Stereoscopic eyeglasses, method for designing eyeglass lens to be used for the stereoscopic eyeglasses, and method for observing stereoscopic image

Abstract

Provided are stereoscopic eyeglasses capable of reducing visual fatigue in binocular stereoscopic display by a simple configuration. In stereoscopic eyeglasses, in order to expand a tolerance of match between vergence and accommodation enabling comfortable stereovision in eyeglasses-using stereoscopic display, wide-focus lenses ranging in focal length are incorporated so as to overlap optical filters in light transmission directions, and accordingly, visual fatigue to be caused by vergence-accommodation conflict during stereoscopic image observation is reduced.

Claims

1. A method for observing a stereoscopic image, comprising using stereoscopic eyeglasses, the stereoscopic eyeglasses comprising: an optical filter for a left eye which transmits only an image for the left eye out of the image for the left eye and an image for a right eye displayed on a display surface of an image display device; the optical filter for the right eye which transmits only the image for the right eye out of the image for the left eye and the image for the right eye; a wide-focus lens for the left eye ranging in focal length disposed so as to overlap the optical filter for the left eye in a light transmission direction; and a wide-focus lens for the right eye ranging in focal length disposed so as to overlap the optical filter for the right eye in the light transmission direction, wherein when an observation distance to the display surface is 2m or more, by using the wide-focus lenses having a negative focal length, a stereoscopic display range enabling comfortable observation of the stereoscopic image is expanded at a front of the display surface of the image display device on which the image for the left eye and the image for the right eye are displayed, wherein when the observation distance to the display surface is 0.6 m or less, by using the wide-focus lenses having a positive focal length, the stereoscopic display range enabling comfortable observation of the stereoscopic image is expanded at a rear of the display surface of the image display device on which the image for the left eye and the image for the right eye are displayed, wherein when the observation distance to the display surface is more than 0.6m to less than 2m, by using the wide-focus lenses having positive and negative focal lengths, the stereoscopic display range enabling comfortable observation of the stereoscopic image is expanded at both of the front and the rear of the display surface of the image display device on which the image for the left eye and the image for the right eye are displayed.

2. Stereoscopic eyeglasses, wherein wide-focus lenses ranging in focal length are incorporated to expand a tolerance of match between vergence and accommodation enabling comfortable stereovision in eyeglasses using stereovision, the stereoscopic eyeglasses comprising: a pair of left and right eyeglass lenses as the wide-focus lenses, wherein in each of the eyeglass lenses, when an axis in the anteroposterior direction passing through a lens optical center is defined as a z-axis, and a direction toward the rear side of the lens is defined as a positive direction of the z-axis, an average power stabilization component which is expressed as Ar.sup.4+Br.sup.6+Cr.sup.8+Dr.sup.10 (r is a distance from the z-axis, and A, B, C, and D are constants) and suppresses variations in average power from the lens optical center to a lens peripheral edge portion is added to a z-coordinate value of at least one of the front surface and the rear surface of the lens, and a depth-of-field extension component expressed as Er.sup.3 (E is a constant) is added to a z-coordinate value of either the front surface or the rear surface of the lens.

3. The stereoscopic eyeglasses according to claim 2, wherein the eyeglass lenses gradually change in average power to the negative side or the positive side from the lens optical center toward the lens peripheral edge portion.

4. The stereoscopic eyeglasses according to claim 2, wherein in the eyeglass lenses, a power component for correcting at least myopia, hyperopia, and astigmatism is further set.

5. A method for designing the eyeglass lens to be used for the stereoscopic eyeglasses according to claim 2, comprising: a first aspherical component adding step of adding an average power stabilization component which is expressed as, when an axis in the anteroposterior direction passing through a lens optical center is defined as a z-axis, and a direction toward the rear side of the lens is defined as a positive direction of the z-axis, Ar.sup.4+Br.sup.6+Cr.sup.8+Dr.sup.10 (r is a distance from the z-axis, and A, B, C, and D are constants) and suppresses variations in average power from the lens optical center to a lens peripheral edge portion, to a z-coordinate value of at least one of the front surface and the rear surface of the lens determined according to the prescription power; and a second aspherical component adding step of adding a depth-of-field extension component which is expressed as Er.sup.3 (E is a constant) and extends a depth of field, to a z-coordinate value of either the front surface or the rear surface of the lens.

6. The stereoscopic eyeglasses according to claim 2, comprising: an optical filter for a left eye which transmits only an image for the left eye out of the image for the left eye and an image for a right eye displayed on a display surface of an image display device; the optical filter for the right eye which transmits only the image for the right eye out of the image for the left eye and the image for the right eye; the wide-focus lens for the left eye disposed so as to overlap the optical filter for the left eye in a light transmission direction; and the wide-focus lens for the right eye disposed so as to overlap the optical filter for the right eye in the light transmission direction.

7. The stereoscopic eyeglasses according to claim 6, wherein the optical filters are formed of polarizers.

8. The stereoscopic eyeglasses according to claim 6, wherein the optical filters are formed of liquid crystal shutters.

9. The stereoscopic eyeglasses according to claim 6, wherein the optical filters are formed of spectral filters.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a diagram for describing a relationship between accommodation and vergence.

(2) FIG. 2 is a view illustrating a configuration of stereoscopic eyeglasses of the present invention.

(3) FIG. 3 are views for describing states of image formation in wide-focus lenses, and FIG. 3(a) illustrates a case of real image formation, and FIGS. 3(b) and 3(c) illustrate cases of virtual image formation.

(4) FIG. 4(a) is an operation explanatory view of conventional stereoscopic eyeglasses, and FIGS. 4(b) and 4(c) are operation explanatory views of the stereoscopic eyeglasses illustrated in FIG. 2.

(5) FIG. 5 is an operation explanatory view following FIGS. 4.

(6) FIG. 6(a) is a diagram for describing an effect of the stereoscopic eyeglasses illustrated in FIG. 2 when an observation distance is long, FIG. 6(b) is a diagram for describing an effect of the stereoscopic eyeglasses illustrated in FIG. 2 when the observation distance is short, and FIG. 6(c) is a diagram for describing an effect of the stereoscopic eyeglasses illustrated in FIG. 2 when the observation distance is medium.

(7) FIG. 7 is a view illustrating stereoscopic eyeglasses according to an embodiment of the present invention together with a stereoscopic display device adapted to a polarization method.

(8) FIG. 8 is a view illustrating a projector adapted to a polarization method.

(9) FIGS. 9(a) to 9(1) are views respectively illustrating configurations of stereoscopic eyeglasses using polarizers.

(10) FIG. 10 is a view illustrating stereoscopic eyeglasses according to another embodiment of the present invention together with a stereoscopic display device adapted to a liquid crystal shutter method.

(11) FIG. 11 is a view illustrating a projector adapted to a liquid crystal shutter method.

(12) FIG. 12(a) is a view illustrating a projector adapted to a spectral filter method, and FIG. 12(b) is a view illustrating stereoscopic eyeglasses according to still another embodiment of the present invention.

(13) FIG. 13(a) is a schematic view of an entirety of an eyeglass lens to be used for the stereoscopic eyeglasses according to the embodiment of the present invention, and

(14) FIG. 13(b) is an enlarged schematic view of an upper half of the same lens.

(15) FIG. 14 is a view for describing the eyeglass lens illustrated in FIGS. 13.

(16) FIG. 15 is a diagram illustrating average power changes along a lens radial direction in the eyeglass lens illustrated in FIGS. 13.

(17) FIG. 16 are diagrams illustrating evaluation results of the stereoscopic eyeglasses of the same embodiment, and FIG. 16(a) illustrates “viewability” and FIG. 16(b) illustrates “eye fatigue.”

(18) FIG. 17 are diagrams illustrating evaluation results, following FIGS. 16.

(19) FIG. 18 is an explanatory view illustrating the principle of binocular stereoscopic display.

DESCRIPTION OF EMBODIMENTS

First Embodiment

(20) An embodiment of stereoscopic eyeglasses and a method for observing a stereoscopic image, adapted to stereoscopic display using a polarization method, will be described.

(21) When an image display device 100 is a television type or a monitor type, as illustrated in FIG. 7, to a display surface 100a, horizontally long wave plates 40a and 40b corresponding to odd-numbered and even-numbered scanning lines are attached and configured so that, to display images of odd-numbered and even-numbered scanning lines, circularly polarized lights whose rotation directions are opposite to each other are given. By using odd-numbered and even-numbered scanning lines, an image for the left eye and an image for the right eye are displayed. The correspondence relationship between the odd-numbered and even-numbered scanning lines and an image for the left eye and an image for the right eye to be displayed may be reversed.

(22) To stereoscopic eyeglasses 10A adapted to this display, a polarizer 42a for the left eye and a polarizer 42b for the right eye are attached as optical filters. The polarizer 42a for the left eye and the polarizer 42b for the right eye transmit only circularly polarized lights whose rotation directions are opposite to each other, and are configured so that the image for the left eye is viewed with the left eye 25a of an observer, and the image for the right eye is viewed with the right eye 25b of the observer. In this example, as the polarizers, polarization films are used.

(23) Here, the case using circularly polarized lights whose rotation directions are opposite to each other is described by way of example, however, linearly polarized lights orthogonal to each other can also be used instead. In this case, normal polarizers that transmit linearly polarized lights can be used.

(24) In the case of a 3D movie, as illustrated in FIG. 8, images for the left eye and the right eye are alternately displayed by double-speed driving a projector 44, and a liquid crystal element 46 to control light polarization states is disposed in front of the projector 44 so that circularly polarized lights whose rotation directions are opposite to each other (or linearly polarized lights orthogonal to each other) are given to the image for the left eye and the image for the right eye.

(25) FIG. 9 illustrate a configuration of stereoscopic eyeglasses 10A adapted to a polarization method. In the stereoscopic eyeglasses 10A, a wide-focus lens 16a for the left eye and a wide-focus lens 16b for the right eye are disposed corresponding to the polarizer 42a for the left eye and the polarizer 42b for the right eye. FIGS. 9(a) to 9(f) illustrate cases using positive wide-focus lenses, and FIGS. 9(g) to 9(i) illustrate cases using negative wide-focus lenses.

(26) The stereoscopic eyeglasses 10A can also be configured so that the polarizer 42 (42a, 42b) and the wide-focus lens 16 (16a, 16b) are separated from each other as illustrated in FIGS. 9(a), 9(d), 9(e), 9(f), 9(g), 9(j), 9(k), and 9(l). When the polarizer 42 and the wide-focus lens 16 are separated from each other, either one of the polarizer 42 and the wide-focus lens 16 can be detached from the frame 12 as necessary. As illustrated in FIGS. 9(d), 9(f), 9(j), and 9(l), by using a wide-focus lens 16 whose both lens surfaces opposed to each other are curved surfaces, a wide angle of view as viewed from the eye and uniform characteristics can be obtained.

(27) It is also possible that the wide-focus lens 16 is integrally joined to the polarizer 42 as illustrated in FIGS. 9(b), 9(c), 9(h), and 9(i). This enables the stereoscopic eyeglasses 10A to be configured in a compact manner.

(28) It is also possible that the wide-focus lens 16 is disposed at the front (side opposite to the eyeball) with respect to the polarizer 42 as illustrated in FIGS. 9(e), 9(f), 9(k), and 9(l).

(29) As described later, in the present example, as the wide-focus lens 16, an eyeglass lens to which a depth-of-field extension component is added is used.

Second Embodiment

(30) An embodiment of stereoscopic eyeglasses and a method for observing a stereoscopic image, adapted to stereoscopic display using a liquid crystal shutter method, will be described.

(31) In stereoscopic display using a liquid crystal shutter method, in a case where an image display device 100 is a television type or a monitor type, an image for the left eye and an image for the right eye are alternately displayed by double-speed driving as illustrated in FIG. 10. In a case of a 3D movie, an image for the left eye and an image for the right eye are alternately displayed by double-speed driving a projector 55 as illustrated in FIG. 11.

(32) To stereoscopic eyeglasses 10B adapted to this display, a liquid crystal shutter 50a for the left eye and a liquid crystal shutter 50b for the right eye are attached as optical filters. These liquid crystal shutters 50a and 50b are configured to be switchable between a transmissive state and a non-transmissive state according to image displays for the left eye and the right eye displayed on the display surface 100a. Accordingly, the stereoscopic eyeglasses are configured so that the image for the left eye is viewed with the left eye of an observer, and the image for the right eye is viewed with the right eye of an observer.

(33) In the stereoscopic eyeglasses 10B as well, a wide-focus lens 16a for the left eye and a wide-focus lens 16b for the right eye are disposed corresponding to the liquid crystal shutter 50a for the left eye and the liquid crystal shutter 50b for the right eye. The stereoscopic eyeglasses 10B can also be configured by combining the liquid crystal shutters 50a and 50b and the wide-focus lenses 16a and 16b as appropriate as in the case of the stereoscopic eyeglasses 10A illustrated in FIGS. 9.

Third Embodiment

(34) An embodiment of stereoscopic eyeglasses and a method for observing a stereoscopic image, adapted to stereoscopic display using a spectral filter method, will be described.

(35) Stereoscopic display using spectral filters as optical filters is used in a case of a 3D movie. As illustrated in FIG. 12(a), in a projector 60, a color filter 62 capable of dividing a wavelength band of each of RGB colors into two is incorporated, and the projector 60 projects an image for the right eye and an image for the left eye consisting of different RGB wavelength bands on a screen 100a as a display surface.

(36) To stereoscopic eyeglasses 10C adapted to this display, as illustrated in FIG. 12(b), a spectral filter 65a for the left eye and a spectral filter 65b for the right eye are attached as optical filters. The spectral filter 65a for the left eye is configured to transmit only light having a wavelength band corresponding to the image for the left eye, and the spectral filter 65b for the right eye is configured to transmit only light having a wavelength band corresponding to the image for the right eye. Accordingly, the stereoscopic eyeglasses are configured so that the image for the left eye is viewed with the left eye of an observer, and the image for the right eye is viewed with the right eye of the observer.

(37) In the stereoscopic eyeglasses 10C, a wide-focus lens 16a for the left eye and a wide-focus lens 16b for the right eye are disposed corresponding to the spectral filter 65a for the left eye and the spectral filter 65b for the right eye. The stereoscopic eyeglasses 10C can also be configured by combining the spectral filters 65a and 65b and the wide-focus lenses 16a and 16b as appropriate as in the case of the stereoscopic eyeglasses 10A illustrated in FIGS. 9.

(38) Next, an eyeglass lens 24 as a wide-focus lens to be used for the stereoscopic eyeglasses 10A according to the first embodiment will be described. Of course, the eyeglass lens 24 can be used for the stereoscopic eyeglasses 10B and 10C of other embodiments.

(39) In the following description, the anteroposterior, the left-right, and the vertical directions as viewed from a user wearing the stereoscopic eyeglasses 10A using the eyeglass lenses 24 are respectively defined as anteroposterior, left-right, and vertical directions in the lenses.

(40) In FIG. 13, the eyeglass lenses 24 have a rear surface 2 formed as a concave surface defined by the following Equation (i), and a front surface 3 formed as a convex surface defined by the following Equation (ii). An axis in the anteroposterior direction, passing through an optical center O (basic point O.sub.1 on the rear surface 2, basic point O.sub.2 on the front surface 3) of the lenses 24, is defined as the z-axis, and a positive direction of the z-axis is set in a direction toward the rear side of the lenses 24. The z-axis matches an optical axis of the lenses 24.
z=r.sup.2/(R.sub.1+(R.sub.1.sup.2−Kr.sup.2).sup.1/2)+δ.sub.1+δ.sub.2  Equation (i)
z=r.sup.2/(R.sub.2+(R.sub.2.sup.2−Kr.sup.2).sup.1/2)  Equation (ii)

(41) r in Equation (i) and Equation (ii) is a distance from the z-axis. That is, considering an orthogonal coordinate system having an axis in the left-right direction and an axis in the vertical direction orthogonal to the z-axis, respectively set as an x-axis and a y-axis, and the basic point O.sub.1 defined as a center on the rear surface 2 and the basic point O.sub.2 defined as a center on the front surface 3, r=(x.sup.2+y.sup.2).sup.1/2. R.sub.1 and R.sub.2 are curvature radiuses at apexes of the surfaces, K (conic constant) is 1.

(42) In Equation (i) defining the rear surface 2, δ.sub.1 is an average power stabilization component expressed as Ar.sup.4+Br.sup.6+Cr.sup.8+Dr.sup.10 (r is a distance from the z-axis, and A, B, C, and D are constants). δ.sub.2 is a depth-of-field extension component expressed as Er.sup.3 (r is a distance from the z-axis, and E is a positive constant). Therefore, the lenses 24 in this example have a front surface 3 being a spherical surface and a rear surface 2 being an aspherical surface. R.sub.1 and R.sub.2 are determined according to the prescription power (0 D in this example).

(43) In this way, the lenses 24 in this example are obtained by adding the average power stabilization component δ.sub.1 and depth-of-field extension component δ.sub.2 to the refractive surface (spherical surface with a curvature radius R.sub.1 in this example, hereinafter, also referred to as an original spherical surface, shown by a reference sign S) of the lens rear surface 2 determined according to the prescription power (refer to FIG. 14).

(44) The depth-of-field extension component δ.sub.2 expressed as Er.sup.3 has an effect of substantially linearly changing average power a to the negative side along a lens radial direction from the optical center to a lens peripheral edge as shown in FIG. 15. Therefore, with the eyeglass lenses 24, a range of focusing is expanded, and the focal length can be provided with a range.

(45) The constant E can be set as appropriate according to a purpose and use. For example, in order to obtain a certain level of effect against visual fatigue in stereoscopic display and realize a comfortable life even when always wearing the eyeglasses, it is desirable to select the constant E from a range of 6.40×10.sup.−7 to 6.40×10.sup.−5. As the value of the constant E is set to be larger, a focusable range is expanded, and a range enabling comfortable stereovision can be further expanded. For example, when the constant E is set to 1.66×10.sup.−3, in a case where a pupil diameter is 5 mm, a change in average power in stereovision becomes approximately 0.5 D, and the range enabling comfortable stereovision can be expanded to, for example, the extent illustrated in Paragraphs 0035 to 0040 (example using stereoscopic eyeglasses for observation of a stereoscopic television or stereoscopic monitor).

(46) As shown in (b) in FIG. 13, when Δ is a height in the z-axis direction at a radius a based on the original spherical surface S (that is, an increase in thickness from the original spherical surface S), in a case where the constant E=7.68×10.sup.−6, a is 25 mm, and Δ is 120 μm. E=Δ/1000/a.sup.3 is satisfied (unit of a: mm, unit of Δ: μm).

(47) However, if the power distribution in a lens surface before the depth-of-field extension component δ.sub.2 is added is not constant, the effect of depth-of-field extension by the aspherical component expressed as Er.sup.3 is not stably produced. Therefore, in this example, for the purpose of temporarily making the average power substantially constant from the lens center toward a peripheral edge portion, the average power stabilization component δ.sub.1 expressed as Ar.sup.4+Br.sup.6+Cr.sup.8+Dr.sup.10 (r is a distance from the z-axis, and A, B, C, and D are constants) is added to the lens rear surface 2.

(48) Next, a method for designing the eyeglass lens 24 will be described.

(49) First, based on prescription power, a refractive surface of the front surface 3 and a refractive surface of the rear surface 2 of the lens 24 are determined. A method of this determination is well known, and is not described in detail here. Next, aspherical components are added to the refractive surface (original spherical surface S) of the rear surface 2 of the lens determined according to the prescription power. Specifically, an aspherical component is added to the refractive surface of the rear surface 2 through a first aspherical component adding step of adding an average power stabilization component δ.sub.1 that suppresses variations in average power, and a second aspherical component adding step of adding a depth-of-field extension component δ.sub.2 that extends a depth of field.

(50) In the first aspherical component adding process, average power stabilization component δ.sub.1 expressed as Ar.sup.4+Br.sup.6+Cr.sup.8+Dr.sup.10 (r is a distance from the z-axis, and A, B, C, and D are constants) is obtained and added to the refractive surface of the rear surface 2. In the lens to which average power stabilization component δ.sub.1 is added, as shown by the dashed line β in FIG. 15, the average power can be made substantially constant along a radial direction of the lens.

(51) Regarding the average power stabilization component δ.sub.1, a refractive surface shape of the rear surface 2 expressed by using the following Equation (iii) for an aspherical surface is simulated by ray tracing, and aspherical coefficients A, B, C, and D optimum for suppressing changes in power (specifically, average power as an average of refractive power in the meridional direction and refractive power in the sagittal direction) are obtained, and from values of these aspherical coefficients, the average power stabilization component δ.sub.1 can be obtained.
z=r.sup.2/(R.sub.1+(R.sub.1.sup.2−Kr.sup.2).sup.1/2)+Ar.sup.4+Br.sup.63Cr.sup.8+Dr.sup.10  Equation (iii)

(52) Here, z is a sag value in the rear surface 2, r is a distance from the z-axis, R.sub.1 is a curvature radius of apex, and A, B, C, and D are constants (aspherical coefficients).

(53) Next, in the second aspherical component adding process, the depth-of-field extension component δ.sub.2 expressed as Er.sup.3 (r is a distance from the z-axis, and E is a constant) is added to the refractive surface of the rear surface 2. In this example, for example, the constant E can be set to E=7.68×10.sup.−6. This value of the constant E is preferable when a certain level of effect is obtained against visual fatigue in stereoscopic display, and the eyeglasses are always worn. On the other hand, as the value of the constant E is set to be larger, the range enabling comfortable stereovision can be expanded.

(54) In this way, the refractive surface shape of the rear surface 2 of the lens 24 defined by Equation (i) described above is determined.

EXAMPLES

(55) Stereoscopic eyeglasses (Examples 1 and 2) of the embodiment formed by combining depth-of-field extension lenses with circular polarization films, were manufactured, and “viewability” and “eye fatigue” at the time of observation of stereoscopic display were evaluated.

(56) Stereoscopic eyeglasses (GetD circular polarization 3D eyeglasses) available on the market, including circular polarization films, were used as a comparative example, and stereoscopic eyeglasses obtained by fitting the following eyeglass lenses to the stereoscopic eyeglasses available on the market were used as stereoscopic eyeglasses of Examples 1 and 2.

(57) Data common to the eyeglass lenses used in the stereoscopic eyeglasses of Examples 1 and 2 are as follows.

(58) Refractive index: 1.608

(59) Front surface base curve: 4.12

(60) Power: 0.00 D

(61) Central thickness: 1.80 mm

(62) Outer diameter: φ75 mm

(63) Values of constants of aspherical components added to each lens are as shown in the following Table 1.

(64) TABLE-US-00001 TABLE 1 Example 1 Example 2 Constant A −1.09E−08  −1.09E−08  Constant B 3.70E−12 3.70E−12 Constant C −2.60E−15  −2.60E−15  Constant D 6.66E−19 6.66E−19 Constant E 7.68E−06 1.22E−05 Δ: Height (μm) 120 190 at effective radius a: Effective radius (mm)  25  25

(65) Subjects are four in number (age 30 to 55), and two of the four are spectacle wearers. The subjects viewed stereoscopic video content (3D movie) available on the market while wearing the stereoscopic eyeglasses of the comparative example and Examples described above. As display devices, a 23-inch wide liquid crystal display manufactured by Mitsubishi Electric Corporation and a BD/DVD player BDP-S6700 manufactured by SONY were used, and a distance between the display surface and the eyes of the subject was set to 90 to 120 cm.

(66) After viewing for a predetermined period of time, “viewability” and “eye fatigue” with the stereoscopic eyeglasses of Examples were evaluated according to 5 categories, bad, somewhat bad, unchanged, slightly better, and good, compared to the stereoscopic eyeglasses of the comparative example.

(67) FIGS. 16 and 17 illustrate evaluation results of the stereoscopic eyeglasses of Example 2. FIG. 16 shows results (number of responses: 4) obtained after 30 minutes from the start of viewing of the movie. FIG. 17 shows results (number of responses: 3) obtained after 120 minutes from the viewing start.

(68) According to these FIG. 16 and FIG. 17, a half or more of the results of evaluation on the stereoscopic eyeglasses of Example 2 were “slightly better” in both of “viewability” and “eye fatigue.” In particular, when the viewing time was long, the ratio of “slightly better” became high. Broadly similar results were also obtained with the stereoscopic eyeglasses of Example 1. These are considered to have been obtained by an effect of enlarging a stereoscopic image display range enabling comfortable stereovision by using the eyeglass lenses having a depth-of-field extension effect.

Other Modifications and Application Examples

(69) (1) The above-described embodiment is an example in which the constant E of the depth-of-field extension component Er.sup.3 added to the rear surface 2 of the lens is a positive number, however, the constant E may be a negative number. In this case, a depth-of-field extension component to gradually change the average power to the positive side from the lens optical center toward the lens peripheral edge is added. Here, in order to obtain a certain level of effect against visual fatigue in stereoscopic display and realize a comfortable life even when always wearing the eyeglasses, it is desirable to select the constant E from a range of −6.40×10.sup.−7 to −6.40×10.sup.−5. As the value of the constant E is made smaller (the absolute value is made larger), a focusable range is expanded, and the range enabling comfortable stereovision can be further expanded. For example, when the constant E is set to −1.66×10.sup.−5, in a case where the pupil diameter is 5 mm, a change in average power in stereovision becomes approximately 0.5 D, and the range enabling comfortable stereovision can be expanded to, for example, the extent illustrated in Paragraphs 0035 to 0040 (example using stereoscopic eyeglasses for observation of a stereoscopic television or stereoscopic monitor).

(70) (2) The embodiment described above is an example in which the average power stabilization component δ.sub.1 is added to the rear surface 2 of the lens, however, the average power stabilization component δ.sub.1 may be added to the front surface 3 of the lens, or can be added to both of the front surface 3 and the rear surface 2. For example, it is also possible that an average power stabilization component δ.sub.1 expressed as Ar.sup.4+Br.sup.6 (in this case, values of the constants C and D are zero) is added to the front surface 3, and further, an average power stabilization component δ.sub.1 expressed as Cr.sup.8+Dr.sup.10 (in this case, values of the constants A and B are zero) is added to the rear surface 2.

(71) (3) The embodiment described above is an example in which the depth-of-field extension component δ.sub.2 is added to the rear surface 2 of the lens, however, it is also possible that the depth-of-field extension component δ.sub.2 is added to the front surface 3 of the lens.

(72) (4) The embodiments described above illustrate a plano lens that is substantially plano as an eyeglass lens to be used for stereoscopic eyeglasses, however, an eyeglass lens in which a power component for correcting at least any of myopia, hyperopia, and astigmatism is further set can also be used.

REFERENCE SIGNS LIST

(73) 2: rear surface, 3: front surface, 10, 10A, 10B, 10C: stereoscopic eyeglasses, 14a: optical filter for left eye, 14b: optical filter for right eye, 16, 16a, 16b: wide-focus lens, 24: eyeglass lens, 25a: left eye, 25b: right eye, 42a, 42b: polarizer (polarization film), 50a, 50b: liquid crystal shutter, 65a, 65b: spectral filter, 100a: display surface, f.sub.1, f.sub.2: focal length, δ.sub.1: average power stabilization component, δ.sub.2: depth-of-field extension component