US20020093746A1 - Optical apparatus with optical system having long optical path - Google Patents
Optical apparatus with optical system having long optical path Download PDFInfo
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- US20020093746A1 US20020093746A1 US09/370,697 US37069799A US2002093746A1 US 20020093746 A1 US20020093746 A1 US 20020093746A1 US 37069799 A US37069799 A US 37069799A US 2002093746 A1 US2002093746 A1 US 2002093746A1
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- 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
- G02B7/30—Systems for automatic generation of focusing signals using parallactic triangle with a base line
- G02B7/32—Systems for automatic generation of focusing signals using parallactic triangle with a base line using active means, e.g. light emitter
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/04—Prisms
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- the present invention relates to an optical apparatus such as a camera, and particularly relates to an optical system thereof which has a lens, a prism, and the like.
- FIG. 1 is a view showing an optical relation among a photographing optical system, a light projecting lens (or a light emitting lens), a light receiving lens, and so on, of a camera which employs an active AF as a focussing device.
- An AF beam emitted from a light projecting element (or a light emitting element) such as a LED is reflected on an object (i.e. a subject to be photographed), and then is projected, or incident, upon a light receiving surface of a photo sensor (or a light receiving element) such as a PSD. Therefore, it is possible to know a position of center of gravity of light distributed over the light receiving surface, such as a distance from a left edge of the photo sensor to the position of center thereof.
- a relation between the position of center thereof and a distance “D” up to the object to be photographed i.e. a distance “D” between the object and the camera
- a formula which represents a relation between the position of center thereof and the distance “D” up to the object it is also possible to calculate the distance “D” up to the object by calculation, or operation, due to the position of center thereof.
- FIG. 2B shows a situation in which the AF beam is all projected on the object. That is, the horizontally elongate and shaded region in FIG. 2B shows a region on the object in which the AF beam is projected. In this case, all the projected AF beam is reflected on the object, and it is possible to measure the distance (i.e. to focus) up to the object with high accuracy.
- the width “dX” of the region on the photo sensor corresponding to the depth of field can be determined geometrically. Even if the center location of the light distributed on the photo sensor is deviated due to the “partial reflection”, the deviation is not a substantial problem as far as it exists within the region “dX”. Therefore, supposing that the resolution of the photo sensor is fixed or constant, the wider the “dX” becomes, the higher the accuracy of the distance measuring becomes substantially. As explained below, the “dX” can be represented by a formula including the focal length “fr” of the receiving lens.
- FORMULA 1 is established between a permissible circle of confusion (or a permissible derangement circle) and a depth of field, where the “F NO ” is a f-number of the photographing optical system, and the “n” is a permissible coefficient which can be determined optionally in compliance with a specific design (the “n” can be 0.333, for example).
- the photographing optical system is a zoom lens which is constituted by a pair of lens groups
- FIGS. 3A and 3B show this situation explanatorily.
- FIG. 3B illustrates a situation in which the focal length of the light projecting lens is relatively longer; therefore, the beam projected area is relatively smaller.
- FIG. 3A illustrates a situation in which the focal length of the light projecting lens is relatively shorter; therefore, the beam projected area is relatively larger.
- the light projecting lens is superior in the accuracy of the distance measuring if the focal length is relatively longer, similar to the light receiving lens which is superior in the accuracy of the distance measuring if the focal length is relatively longer.
- the spot photometric measurement is a photometric measurement in which an attention is paid to a specified narrow field of a photographing region. Therefore, it is necessary that the focal length of the AE photometric optical system is relatively long. Further, under a recent tendency in which the zoom lens has a high zooming rate, it is necessary to secure a longer focal length in the AE optical system in order to perform the spot photometric measurement with a higher magnification than the focal length in the conventional AE optical system.
- each optical system arranged in the optical apparatuses such as a camera has a longer focal length, in view of the accuracy of distance measuring and spot photometric measurement.
- the longer focal length in the optical system is contradictory to the necessity for thinnerization, or compactness, of camera.
- FIG. 4 is a cross section showing a main part of an optical unit in a conventional camera.
- a light projecting optical system (or a light emitting optical system) 20 and a light receiving optical system 30 , of an active AF are arranged on both sides of a unit body 11 , and a finder optical system 40 is arranged therebetween.
- the light projecting optical system 20 has a light projecting, or emitting, lens 21 and a light projecting, or emitting, element 22 .
- the light receiving optical system 30 has a light receiving lens 31 and a photo sensor 32 .
- the finder optical system 40 has a first objective lens 41 , a second objective lens 42 , a first prism 43 , a second prism 44 , and an eye piece (or an eye piece lens) 45 .
- the focal length of each of the light projecting optical system 20 and the light receiving optical system 30 of the active AF can not be beyond the thickness of the unit body 11 at its maximum. Namely, an increase of the focal length thereof brings a large size of the optical unit (which in turn brings a large size of camera having the optical unit).
- the reason why it is difficult to prevent the conventional optical unit from becoming large-sized, is that the light travelling in each of the optical systems 20 , 30 passes only in a straight direction without changing its direction therein.
- the length of the optical path in the finder optical system 40 is much longer than the thickness of the unit body 11 .
- the longer optical path length is attributed to an arrangement in which the light passing in the optical system 40 reflects on a plurality of reflecting surfaces 43 a , 44 a , 44 b of the first and second prisms 43 , 44 , and changes its direction.
- utilizing the reflection thereby in the optical system brings such a longer optical path without increasing the thickness of the optical unit.
- an additional reflection member, such as a prism in the light projecting optical system 20 and the light receiving optical system 30 , it leads rather a large-sized apparatus.
- each surface for reflecting light of the prism arranged in the conventional finder optical system 40 shown in FIG. 4 has an aluminum deposited film by vacuum evaporation, as a reflection element, which is formed by depositing aluminum on an outside surface of a body of the prism.
- a reflection element which is formed by depositing aluminum on an outside surface of a body of the prism.
- only one side of the aluminum deposited film i.e. only an inner surface thereof contacting the body of the prism
- an object of the present invention to provide an optical apparatus, such as a camera, having an optical system in which a relatively longer optical path is secured without hindering a thinnerization, or compactness, of the optical apparatus overall.
- an optical apparatus with a prism comprising: a first surface through which an incident light passes into a body of the prism; a second surface having an inner side by which the incident light is reflected into a reflection light within the body; and a third surface through which the reflection light is projected outside the body, wherein the prism is arranged such that an outer side of the second surface reflects light toward outside.
- the second surface may be provided with a reflection component.
- the reflection component for example, may be a metal deposited film or layer, such as an aluminum film or layer, which is deposited on the body of the prism.
- the reflection component for example, may be integrally formed with a part of the body of the prism.
- each of the inner side and the outer side of a single surface is employed as a surface for reflecting light.
- a single surface i.e. the second surface
- the optical unit is miniaturized, or becomes compact, which in turn makes it possible to make the optical apparatus with the optical unit thinner or compact overall.
- an optical apparatus with an optical element, the optical element comprising: a first surface having a first inner side and a first outer side; and a second surface having a second inner side and a second outer side, wherein an incident light which passes into a body of the optical element is reflected by the first inner side of the first surface and the second inner side of the second surface, into a reflection light which is projected outside the body, and wherein each of the first outer side of the first surface and the second outer side of the second surface reflects a light outside.
- FIG. 1 is an explanatory view showing an optical relation of a camera which is equipped with an active AF;
- FIGS. 2A and 2B are explanatory views explaining a conception of “partial reflection (or vignette)” of an AF beam projected;
- FIGS. 3A and 3B are explanatory views explaining a conception of “partial reflection (or vignette)” of an AF beam projected;
- FIG. 4 is a cross section of an optical unit of a conventional camera
- FIG. 5 is a cross section of an optical unit of a camera, as an optical apparatus, according to a first embodiment of the present invention
- FIG. 6 is a perspective view showing a unit body of the optical unit and a finder optical system therein shown in FIG. 5;
- FIG. 7 is a perspective view showing the unit body and an AE optical system therein shown in FIG. 5;
- FIG. 8 is a cross section of an optical unit of the camera, as the optical apparatus, according to a second embodiment of the present invention.
- FIG. 9 is a cross section of an optical unit of the camera, as the optical apparatus, according to a third embodiment of the present invention.
- FIG. 10 is a cross section of an optical unit of the camera, as the optical apparatus, according to a fourth embodiment of the present invention.
- FIG. 11 is a cross section of an optical unit of the camera, as the optical apparatus, according to a fifth embodiment of the present invention.
- FIG. 12 is a cross section of an optical unit of the camera, as the optical apparatus, according to a sixth embodiment of the present invention.
- FIG. 13 is a cross section of an optical unit of a binocular telescope, as the optical apparatus, according to a seventh embodiment of the present invention.
- FIG. 5 shows a cross section of a main part of the optical unit 100 of the camera.
- the optical unit 100 has an AE optical system 110 , a finder optical system 120 , and a passive AF unit 130 , which are integrally arranged in an unit body 101 .
- FIG. 6 shows an assembled state in which the finder optical system 120 is assembled to the unit body 101 , and it also shows a taken-out state in which the finder optical system 120 is taken out from the unit body 101 .
- FIG. 7 which is a perspective view, shows the unit body 101 , the AE optical system 110 , and the passive AE unit 130 .
- a first prism 123 which forms a part of the finder optical system 120 is shown, because an aluminum deposited film (or an aluminum deposited layer) is provided on a surface 123 a of the first prism 123 , and the surface 123 a not only forms the part of the finder optical system 120 , but also forms a part of the AE optical system 110 .
- an optical path in the finder optical system 120 is shown by a dashed line “A”
- an optical path in the AE optical system 110 is shown by a dashed line “B”. It can be understood that the light along the optical path “B” in the AE optical system 110 is totally reflected on an exposed side (i.e. an outer side) of the aluminum film deposited surface 123 a of the first prism 123 which is a component of the finder optical system 120 .
- a back side (i.e. inner side) of the aluminum film deposited surface 123 a is employed as a total reflecting surface in the finder optical system 120 .
- the aluminum deposited film itself has been conventionally well known, and it is made, or formed, by depositing aluminum by vacuum evaporation on a surface of a body of a prism. Different from a conventional art, however, both sides (i.e. outer side and inner side) of the aluminum film deposited surface 123 a are employed as reflecting surfaces.
- the exposed side (i.e. the outer side) of the aluminum film deposited surface 123 a is a face of the aluminum film which is open, or exposed, to environment
- the back side (i.e. the inner side) of the aluminum film deposited surface 123 a is a face of the aluminum film which contacts with an outer surface of a body of a prism.
- the surface on which the ray indicated by the arrow “B” falls is the exposed side of the aluminum film deposited surface 123 a ; on the other hand, the surface on which the ray indicated by the arrow “A” falls, is the back side thereof.
- the finder optical system 120 has a first objective lens 121 , a second objective lens 122 , the first prism 123 , a second prism 124 , and an eye piece lens 125 . Further, there is arranged a finder diaphragm 128 which is located between the first objective lens 121 and the second objective lens 122 . Still further, there is arranged a field pointing frame 129 which is located between the first prism 123 and the second prism 124 .
- the AE optical system 110 has a light receiving lens 111 , a reflex mirror 112 , and a photo sensor 113 , as shown in FIG. 7.
- FIG. 8 shows a cross section of a main part of the optical unit 200 of the camera.
- a light projecting, or emitting, optical system 220 and a light receiving optical system 230 of an active AF system are arranged on both sides of a unit body 201 .
- a finder optical system 210 is arranged between the light projecting optical system 220 and the light receiving optical system 230 .
- the light projecting optical system 220 has a light projecting, or emitting, lens 221 and a light projecting, or emitting, element 222 .
- the light receiving optical system 230 has a light receiving lens 231 and a photo sensor (or a light receiving element) 232 .
- the finder optical system 210 has a first objective lens 211 , a second objective lens 212 , a first prism 213 , a second prism 214 , and an eye piece lens 215 . Although each prism shown in FIG. 8 is formed by laminating some prism pieces, a prism integrally made of one single piece can also be employed.
- an aluminum deposited film is provided on a surface 214 a of the second prism 214 of the finder optical system 210 .
- the light travelling in the light receiving optical system 230 totally reflects towards the photo sensor 232 .
- the light travelling in the finder optical system 210 totally reflects towards the eyepiece lens 215 .
- the focal length in the active AF system is possible to be longer while the optical unit is compact; therefore, an accuracy in focussing is enhanced.
- FIG. 9 shows a cross section of a main part of the optical unit 300 of the camera.
- a light projecting optical system 310 and a light receiving optical system 340 of an active AF system are arranged on both sides of a unit body 301 .
- a finder optical system 320 which is located between the light projecting optical system 310 and the light receiving optical system 340 and which is located closer to the light projecting optical system 310 rather than to the light receiving optical system 340 .
- an AE optical system 330 which is located between the light projecting optical system 310 and the light receiving optical system 340 and which is located closer to the light receiving optical system 340 rather than to the light projecting optical system 310 .
- the light projecting optical system 310 has a light projecting lens 311 and a light projecting element 312 .
- the light receiving optical system 340 has a light receiving lens 341 , a reflex mirror 342 , and a photo sensor 343 .
- the finder optical system 320 has a first objective lens 321 , a second objective lens 322 , a first prism 323 , a second prism 324 , and an eye piece lens 325 .
- the AE optical system 330 has a light receiving lens 331 and a photo sensor 332 .
- a pair of aluminum film deposited surfaces 324 a , 324 b are formed on the second prism 324 of the finder optical system 320 . That is, the light travelling in the AE optical system 330 totally reflects on the outer side of one 324 a of pair of the aluminum film deposited surfaces towards the photo sensor 332 ; the light travelling in the finder optical system 320 totally reflects on the inner side of the other 324 b of the pair of the aluminum film deposited surfaces and then on the inner side of the one 324 a of the pair of aluminum film deposited surfaces towards the eye piece lens 325 ; and the light travelling in the light receiving optical system 340 totally reflects on the reflex mirror 342 and then on the outer side of the other 324 b of the pair of aluminum film deposited surfaces towards the photo sensor 343 .
- a pair of additional reflecting surfaces are available by providing the two aluminum film deposited surfaces, different from the conventional arrangement. Therefore, it is preferable that the film deposited surfaces are provided as many as possible.
- the focal length in the AE optical system is possible to be longer while the optical unit is compact; therefore, it is possible to realize a spot photometric measurement even in a zoom photographing with a higher magnification.
- FIG. 10 shows a cross section of a main part of the optical unit 400 of the camera.
- a light projecting optical system 410 and a light receiving optical system 420 of an active AF system are arranged on both sides of a unit body 401 .
- a finder optical system 430 is arranged between the light projecting optical system 410 and the light receiving optical system 420 .
- the light projecting optical system 410 has a light projecting lens 411 , a reflex mirror 412 , and a light projecting element 413 .
- the light receiving optical system 420 has a light receiving lens 420 and a photo sensor 422 .
- the finder optical system 430 has a first objective lens 431 , a second objective lens 432 , a first prism 433 , a second prism 434 , and an eye piece lens 435 .
- an aluminum deposited film is provided on a surface 433 a of the first prism 433 of the finder optical system 430 by vacuum evaporation.
- the light travelling in the light projecting optical system 410 totally reflects.
- the light travelling in the finder optical system 430 totally reflects.
- FIG. 11 shows a cross section of a main part of the optical unit 500 of the camera.
- a unit body 501 carries only a finder optical system 510 .
- This finder optical system 510 has a first objective lens 511 , a second objective lens 512 , a first prism 513 , a second prism 514 , an eye piece lens 515 , and a reflex mirror 518 .
- an aluminum deposited film is formed on a surface 514 a of the second prism 514 of the finder optical system.
- Both of an outer side of the aluminum film deposited surface 514 a and an inner side thereof serve as total reflecting surfaces in the finder optical system 510 as one optical system. That is, the aforementioned embodiments (i.e. the first through fourth embodiments) are different from this fifth embodiment in that the outer side and the inner side of each reflection member in the aforementioned embodiments serve as different reflecting surfaces in different optical systems.
- the reflection member has the same effect in that the optical path in each optical system can be made longer with it.
- FIG. 12 shows a cross section of a main part of the optical unit 600 of the camera.
- a unit body 601 carries a finder optical system 610 and an AE optical system 620 .
- the finder optical system 610 has a first objective lens 611 , a second objective lens 612 , a first prism 613 , a second prism 614 , an eye piece lens 615 , and a reflex mirror 618 .
- the AE optical system 620 has a light receiving lens 621 , a reflex mirror 622 , and a photo sensor 623 .
- a pair of reflection surfaces 614 a , 614 b are formed, like in the third embodiment shown in FIG. 9.
- the two reflection surfaces 614 a , 614 b have aluminum deposited films which are formed on different surfaces of the second prism 614 of the finder optical system 610 .
- the light travelling in the finder optical system 610 totally reflects on an outer side of one 614 a of the pair of film deposited surfaces 614 a , 614 b , then the reflected light is further reflected on an inner side of the other 614 b of the pair of film deposited surfaces, and then the reflected light is further reflected on an inner side of the one 614 a of the pair of film deposited surfaces towards the eye piece lens 615 . Meanwhile, the light travelling in the AE optical system 620 totally reflects on an outer side of the other 614 b of the pair of film deposited surfaces.
- the present invention is applied to a camera in which there is provided a finder (or viewfinder), independently of a photographing lens.
- a finder or viewfinder
- the present invention may be applied to a single-lens reflex camera.
- the present invention may be applied to any optical apparatus other than the camera.
- FIG. 13 the description is made below upon a binocular telescope, as the optical apparatus, with the optical unit, as a seventh embodiment, to which the present invention is applied.
- FIG. 13 shows a schematic cross section of the binocular telescope 700 .
- a pair of optical systems thereof are arranged on both sides (i.e. a right side and a is left side in the figure) in a relation of a mirror image with each other, relative to a center of a body of the binocular telescope. Therefore, an explanation thereof is made upon a right-hand optical system only.
- the optical system has a first objective lens 711 , a reflex mirror (or a reflection mirror) 712 , a second objective lens 713 , a first prism 714 , a second prism 715 , and a group of eye piece lenses 716 .
- a holder 717 which holds the group of eye piece lenses 716 is rotatably mounted on the body of the binocular telescope 700 , and it allows to perform a focussing operation.
- an aluminum deposited film is formed on a surface 715 a of the second prism 715 .
- the light travelling, or passing, in the optical system totally reflects on the outer side of the film deposited surface 715 a , and on the inner side thereof.
- the deposited film is employed to ensure a long optical path through which the light passes.
- the long optical path forming in the optical system makes it possible to realize a high magnification.
- the exposed side (i.e. outer side) of one surface of a prism and the back side (i.e. inner side) thereof are made use of as reflection surfaces.
- the aluminum deposited film is employed.
- the deposited film may be made of Ag (silver), Cr (chromium), Cu (copper), Au (gold), or the like, instead of employing the aluminum (Al).
- the deposited film or layer may be made as a dielectric multi-layered deposition film or layer.
- a plate-like reflex mirror instead of employing the deposited film or layer, a plate-like reflex mirror, both surfaces of which serve as reflection surfaces, may be employed.
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Abstract
Description
- This application is based on an application No. 10-225861 filed in Japan, the contents of which are hereby incorporated by reference.
- 1. Field of the Invention
- The present invention relates to an optical apparatus such as a camera, and particularly relates to an optical system thereof which has a lens, a prism, and the like.
- 2. Description of the Related Art
- Accompanying a miniaturization (or compactness, or thinnerization) of cameras which have been provided in recent years, there has been a tendency that a length in a direction of optical axis in an optical unit also becomes short. Under this tendency, it becomes difficult to arrange a light projecting/receiving optical system of an active AF, or an AE optical system, with a sufficient focal length. If the focal length of each of these optical systems is made relatively shorter, undesirable influences, such as a deterioration of precision in AF focussing, a difficulty in AE spot photometric measuring, and the like, may be brought to a camera performance.
- Firstly, a description is made below upon the deterioration, or lowering, of precision in the AF focussing.
- FIG. 1 is a view showing an optical relation among a photographing optical system, a light projecting lens (or a light emitting lens), a light receiving lens, and so on, of a camera which employs an active AF as a focussing device. An AF beam emitted from a light projecting element (or a light emitting element) such as a LED, is reflected on an object (i.e. a subject to be photographed), and then is projected, or incident, upon a light receiving surface of a photo sensor (or a light receiving element) such as a PSD. Therefore, it is possible to know a position of center of gravity of light distributed over the light receiving surface, such as a distance from a left edge of the photo sensor to the position of center thereof. Therefore, if a relation between the position of center thereof and a distance “D” up to the object to be photographed (i.e. a distance “D” between the object and the camera) is tabled, or memorized, beforehand, it is possible to calculate the distance “D” up to the object. Alternatively, if a formula which represents a relation between the position of center thereof and the distance “D” up to the object, it is also possible to calculate the distance “D” up to the object by calculation, or operation, due to the position of center thereof.
- The aforementioned table or formula is prepared on the assumption that all the projected AF beam returns to the photo sensor. That is, in order to accurately measure the distance with the aforementioned manner, it is necessary that all the projected AF beam returns to the photo sensor. FIG. 2B shows a situation in which the AF beam is all projected on the object. That is, the horizontally elongate and shaded region in FIG. 2B shows a region on the object in which the AF beam is projected. In this case, all the projected AF beam is reflected on the object, and it is possible to measure the distance (i.e. to focus) up to the object with high accuracy.
- Meanwhile, in FIG. 2A, only a part of the projected, or emitted, AF beam can hit the object. In this case, what reflects on the object is not all of the projected, or emitted, AF beam (hereinafter, this phenomenon is referred to as “partial reflection” or “vignette (or vignetting)”), and the accuracy of the distance measuring is naturally lowered or reduced. The degree of error of the distance measuring becomes larger as the degree of the vignette increases.
- Therefore, for the purpose of accurate distance measuring, it is preferable that there is no “partial reflection” at all. However, even if the “partial reflection”, or “vignetting”, occurs, and even if the actual location of the object and its focused location (namely, the distance up to the object measured by means of active AF) are not exactly coincide with each other as a result, the focussing error does not become a substantial problem as far as the object exists within a depth of field relative to the location thus focussed.
- Referring to FIG. 1, it can be understood that if the depth of field is “dL”, the width “dX” of the region on the photo sensor corresponding to the depth of field can be determined geometrically. Even if the center location of the light distributed on the photo sensor is deviated due to the “partial reflection”, the deviation is not a substantial problem as far as it exists within the region “dX”. Therefore, supposing that the resolution of the photo sensor is fixed or constant, the wider the “dX” becomes, the higher the accuracy of the distance measuring becomes substantially. As explained below, the “dX” can be represented by a formula including the focal length “fr” of the receiving lens.
- Generally, the following “
FORMULA 1” is established between a permissible circle of confusion (or a permissible derangement circle) and a depth of field, where the “FNO” is a f-number of the photographing optical system, and the “n” is a permissible coefficient which can be determined optionally in compliance with a specific design (the “n” can be 0.333, for example). - 1/L−1/(L+dL)=n·F no ·σ/ft 2 (FORMULA 1)
- On the other hand, from the geometrical relationship shown in FIG. 1, the following “FORMULA 2”, “FORMULA 3” and “
FORMULA 4” are established. - (L+dL):B=fr:X 1 (FORMULA 2)
- L:B=fr:X2 (FORMULA 3)
- dx=X 2 −X 1 (FORMULA 4)
- Elimination of X1 and X2 from the “
FORMULA 4”, using the “FORMULA 2” and “FORMULA 3”, brings a “FORMULA 5”, as follows. - dx=B·fr/L−B·fr/(L+dL)=B·fr·{1/L−1/(L+dL)}
- Finally, substitution of the “
FORMULA 1” into the “FORMULA 5” brings a “FORMULA 6” as follows. - dx=(n·F no ·σ·B·fr)/ft 2 (FORMULA 6)
- By the way, in the case that the photographing optical system is a zoom lens which is constituted by a pair of lens groups, the diameter of entrance pupil φ does not change, even if the magnification is changed by zooming. Therefore, using a relationship Fno=ft/φ, the “FORMULA 6” can also be expressed as a “
FORMULA 7” as follows. - dx=(n·σ·B·fr)/ft·φ (FORMULA 7)
- From the “FORMULA6” and “
FORMULA 7”, it can be understood that the “dX” is proportional to “fr”. That is, it can be understood that the longer the focal length “fr” of the light receiving lens becomes, the higher the accuracy of the distance measuring (i.e. the accuracy of focussing) becomes. - As to the focal length “fs” of the light projecting lens, the longer “fs” becomes, the higher the accuracy of the distance measuring becomes. Next, an explanation thereof is made below.
- That is, the shorter the focal length “fs” of the light projecting lens becomes, the projected, or emitted, AF beam diverges from the projecting lens or element with a relatively wider angle. As a result, the beam projected area on the object also becomes relatively larger, supposing that the distance to the object is fixed. FIGS. 3A and 3B show this situation explanatorily.
- Namely, FIG. 3B illustrates a situation in which the focal length of the light projecting lens is relatively longer; therefore, the beam projected area is relatively smaller. On the other hand, FIG. 3A illustrates a situation in which the focal length of the light projecting lens is relatively shorter; therefore, the beam projected area is relatively larger.
- As apparent from FIGS. 3A and 3B, if the beam projected area relative to the object is relatively larger, there increases the possibility that the aforementioned “partial reflection” occurs, so that the accuracy of the distance measuring becomes lower. In other words, the light projecting lens is superior in the accuracy of the distance measuring if the focal length is relatively longer, similar to the light receiving lens which is superior in the accuracy of the distance measuring if the focal length is relatively longer.
- Next, an explanation is made below upon a spot photometry (or spot photometric measurement).
- That is, the spot photometric measurement is a photometric measurement in which an attention is paid to a specified narrow field of a photographing region. Therefore, it is necessary that the focal length of the AE photometric optical system is relatively long. Further, under a recent tendency in which the zoom lens has a high zooming rate, it is necessary to secure a longer focal length in the AE optical system in order to perform the spot photometric measurement with a higher magnification than the focal length in the conventional AE optical system.
- As explained above, it is preferable that each optical system arranged in the optical apparatuses such as a camera has a longer focal length, in view of the accuracy of distance measuring and spot photometric measurement. However, the longer focal length in the optical system is contradictory to the necessity for thinnerization, or compactness, of camera. Next, an explanation thereof is made below with reference to FIG. 4.
- That is, FIG. 4 is a cross section showing a main part of an optical unit in a conventional camera. In the
optical unit 1, a light projecting optical system (or a light emitting optical system) 20 and a light receivingoptical system 30, of an active AF, are arranged on both sides of a unit body 11, and a finderoptical system 40 is arranged therebetween. - The light projecting
optical system 20 has a light projecting, or emitting,lens 21 and a light projecting, or emitting,element 22. The light receivingoptical system 30 has a light receiving lens 31 and a photo sensor 32. The finderoptical system 40 has a first objective lens 41, a secondobjective lens 42, a first prism 43, asecond prism 44, and an eye piece (or an eye piece lens) 45. - In the conventional optical unit typically as shown in FIG. 4, the focal length of each of the light projecting
optical system 20 and the light receivingoptical system 30 of the active AF, can not be beyond the thickness of the unit body 11 at its maximum. Namely, an increase of the focal length thereof brings a large size of the optical unit (which in turn brings a large size of camera having the optical unit). The reason why it is difficult to prevent the conventional optical unit from becoming large-sized, is that the light travelling in each of theoptical systems - On the other hand, paying attention to the finder
optical system 40, it can be understood that the length of the optical path in the finderoptical system 40 is much longer than the thickness of the unit body 11. The longer optical path length is attributed to an arrangement in which the light passing in theoptical system 40 reflects on a plurality of reflectingsurfaces second prisms 43, 44, and changes its direction. In other words, utilizing the reflection thereby in the optical system brings such a longer optical path without increasing the thickness of the optical unit. However, if there is arranged an additional reflection member, such as a prism, in the light projectingoptical system 20 and the light receivingoptical system 30, it leads rather a large-sized apparatus. - It is to be noted that each surface for reflecting light of the prism arranged in the conventional finder
optical system 40 shown in FIG. 4 has an aluminum deposited film by vacuum evaporation, as a reflection element, which is formed by depositing aluminum on an outside surface of a body of the prism. As shown in the figure, only one side of the aluminum deposited film (i.e. only an inner surface thereof contacting the body of the prism) is employed as a surface for reflecting light. - Therefore, it is an object of the present invention to provide an optical apparatus, such as a camera, having an optical system in which a relatively longer optical path is secured without hindering a thinnerization, or compactness, of the optical apparatus overall.
- In order to accomplish the above object, according to one aspect of the present invention, there is provided an optical apparatus with a prism, the prism comprising: a first surface through which an incident light passes into a body of the prism; a second surface having an inner side by which the incident light is reflected into a reflection light within the body; and a third surface through which the reflection light is projected outside the body, wherein the prism is arranged such that an outer side of the second surface reflects light toward outside.
- In the mechanism, the second surface may be provided with a reflection component. The reflection component, for example, may be a metal deposited film or layer, such as an aluminum film or layer, which is deposited on the body of the prism. Alternatively, the reflection component, for example, may be integrally formed with a part of the body of the prism.
- According to the mechanism, each of the inner side and the outer side of a single surface (i.e. the second surface) is employed as a surface for reflecting light. Namely, there exist a pair of surfaces for reflecting light per single surface. Therefore, according to the mechanism, in contrast with the aforementioned conventional mechanism in which only the inner surface (i.e. inner side) of the reflection element is employed as a surface for reflecting light, and in which the outer surface (i.e. outer side) of the reflection element is not employed as a surface for reflecting light, it is possible to secure a longer optical path, relative to the same size of an optical unit. In other words, according to the mechanism of the one aspect of the present invention, if the length of optical path is the same in contrast with the conventional mechanism, the optical unit is miniaturized, or becomes compact, which in turn makes it possible to make the optical apparatus with the optical unit thinner or compact overall.
- According to another aspect of the present invention, there is provided an optical apparatus with an optical element, the optical element comprising: a first surface having a first inner side and a first outer side; and a second surface having a second inner side and a second outer side, wherein an incident light which passes into a body of the optical element is reflected by the first inner side of the first surface and the second inner side of the second surface, into a reflection light which is projected outside the body, and wherein each of the first outer side of the first surface and the second outer side of the second surface reflects a light outside.
- This and other objects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which:
- FIG. 1 is an explanatory view showing an optical relation of a camera which is equipped with an active AF;
- FIGS. 2A and 2B are explanatory views explaining a conception of “partial reflection (or vignette)” of an AF beam projected;
- FIGS. 3A and 3B are explanatory views explaining a conception of “partial reflection (or vignette)” of an AF beam projected;
- FIG. 4 is a cross section of an optical unit of a conventional camera;
- FIG. 5 is a cross section of an optical unit of a camera, as an optical apparatus, according to a first embodiment of the present invention;
- FIG. 6 is a perspective view showing a unit body of the optical unit and a finder optical system therein shown in FIG. 5;
- FIG. 7 is a perspective view showing the unit body and an AE optical system therein shown in FIG. 5;
- FIG. 8 is a cross section of an optical unit of the camera, as the optical apparatus, according to a second embodiment of the present invention;
- FIG. 9 is a cross section of an optical unit of the camera, as the optical apparatus, according to a third embodiment of the present invention;
- FIG. 10 is a cross section of an optical unit of the camera, as the optical apparatus, according to a fourth embodiment of the present invention;
- FIG. 11 is a cross section of an optical unit of the camera, as the optical apparatus, according to a fifth embodiment of the present invention;
- FIG. 12 is a cross section of an optical unit of the camera, as the optical apparatus, according to a sixth embodiment of the present invention; and
- FIG. 13 is a cross section of an optical unit of a binocular telescope, as the optical apparatus, according to a seventh embodiment of the present invention.
- Before a description of the preferred embodiments proceeds, it is to be noted that like or corresponding parts are designated by like reference numerals throughout the accompanying drawings.
- With reference to FIGS. 5 through 13, the description is made below upon a camera or a binocular telescope, as an optical apparatus, with an optical unit including at least one optical system, according to each of seven embodiments of the present invention.
- First, with reference to FIGS. 5 through 7, the description is made below upon the camera with the optical unit according to a first embodiment of the present invention.
- FIG. 5 shows a cross section of a main part of the
optical unit 100 of the camera. Theoptical unit 100 has an AEoptical system 110, a finderoptical system 120, and apassive AF unit 130, which are integrally arranged in anunit body 101. - For a better understanding of FIG. 5, the
unit body 101 and the finderoptical system 120 are shown in FIG. 6 which is a perspective view thereof. FIG. 6 shows an assembled state in which the finderoptical system 120 is assembled to theunit body 101, and it also shows a taken-out state in which the finderoptical system 120 is taken out from theunit body 101. Meanwhile, FIG. 7, which is a perspective view, shows theunit body 101, the AEoptical system 110, and thepassive AE unit 130. In FIG. 7, although the finderoptical system 120 is not shown, afirst prism 123 which forms a part of the finderoptical system 120 is shown, because an aluminum deposited film (or an aluminum deposited layer) is provided on asurface 123 a of thefirst prism 123, and thesurface 123 a not only forms the part of the finderoptical system 120, but also forms a part of the AEoptical system 110. - In FIG. 7, an optical path in the finder
optical system 120 is shown by a dashed line “A”, and an optical path in the AEoptical system 110 is shown by a dashed line “B”. It can be understood that the light along the optical path “B” in the AEoptical system 110 is totally reflected on an exposed side (i.e. an outer side) of the aluminum film depositedsurface 123 a of thefirst prism 123 which is a component of the finderoptical system 120. In this arrangement, a back side (i.e. inner side) of the aluminum film depositedsurface 123 a is employed as a total reflecting surface in the finderoptical system 120. - The aluminum deposited film itself has been conventionally well known, and it is made, or formed, by depositing aluminum by vacuum evaporation on a surface of a body of a prism. Different from a conventional art, however, both sides (i.e. outer side and inner side) of the aluminum film deposited
surface 123 a are employed as reflecting surfaces. - In this specification, the exposed side (i.e. the outer side) of the aluminum film deposited
surface 123 a is a face of the aluminum film which is open, or exposed, to environment, and the back side (i.e. the inner side) of the aluminum film depositedsurface 123 a is a face of the aluminum film which contacts with an outer surface of a body of a prism. In FIG. 7, the surface on which the ray indicated by the arrow “B” falls, is the exposed side of the aluminum film depositedsurface 123 a; on the other hand, the surface on which the ray indicated by the arrow “A” falls, is the back side thereof. Namely, there exist a pair of reflecting surfaces per a surface of the prism, which is the aluminum film depositedsurface 123 a in the first embodiment. - As shown in FIGS. 5 and 6, the finder
optical system 120 has a firstobjective lens 121, a secondobjective lens 122, thefirst prism 123, asecond prism 124, and aneye piece lens 125. Further, there is arranged afinder diaphragm 128 which is located between the firstobjective lens 121 and the secondobjective lens 122. Still further, there is arranged afield pointing frame 129 which is located between thefirst prism 123 and thesecond prism 124. - Meanwhile, the AE
optical system 110 has a light receiving lens 111, areflex mirror 112, and aphoto sensor 113, as shown in FIG. 7. - Next, with reference to FIG. 8, the description is made below upon the camera with the optical unit according to a second embodiment of the present invention.
- That is, FIG. 8 shows a cross section of a main part of the
optical unit 200 of the camera. In theoptical unit 200, a light projecting, or emitting,optical system 220 and a light receivingoptical system 230 of an active AF system are arranged on both sides of aunit body 201. A finder optical system 210 is arranged between the light projectingoptical system 220 and the light receivingoptical system 230. - The light projecting
optical system 220 has a light projecting, or emitting,lens 221 and a light projecting, or emitting,element 222. The light receivingoptical system 230 has a light receiving lens 231 and a photo sensor (or a light receiving element) 232. The finder optical system 210 has a first objective lens 211, a secondobjective lens 212, a first prism 213, asecond prism 214, and aneye piece lens 215. Although each prism shown in FIG. 8 is formed by laminating some prism pieces, a prism integrally made of one single piece can also be employed. - In the second embodiment shown in FIG. 8, an aluminum deposited film is provided on a surface214 a of the
second prism 214 of the finder optical system 210. On an outer side of the film deposited surface 214 a, the light travelling in the light receivingoptical system 230 totally reflects towards thephoto sensor 232. On the other hand, on an inner side of the film deposited surface 214 a, the light travelling in the finder optical system 210 totally reflects towards theeyepiece lens 215. - According to the second embodiment, the focal length in the active AF system is possible to be longer while the optical unit is compact; therefore, an accuracy in focussing is enhanced.
- Next, with reference to FIG. 9, the description is made below upon the camera with the optical unit according to a third embodiment of the present invention.
- That is, FIG. 9 shows a cross section of a main part of the
optical unit 300 of the camera. In theoptical unit 300, a light projectingoptical system 310 and a light receivingoptical system 340 of an active AF system are arranged on both sides of aunit body 301. There is arranged a finderoptical system 320 which is located between the light projectingoptical system 310 and the light receivingoptical system 340 and which is located closer to the light projectingoptical system 310 rather than to the light receivingoptical system 340. There is also arranged an AEoptical system 330 which is located between the light projectingoptical system 310 and the light receivingoptical system 340 and which is located closer to the light receivingoptical system 340 rather than to the light projectingoptical system 310. - The reason why the light projecting
optical system 310 and the light receivingoptical system 340 are located with a maximum space therebetween, is to make the longest a distance therebetween in a base length direction which is parpendicular to a direction (i.e. a reference length: refer to FIG. 1) of its optical axis. With this arrangement, it is possible to enhance a precision of the AF operation of the camera. - The light projecting
optical system 310 has alight projecting lens 311 and alight projecting element 312. The light receivingoptical system 340 has alight receiving lens 341, areflex mirror 342, and aphoto sensor 343. The finderoptical system 320 has a firstobjective lens 321, a secondobjective lens 322, afirst prism 323, asecond prism 324, and aneye piece lens 325. The AEoptical system 330 has alight receiving lens 331 and aphoto sensor 332. Although each prism shown in FIG. 9 is formed by laminating some prism pieces, a prism integrally made of one single piece can also be employed. - In the third embodiment shown in FIG. 9, a pair of aluminum film deposited
surfaces 324 a, 324 b are formed on thesecond prism 324 of the finderoptical system 320. That is, the light travelling in the AEoptical system 330 totally reflects on the outer side of one 324 a of pair of the aluminum film deposited surfaces towards thephoto sensor 332; the light travelling in the finderoptical system 320 totally reflects on the inner side of the other 324 b of the pair of the aluminum film deposited surfaces and then on the inner side of the one 324 a of the pair of aluminum film deposited surfaces towards theeye piece lens 325; and the light travelling in the light receivingoptical system 340 totally reflects on thereflex mirror 342 and then on the outer side of the other 324 b of the pair of aluminum film deposited surfaces towards thephoto sensor 343. - As can be understood from this third embodiment, a pair of additional reflecting surfaces are available by providing the two aluminum film deposited surfaces, different from the conventional arrangement. Therefore, it is preferable that the film deposited surfaces are provided as many as possible.
- According to the third embodiment, the focal length in the AE optical system is possible to be longer while the optical unit is compact; therefore, it is possible to realize a spot photometric measurement even in a zoom photographing with a higher magnification.
- Next, with reference to FIG. 10, the description is made below upon the camera with the optical unit according to a fourth embodiment of the present invention.
- That is, FIG. 10 shows a cross section of a main part of the
optical unit 400 of the camera. In theoptical unit 400, a light projectingoptical system 410 and a light receivingoptical system 420 of an active AF system are arranged on both sides of aunit body 401. A finderoptical system 430 is arranged between the light projectingoptical system 410 and the light receivingoptical system 420. - The light projecting
optical system 410 has alight projecting lens 411, areflex mirror 412, and alight projecting element 413. The light receivingoptical system 420 has alight receiving lens 420 and a photo sensor 422. The finderoptical system 430 has a firstobjective lens 431, a secondobjective lens 432, afirst prism 433, asecond prism 434, and aneye piece lens 435. - In the fourth embodiment shown in FIG. 10, an aluminum deposited film is provided on a surface433 a of the
first prism 433 of the finderoptical system 430 by vacuum evaporation. On an outer side of the film deposited surface 433 a, the light travelling in the light projectingoptical system 410 totally reflects. On an inner side of the film deposited surface 433 a, the light travelling in the finderoptical system 430 totally reflects. - Next, with reference to FIG. 11, the description is made below upon the camera with the optical unit according to a fifth embodiment of the present invention.
- That is, FIG. 11 shows a cross section of a main part of the
optical unit 500 of the camera. In theoptical unit 500, aunit body 501 carries only a finderoptical system 510. This finderoptical system 510 has a firstobjective lens 511, a secondobjective lens 512, afirst prism 513, asecond prism 514, aneye piece lens 515, and areflex mirror 518. - In the fifth embodiment, an aluminum deposited film is formed on a
surface 514 a of thesecond prism 514 of the finder optical system. Both of an outer side of the aluminum film depositedsurface 514 a and an inner side thereof serve as total reflecting surfaces in the finderoptical system 510 as one optical system. That is, the aforementioned embodiments (i.e. the first through fourth embodiments) are different from this fifth embodiment in that the outer side and the inner side of each reflection member in the aforementioned embodiments serve as different reflecting surfaces in different optical systems. However, through all the aforementioned embodiments (i.e. the first through fifth embodiments), the reflection member has the same effect in that the optical path in each optical system can be made longer with it. - Next, with reference to FIG. 12, the description is made below upon the camera with the optical unit according to a sixth embodiment of the present invention.
- That is, FIG. 12 shows a cross section of a main part of the
optical unit 600 of the camera. In theoptical unit 600, aunit body 601 carries a finderoptical system 610 and an AE optical system 620. The finderoptical system 610 has a firstobjective lens 611, a secondobjective lens 612, afirst prism 613, asecond prism 614, aneye piece lens 615, and areflex mirror 618. The AE optical system 620 has a light receiving lens 621, areflex mirror 622, and aphoto sensor 623. - In the embodiment shown in FIG. 12, a pair of reflection surfaces614 a, 614 b are formed, like in the third embodiment shown in FIG. 9. The two
reflection surfaces 614 a, 614 b have aluminum deposited films which are formed on different surfaces of thesecond prism 614 of the finderoptical system 610. The light travelling in the finderoptical system 610 totally reflects on an outer side of one 614 a of the pair of film depositedsurfaces 614 a, 614 b, then the reflected light is further reflected on an inner side of the other 614 b of the pair of film deposited surfaces, and then the reflected light is further reflected on an inner side of the one 614 a of the pair of film deposited surfaces towards theeye piece lens 615. Meanwhile, the light travelling in the AE optical system 620 totally reflects on an outer side of the other 614 b of the pair of film deposited surfaces. - In each of the above embodiments, the present invention is applied to a camera in which there is provided a finder (or viewfinder), independently of a photographing lens. However, it is needless to say that the present invention may be applied to a single-lens reflex camera. Also, it is needless to say that the present invention may be applied to any optical apparatus other than the camera. Next, with reference to FIG. 13, the description is made below upon a binocular telescope, as the optical apparatus, with the optical unit, as a seventh embodiment, to which the present invention is applied.
- That is, FIG. 13 shows a schematic cross section of the
binocular telescope 700. A pair of optical systems thereof are arranged on both sides (i.e. a right side and a is left side in the figure) in a relation of a mirror image with each other, relative to a center of a body of the binocular telescope. Therefore, an explanation thereof is made upon a right-hand optical system only. - The optical system has a first
objective lens 711, a reflex mirror (or a reflection mirror) 712, a secondobjective lens 713, afirst prism 714, asecond prism 715, and a group ofeye piece lenses 716. Aholder 717 which holds the group ofeye piece lenses 716, is rotatably mounted on the body of thebinocular telescope 700, and it allows to perform a focussing operation. - In the embodiment shown in FIG. 13, an aluminum deposited film is formed on a
surface 715 a of thesecond prism 715. The light travelling, or passing, in the optical system totally reflects on the outer side of the film depositedsurface 715 a, and on the inner side thereof. Namely, the deposited film is employed to ensure a long optical path through which the light passes. The long optical path forming in the optical system, makes it possible to realize a high magnification. - Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are also apparent to those skilled in the art. The essence of the present invention is that the exposed side (i.e. outer side) of one surface of a prism and the back side (i.e. inner side) thereof are made use of as reflection surfaces. For example, in the aforementioned embodiments, the aluminum deposited film is employed. Alternatively, the deposited film may be made of Ag (silver), Cr (chromium), Cu (copper), Au (gold), or the like, instead of employing the aluminum (Al).
- Alternatively, the deposited film or layer may be made as a dielectric multi-layered deposition film or layer.
- Further, instead of employing the deposited film or layer, a plate-like reflex mirror, both surfaces of which serve as reflection surfaces, may be employed.
- Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.
Claims (12)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP10-225861 | 1998-08-10 | ||
JP10225861A JP2000056380A (en) | 1998-08-10 | 1998-08-10 | Optical device |
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US20020093746A1 true US20020093746A1 (en) | 2002-07-18 |
US6441977B1 US6441977B1 (en) | 2002-08-27 |
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US09/370,697 Expired - Lifetime US6441977B1 (en) | 1998-08-10 | 1999-08-09 | Optical apparatus with optical system having long optical path |
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US6721044B2 (en) * | 2001-01-30 | 2004-04-13 | Seknoic Corporation | Exposure meter used for photographing |
US7253833B2 (en) | 2001-11-16 | 2007-08-07 | Autonetworks Technologies, Ltd. | Vehicle periphery visual recognition system, camera and vehicle periphery monitoring apparatus and vehicle periphery monitoring system |
JP4576175B2 (en) * | 2004-08-10 | 2010-11-04 | Hoya株式会社 | Digital camera |
KR100612863B1 (en) * | 2004-10-11 | 2006-08-14 | 삼성전자주식회사 | Apparatus and method for measuring fat |
JP2015137987A (en) * | 2014-01-24 | 2015-07-30 | アズビル株式会社 | Distance sensor and distance measurement method |
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JPH02234139A (en) * | 1989-03-08 | 1990-09-17 | Olympus Optical Co Ltd | Real-image type finder for eye level and waist level |
JPH05187832A (en) | 1992-01-10 | 1993-07-27 | Kubota Corp | Measuring instrument |
JPH06202200A (en) * | 1993-01-07 | 1994-07-22 | Minolta Camera Co Ltd | Camera |
JPH0743781A (en) * | 1993-07-30 | 1995-02-14 | Olympus Optical Co Ltd | Finder device for camera |
JP3368561B2 (en) * | 1993-10-28 | 2003-01-20 | オリンパス光学工業株式会社 | Real-image finder optical system with photometric function |
JPH08297203A (en) | 1995-04-27 | 1996-11-12 | Matsushita Electric Ind Co Ltd | Optical prism for color separation |
US6058273A (en) * | 1997-03-05 | 2000-05-02 | Asahi Kogaku Kogyo Kabushiki Kaisha | Real-image type viewfinder |
JPH11258681A (en) * | 1998-03-16 | 1999-09-24 | Olympus Optical Co Ltd | Finder equipped with display device |
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- 1998-08-10 JP JP10225861A patent/JP2000056380A/en active Pending
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1999
- 1999-08-09 US US09/370,697 patent/US6441977B1/en not_active Expired - Lifetime
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