Source: https://patents.justia.com/patent/5539578
Timestamp: 2020-01-22 12:29:24
Document Index: 2475431

Matched Legal Cases: ['art 1', 'art 1', 'art 1', 'art 1', 'art 2', 'art 2', 'art 2', 'art 2', 'art 3', 'art 3', 'art 3', 'art 3', 'arts 1']

US Patent for Image display apparatus Patent (Patent # 5,539,578 issued July 23, 1996) - Justia Patents Search
Justia Patents Superimposing Visual Information On Observers Field Of View (e.g., Head-up Arrangement, Etc.)US Patent for Image display apparatus Patent (Patent # 5,539,578)
Feb 28, 1994 - Olympus
To attain the above-described object, the present invention first provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis passing through the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is reflected by the semitransparent reflecting surface is defined as a visual axis, and the semitransparent reflecting surface is disposed at a tilt to the image axis to change the angle of inclination of the semitransparent reflecting surface to the image axis so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
Secondly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis passing through the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is reflected by the semitransparent reflecting surface is defined as a visual axis, and the magnifying reflecting mirror is disposed at a tilt to the image axis so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
Thirdly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis passing through the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is reflected by the semitransparent reflecting surface is defined as a visual axis, and the magnifying reflecting mirror is shifted with respect to the image axis so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
Fourthly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis reflected by the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, the semitransparent reflecting surface is a partially transmitting-reflecting surface composed of transmitting and reflecting regions which are locally distinguished from each other, and a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is transmitted by the partially transmitting-reflecting surface is defined as a visual axis. The partially transmitting-reflecting surface is disposed at a tilt to the image axis to change the angle of inclination of the partially transmitting-reflecting surface to the image axis so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
Fifthly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis reflected by the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, the magnifying reflecting mirror is a partially transmitting-reflecting surface composed of transmitting and reflecting regions which are locally distinguished from each other, and a straight line that connects an eye point and a position where the optical axis reflected by the partially transmitting-reflecting surface is transmitted by the semitransparent reflecting surface is defined as a visual axis. The partially transmitting-reflecting surface is disposed at a tilt to the image axis so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
Sixthly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis reflected by the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is transmitted by the semitransparent reflecting surface is defined as a visual axis, and the magnifying reflecting mirror is shifted with respect to the image axis so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
Seventhly, the present invention provides a face-mounted image display apparatus including a face-mounted unit which has an image display device with a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis leaving the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path, and a support member for retaining the face-mounted unit on the observer's head. In the image display apparatus, a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is tangent to the semitransparent reflecting surface is defined as a visual axis, and at least the semitransparent reflecting surface or the magnifying reflecting mirror is decentered so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
It is preferable that the angle made between the line normal to the semitransparent reflecting surface and the image axis should be smaller than .pi./4.
When the semitransparent reflecting surface is formed from a half-mirror, the angle .theta. between the line normal to the half-mirror and the image axis preferably satisfies the following condition:
.pi./4-.omega./2.ltoreq..theta.<.pi./4
where .omega. is a half of the vertical field angle.
When the semitransparent reflecting surface is formed from a prism beam splitter having a half-mirror surface, the angle .theta. between the line normal to the half-mirror surface and the image axis preferably satisfies the following condition:
.pi./4-.phi.'/2.ltoreq..theta.<.pi./4
where .omega.'=sin.sup.-1 (sin.phi./n), .omega. is a half of the vertical field angle, and n is the refractive index of a medium constituting the prism.
Ninthly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis reflected by the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, the semitransparent reflecting surface is formed from a semitransparent film coated on a surface of an optical member having a refractive index (n) larger than 1 (n>1), and a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting mirror is transmitted by the semitransparent reflecting surface is defined as a visual axis. The semitransparent reflecting surface is disposed at a tilt to the image axis to change the angle of inclination of the semitransparent reflecting surface to the image axis so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
Tenthly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis reflected by the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, the magnifying reflecting mirror is a magnifying reflecting surface formed from a semitransparent film coated on a surface of an optical member having a refractive index (n) larger than 1 (n>1), and a straight line that connects an eye point and a position where the optical axis reflected by the magnifying reflecting surface is transmitted by the semitransparent reflecting surface is defined as a visual axis. The magnifying reflecting surface is disposed at a tilt to the image axis so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
Eleventhly, the present invention provides an image display apparatus including an image display device having a screen for displaying an image, a semitransparent reflecting surface disposed at an angle of inclination to an optical axis which is determined by a bundle of rays emitted from the display screen, the optical axis being defined as an image axis, and a magnifying reflecting mirror disposed so that an optical axis reflected by the semitransparent reflecting surface goes to and returns from the magnifying reflecting mirror to form a turn-back optical path. In the image display apparatus, the magnifying reflecting mirror is a totally reflecting mirror, and a straight line that connects an eye point and a position where the optical axis reflected by the totally reflecting mirror is transmitted by the semitransparent reflecting surface is defined as a visual axis. The totally reflecting mirror is disposed at a tilt to the image axis so that the angle (.phi.) made by intersection of the image axis extending from the image display device and the visual axis extending from the eye point is larger than 90.degree. (.phi.>90.degree.).
In addition, when the angle made between the line normal to the half-mirror or half-mirror surface and the optical axis of the image display device is set so as to be smaller than .pi./4, it is possible to reduce the area of the half-mirror or the volume of the prism beam splitter. In addition, the distance between the projection optical system and the image display device shortens, so that the diopter adjustable range enlarges. Further, the distance (working distance) between the projection optical system and the observer's eye lengthens. Accordingly, the user can observe a displayed image with his/her spectacles on.
FIG. 9 is a graph showing the relationship between g(.theta.) and .THETA..
In this example, when an optical axis which is determined by a bundle of rays emitted from the screen of the two-dimensional image display device 6 is defined as an image axis x, the image axis x coincides with an optical axis 11 of the concave ocular mirror 5 which passes through the display center 7 of the two-dimensional image display device 6. The optical axis 11 is shifted through about 10.degree. from a reference axis 8 which perpendicularly intersects the visual axis 3 and which passes through the point of intersection of the beam splitter surface 4 and the visual axis 3 so that the angle made by intersection of the image axis x and the visual axis 3 is larger than 90.degree., thereby ensuring the spacing between the observer 1 and the two-dimensional image display device 6. The shift angle .THETA. will hereinafter be referred to as "tilt angle 10" and defined as the angle made between the optical axis 11 of the concave ocular mirror 5 and the reference axis 8. It should be noted that in FIG. 1 the amount of shift of the display center 7 of the two-dimensional image display device 6 from the reference axis 8 is denoted by reference numeral 9. Thus, since both the two-dimensional image display device 6 and the concave ocular mirror 5 are tilted in comparison to those in the prior art, the angle 12 of inclination of the beam splitter surface 4 with respect to the visual axis 3 is larger than 45.degree., which is the original angle of inclination. That is, the beam splitter surface 4 is tilted, and the angle 12 becomes 45.degree.+.THETA./2.
In this example, it is important that the tilt angle .THETA. should be selected in the range of 0.degree.<.THETA.<30.degree.. If the tilt angle .THETA. is not larger than the lower limit of the above range, i.e., 0.degree., the two-dimensional image display device 6 cannot be disposed sufficiently away from the observer's head. If the tilt angle .THETA. is not smaller than the upper limit of the above range, i.e., 30.degree., the concave ocular mirror 5 comes closer to the observer's head (cheek) and may interfere with it.
Next, Example 2 of the present invention will be explained with reference to FIG. 2. In this example, a half-mirror 4 is used in place of the beam splitter. The feature of this example resides in that the half-mirror 4 is tilted at an angle .THETA. in the clockwise direction as viewed in the figure, and the concave ocular mirror 5 is parallel-displaced away from the observer's eyeball position 2 by an amount corresponding to the amount of shift 9 of the display center 7, and that the optical axis 11 is tilted at an angle .THETA. with respect to the reference axis 8. With this arrangement, the two-dimensional image display device 6 can be disposed sufficiently away from the observer's head so that it will not interfere with the observer's head.
In this example, the angle 12 of inclination of the half-mirror reflecting surface 4 is 45.degree.-.THETA./2. It is important that the tilt angle .THETA. should be selected in the range of 0.degree.<.THETA.<30.degree.. If the tilt angle .THETA. is not smaller than the upper limit of the above range, i.e., 30.degree., the amount of shift 9 of the display center 7 becomes 0. Consequently, the two-dimensional image display device 6 cannot effectively be separated away from the observer's head. If the tilt angle .THETA. is not larger than the lower limit of the above range, the bundle of rays from the two-dimensional image display device 6 is incident on the concave ocular mirror 5 at an excessively large angle to the optical axis 11 of the concave ocular mirror 5, causing large comatic aberration to be produced. Thus, it becomes impossible to obtain a wide field angle and high resolution.
It is even more preferable to tilt the two-dimensional image display device 6 at an angle equal to the angle .THETA. in the clockwise direction as viewed in the figure so that the two-dimensional image display device 6 perpendicularly intersects the optical axis 11 of the concave ocular mirror 5 for the purpose of correcting the bowing of the aerial image which is caused by inclining the concave ocular mirror 5 with respect to the optical axis and which is seen to the observer 1 as a diopter error of the observation image. By doing so, the above-described diopter error can be eliminated.
Next, Example 3 of the present invention will be explained with reference to FIG. 3. This example is basically the same as Example 1. In this example, however, the optical axis 11 of the concave ocular mirror 5 is tilted with respect to the image axis x. In addition, a beam splitter prism P is used as an optical path splitting device, and a reverse reflecting mirror M is used as a concave ocular mirror 5. In this example, the beam splitter surface 4 is inclined at an angle of 45.degree., as denoted by reference numeral 12, and need not be further inclined in particular. It is important that the tilt angle .THETA. of the optical axis 11 of the concave ocular mirror 5 with respect to the reference axis 8 should be selected in the range of 0.degree.<.THETA.<30.degree.. If the tilt angle .THETA. is not smaller than the upper limit of the above range, i.e., 30.degree., the bundle of rays from the two-dimensional image display device 6 is incident on the concave ocular mirror 5 at an excessively large angle to the optical axis 11 of the concave ocular mirror 5, causing large comatic aberration to be produced by the concave ocular mirror 5. Accordingly, it becomes impossible to obtain a wide field angle and high resolution. If the tilt angle .THETA. is not larger than the lower limit of the above range, the amount of shift 9 of the display center 7 becomes 0. Consequently, the two-dimensional image display device 6 cannot effectively be separated away from the observer's head.
It is even more preferable to incline the line normal to the two-dimensional image display device 6 at an angle equal to the angle .THETA. toward the reference axis 8 for the purpose of correcting the bowing of the aerial image which is caused by inclining the concave ocular mirror 5 with respect to the optical axis and which is seen to the observer 1 as a diopter error of the observation image. By doing so, the above-described diopter error can be eliminated.
Next, Example 4 of the present invention will be explained with reference to FIG. 4. This example is basically the same as Example 2. The feature of this example resides in that the concave ocular mirror 5 is not tilted with respect to the axial ray on the visual axis 3 but disposed so that the optical axis thereof is parallel to the reference axis 8. In this case, if the tilt angle .THETA. is defined as the angle made between the optical axis 11 of the concave ocular mirror 5 and the axial ray reflected by the concave ocular mirror 5, the condition therefor is the same as in Example 2. In this example, the angle 12 of inclination of the beam splitter surface 4 with respect to the visual axis 3 is 45.degree.-.THETA./2.
The foregoing discussion centers about the tilt angle .THETA. from the reference axis 8, which perpendicularly intersects the visual axis 3 and which passes through the point of intersection of the beam splitter surface 4 and the visual axis 3. The following is another discussion which centers about the angle .THETA. made between the image axis x of the two-dimensional image display device 6 [hereinafter referred to as "LCD (Liquid Crystal Display)] and the line normal to the half-mirror 4.
FIG. 5 shows a basic form of the image display apparatus according to the present invention which includes an LCD 6 for displaying an image, a half-mirror 4 which is obliquely disposed at the point of intersection of the optical axis (image axis) of the LCD 6 and the observer's visual axis for leading a bundle of rays from an image formed by the LCD 6 to an observer's eyeball (eye point) 2, and a magnifying reflecting mirror 5 of positive power which is disposed to face the LCD 6 across the half-mirror 4. The half-mirror 4 is disposed so that the angle .THETA. made between the line normal to the half-mirror 4 and the optical axis of the LCD 6 is smaller than .pi./4.
First, the size of the projection optical system will be explained. FIG. 7 shows the half-mirror c that is disposed relative to a bundle of rays reflected by the concave mirror b. With regard to the area of the half-mirror c, minimization of it enables a reduction in the overall size and weight of the projection optical system. The size of the half-mirror c must be larger than at least the cross-section of the bundle of rays reflected by the concave mirror b, which is taken along the plane in which the half-mirror c is disposed. In other words, the smaller the angle .THETA. made between the line normal to the half-mirror c and the optical axis of the LCD a, the smaller the size of the half-mirror c.
Let us consider the size of a prism beam splitter when used to constitute the half-mirror c. If the point of intersection of a line perpendicular to the optical axis of the LCD a from the end surface u of the half-mirror c which is closer to the LCD a and the optical axis of the LCD a is assumed to be v, as the angle .THETA. between the line normal to the half-mirror c and the optical axis of the LCD a becomes smaller, the angle of inclination of the half-mirror c decreases, and the distance between the concave mirror b and the point v shortens. The advantageous effect is particularly significant when the half-mirror c is formed by using a prism beam splitter; the shorter the distance between the concave mirror b and the point v, the smaller the volume of the prism.
Next, the distance between the projection optical system and the LCD will be explained. If the point of intersection of a line perpendicular to the optical axis of the LCD a from the end surface u of the half-mirror c which is closer to the LCD a and the optical axis of the LCD a is assumed to be v, as the angle .THETA. between the line normal to the half-mirror c and the optical axis of the LCD a becomes smaller, the distance between the concave mirror b and the point v shortens, so that the distance between the LCD a and the prism can be increased correspondingly. Accordingly, when the diopter is adjusted by moving the LCD a, the diopter adjustable range enlarges.
Next, the distance between the projection optical system and the observer's eyeball will be explained. FIG. 8 is a sectional view of the optical system taken along the plane that contains the optical axis x of the LCD and the center of the observer's eyeball. It is assumed that the point of intersection of the optical axis x of the LCD and the concave mirror b is e; the point of intersection of the half-mirror c and the concave mirror b in the plane that contains both the optical axis x of the LCD and the line normal to the half-mirror c when the half-mirror c is disposed so that the curved line where the concave mirror b and the half-mirror c intersect each other will not eclipse the bundle of rays is p; the point of intersection of the optical axis x of the LCD and the half-mirror c is f; the angle made between the optical axis x of the LCD and the line normal to the half-mirror c is .THETA.; a point on the concave mirror b which is in symmetry with the point p with respect to the optical axis x of the LCD is q; and the point of intersection of an optical axis (visual axis) formed by reflection of the reflected rays from the concave mirror b by the half-mirror c and a line perpendicular to the optical axis from the point q is s. The distance WD is given by
WD=l.sub.2 -(ef+fs) (1)
When the point p of intersection of the concave mirror b and the half-mirror c is fixed, (ef+fs) is a function of only the angle .THETA., which may be given by
g(.THETA.)=ef+fs (2)
When the curvature of the concave mirror b and the point p are fixed, the distance between the points e and e' is a constant. Assuming that the distance is t, g(.THETA.) is given by
g(.THETA.)=k(tan .THETA.+1/sin 2.THETA.+tan .THETA.cos 2.THETA.-cos 2.THETA./tan 2.THETA.)+t (3)
FIG. 9 is a graph showing the relationship between g(.THETA.) and .THETA.. When .THETA.=.pi./4 (45.degree.), g(.THETA.) reaches a maximum. When .THETA.<.pi./4, g(.THETA.) monotonously increases, whereas, when .THETA.>.pi./4, g(.THETA.) monotonously decreases. However, when .THETA.>.pi./4, the LCD a comes closer to the observer's face, which is undesirable.
Accordingly, it is possible to increase the distance WD by reducing the angle .THETA. made between the optical axis x of the LCD and the line normal to the half-mirror c.
Thus, as the angle of the half-mirror c becomes smaller than .pi./4, the size of the projection optical system can be minimized, and it is possible to lengthen the distance WD between the observer's eyeball and the projection optical system and the distance between the LCD and the projection optical system.
However, if the angle of the line normal to the half-mirror c with respect to the optical axis x of the LCD is made excessively smaller than .pi./4, among light rays emitted from the LCD a and reflected from the concave mirror b and the half-mirror c, the ray that enters the observer's ball from the lowermost side perpendicularly intersects the optical axis x of the LCD. If the angle of the line normal to the half-mirror c with respect to the optical axis x of the LCD is made further small, the edge of the concave mirror b which is opposite to the intersection of the half-mirror c and the concave mirror b with respect to the optical axis x of the LCD eclipses light rays which are reflected from the half-mirror c toward the observer's eyeball.
More specifically, assuming that the vertical field angle is 2.omega., and the refractive index of a medium constituting a prism used to constitute the half-mirror c is n, the angle .THETA. made between the optical axis x of the LCD and the line normal to the half-mirror c is preferably set in the following range:
.pi./4-.phi.'/2.ltoreq..THETA.<.pi./4 (4)
.omega.'=sin.sup.-1 (sin .phi./n) (5)
.pi./4-.omega./2.ltoreq..THETA.<.pi./4 (6)
In the expression (4) or (6), as the value for .THETA. approaches the left-hand side, the above-described effect becomes greater.
Referring to FIG. 10, (a) is a sectional view of an optical system of Example 5 according to the present invention, and (b) is a sectional view of an optical system of prior art 1 corresponding to Example 5. In the figure, reference symbol E denotes the position of an observer's pupil, 6 an LCD, 4 a half-mirror, and 5 a concave mirror. The angle made between the optical axis of the LCD 6 and the line normal to the half-mirror 4 is 38.5.degree. in Example 5; it is 45.degree. in prior art 1. Numerical data in Example 5 and prior art 1 will be described later. Example 5 and prior art 1 are equal to each other in terms of the field angle, which is 35.times.26.degree., the size of the LCD 6, which is 26.0.times.19.1 mm, the distance from the LCD 6 to the concave mirror 5, and the distance from the concave mirror 5 to the pupil position E.
Referring to FIG. 11, (a) is a sectional view of an optical system of Example 6 according to the present invention, and (b) is a sectional view of an optical system of prior art 2 corresponding to Example 6. In the figure, reference symbol E denotes the position of an observer's pupil, 6 an LCD, 13 a prism beam splitter, 4 a half-mirror surface of the prism beam splitter 13, 5 a concave mirror, 14 a surface of the prism beam splitter 13 which faces the LCD 6, and 15 a surface of the prism beam splitter 13 which faces the observer's eyeball. The angle made between the optical axis of the LCD 6 and the line normal to the half-mirror 4 is 40.5.degree. in Example 6; it is 45.degree. in prior art 2. Numerical data in Example 6 and prior art 2 will be described later. Example 6 and prior art 2 are equal to each other in terms of the field angle, which is 37.times.27.6.degree., and the size of the LCD 6, which is 26.0.times.19.1 mm.
Referring to FIG. 12, (a) is a sectional view of an optical system of Example 7 according to the present invention, and (b) is a sectional view of an optical system of prior art 3 corresponding to Example 7. In the figure, reference symbol E denotes the position of an observer's pupil, 6 an LCD, 13 a prism beam splitter, 4 a half-mirror surface of the prism beam splitter 13, 5 a concave mirror, 14 a surface of the prism beam splitter 13 which faces the LCD 6, 15 a surface of the prism beam splitter 13 which faces the observer's eyeball, 16 a concave lens, and 17 a convex lens. The angle made between the optical axis of the LCD 6 and the line normal to the half-mirror 4 is 41.degree. in Example 7; it is 45.degree. in prior art 3. Numerical data in Example 7 and prior art 3 will be described later. Example 7 and prior art 3 are equal to each other in terms of the field angle, which is 44.times.33.2.degree., and the size of the LCD 6, which is 26.0.times.19.1 mm.
In Example 6, divergence of the bundle of rays in the prism is minimized by imparting positive power to the eyeball-side surface 15 of the prism in this example, thereby further widening the field angle. In the prior art, the distance from the LCD 6 to the prism is short, so that the diopter adjustable range is narrow when diopter correction is made in the negative direction (the image position is moved toward the near side) by moving the LCD 6. In this example, however, since the angle made between the optical axis of the LCD 6 and the line normal to the half-mirror surface 4 is set at 41.degree., the distance from the vertex of the prism end surface 14 to the LCD 6 can be increased to 7.00 mm from 5.55 mm in the prior art. Thus, the diopter adjustable range can be enlarged by 1.3/m to the negative side in comparison to the prior art. Further, the distance from the prism end surface 15 to the observer's eyeball can be increased to 20.0 mm from 19.3 mm in the prior art. In addition, the volume of the prism can be reduced by 10% in comparison to the prior art.
Numerical data in the above-described Examples 5 to 7 and prior arts 1 to 3, which are obtained by backward tracing, will be shown below. These pieces of data are all shown in the order of backward tracing from the pupil E to the image display device 6. In all Examples, r.sub.0 denotes the pupil E, d.sub.0 is the working distance (WD), r.sub.1, r.sub.2 . . . are the radii of curvature of lens surfaces or reflecting surfaces, d.sub.1, d.sub.2 . . . are the spacings between adjacent lens surfaces, n.sub.d1, n.sub.d2 . . . are the refractive indices for the spectral d-line of the glass materials, .nu..sub.d1, .nu..sub.d2 . . . are the Abbe's numbers of the glass materials, and r.sub.20 is the image display device 6. Further, the aspherical configuration is expressed by
z=ch.sup.2 /{1+[1-c.sup.2 (K+1)h.sup.2 ].sup.1/2 }+Ah.sup.4 +Bh.sup.6 +Ch.sup.8 +Dh.sup.10 (7)
r.sub.0 = .infin.
(E)   d.sub.0 = 35.300000
(4)   d.sub.1 = -14.172190
(.theta. 38.500000.degree.)
r.sub.2 = 85.48059
(5)   d.sub.2 = 43.835912
r.sub.20 = .infin.
(E)   d.sub.0 = 32.000000
(4)   d.sub.1 = -17.472190
(.theta. = 45.000000.degree.)
(E)   d.sub.0 = 19.200000
(15)  d.sub.1 = 16.200000
n.sub.d1 = 1.516330
(4)   d.sub.2 = 13.339170
n.sub.d2 = 1.516330
(.theta. = 40.500000.degree.)
r.sub.3 = 123.40676
(5)   d.sub.3 = 24.500000
n.sub.d3 = 1.516330
(14)  d.sub.4 = 24.846988
(E)   d.sub.0 = 19.000000
(15)  d.sub.1 = 14.500000
(4)   d.sub.2 = 15.339170
r.sub.3 = 123.40638
(5)   d.sub.3 = 28.000000
(14)  d.sub.4 = 22.542094
(E)   d.sub.0 = 20.000000
r.sub.1 = 79.40268
(15)  d.sub.1 = 17.000000
(4)   d.sub.2 = -15.000000
(.theta. = 41.000000.degree.)
r.sub.3 = 55.04852
d.sub.2 = -0.500000
r.sub.4 = 140.20084
(16)  d.sub.2 = -1.500000
n.sub.d3 = 1.805177
.nu..sub.d3 = 25.4
r.sub.5 = 9305.57882
(17)  d.sub.2 = -2.600000
n.sub.d4 = 1.516330
r.sub.6 = 144.37844
(5)   d.sub.3 = 2.600000
n.sub.d5 = 1.516330
r.sub.7 = 9305.57882
d.sub.2 = 1.500000
n.sub.d6 = 1.805177
.nu..sub.d6 = 25.4
r.sub.8 = 140.20084
d.sub.2 = 0.500000
r.sub.8 = 55.04852
d.sub.3 = 26.000000
n.sub.d7 = 1.516330
.nu..sub.d7 = 64.1
(14)  d.sub.4 = 7.000000
A = 0.187498 .times. 10.sup.-4
(E)   d.sub.0 = 19.340000
r.sub.1 = 91.35114
(15)  d.sub.1 = 16.000000
(4)   d.sub.2 = -17.000000
n.sub.2 = 1.516330
r.sub.3 = 50.81031
r.sub.4 = 140.90134
r.sub.6 = 151.92998
r.sub.8 = 140.90134
r.sub.8 = 50.81031
d.sub.3 = 29.000000
(14)  d.sub.4 = 5.550034
A = 0.252379 .times. 10.sup.-4
Incidentally, no mention has been made of the form of the beam splitter surface 4 of the prism beam splitter or the half-mirror surface 4 in the foregoing description. In the present invention, it is possible to use any of a partially transmitting-reflecting surface 41, a semitransparent film 42 and a polarizing semitransparent film 43, which may be provided on a cemented surface of a prism or on a transparent substrate, for example, as shown at (a) to (c) in FIG. 15. More specifically, the beam splitter surface or half-mirror surface 4 is a surface that transmits about 50% of the quantity of incident light and reflects about 50% of it. The beam splitter surface or half-mirror surface 4 may be used with the transmittance-to-reflectance ratio varied in the range of from 1:9 to 9:1, in addition to the above. The beam splitter surface or half-mirror surface 4 may be realized by any of the following methods: one in which the quantity of incident light is divided in terms of area; another in which the quantity of incident light is divided in terms of light intensity; and another in which the quantity of incident light is divided in terms of both area and intensity. In the case of the partially transmitting-reflecting surface 41 shown at (a) in FIG. 15, the quantity of incident light is divided in terms of area. In this case, reflection coating of aluminum or the like is provided on a cemented surface of a prism or on a transparent substrate (the refractive index n of which is larger than 1, i.e., n>1) at intervals, for example, in a lattice-like pattern of about several .mu.m to 0.1 mm, whereby a reflectance and a transmittance are set overall (macrocosmically) by the ratio of the area of the reflecting portions to the area of the transmitting portions. In the case of the semitransparent film 42 shown at (b) in FIG. 15, a cemented surface of a prism or a transparent substrate (the refractive index n of which is larger than 1, i.e., n>1) is coated with a metallic, extremely thin film, e.g., an extremely thin film of aluminum or chromium, or a dielectric multilayer film of SiO.sub.2, MgF.sub.2, etc., thereby dividing the quantity of incident light. The polarizing semitransparent film 43 shown at (c) in FIG. 15 divides the quantity of incident light by separating polarized light components of the incident light. More specifically, the polarizing semitransparent film 43 is coated on a cemented surface of a prism or on a transparent substrate to allow p- and s-polarized light components to be selectively transmitted or reflected to thereby divide the quantity of the incident light.
said semitransparent reflecting surface is disposed at a tilt to said image axis to change the angle of inclination of said semitransparent reflecting surface to said image axis so that an angle (.phi.) made by intersection of said image axis extending from said image display device and said visual axis extending from said eye point is larger than 90.degree. (.phi.>90.degree.).
said magnifying reflecting mirror is disposed at a tilt to said image axis so that an angle (.phi.) made by intersection of said image axis extending from said image display device and said visual axis extending from said eye point is larger than 90.degree. (.phi.>90.degree.).
said magnifying reflecting mirror is shifted with respect to said image axis so that an angle (.phi.) made by intersection of said image axis extending from said image display device and said visual axis extending from said eye point is larger than 90.degree. (.phi.>90.degree.).
said partially transmitting-reflecting surface is disposed at a tilt to said image axis to change the angle of inclination of said partially transmitting-reflecting surface to said image axis so that an angle (.phi.) made by intersection of said image axis extending from said image display device and said visual axis is extending from said eye point is larger than 90.degree. (.phi.>90.degree.), a space between said partially transmitting-reflecting surface and said magnifying reflecting mirror being formed from a prism which is filled with a medium having a refractive index (n) larger than 1 (n>1).
said partially transmitting-reflecting surface is disposed at a tilt to said image axis so that an angle (.phi.) made by intersection of said image axis extending from said image display device and said visual axis extending from said eye point is larger than 90.degree. (.phi.>90.degree.), a space between said semitransparent reflecting surface and said magnifying reflecting mirror being formed from a prism which is filled with a medium having a refractive index (n) larger than 1 (n>1).
said magnifying reflecting mirror is shifted with respect to said image axis so that an angle (.THETA.) made by intersection of said image axis extending from said image display device and said visual axis extending from said eye point is larger than 90.degree. (.THETA.>90.degree.), wherein a prism having a medium of refractive index (n) larger than 1 (n>1) is formed in between said semi-transparent reflecting mirror and said magnifying reflecting mirror.
at least one of said semitransparent reflecting surface and said magnifying reflecting mirror is decentered so that an angle (.phi.) made by intersection of said image axis extending from said image display device and said visual axis extending from said eye point is larger than 90.degree. (.phi.>90.degree.), a space between said semitransparent reflecting surface and said magnifying reflecting mirror being formed from a prism which is filled with a medium having a refractive index (n) larger than 1 (n>1).
11. An image display apparatus according to claim 1, 2, 3, 4, 5, 6 or 7, wherein an angle made between a line normal to said semitransparent reflecting surface and said image axis is smaller than.pi./4.
12. An image display apparatus according to claim 11, wherein said semitransparent reflecting surface is formed from a half-mirror, and an angle.THETA. between a line normal to said half-mirror and said image axis satisfies the following condition:
13. An image display apparatus according to claim 11, wherein said semitransparent reflecting surface is formed from a prism beam splitter having a half-mirror surface, and an angle.THETA. between a line normal to said half-mirror surface and said image axis satisfies the following condition:
said magnifying reflecting surface is disposed at a tilt to said image axis so that an angle (.phi.) made by intersection of said image axis extending from said image display device and said visual axis extending from said eye point is larger than 90.degree. (.phi.>90.degree.).
said totally reflecting mirror is disposed at a tilt to said image axis so that an angle (.phi.) made by intersection of said image axis extending from said image display device and said visual axis extending from said eye point is larger than 90.degree. (.phi.>90.degree.).
5200856 April 6, 1993 Beaussant
3191389 August 1991 JPX
Patent number: 5539578
Inventors: Takayoshi Togino (Koganei), Masato Yasugaki (Kunitachi)
Application Number: 8/202,465
Current U.S. Class: Superimposing Visual Information On Observers Field Of View (e.g., Head-up Arrangement, Etc.) (359/630); Including Curved Reflector (359/631); Image Superposition By Optical Means (e.g., Heads-up Display) (345/7); Operator Body-mounted Heads-up Display (e.g., Helmet Mounted Display) (345/8)
International Classification: G02B 2710; G09G 500;