
By setting the resistance to 3.3Ω, 1. =100+*A, l2
= I, = 150 logic A, and the terminal C of the LED
The current values of I, C2, and C3 can be controlled.

The configuration on the camera body side has been described above, and next, the vI configuration on the interchangeable lens side will be explained. Interchangeable lenses are number 7
In the figure, it is shown separated by a dashed line at the lower left.

This interchangeable lens is shown as an example of a zoom lens. ZR
is a zoom ring which can be operated from the outside and has a brush BR attached thereto which can rotate integrally with the zoom ring ZR.

Corresponding to the brush BR of the zoom ring ZR, a code plate CD is provided on the lens barrel fixing part (not shown), and a digital code signal corresponding to each focal length is generated according to the rotation of the zoom ring, that is, the setting of the focal length. It is configured so that it can occur. The code signal is connected to be input to a lens information output circuit LID including a ROM. The ROM stores lens data such as focal length information (f) of the photographic lens necessary for AF control on the camera body side, correction data (C) regarding aberrations, and motor rotation speed conversion coefficient (K). . 7 addresses of the ROM are specified by the digital code signal, and the above-mentioned lens data is read from the reading circuit RD on the camera body side as the reading starts, and is transferred to the renostars 312, 313, and 314, respectively. still,
The focal length information (f) of the photographing lens, the correction data regarding aberrations (C), and the motor rotation speed conversion coefficient (K) are advanced in accordance with zooming of the zoom lens, and are output to the reading circuit RD. Ru. The terminals between the camera body and the interchangeable lens include a power supply terminal, a synchronization clock pulse terminal, a read signal terminal, a serial data terminal, and a ground terminal. Further, in order to drive the 7 orcusing lens, the driven shaft FD is in a meshing relationship with the 7 orcus ring FR.

The operation of the configuration as described above will be explained below. When the interchangeable lens is attached to the camera body, the lens nine report output circuit LID and the reading circuit RD are connected through the terminal, and the ground terminal is also connected. Furthermore, in order to move the Orcasing Lens, mechanical engagement is made by the unevenness between the drive shaft DA and the driven shaft FD. When the user touches the shutter button etc. to perform focusing, the lens information output circuit LI is first transmitted from the reading circuit RD via the power terminal.
Power is applied to D, and the contents of the ROM are read out from the lens information output circuit LID in accordance with the read signals from the synchronization clock pulse terminal and the read signal terminal, and the focal length information (f) is sent to the renostar 312, and the correction data regarding aberration (
C) is applied to Renostar 313 by the motor rotation speed conversion coefficient (K
) is imported into the renostar 314. This capture is continued at predetermined timing thereafter, and the data is updated from time to time. The content of this read ROM is the brush B that moves according to the setting of the zoom ring ZR.
It is determined by the address specified by the denotal code of the code plate CD determined by the position R. Therefore, for example, even if the focal length of a zoom lens changes according to zooming, the focal length information (f) included in the ROM contents changes accordingly, so the lens information output circuit LID and reading circuit RD are The renost circuit 312 is appropriately incorporated through the renost circuit 312. When the data acquisition is completed, the control calculation circuit 303 outputs a CCD drive pulse to the CCD drive circuit 301 via the signal (ia).

When the CCD drive circuit pulse described above is applied to the CCD drive circuit 301, a CCD integration start signal is sent from the CCD drive circuit 301 to the focus detection sensors 300a, 300b=30.
given to 0c. Each focus detection sensor has an output V ad of each monitor light receiving element (corresponding to 201 in FIG. 9).
, -V ad3 to the CCD drive circuit 301, and C
The CD drive circuit 301 compares ■ ad and ~V ad with the reference voltage V ref, and when they reach a predetermined voltage,
In addition to outputting a CCD integration end signal to each focus detection sensor, a CCD drive end signal is output to the control calculation circuit 303. Furthermore, if the CCD drive circuit 301 does not output a CCD drive end signal even after a predetermined period of time has elapsed after outputting the CCDff1 pulse length to the CCD drive circuit 301, the control calculation circuit 303 outputs the CCDff1 pulse length to the CCD drive circuit 301. fart,
Outputs a CCD drive forced termination pulse and closes the CCD drive circuit 3.
01 outputs a CCD integration end signal to each focus detection sensor. At this time, the CCD drive circuit 301 is configured to multiply each focus detection sensor output by a gain corresponding to the level of each monitor output V ad1+V ad3.

After this, the CCD drive circuit 301 drives each focus 5I'7. Output the detection sensor output to the A/D conversion output circuit 302,
Each focus detection sensor output digitized by the A/D conversion circuit 302 is stored in a predetermined memory in the control calculation circuit 303. Thereafter, the control calculation circuit 303 calculates and processes the data according to a predetermined algorithm, and obtains a so-called phase difference, thereby obtaining the defocus amount and defocus direction signal for each focus detection sensor at that time.

When there are a plurality of focus detection areas, it is necessary to perform processing such as determining which area's data should be adopted, but this is not the purpose of this application and will therefore be omitted. (For example, see Japanese Unexamined Patent Publication No. 59-146028 for details.) This theme 7 orcus amount, ΔL, and defocus direction signals are sent to the subtraction circuit 304.
and the adder circuit 306. On the other hand, the correction value C is output from the register circuit 313, and the subtraction circuit 31
4 and one input terminal of the adder circuit 305.

The register circuit 313 provides the selector circuit 306 with a correction direction signal +Or- in addition to the correction value C described above. Then, according to the correction direction signal output from the register circuit 313, for example, if it is a (-) signal, the subtraction circuit 304
The data and signal from the adder circuit 305 are taken into the selector circuit 306, and if it is (+), the data and signal from the adder circuit 305 are taken into the selector circuit 30G. Selector circuit 3
The data and signals selected by 06 are transferred to the multiplication circuit 3.
10 and is given to the display comparison circuit 307, and the filler circuit 310
Then, the rotation speed data N is multiplied by the motor rotation speed conversion coefficient from the register 314 to calculate the rotation speed data N, which is then provided to the motor drive circuit 311.

The display comparison circuit 307 compares the defocus amount data with the data of the in-focus data circuit 308, and if the defocus amount data is within a predetermined focusing range, the focus display element is turned on.

In addition to the selector circuit 306, a signal in the defocus direction is also given to the motor drive circuit 311 and the display circuit 309, and in order to instruct the rotation direction of the motor M and display the defocus state, either the left or right of the out-of-focus display element is sent. Turn it on. The motor M rotates according to the motor rotation speed data N and the rotation direction signal input to the motor drive circuit 311. The rotation of the motor is transmitted to the drive shaft DA via the gear train GT and the SLIP modification SL, and is further transmitted to the 7-ocanng ring FR via the driven shaft FD of the interchangeable lens, and then to the focusing optical system (not shown). is moved in the optical axis direction by the amount of defocus.

The rotation of the drive shaft DA is monitored by an encoder PC consisting of seven autocouplers, and is accurately controlled by feeding back to the motor drive circuit 311.

Here, when the brightness of the subject is low or when the contrast is low, it becomes difficult for the control calculation circuit 303 to obtain the correct defocus amount and defocus direction. In such a case, the signal line "k" is set to a high level and the LD is turned on to illuminate the object and provide contrast, and the next distance measurement operation is started.

FIG. 9 shows a detailed diagram of the focus detection sensor.

Reference numeral 200 denotes a line sensor composed of a one-dimensional photodiode, the output of which is transferred to a shift reno star section 204 via a transfer date 203 and output from an output terminal Vss of an operational amplifier 206. 201 is a rectangular photodiode, the output of which is output from the output terminal Vad of the operational amplifier 205. The photodiode 201 is a monitor for measuring the amount of light incident on the line sensor 200, and is placed near the line sensor 200.

202 is an integral clear date for clearing the charge generated from the line sensor 200 when φR is at a high level; 20
3 is a charge transfer date, and when φT is at a high level, the charge generated from the line sensor 200V is transferred to the shift register section 2.
Accumulate in 04. A shift register section 204 transfers the accumulated charges to the operational amplifier 206 in response to clock pulses φ1 and φ2 to read signals. The output signal Vad from the monitor 201 is C in FIG.
It is output to the CD drive circuit 301. Also, line sensor 2
The output signal Vss from 00 is the CCD in FIG.
It is output to the drive circuit 301.

Here, monitor output Vad and line sensor output Vss
Let me explain in more detail. CCD drive circuit 30
1, the CCD drive start signal is sent to the focus detection sensor 30.
0a (300b, 300c), first φ
R becomes high level, and the charge in the monitor section 201 is discharged through the integral clear date 207, and the monitor section 201
Initial settings are made. At the same time, line sensor 200
niM! Integrate the charge that is rt\ clear date 202
Initial settings of the exposed line sensor 200 are performed via the .

Then, start the M product of charges by closing the integral clear date. Since the output of the monitor part 201 is accumulated and output from the output terminal Vad of the operational amplifier 205, the monitor output Vad decreases (or increases) with time. When the level of this monitor output ■ad reaches a predetermined level (for example, Vref), the CCD drive circuit 301 outputs a charge transfer pulse φT to the transfer date 203, and the charge generated in the line sensor 200 is transferred via the transfer date 203. and is transferred to the shift register section 204.

The amount of light incident on the monitor output Vad is low, and even if integration is performed for a certain period of time, the monitor output ~'act will not reach the above-mentioned V.
If the charge transfer pulse φT is not reached to the transfer date 203 by the signal of the CCD drive circuit 301 without further reading the integral operation, the line sensor 2
The charge generated at 00 is transferred to the shift register section 204. Furthermore, the charges in the shift register section 204 are sequentially output to the CCD drive circuit 301 according to signals from the CCD drive circuit 301.

Next, the auxiliary light mode in the present invention will be elaborated.

As shown in FIG. 10, the auxiliary light mode (AL mode) has two types: a low light complementary type (ALB) and a low light complementary type (ALS).

Low light supplement type (ALB) means that the subject is dark (
For example, if Bv≦0) the CCD cannot obtain enough light to measure the distance, turn on the auxiliary light LED to illuminate the subject,
Moreover, distance measurement is made possible by providing effective contrast.

The low-angle supplement type is a type that lights up the auxiliary light LED to provide effective contrast when the distance measurement calculation becomes impossible due to lack of correlation value in distance measurement calculations when the subject has low contrast. This enables distance measurement without performing light removal processing or addition processing. (Details of the low contrast complement type will be described later.) In addition, A L S on and l\LSo [in Fig. 10] are used to control whether the auxiliary light is emitted or not emitted during CCD integration, and are used to remove standing light. Used in processing.

Next, the processing within the control arithmetic circuit 303 is explained in FIG.
This will be explained using a chart.

The control calculation circuit is activated by a switch such as a shutter button (#1), and the auxiliary light mode is set to OFF. Then, in #2, it is determined whether the mode is auxiliary light mode. Here, since the auxiliary light mode is set to OFF in #1, CCD integration in #3 is performed.

After CCD integration is completed, auxiliary light mode is turned on and off in #4.
Make a decision on FF. Since the auxiliary light mode is OFF here as well, the DATA dump of I5 is performed. DAT
A-gump means that the output obtained by the CCD is subjected to analog-to-digital conversion (A/D) and stored in a predetermined memory within the control calculation circuit 303. Thereafter, a determination is made as to whether to turn on or off the rezo and auxiliary light mode in #6. Since the auxiliary light mode is OFF here as well, the distance measurement calculation in #7 is performed.

In the distance measurement calculation, a distance measurement value and a distance measurement reliability determination value indicating the reliability of the distance measurement value are calculated from the memorized output of the CCD according to a predetermined algorithm. Then, in step 8, it is determined whether the distance measurement reliability determination value is within a predetermined level, and if it is outside the predetermined level, it is determined that distance measurement is impossible (low contrast). Here, first, assuming that the distance measurement reliability judgment value is within a predetermined level, then #
In step 9, it is determined whether or not the camera is in focus based on the distance measurement value calculated in step #7. If it is determined that the camera is in focus, an in-focus display is performed in #16. If the lens is not in focus, the lens is driven by a predetermined amount to bring it into focus based on the distance measurement value calculated in step 7, and the process returns to #2 to perform the next distance measurement. In the above loop, the auxiliary light mode is O
It is a FF and performs distance measurement without auxiliary illumination.

Next, the case where it is determined that distance measurement is impossible (low contrast) in #8 will be described.

If it is determined in #8 that distance measurement is not possible (low contrast), it is determined in #11 whether or not the auxiliary light mode is selected. Here, since the auxiliary light mode is OFF, the process proceeds to #12. In #12, it is determined whether the subject brightness is higher than a predetermined value (for example, By=4), and if it is higher than the predetermined value, the auxiliary light mode is not entered. This means that when the subject brightness is high,
This is because even if an auxiliary light is emitted, an effective CCD output (mount last) cannot be obtained. (C
CD output = CCD output at the time of projection. ) Therefore, if the subject brightness is higher than the predetermined value in #12, a low contrast display (distance measurement impossible display) is performed in #23, and the process moves to step #3. Further, if the subject brightness is lower than a predetermined value, the second brightness level (here, B
v=O) and the subject brightness. For example, if the subject brightness is lower than the second brightness level, the fill light mode is set in #14 and the low light supplement type flag (
ALB) is set and the process advances to #2. In addition, if the subject brightness is higher than the second brightness level, the auxiliary light mode is set in #15 and the low contrast supplement type flag (A L
S) is set and the process advances to #2.

Here, to explain the processing from #2 onwards after the flag ALB is set, first, in #2 it is determined that the auxiliary light mode is on, in #17 the auxiliary light type is determined and the auxiliary lighting LED is turned on. Or OFF is controlled. Here, since it is an ALB type, we will use LED for auxiliary lighting.
is turned on.

Then, CCD integration is performed in #3, and after the COD integration is completed, the auxiliary light mode is determined in #4, the auxiliary illumination LED is set to 0FFL in #8, and then the DAT is set in #5.
A dump is performed.

Thereafter, the auxiliary light mode is determined in step 6, and the auxiliary light type is determined in #19, and in this case, since it is the ALB type, the process moves to distance measurement @ki in #7. After that, based on the calculation result in #7, it is determined in #8 whether distance measurement is not possible, and if distance measurement is not possible, it is determined in step 11 that the auxiliary light mode is selected.
In step #22, the auxiliary light mode is turned off, and in step #23, a round display is performed, and the process moves to step #3. Also, if distance measurement is possible at #8, focus 4! at #9! III
fr, and if focus is determined, in-focus display is performed in step #16, and distance measurement is completed. Also, if focus is not determined in #9, the lens is driven by a predetermined amount in #10,
Proceed to #2 for the next distance measurement.

In this case, the next distance measurement is performed with the auxiliary light mode ALB type unchanged.

Next, the case where the auxiliary light mode ALS type is set in #15 will be described.

After the flag ALS is set in #15, the process proceeds to #2, where the auxiliary light mode is disconnected from M, and the auxiliary light type is determined in #17, and ALS and ALB are determined, and ALson and ALSoff are determined. is added to control the ON/OFF of the auxiliary lighting LED. Here, since it is the first of the A L S type, we will use the LED for auxiliary lighting.
Turn on and perform #3 CCD integration. After the COD integration is completed, DATA gump is performed in #5, then the auxiliary light mode is determined in #4, the ALS type is determined in #19, and the process moves to #20. CC in #20
Pre-processing such as D output addition processing and constant light processing I! ! (Details will be described later) are performed, and it is determined in #21 whether the result of the preprocessing satisfies a predetermined condition (details will be described later). If it is determined that the predetermined condition is satisfied, distance measurement calculation is performed in #7 based on the preprocessed DATA. The explanation after that is the same as that for ALB, so it will be omitted.

Further, if the pre-processed DATA is cut off in the well 21 if it does not satisfy a predetermined condition, the process proceeds to #2. From then on, AL
S type distance measurement is continued, but the CCD integration when the auxiliary light is emitted and the CCD integration when the auxiliary light is not emitted are performed alternately. This will be explained using chart 70 in FIG. First, #1011:1', 7
Rough 'A L So+1 count 4: -7 is hit, and the number of times N is set to 1 at well 102.

(The number of times N indicates the number of times that the CCD integration when the auxiliary light is emitted and the CCD integration when the auxiliary light is not lit are made into one loop.) #101. #102 corresponds to #15 in FIG.

After that, B1 to Bn are set to O in #103. B1 to Bn are memories that add the output obtained by subtracting the CCD data P(n) during non-emission from the CCD data R(n) during light emission, and are initially set to 0. Then, in #104 (corresponding to #2 and #17 in FIG. 11), the auxiliary light is turned on α, and in #105, a timer inside the control calculation is started.

This timer is used to monitor the charge accumulation time (integration time) of the CCD, as will be described later.

Then, at #106, the CCD integration start signal is sent from the control calculation circuit to the rlCCD drive circuit, and the CCD
Start charge M82. Thereafter, in #107, it is determined whether the CCD integration has been completed. If it has ended, proceed to #109.

Also, if it has not finished, proceed to #108 and #10
The timer started in step 5 has been preset.
How about more than AXT I NT time? q cut, if, M
A. If it is shorter than the XTINT time, the process advances to #107 and it is again determined whether the CCD integration has been completed. Also, M
If the AXTINT time or more is reached, the control calculation circuit sends a CCD integration forced termination signal to the CCD drive circuit, and after the CCD integration is terminated, the process proceeds to #109.

In #109, the CCD at the time of auxiliary light emission
A timer count TM indicating the integration time is memorized.

This timer value TM is used as the integration time for the next non-emission CCD integration.

Thereafter, in #110, the auxiliary light is turned off, and in #111, the CCD data R(1) to R(n) at the time of light projection are stored in memory. Then, addition processing is performed in #112. Here, data Bn after addition processing and constant light processing in Ascaris nigra are added to data R(1) to R when the auxiliary light is emitted this time.
(n) is added. Next, a flag ALSofr is set in #113, a timer is started in #114, and CCD integration is started in #115.

The integral at this time is the integral when the auxiliary light is not emitted, and only the steady light is received.

Then, in #116, the CCD integration continues until the timer reaches the integration time TM of the previous auxiliary light emission, and when the timer reaches TM or more, the CCD integration is forcibly terminated, and in #117 Data P when the auxiliary light is not emitted (1
) to P (n) are stored.

Here, the reason why the integration time when the auxiliary light is not being emitted is made to match the integration time when the auxiliary light is being emitted is that the output of the steady light component is the same when the auxiliary light is being emitted and when the filler light is not being emitted (i.e., by subtraction). This is because the output after this is only the output of the auxiliary illumination light component.

Thereafter, ambient light processing is performed in #118.

In #118, 81 to Bn are created by subtracting the current data P(1) to P(11) when the auxiliary light is not emitted from A1 to 80 calculated in #112.

Thereafter, in #119, it is determined whether the difference between the maximum value of Bn and the minimum value of Bn is greater than or equal to a certain amount. When it exceeds a certain amount,
It is assumed that sufficient contrast has been obtained for distance measurement, and the process moves to distance measurement calculation (#7). Further, if the difference between the maximum value of Bn and the minimum value of Bn is not equal to or greater than a certain amount, a constant J is compared with the number of times N indicating the loop number in #120. When the loop has been repeated a predetermined number of times 5 times or more, the subsequent processing is stopped and the process moves to distance measuring liquid n (#7), and the loop is repeated a predetermined number of times 3 or more.
If it does not reach the number of times, count up N (#121
)L, flag ALson)L($122), #
Proceed to 104 to continue the next loop.

Note that the number of times limit is included in #120, for example, when the subject is very far away, the data when the fill light is being emitted is ≠ the data when the fill light is not being emitted, and as a result of the constant light processing, This is to prevent a situation where effective contrast cannot be obtained no matter how many times the loop is turned and it becomes impossible to exit the loop.

As described above, by performing the addition process and the constant light process, effective contrast can be obtained and distance measurement becomes possible.

In the above-described embodiments, TTL focus detection in which the focus detection light receiving section such as a CCD is provided behind the photographic lens is explained as an example, but the present invention is applicable to the case where the focus detection light receiving section is provided as the photographing lens. [As described above, according to the present invention, when the subject brightness is high, intermediate, or
The focus detection mode is switched and the auxiliary illumination is controlled depending on which of the three low brightness areas the auxiliary illumination is in, and in the case of an intermediate brightness level, the auxiliary illumination is repeatedly turned on and off, and the received light output when the auxiliary illumination is on is changed. Since we decided to extract the auxiliary illumination light component by finding the difference between the received light output when the auxiliary illumination is off, we can obtain enough light even in the brightness range 7, where the proportion of the auxiliary illumination light component in the amount of light received when the auxiliary illumination is on is small. Focus detection can be performed.

[Brief explanation of the drawing]

Figure 1 is a principle diagram showing the principle of focus detection using auxiliary illumination.
Fig. 2 is a perspective view of a camera to which the present invention is applied, Fig. 3 is a perspective view showing an example of a focus detection optical system, Fig. 4 is a view showing an example of a 7T-ing field of view, and Fig. 5 is an auxiliary illumination light source. FIG. 6 is a diagram showing the distribution of the auxiliary illumination light flux, FIG. 7 is a circuit block diagram showing the overall configuration of the focus detection device according to the present invention, and FIG. 8 is an LED drive unit. FIG. 9 is a circuit diagram of the light receiving means, and FIGS. 10 to 12 are flowcharts showing the operation of the control calculation circuit of FIG. 7. 100-104: Focus detection light 'Fj! %, 105゜2
00.300: Light receiving means, #7: Focus detection means, 315
: Photometric means, wells 101 to #122: Control means Applicant Minolta Camera Co., Ltd. No. 1 Fig. 3 Mouth 1'O4 Fig. 3 ◆ V U O + Di

Claims (1)

[Claims] A focus detection optical system, a light receiving means for receiving a subject image formed by the optical system, an auxiliary illumination light source for projecting focus detection auxiliary light onto the subject, and the light receiving means when the light source is in a non-illuminated state. a first focus detection mode in which focus detection is performed based on the output of the light source; a second focus detection mode in which focus detection is performed based on the difference between each output of the light receiving means in non-illumination and illumination states of the light source; a focus detection means for selectively detecting a focus adjustment state of a subject in one of a third focus detection mode in which focus detection is performed based on an output of the light receiving means in an illumination state of a light source; a measuring means for measuring whether the object is in a higher brightness region, in an intermediate brightness region between the first brightness value and the second brightness value, or in a lower brightness region lower than the second brightness value; is in a high brightness region, the light source is deactivated and the focus detection means is caused to perform focus detection in a first detection mode, and when the subject brightness is in an intermediate brightness region, the light source is repeatedly activated and deactivated, and Photometry is configured to cause the focus detection means to perform focus detection in a second detection mode, and to activate the light source when the subject brightness is in a low brightness region, and to cause the focus detection means to perform focus detection in a third detection mode. A focus detection device comprising: control means for controlling the light source and focus detection means based on photometric results of the means.