Stopping position control device

A stopping control device includes a stripe pattern formed on an object to be moved and a non-contact type sensor for sensing a boundary between the stripes of the pattern. The stopping mechanism stops the object after a predetermined time has passed after a boundary was sensed so that the sensor beam is positioned at an approximate center of a stripe. The sensor may be a photo reflector sensing a reflectance of each part of the stripes, to sense a boundary therebetween.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a stopping position control device which 
controls the stopping of an object at a predetermined position 
(hereinafter referred to as stopped position). 
2. Description of the Related Art 
Recently, especially with regard to compact cameras, many cameras equipped 
with a power zoom lens have been developed. When a zoom lens is utilized 
usually the full-opened aperture value is changed in accordance with a 
focal length of the lens, and accordingly, the full-opened aperture value 
must be input to the camera control mechanism to carry out an automatic 
exposure control with a zoom lens. Further, in a camera in which an 
exposure program, for example, is changed in accordance with a focal 
length, data relating to the focal length of the lens must be input to the 
camera control mechanism. 
Therefore, in a conventional device, the position of a zoom ring, which 
causes zoom lens groups (a variator lens and a compensator lens) to move 
relatively close to and apart from each other, is sensed and a 
corresponding full-opened aperture value and focal length of the lens are 
obtained from the lens position data. It is noted that no particular 
problem arises if the full-opened aperture value and the focal length of 
the lens are not continuously obtained, and thus this data can be obtained 
at predetermined intervals. 
Two methods of sensing a stopped position of the zoom ring are known; one 
in which a range of movement of the zoom ring is divided into a plurality 
of sections, each section is given a different code, and the codes are 
discriminated by a code discrimating mechanism, and another in which 
periodically varied codes are given to the entire range of movement of the 
zoom ring and a code change counting mechanism is used to count the number 
of changes of the codes from the base position thereof. 
In the former method, digital codes composed of a combination of 
electro-conductive elements and insulating elements are provided at each 
division of the range of movement along a direction of movement of the 
zoom ring. The digital codes are read by a brush kept in slidable contact 
with the electro-conductive element and the insulating element at each 
bit, respectively. 
In a position sensing mechanism using such codes and a brush, however, due 
to deterioration with the passage of time, for example, by rust or 
transformation of the electro-conductive parts, or due to the presence of 
foreign matter between the code plate and the brush, a poor contact 
therebetween is obtained, and accordingly, reading errors easily occur. 
On the other hand, an optical method of code counting is known in which an 
optical stripe pattern composed of high reflectance elements and low 
reflectance elements are arranged alternately along a direction of 
movement of a cam ring. The number of changes of the optical stripe 
pattern are read and counted by an optical mechanism (a photo reflector) 
provided at a fixed position on a camera body, whereby a position of the 
zoom ring is sensed according to the count of the number of changes from 
the base position thereof. 
In this stopping position sensing mechanism, however, if the zoom ring 
stops when a beam from the photo reflector is at a boundary between the 
stripes of the pattern, one of two states occur, i.e., a change of a 
stripe is read and the zoom ring then stopped, or a change of stripe is 
not read and the zoom ring is stopped. Also, when the movement of the zoom 
ring resumes after the zoom ring has been stopped on a stripe boundary, a 
change of a stripe may or may not be read. 
This uncertainty, i.e., the reading or the not reading of the change, is a 
reading error which is accumulated, whereby the error in the full-opened 
aperture value is increased. Further, in such a case, to prevent an 
overrun of the zoom ring, a limit switch must be provided at a position 
opposite to the base position of the zoom ring, and this provision of the 
limit switch inevitably increases the cost of the camera. 
In the electrical reading mechanism described above, the electro-conductive 
elements and the insulating elements can be replaced by an optical pattern 
including two kinds of elements having different optical reflectances, and 
the brush replaced by a plurality of photo reflectors for discriminating 
the optical pattern of each bit. 
A photo reflector, however, is bulkier than a brush, and therefore, the 
size of the camera must be increased to enable the accommodation therein 
of a plurality of photo reflectors, and thus the cost thereof is 
inevitably increased. 
SUMMARY OF THE INVENTION 
Therefore, an object of the present invention is to provide a stopping 
position control device by which a moving object such as a lens drive ring 
is accurately stopped at a predetermined position, whereby accurate data 
of the position of the object is obtained. 
According to the present invention, there is provided a stopping position 
control device comprising a pattern provided in a line along which the 
object is moved and having characteristics which change in a regular 
manner along the line. The stopping position control device further 
comprises a means for discriminating the characteristics of the pattern, 
and a means for stopping the object when a predetermined time has passed 
after the discriminating means has sensed a change of the pattern 
characteristics.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will now be described with reference to embodiments 
shown in the drawings. 
FIG. 1 is a block diagram showing major components of an embodiment in 
which the present invention is applied to a camera having a power zoom 
lens. 
As shown in the Figure, a zoom lens 10 is provided with a lens drive ring 
which is rotated to move lens groups provided in the zoom lens 10. Namely, 
the zoom lens 10 is constructed in such a manner that the zoom lens groups 
(a variator lens and a compensator lens) are moved, by a rotational motion 
of a zoom ring 12, i.e. the lens drive ring, close to and apart from each 
other along the optical axis of the lens, to perform a zooming operation. 
This zoom ring 12 is driven by a DC motor 16, which is driven by a motor 
drive circuit 14, to rotate in the forward and reverse directions to cause 
the zoom lens to move to the telephoto mode or a wide-angle mode. 
A stripe pattern 18 for sensing a stopped position of the zoom ring 12 is 
applied on an outer surface of the zoom ring 12. The stripe pattern 18 is 
constituted by black stripes 18b and white stripes 18w alternately, 
provided in a regular pattern. The stripe pattern 18 is provided along a 
direction of rotation of the zoom ring 12 and in a range covering the 
range of rotation of the zoom ring 12. 
A photo reflector or a photo coupler 20 is disposed at a position facing 
the stripe pattern 18. This photo reflector 20 is a non-contact type 
sensor sensing a reflectance of the stripe pattern 18, and includes a 
radiative device (IRED (infrared rays)) 21 and a photo detector 22. The 
radiative device 21 radiates a sensing beam to the pattern 18, and the 
sensing beam is reflected by the stripe pattern 18 into the photo detector 
22. 
The surface of the stripe pattern 18 is composed of black and white stripes 
18b and 18w, and accordingly, the quantity of the reflected beam received 
by the photo detector 22 is at a maximum when the sensing beam is 
reflected by the white stripes 18w and at a minimum when the sensing beam 
is reflected by the black stripes 18b. When the sensing beam is reflected 
at a boundary between the black and white stripes 18b and 18w, the 
quantity of the reflected beam is an intermediate value corresponding to 
the proportions of black and white on each side of the boundary. Namely, 
the characteristics of a beam reflected by the pattern 18 are regularly 
changed in a line along which the zoom ring 12 is rotated, and these 
changes of the characteristics of the pattern 18 are discriminated by a 
microcomputer 28, as described later. The photo reflector 20 is attached 
to a stationary cylinder (not shown) of the camera body. 
The radiating operation of the radiative device 21 is controlled by a 
radiative device drive circuit 24, and signals output by the photo 
detector 22 are input to a binary circuit 26. 
The binary circuit 26 transforms the output signal of the photo detector 22 
to a binary signal defined by electric "High" and "Low" level signals. 
Namely, when the sensing beam radiated from the radiative device 21 is 
reflected by the white stripe 18w, the binary circuit 26 transforms the 
output signal to a "High" level, and when the sensing beam is reflected by 
the black stripe 18b, the binary circuit 26 transforms the output signal 
to a "Low" level. Thereafter, the binary circuit 26 outputs the binary 
signal to the microcomputer 28. 
The microcomputer 28 controls the rotation of the DC motor 16 through the 
motor drive circuit 14, and counts the number of changes of the output 
signal of the binary circuit 26. Further, the microcomputer 28 carries out 
the calculation, control and drive for various well known functions of the 
camera, such as photometry, distance measurements, and release operations. 
In this embodiment, a stopped position of the zoom ring 12 is sensed in 
accordance with an amount of movement thereof from a base position. 
Namely, the stopped position is sensed in accordance with the number of 
changes of the output signals of the binary circuit 26. Therefore, the 
breadth of each stripe 18b and 18w of the stripe pattern 18 is determined 
in accordance with a pitch by which the zoom ring 12 is rotated and the 
positions at which the zoom ring 12 can be stopped. 
The microcomputer 28 is also provided with a counter for counting the 
number of changes of the output signals of the binary circuit 26, and 
stores a full-opened aperture value and a focal length corresponding to 
the stopped positions of the zoom ring 12. 
The base position of the zoom ring 12 is sensed by a base switch 30 which 
is turned ON when the zoom ring 12 is positioned at the base position and 
outputs an ON signal to the microcomputer 28. The microcomputer 28 checks 
the ON-OFF condition of the base switch 30, to determine whether or not 
the zoom ring 12 is positioned at the base position, and counts the number 
of changes of the output signals of the binary circuit 26 to determine the 
amount of movement of the zoom ring 12 from the base position, to thereby 
obtain a full-opened aperture value and a focal length corresponding to 
the amount of movement of the zoom ring 12. 
A telephoto switch 32 and a wide-angle switch 34 are connected to the 
microcomputer 28, as switches for carrying out a zooming operation of the 
zoom lens 10. The telephoto switch 32 moves the zoom lens 10 toward the 
telephoto side, and the wide-angle switch 34 moves the zoom lens 10 toward 
the wide-angle side. 
An operation of the lens data reading device of the power zoom lens 10 
having the above construction is described below with reference to a flow 
chart shown in FIG. 2. Note that this operation is carried out according 
to a control program stored in a non-illustrated read only memory (ROM) of 
the microcomputer 28. 
This program is started when electric power supply is turned ON, and it is 
determined whether or not the base switch 30 has been turned ON (STEP 51). 
If the base switch 30 has not been turned ON, the DC motor 16 is rotated 
toward the wide-angle side (STEP 52). Namely, a base position check loop 
process composed of STEPs 51 and 52 is repeated until the base switch 30 
is turned ON, i.e., until the zoom ring 12 returns to the base position. 
When the base switch 30 is turned ON, the DC motor 16 is stopped to stop 
the zoom operation (STEP 53), and a zoom position counter is reset (STEP 
54). 
Then, the conditions of the telephoto switch 32 and the wide-angle switch 
34 are checked, and if the switches 32 and 34 are turned OFF, this switch 
check is repeated (STEP 55). If the telephoto switch 32 is turned ON the 
process goes to STEP 56, and conversely, if the wide-angle switch 34 is 
turned ON the process goes to STEP 64. 
If the telephoto switch 32 is turned ON, it is determined whether or not 
the value of the zoom position counter has reached the telephoto limit 
(STEP 56). If the value has not reached the tele limit, the process goes 
to STEP 57, and if the value has reached the telephoto limit, the process 
returns to STEP 55 since the DC motor 16 cannot be further rotated toward 
the telephoto side. 
Where the count of the zoom position counter has not reached the tele 
limit, the radiative device drive circuit 24 is operated to cause the 
radiative device 21 to radiate a beam (STEP 57), and the DC motor 16 is 
rotated toward the tele side (STEP 58). Then, it is determined if a change 
has occurred in an output signal of the binary circuit 26 (STEP 59). If 
the output signal of the binary circuit 26 has not changed, the process 
returns to STEP 56, so that a tele zoom process composed of STEPs 56, 57, 
58 and 59 is repeated until the output of the binary circuit 26 is 
changed. 
When the output of the binary circuit 26 is changed, the value of the zoom 
position counter is increased by 1 (STEP 60), and the process waits for a 
predetermined time (STEP 61). During this waiting time, the sensing beam 
radiated from the radiative device 21 advances to approximately the center 
of a black or white stripe 18b or 18w. 
Then, the DC motor 16 and the radiation of beam by the radiative device 21 
are stopped to stop the zoom operation (STEPs 62 and 63), and the process 
returns to STEP 55; i.e., the process of STEPs 56 through 63 is repeated. 
Namely, the zoom ring 12 is stopped after a predetermined time depending 
upon a rotational speed of the motor 16 has passed after the microcomputer 
28 has sensed a change of the black and white stripes 18b and 18w. That 
is, the zoom ring 12 is stopped after a predetermined time has passed 
after the beam radiated from the radiative device 21 crosses a boundary 
formed on the stripe pattern 18 to define a reflectance change. Then, if 
the tele switch 32 is still turned ON, the process returns to STEP 55, and 
the zoom ring 12 is again rotated until stopped at STEP 62. 
Namely, the process of STEPs 56 through 63 is provided for intermittently 
rotating the zoom ring 12 from a position at which the sensing beam 
radiated from the radiative device 21 reaches the center of a black or 
white stripe 18b or 18w, to a position at which the sensing beam reaches a 
center of the adjacent white or black stripe 18w or 18b. 
Accordingly, while the tele switch 32 is turned ON, the loop process of 
STEPs 55 through 63 is repeated, and the zoom ring 12 is intermittently 
rotated toward the tele side. Then, if the tele switch 32 is turned OFF 
when the zoom ring 12 is stopped at a position at which the sensing beam 
of the radiative device 21 is at an approximate center of a black or white 
stripe 18b or 18w, the switch check process of STEP 55 is repeated. 
On the other hand, if the value of the counter reaches the tele limit while 
the tele switch is turned ON, the process returns from STEP 56 to STEP 55, 
and only the switch check process and the limit check process are 
repeated. Therefore, due to the process of STEPs 56 through 63, the zoom 
ring 12 is stopped at a tele position, at which the sensing beam of the 
radiative device 21 is at an approximate center of a black or white stripe 
18b or 18w. 
When the zoom ring 12 is stopped, the microcomputer 28 obtains lens data of 
a full-opened aperture value or a focal length corresponding to the 
stopped position of the zoom ring 12, according to the value of the zoom 
position counter. Then, when a shutter release switch is operated, as is 
well known, the operations such as an auto focusing, auto exposure and 
shutter release are carried out. 
On the other hand, if the wide-angle switch 34 is turned ON, the process 
goes from STEP 55 to STEP 64, where it is determined whether or not the 
value of the zoom position counter has reached the wide-angle limit (STEP 
64). If the value has reached the wide-angle limit the process returns to 
STEP 55, since the DC motor 16 cannot be further rotated toward the 
wide-angle side, and if the value has not reached the wide-angle limit the 
radiative device 21 radiates the sensing beam (STEP 65), and the DC motor 
16 is rotated toward the wide-angle side (STEP 66). Then, it is determined 
if a change of an output signal of the binary circuit 26 has occurred 
(STEP 67), and if the output signal of the binary circuit 26 has not 
changed, the process returns to STEP 64, and a wide-angle zoom process 
composed of STEPs 64, 65, 66 and 67 is repeated until the output of the 
binary circuit 26 is changed. 
When the output of the binary circuit 26 is changed, the value of the zoom 
position counter is decremented by 1 (STEP 68), and the process waits for 
a predetermined time (STEP 69). Then the DC motor 16 and the radiation of 
the beam by the radiative device 21 are stopped to stop the zoom operation 
(STEPs 70 and 71), and as a result, the zoom ring 12 is stopped at a 
position at which the beam radiated from the radiative device 21 is at an 
approximate center of a black or white stripe 18b or 18w. The process then 
returns to STEP 55. 
STEPs 64, 65, 66, 67, 68, 69, 70 and 71 are basically the same as STEPs 56 
through 63, except that the DC motor 16 is reversely rotated, the value of 
counter is decremented by 1, and the zoom ring 12 is stopped when reaching 
the wide-angle limit position. 
FIG. 3 shows a flow chart of another embodiment of the operation of the 
power zoom lens. 
This flow chart is different from the flow chart shown in FIG. 2 in that 
STEPs 91 and 92 are provided after STEPs 60 and 68, respectively. The 
other STEPs are the same as in FIG. 2. 
Namely, in a zooming operation toward the tele side, after the value of the 
zoom position counter is increased by 1 (STEP 60), it is determined 
whether or not the tele switch 32 is turned OFF (STEP 91). If the tele 
switch 32 is not turned OFF, the process from STEP 56 to STEP 60 is 
carried out so that the zoom ring 12 is further rotated, and if the output 
signal of the binary circuit 26 has changed, the value of the counter is 
increased by 1 (STEP 60). Conversely, if the tele switch 32 is turned OFF, 
the process goes from sTEP 91 to STEP 61, and after a predetermined time 
has passed, the zoom ring 12 and the radiative device are stopped to stop 
the zoom operation (STEPs 62 and 63). 
In a zooming operation toward the wide-angle side, after the value of the 
zoom position counter is decremented by 1 (STEP 68), it is determined 
whether or not the wide-angle switch 34 is turned OFF (STEP 92). If the 
tele switch 34 is not turned OFF, the process from STEP 64 to STEP 68 is 
carried out so that the zoom ring 12 is further rotated. If the tele 
switch 32 is turned OFF (STEP 92), the process goes to STEP 69, and after 
the predetermined time has passed, the zoom ring 12 and the radiative 
device are stopped (STEPs 69 and 70). 
According to the operation shown in FIG. 3, the zoom ring 12 is 
continuously (not intermittently) rotated until the tele switch 32 or the 
wide-angle switch 34 is turned OFF, and is stopped at a position at which 
the sensing beam from the radiative device 21 is at an approximate center 
of the black or white stripe 18b or 18w. 
According to the embodiments of the present invention, when the sensing 
beam from the radiative device 21 passes through a boundary between the 
black and white stripes 18b and 18w and is positioned at an approximate 
center of another black or white stripe 18b or 18w, the zoom ring 12 is 
stopped, and thus the number of stripe boundaries passed cannot be 
misread. 
Further, although int he above embodiments, the zoom ring 12 is moved to 
the base position when an electric power supply is turned ON, the 
construction can be modified so that the zoom ring 12 is moved to the base 
position when the electric power supply is turned OFF, and photographing 
can be carried out as soon as the electric power supply is turned ON. In 
this case, however, the zoom ring 12 must be once moved to the base 
position when the electric power supply is turned ON. This is because, if 
the battery is exhausted when the zoom ring 12 is positioned at a position 
other than the initial position, or has been removed from the camera, the 
zoom ring 12 will not be returned to the base position. 
In the above description, the present invention is explained with reference 
to the embodiments applied to the driving of the zoom ring provided on the 
power zoom lens, but the present invention can be also applied to the 
driving of a focusing lens drive ring provided for moving a focusing lens 
of a single focal length lens. Further, although the above description 
concerns a rotating zooming type zoom ring as a lens drive ring, the type 
of movement of the zoom ring, i.e., the lens drive ring, is not important. 
For example, the present invention can be applied to a linear moving lens 
drive ring, or a linear moving rotating lens drive ring. 
The stripe pattern 18 is not restricted to black and white stripes, but can 
be any pattern by which the amount of movement of the zoom ring 12 from 
the base position can be detected. Namely, the stripe pattern 18 may be 
formed by different colored stripes. 
As the position sensing mechanism, instead of the optical sensing, a 
construction in which a magnetic signal is used and the existence or the 
polarity of the magnetic signal is sensed, or a construction in which a 
change of an electrostatic capacity is sensed can be used, as long as a 
sensor sensing a code indicating a stopped positoin of the zoom ring 12 
does not stop at a boundary of the code. 
As understood from the above description, according to the lens drive 
device of the embodiments of the present invention, a code indicating the 
position of the zoom ring 12 is optically read, i.e., without contact, and 
thus reading errors due to a poor contact or rust do not occur. Further, 
since the lens drive ring is stopped after sensing that the lens drive 
ring has passed through a boundary of the code, a code reading error is 
prevented, and the code of the position at which the lens drive ring is 
stopped is accurately read. Therefore, accurate lens data such as a 
full-opened aperture value corresponding to a position at which the lens 
drive ring is stopped is obtained. Further, since the lens drive ring 
cannot be overrun, a limit switch sensing a movement limit position of the 
lens drive ring need not be provided. 
Although the embodiments of the present invention have been described 
herein with reference to the accompanying drawings, obviously many 
modifications and changes may be made by those skilled in this art without 
departing from the scope of the invention.