JP2007264179A - Eyepiece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eyepiece that has a large exit pupil diameter and facilitates observation while exhibiting high imaging performance despite its more compact configuration. <P>SOLUTION: The eyepiece includes, in order from the object side to the exit pupil side, a first lens group G1 composed of a positive lens L1, a second lens group G2 composed of a negative lens L2, and a third lens G3 composed of a positive lens L3. The eyepiece satisfies conditional formula (1) that defines the appropriate range of a principal point interval PP. This shortens a distance from an object to the exit pupil and exhibits satisfactory aberration performance. Further, since the exit pupil diameter is large enough while tele-centricity on the object side is ensured, the eyepiece is suitable for observing a liquid crystal surface that has high directivity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an eyepiece that magnifies an object and observes it with the naked eye, and more particularly to an eyepiece that is suitable for observing an image displayed on a display surface of an image display device.

  Conventionally, an eyepiece is used as an optical system for magnifying and observing an image displayed on a liquid crystal display surface, for example, used in a viewfinder such as a video camera. The eyepiece is also used to easily enlarge an image displayed on a mobile phone or the like equipped with a display device to a size that is easy to see. Recently, with the increase in the number of pixels of an image sensor, the quality of an image has been improved, and the size of a display device has been significantly reduced. For these reasons, there is a demand for an eyepiece that is compact and exhibits high imaging performance.

Among conventional eyepieces for image display devices, a lens with a relatively small number of lenses is disclosed in Patent Document 1.
JP 2002-48985 A

  Although the eyepiece described in Patent Document 1 has been reduced in size by suppressing the number of lenses, there are insufficient dimensions regarding the overall length. In other words, since the distance from the image display surface is large enough to be applied to a reflective liquid crystal display device, when this is applied to a transmissive liquid crystal display device, the total length of the eyepiece lens system is increased by that distance. It will be long.

  Further, since the liquid crystal display device has directivity, it is necessary to ensure telecentricity on the liquid crystal display surface side in the eyepiece lens system. That is, it is necessary for the principal ray of light from the liquid crystal display surface to pass through the front principal point. However, in general, when trying to ensure telecentricity, the distance from the object (liquid crystal display surface) to the position of the exit pupil tends to be long, which hinders downsizing of the overall configuration.

  On the other hand, since there are many opportunities for the observer to use a video camera or a mobile phone in a situation involving vibrations of the vehicle etc., the image can be recognized relatively easily even if the relative position with the observer's pupil changes slightly. A possible ocular lens is desired.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an eyepiece having a large exit pupil diameter and easy to observe while exhibiting high imaging performance while having a more compact configuration. .

The eyepiece according to the present invention includes a first lens group composed of a single lens or a cemented lens having a positive power and a second lens group composed of a single lens having a negative power from the object side toward the exit pupil side. And a third lens group composed of a single lens having a positive power in order, satisfying the following conditional expression (1) where f is the focal length of the entire system and PP is the principal point interval: It is comprised so that it may do.
−0.7 <PP / f ≦ 0 (1)

  In the eyepiece of the present invention, the power in the first to third lens groups arranged in order from the object side is positive, negative, positive, and the negative is such that the principal point interval PP satisfies the conditional expression (1). Therefore, the distance from the object (for example, the image display surface) to the exit pupil position is shortened while the telecentricity on the object side is maintained. In addition, various aberrations are corrected well, and the exit pupil diameter is sufficiently large.

It is desirable that the eyepiece lens of the present invention is further configured to satisfy all of the following conditional expressions (2) to (5). However, the focal length of the first lens group is f1, the focal length of the second lens group is f2, the focal length of the third lens group is f3, and the optical axes of the first lens group and the second lens group The upper distance is D12, and the distance on the optical axis between the second lens group and the third lens group is D23.
0.5 <f1 / f <1.5 (2)
0.5 <| f2 / f | <2.0 (3)
0.5 <f3 / f <1.0 (4)
0.23 <(D12 + D23) / f <0.6 (5)
By doing so, the power distribution in the first to third lens groups is made more appropriate, and further downsizing is achieved.

  In the eyepiece of the present invention, it is desirable that both surfaces of the single lens in the third lens group are aspherical surfaces whose positive power is weakened from the optical axis toward the periphery. By doing so, a balance between compactness and improvement in imaging performance is achieved in a well-balanced manner.

  According to the eyepiece of the present invention, the positive first lens group, the negative second lens group, and the positive third lens group are sequentially arranged from the object side toward the exit pupil side, and the principal point Since the interval PP is set to a negative value that satisfies the conditional expression (1), it is possible to achieve compactness while ensuring telecentricity on the object side. Furthermore, since the exit pupil diameter is sufficiently large, a relatively good image can be observed even under conditions involving vibrations such as ships and vehicles, and an appropriate eye relief can be obtained. A good image can be observed in the same visual field regardless of whether or not glasses are used.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a first configuration example of an eyepiece as an embodiment of the present invention. This configuration example corresponds to the lens configuration of a first numerical example (FIG. 6) described later. 2 to 5 show second to fifth configuration examples in the present embodiment, respectively. The second to fifth configuration examples correspond to lens configurations of second to fifth numerical examples (FIGS. 7 to 10) which will be described later. 1 to 5, the left side is the object side, and the right side is the exit pupil side. The symbol Si indicates the i-th surface that is numbered sequentially so as to increase toward the exit pupil side (observer side) with the surface of the component closest to the object side as the first. The symbol Ri indicates the radius of curvature of the surface Si. A symbol Di indicates a surface interval on the optical axis Z1 between the i-th surface Si and the i + 1-th surface Si + 1. However, the symbol D0 is a surface interval on the optical axis Z1 between the image display surface S0 and the surface S1. Only in FIG. 1 incident light is shown. In the following description, the configuration example of the eyepiece shown in FIG. 1 will be basically described, and the second to fifth configuration examples will be described as necessary.

  The eyepiece is used for magnifying and observing an image displayed on the image display surface S0 such as a liquid crystal display device, a plasma display device, or an electroluminescence (EL) display device. In FIG. 1, a triangle connected by points A, B, and C indicates a region where the entire image displayed on the image display surface S0 can be observed (hereinafter referred to as a region ABC). That is, in the area ABC, a good observation image over the entire visual field can be obtained regardless of the position where the observer puts the pupil.

  This eyepiece lens has an exit pupil E.P. from the object side (the image display surface S0 side) along the optical axis Z1. A configuration in which a first lens group G1 having a positive power, a second lens group G2 having a negative power, and a third lens group G3 having a positive power are arranged in this order toward the P side. It has become.

  As in the first to fourth configuration examples, the first lens group G1 is configured by a single lens L1 having, for example, a biconvex shape in the vicinity of the optical axis Z1. Alternatively, as in the fifth configuration example, the first lens group G1 may be configured by a cemented lens of a biconvex lens L11 and a negative meniscus lens L12 having a concave surface facing the object side. Good.

  The second lens group G2 includes a single lens L2 having a negative meniscus shape, for example, a concave surface facing the object side in the vicinity of the optical axis Z1.

  The third lens group G3 is constituted by a single lens L3 having, for example, a biconvex shape in the vicinity of the optical axis Z1.

  In the first to third configuration examples, both surfaces S5 and S6 of the lens L3 (the surfaces S6 and 7 in the fifth configuration example) are aspherical surfaces. These aspheric surfaces are preferably shaped such that the positive power decreases from the optical axis Z1 toward the periphery. On the other hand, in the second configuration example, the exit pupil side surface S2 of the lens L1 and the object side surface S5 of the lens L3 are aspherical.

The eyepiece in the present embodiment is configured to satisfy the following conditional expression (1). However, f is the focal length of the entire system, and PP is the interval between the front principal point P1 and the rear principal point P2 (see FIG. 1), that is, the principal point interval.
−0.7 <PP / f ≦ 0 (1)

It is desirable that this eyepiece further satisfies all the following conditional expressions (2) to (5). However, f1-f3 are the 1st-3rd lens groups G1-G3, respectively, D12 is the space | interval on the optical axis Z1 of the 1st lens group G1 and the 2nd lens group G2, and D23 is 1st. This is the distance on the optical axis Z1 between the second lens group G2 and the third lens group G3.
0.5 <f1 / f <1.5 (2)
0.5 <| f2 / f | <2.0 (3)
0.5 <f3 / f <1.0 (4)
0.23 <(D12 + D23) / f <0.6 (5)

  Next, the operation and effect of the eyepiece of the present embodiment configured as described above will be described.

  Since the eyepiece according to the present embodiment is configured to satisfy the conditional expression (1) with a small number of lenses of three or four, the distance from the object position to the exit pupil position (hereinafter referred to as the total length). ) Has been shortened, and compactness has been realized. That is, the total length is a first interval from the front focal point to the front principal point, a second interval from the front principal point to the rear principal point, and a third interval from the rear principal point to the rear focal point. If compared to the case where the first to third intervals all have the same sign as in the conventional eyepiece, the second interval (that is, the principal point interval PP) is used in this eyepiece. Is a negative sign, the entire length is shortened accordingly. The fact that the principal point interval PP is negative means that the front principal point P1 is closer to the exit pupil than the rear principal point P2. Further, in this eyepiece lens, since various aberrations are corrected relatively well even for light rays that pass through a peripheral region away from the optical axis Z1, the exit pupil diameter is sufficiently large. In addition, telecentricity on the object side is ensured, and for example, it is possible to deal with highly directional image display devices such as liquid crystal display devices. Here, if the lower limit of conditional expression (1) is not reached, various aberrations (particularly coma aberration) are deteriorated and it is difficult to correct them sufficiently.

  Conditional expression (2) is an expression representing an appropriate range of an amount (f1 / f) representing the magnitude of the power (1 / f1) of the first lens group G1 with respect to the power (1 / f) of the entire system. Conditional expression (3) is an expression representing an appropriate range of an amount | f2 / f | representing an absolute value of the power (1 / f2) of the second lens group G2 with respect to the power (1 / f) of the entire system. Conditional expression (4) is an expression representing an appropriate range of an amount (f3 / f) representing the magnitude of the power (1 / f3) of the third lens group G3 with respect to the entire system power (1 / f). By optimizing the power distribution of the first to third lens groups G1 to G3 so as to satisfy these conditional expressions (2) to (4), various aberrations are corrected and the total length is shortened. It can be implemented in a well-balanced manner.

  Here, if the positive power of the first lens group G1 becomes too strong below the lower limit of conditional expression (2), for example, correction of field curvature will be insufficient. On the other hand, if the upper limit of conditional expression (2) is exceeded and the positive power of the first lens group G1 becomes too weak, the deflection angle of the light beam becomes insufficient, making it difficult to make the principal point interval PP negative. .

  Further, if the negative power of the second lens group G2 becomes too strong below the lower limit of the conditional expression (3), it becomes difficult to correct, for example, spherical aberration and coma aberration. On the other hand, if the upper limit of conditional expression (3) is exceeded and the negative power of the second lens group G2 becomes too weak, the curvature of field increases, and the principal point interval PP is reduced due to insufficient light deflection angle. It becomes difficult to do.

  Further, if the positive power of the third lens group G3 becomes too strong below the lower limit of the conditional expression (4), for example, correction of spherical aberration and coma aberration becomes insufficient. On the other hand, if the upper limit of conditional expression (4) is exceeded and the positive power of the third lens group G3 becomes too weak, the deflection angle of the light beam becomes insufficient. It becomes difficult to make the principal point interval PP negative.

  Conditional expression (5) defines an appropriate range for the mutual distance between the first to third lens groups G1 to G3. Here, if the first to third lens groups G3 are too close to each other below the lower limit of the conditional expression (5), it is difficult to keep the principal point interval PP negative. On the other hand, if the distance exceeds the upper limit of the conditional expression (5), it is difficult to make the principal point interval PP negative in order to ensure good aberration performance.

  As described above, according to the eyepiece of the present embodiment, the first to third lens groups G1 to G3 are configured as described above, and all the conditional expressions (1) to (5) are satisfied. As a result, it is possible to achieve compactness while maintaining high imaging performance. Furthermore, since telecentricity on the object side is secured, it is possible to cope with enlarged observation of an image display surface having high directivity such as a liquid crystal display device. In addition, since the exit pupil diameter can be made sufficiently large, the allowable range of the amount of pupil movement in the direction orthogonal to the optical axis and in the direction along the optical axis is expanded. That is, the range of the area ABC shown in FIG. 1 is extremely large. Therefore, for example, an image can be observed relatively easily even under a situation involving vibration of a ship or a vehicle. Alternatively, since there is a margin in the selection range of the eye relief, good observation can be performed regardless of whether the observation is performed using spectacles or the observation with the naked eye. Specifically, when observation is performed with the naked eye, the exit pupil E.E. If the pupil is placed at the position P, intrusion of unnecessary light can be prevented. On the other hand, when using glasses, for example, the rear exit pupil E.E. Although the pupil is arranged at the position P2, the exit pupil E.E. Good observation is possible for the same field of view as when the pupil is placed at the position of P.

  Next, specific numerical examples of the eyepiece according to the present embodiment will be described.

  Below, the 1st-5th numerical example (Examples 1-5) is demonstrated collectively. Here, FIG. 6 shows specific lens data (Example 1) corresponding to the first configuration example of the eyepiece shown in FIG. Similarly, FIGS. 7 to 10 show specific lens data (Examples 2 to 5) corresponding to the second to fifth configuration examples (FIGS. 2 to 5). 6A, FIG. 7A, FIG. 8A, FIG. 9A, and FIG. 10A show basic data portions of the lens data of each example. 6 (B), FIG. 7 (B), FIG. 8 (B), FIG. 9 (B), and FIG. 10 (B) show the data portion related to the aspherical shape in the lens data of each example.

  In the basic lens data shown in FIG. 6A, FIG. 7A, FIG. 8A, FIG. 9A, and FIG. 1 corresponding to the reference numerals Si shown in FIGS. 1 to 5, the surface of the component closest to the object side is the first, and the i th number is added so as to increase sequentially toward the exit pupil side. The number of the surface of (i = 1-6 or 1-7) is shown. In the column of the curvature radius Ri, the value of the curvature radius of the i-th surface from the object side is shown in correspondence with the symbol Ri shown in FIGS. The column of the surface interval Di also indicates the interval on the optical axis between the i-th surface Si and the i + 1-th surface Si + 1 from the object side, corresponding to the reference numerals attached in FIGS. However, D6 in Examples 1 to 4 and D7 in Example 5 are intervals on the optical axis from the surface S6 or S7 closest to the exit pupil to the exit pupil position. The unit of the value of the curvature radius Ri and the surface interval Di is millimeter (mm). In the columns Ndj and νdj, the values of the refractive index and the Abbe number for the d-line (587.6 nm) of the j-th (j = 1 to 3 or 1 to 4) lens element from the object side are shown. The symbol “*” attached to the left side of the surface number Si indicates that the lens surface has an aspherical shape. In Examples 1 and 3 to 5, the surfaces S5 and S6 of the lens L3 (surfaces S6 and 7 in Example 5) are aspherical surfaces. In Example 2, the surface S2 on the exit pupil side of the lens L1 and the surface of the lens L3. The object side surface S5 is an aspherical surface. In the basic lens data, the numerical value of the radius of curvature near the optical axis (near the paraxial axis) is shown as the radius of curvature of these aspheric surfaces.

In the numerical values of the aspheric data in FIGS. 6B, 7B, 8B, 9B, and 10B, the symbol “E” is the next numerical value. It indicates that it is a “power exponent” with a base of 10, and that a numerical value represented by an exponential function with the base of 10 is multiplied by a numerical value before “E”. For example, “1.0E-02” indicates “1.0 × 10 ⁻² ”.

  In each aspheric surface data, the values of the respective coefficients Ai, K in the aspheric surface expression represented by the following expression (ASP) are described. More specifically, Z is the length (mm) of a perpendicular line drawn from a point on the aspheric surface at a height Y from the optical axis to the tangential plane (plane perpendicular to the optical axis) of the apex of the aspheric surface. Show.

Z = C · Y ² / {1+ (1−K · C ² · Y ² ) ^1/2 } + A ₃ · Y ³ + A ₄ · Y ⁴ + A ₅ · Y ⁵ + A ₆ · Y ⁶ + A ₇ · Y ⁷ + A ₈・ Y ⁸ + A ₉・ Y ⁹ + A ₁₀・ Y ¹⁰ (ASP)
However,
Z: Depth of aspheric surface (mm)
Y: Distance from the optical axis to the lens surface (height) (mm)
K: Coefficient of quadratic surface C: Paraxial curvature = 1 / R
(R: paraxial radius of curvature)
Ai: i-th (i = 4, 6) aspheric coefficient

  FIG. 11 shows the focal length f (mm) of the entire system, the focal lengths f1 to f3 (mm) of the first to third lens groups G1 to G3, the first lens group G1 and the second lens group G2. Numerical data on the distance D12 on the optical axis and the distance D23 on the optical axis between the second lens group G2 and the third lens group G3 are shown for each example. In addition, numerical data corresponding to the conditional expressions (1) to (5) are collectively shown for each example. As shown in FIG. 11, the values of the respective examples are all within the numerical ranges of the conditional expressions (1) to (5).

  12A to 12C show spherical aberration, astigmatism, and distortion (distortion aberration) in the eyepiece of Example 1. FIG. Here, when light is incident from the exit pupil side, each aberration that is transmitted through the eyepiece and appears on the image display surface S0 on the object side is shown. Each aberration diagram shows aberrations with the d-line as a reference wavelength, while the spherical aberration diagram also shows aberrations for the F-line (wavelength 486.1 nm) and C-line (wavelength 656.3 nm). In the astigmatism diagram, the solid line indicates the sagittal direction and the broken line indicates the tangential direction. Further, FIGS. 13A to 13G show lateral aberrations in the eyepiece of Example 1. FIG. Here, EX attached to FIGS. 13 (A) to 13 (D) represents coma aberration in the tangential direction, and EY attached to FIGS. 13 (E) to 13 (G) represents coma aberration in the sagittal direction. Note that PX and PY indicate the positions of light rays on the exit pupil plane. In each aberration diagram, FNO. Indicates an F value, and ω indicates a half angle of view. Similarly, various aberrations for Example 2 are shown in FIGS. 14 (A) to 14 (C) and FIGS. 15 (A) to 15 (G), and various aberrations for Example 3 are shown in FIGS. (C) and FIGS. 17 (A) to 17 (G), and various aberrations for Example 4 are shown in FIGS. 18 (A) to 18 (C) and FIGS. 19 (A) to 19 (G). Various aberrations for Example 5 are shown in FIGS. 20 (A) to 20 (C) and FIGS. 21 (A) to 21 (G).

  As is apparent from the lens data and aberration diagrams described above, extremely good aberration performance is exhibited for each example. In addition, downsizing of the entire length has been achieved.

  The present invention has been described above with reference to some embodiments and examples. However, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, the values of the radius of curvature, the surface interval, the refractive index, and the Abbe number of each lens component are not limited to the values shown in the above numerical examples, and can take other values.

1 is a cross-sectional view illustrating a first configuration example of an eyepiece as an embodiment of the present invention and corresponding to Example 1. FIG. FIG. 5 is a cross-sectional view illustrating a second configuration example of an eyepiece lens as an embodiment of the present invention and corresponding to Example 2; FIG. 5 is a cross-sectional view illustrating a third configuration example of an eyepiece lens as an embodiment of the present invention and corresponding to Example 3; 4 is a cross-sectional view illustrating a fourth configuration example of an eyepiece lens according to an embodiment of the present invention and corresponding to Example 4. FIG. 5 is a cross-sectional view illustrating a fifth configuration example of an eyepiece lens according to an embodiment of the present invention and corresponding to Example 5. FIG. FIG. 6 is an explanatory diagram showing basic lens data and aspherical data in the eyepiece of Example 1. 6 is an explanatory diagram showing basic lens data and aspherical data in the eyepiece of Example 2. FIG. FIG. 7 is an explanatory diagram showing basic lens data and aspherical data in the eyepiece of Example 3. FIG. 6 is an explanatory diagram showing basic lens data and aspherical data in the eyepiece of Example 4. FIG. 10 is an explanatory diagram showing basic lens data and aspherical data in the eyepiece of Example 5. It is explanatory drawing which shows the numerical value corresponding to conditional expression (1)-(5) in each eyepiece lens of Examples 1-5. FIG. 4 is an aberration diagram showing spherical aberration, astigmatism, and distortion in the eyepiece lens of Example 1; FIG. 6 is an aberration diagram showing lateral aberration in the eyepiece lens of Example 1; 6 is an aberration diagram illustrating spherical aberration, astigmatism, and distortion in the eyepiece of Example 2. FIG. FIG. 6 is an aberration diagram showing lateral aberration in the eyepiece lens of Example 2. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion in the eyepiece of Example 3. 5 is an aberration diagram illustrating lateral aberration in the eyepiece lens of Example 3. FIG. FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion in the eyepiece lens of Example 4; FIG. 6 is an aberration diagram showing lateral aberration in the eyepiece lens of Example 4; FIG. 9 is an aberration diagram showing spherical aberration, astigmatism, and distortion in the eyepiece lens of Example 5. FIG. 6 is an aberration diagram showing lateral aberration in the eyepiece lens of Example 5.

Explanation of symbols

G1 to G3: first to third lens groups, S0: image display surface, Si: i-th lens surface from the object side, Ri: curvature radius of the i-th lens surface from the object side, Di: object side To the i-th lens surface to the (i + 1) -th lens surface. P ... exit pupil, Z1 ... optical axis.

Claims (3)

From the object side to the exit pupil side,
A first lens group consisting of a single lens or a cemented lens having positive power;
A second lens group consisting of a single lens having negative power;
And a third lens group consisting of a single lens having a positive power in order, and satisfying the following conditional expression (1).
−0.7 <PP / f ≦ 0 (1)
However,
f: focal length of entire system PP: principal point interval The eyepiece according to claim 1, further configured to satisfy all of the following conditional expressions (2) to (5).
0.5 <f1 / f <1.5 (2)
0.5 <| f2 / f | <2.0 (3)
0.5 <f3 / f <1.0 (4)
0.23 <(D12 + D23) / f <0.6 (5)
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group f3: Focal length of the third lens group D12: Distance on the optical axis between the first lens group and the second lens group D23: Distance on the optical axis between the second lens group and the third lens group 3. The eyepiece according to claim 1, wherein both surfaces of the single lens in the third lens group are aspherical surfaces whose positive power is weakened toward the periphery from the optical axis.

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