CA1173284A - Auto focus system - Google Patents
Auto focus systemInfo
- Publication number
- CA1173284A CA1173284A CA000397160A CA397160A CA1173284A CA 1173284 A CA1173284 A CA 1173284A CA 000397160 A CA000397160 A CA 000397160A CA 397160 A CA397160 A CA 397160A CA 1173284 A CA1173284 A CA 1173284A
- Authority
- CA
- Canada
- Prior art keywords
- lens
- light source
- distance measuring
- reflected
- focus
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B3/00—Focusing arrangements of general interest for cameras, projectors or printers
- G03B3/10—Power-operated focusing
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/28—Systems for automatic generation of focusing signals
- G02B7/282—Autofocusing of zoom lenses
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Focusing (AREA)
- Automatic Focus Adjustment (AREA)
- Character Input (AREA)
- Accessories Of Cameras (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An automatic focus system for a camera in which a beam of light is directed toward a subject from a light source within the camera, and a portion of the light beam reflected from the subject back to the camera is sensed by photoelectric means.
The angle between the emitted light and the reflected beam is translated by mechanical means into a mechanical movement which is a function of the distance to the point of reflection. The auto focusing system as herein described provides a zoom lens system in which the zoom lens is adjustable to change from a normal focal length to a longer focal length and in which a subject may be brought into focus by axial movement of at least one lens component of the zoom lens system. The zoom lens is located in front of a screen in the camera and the zoom lens system is arranged to focus the viewing subject thereon. An auto focus system herein described comprises a pick-up lens including a zoom system, a distance measuring light source and a distance measuring light receiving portion, said pick-up lens having a focus adjusting mechanism, the distance measuring light source being illuminated, and a detecting device for detecting the angle of the reflected light beam emitted from said light source and reflected by the subject, the focus adjusting mechanism being driven in accordance with the detected distance determined by the measurement output and either of the distance measurements.
An automatic focus system for a camera in which a beam of light is directed toward a subject from a light source within the camera, and a portion of the light beam reflected from the subject back to the camera is sensed by photoelectric means.
The angle between the emitted light and the reflected beam is translated by mechanical means into a mechanical movement which is a function of the distance to the point of reflection. The auto focusing system as herein described provides a zoom lens system in which the zoom lens is adjustable to change from a normal focal length to a longer focal length and in which a subject may be brought into focus by axial movement of at least one lens component of the zoom lens system. The zoom lens is located in front of a screen in the camera and the zoom lens system is arranged to focus the viewing subject thereon. An auto focus system herein described comprises a pick-up lens including a zoom system, a distance measuring light source and a distance measuring light receiving portion, said pick-up lens having a focus adjusting mechanism, the distance measuring light source being illuminated, and a detecting device for detecting the angle of the reflected light beam emitted from said light source and reflected by the subject, the focus adjusting mechanism being driven in accordance with the detected distance determined by the measurement output and either of the distance measurements.
Description
::~i'73Z~
Field of the_Invention:
The present invention xelates generally to an auto focus system and is directed more particularly to an auto focus system which is particularly suitable for use with a television camera which includes, for example, a zoom lens.
Description of the Prior Art:
A prior art camera is described in the Paqel U.S. Patent No. 3,442,193, in which a focusing state is detected and displayed on a view finder. Also, known in the prior art is a system for automatically controlling the ~ocusing state of the camera by utilizing the above focusing state detecting sys~em.
BRIE~ DESCRXPTION OF THE DRAWINGS
Fig. 1 is a schematic diagram showing the construction of a conventional auto focus system;
Figs. 2A to 2C are diagrams used to explain the conven-tional auto focus system shown in ~ig. 1;
Fig. 3 is a schematic diagram showing one ~mbodiment of the auto focus system according to the present invention; and Figs. 4A and 4B are explanatory diagrams useful for show-ing the effect which the auto focus system according to the present invention can achieve.
In one such auto focus system, a conventional auto focus system is employed as illustrated in Fig. 1. Shown in Fig. 1 is an arrangement in which reference numeral 1 denotes a pick-up or camera lens and 2 designates a focusing screen. The lens 1 iB
provided with a focus adjusting mechanism and the focus adjusting mechanism is driven by a driving member or driver 3. There is further provided a light source 4 and a light receiving member 5 used to measure a distance between an object and a camera body.
Field of the_Invention:
The present invention xelates generally to an auto focus system and is directed more particularly to an auto focus system which is particularly suitable for use with a television camera which includes, for example, a zoom lens.
Description of the Prior Art:
A prior art camera is described in the Paqel U.S. Patent No. 3,442,193, in which a focusing state is detected and displayed on a view finder. Also, known in the prior art is a system for automatically controlling the ~ocusing state of the camera by utilizing the above focusing state detecting sys~em.
BRIE~ DESCRXPTION OF THE DRAWINGS
Fig. 1 is a schematic diagram showing the construction of a conventional auto focus system;
Figs. 2A to 2C are diagrams used to explain the conven-tional auto focus system shown in ~ig. 1;
Fig. 3 is a schematic diagram showing one ~mbodiment of the auto focus system according to the present invention; and Figs. 4A and 4B are explanatory diagrams useful for show-ing the effect which the auto focus system according to the present invention can achieve.
In one such auto focus system, a conventional auto focus system is employed as illustrated in Fig. 1. Shown in Fig. 1 is an arrangement in which reference numeral 1 denotes a pick-up or camera lens and 2 designates a focusing screen. The lens 1 iB
provided with a focus adjusting mechanism and the focus adjusting mechanism is driven by a driving member or driver 3. There is further provided a light source 4 and a light receiving member 5 used to measure a distance between an object and a camera body.
-2-9 light source 4 radiates, for example, an infrared radiation beam toward the optical axis of the lens 1 and the light receiving direction of the light receiving member 5 is changed along a plane which includes an infxared radiation beam emitted from the light source 4 and the ~ptical axis of the lens 1, so that a light, which is the infrared radiation beam fr~m the light source 4 strikes an object 6 and is reflected and detected thereby. This detecting signal from the light receiving member S
is delivered to a si~nal processing circuit or processor 7 to measure the distance,.
In other words, in case of measuring the distance, the light sourcc 4 is illumin~ted by tl-e signal derived from the processor 7 and at the same time, the light recPiving direction of the liaht receiving member 5 is gradually changed or displaced from the direction parallel to the optical axis of the lens 1 to the inside as shown by an arrow P in Fig. 1. When the reflected light beam from the object 6 is detected by the light receiving member 5, the detected signal responsive to the angle of the light receiving direction of the light receiving member 5 is supplied to the processor 7 to measure the distance from the camera body to the object 6.
A signal responsive to the measured distance is delivered from the processor 7 to the driver 3 to adjust the focus or focal point of the lens 1.
Further, as shown in Fig. 1, the pick-up lens 1 is also provided with a 200m system 8. In this example of the prior art auto focus system seen in the figure, the zoom system 8 consist~
of a concave lens 8a and a convex lens 8b and is used as a telephoto lens by locating the concave lens 8a near the convex lens 8b, and is used as a wide-angle lens by moving the concave lens 8a away from the convex lens 8b. The focu5 adjustment of this camera lens 1 i~ carried out in such a manner as to move a convex lens la just befor~ and after. In this case, another convex lens lb is formed as a fixed lens. As shown in Fig. 1, ~L~L'73Z~
letter W represents a range of luminous flux receiv~d from the ~bject 6 in case o the wide angle lens mode and letter T
represents a like range of the telephoto lens mode, respectively.
In this auto focus system, owing to the fact that the lens 1 and the optical system composing the light source 4 ~nd and the light xeceiving member 5 for the distance measuring are all independently constructbd, even if the optical field of the lens 1, whieh i~ used for example, the zoom lens, i5 changed in each case of the telephoto and wide-angle lenses, a range S of irradiated luminous ~lux emitted from the light source 4 is not altered.
To describe this more specifically with reference to Figs. 2A to 2C, Fig. 2A describes a case, for example, where the zoom lens is utilized as the standard lens. In this case, the object 6, which will be displayed or projected on a view finder F
of the camera, is indicated thereon as shown in the figure. It is assumed that the range S of the irradiated luminous flux at this time will be represented by a broken line D. On the othPr hand, Fig. 2B shows a case in which the zoom lens is used as the tele-photo lens and therefore the object 6 is enlarged as illustrated in the figure. At this time, although the range S of the irradiated luminous flux stays within the fixed range relative to the object 6, the distance measuring range is forced to be enlarged to cover almost all area of the field as shown by one dot chain line D' in accordance with the fact that the object 6 displayed within the finder F is also enlarged. Further, Fig.
~C describes a case in which the zoom lens is used as the wide angle lens and the object 6 to be displayed within the finder F is reduced as ilIustrated in the figure and the distance measuring range (shown by two dots chain line D'~ in FigO 2C~
becomes small.
As described abov2, in case of the zoom lens, an apparent di~tance measurang range relative t~ the frame of th~ view finder F i~ fluctuated. But, in these cases, although the dis ance measuring rnages D' and D" to the frame of the vi~w finder F are ~L'73~
~ ased or reduced, such increase or reduction is not perceivableon the view finder F, so that it can not be known after all where or whether the object 6 is precisely focused.
In other words, in such cases, user is apt to hanale the camera system while to believe the distance measuring range as being fixed ~shown by the broken line D). As a result, when the zoom lens is used as, for example, the telephoto lens, there is a fear that if another object exists between the distance measuring ranges D (shown by the broken line) and D' Ishown by one dot chain line) which is before or after that object 6, the focus adjustment will be forced to be made before or after that object 6 even when that object 6 is caught within the broken line D on the finder F
in Fig. 2B. This results in such a defect that when a picture of a round-shaped object such as a human figure is taken, the focus adjustment is liable to be per~ormed around the part of the object to be picked up, so that the focus is not correctly made coincident with the intended part of the object. When the zoom lens is used as the wide-angle lens, even if the object 6 is caught within the broken line D on the finder F as seen in Fig. 2C, there is also a fear that the focus adjustment will not be per-formed when the object 6 exists outside of two dots chain line D".
In this case, in case of the telephoto lens, since the depth of the field is small, it is necessary to adjust the focus correctly. On the other hand, in case of the wide-angle lens, it is permissible that the focus may be adjusted roughly to a certain extent because the depth of the field thereof bPcomes large. In other words, in case of the known auto focus system as set forth above, the precision on the distance measurement is lost parti-cularly when the zoom lens is used as the telephoto lens which normally requires high precision in focus adjustment.
OBJECTS AND SVMMARY C)F THE INVENTION ~
Therefore, it i~ an object of this invention to provide an auto focus system which can remove the aforedescribed de~ects inh~rent to the conventional auto focus system.
It is another object of this invention to provide an auto focus system which is simple in construction and which can prevent the occurrence of the a~ove men~ioned fluctuation of ~he distance measuring range.
According to an aspect of the present invention, there is provided an auto focus system comprising a pick-up lens ~ncluding a zoom lens system, a distance measuring light source and a distance measuring light receivin~ portion, the pick-up lens having a focus adjusting mechanism, the distance measuring light source beina illuminated, and a detecting device is provided for detecting the angle of the reflected light beam emitted from th~ light source and reflected by an object, the focus adjusting mechanism beinq driven in accordance with the detected distance measurement output and either of the distance measuring light source and the distance measuring light receiving portisn being disposed behind the zoom system within the pick-up lens.
The other objects, ~eatures and advantages of the present invention will become apparent from the ~ollowing description taken in conjunction with the accompanying drawings through which the like references desi~nate the same elements and parts.
DESCRIPTION OF T~E PREFERRED EMBODIMENT
Now, one embodiment vf the auto focus system according to the pre ent inv ntio~ will hereinafter be described with reference to the attached drawings.
As shown in Fig. 3, a half mirror 9 having an angle 45~
relative to the optic~l axis of the lens system is provided between these zoom system 8 and the convex lens of the lens system 1. The light receiving mem~er 5 ~or measuring the distance is locat~d at the position where the optical axis of the lens 8ystem 1 is ~ ec~ed by the half mirror 9. The light ~ource 4 i5 provided at the p~sition of the light receiving member 5 as was previously illustrated in Fig. 1. ~he irradiation direction of the beam irradiated from this light source 4 is adapted to change along a plane which includes the optical axis of the lens 1.
In the auto focus system of the present invention thus arranged, the distance measurement i~ carried out as follows. When it is desired to perform the aistance measurement, the light ~ource 4 is illuminated by the signal derived from the processor 7 and the irradiation direction of the light beam therefrom is changed from the direction parallel to the sptical axis of the lens 1 to the inside gradually, as indicated by the arrow P. When the reflected light beam reflected by the object 6 is entered in~o the convex lens la, then it is passed thr~ugh the zoom system 8 and reflected by the half mirror 9 so as to be introduced into the light receiving member 5, the detecting signal responsive to the angle 3LJ 732~
of the irradiation clirection of the beam emitted from the light source 4 is delivered -from the liyh-t receiviny member 5 to the processor 7 by which the distance from the camera body to the objec-t 6 is measured.
Therefore, in accordance wi-th this system, since the light receiving member 5 is located behind the zoom system 8~ the ranqe (distance measuring range) of the light received by the light receiving member 5 becomes always fixed by following the field enlarged or reduced by the zoom system 8 and the distance measur~
ing ranges in the telephoto and wide-angle lenses make the cons-tant values against the frame of the view finder F, so that the object 6 can be ascertained ~ithout difficulty. In other words, as shown in Fig. 3, in case of the telephoto lens, the distance measurement is carried out in the range shown by one dot chain line T, and in case o the wide-angle lens, the distance measure-ment is performed in the range shown by two dots chain line W.
In case of the telephoto lens, the dis-tance measurement is carried out with the accuracy higher than the wide-angle lens. Because, in the wide-angle lens mode, the focal position of the reflected light against all areas of the object 6 is largel~v moved within the range shown by 1W in Fig. 3, thus giving rise to the scattering of the focal position. On the contrary, in the telephoto lens mode, the area of the re~lected light is quite narrow, so tha~ the focal position is only moved within the range shown by LT in Fig.
is delivered to a si~nal processing circuit or processor 7 to measure the distance,.
In other words, in case of measuring the distance, the light sourcc 4 is illumin~ted by tl-e signal derived from the processor 7 and at the same time, the light recPiving direction of the liaht receiving member 5 is gradually changed or displaced from the direction parallel to the optical axis of the lens 1 to the inside as shown by an arrow P in Fig. 1. When the reflected light beam from the object 6 is detected by the light receiving member 5, the detected signal responsive to the angle of the light receiving direction of the light receiving member 5 is supplied to the processor 7 to measure the distance from the camera body to the object 6.
A signal responsive to the measured distance is delivered from the processor 7 to the driver 3 to adjust the focus or focal point of the lens 1.
Further, as shown in Fig. 1, the pick-up lens 1 is also provided with a 200m system 8. In this example of the prior art auto focus system seen in the figure, the zoom system 8 consist~
of a concave lens 8a and a convex lens 8b and is used as a telephoto lens by locating the concave lens 8a near the convex lens 8b, and is used as a wide-angle lens by moving the concave lens 8a away from the convex lens 8b. The focu5 adjustment of this camera lens 1 i~ carried out in such a manner as to move a convex lens la just befor~ and after. In this case, another convex lens lb is formed as a fixed lens. As shown in Fig. 1, ~L~L'73Z~
letter W represents a range of luminous flux receiv~d from the ~bject 6 in case o the wide angle lens mode and letter T
represents a like range of the telephoto lens mode, respectively.
In this auto focus system, owing to the fact that the lens 1 and the optical system composing the light source 4 ~nd and the light xeceiving member 5 for the distance measuring are all independently constructbd, even if the optical field of the lens 1, whieh i~ used for example, the zoom lens, i5 changed in each case of the telephoto and wide-angle lenses, a range S of irradiated luminous ~lux emitted from the light source 4 is not altered.
To describe this more specifically with reference to Figs. 2A to 2C, Fig. 2A describes a case, for example, where the zoom lens is utilized as the standard lens. In this case, the object 6, which will be displayed or projected on a view finder F
of the camera, is indicated thereon as shown in the figure. It is assumed that the range S of the irradiated luminous flux at this time will be represented by a broken line D. On the othPr hand, Fig. 2B shows a case in which the zoom lens is used as the tele-photo lens and therefore the object 6 is enlarged as illustrated in the figure. At this time, although the range S of the irradiated luminous flux stays within the fixed range relative to the object 6, the distance measuring range is forced to be enlarged to cover almost all area of the field as shown by one dot chain line D' in accordance with the fact that the object 6 displayed within the finder F is also enlarged. Further, Fig.
~C describes a case in which the zoom lens is used as the wide angle lens and the object 6 to be displayed within the finder F is reduced as ilIustrated in the figure and the distance measuring range (shown by two dots chain line D'~ in FigO 2C~
becomes small.
As described abov2, in case of the zoom lens, an apparent di~tance measurang range relative t~ the frame of th~ view finder F i~ fluctuated. But, in these cases, although the dis ance measuring rnages D' and D" to the frame of the vi~w finder F are ~L'73~
~ ased or reduced, such increase or reduction is not perceivableon the view finder F, so that it can not be known after all where or whether the object 6 is precisely focused.
In other words, in such cases, user is apt to hanale the camera system while to believe the distance measuring range as being fixed ~shown by the broken line D). As a result, when the zoom lens is used as, for example, the telephoto lens, there is a fear that if another object exists between the distance measuring ranges D (shown by the broken line) and D' Ishown by one dot chain line) which is before or after that object 6, the focus adjustment will be forced to be made before or after that object 6 even when that object 6 is caught within the broken line D on the finder F
in Fig. 2B. This results in such a defect that when a picture of a round-shaped object such as a human figure is taken, the focus adjustment is liable to be per~ormed around the part of the object to be picked up, so that the focus is not correctly made coincident with the intended part of the object. When the zoom lens is used as the wide-angle lens, even if the object 6 is caught within the broken line D on the finder F as seen in Fig. 2C, there is also a fear that the focus adjustment will not be per-formed when the object 6 exists outside of two dots chain line D".
In this case, in case of the telephoto lens, since the depth of the field is small, it is necessary to adjust the focus correctly. On the other hand, in case of the wide-angle lens, it is permissible that the focus may be adjusted roughly to a certain extent because the depth of the field thereof bPcomes large. In other words, in case of the known auto focus system as set forth above, the precision on the distance measurement is lost parti-cularly when the zoom lens is used as the telephoto lens which normally requires high precision in focus adjustment.
OBJECTS AND SVMMARY C)F THE INVENTION ~
Therefore, it i~ an object of this invention to provide an auto focus system which can remove the aforedescribed de~ects inh~rent to the conventional auto focus system.
It is another object of this invention to provide an auto focus system which is simple in construction and which can prevent the occurrence of the a~ove men~ioned fluctuation of ~he distance measuring range.
According to an aspect of the present invention, there is provided an auto focus system comprising a pick-up lens ~ncluding a zoom lens system, a distance measuring light source and a distance measuring light receivin~ portion, the pick-up lens having a focus adjusting mechanism, the distance measuring light source beina illuminated, and a detecting device is provided for detecting the angle of the reflected light beam emitted from th~ light source and reflected by an object, the focus adjusting mechanism beinq driven in accordance with the detected distance measurement output and either of the distance measuring light source and the distance measuring light receiving portisn being disposed behind the zoom system within the pick-up lens.
The other objects, ~eatures and advantages of the present invention will become apparent from the ~ollowing description taken in conjunction with the accompanying drawings through which the like references desi~nate the same elements and parts.
DESCRIPTION OF T~E PREFERRED EMBODIMENT
Now, one embodiment vf the auto focus system according to the pre ent inv ntio~ will hereinafter be described with reference to the attached drawings.
As shown in Fig. 3, a half mirror 9 having an angle 45~
relative to the optic~l axis of the lens system is provided between these zoom system 8 and the convex lens of the lens system 1. The light receiving mem~er 5 ~or measuring the distance is locat~d at the position where the optical axis of the lens 8ystem 1 is ~ ec~ed by the half mirror 9. The light ~ource 4 i5 provided at the p~sition of the light receiving member 5 as was previously illustrated in Fig. 1. ~he irradiation direction of the beam irradiated from this light source 4 is adapted to change along a plane which includes the optical axis of the lens 1.
In the auto focus system of the present invention thus arranged, the distance measurement i~ carried out as follows. When it is desired to perform the aistance measurement, the light ~ource 4 is illuminated by the signal derived from the processor 7 and the irradiation direction of the light beam therefrom is changed from the direction parallel to the sptical axis of the lens 1 to the inside gradually, as indicated by the arrow P. When the reflected light beam reflected by the object 6 is entered in~o the convex lens la, then it is passed thr~ugh the zoom system 8 and reflected by the half mirror 9 so as to be introduced into the light receiving member 5, the detecting signal responsive to the angle 3LJ 732~
of the irradiation clirection of the beam emitted from the light source 4 is delivered -from the liyh-t receiviny member 5 to the processor 7 by which the distance from the camera body to the objec-t 6 is measured.
Therefore, in accordance wi-th this system, since the light receiving member 5 is located behind the zoom system 8~ the ranqe (distance measuring range) of the light received by the light receiving member 5 becomes always fixed by following the field enlarged or reduced by the zoom system 8 and the distance measur~
ing ranges in the telephoto and wide-angle lenses make the cons-tant values against the frame of the view finder F, so that the object 6 can be ascertained ~ithout difficulty. In other words, as shown in Fig. 3, in case of the telephoto lens, the distance measurement is carried out in the range shown by one dot chain line T, and in case o the wide-angle lens, the distance measure-ment is performed in the range shown by two dots chain line W.
In case of the telephoto lens, the dis-tance measurement is carried out with the accuracy higher than the wide-angle lens. Because, in the wide-angle lens mode, the focal position of the reflected light against all areas of the object 6 is largel~v moved within the range shown by 1W in Fig. 3, thus giving rise to the scattering of the focal position. On the contrary, in the telephoto lens mode, the area of the re~lected light is quite narrow, so tha~ the focal position is only moved within the range shown by LT in Fig.
3. Accordin~ly, the precision in the focus adjustment is improved more in the telephoto lens mode as compared with the wide-angle lens mode.
In this way, the distance is measured and the focus of the lens 1 is adjusted. According to the embodiment of this invention, since the distance measuring range on the view finder F is not '732B~
changed in both cases of -the telep~o-to and wicle~an~le lenses, there is no possibility that the user may misoperate the auto focus sys-tem. In addition, in case of the -telephoto lens, the more accurate distance measurement is carried out and -therefore good focus adjustment can always be done.
Fur-ther, although in case of the prior ar-t auto focus system as seen in Fig. 1, there is a fear that the error in measuring the distance will occur especially when the short distance measurement is done, since the beam from the light source 4 is spaced apart from the optical axis of the lens 1, according to the auto focus system of the present invention, the light receiving member 5 is so arranged -that the ligh-t receiving member 5 receives the light passed through the optical axis of the lens system 1, so that there is no fear that the aforesaid error in measuring the distance will be caused. ~his will be described with reference -to Figs. 4A and 4B wllich respectively illustrate the presence or absence of a so-called parallax in measuring the distance in case of -the convent:Lonal auto focus system and the system according to the presen-t invention. In the figures, reference numeral ]0 designates a camera body. As shown in Fig. 4~, due to the fact that the irradiation direction of the infrared light emitted from the light source 4 is fixed in the prior art, irradiated areas Sx, S~, Sz against objects X, Y
and Z by the light from the light source 4 are displaced in response to the distance of the objects X, Y and Z Erom the camera body 10. Accordingly, the value of the luminous flux to be detected by the light receiving member 5 is changed by the distance occupied by the camera body 10 and the objec-ts X, Y and Z, thereby giving rise to the error in measuring the distance. Fig. 4B
illustrates the case of the present invention in ~hich the light L73289~
source and the light receiving member are exchanged as compared with those of Fig. 3. In case oE Fig~ ~B, the infrared light is emitted from a light source 12 buil-t in the camera body 10 to irradiate the respective objects X, Y and ~ by way of ~ mirror 13.
In accordance with this example, i-t is understood that the irradiated areas Sx Sy and Sz are always made coincident with the respective objects X, Y and Z irrespective of the distances occupied by the camera body 10 and the objects X, Y and Z each and therefore no parallax occurs.
In case of the conventional auto focus system as shown in Fig. l, since there are provided the light source 4 and the light receiving member 5 in addition to the lens 1, this greatly re-stricts the well-known auto focus system in design. But, according to the auto focus system of the present invention, since only the light source 4 is prepared in addition to the lens 1, the aforementioned restr.iction in design upon the system is largely reduced.
In the auto focus system according to the present inven-tion, the half mirror 9 is formed of a dichroic mirror which re-flects the beam of the infrared rays to introduce it into the light receiving member 5 and which also serves to introduce a visible light into a target screen (not shown) of the pick-up tube.
Therefore, according to this invention, it becomes possible to measure the distance without a cut filter of the infrared rays which is normally located in front of the pick-up tube.
While in this embodiment there is disclosed the auto focus system in which any one of the light source and the light receiving member is relatively rotated to measure the distance of the o~ject away from the camera body, the embodiment of the present invention 73~
is not limited to the aforesaid embodiment and such modi:Eication may also be possible for example, that both of the light source and light receiving member are no-t rotatably moved but fixed and instead, there is simply provided two light receiving members in parallel to each other whereby the rotation angles of the light receiving members are made correspondent to the output ratio of these two light receiving members to detect the focus.
In this case, in the afore described arrangement, it may also be possible that the arrangement of the light source ~ and the light receiving member 5 is exchanged as shown in Fig. 4B, but instead, the light source 4 is located within the lens 1.
The above description is given on a single preferred em-bodiment oE the invention, but it will be apparen-t that many modifications and variations could be effected by one skilled in the art without departing from the spirit or scope o~ the novel concepts of the invent.ion, so that the scope of the inven-tion should be de-termined by the appended claims only.
In this way, the distance is measured and the focus of the lens 1 is adjusted. According to the embodiment of this invention, since the distance measuring range on the view finder F is not '732B~
changed in both cases of -the telep~o-to and wicle~an~le lenses, there is no possibility that the user may misoperate the auto focus sys-tem. In addition, in case of the -telephoto lens, the more accurate distance measurement is carried out and -therefore good focus adjustment can always be done.
Fur-ther, although in case of the prior ar-t auto focus system as seen in Fig. 1, there is a fear that the error in measuring the distance will occur especially when the short distance measurement is done, since the beam from the light source 4 is spaced apart from the optical axis of the lens 1, according to the auto focus system of the present invention, the light receiving member 5 is so arranged -that the ligh-t receiving member 5 receives the light passed through the optical axis of the lens system 1, so that there is no fear that the aforesaid error in measuring the distance will be caused. ~his will be described with reference -to Figs. 4A and 4B wllich respectively illustrate the presence or absence of a so-called parallax in measuring the distance in case of -the convent:Lonal auto focus system and the system according to the presen-t invention. In the figures, reference numeral ]0 designates a camera body. As shown in Fig. 4~, due to the fact that the irradiation direction of the infrared light emitted from the light source 4 is fixed in the prior art, irradiated areas Sx, S~, Sz against objects X, Y
and Z by the light from the light source 4 are displaced in response to the distance of the objects X, Y and Z Erom the camera body 10. Accordingly, the value of the luminous flux to be detected by the light receiving member 5 is changed by the distance occupied by the camera body 10 and the objec-ts X, Y and Z, thereby giving rise to the error in measuring the distance. Fig. 4B
illustrates the case of the present invention in ~hich the light L73289~
source and the light receiving member are exchanged as compared with those of Fig. 3. In case oE Fig~ ~B, the infrared light is emitted from a light source 12 buil-t in the camera body 10 to irradiate the respective objects X, Y and ~ by way of ~ mirror 13.
In accordance with this example, i-t is understood that the irradiated areas Sx Sy and Sz are always made coincident with the respective objects X, Y and Z irrespective of the distances occupied by the camera body 10 and the objects X, Y and Z each and therefore no parallax occurs.
In case of the conventional auto focus system as shown in Fig. l, since there are provided the light source 4 and the light receiving member 5 in addition to the lens 1, this greatly re-stricts the well-known auto focus system in design. But, according to the auto focus system of the present invention, since only the light source 4 is prepared in addition to the lens 1, the aforementioned restr.iction in design upon the system is largely reduced.
In the auto focus system according to the present inven-tion, the half mirror 9 is formed of a dichroic mirror which re-flects the beam of the infrared rays to introduce it into the light receiving member 5 and which also serves to introduce a visible light into a target screen (not shown) of the pick-up tube.
Therefore, according to this invention, it becomes possible to measure the distance without a cut filter of the infrared rays which is normally located in front of the pick-up tube.
While in this embodiment there is disclosed the auto focus system in which any one of the light source and the light receiving member is relatively rotated to measure the distance of the o~ject away from the camera body, the embodiment of the present invention 73~
is not limited to the aforesaid embodiment and such modi:Eication may also be possible for example, that both of the light source and light receiving member are no-t rotatably moved but fixed and instead, there is simply provided two light receiving members in parallel to each other whereby the rotation angles of the light receiving members are made correspondent to the output ratio of these two light receiving members to detect the focus.
In this case, in the afore described arrangement, it may also be possible that the arrangement of the light source ~ and the light receiving member 5 is exchanged as shown in Fig. 4B, but instead, the light source 4 is located within the lens 1.
The above description is given on a single preferred em-bodiment oE the invention, but it will be apparen-t that many modifications and variations could be effected by one skilled in the art without departing from the spirit or scope o~ the novel concepts of the invent.ion, so that the scope of the inven-tion should be de-termined by the appended claims only.
Claims (6)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An auto focus system comprising, a pick-up lens including a zoom system, a distance measuring light source for emitting infrared rays, a distance measuring light receiving means, said pick-up lens having a focus adjusting mechanism, means for illuminating said distance measuring light source, and a detecting means for detecting the angle of the reflected infrared rays emitted from said light source and reflected by an object, means for driving said focus adjusting mechanism according to the detected distance measurement output, and either the center of infrared rays emitted from said distance measuring light source of the center of the reflected infrared rays to said distance measuring light receiving means being coincident with the optical axis of said zoom system within said pick up lens.
2. An auto focus system comprising a pick-up lens including a zoom system, a distance measuring light source, a distance measuring light receiving portion, said pick-up lens having a focus adjusting mechanism, said distance measuring light source being illuminated, and a detecting means for detecting the angle of the reflected light beam emitted from said light source and reflected by an object, said focus adjusting mechanism being driven in accordance with the detected distance measurement output, either of said distance measuring light source and said distance measuring light receiving portion being disposed behind said zoom system within said pick-up lens.
3. An auto focus system according to claim 2, wherein said detecting means for detecting the angle of the. reflected light beam is formed of means for rotating either one or the other of said light source and said light receiving portion relatively.
4. An auto focus system according to claim 2, wherein said light source being a light source for emitting infrared rays and said pick-up lens system includes a mirror for reflecting a portion of said infrared rays to by-pass them.
5. An automatic focus system for a camera in which a beam of light is directed toward a subject from a light source within the camera, a portion of said light beam being reflected from the subject back to the camera, sensing means in said camera in which the angle between the emitted and the reflected beam is translated by mechanical means into a mechanical movement which is a function of the distance to the point of reflection.
6. In a photographic camera having a zoom lens, said zoom lens having at least one lens component mounted for movement along the optic axis of said lens for pro-viding a change in the effective focal length of said lens, an auto focusing means for automatically adjusting the effective focal length of said zoom lens to bring said lens into sharp focus.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56038447A JPS57154206A (en) | 1981-03-17 | 1981-03-17 | Focusing device |
| JP38447/81 | 1981-03-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1173284A true CA1173284A (en) | 1984-08-28 |
Family
ID=12525538
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000397160A Expired CA1173284A (en) | 1981-03-17 | 1982-02-26 | Auto focus system |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS57154206A (en) |
| KR (1) | KR890001454B1 (en) |
| AT (1) | AT376813B (en) |
| CA (1) | CA1173284A (en) |
| DE (1) | DE3209517A1 (en) |
| FR (1) | FR2502354B1 (en) |
| GB (1) | GB2095505A (en) |
| NL (1) | NL8201070A (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3310601C2 (en) * | 1982-03-24 | 1994-02-10 | Canon Kk | Distance measuring device |
| JPS5995336U (en) * | 1982-12-17 | 1984-06-28 | ソニー株式会社 | Video camera |
| JPS606114U (en) * | 1983-06-24 | 1985-01-17 | キヤノン株式会社 | focus detection device |
| US4801963A (en) * | 1985-12-18 | 1989-01-31 | Canon Kabushiki Kaisha | Focus detecting system |
| US5305047A (en) * | 1988-10-11 | 1994-04-19 | Canon Kabushiki Kaisha | Pattern projector having a multi-portion projection lens and camera comprising the same |
| KR102093637B1 (en) * | 2017-10-20 | 2020-03-27 | 전자부품연구원 | Lidar device and system comprising the same |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3759614A (en) * | 1971-02-10 | 1973-09-18 | Eastman Kodak Co | Dual photocell range finder apparatus |
| JPS51120725A (en) * | 1975-04-16 | 1976-10-22 | Sankyo Kogaku Kogyo Kk | Automatic forcusing camera |
| US4083056A (en) * | 1975-09-09 | 1978-04-04 | Asahi Kogaku Kogyo Kabushiki Kaisha | Focus detecting device for single-lens reflex cameras |
| JPS5262022A (en) * | 1975-11-17 | 1977-05-23 | Bell & Howell Co | Closed loop automatic focusing system |
| FR2396325A1 (en) * | 1977-07-01 | 1979-01-26 | Olympus Optical Co | Automatic focussing system for an optical instrument - assesses smoothness of brightness change between scanned adjacent image elements to produce control signal for optical system |
| JPS54155832A (en) * | 1978-05-30 | 1979-12-08 | Canon Inc | Focusing detector |
-
1981
- 1981-03-17 JP JP56038447A patent/JPS57154206A/en active Granted
-
1982
- 1982-02-26 CA CA000397160A patent/CA1173284A/en not_active Expired
- 1982-03-09 KR KR8201605A patent/KR890001454B1/en active
- 1982-03-10 FR FR8204034A patent/FR2502354B1/en not_active Expired
- 1982-03-15 AT AT0102382A patent/AT376813B/en not_active IP Right Cessation
- 1982-03-15 NL NL8201070A patent/NL8201070A/en not_active Application Discontinuation
- 1982-03-16 GB GB8207558A patent/GB2095505A/en not_active Withdrawn
- 1982-03-16 DE DE19823209517 patent/DE3209517A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| ATA102382A (en) | 1984-05-15 |
| DE3209517A1 (en) | 1982-10-14 |
| GB2095505A (en) | 1982-09-29 |
| KR830009501A (en) | 1983-12-21 |
| FR2502354B1 (en) | 1985-06-21 |
| AT376813B (en) | 1985-01-10 |
| KR890001454B1 (en) | 1989-05-03 |
| FR2502354A1 (en) | 1982-09-24 |
| JPS57154206A (en) | 1982-09-24 |
| JPH0526176B2 (en) | 1993-04-15 |
| NL8201070A (en) | 1982-10-18 |
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| MKEC | Expiry (correction) | ||
| MKEX | Expiry |