CA1132384A - Virtual image display apparatus - Google Patents
Virtual image display apparatusInfo
- Publication number
- CA1132384A CA1132384A CA353,223A CA353223A CA1132384A CA 1132384 A CA1132384 A CA 1132384A CA 353223 A CA353223 A CA 353223A CA 1132384 A CA1132384 A CA 1132384A
- Authority
- CA
- Canada
- Prior art keywords
- mirror
- image display
- virtual image
- image source
- display apparatus
- 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
Abstract
ABSTRACT OF THE DISCLOSURE
A virtual image display device for alpha-numeric and pictorial information. A concave spherical mirror segment magnifies and reflects an image from an image source. The image source is mounted between the focus of the mirror and the said mirror and parallel to its optical axis. The mirror segment is located substantially on the same side of the opti-cal axis as the image source. In this fashion an observer positioned on the same side of the optical axis as the mirror segment and the image display face can observe a substantially distortion free image, that is to say the formed visual image is visible to the viewer in front of the mirror. In related embodiments, the concave mirror segment can be made partially reflective and placed in front of a camera lens to allow a camera to photograph through it. A planar mirror can also be included to fold the light path of the display and thereby reduce the size of the apparatus.
A virtual image display device for alpha-numeric and pictorial information. A concave spherical mirror segment magnifies and reflects an image from an image source. The image source is mounted between the focus of the mirror and the said mirror and parallel to its optical axis. The mirror segment is located substantially on the same side of the opti-cal axis as the image source. In this fashion an observer positioned on the same side of the optical axis as the mirror segment and the image display face can observe a substantially distortion free image, that is to say the formed visual image is visible to the viewer in front of the mirror. In related embodiments, the concave mirror segment can be made partially reflective and placed in front of a camera lens to allow a camera to photograph through it. A planar mirror can also be included to fold the light path of the display and thereby reduce the size of the apparatus.
Description
3Z3~34 This invention is a device for displaying alpha-numeric and pictorial information in an enlar~ed format. ~uch a device has utility as an advertisin~ disPlay panel, a prom~tin~ device, closed circuit television display or photo~raphic projector. It can also be used in place of other apparatus commonly used for imaging texts and pictures.
Visihle displays have been produced in the prior art bY
pro~lecting an ima~e, often termed n "real lma~e," on a 9Creen.
Since the ima~e is formed on the screen surface, its siæe i8 limited to that of the screen itself. This real ima~e appears to ~row smaller, an~ therefore, more difficult to see, as a viewer' distance from the screen increases. Real images on a screen are also degraded by ambient li~,ht.
Where visual information is produced for prompting purposes, the screen must display enough words for a performer to read his script comfortably. It is often difficult to use characters lar~e enough so that they can be read from a distance and still fit on the small cathode ray screens currently in use. Moreover, such ~resent day displays cannot be enlarged r~adily.
Airlines also use closed circuit television svstems in their terminals to make fli~ht in~ormation available to their passen~ers.
These screens too must show so much information on a small area that chey ere difficult to read from e distance.
'~
¦ The present invention overcomes many of the difficulties with ¦ prior are devices by producin~ a magnified virtual ima~e display.
The virtual image, created bv its concave mirror, is more readily shielded from than /ambient light t are real image displays. Unlike prior art ¦ devices employing flat mirrors, the curved virtual image apparatus can ma~nify its displa~ so that it can be read at a distance.
The de~ree of ma~nification can be varied readily if desired.
Another oblect of the present invention is to provide a means for viewing information in front of a photographic or television camera for prompting purposes. In this embodiment, the virtual Lmage display apparatus will provide a script for a performer that he can read in a studio while he is looking directlY at the camera.
Still another ob~ect of the present invention is to provide a ~rompting device which can be used outdoors or in the presence ~r '~I~h lev~l~ Or ~D~c~ IL~hr 113Z3F~4 SUMMA~Y OF THE INVENTION
According to the present invention, a virtual image display apparatus comprises a mirror in the shape of a substan-tially concave segment of a hemisphere said spherical mirror having an optical axis and a focus, an image source means for said mirror segment, and an image display face on said image source disposed substantially perpendicular to said optical axis but located off said axis and between said focus and said mirror segment, said mirror segment being located substantially on the same si.de of the said optical axis as the image source, whereby an observer positioned on the same side of the optical axis as the mirror segment and the image display face can observe a substantially distortion free image.
The following is a description by way of example of certain embodiments of the present invention.
Z3~4 ~ DESCRIPTION OF THE DRAWINGS
I _ . _ In the accompanying drawings formin~ a part hereof, similar parts have been given identical reference numerals, in which drawings:
Figure 1 is a somewhat diagrammatic side view, partially in ~ection,of one complete embodiment of the present invention.
Fi~,ure 2 is a somewhat diagram~atic side view of another embodiment o~ the present invention Figure 3 is a somewhat isometric view, partiallY brolcen away, cf another complete embodiment of the present invention useful for prompting.
Figure 4 is a diagrammatic view, partially in sectio~ of the embodiment shown in Fi~ure 3 illustratin~ the various light paths.
Figure 5 is a somewhat diagramatic side view, partially in section, of still another embodiment of the present invention.
~'igure 6 is a view similar to Figure 5 showing a further embodiment of the invention.
' 3 13Z3~4 , ~ ` , DETAILED DESCRIPTION
Referring to the drawings, and Figure 1 in particular, 10 indicates one complete embodiment of a virtual image display device made in accordance with the present invention.
Il Said embodiment is particularly well suited for large format 5 1I displays in airline terminal~, train stations, and other places where information must be read easily at a distance.
The virtual image display device 10 comprises an information pro~ection device 11, hereinafter referred to as an image Il source, and a curved mirror segment 14 to receive li~ht from I said pro~ection device. The image source illustrated at 11 is intended to depict a cathode ray tube 12, a thin film electroluminescent display, a liquid crystal display-rear or front illuminated, an illuminated film, a light emitting il diode array, electroluminescent panel, filament lamp, gaseous ~ plasma discharge cell or analogous unit. The image source 11 iY mounted in an enclosure 13 and its image display face 30 ls substantially normal to the optical axis 16a and is preferably shielded from ambient light by said enclosure.
~ In the present embodiment, the image source 11 i~ ~uspended from the ceiling of a room, but other supports may be used to suit the location of the image ~ource apparatus.
., . ~
,1 11;~2;384 The lmage source 11 i~ directed at a concave spherical mirror segment as used herein is intended to mean a concave ~portion of a larger hemispherical mirror structure indicated llby dashed lines 14a in Figure 1. Mirror segment 14 is held l~tationary at ~ome predetermined distance below and in front of image source 11 as by bracket 15.
In the embodiment shown in Figure 1, mirror segment 14 is l fully aluminized, preferably front surface. It ma8nifies the !1 image received from the image source 11 and reflects it lltoward the viewers 29 located at some distance below and ~behind enclo~u~es 13. The viewers 29 are represented by the ! schematic eye 29.
l Every concave spherical mirror ha~ a focus and an I optical axis. Said focus is always located at some distance ,lin front of the mirror and on lts axis. Rays paralell and close to the optical axis directed at the surface of the concave mirror concerge near or at its focus. Any ob;ect placed between the f~cus and the concave mirror will appear to be l~ma~nified when viewed by one standing somewhere behind the l~focus. The closer the obJect is located to the focus, the more it will be magnified. The ob~ect reflected by the concave mirror will also appear to the viewer as if it is loca ted s 0mewhe re behind the sur f ace o f the mLrror i ts el f .
~¦ ~13Z3B4 i i This reflection is commonly called a virtual image.
In Figure 1, the optical axis of the mirror 14a is designated by the line 16a. The focus of mirror 14a is the Il point 16b. The image source 11 is positioned between said S Ij focus 16b and the mirror 14a to magnify its display. Mirror segment 14 i8 mounted below the axis 16a so that the display I it reflects i9 not partially blocked from view by the image source 11 and its enclosure 13. Since image source 11 I radiated light out over a wide angular range in front of it, ¦ it i8 possible for mirror segment 14 to be positioned below Il its own axis and yet reflect a portion of this light to the ¦I viewer 29. This reflected portion constitutes the desired ! display of the present invention. The light rays drawn in l~ Figure 1 show how this so-called off axis projection technique 15 ll picks up a portion of the light that image source 11 emits and reflects it toward the viewer 25. Said viewer sees the display from the image source 11 as an enlarged virtual image Il 16c appearing to exist behind mirror segment 14.
Il Figure 2 shows another embodiment of the present invention l in which the virtual ima~e display apparatus is used as a ¦I prompting device. The viewer 29 may be at some distance in ,I front of a movie or television camera 18 mouneed upon a support 20. This schematic figure again shows a cathode ray tube 12 image source directing a display such as a script on to mirror segment 17. Unllke mirror segment 14, used in the .
l. ~
1~32384 l ( first embodiment of this invention, mirror segment 17 is only partially reflective. Mirror segment 17 is surfaced so that typically 70 to 80% of the incident light enters Il camera lens 19 after passing through said mirror segment 17.
; At the same time, mirror segment 17 allows 30 to 20% respect-Il ively of the light coming from the image source 11 to be reflected to the viewer 29. The placement of the image source 11 outside of the field of view of the recording camera (indicated I by lines 12a) prevents said camera from receiving the display l¦ being projected by image source 11. Image source 11 uses a ,~ sufficiently intense light so that the viewer 29 can still read the reflected display coming from the 20 to 30% of the light from the mirror se~ment 17. The remaining 70 to 80% of the , light from image source 11 is wasted. The 20 to 30% decrease ll in brightness of the scene that camera 18 is recording, similarly, is not sufficient to di~rupt its proper functioning.
` Coating mirror segment 17 with ~ilver, aluminum, or '~ other reflective substances to reflect and transmit light in ~ the above described manner is accomplished by techniques well ~I knowm in the art and comprise no part of the present invention.
Figures 3 and 4 illustrate a third embodiment of the present invention~ This embodiment is similar to Figure 1 except that the light path of the di~play reflected from mirror Il se~ment 14 is folded once before it is directed to the viewer 29.
" Foldlng the light path allows the components of the virtual ., I
''' I
.
., I
, . , .. I
g image display appsratus 10 to be re clo5ely arranged in front of a recording camera 18. A partially reflective plannar ;'mlrror 22 i~ here used to fold the light path. The apparatus ~;of Figure 3 is contained in a housing 23 having a top 24, bottom 25, spaced sides 26a and b, and back 27. The front 1 of housing 23 is open.
i Figure 4 shows the arran~ement of each of the optical components in the embodiment of Figure 3. The image source 11 is again mounted with its image display face 30 substsntially llperpendicular to the optical acis 16a of soherical mirror segment ~ 14. Image source 11 is placed inside the focus 16b of mirror ,segment 14 so that its display is magnified by sa~d mirror.
IA small baffle 21, mounted on one edge of the image source 11, ,prevents the viewer from being distracted ~ light radiating , from the edge of the image source's display face 30.
l, Mirror segment 14 is unted off its own optical axis a as described in previous embodiments. Image source 11 is also mounted off the axis 16a. Mirror seg~ent 14 is fully reflective so that it transmits all the light it receives from l,source 11 toward planar mirror 22. Planar mirror 22 is mounted 2Q 11 in front of camera lens 19. Mirror 22 is coated to have its front surface partially reflective such as, for example, ~mirror segment 17 described in the second embodiment of this invention.
Il As noted above, the degree to which a spherical mirror will i~magnify an object placed before it depends upon its location: j ,, . I
1. 1 ,~ I
. .
I
113Z3~4 Il - 10 -I The closer the object is placed to the mirror's focus, the I more the mirror will magnify its virtual image. Applying this principal to each of the three above described embodlments, I it becomes apparent that moving the image source 11 toward focus 16b will increase the magnification of the virtual image display. Moving the source 11 away from the focus 16b decreases the size of the virtual image. Experimentation shows that the image source 11 must be moved along a line ~ which passes through the focus 16b of mirror segment 14, ~ at an angle 0 with respect to, axis 16a such that tan ~ ~ h , where h equals the distance from the center of the image source's display face 30 normal 16a;l ¦ f,l. equals the foval length of the mirror segment 14 ~the ¦ distance from the optical center 16d of mirror segment 14 ¦ to point 16b as measured along axis 16a) and 8 equals the distance from the point 16e where line he intersects axis 16a ! to the center 16d of mirror segment 14 measured along axis 16a l so that the virtual image of image source 11 in mirror se~ment l~ 14 will stay at the same height above the optical axis mirror as the magnification iq changed.
Image source 11 may be slidably carried by supports lla to move it along the line llb to change the magnification.
Flgure 5 show~ stlll another embodlment of the pre~ent ,1 !
`.' I
, ~
I invention. Here, a mirror segment 17 is mounted in front of camera lens 19, as it was in Figure 2 of the invention. An image source 11 is mounted above said mirror 17. A planar Il fully silvered mirror 22a is placed in front of ~mage ~ource 11 l~ to receive it~ display and reflect it on to mirror segment 17.
Thi9 folded light path embodiment like that of Figures 3 and 4, is particularly useful where excessive overhang of the recording camera 18 is undesirable for handling purposes.
Instead of using a partially reflective mirror in the various embodiments of this invention, a similar result can be ¦l ach~eved using a dichroic mirror, spherical or planar, in front ~¦ of camera lens 19, in Figures 2 through 5. The dichroic ¦¦ mirror must be fashioned so that it will allow all but a l narrow range of light frequencies to pass through it and be 15 1I photographed by camera 18. A mirror could be coated, for example, so that it would reflect only a narrow ran8e of inten~e greens of between 540 and 546 nanometers in wave- ¦
! length. The image source 11 could be designed to emit light only at these frequencies. The dichroic mirror would l~ therefore reflect substantially all light coming from image Il source 11 to the viewer 29. The mirror would allow all other ~I frequencies to pass through it, 90 the camera 18 located directly behind it would ~nse virtually full color. The operatorl , could boost the sensitivity of camera 18 to greens within the ~ spectrum from those reflected by the dichroic mirror to compensate for it and thereby record virtually full color.
In the embodimentc described above, except those using both "
. I I
, i 1i 113238~
Ithe planar and spherical mirrors, those skilled in the art will ,~ ,, I
have no difficulty selecting and positioning mirrors to meet their needs. The parameterq of the folded light path designs can also be worked out through experimentation or by applying ,1 ~
the information set forth above and basic principles of optics.
To facilitate bullding the mo~t complex embodiment, however~
the one set forth in Figures 3 and 4, an example of how the mirrors and image source mlght be designed and positioned in a prompter is here provided.
~I EXAMPLE
, . . .
Assume a designer wishes to magnify a three by four inch , image three and one half times without obscuring the +15 field of view of the` movie camera lens unted directly behind his mirror segment. Experimentation shows that the cathode ray tube, or other image source, should be located with its closest `ledge six inches in front of the camera lens and six inches below it~ optical center. The cathode ray tube's screen should be tilted forward toward the viewer at an an~le of 34 below the horizontal axis of the movie camera's lens.
The partially reflective planar mirror should be rectangular.
20 li It should measure 16" in width and 12" from~top to bottom. The mirror should be inclined forward at its bottom at an angle of 63.5 from the horizontal. Its bottom should be parallel with .1 ", l ., I
!
, il - 13 -. ~ I
the bottom of the housing. Its center should be located 2"
in front of the camera lens.
The concave spherical mirror se~ment should also be l~rectangtllar. It should have a radius of curvature of 50" and I(~hould measure 11" from front to back and 16" from side to side.
IIIts forward edge should be located about 911 above the center Illine of the camera lens. Its rear edge should be located 13"
above the center line and 4 1/2" in front of the front of the ~I,camera lens.
ll It i9 within the purview-of the present invention to ,Isubstitute a convex front surface mirror segment 35 as shown in Figure 6 for the planar mirror 22a shown in Figure 5. The convex front surface mirror 35 will provide better off-axis il imaging as the viewer moves from left to right of from up to l' down with respect to optical axis. The precise optics of the convex mirror 35 will vary in accordance with well known optical principles and need not be described, therein. I
Having thus fully described the invention, what is Il deYired to be secured and protected by Letters Patent is as follow6:
Visihle displays have been produced in the prior art bY
pro~lecting an ima~e, often termed n "real lma~e," on a 9Creen.
Since the ima~e is formed on the screen surface, its siæe i8 limited to that of the screen itself. This real ima~e appears to ~row smaller, an~ therefore, more difficult to see, as a viewer' distance from the screen increases. Real images on a screen are also degraded by ambient li~,ht.
Where visual information is produced for prompting purposes, the screen must display enough words for a performer to read his script comfortably. It is often difficult to use characters lar~e enough so that they can be read from a distance and still fit on the small cathode ray screens currently in use. Moreover, such ~resent day displays cannot be enlarged r~adily.
Airlines also use closed circuit television svstems in their terminals to make fli~ht in~ormation available to their passen~ers.
These screens too must show so much information on a small area that chey ere difficult to read from e distance.
'~
¦ The present invention overcomes many of the difficulties with ¦ prior are devices by producin~ a magnified virtual ima~e display.
The virtual image, created bv its concave mirror, is more readily shielded from than /ambient light t are real image displays. Unlike prior art ¦ devices employing flat mirrors, the curved virtual image apparatus can ma~nify its displa~ so that it can be read at a distance.
The de~ree of ma~nification can be varied readily if desired.
Another oblect of the present invention is to provide a means for viewing information in front of a photographic or television camera for prompting purposes. In this embodiment, the virtual Lmage display apparatus will provide a script for a performer that he can read in a studio while he is looking directlY at the camera.
Still another ob~ect of the present invention is to provide a ~rompting device which can be used outdoors or in the presence ~r '~I~h lev~l~ Or ~D~c~ IL~hr 113Z3F~4 SUMMA~Y OF THE INVENTION
According to the present invention, a virtual image display apparatus comprises a mirror in the shape of a substan-tially concave segment of a hemisphere said spherical mirror having an optical axis and a focus, an image source means for said mirror segment, and an image display face on said image source disposed substantially perpendicular to said optical axis but located off said axis and between said focus and said mirror segment, said mirror segment being located substantially on the same si.de of the said optical axis as the image source, whereby an observer positioned on the same side of the optical axis as the mirror segment and the image display face can observe a substantially distortion free image.
The following is a description by way of example of certain embodiments of the present invention.
Z3~4 ~ DESCRIPTION OF THE DRAWINGS
I _ . _ In the accompanying drawings formin~ a part hereof, similar parts have been given identical reference numerals, in which drawings:
Figure 1 is a somewhat diagrammatic side view, partially in ~ection,of one complete embodiment of the present invention.
Fi~,ure 2 is a somewhat diagram~atic side view of another embodiment o~ the present invention Figure 3 is a somewhat isometric view, partiallY brolcen away, cf another complete embodiment of the present invention useful for prompting.
Figure 4 is a diagrammatic view, partially in sectio~ of the embodiment shown in Fi~ure 3 illustratin~ the various light paths.
Figure 5 is a somewhat diagramatic side view, partially in section, of still another embodiment of the present invention.
~'igure 6 is a view similar to Figure 5 showing a further embodiment of the invention.
' 3 13Z3~4 , ~ ` , DETAILED DESCRIPTION
Referring to the drawings, and Figure 1 in particular, 10 indicates one complete embodiment of a virtual image display device made in accordance with the present invention.
Il Said embodiment is particularly well suited for large format 5 1I displays in airline terminal~, train stations, and other places where information must be read easily at a distance.
The virtual image display device 10 comprises an information pro~ection device 11, hereinafter referred to as an image Il source, and a curved mirror segment 14 to receive li~ht from I said pro~ection device. The image source illustrated at 11 is intended to depict a cathode ray tube 12, a thin film electroluminescent display, a liquid crystal display-rear or front illuminated, an illuminated film, a light emitting il diode array, electroluminescent panel, filament lamp, gaseous ~ plasma discharge cell or analogous unit. The image source 11 iY mounted in an enclosure 13 and its image display face 30 ls substantially normal to the optical axis 16a and is preferably shielded from ambient light by said enclosure.
~ In the present embodiment, the image source 11 i~ ~uspended from the ceiling of a room, but other supports may be used to suit the location of the image ~ource apparatus.
., . ~
,1 11;~2;384 The lmage source 11 i~ directed at a concave spherical mirror segment as used herein is intended to mean a concave ~portion of a larger hemispherical mirror structure indicated llby dashed lines 14a in Figure 1. Mirror segment 14 is held l~tationary at ~ome predetermined distance below and in front of image source 11 as by bracket 15.
In the embodiment shown in Figure 1, mirror segment 14 is l fully aluminized, preferably front surface. It ma8nifies the !1 image received from the image source 11 and reflects it lltoward the viewers 29 located at some distance below and ~behind enclo~u~es 13. The viewers 29 are represented by the ! schematic eye 29.
l Every concave spherical mirror ha~ a focus and an I optical axis. Said focus is always located at some distance ,lin front of the mirror and on lts axis. Rays paralell and close to the optical axis directed at the surface of the concave mirror concerge near or at its focus. Any ob;ect placed between the f~cus and the concave mirror will appear to be l~ma~nified when viewed by one standing somewhere behind the l~focus. The closer the obJect is located to the focus, the more it will be magnified. The ob~ect reflected by the concave mirror will also appear to the viewer as if it is loca ted s 0mewhe re behind the sur f ace o f the mLrror i ts el f .
~¦ ~13Z3B4 i i This reflection is commonly called a virtual image.
In Figure 1, the optical axis of the mirror 14a is designated by the line 16a. The focus of mirror 14a is the Il point 16b. The image source 11 is positioned between said S Ij focus 16b and the mirror 14a to magnify its display. Mirror segment 14 i8 mounted below the axis 16a so that the display I it reflects i9 not partially blocked from view by the image source 11 and its enclosure 13. Since image source 11 I radiated light out over a wide angular range in front of it, ¦ it i8 possible for mirror segment 14 to be positioned below Il its own axis and yet reflect a portion of this light to the ¦I viewer 29. This reflected portion constitutes the desired ! display of the present invention. The light rays drawn in l~ Figure 1 show how this so-called off axis projection technique 15 ll picks up a portion of the light that image source 11 emits and reflects it toward the viewer 25. Said viewer sees the display from the image source 11 as an enlarged virtual image Il 16c appearing to exist behind mirror segment 14.
Il Figure 2 shows another embodiment of the present invention l in which the virtual ima~e display apparatus is used as a ¦I prompting device. The viewer 29 may be at some distance in ,I front of a movie or television camera 18 mouneed upon a support 20. This schematic figure again shows a cathode ray tube 12 image source directing a display such as a script on to mirror segment 17. Unllke mirror segment 14, used in the .
l. ~
1~32384 l ( first embodiment of this invention, mirror segment 17 is only partially reflective. Mirror segment 17 is surfaced so that typically 70 to 80% of the incident light enters Il camera lens 19 after passing through said mirror segment 17.
; At the same time, mirror segment 17 allows 30 to 20% respect-Il ively of the light coming from the image source 11 to be reflected to the viewer 29. The placement of the image source 11 outside of the field of view of the recording camera (indicated I by lines 12a) prevents said camera from receiving the display l¦ being projected by image source 11. Image source 11 uses a ,~ sufficiently intense light so that the viewer 29 can still read the reflected display coming from the 20 to 30% of the light from the mirror se~ment 17. The remaining 70 to 80% of the , light from image source 11 is wasted. The 20 to 30% decrease ll in brightness of the scene that camera 18 is recording, similarly, is not sufficient to di~rupt its proper functioning.
` Coating mirror segment 17 with ~ilver, aluminum, or '~ other reflective substances to reflect and transmit light in ~ the above described manner is accomplished by techniques well ~I knowm in the art and comprise no part of the present invention.
Figures 3 and 4 illustrate a third embodiment of the present invention~ This embodiment is similar to Figure 1 except that the light path of the di~play reflected from mirror Il se~ment 14 is folded once before it is directed to the viewer 29.
" Foldlng the light path allows the components of the virtual ., I
''' I
.
., I
, . , .. I
g image display appsratus 10 to be re clo5ely arranged in front of a recording camera 18. A partially reflective plannar ;'mlrror 22 i~ here used to fold the light path. The apparatus ~;of Figure 3 is contained in a housing 23 having a top 24, bottom 25, spaced sides 26a and b, and back 27. The front 1 of housing 23 is open.
i Figure 4 shows the arran~ement of each of the optical components in the embodiment of Figure 3. The image source 11 is again mounted with its image display face 30 substsntially llperpendicular to the optical acis 16a of soherical mirror segment ~ 14. Image source 11 is placed inside the focus 16b of mirror ,segment 14 so that its display is magnified by sa~d mirror.
IA small baffle 21, mounted on one edge of the image source 11, ,prevents the viewer from being distracted ~ light radiating , from the edge of the image source's display face 30.
l, Mirror segment 14 is unted off its own optical axis a as described in previous embodiments. Image source 11 is also mounted off the axis 16a. Mirror seg~ent 14 is fully reflective so that it transmits all the light it receives from l,source 11 toward planar mirror 22. Planar mirror 22 is mounted 2Q 11 in front of camera lens 19. Mirror 22 is coated to have its front surface partially reflective such as, for example, ~mirror segment 17 described in the second embodiment of this invention.
Il As noted above, the degree to which a spherical mirror will i~magnify an object placed before it depends upon its location: j ,, . I
1. 1 ,~ I
. .
I
113Z3~4 Il - 10 -I The closer the object is placed to the mirror's focus, the I more the mirror will magnify its virtual image. Applying this principal to each of the three above described embodlments, I it becomes apparent that moving the image source 11 toward focus 16b will increase the magnification of the virtual image display. Moving the source 11 away from the focus 16b decreases the size of the virtual image. Experimentation shows that the image source 11 must be moved along a line ~ which passes through the focus 16b of mirror segment 14, ~ at an angle 0 with respect to, axis 16a such that tan ~ ~ h , where h equals the distance from the center of the image source's display face 30 normal 16a;l ¦ f,l. equals the foval length of the mirror segment 14 ~the ¦ distance from the optical center 16d of mirror segment 14 ¦ to point 16b as measured along axis 16a) and 8 equals the distance from the point 16e where line he intersects axis 16a ! to the center 16d of mirror segment 14 measured along axis 16a l so that the virtual image of image source 11 in mirror se~ment l~ 14 will stay at the same height above the optical axis mirror as the magnification iq changed.
Image source 11 may be slidably carried by supports lla to move it along the line llb to change the magnification.
Flgure 5 show~ stlll another embodlment of the pre~ent ,1 !
`.' I
, ~
I invention. Here, a mirror segment 17 is mounted in front of camera lens 19, as it was in Figure 2 of the invention. An image source 11 is mounted above said mirror 17. A planar Il fully silvered mirror 22a is placed in front of ~mage ~ource 11 l~ to receive it~ display and reflect it on to mirror segment 17.
Thi9 folded light path embodiment like that of Figures 3 and 4, is particularly useful where excessive overhang of the recording camera 18 is undesirable for handling purposes.
Instead of using a partially reflective mirror in the various embodiments of this invention, a similar result can be ¦l ach~eved using a dichroic mirror, spherical or planar, in front ~¦ of camera lens 19, in Figures 2 through 5. The dichroic ¦¦ mirror must be fashioned so that it will allow all but a l narrow range of light frequencies to pass through it and be 15 1I photographed by camera 18. A mirror could be coated, for example, so that it would reflect only a narrow ran8e of inten~e greens of between 540 and 546 nanometers in wave- ¦
! length. The image source 11 could be designed to emit light only at these frequencies. The dichroic mirror would l~ therefore reflect substantially all light coming from image Il source 11 to the viewer 29. The mirror would allow all other ~I frequencies to pass through it, 90 the camera 18 located directly behind it would ~nse virtually full color. The operatorl , could boost the sensitivity of camera 18 to greens within the ~ spectrum from those reflected by the dichroic mirror to compensate for it and thereby record virtually full color.
In the embodimentc described above, except those using both "
. I I
, i 1i 113238~
Ithe planar and spherical mirrors, those skilled in the art will ,~ ,, I
have no difficulty selecting and positioning mirrors to meet their needs. The parameterq of the folded light path designs can also be worked out through experimentation or by applying ,1 ~
the information set forth above and basic principles of optics.
To facilitate bullding the mo~t complex embodiment, however~
the one set forth in Figures 3 and 4, an example of how the mirrors and image source mlght be designed and positioned in a prompter is here provided.
~I EXAMPLE
, . . .
Assume a designer wishes to magnify a three by four inch , image three and one half times without obscuring the +15 field of view of the` movie camera lens unted directly behind his mirror segment. Experimentation shows that the cathode ray tube, or other image source, should be located with its closest `ledge six inches in front of the camera lens and six inches below it~ optical center. The cathode ray tube's screen should be tilted forward toward the viewer at an an~le of 34 below the horizontal axis of the movie camera's lens.
The partially reflective planar mirror should be rectangular.
20 li It should measure 16" in width and 12" from~top to bottom. The mirror should be inclined forward at its bottom at an angle of 63.5 from the horizontal. Its bottom should be parallel with .1 ", l ., I
!
, il - 13 -. ~ I
the bottom of the housing. Its center should be located 2"
in front of the camera lens.
The concave spherical mirror se~ment should also be l~rectangtllar. It should have a radius of curvature of 50" and I(~hould measure 11" from front to back and 16" from side to side.
IIIts forward edge should be located about 911 above the center Illine of the camera lens. Its rear edge should be located 13"
above the center line and 4 1/2" in front of the front of the ~I,camera lens.
ll It i9 within the purview-of the present invention to ,Isubstitute a convex front surface mirror segment 35 as shown in Figure 6 for the planar mirror 22a shown in Figure 5. The convex front surface mirror 35 will provide better off-axis il imaging as the viewer moves from left to right of from up to l' down with respect to optical axis. The precise optics of the convex mirror 35 will vary in accordance with well known optical principles and need not be described, therein. I
Having thus fully described the invention, what is Il deYired to be secured and protected by Letters Patent is as follow6:
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A virtual image display apparatus comprising a mirror in the shape of a substantially concave segment of a hemisphere said spherical mirror having an optical axis and a focus, an image source means for said mirror segment, and an image dis-play face on said image source disposed substantially perpen-dicular to said optical axis but located off said axis and between said focus and said mirror segment, said mirror segment being located substantially on the same side of the said optical axis as the image source, whereby an observer positioned on the same side of the optical axis as the mirror segment and the image display face can observe a substantially distortion free image.
2. A virtual image display apparatus according to claim 1 wherein said mirror segment is a partially reflective mirror.
3. A virtual image display apparatus according to claim 1 wherein a partially reflective planar mirror is angularly positioned between said image source to receive light reflected by the mirror segment and direct it in a path across the opti-cal axis of said mirror segment.
4. A virtual image display apparatus according to claim 1 wherein a fully reflective mirror is placed substantially in front of said image source laterally displaced from the concave mirror segment and parallel to the light emitting image display face of said image source and wherein the said image display face is directed away from said mirror segment.
5. A virtual image display apparatus according to Claim 1 wherein said image source means is a cathode ray tube.
6. A virtual image display apparatus according to Claim 1 wherein said image source means is a this film cathode ray tube.
7. A virtual image display apparatus according to Claim 1 wherein said image source means is a liquid crystal display apparatus.
8. A virtual image display apparatus according to Claim 1 wherein said image source means is a light emitting diode array.
9. A virtual image display device according to Claim 1 wherein said image source means is an electroluminescent panel.
10. A virtual image display device according to Claim 1 wherein said image source means is a tungsten filament projector.
11. A virtual image display device according to Claim 1 wherein said image source means is a gaseous plasma discharge cell.
12. A virtual image display device according to Claim 1 wherein said image source is a back illuminated film or transparency.
13. A virtual image display device according to Claim l wherein said image source means is a front illuminated partially reflecting original.
14. A virtual image display device according to Claim l wherein said mirror segment is dichroic.
15. A virtual image display apparatus according, to Claim 3 wherein said partially reflective planar mirror is dichoic.
16. A virtual image display apparatus according to Claim 1 wherein said image source is slidably carried by a support located between said mirror segment and said focus, whereby said image source may be moved so as to decrease or increase the degree to which its image is magnified by the virtual image display apparatus without changing the vertical position of the virtual image with respect to the mirror segment.
17. A virtual image display apparatus according to Claim 4 in which the fully reflective mirror is a curved front surface mirror.
18. A virtual image display apparatus according to Claim 4 in which the fully reflective mirror is a planar mirror.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA353,223A CA1132384A (en) | 1980-06-02 | 1980-06-02 | Virtual image display apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA353,223A CA1132384A (en) | 1980-06-02 | 1980-06-02 | Virtual image display apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1132384A true CA1132384A (en) | 1982-09-28 |
Family
ID=4117092
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA353,223A Expired CA1132384A (en) | 1980-06-02 | 1980-06-02 | Virtual image display apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1132384A (en) |
-
1980
- 1980-06-02 CA CA353,223A patent/CA1132384A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4294515A (en) | Virtual image display apparatus | |
| US5973845A (en) | Miniature synthesized virtual image electronic display | |
| US4671625A (en) | Optical apparatus for producing a natural, viewable and optically interactive image in free space | |
| US6906860B2 (en) | Curved-screen immersive rear projection display | |
| US3998532A (en) | Wide angle single channel projection apparatus | |
| US7222969B2 (en) | Split image optical display | |
| US6714349B2 (en) | Screen and projection display system with improved viewing angle characteristic | |
| EP0704739A2 (en) | Image display systems | |
| US7111943B2 (en) | Wide field display using a scanned linear light modulator array | |
| US6094181A (en) | Miniature synthesized virtual image electronic display | |
| WO1994018791A1 (en) | Projection monitor | |
| EP0605652A1 (en) | Information display system having transparent holographic optical element | |
| KR20210093258A (en) | image display device | |
| GB2076557A (en) | A Virtual Image Display Apparatus | |
| EP1202079B1 (en) | Projection system | |
| KR20000032673A (en) | Liquid crystal display projector | |
| JP2002523790A (en) | Projection system | |
| CA1132384A (en) | Virtual image display apparatus | |
| US5826961A (en) | Rear projector employing an image display | |
| JPH11327048A (en) | Rear projection type display | |
| CN113589547A (en) | Curved surface transmission type 3D light field display system based on projection array | |
| JPH09113995A (en) | Display device | |
| US20060001967A1 (en) | Wide-field three dimensional imaging system | |
| JP4781537B2 (en) | Camera system and display device | |
| JP2000352695A (en) | Video display device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |