Blurring motion detection device

A blurring motion detection device and method to determine an improved blurring motion zero reference value. The device includes a storage unit to store averaged blurring motion data based on an average of successive blurring motion data, with new blurring motion data being more recent in time than old blurring motion data. A selection unit filters out anomalous blurring motion data by selecting the blurring motion data within a deviation range from an average of the stored blurring motion data. The deviation range may include a first deviation range for the old blurring data which is set to be smaller than a second deviation range for the new blurring motion data. The deviation range may also be defined by a decision function which gradually widens the deviation range for the new blurring motion data. A calculation unit calculates the blurring motion zero reference value based on the blurring motion data within the deviation range. The calculation of the average of the successive blurring motion data and the blurring motion zero reference value may use weighted blurring motion data in which the new blurring motion data has a greater weight than the old blurring motion data.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is related to blur detection. More specifically, the present 
invention is related to a blurring motion detection device to detect 
blurring motions, such as from hand movements, on a camera and the like. 
2. Description of the Related Art 
Detection of blurring motion acting on a camera and compensation for image 
blur based on the detected blurring motion is well known in the industry. 
Methods well known in the industry are also used to increase the output 
accuracy of blur detection sensors as a type of drift countermeasure. An 
example of such methods includes Japanese Laid-Open Patent Publication 
number JP-A-4-211230, in which the average value of output values of the 
blurring motion detection sensors is calculated in a predetermined time. 
The average value is taken as a standard value (a blurring motion zero 
reference value) of the output of the blurring motion detection sensor. 
However, the following problems existed in the aforementioned conventional 
technology. 
When an average value is to be calculated from the output of a blurring 
motion detection sensor, the data to be collected to calculate the average 
value should preferable be free from irregular blurring motions acting on 
the camera. However, in photography of a stationary subject, photographic 
preparations may include changing the photographic field angle after 
framing is performed during manipulation of the composition of the 
photograph. Such movement of the camera may occur particularly in 
autofocus (AF) cameras after focusing is performed on the main subject to 
reframe the desired composition of the photograph where the main subject 
is no longer in the picture center. An output value of a blurring motion 
detection sensor during such movement of the camera will reflect an 
undesirably large offset or alteration movement. Accordingly, if the 
output value during such movement is used in calculating the average 
value, a standard value of high reliability cannot be obtained. 
Moreover, if the data collected from the blur detection sensor for use in 
determining an average value becomes too old (i.e., data from a time in 
the past that is distant from the time of photography), then the data 
collected will not reflect conditions near the time photographic 
preparations end. Thus, when using such old data to calculate an average 
value, the true standard value at the time of photography cannot be 
obtained and a displacement occurs. 
In addition, because the amount of movement during a panning motion is 
different from the amount of movement occurring at the commencement of the 
panning motion, a blurring motion zero reference value calculated from 
data collected during the panning motion commencement and panning motion 
execution is disadvantageous. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to calculate a more 
accurate and reliable blurring motion zero reference value in blurring 
motion detection. 
It is a further object of the present invention to achieve a more efficient 
processing load on the blurring motion detection device of the present 
invention. 
It is yet another object of the present invention to filter out anomalous 
blurring motion data in determining the blurring motion zero reference 
value. 
It is a further object of the present invention to calculate a more 
accurate and reliable blurring motion zero reference value with a blurring 
motion detection device of simple construction. 
Objects of the present invention are achieved by providing a blurring 
motion detection device and method to determine an improved blurring 
motion zero reference value. The device includes a storage unit to store 
averaged blurring motion data based on an average of successive blurring 
motion data, with new blurring motion data being more recent in time than 
old blurring motion data. The average of the successive blurring motion 
data may be calculated from weighted blurring motion data in which the new 
blurring motion data has a greater weight than the old blurring motion 
data. A selection unit filters out anomalous blurring motion data by 
selecting the blurring motion data within a deviation range from an 
average of the blurring motion data. 
Objects of the present invention are also achieved by providing a blurring 
motion detection device using a first deviation range for old blurring 
motion data and a second deviation range for new blurring motion data. The 
second deviation range is set to be larger than the first deviation range. 
The deviation range may also be defined by a decision function which 
gradually widens the deviation range for the new blurring motion data. 
Objects of the present invention are further achieved by providing blurring 
motion detection device having a calculation unit to calculate the 
blurring motion zero reference value based on the blurring motion data 
within the deviation range. The calculation of the blurring motion zero 
reference value may also use weighted blurring motion data in which the 
new blurring motion data has a greater weight than the old blurring motion 
data.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Reference will now be made in detail to the present preferred embodiments 
of the present invention, examples of which are illustrated in the 
accompanying drawings, wherein like reference numerals refer to like 
elements throughout. 
FIG. 1 shows a preferred embodiment of a blurring motion detection device 
according to the present invention incorporated within a camera. FIG. 2 is 
a block diagram showing the relationship and connections between 
components of the camera depicted in FIG. 1. 
The blurring motion detection sensor 1 is a sensor that detects hand 
movements and similar blurring motions acting on the camera. The blurring 
motion detection sensor 1 outputs analog data corresponding to the angular 
velocity of the blurring motion of the camera. An example of the blurring 
motion detection sensor 1 includes, but is not limited to, a piezoelectric 
vibration gyro angular velocity sensor. 
An A/D converter 2 converts the analog data outputted from the blurring 
motion detection sensor 1 to digital data. A dedicated IC may be used as 
the A/D converter 2, but one such as the A/D port of a microcomputer 
constituting the camera control unit 5 (described below) may also be used. 
A focus detection sensor 3 detects the imaging state of the photographic 
optical system. The focus detection sensor 3 outputs analog data of 
picture signals (video signals) from a CCD solid state imaging circuit. An 
example of a focus detection sensor 3 includes, but is not limited to, a 
divided pupil type of TTL focus detection sensor. 
An A/D converter 4 converts the analog data outputted from the focus 
detection sensor 3 to digital data. As with the A/D converter 2, the A/D 
port of a microcomputer may be employed as the A/D converter 4. 
Alternatively, the A/D converter 2 may also be employed as the A/D 
converter 4 when the A/D converter 2 is used in a time sharing mode in a 
multiplexer circuit. 
The camera control unit 5 may be a microcomputer and the like for 
controlling the operations of the whole camera. The camera control unit 5 
has a calculating unit 5a and a memory unit 5b. The calculating unit 5a 
calculates digital data. The memory unit 5b stores digital data. An 
example of the calculating unit 5a includes, but is not limited to, the 
CPU circuit of a microcomputer employed as the camera control unit 5. An 
example of the memory unit 5b includes, but is not limited to, RAM, 
EEPROM, or flash memory circuits built into or external to the 
microcomputer. 
In the present preferred embodiment, the photographic optical system 8 is a 
blurring motion compensation optical system. A drive method of the 
photographic optical system 8 includes, but is not limited to, (1) a 
method of causing the photographic optical system 8 to move by the 
rotation of a feed screw by means of a rotary motor, (2) a method of 
causing linear motion by means of a voice coil and a magnetoelectric 
circuit, and (3) a method of shift driving which uses a linear motor and 
the like. This preferred embodiment adopts a method which shifts the whole 
optical system and the blurring motion compensation drive unit 6 shift 
drives the photographic optical system 8 to effect blurring motion 
compensation. In FIG. 1, only a shift in the vertical direction of the 
camera (Y direction) is shown, but driving may also be performed in the 
camera's horizontal direction (X axis). 
In addition, blurring motion compensation may further include other methods 
to cause the driving of the photographic optical system 8 or a portion of 
the optical system. Such further methods may include, for example, (1) use 
of a variable angle prism, (2) shifting an imaging unit (e.g., 
photographic film), and (3) adjusting the mounting angle of a reflecting 
mirror located in the photographic optical path. 
The focusing drive unit 7 moves the photographic optical system 8 in the 
optical axis direction to effect focusing on the imaging surface. In the 
present preferred embodiment, the whole photographic optical system 8 is 
caused to move during focusing by the focusing drive unit 7, but movement 
of only a portion of the optical system is also possible. 
The release switch 9 includes a half depression switch 9a and a full 
depression switch 9b. The release switch 9 is electrically connected to 
the camera control unit 5. When the release switch 9 is set ON/OFF, a 
signal is transmitted to the camera control unit 5. 
FIG. 3 is a flow chart illustrating an operation of the camera of FIG. 1. 
This camera has a so-called one-shot AF mode in which the exposure does 
not commence if the photographic optical system 8 does not focus. In the 
following description of FIG. 3, the processing at each step is performed 
by the camera control unit 5 unless otherwise stated. 
The flow chart of FIG. 3 starts at step S100 in which the half depression 
switch 9a becomes ON, the camera power supply becomes ON, etc. In S110, 
the full depression switch 9b is checked for being ON. If the full 
depression switch 9b is not ON, processing proceeds to step S120. If the 
full depression switch 9b is ON, processing proceeds to step S140. 
In step S120, the data of the blurring motion detection sensor 1, obtained 
through the A/D converter 2, is read out. In step S130, the data obtained 
in step S120 is stored in the memory unit 5. Successively obtained data is 
stored until the storage capacity of the memory unit 5 is reached. On 
reaching the memory capacity limit (for example, NL data), the oldest data 
is erased, and is replaced by the newest data. 
To effect savings in the memory capacity of the memory unit 5b, the 
successively obtained data may be modified for storage between steps S120 
and S130. For example, if 8 items of data are temporarily stored, an 
average of the data may be calculated by the calculating unit 5a and this 
single average value may be stored in the memory unit 5b instead of eight 
data values. If blurring motion data is inputted each 1 msec, the average 
value of 8 items of data may be stored. The stored average value would 
represent 8 msec of data. Because the frequency of hand movements on the 
camera is at a comparatively low frequency, sampling of the data may be at 
about 8 to 16 msec intervals of time. Accordingly, an average value of 8 
data values sampled at 8 to 16 msec intervals may be calculated and 
stored. Such an average value would represent 64-128 msec of data. 
Moreover, the average may be of 16 or 32 items of data, not just of 8 
items. Thus, this compressed form of data storage allows data over a 
longer period of time to be stored in a comparatively smaller amount of 
memory capacity. 
When the full depression switch 9b is on, processing proceeds to step S140. 
Step S140 and the steps following step S140 are related to an exposure 
operation. 
In step S140, the camera blurring motion data which had been stored in the 
memory unit 5b are read out. Then, in the next step S150, a first 
calculation is performed by the calculating unit 5a based on the data 
which were read out in step S140. FIG. 4 illustrates the data stored in 
the memory unit 5b which is read out. In FIG. 4, the number of data stored 
in the memory unit 5b is the 10 newest items (D1-D10, D10 being the 
newest), and old data previous to this is erased. The first calculation of 
step S150 performs a calculation of an overall average or an arithmetic 
mean of all the data D1-D10. The value obtained here becomes the first 
standard value V0'. 
Next, in step S160, the calculating unit 5a compares the first standard 
value V0' found in step S150 with each data Dn. This comparison determines 
whether a particular data Dn should be used in a second calculation for an 
improved standard value or a blurring motion zero reference value. The 
objective in deciding whether to use a particular data Dn is to remove any 
data Dn which is anomalous with respect to the first standard value V0'. 
By such determinations, data Dn which deviates to a certain extent from the 
standard value V0' will not be used in the second calculation. The 
exclusion of selected data Dn addresses the problem that certain data may 
reflect blurring motion data that is significantly different from the 
blurring motion data near the time of photography. "New" data Dn generated 
near the end of photographic preparations (e.g., D6-D10) are less prone to 
reflect anomalous blurring motions. But, there is a high possibility that 
"old" data (e.g., D1-D5), reflecting blurring motion more distant in time 
from the photographic preparation end state, would include unwanted 
blurring motion associated with the photographer's reframing of the camera 
or other picture composition manipulations. Instead of haphazard 
discarding of old data from the second calculation (which may lead to 
decreased reliability of the resulting standard value), the selection 
process for the second calculation according to the present invention 
identifies only the useful data Dn and bolsters the reliability and 
accuracy of the standard value calculated by the second calculation. 
First, the absolute value of the deviation of each data Dn from the 
standard value V0' is calculated. The absolute value results R1-R10 are 
then compared with decision values S(old) and S(new), discussed in further 
detail below. Absolute value deviations R1-R5 are compared with decision 
value S(old). Absolute value deviations R6-R10 are compared with decision 
value S(new). Data Dn having an Rn&gt;S(old) (for n=1-5) or Rn&gt;S(new) (for 
n=6-10) are not used in the second calculation for the improved standard 
value V0 or blurring motion zero reference value. Expressed in another 
way, data Dn retained for the second calculation for n=1-5 must fall 
within a first deviation range of (V0'-S(old)) 
.ltoreq.Dn.ltoreq.(V0'+S(old)). Data Dn retained for the second 
calculation for n =6-10 must fall within a second deviation range of 
(V0'-S(new)).ltoreq.Dn.ltoreq.(V0'+S(new)). Data Dn not present in these 
ranges are not used. 
The decision values are either S(old).ltoreq.S(new), or S(old)&lt;S(new). This 
relationship reflects the expectation that the old data are more likely to 
incorporate anomalous data than the new data, as discussed above. The 
decision values S(old) and S(new) may be predetermined values placed in 
the memory unit 5b at the time of manufacture of the camera--the 
predetermined values being found by previous experiment. The memory unit 
5b which stores these decision values may be non-volatile, such as mask 
ROM or EEPROM. 
The decision values S(old) and S(new) may also be determined by 
predetermined relationships with the data D1-D10 or the deviations R1-R10. 
For example, the maximum value of the deviations R1-R10.times.(1/2) may be 
taken as the decision value S(old), and the maximum value of the 
deviations R1-R10.times.(3/4) may be taken as the decision value S(new). 
Moreover, the decision values S(old) and S(new) may be calculated each time 
R1-R10 is calculated. For example, among values on both sides, the method 
is to use the smaller value or the larger value. 
Of course, the present invention is not limited to using 10 data items for 
determining the blurring motion standard value--other quantities of data 
items may be used. Moreover, a limitation may be established as to the 
number of data items that may be removed from the second calculation. For 
example, a limitation may be used for excluding only up to a maximum of 3 
data items that are compared to S(old). Another limitation may be used for 
excluding only up to a maximum of 2 data items that are compared to 
S(new). Again, this allowance for removing more old data than new data 
reflects the expectation that the old data are more likely to incorporate 
anomalous data than the new data, as discussed above. 
In step S170, the calculation unit 5a calculates the average (arithmetic 
mean) using the data items which were retained in step S160. In the 
example of FIG. 4, among the data D1-D10, the average is calculated using 
data other than D2 and D3. This average becomes the second standard value 
V0 or the blurring motion zero reference value. 
In step S180, drive control signals are output to the image blurring motion 
compensation drive unit 6, causing image blurring motion compensation 
driving to commence. Similar to step S120, data (VS) from the blurring 
motion detection sensor 1 is obtained through the serial A/D converter 2. 
The true blurring motion data of the camera is calculated by the 
calculating unit 5a from the difference between VS and the blurring motion 
zero reference value (standard value V0) obtained in step S170 (i.e., 
VS-V0). Calculation of an appropriate compensation drive amount by the 
calculating unit 5a is based on this true blurring motion data (VS-V0). A 
drive control signal of the image blurring motion compensation is output 
by the camera control unit 5 to the image blurring motion compensation 
drive unit 6. Image blurring motion compensation driving continues until 
processing reaches step S210. 
Continuing in step S190, a drive control signal is output to the shutter 
unit (not shown in the drawing) of the camera, causing the exposure 
operation to commence. In step S200, when the exposure time, a 
predetermined time commenced by step S190, has elapsed, a signal is output 
to the shutter unit to end the exposure operation. Next, in step S210, a 
signal is output from the camera control unit 5 to the image blurring 
motion compensation drive compensation unit 6 to end image blurring motion 
compensation driving. 
The present invention is not limited to the blurring motion detection 
device of the above embodiment. For example, the method of setting the 
deviation ranges and calculating the standard values may be effectively 
changed and modified in the further preferred embodiments described below. 
A second preferred embodiment of the blurring motion detection device of 
the present invention, in comparison with the first preferred embodiment, 
only differs in the selection method of the data Dn in order to calculate 
the blurring motion zero reference value (standard value V0). 
In the first preferred embodiment, the decision values S(old) and S(new) 
were used. In this second preferred embodiment, a decision function fS(n) 
is used to set a varying deviation range used in filtering out anomalous 
data items. The varying deviation range set by the decision function fS(n) 
varies gradually and favors the new blurring motion data items by widening 
the deviation range for newer blurring motion data. The decision function 
fS(n) includes, for example: 
EQU fS1(n)=S(c).times..alpha..sup.(n-1) ; constants: S(c)&gt;0, .alpha.&gt;1;(1) 
EQU fS2(n)=S(c)+(.beta..times.(n-1)); constants: S(c)&gt;0, .beta..gtoreq.0; and(2 
) 
EQU fS3(n)=S(c)+(.delta..times..gamma..sup.(n-1)); constants: S(c)&gt;0, 
.delta..gtoreq.0, .gamma.0. ((3) 
FIG. 5 is a graph illustrating a sample data distribution, standard values, 
and a deviation range according to this second preferred embodiment of the 
present invention. The absolute value deviation Rn corresponding to each 
Dn is used in the decision functions fS1(n), fS2(n), or fS3(n), etc., to 
select the data Dn in step S160 to be used in the second calculation of 
step S170. As shown by the dotted lines in FIG. 5, the decision function 
fS(n) allows for an increasingly wider deviation range for newer data Dn 
to be selected for the second calculation. The dotted lines shown in the 
example of FIG. 5 approximates the difference function fS2(n) above. 
Accordingly, FIG. 5 shows that data D2 and D3 will be removed from the 
data which is used in the second calculation. 
In a third preferred embodiment of the blurring motion detection device of 
the present invention, the calculation of the first standard value V0' and 
the second standard value V0 in steps S150 to S170 does not use the 
average or arithmetic mean of the data. In this third preferred 
embodiment, the calculation of the first standard value is performed as 
follows: 
EQU V0'=((D1.times.C1)+(D2.times.C2)+. . . +(D10.times.C10)) /(C1+C2+. . . 
+C10); 
EQU C1-C10: positive constants (C1.ltoreq.C2 .ltoreq.. . . .ltoreq.C10). 
This calculation is an example of performing a weighted average calculation 
in which the newer the data is assigned a greater weight than the older 
data. A greater weight is accorded to the newer data because the newer 
data is closer to the time of photography. The constants C1 to C10 do not 
all have to be different values; the values may increase stepwise. The 
constants Cn may also be equal to each other, but C1 cannot be equal to 
C10. 
In an example of this third embodiment shown in FIG. 6, the first standard 
value V0' is calculated with a weighted function having the constant 
Cn=1.1.sup.(n-1). The data Dn in FIG. 6 are depicted with their respective 
weights. The decision function f2S(n) (similar to the decision functions 
of the second preferred embodiment) is a function which changes gradually 
over time, allowing for an increasingly wider deviation range for newer 
data Dn to be selected for the second calculation. Data Dn to be selected 
for the second calculation must fall within the deviation range of 
(V0'-f2S(n)).ltoreq.Dn.ltoreq.(V0'-f2S(n)). The blurring motion zero 
reference value (the second standard value V0) is also calculated using a 
weighted average, similar to the weighted calculation of the first 
standard value V0'. 
A fourth preferred embodiment of the present invention will now be 
described. 
FIG. 7 is a graph illustrating a sample data distribution, deviation 
ranges, and standard values according to a fourth preferred embodiment of 
the present invention. In the example of FIG. 7, the first standard value 
V0' is calculated in step S150 by an arithmetic mean. For step S170, the 
second standard value V0 is calculated using a weighted function similar 
to the third preferred embodiment having a constant Cn=1.1.sup.(n-1). The 
respective weights for each data Dn are also depicted in FIG. 7. Of 
course, this type of weighted average calculation may also be performed in 
step S150 to calculate the first standard value V0' instead of using an 
arithmatic mean. 
In this fourth preferred embodiment, decision values S(old) and S(new) are 
used in step S160 to select the appropriate data Dn. But, since the second 
calculated standard value V0 will reflect the weighted importance of the 
newer data, the setting of the decision values S(old) and S(new) will not 
need to reflect the importance of the newer data as much as in the first 
preferred embodiment. Thus, the difference between the decision values 
S(old) and S(new) used in the data selection in step S160 may be small. 
Alternatively, the decision values S(old) and S(new) may be set to be 
equal. 
In the above embodiments, the blurring motion detection sensor I may be a 
piezoelectric vibration gyro. Thus, the data Dn of FIGS. 4-7 reflect the 
dimensions of angular velocity outputs from the gyro. The data D4 and 
thereafter in FIGS. 4-7 show a center of distribution displaced upwards. 
Such a displacement may result from a panning motion and the data may 
reflect a fixed angular velocity superposed on hand blurring movements. 
Nevertheless, because panning was effected at a fixed angular velocity, 
the second standard value V0 is desirably set to be the average angular 
velocity of the panning velocity. 
Moreover, in the above embodiments, the blurring motion detection sensor 1 
may be an angular displacement sensor or like detection means. Thus, the 
data Dn of FIGS. 4-7 reflect the dimensions of angular displacement 
outputs. In the case of an angular displacement sensor, the upwards 
displacement of the center of the data distribution, D4 and thereafter, 
may reflect a case in which the photographic field angle changed due to 
framing before photography. Nevertheless, because the blurring motion was 
changed at a constant angle even at the time of photography, the standard 
value desirably becomes the second standard value V0, which is the 
averaged angular value after the field angle change. 
With the blurring motion detection device according to the present 
invention, higher accuracy in blurring motion drive control may be 
achieved with a more efficient processing load on the camera control unit 
5. The blurring motion data reflecting blurring motion near the time of 
photography is successively retrieved, averaged, and stored, as discussed 
above for steps S110 to S130. Such successively averaged data reduces the 
overall processing requirements on the camera control unit 5 according to 
the present invention. 
When the full depression switch is depressed, anomalous blurring motion 
data is effectively filtered out from a calculation of a blurring motion 
zero reference value (an improved standard value V0), as discussed above 
for steps S140 to S170. This selection of appropriate data items in the 
calculation of an improved standard value overcomes the problems of the 
previously mentioned conventional art. The blurring motion detection 
device according to the present invention avoids the use of unwanted 
anomalous data reflective of blurring motion deviating too much from the 
blurring motion near the end of photographic preparations or near the time 
of photography. 
Several variations were also described with respect to the method of 
calculating an improved standard value. A decision function fS(n) may be 
used instead of decision values S(old) and S(new). A weighted standard 
value may also be calculated. These variations also improve the accuracy 
and reliability of the blurring motion zero reference value determined by 
the blurring motion detection device of the present invention. 
A true blurring motion value is also easily determined from VS-V0, as 
discussed above for step S180. Thus, the amount of calculation 
accompanying blurring motion compensation control during exposure can be 
reduced and the processing load on the camera control unit 5 can be small. 
Having efficient processing duties placed on the camera control unit 5 
also results in reduced consumption of electric power, allowing for 
reduction in size and cost for the camera. 
It should be understood that the blurring motion detection device according 
to the present invention is particularly suitable for a camera and that 
the term camera is not used in a narrow sense but can include different 
types of camera devices, such as still cameras, video cameras, and the 
like. Moreover, although a few preferred embodiments of the present 
invention have been shown and described, it would be appreciated by those 
skilled in the art that changes may be made in these embodiments without 
departing from the principles and spirit of the invention, the scope of 
which is defined in the claims and their equivalents.