JP5028009B2 - Observation optical system - Google Patents

Description

  The present invention relates to an observation optical system. In particular, it is suitable for optical equipment such as a telescope, binoculars, and a camera finder system having a vibration isolating means for correcting blurring of an observation image when the observation optical system vibrates.

  In an observation optical system in an optical apparatus such as a telescope and binoculars, it is desired that an observation image has a high magnification (observation magnification). When the observation magnification is high, the image (observation image) is likely to be blurred during hand-held observation. For this reason, conventionally, skill is required to observe a still image.

  In recent years, an observation optical system having an anti-vibration means has been proposed so that a still image can be obtained even by hand (Patent Documents 1 to 7).

  In Patent Document 1, a variable apex angle prism having a variable prism apex angle is used as an anti-vibration means.

  In Patent Documents 2 to 4, an image stabilization lens group that can be decentered in the direction perpendicular to the optical axis is used as the image stabilization means, and the image blur is corrected by decentering the image stabilization lens in the direction perpendicular to the optical axis.

  In Patent Document 5, an anti-vibration lens group that can rotate about an axis perpendicular to the optical axis as a rotation axis is used as an anti-vibration means. The anti-vibration lens group is tilted around the rotation axis to perform anti-vibration.

  In the observation optical system of Patent Document 6, an objective lens (objective optical system) including a first lens group having a positive refractive power and a second lens group having a negative refractive power is formed in order from the object side to the observation side. An image is observed with an eyepiece lens (eyepiece optical system) through an image inverting means. Then, the blur of the observation image is corrected by driving the second lens group of the objective lens in a direction orthogonal to the optical axis.

The observation optical system of Patent Document 7 includes, in order from the object side to the observation side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. An image formed by the objective lens is observed with an eyepiece through an image inverting means.

Then, the third lens group of the objective lens is driven in a direction orthogonal to the optical axis to correct the blur of the observation image.

  In Patent Document 1, image stabilization is performed using a variable apex angle prism. For this reason, since the light beam passes through the prism, chromatic aberration is likely to occur.

  In Patent Documents 2 to 4, a shift system that shifts the lens group in a direction perpendicular to the optical axis is used. This shift method requires a large driving force for shifting. For this reason, it is difficult to apply to binoculars, for example.

  In Patent Document 5, the anti-vibration lens group is located near the front lens. For this reason, the anti-vibration lens group tends to increase in size.

  In Patent Document 6, the objective lens is composed of first and second lens groups having positive and negative refractive power, and the second lens group performs vibration isolation. In this lens configuration, the sensitivity can be increased by increasing the magnification of the second lens group. However, since the refractive power ratio of the lens group having positive and negative refractive powers becomes tight, a large number of lenses are required for aberration correction, and the entire lens system becomes large.

In Patent Document 7, the objective lens is composed of a lens group having positive, negative, and positive refractive power, and the third lens group performs vibration isolation. In this lens configuration, the anti-shake sensitivity when driving the third lens group is in the range of 0 <β <1 in the magnification β of the third lens group. I can't do it.

  The present invention reduces the occurrence of various aberrations due to decentering when the lens group is rotated to correct image blur, and also provides a predetermined anti-vibration sensitivity, making the lens group easy to use with a small driving force. An object of the present invention is to provide an observation optical system that can rotate and can easily observe a still image.

The observation optical system of the present invention is an observation optical system having an objective lens, an image inverting means, and an eyepiece in order from the object side to the observation side. The objective lens is a first lens group in order from the object side to the observation side. And a second lens group having a positive refractive power and a third lens group having a negative refractive power,
The third lens group displaces the imaging position of the objective lens by rotating about an axis perpendicular to the optical axis as a rotation axis.
When the focal lengths of the first lens group and the third lens group are f1 and f3, respectively, and the air conversion value of the distance from the rear principal point of the third lens group to the image plane of the objective lens is L3p,
0.65 <| f3 / L3p | <0.95
0.75 <f1 / fo <0.95
It is characterized by satisfying the following conditions.
In addition, the observation optical system of the present invention is an observation optical system having an objective lens, an image inverting means, and an eyepiece in order from the object side to the observation side. The objective lens is a first in order from the object side to the observation side. A lens group, a second lens group having a positive refractive power, and a third lens group having a negative refractive power;
The third lens group displaces the imaging position of the objective lens by rotating about an axis perpendicular to the optical axis as a rotation axis.
The third lens group includes a cemented lens of a negative lens and a positive lens disposed on the observation side, and the cemented surface has a concave shape with respect to the image plane of the objective lens, and the negative lens and the positive lens The refractive indexes of the lens materials are N3n and N3p, the radius of curvature of an arbitrary surface of the third lens group is R3i, and the distance in the optical axis direction from the object side surface of the third lens group to the rotation axis is L3c. And when
N3p <N3n
0.4 <R3i / L3c <2
It is characterized by satisfying the following conditions .

  According to the present invention, when the lens group is rotated to correct image blur, the occurrence of various aberrations due to decentration is reduced, a predetermined vibration-proof sensitivity is obtained, and the lens group can be moved with a small driving force. An observation optical system that can be easily rotated and can easily observe a still image is obtained.

  FIG. 1 is a lens sectional view of Example 1 of the observation optical system of the present invention, and FIG. 2 is an aberration diagram of Example 1 of the observation optical system of the present invention.

  The observation optical system of Example 1 has an observation magnification of 10 times, an apparent field of view of 64 degrees, a pupil diameter of 4.1, and an eye relief of 15 mm.

  FIG. 1A shows the case where the third lens unit L3 for image stabilization is not decentered, and FIG. 1B shows the case where the third lens unit L3 is decentered.

  FIG. 2A is a longitudinal aberration diagram when the third lens unit L3 is not decentered.

  FIG. 2B is a lateral aberration diagram at the image center when the third lens unit L3 is not decentered.

  FIG. 2C is a lateral aberration diagram at the image center when the third lens unit L3 is decentered.

  FIG. 3 is a lens cross-sectional view of Example 2 of the observation optical system of the present invention, and FIG. 4 is an aberration diagram of Example 2 of the observation optical system of the present invention.

  The observation optical system of Example 2 realizes an observation magnification of 15 times, an apparent field of view of 66 degrees, a pupil diameter of 3.3, and an eye relief of 15 mm.

  FIG. 4A is a longitudinal aberration diagram when the third lens unit L3 is not decentered.

  FIG. 4B is a lateral aberration diagram at the image center when the third lens unit L3 is not decentered.

  FIG. 4C is a lateral aberration diagram at the image center when the third lens unit L3 is decentered.

  In Examples 1 and 2, the light deflection angle on the object side when the third lens unit L3 is decentered is 0.3 degrees.

  At this time, the rotation angle of the third lens unit L3 is 1.4 degrees.

  In the lens cross-sectional view, the left side is the object side (light incident side), and the right side is the observation side (light emitting side).

  In the lens cross-sectional view, OBJ is an objective lens, which is composed of a first lens group L1, a second lens group L2, and a third lens group L3, and forms an object image.

  The objective lens OBJ may include a lens group, a filter, and the like on the object side or / and the observation side in addition to the three lens groups L1, L2, and L3.

  P is an erecting prism as an image inverting means, and has a function of converting an inverted image formed by the objective lens OBJ into an erecting image. In the figure, the development system is shown, but the glass block is shown.

  OCL is an eyepiece lens, which observes an object image converted into an erect image by the erecting prism P.

  IP is an eye point (observation position) and corresponds to the pupil position of the observer.

  The observation optical system has a configuration in which an object image formed by the objective lens OBJ is inverted by an erecting prism P to be an erecting image, and the erecting image is observed by an eyepiece OCL from an eye point IP.

The third lens unit L3 includes a point on the optical axis, and automatically rotates about an axis perpendicular to the optical axis as the rotation axis O, thereby displacing the imaging position. That is, the third lens unit L3 has a vibration-proof function for correcting the blur of the observation image due to the camera shake.

  At this time, there are two rotation axes that are orthogonal to each other through two points on the optical axis that are the same or slightly separated from each other.

  FIGS. 1B and 3B show a state in which the third lens unit L3 is rotated in one direction around the rotation axis O as a rotation center.

  When looking into an optical system such as a telescope by hand, the observation image may be distorted due to camera shake, making it difficult to observe.

  In particular, when the observation magnification of the observation optical system is increased, the shake of the observation image is enlarged due to camera shake, which makes it difficult to observe. Therefore, it is desirable to make the object image formed by the objective lens OBJ as stationary as possible.

  In each embodiment, image blur due to camera shake is corrected by rotating the third lens unit L3 constituting the objective lens OBJ as described above, using the anti-vibration lens as described above.

  In each longitudinal aberration diagram, the spherical aberration and the curvature of field are diopters, the distortion is%, and the lateral chromatic aberration is degree. The unit of the lateral aberration diagram is degrees. In the figure, d, F, and C represent aberrations of the wavelength d line, F line, and C line, and M and S represent aberrations of the meridional image surface and the sagittal image surface.

  In order to simplify the lens configuration of the objective lens OBJ, the objective lens OBJ as a whole can be made into a two-group configuration of the front group and the rear group, and the rear group can be decentered to perform vibration isolation.

  However, in the case of the two-group configuration, if the total lens length is determined, the decentration sensitivity regarding the refractive power of the front group and the rear group and the image shift of the image stabilizing lens group is uniquely determined, and the degree of freedom in design is lost.

  Therefore, in each embodiment, the objective lens OBJ has a three-group configuration so that the anti-vibration lens group related to image shift has a degree of freedom of decentration sensitivity. As a result, good optical performance is obtained.

  Further, instead of the rotation method of rotating the third lens unit L3, it is also possible to perform image shift by shifting in the direction perpendicular to the optical axis. However, the rotation method can provide a counterbalance and has an advantage that it can be driven with a small driving force.

  For this reason, a rotating system is used in each embodiment.

  The objective lens OBJ includes a first lens unit L1 having a positive refractive power, a second lens unit L2 having a positive refractive power, and a third lens unit L3 having a negative refractive power in order from the incident surface side. Among these, the first lens unit L1 includes a cemented lens obtained by cementing a positive lens having convex surfaces on the object side and the observation side and a negative lens having a concave surface on the object side.

  The second lens unit L2 includes a cemented lens obtained by cementing a negative lens having a convex object side surface and a meniscus positive lens having a convex object side surface.

  The third lens unit L3 includes a cemented lens obtained by cementing a meniscus negative lens having a convex surface on the object side and a meniscus positive lens having a convex surface on the object side.

  Note that the third lens unit L3 may include other lenses in addition to the cemented lens.

  The distance between the first lens unit L1 and the second lens unit L2 is preferably larger than the center thickness of each lens unit. In this case, since the objective lens OBJ is a telephoto type, the overall length can be shortened.

  The image by the objective lens OBJ is shifted in the direction perpendicular to the optical axis by rotating the third lens group L3 around the position on the optical axis and turning the axis perpendicular to the optical axis as the rotation axis O. An image shift amount is obtained by detecting a blur amount of an image formed by the objective lens OBJ due to camera shake by a known blur detection unit. A still image is obtained by controlling the rotation amount of the third lens unit L3 so as to cancel the image shift amount at this time.

  In the objective lens OBJ having the three-group configuration in each example, the lens outer diameter of the third lens unit L3 is the smallest among the objective lenses OBJ. For this reason, it is easy to correct the image shift with respect to camera shake by moving the lightweight lens group. Furthermore, it is possible to correct the image shift with quick response.

  The objective lens OBJ is subject to the condition that the optical performance does not deteriorate even when the objective lens OBJ is rotated in the direction perpendicular to the optical axis, as in the case of a normal lens configuration in which the third lens unit L3 is not eccentric.

  Therefore, in particular, the second lens unit L2 and the third lens unit L3 have appropriate lens shapes as described above. Each surface of the second lens unit L2 and the third lens unit L3 has a concave shape with respect to the imaging surface of the objective lens OBJ. With this shape, on-axis rays and off-axis rays are not refracted greatly on the lens surface, so that there is little occurrence of aberration, and even when the third lens unit L3 is rotated for anti-vibration, occurrence of aberration is reduced.

  In each embodiment, the rotation axis is located on the observation side of the objective lens OBJ.

  The distance in the optical axis direction from the object side surface of the third lens unit L3 to the rotation axis is L3c, and the focal length of the objective lens OBJ is fo.

At this time, 0.15 <L3c / fo <0.25 (1)
Is satisfied.

  In addition, when there are a plurality of rotation axes, it is the position of one of the rotation axes.

  Conditional expression (1) is for facilitating the realization of the anti-vibration mechanism and suppressing the deterioration of the optical performance due to the rotation of the third lens unit L3 while ensuring the image shift amount. If the upper limit of conditional expression (1) is exceeded, it will be difficult to secure the position of the rotating shaft due to the lens barrel structure, and if the lower limit is exceeded, the aberration change due to rotation will become large.

  More preferably, the numerical range of conditional expression (1) is set as follows.

0.16 <L3c / fo <0.22 (1a)
The amount of image shift on the imaging surface due to the change in the angle of view of the objective lens OBJ is Δyo, and the amount of eccentricity of the third lens unit L3 is Δy3. At this time, the eccentric amount Δy3 and the image shift amount Δyo are expressed by the following relational expression.

Δy3 = f3 * Δyo / L3p
The decentering sensitivity of the third lens unit L3 is f3 / L3p. F3 is a focal length of the third lens unit L3, and L3p is an air-converted value of the distance from the rear group principal point position (rear side principal point) of the third lens unit L3 to the image plane of the objective lens OBJ.

  In each embodiment, the following conditional expression (2) is satisfied in order to correct image blur due to camera shake in the third lens unit L3.

0.65 <| f3 / L3p | <0.95 (2)
If the upper limit of conditional expression (2) is exceeded, the shift amount of the third lens unit L3 becomes large. As a result, the lens barrel becomes large, which is not good. On the other hand, if the lower limit is exceeded, the shift amount becomes small, and the image blur correction amount corresponding to camera shake becomes small, which is not good.

  More preferably, the numerical range of conditional expression (2) is set as follows.

0.7 <| f3 / L3p | <0.92 (2a)
In the lens configuration of each embodiment, the entire system is made compact by using the first lens unit L1 as a lens unit having a positive refractive power. At this time, the refractive power of the first lens unit L1 satisfies the following conditional expression (3).

That is, when the focal length of the first lens unit L1 is f1, 0.75 <f1 / fo <0.95 (3)
If the upper limit of conditional expression (3) is exceeded, it becomes difficult to make the entire system compact. If the lower limit is exceeded, aberrations such as spherical aberration occur, and the optical performance deteriorates.

  More preferably, the numerical range of conditional expression (3) is set as follows.

0.80 <f1 / fo <0.93 (3a)
In each embodiment, the third lens unit L3 is composed of a cemented lens of a negative lens and a positive lens in order from the object side to the observation side, and the cemented surface is concave with respect to the image plane of the objective lens OBJ.

  The refractive powers of the negative lens and the positive lens material of the third lens unit L3 are N3n and N3p, respectively, and the curvature radius of an arbitrary surface of the third lens unit L3 is R3i.

At this time, N3p <N3n (4)
0.4 <R3i / L3c <2 (5)
Is satisfied.

  Conditional expression (4) is for making the cemented surface also have a negative refracting power in the third lens unit L3 and reducing the negative refracting power of each surface to reduce the occurrence of aberrations.

  If conditional expression (4) is not satisfied, various aberrations increase, which is not good.

  Conditional expression (5) means that an arbitrary surface of the third lens unit L3 forms a concave surface with respect to the rotation axis O. By satisfying this conditional expression (5), the aberration generated by the third lens unit L3 is made small.

  More preferably, the numerical range of conditional expression (5) is set as follows.

0.5 <R3i / L3c <1.8 (5a)
By specifying each configuration as described above, in each embodiment, high-performance optical performance in spite of a magnification of 10 times and an apparent field of view of 64 degrees, or a magnification of 15 times and an apparent field of view of 66 degrees and a high field of view. Is realized. In addition, as shown in the respective longitudinal aberration diagrams, high optical performance is maintained with little deterioration in performance when the anti-vibration lens is decentered.

  In particular, the objective lens has a three-group configuration having three lens groups of positive, positive, and negative refractive power in order, and the third lens group is rotated about an axis perpendicular to the optical axis. This achieves an observation optical system suitable for camera shake correction in which the change in optical performance is small even during image stabilization and the driving force is small.

  FIG. 5 is a schematic view of the essential part of a third embodiment of binoculars having a pair of observation optical systems according to the present invention.

  In FIG. 5, left and right polo II-type prisms PL and PR, which are erecting prisms arranged on the left and right with respect to the left and right objective lenses OBJL and OBJR, and left and right eyepieces OCLL and OCLR are provided. The eye width is adjusted by rotating the eyepieces OCLL and OCLR integrally to the left and right with the optical axes OAL and OAR of the objective lenses OBJL and OBJR as rotation axes.

  When making the image stabilization function, the left and right image stabilization lenses L3L and L3R rotate in the same amount and in the same direction in conjunction with the left and right direction and the vertical direction. By providing this mechanism, still images are always obtained as binoculars.

  As shown in the longitudinal aberration diagram of FIG. 2, the binoculars of FIG. 5 ensure good performance in a wide field of view with an observation magnification of 10 times and an observation field of view of 64 degrees.

  In this embodiment, in a telescope or binoculars with an observation magnification of about 10 to 20 times, good optical performance is maintained even when the anti-vibration lens (third lens group) is decentered, and a still image can be obtained with a small driving force. It is done.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

  FIG. 6 is a schematic view of the essential portions of Example 4 when the observation optical system of the present invention is applied to a telescope.

  In FIG. 6, the shake sensor 1 is a vibration gyro sensor, which is composed of a pitch shake sensor for detecting vertical shake and a shake sensor for detecting horizontal shake. The two sensors are configured with the sensitivity axes orthogonal to each other. ing. The blur sensor 1 detects angular acceleration and outputs the information to the microcomputer 2 as a signal.

  When the microcomputer 2 receives the shake (angular acceleration) from the shake sensor 1 as information, it calculates and calculates the rotation angle of the third lens unit L3 and outputs it to the lens actuator 3.

  The lens actuator 3 drives the third lens unit L3 to rotate or have a component in the direction perpendicular to the optical axis based on a signal from the microcomputer 2.

  The angle sensor 4 measures the rotation angle of the third lens unit L3 and outputs it to the microcomputer 2. When the output matches the value obtained by the calculation, the microcomputer 2 stops driving the lens actuator 3. To control. Anti-vibration is performed as described above.

  Next, numerical data of numerical examples 1 and 2 respectively corresponding to the first and second examples will be shown.

  In each numerical example, i indicates the order of the optical surfaces from the object side, Ri is the radius of curvature of the i-th optical surface (i-th surface), and di is between the i-th surface and the (i + 1) -th surface. The intervals, Ni and νi, respectively indicate the refractive index and Abbe number of the material of the i-th optical member with respect to the d-line.

  Surface numbers 1 to 9 are objective lenses, and surface numbers 10 to 13 are image inverting prisms. Since all the prism surfaces are flat surfaces, the radius of curvature is infinite. Surface numbers 14 to 25 are eyepieces. A surface number 26 indicates an eye point.

  Table 1 shows the correspondence with the above-described conditional expressions in each numerical example.

Cross-sectional view of a lens according to Example 1 of the present invention Aberration diagram of Example 1 of the present invention Lens sectional drawing of Example 2 of the present invention Aberration diagram of Example 2 of the present invention Schematic of Example 3 of an optical system of binoculars using a pair of observation optical systems of the present invention Schematic diagram of Example 4 of a telescope having the observation optical system of the present invention

Explanation of symbols

L1 1st lens group L2 2nd lens group L3, L3R, L3L 3rd lens group O Rotational axis position of 3rd lens group OBJ, OBJR, OBJL Objective lens P, PR, PL Erecting prism OCL, OCLR, OCLL Eyepiece OAR, OAL Objective lens optical axis IP Pupil position

Claims (5)

In an observation optical system having an objective lens, an image reversing unit, and an eyepiece lens in order from the object side to the observation side, the objective lens is arranged in order from the object side to the observation side, with the first lens group and the positive refractive power. 2 lens groups and a third lens group with negative refractive power,
The third lens group, by rotating the rotation axis an axis perpendicular to the optical axis, and to displace the imaging position of the objective lens,
When the focal lengths of the first lens group and the third lens group are f1 and f3, respectively, and the air conversion value of the distance from the rear principal point of the third lens group to the image plane of the objective lens is L3p,
0.65 <| f3 / L3p | <0.95
0.75 <f1 / fo <0.95
An observation optical system characterized by satisfying the following conditions . The third lens group includes a negative lens, a cemented lens of a positive lens disposed on the observation side, a cemented surface is concave to the image plane of the objective lens, the negative lens the positive each material refractive index of the lens N3n, N3P, the third lens group for any radius of curvature of the surface R3i, the distance in the direction of the optical axis from the object-side surface of the third lens group to the rotary shaft L3c And when
N3p <N3n
0.4 <R3i / L3c <2
The observation optical system according to claim 1, wherein the following condition is satisfied. In an observation optical system having an objective lens, an image reversing unit, and an eyepiece lens in order from the object side to the observation side, the objective lens is arranged in order from the object side to the observation side, with the first lens group and the positive refractive power. 2 lens groups and a third lens group with negative refractive power,
  The third lens group displaces the imaging position of the objective lens by rotating about an axis perpendicular to the optical axis as a rotation axis.
The third lens group includes a cemented lens of a negative lens and a positive lens disposed on the observation side, and the cemented surface has a concave shape with respect to the image plane of the objective lens, and the negative lens and the positive lens The refractive indexes of the lens materials are N3n and N3p, the radius of curvature of an arbitrary surface of the third lens group is R3i, and the distance in the optical axis direction from the object side surface of the third lens group to the rotation axis is L3c. And when
    N3p <N3n
    0.4 <R3i / L3c <2
An observation optical system characterized by satisfying the following conditions. The rotating shaft is positioned on the observation side of the third lens group, L3c a distance on the optical axis from the object-side surface of the third lens group to the rotary shaft, the focal length of the objective lens When fo
0.15 <L3c / fo <0.25
Any one of the observation optical system of claims 1 to 3, characterized by satisfying the following condition. An optical apparatus comprising the observation optical system according to claim 1.