Automatic focus adjustment camera

To improve the responsiveness of an automatic focus adjustment camera in which focus adjustment of the photographic lens is performed based on the results of focus detection in multiple regions, defocus amounts of the photographic optical system in multiple focus detection regions are detected asynchronously and independently of one another in multiple focus detection regions that are established on the photographic screen of the photographic optical system. The value of the defocus amounts in the various focus detection regions are compensated at times T3, T5, T8 and T9 when the defocus amounts are detected in the various focus detection regions, or at preset time intervals W, and the final defocus amount is set from among these multiple compensated defocus amounts in order to drive the photographic optical system.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an automatic focus adjustment camera that 
performs focus adjustment of the photographic optical system according to 
focus detection results in multiple focus detection regions on a 
photographic screen. 
2. Description of Related Art 
An automatic focus adjustment camera has been known that performs focus 
adjustment in multiple focus detection regions established on a 
photographic screen of a photographic optical system, detects the defocus 
amount of the photographic optical system in each of the focus detection 
regions, sets a final defocus amount from among these multiple defocus 
amounts, and drives the photographic optical system in accordance with 
this final defocus amount. 
However, in conventional automatic focus adjustment cameras, each time 
focus detection is performed, the focus detection sensors are operated in 
all focus detection regions simultaneously, the focus detection 
computation is performed with respect to the output obtained from all of 
the sensors, and the final defocus amount is set after the defocus amounts 
from all of the focus detection regions are computed. As a result, when 
the length of time it takes for some of the focus detection regions to 
compute the defocus amount is large, the length of time it takes-to 
compute the final defocus amount becomes prolonged because of the length 
of time needed in these focus detection regions, causing the 
responsiveness of the focus adjustment to diminish. 
For instance, when electric charge accumulation type sensors are used as 
the focus detection sensors, the electric charge accumulation time of the 
sensors that capture dim subjects is relatively long, so that the time 
interval in which the final defocus amount is computed increases in 
response to the electric charge accumulation time of the sensors that 
capture dim subjects, even when other sensors capture bright subjects. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to improve the responsiveness of 
an automatic focus adjustment camera that performs focus adjustment of the 
photographic lens based on the focus detection results in multiple 
regions. 
This and other objects of the invention are achieved by providing an 
automatic focus adjustment camera equipped with a photographic optical 
system that can move along the direction of the optical axis in order to 
form an image of the subject on the intended focus surface, multiple focus 
detectors that are provided in order to respond to multiple focus 
detection regions established on the photographic screen of the 
photographic optical system and that detect the amount of defocus of the 
photographic optical system in each focus detection region, a setting 
device that sets the final defocus amount from the multiple defocus 
amounts detected by the multiple focus detectors, and a drive device that 
focuses the photographic optical system by driving it in accordance with 
the final defocus amount set by the setting device. The multiple focus 
detectors operate asynchronously and independently of one another. 
According to another aspect of the invention, each of the focus detectors 
possesses a focus detection optical system that forms an image of the 
subject with light from each focus detection region, a sensor that 
receives light from the image of the subject formed by the focus detection 
optical system, and computation circuits that compute the amount of 
defocus of the photographic optical system in each focus detection region 
based on the output of the sensors. 
The sensors may be the electric charge accumulation type, and each of the 
focus detectors may possess an accumulation controller that controls the 
electric charge accumulation start time and the accumulation interval of 
each electric charge accumulation type sensor asynchronously and 
independently from the electric charge accumulation start time and the 
accumulation interval of the other electric charge accumulation type 
sensor. 
The setting device may possess a memory that memorizes the multiple defocus 
amounts detected by the multiple focus detectors, and when the various 
focus detectors detect the defocus amounts, the camera compensates the 
defocus amounts stored in the memory in accordance with the amount of 
movement of the photographic optical system to that point, and also sets 
the final defocus amount from among the defocus amounts detected at that 
time and the compensated defocus amounts. 
The setting device may possess a memory that memorizes the multiple defocus 
amounts detected by the multiple focus detectors, and at preset times 
compensates each defocus amount stored in the memory in accordance with 
the amount of movement of the photographic optical system to that point, 
and also sets the final defocus amount from among the compensated defocus 
amounts. 
In accordance with another aspect of the invention, an automatic focus 
adjustment camera is equipped with a photographic optical system that can 
move along the direction of the optical axis in order to form an image of 
the subject on the intended focus surface, multiple focus detection 
optical systems that are provided in order to respond to multiple focus 
detection regions established on the photographic screen of the 
photographic optical system and that form an image of the subject with 
light from each focus detection region, multiple electric charge 
accumulation type sensors that receive light from the multiple images of 
the subject formed by the multiple focus detection optical systems, 
accumulation controllers that control the electric charge accumulation 
start times and the accumulation interval of the electric charge 
accumulation type sensors, a computation device that computes the defocus 
amount of the photographic optical system in each focus detection region 
based on the output of the multiple electric charge accumulation type 
sensors, a setting device that sets the final defocus amount from among 
the multiple defocus amounts computed by the computation device, and a 
drive device that focuses the photographic optical system by driving it in 
accordance with the final defocus amount set by the setting device. The 
accumulation controllers control the multiple electric charge accumulation 
sensors asynchronously and independently from one another. 
The automatic focus adjustment camera may further include temporary 
retention devices that temporarily retain the output of the multiple 
electric charge accumulation type sensors, and an input controller that 
controls the temporary retention devices so that the outputs of the 
multiple electric charge accumulation type sensors are not simultaneously 
input into the computation device. 
The setting device may possess a memory that memorizes the defocus amounts 
in each focus detection region computed by the computation device, and 
when the computation device computes the various defocus amounts, the 
camera can compensate each defocus amount stored in the memory in 
accordance with the amount of movement of the photographic optical system 
to that point, and also can set the final defocus amount from among the 
defocus amounts detected at that time and the compensated defocus amounts. 
The setting device may possess a memory that memorizes the defocus amounts 
in each focus detection region computed by the computation device, and at 
preset times may compensate each defocus amount stored in the memory in 
accordance with the amount of movement of the photographic optical system 
to that point, and also can set the final defocus amount from among the 
compensated defocus amounts. 
The photographic optical system is driven after the defocus amounts of the 
photographic optical system in each focus detection region have been 
detected asynchronously and independently of one another in the multiple 
focus detection regions that are established on the photographic screen of 
the photographic optical system, the defocus amounts in each focus 
detection region have been compensated to the value at the time when the 
defocus amounts in the various detection regions are detected or at preset 
time intervals, and the final defocus amount has been set from among the 
multiple defocus amounts that have been compensated. Through this, it is 
possible to set the final defocus amount in a short time even if there are 
focus detection regions that require long time periods to detect the 
defocus amount, thereby making it possible to improve the responsiveness 
of the focus adjustment. 
The following paragraphs that describe the means and functions used to 
solve the problems discussed above and to explain the structure of the 
present invention use drawings of the embodiments in order to explain the 
present invention in easy to understand terms, but the present invention 
is in no way limited to the embodiments herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
First Embodiment 
FIG. 1 is a drawing showing the structure of the first embodiment. 
The lens 2 is structured so as to be removable from the body 1, and FIG. 1 
shows the state in which the lens 2 is mounted on the body 1. Inside the 
lens 2 is a photographic optical system 3, and light rays from the subject 
passing through the photographic optical system 3 are separated by the 
main mirror 4, which is a half mirror, into rays that go in the direction 
of an auxiliary mirror 5 and in the direction of the viewfinder 6. The 
light rays that are deflected further toward the bottom of the body by the 
auxiliary mirror 5 are guided to a focus detection optical system 7, which 
is provided near the intended focussing surface of the photographic 
optical system 3. 
FIG. 2 shows the structure of the focus detection optical system 7 and the 
electric charge accumulation type sensors 8A and 8B. 
The focus detection optical system 7 is equipped with a field of vision 
mask 71 containing apertures 70A and 70B, a condenser lens 72, a diaphragm 
mask containing a pair of diaphragm apertures 73 and 74, and a pair of 
re-imaging lenses 76 and 77. In addition, the two electric charge 
accumulation type sensors 8A and 8B are each equipped with a pair of light 
receptors 80 and 81, and 82 and 83, respectively. The primary image formed 
at the aperture 70A along the optical axis by the photographic optical 
system 3 is recreated as a pair of secondary images on the light receptors 
80 and 81, and the primary image formed at the aperture 70B is recreated 
as a pair of secondary images on the light receptors 82 and 83. 
FIG. 3 shows the detailed structure of the electric charge accumulation 
type sensor 8A. 
In this figure, the light receptors 80 and 81 are composed of numerous 
pixels, and a light quantity monitor 84 is mounted near the light receptor 
80. In addition, a shift register 85 used in charge output transfer is 
mounted parallel to the light receptors 80 and 81. 
The electric charge accumulation type sensor 8A begins to accumulate 
photoelectrically converted electric charge in the light receptors 80 and 
81 when it receives an electric charge accumulation start signal from the 
outside. Simultaneous with this, the light quantity monitor 84 generates a 
monitor voltage in accordance with the illumination of the light receptor 
80 and the electric charge accumulation time. This monitor voltage is 
output and is compared with a preset standard voltage by the first 
accumulation control circuit 13A, which will be described below. When the 
monitor voltage reaches the standard voltage, the first accumulation 
control circuit 13A generates an electric charge accumulation completion 
signal for the electric charge accumulation type sensor 8A. The electric 
charge accumulation type sensor 8A, upon receiving the electric charge 
accumulation completion signal from the outside, transfers the accumulated 
photoelectrically converted electric charge in the receptors 80 and 81 to 
the shift register 85, following which it serially transfers to the 
outside the electric charge accumulated in each pixel as the sensor output 
following a transfer clock. 
The structure and operation of the electric charge accumulation type sensor 
8B is identical to the structure and operation of the electric charge 
accumulation type sensor 8A, so explanation of such is omitted here. 
In the structure described above, the pair of diaphragm apertures 73 and 74 
are focussed by the condenser lens 72 onto a pair of regions 31 and 32 on 
the surface 30 of the exit pupil of the photographic optical system 3, and 
light that passes through these regions is formed first as a primary image 
in the vicinity of the field of vision mask 71. The primary image formed 
on the apertures 70A and 70B of the field of vision mask 71 passes through 
the condenser lens 72 and the pair of diaphragm apertures 73 and 74, and 
is formed as 2 pairs of secondary images by the pair of re-imaging lenses 
76 and 77 on the light receptors 80 and 81 of electric charge accumulation 
type sensor 8A and on the light receptors 82 and 83 of the electric charge 
accumulation type sensor 8B. 
With this type of structure, the relationship of the relative positions of 
one pair of secondary images changes in accordance with the focus 
condition of the photographic optical system 3. The light intensity 
distribution of the secondary image is converted from light to electricity 
by the light receptors 80, 81, 82 and 83, and becomes a subject image 
signal. 
The electric charge accumulation type sensor 8A shown in FIGS. 2 and 3 
makes up the first sensor 9 shown in FIG. 1, and the electric charge 
accumulation type sensor 8B makes up the second sensor 10. 
In addition, through the focus detection optical system described above, 
the first focus detection region and the second focus detection region are 
established on the photographic screen, as shown in FIG. 4. 
Referring again to FIG. 1, the pair of subject image signals from the first 
sensor 9 and the pair of subject image signals from the second sensor 10 
are sent to the first focus detection computation circuit 12A and the 
second focus detection computation circuit 12B, respectively. By computing 
the relationship between the relative positions of these subject image 
signals, the first focus detection computation circuit 12A and the second 
focus detection computation circuit 12B detect the defocus amount X of the 
intended focus surface and the image surface in the first focus detection 
region of the photographic optical system 3, and the defocus amount Y of 
the intended focus surface and the image surface in the second focus 
detection region. 
However, because the photographic optical system 3 is driven and the image 
surface also moves to this same extent even during electric charge 
accumulation in the first sensor 9 and the second sensor 10 and during the 
defocus amount computation, the amount of driving of the photographic 
optical system during the time between the middle of charge accumulation 
and completion of the computation is converted into a defocus amount, and 
defocus amounts compensated by subtracting from the defocus amounts 
computed at the completion of the computation the defocus amounts 
converted due to driving of the lens are taken as the defocus amounts X 
and Y. In other words, the defocus amounts X and Y indicate the defocus 
amounts upon the completion of defocussing. 
The first sensor 9, the first focus detection computation circuit 12A and 
the first accumulation control circuit 13A make up the first focus 
detection unit 14A, and the second sensor 10, the second focus detection 
computation circuit 12B and the second accumulation control circuit make 
up the second focus detection unit 14B. The first accumulation control 
circuit 13A controls electric charge accumulation in the first sensor 9, 
and the second accumulation control circuit 13B controls electric charge 
accumulation in the second sensor 10. These electric charge accumulation 
controls are performed asynchronously and independently of one another. 
The first focus detection unit 14A and the second focus detection unit 14B 
operate asynchronously and independently of one another and output the 
defocus amounts X and Y to the defocus amount setting part 18. 
The defocus amount setting part 18 is composed of a memory 15, a 
computation circuit 16 and a timer 17, and it sets the final defocus 
amount Z from the defocus amounts X and Y computed by the first focus 
detection computation circuit 12A and the second focus detection 
computation circuit 12B, respectively. The memory 15 reads the lens 
position at the time when the defocus amounts X and Y are generated from a 
position detection circuit 21, which will be explained below, and stores 
these values in pairs with the defocus amounts X and Y. 
The computation circuit either sets the final defocus amount Z based on the 
lens position and defocus amounts-stored in the memory 15 and the 
currently detected lens position and defocus amounts, or sets the final 
defocus amounts based on lens position and defocus amounts stored in the 
memory 15 when the timer 17 sends an interruption signal at a set time 
interval. Detailed explanation of this method of setting the final defocus 
amount will be provided below. 
The final defocus amount Z is sent to the drive control circuit 19 and is 
converted into a lens driving amount. The position detection circuit 21 
computes the lens driving amount by detecting the rotations of the motor 
20 and also computes the lens position by multiplying it with the amount 
of rotation, taking the direction of rotation into consideration. The 
drive control circuit 19 drives the motor 20 to move the photographic 
optical system 3 connected to the motor 20 and also monitors the lens 
driving amount with the position detection circuit 21 and stops the motor 
when the desired lens driving amount is reached. 
Next, the action of the first embodiment explained above will be explained. 
FIG. 5 is a time chart showing the focus detection computation and final 
defocus amount computation based on the electric charge accumulation, 
output transfer and output of the first sensor 9 and the second sensor 10. 
In order to make the explanation easier to understand, FIG. 5 shows the 
case where electric charge accumulation in both the first sensor 9 and the 
second sensor 10 start simultaneously at time T1, with the first sensor 9 
and the second sensor 10 already in operation prior to this time T1 and 
the electric charge accumulation, output transmission, focus detection 
computation and the final defocus amount computations already being 
performed. 
The first sensor 9 has a longer electric charge accumulation time than the 
second sensor 10 because the first sensor 9 captures dim subjects. The 
first sensor 9 completes its electric charge accumulation at time T6, 
performs output transfer and focus detection computations by time T8, and 
generates defocus amount X. After this, from time T8 it repeats the 
operations described above. The second sensor 10 completes its electric 
charge accumulation at time T2, performs output transfer and focus 
detection computations by time T3, and generates defocus amount Y. After 
this, it repeats the operations described above, and successively creates 
the defocus amount Y at times T5 and T9. 
The defocus amount setting part 18 memorizes the defocus amount Y and the 
current lens position at time T3 when the defocus amount Y is generated, 
and also sets the final defocus amount Z based on the defocus amount Y and 
the current lens position as well as on the most recent defocus amount X 
stored in the memory 15 and the lens position at the time when this 
defocus amount X was generated, as shown in the final defocus amount 
computation A in FIG. 5. In addition, it memorizes the defocus amount Y 
and the current lens position when the next defocus amount Y is generated 
at time T5 and sets the final defocus amount Z based on the defocus amount 
Y and the current lens position as well as on the most recent defocus 
amount X stored in the memory 15 and the lens position at the time when 
this defocus amount X was generated. Furthermore, it memorizes the defocus 
amount X and the current lens position when the defocus amount X is 
generated at time T8, and sets the final defocus amount Z based on the 
defocus amount X and the current lens position as well as on the defocus 
amount Y generated at time T5 and stored in the memory and the lens 
position at the time when this defocus amount Y was generated. 
In this way, the first focus detection unit 14A and the second focus 
detection unit 14B operate asynchronously and independently of one 
another, and the final defocus amount Z is updated each time either the 
defocus amount X or the defocus amount Y is generated. In conventional 
automatic focus adjustment cameras, the detection time for the final 
defocus amount Z is limited to the detection time of the focus detection 
sensor having the longer detection time. With the example shown in FIG. 5, 
this would mean detecting the final defocus amount Z at time T8. In 
contrast to this, using the method of final defocus amount computation A 
in the first embodiment, it is possible to make the detection time of the 
final defocus amount Z coincide with the detection time of the focus 
detection sensor with the shorter detection time (here, second sensor 10), 
thereby improving the responsiveness of the focus adjustment. 
It is also acceptable for the operation of detecting the final defocus 
amount Z to be that shown in the final defocus amount computation B in 
FIG. 5. In this case, the computation circuit 16 performs the final 
defocus amount Z computation after receiving an interruption signal from 
the timer 17 at a set time interval W. At time T10 shown in FIG. 5, the 
final defocus amount Z is set based on the current lens position, the 
defocus amount X stored in the memory 15 and the lens position at the time 
this defocus amount X was generated, and the defocus amount Y and the lens 
position at the time this defocus amount Y was generated. Following this, 
this final defocus amount Z computation is repeated after each time 
interval W. 
In this manner, the time interval between generation of the final defocus 
amount Z can be fixed, and it is also possible to create updates of the 
lens driving target each time the final defocus amount Z is generated at 
certain fixed time intervals, thereby improving the stability of control. 
In addition, even when the detection times of the various focus detection 
sensors becomes shorter than is necessary, computation of the final 
defocus amount Z is performed at a set time interval having no 
relationship with the detection time of the focus detection sensors, and 
because of this, the computation circuit 16 can execute other processes 
besides just the computation of the final defocus amount Z. 
FIG. 6 is a time chart showing change in lens position, generation periods 
for the defocus amounts X and Y, and the change with time of the contents 
stored in the memory 15. In this figure, the defocus amount X is called 
the first defocus amount, and the first defocus amount and the lens 
position at the time that this first defocus amount is generated, which 
are both stored in memory, are called the first memorized defocus amount 
and the first memorized lens position. In addition, the defocus amount Y 
is called the second defocus amount, and the second defocus amount and the 
lens position at the time that this second defocus amount is generated, 
which are both stored in memory, are called the second memorized defocus 
amount and the second memorized lens position. 
First, when the defocus amount Ym is generated at lens position Lm, Ym is 
stored in the memory 15 as the second memorized defocus amount, and Lm is 
stored as the second memorized lens position. At this time, the 
computation circuit 16 creates the compensated defocus amount X'n-1 based 
on the first memorized defocus amount Xn-1, the first memorized lens 
position Ln-1, and the current lens position Lm, using the following 
equation. 
EQU X'n-1=(Xn-1)+K.times.{(Ln-1)-Lm} (1) 
Here, K is a coefficient used to convert the lens driving amount into a 
defocus amount. 
Next, the computation circuit 16 computes the final defocus amount Zk by 
averaging the defocus amount Ym and the compensated defocus amount X'n-1, 
using the following equation. 
EQU Zk={(X'n-1)+Ym}/2 (2) 
At this time, it would also be acceptable to set the final defocus amount 
Zk by selecting as the defocus amount the nearer of the compensated 
defocus amount X'n-1 and the defocus amount Ym, as shown in the following 
equation. 
EQU Zk=MAX {(X'n-1), Ym} (3) 
Here, a positive sign on the defocus amount indicates a nearer defocus 
amount. 
When the defocus amount Xn is generated at lens position Ln, Xn is stored 
in the memory 15 as the first memorized defocus amount and Ln is stored as 
the first memorized lens position. At this time, the computation circuit 
16 generates a compensated defocus amount Y'm based on the second 
memorized defocus amount Ym, the second memorized lens position Lm and the 
current lens position Ln, using the following equation. 
EQU Y'm=Ym+K.times.(Lm-Ln) (4) 
Next, the computation circuit 16 computes a final defocus amount Z based on 
the defocus amount Xn and the compensated defocus amount Y'm using either 
equation 5 or equation 6 below. 
EQU Zk+1=(Xn+Y'm)/2 (5) 
EQU Zk+1=MAX (Xn, Y'm) (6) 
The defocus amount setting part 18 repeats the computations described above 
each time the defocus amount X and the defocus amount Y are generated, 
following the method of the final defocus amount computation A shown in 
FIG. 5, thereby producing final defocus amounts Zk+2, Zk+3, Zk+4, Zk+5, 
etc. 
On the other hand, with the method of the final defocus amount computation 
B shown in FIG. 5, the operations of generating the first defocus amount, 
the first memorized defocus amount, the first memorized lens position, the 
second defocus amount, the second memorized defocus amount, and the second 
memorized lens position, and operations up through the updating of the 
memory are the same as with the final defocus amount computation A. The 
computation to find the final defocus amount is not performed at the time 
that the first defocus amount or the second defocus amount is generated, 
but rather with a set periodic timing that is independent of generation of 
the first and second defocus amounts. 
Taking time t in FIG. 6 as the timing of the final defocus amount 
computation in computation method B, when the lens position at that time 
is set as Lt, the compensated defocus amounts X'n and Y'm are computed 
based on the most recent first memorized defocus amount Xn, first 
memorized lens position Ln, second memorized defocus amount Ym, and second 
memorized lens position Lm prior to this time t, using the following 
equations. 
EQU X'n=Xn+K.times.(Ln-Lt) (7) 
EQU Y'm=Ym+K.times.(Lm-Lt) (8) 
Next, the computation circuit 16 computes the final defocus amount Zt based 
on the compensated defocus amounts X'n and Y'm using either equation 9 or 
equation 10 below. 
EQU Zt=(X'n+Y'm)/2 (9) 
EQU Zt=MAX (X'n , Y'm) (10) 
The above operations are repeated with a set periodic timing, thereby 
computing the final defocus amounts Zt+1, Zt+2, etc. 
With the above final defocus amount computation methods A and B, the 
subject is taken to be stationary and only the amount of lens movement 
between the generation of the defocus amount and the computation of the 
compensated defocus amount is compensated; but, taking movement by the 
subject into consideration, it would also be viable to detect the rate of 
change Vx and Vy in the first defocus amount and the second defocus 
amount, respectively, caused by movement by the subject from the previous 
changes in the multiple defocus amounts, and to compute the final defocus 
amount using the following equations 11, 12, 13, and 14 in place of 
equations 1, 4, 7 and 8 respectively. 
EQU X'n-1=(Xn-1)+K.times.{(Ln-1)-Lm}+(Vxn-1).times.{(tn-1)-tm} (11) 
EQU Y'm=Ym+K.times.(Lm-Ln)+Vym.times.(tm-tn) (12) 
EQU X'n=Xn+K.times.(Ln-Lt)+Vxn.times.(tn-t) (13) 
EQU Y'm=Ym+K.times.(Lm-Lt)+Vym.times.(tm-t) (14) 
Here, the times tn-1, tn and tm are times when the defocus amounts Xn-1, Xn 
and Ym were generated, and the defocus amount rates of change Vxn-1, Vxn 
and Vym indicate the rate of change in defocus amount at the time when the 
defocus amounts Xn-1, Xn and Ym were generated. For instance, the first 
defocus amount rate of change Vxn is found using the following equation. 
EQU Vxn=[{Xn-(Xn-1)}+K.times.{Ln-(Ln-1)}]/{tn-(tn-1)} (15) 
FIGS. 7 through 9 are flow charts of the electric charge accumulation 
control and the focus detection computation in the cases where the first 
focus detection unit 14A and the second focus detection unit 14B have been 
equipped with microcomputers and when the defocus amount setting part 18 
has been equipped with a microcomputer. 
The microcomputer in the first focus detection unit 14A begins the 
operations shown in FIG. 7 when a power source is activated in the camera. 
In step S101, the electric charge accumulation operation of the first 
sensor 9 is performed, following which in step S102 the subject image data 
detected by the first sensor 9 is transmitted to the focus detection 
computation circuit 12A. In step S103, the subject image data is processed 
in order to compute the defocus amount X, and in step S104 the defocus 
amount X is output to the defocus amount setting part 18. Following this, 
the microcomputer returns to step S101 and repeats the above process. 
The microcomputer in the second focus detection unit 14B begins the 
operations shown in FIG. 8 when a power source is activated in the camera. 
In step S201, the electric charge accumulation operation of the second 
sensor 10 is performed, following which in step S202 the subject image 
data detected by the first sensor 10 is transmitted to the focus detection 
computation circuit 12B. In step S203, the subject image data is processed 
in order to compute the defocus amount Y, and in step S204 the defocus 
amount Y is output to the defocus amount setting part 18. Following this, 
the microcomputer returns to step S201 and repeats the above process. 
The microcomputer in the defocus amount setting part 18 begins the 
operations shown in FIG. 9 when a power source is activated in the camera. 
In step S301, the determination is made as to whether or not the defocus 
amount X has been received from the first focus detection unit 14A, and if 
the defocus amount X has been received, the microcomputer advances to step 
S302. In step S302, the lens position Lx at the time when the defocus 
amount X was received is read from the position detection circuit 21, and 
this is stored in the memory 15 along with the defocus amount X that has 
been received. In step S303, the compensated defocus amount Y' is computed 
as was described above based on the defocus amount Y and the lens position 
at the time that this defocus amount Y was generated, which are stored in 
the memory 15. In step S304, the final defocus amount Z is set using 
either equation 5 or equation 6 above based on the defocus amount X and 
the compensated defocus amount Y', following which the microcomputer 
advances to step S320 and sends the final defocus amount Z to the drive 
control circuit 19. 
On the other hand, when the defocus amount X has not been received in step 
S301, the microcomputer moves to step S311 and determines whether or not 
the defocus amount Y has been received from the second focus detection 
unit 14B. If the defocus amount Y has been received, the microcomputer 
advances to step S312, and if it has not been received the microcomputer 
returns to step S301. In step S312, the lens position Ly at the time when 
the defocus amount Y was received is read from the position detection 
circuit 21, and this is stored in the memory 15 along with the defocus 
amount Y that has been received. In step S313, the compensated defocus 
amount X' is computed as was described above based on the defocus amount X 
and the lens position at the time that this defocus amount X was 
generated, which are stored in the memory 15. In step S314, the final 
defocus amount Z is set using either equation 5 or equation 6 above based 
on the defocus amount Y and the compensated defocus amount X', following 
which the microcomputer advances to step S320 and sends the final defocus 
amount Z to the drive control circuit 19. 
FIG. 10 is a flow chart of the operations of the defocus amount setting 
part 18 when final defocus amount computation method B is used. From this 
flow chart, the operations of the first embodiment using this final 
defocus amount computation method B will be explained. 
In step S401, the determination is made as to whether or not the defocus 
amount X has been received from the focus detection unit 14A, and if the 
defocus amount X has been received, the microcomputer advances to step 
S402. In step S402, the lens position Lx at the time when the defocus 
amount X was generated is read from the position detection circuit 21, the 
defocus amount X and this lens position Lx are stored in the memory 15, 
and the microcomputer returns to step S401. 
On the other hand, when the defocus amount X has not been received in step 
S401, the microcomputer moves to step S411 and determines whether or not 
the defocus amount Y has been received. If the defocus amount Y has been 
received, the microcomputer advances to step S412, and if it has not been 
received, the microcomputer returns to step S401. In step S412, the lens 
position Ly at the time when the defocus amount Y was generated is read 
from the position detection circuit 21, the defocus amount Y and this lens 
position Ly are stored in the memory 15, and the microcomputer returns to 
step S401. 
FIG. 11 is a flow chart showing the timer interruption operation of the 
defocus setting part 18. 
The timer 17 performs the timer interruption operation shown in FIG. 11 on 
the microcomputer in the defocus amount setting part 18 with a set 
frequency. When the timer interruption operation is initiated, the 
compensated defocus amounts X' and Y' are found in step S501 using 
equations 7 and 8 above based on the defocus amounts X and Y and the lens 
positions Lx and Ly, which are all stored in the memory 15, and on the 
current lens position. Then, in step S502, the final defocus amount Z is 
set using either equation 9 or equation 10 above based on the compensated 
defocus amounts X' and Y'. In step S503, the final defocus amount Z is 
sent to the drive control circuit 19, and the interruption operation is 
completed. 
Second Embodiment 
With the first embodiment, which has been explained above, the first sensor 
9 and the second sensor 10 send subject image signals to separate 
microcomputers, and the focus detection computation is performed by 
converting the signals from these sensors to digital signals using A/D 
converters mounted inside each of the microcomputers. This arrangement 
requires two microcomputers equipped with A/D converters. A second 
embodiment will now be described, wherein the first sensor 9 and the 
second sensor 10 send subject image signals to a single microcomputer, 
where the focus detection computation is performed by converting these 
signals into digital signals using an A/D converter. 
FIG. 12 shows the structure of the second embodiment. In FIG. 12, elements 
identical to elements shown in FIG. 1 are marked with the identical 
symbols, and the following explanation focusses on the differing items. 
In this second embodiment, a first temporary retention circuit 22A and a 
second temporary retention circuit 22B are provided in order to 
temporarily retain the electric charge accumulated by the first sensor 9 
and the second sensor 10, respectively. The electric charge accumulated in 
the first sensor 9 is transmitted to the first temporary retention circuit 
22A when accumulation has been completed. Similarly, the electric charge 
accumulated in the second sensor 10 is transmitted to the second temporary 
retention circuit 22B when accumulation has been completed. The output of 
the first temporary retention circuit 22A and the second temporary 
retention circuit 22B is combined into one unit, which is linked to the 
focus detection computation circuit 12. The subject image signals from the 
temporary retention circuits 22A and 22B are transferred to the focus 
detection computation circuit 12. The input control circuit 23 provides 
control so that transmission of the subject image signals from the first 
temporary retention circuit 22A and from the second temporary retention 
circuit 22B do not conflict with each other with respect to time of 
transmission. 
FIG. 13 shows the structure of the focus detection optical system 7 and the 
electric charge accumulation type sensor 8 used in the second embodiment. 
The focus detection optical system 7 is equipped with a field of vision 
mask 71 having apertures 70A and 70B; condenser lenses 72A and 72B; a 
diaphragm mask 75 containing two pairs of diaphragm apertures 73A, 74A, 
73B and 74B; and two pairs of re-imaging lenses 76A, 77A, 76B and 77B. In 
addition, the electric charge accumulation type sensor is equipped with 
two pairs of light receptors 80, 81, 82 and 83. 
The primary image formed by the photographic optical system 3 on the 
aperture 70A along the optical axis is recreated as a pair of secondary 
images on the light receptors 80 and 81, and the primary image formed on 
the aperture 70B is recreated as a pair of secondary images on the light 
receptors 82 and 83. 
With the structure described above, the two pairs of diaphragm apertures 
73A, 74A, 73B and 74B are projected by the condenser lenses 72A and 72B 
onto a pair of regions 31 and 32 on the surface 30 of the exit pupil of 
the photographic optical system 3, and light that passes through these 
regions is formed first as a primary image in the vicinity of the field of 
vision mask 71. The primary image formed on the apertures 70A and 70B of 
the field of vision mask 71 passes through the condenser lenses 72A and 
72B and the two pairs of diaphragm apertures 73A, 74A, 73B and 74B and is 
formed as 2 pairs of secondary images by the pair of re-imaging lenses 
76A, 77A, 76B and 77B on the light receptors 80, 81 82 and 83 of electric 
charge accumulation type sensor 8. 
FIG. 14 shows the detailed structure of the electric charge accumulation 
type sensor 8, which is comprised of a single chip. Light receptors 80, 
81, 82 and 83 are each composed of numerous pixels, and light quantity 
monitors 84A and 84B are mounted near light receptors 80 and 82 
respectively. In addition, electric charge memories 86A, 87A, 86B and 87B 
are mounted parallel to the light receptors 80, 81, 82 and 83 in order to 
temporarily retain the electric charge accumulated in each light receptor, 
and shift registers 85A and 85B used in charge output transfer are mounted 
parallel to the electric charge memories 86A, 87A, 86B and 87B. 
Light receptors 80 and 81 and light receptors 82 and 83 can be controlled 
so that the start and completion of charge accumulation is asynchronous 
and independent of one another, and each one starts accumulating charge 
upon receiving an electric charge accumulation start signal. Simultaneous 
with this, the light quantity monitors 84A and 84B generate monitor 
voltages in accordance with the illumination of the light receptors and 
the electric charge accumulation time. The monitor voltage output from the 
light quantity monitor 84A is compared with a preset standard voltage by 
the first accumulation control circuit 13A, and when the monitor voltage 
reaches the standard voltage, the first accumulation control circuit 13A 
generates an electric charge accumulation completion signal for light 
receptors 80 and 81. Similarly, the monitor voltage output from the light 
quantity monitor 84B is compared with a preset standard voltage by the 
second accumulation control circuit 13B, and when the monitor voltage 
reaches the standard voltage, the second accumulation control circuit 13B 
generates an electric charge accumulation completion signal for light 
receptors 82 and 83. Upon receiving the electric charge accumulation 
completion signal, the light receptors 80 and 81 transfer the electric 
charge they have accumulated to the electric charge memories 86A and 87A. 
In addition, upon receiving the electric charge accumulation completion 
signal, the light receptors 82 and 83 transfer the electric charge they 
have accumulated to the electric charge memories 86B and 87B. 
Electric charge memories 86A and 87A transfer the accumulated charge in 
parallel to the shift register 85A following control commands from the 
input control circuit 23, following which the electric charge accumulated 
in each pixel is transferred serially to the outside as the sensor output 
following the timing of a transfer clock. Similarly, electric charge 
memories 86B and 87B transfer the accumulated charge in parallel to the 
shift register 85B following control commands from the input control 
circuit 23, following which the electric charge accumulated in each pixel 
is transferred serially to the outside as the sensor output following the 
timing of a transfer clock. The output of the shift registers 85A and 85B 
are combined together and are output out of the single chip electric 
charge accumulation type sensor 8. 
It would also be acceptable have the first accumulation control circuit 13A 
and the second accumulation control circuit 13B formed on the single chip 
electric charge accumulation type sensor 8. 
In this way, with the structure shown in FIGS. 13 and 14, the relationship 
of the relative positions of the pair of secondary images changes in 
accordance with the focus state of the photographic optical system 3. The 
light intensity distribution of the secondary images is photoelectrically 
converted by the light receptors 80, 81, 82 and 83 and becomes an 
electrical subject image signal. 
Light receptors 80 and 81 of the electric charge accumulation type sensor 
8, light quantity monitor 84A, electric charge memories 86A and 87A, and 
shift register 85A, which are shown in FIGS. 13 and 14, make up the first 
sensor 9 shown in FIG. 12, while light receptors 82 and 83 of the electric 
charge accumulation type sensor 8, light quantity monitor 84B, electric 
charge memories 86B and 87B, and shift register 85B make up the second 
sensor 10 shown in FIG. 12. 
Referring again to FIG. 12, the pair of subject image signals from the 
first sensor 9 and the pair of subject image signals from the second 
sensor 10 are sent to the focus detection computation circuit 12. The 
focus detection computation circuit 12, by computing the relationship of 
the relative positions of these subject image signals, detects the defocus 
amount X of the intended focussing surface and the image surface in the 
first focus detection region of the photographic optical system 3 and the 
defocus amount Y of the intended focussing surface and the image surface 
in the second focus detection region. 
FIG. 15 is a time chart showing the electric charge accumulation operation 
and the output transfer operation of the first sensor 9 and the second 
sensor 10, and the operation of computing the defocus amounts X and Y from 
the output of the two sensors. In order to make the explanation easier to 
understand, FIG. 15 shows the case in which electric charge accumulation 
in both the first sensor 9 and the second sensor 10 starts simultaneously 
at time T1, but the first sensor 9 and the second sensor 10 are already in 
operation prior to this time T1, and electric charge accumulation, output 
transfer, focus detection computations and final defocus amount 
computations have already been performed. 
Because the first sensor 9 captures dim subjects, it has a longer electric 
charge accumulation time than does the second sensor 10. The operations 
through time T6 are basically the same as those shown in FIG. 5. However, 
in FIG. 15, the transfer operation and the computation operation of the 
second sensor 10 are shown separately. Until time T6, the output transfer 
operations of the first sensor 9 and the second sensor 10 are not 
performed simultaneously. 
At time T6, the electric charge accumulation in the first sensor 9 is 
completed, and when the accumulated charge is transferred to the first 
temporary retention circuit 22A, because the accumulated charge of the 
second sensor 10 is being transferred to the focus detection computation 
circuit 12 from the second temporary retention circuit 22B, transferring 
of the accumulated charge of the first sensor 9 from the first temporary 
retention circuit 22A to the focus detection computation circuit 12 is 
prevented by the input control circuit 23. At time T7, when the transfer 
of charge from the second temporary retention circuit 22B to the focus 
detection computation circuit 12 is complete, the input control circuit 23 
allows charge to be transferred from the first temporary retention circuit 
22A to the focus detection computation circuit 12, and from time T7 the 
accumulated charge of the first sensor 9 is transferred from the first 
temporary retention circuit 22A to the focus detection computation circuit 
12. 
At time T8, when the transfer of charge from the first temporary retention 
circuit 22A to the focus detection computation circuit 12 is complete, 
computation of the defocus amount Y by the focus detection computation 
circuit 12 is started based on the subject image signal from the second 
sensor 10. At time T9, when computation of the defocus amount Y has been 
completed, electric charge accumulation is started in the second sensor 10 
and computation of the defocus amount X by the focus detection computation 
circuit 12 is started based on the subject image signal from the first 
sensor 9. Furthermore, at time T10, when computation of the defocus amount 
X has been completed, electric charge accumulation is started in the first 
sensor 9. Following this, the same operations are repeated. 
When the transfer of charge from the first temporary retention circuit 22A 
to the focus detection computation circuit 12 and the transfer of charge 
from the second temporary retention circuit 22B to the focus detection 
computation circuit 12 are in conflict with respect to time of 
transmission, the input control circuit 23 gives priority to the charge 
transfer that was started first, and prevents the second charge transfer 
from occurring until the first charge transfer has been completed. 
Computation of the defocus amount Z is performed at the time when either 
the defocus amount X or Y is generated (times T4, T9 and T10 in FIG. 15) 
in an operation similar to that shown in FIG. 5. 
FIGS. 16 through 20 are flow charts that show the operations of the second 
embodiment when the first accumulation control circuit 13A, the second 
accumulation control circuit 13B, and the input control circuit 23 are 
comprised of two auxiliary microcomputers, the focus detection computation 
circuit 12 is comprised of a separate auxiliary microcomputer, and the 
defocus amount setting part 18 is comprised of the main microcomputer. 
FIG. 16 is a flow chart that shows the operations of the auxiliary 
microcomputer that comprises the first accumulation control circuit 13A 
and the input control circuit 23. 
The microcomputer starts the operations shown in FIG. 16 when a power 
source is activated in the camera. In step S601, charge accumulation is 
performed in the first sensor 9, following which in step S602, the focus 
detection signal from the first sensor 9 is transmitted to the first 
temporary retention circuit 22A. 
In step S603, the determination is made as to whether or not the focus 
detection signal of the second sensor 10 is being transferred from the 
second temporary retention circuit 22B to the focus detection computation 
circuit 12, and if this transfer is in progress, the microcomputer pauses 
until it has been completed. When the transfer of the focus detection 
signal of the second sensor 10 has been completed, the microcomputer 
advances to step S604 and transfers the focus detection signal of the 
first sensor 9 from the first temporary retention circuit 22A to the focus 
detection computation circuit 12. In step S605, the determination is made 
as to whether or not computation of the defocus amount X has been 
completed, and if the computation has been completed the microcomputer 
returns to step S601 and repeats the operations described above. 
FIG. 17 is a flow chart that shows the operations of the auxiliary 
microcomputer that comprises the second accumulation control circuit 13B 
and the input control circuit 23. 
The microcomputer starts the operations shown in FIG. 17 when a power 
source is activated in the camera. In step S701, charge accumulation is 
performed in the second sensor 10, following which in step S702, the focus 
detection signal from the second sensor 10 is transferred to the second 
temporary retention circuit 22B. In step S703, the determination is made 
as to whether or not the focus detection signal of the first sensor 9 is 
being transferred from the first temporary retention circuit 22A to the 
focus detection computation circuit 12, and if this transfer is in 
progress, the microcomputer pauses until it has been completed. When the 
transfer of the focus detection signal of the first sensor 9 has been 
completed, the microcomputer advances to step S704 and transfers the focus 
detection signal of the second sensor 10 from the second temporary 
retention circuit 22B to the focus detection computation circuit 12. In 
step S705, the determination is made as to whether or not computation of 
the defocus amount Y has been completed, and if the computation has been 
completed, the microcomputer returns to step S701 and repeats the 
operations described above. 
FIGS. 18 and 19 are flow charts that show the interruption operations of 
the focus detection computation circuit 12. 
The auxiliary microcomputer of the focus detection computation circuit 12 
starts the interruption operation shown in FIG. 18 when an interruption 
signal is input from the auxiliary microcomputer that comprises the first 
accumulation control circuit 13A and the input control circuit 23. In step 
S801, the subject image signal of the first sensor 9 is read from the 
first temporary retention circuit 22A, following which in step S802, 
computation flag 1 is set and the interruption process is completed. 
In addition, the auxiliary microcomputer of the focus detection computation 
circuit 12 starts the interruption operation shown in FIG. 19 when an 
interruption signal is input from the auxiliary microcomputer that 
comprises the second accumulation control circuit 13B and the input 
control circuit 23. In step S811, the subject image signal of the second 
sensor 10 is read from the second temporary retention circuit 22B, 
following which in step S812, computation flag 2 is set and the 
interruption process is completed. 
FIG. 20 is a flow chart that shows the computation process of the focus 
detection computation circuit 12. 
The microcomputer of the focus detection computation circuit 12 starts the 
operations shown in FIG. 20 when a power source is activated in the 
camera. In step S901, the determination is made as to whether or not 
computation flag 1 has been set. If it has been set the microcomputer 
advances to step S902, and if it has not been set, the microcomputer moves 
to step S911. In step S902, the defocus amount X is computed based on the 
focus detection signal of the first sensor 9 read from the first temporary 
retention circuit 22A. In step S903, the defocus amount X is transmitted 
to the defocus amount setting part 18, following which the computation 
flag 1 is reset in step S904, and the microcomputer then returns to step 
S901. 
On the other hand, in step S911 the determination is made as to whether or 
not computation flag 2 has been set. If it has been set, the microcomputer 
advances to step S912, and if it has not been set, the microcomputer 
returns to step S901. In step S912, the defocus amount Y is computed based 
on the focus detection signal of the second sensor 10 read from the second 
temporary retention circuit 22B. In step S913, the defocus amount Y is 
transmitted to the defocus amount setting part 18, following which the 
computation flag 2 is reset in step S914 and the microcomputer then 
returns to step S901. 
With the second embodiment as described above, the first accumulation 
control circuit 13A, the second accumulation control circuit 13B, and the 
input control circuit 23 are comprised of two auxiliary microcomputers, 
the focus detection computation circuit 12 is comprised of a separate 
auxiliary microcomputer, and the defocus amount setting part 18 is 
comprised of the main microcomputer, but it would also be viable for the 
operations shown in FIGS. 16 and 17 to be processed by interruption by the 
microcomputer of the focus detection computation circuit 12. Even in this 
case, the input terminals of the focus detection computation circuit 12 
from the first sensor 9 and the second sensor 10 are a single unit, and 
computation of the defocus amounts are all performed by the microcomputer 
of the focus detection computation circuit 12, and because of this, there 
is no decrease in focus detection computation speed. 
In addition, it would also be viable for the operations shown in FIGS. 16 
through 20 to be processed by the main microcomputer of the defocus amount 
setting part 18. 
In each of the embodiments described above, examples were given using two 
sensors, but the present invention can also be applied to cases where 
three or more sensors are used. 
In the structure of the embodiments explained above, the photographic 
optical system 3 comprises the photographic optical system, the focus 
detection units 14A and 14b comprise the focus detection means, the 
defocus amount setting part 18 comprises the setting means, the drive 
control circuit 19 and the motor 20 comprise the drive means, the focus 
detection optical system 7 comprises the focus detection optical system, 
the first sensor 9 and the second sensor 10 comprise the sensors, the 
first focus detection computation circuit 12A and the second focus 
detection computation circuit 12B comprise the computation circuit, the 
first accumulation control circuit 13A and the second accumulation control 
circuit 13B comprise the accumulation control means, the memory 15 
comprises the memory means, the focus detection computation circuit 12 
comprises the computation means, the first temporary retention circuit 22A 
and the second temporary retention circuit 22B comprise the temporary 
retention means, and the input control circuit 23 comprises the input 
control means. 
With the present invention as explained above, in numerous focus detection 
regions established on the photographic screen of the photographic optical 
system, defocus amounts of the photographic optical system are detected 
asynchronously and independently of one another in each of the focus 
detection regions, and when the defocus amounts are detected in the 
various focus detection regions or at preset time intervals, the value of 
the defocus amounts in each of the focus detection regions at that time is 
compensated and the final defocus amount is set from among these numerous 
compensated defocus amounts in order to drive the photographic optical 
system. Because of this, even when there are regions that require a long 
period of time in order to compensate the defocus amount for a subject on 
the photographic screen having a large variance in brightness, the final 
defocus amount can be set in a short time, thereby realizing improved 
responsiveness in the focus adjustment. 
While this invention has been described in conjunction with specific 
embodiments thereof, it is evident that many alternatives, modifications 
and variations will be apparent to those skilled in the art. Accordingly, 
the preferred embodiments of the invention as set forth herein are 
intended to be illustrative, not limiting. Various changes may be made 
without departing from the spirit and scope of the invention as defined in 
the following claims.