JP2000081570A5 - - Google Patents

Description

[Claims]
1. An optical characteristic variable optical element whose optical characteristics change by changing the orientation of a liquid crystal having a spiral structure, wherein the following equations (5-63), (5-64), (5-65) are used. ), (5-66), (5-67), and (5-68).
λ≤P <20λ (5-63)
λ≤P and | Γ / 2Φ | <π (5-64)
2λ≤P <20λ (5-65)
2λ≤P and | Γ / 2Φ | <π (5-66)
2/3 λ ≤ P <20λ (5-67)
2 / 3λ≤P and | Γ / 2Φ | <π (5-68)
2. The optical characteristic variable optical element according to claim 1, wherein the optical characteristics are changed by changing the frequency of an electric field applied to the liquid crystal.
3. The optical characteristic variable optical element according to claim 1 or 2, wherein a liquid crystal having a positive refractive index anisotropy is used as the optical characteristic variable optical element.
4. A varifocal lens using the optical characteristic variable optical element according to any one of claims 1, 2 or 3.
5. An imaging device including the varifocal lens according to claim 4.
6. An observation device including the varifocal lens according to claim 4.
7. Eyeglasses provided with the varifocal lens according to claim 4.

0012
[Means for solving problems]
The image pickup apparatus of the present invention is an optical characteristic variable optical element whose optical characteristics change by changing the orientation of a liquid crystal having a spiral structure, and is described in the following equations (5-63), (5-64), (5). It is characterized in that any one of -65), (5-66), (5-67), and (5-68) is satisfied.
λ≤P <20λ (5-63)
λ≤P and | Γ / 2Φ | <π (5-64)
2λ≤P <20λ (5-65)
2λ≤P and | Γ / 2Φ | <π (5-66)
2/3 λ ≤ P <20λ (5-67)
2 / 3λ≤P and | Γ / 2Φ | <π (5-68)

In order to orient the liquid crystal molecules 10 as shown in FIG. 5, fine grooves 11 having a pitch S as shown in FIG. 6 may be regularly provided. The depth of this groove 11 is 0.1 nm to several tens of nm. For example, Kikuta and Iwata, co-authored by the Optical Society of Japan, "Optical control by a lattice structure finer than the wavelength ", Optics Vol. 27, No. 1, pp. 12-17 ( It can be made by drawing exposure and etching as described in 1998). Alternatively, a mold having a groove formed by etching or the like may be formed and transferred to plastic using this mold.

This pattern may be formed on the surface of the transparent substrate 4 or 5 instead of the alignment film 3. In this case, the alignment film 3 may be omitted. Further, the fine groove 11 may be not a dent but a protrusion on the contrary.

FIG. 15 is a diagram showing a third embodiment, and is an example in which the varifocal lens shown in FIGS. 12 to 14 is used as the zoom lens. In the figure, 21A and 21B are varifocal lenses 21 shown in FIGS. 12 and the like, of which 21A is a front group and a rear group arranged in front of the aperture 26 and 21B is arranged behind the aperture 26, respectively. That is, this zoom lens is composed of a variable focal length lens 21A having a concave action, a front group having a negative refractive force, an aperture 26, a variable focal length lens 21B having a convex action, and a convex lens 29, and has a positive refractive force as a whole. It consists of a rear group, and by changing the focal lengths of the variable focal length lenses 21A and 21B without mechanically moving each lens, the focal length of the entire lens system is changed and the movement of the image plane is corrected. be able to. Also, focusing can be performed in the same manner.

Further, the liquid crystals 25b and 25G are not limited to spiral liquid crystals, and polymer-dispersed liquid crystals in which liquid crystals whose dielectric anisotropy changes with frequency are dispersed in a polymer may be used. The variable focus lens 21B is an example of an optical characteristic variable optical element using a polymer-dispersed liquid crystal.

When the value of ff exceeds the upper limit of 0.999 of the condition (9 ), the amount of polymer is reduced and the particles of the liquid crystal molecule 34 cannot be formed. If it falls below the lower limit of 0.5, the effect as a varifocal lens, that is, the amount of change in the focal length decreases.

In the state of FIG. 18, the switch 9 may be turned off as long as the orientation regulating force of the alignment film 2 is sufficient. However, when the switch 9 is turned on, the liquid crystal molecules 36 are arranged regularly, which is desirable because the scattering of light by the liquid crystal molecules 36 can be prevented.

In FIG. 12, an optical system composed of a varifocal liquid crystal lens 21 ( a lens 28 including a concave surface, a convex lens 27, and a liquid crystal lens portion 25 ) and a convex lens 29 is arranged behind the aperture 26. The convex lens 29 is provided so that the main ray is perpendicular to or substantially perpendicular to the solid-state image sensor 30, for example, the angle of the main ray is 90 ° ± 20 ° with respect to the light receiving surface of the solid-state image sensor. Further, the concave lens 28 is provided to improve the Petzval sum and correct curvature of field. Further, the convex lens 27 on the diaphragm 26 side (incident side) has a convex surface on the object side, whereby spherical aberration is satisfactorily corrected. Further, the liquid crystal lens 25 has a concave lens shape in order to correct chromatic aberration. Further, it is preferable to make any one of the lens surfaces of the lenses 27, 28, and 29 an aspherical surface so that the aberration can be corrected more satisfactorily. Further, it is preferable to position the liquid crystal lens 25 in the vicinity of the diaphragm 26 because the effective diameter of the liquid crystal lens 25 can be reduced and the thickness thereof can be reduced.

Next, FIG. 29 shows a conceptual diagram of a configuration in which the variable optical characteristic optical element of the present invention is incorporated into the objective optical system 120 of the observation system of an electronic endoscope. Also in this example, the objective optical system 125 of the observation system uses an imaging optical system including a reflective optical characteristic variable optical element 128 that performs zooming focusing. Liquid crystal 66H is used as these reflective optical characteristic variable optical elements. As shown in FIG. 29 (A), the electronic endoscope includes an electronic endoscope 111, a light source device 112 that supplies illumination light, and a video processor 113 that performs signal processing corresponding to the electronic endoscope 111. The monitor 114 that displays the video signal output from the video processor 113, the VTR deck 115 that is connected to the video processor 113 and records on the video signal, the video disc 116, and the video signal are printed out as video. The tip portion 119 of the insertion portion 118 of the electronic endoscope 111 is configured as shown in FIG. 29 (B). The luminous flux illuminated from the light source device 112 passes through the light guide fiber bundle 126 and illuminates the observation portion by the illumination objective optical system 127. Then, the light from the observation portion is formed as an object image by the observation objective optical system 125 via the cover member 124. This object image is formed on the imaging surface 123 of the CCD 122 via a filter 121 such as a low-pass filter or an infrared cut filter. Further, this object image is converted into a video signal by the CCD 122, and the video signal is directly displayed on the monitor 114 by the video processor 113 shown in FIG. 29 (A), and in the VTR deck 115 and the video disc 116. It is recorded in the video printer 117 and printed out as a video from the video printer 117.

Further, a speaker 144 is attached to the temporal frame 143 so that the stereophonic sound can be heard while observing the image. Since a playback device 146 such as a portable video cassette is connected to the display device main body 142 having the speaker 144 via the video / audio transmission code 145, the observer belts the playback device 146 as shown in the figure. It is possible to enjoy the image and sound by holding it at an arbitrary position such as a place. Reference numeral 147 in FIG. 33 is an adjustment unit for a switch, a volume, and the like of the reproduction device 146. Electronic components such as video processing and audio processing circuits are built in the display device main body 142.

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