JP2000081562A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain good images free from unsharpness, etc., at all times by providing the device with an optical characteristic variable optical element and changing the MTF characteristic of an electronic circuit, such as aberration fluctuation, or correcting the same by changing an image processing method when the optical characteristics of the optical characteristic variable optical element are changed. SOLUTION: The variable focus lens is constituted by providing transparent substrates 4, 5 with liquid crystals 1 having negative anisotropy of a refractive index, an alignment layer 2 and transparent electrodes 3. The variable focus optical element consisting of such liquid crystals 1 having the negative anisotropy of the refractive index is n0 in the refractive index of the liquid crystals on incident light when voltage is not impressed. The optical element acts as a convex lens. When a switch 9 is turned on thereafter, the refractive index to the incident light attains n=(ne+n0)/2 and lowers, where ne is the refractive index of an extraordinary ray and n0 is the refractive index of an ordinary ray. The element acts as a variable focus lens as a result of the lowering. The change in the refractive index is made continuos by changing a variable resistor 13 and the continuous changing of the focal length of the optical element is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus provided with variable optical elements such as a variable focus lens, a variable focus diffraction optical element, a variable deflection prism, and a variable focus mirror.

[0002]

2. Description of the Related Art A conventional variable focus lens uses a lens manufactured by polishing glass, and the focal length cannot be changed by the lens itself. Therefore, for example, a lens group such as a zoom lens of a camera is used. The mechanical structure is complicated because the focal length is changed by moving the section in the optical axis direction.

In order to eliminate such defects, it is necessary to change the focal length of the lens itself.
As shown in FIG. 6, an optical system using a polarizing plate 151 and a liquid crystal lens 152 has been proposed. The liquid crystal lens 152 used in this optical system includes lenses 153a and 153b, and transparent electrodes 154a and 153 between these lenses 153a and 153b.
And a liquid crystal layer 155 interposed therebetween. An AC power supply 157 is connected between the transparent electrodes 154a and 154b of the liquid crystal lens 152 via a switch 156, and an electric field is selectively applied to the liquid crystal layer 155 to change the refractive index of the liquid crystal layer. ing.

In an optical system including a polarizing plate 151 and a liquid crystal lens 152 as shown in FIG. 36, when natural light is incident on the optical system, for example, only a predetermined linearly polarized light component passes through the polarizing plate 151. Incident on the liquid crystal lens.

[0005] Here, as shown in FIG.
In the state where the liquid crystal layer 155 is turned off and no electric field is applied to the liquid crystal layer 155 of the liquid crystal lens 152, the liquid crystal molecules 155a have their major axes oriented in the same direction as the incident linearly polarized light. The focal length of 152 becomes shorter.

On the other hand, as shown in FIG. 37, when the switch 156 is on and an electric field is applied to the liquid crystal layer 155, the long axis direction of the liquid crystal molecules 155a is parallel to the optical axis. Therefore, the refractive index of the liquid crystal layer 155 decreases,
The focal length of the liquid crystal lens 152 becomes longer.

As described above, the optical system shown in FIGS. 36 and 37 changes the focal length by selectively applying an electric field to the liquid crystal lens 152.

[0008]

In the optical system using the liquid crystal lens shown in FIGS. 36 and 37, a polarizing plate 151 is disposed in front of the liquid crystal lens 152 so that only a predetermined linearly polarized light component enters the liquid crystal lens 152. Therefore, there is a disadvantage that the amount of light transmitted through the polarizing plate 151 and incident on the liquid crystal lens 152 decreases, and the light use efficiency decreases.

[0009] Further, since the utilization efficiency is low as described above, products to which this optical system can be applied are limited, and there is also a disadvantage that versatility is lacking. Another disadvantage is that it takes time to change the focal length.

The above-mentioned optical element having a variable optical characteristic such as a liquid crystal lens has a drawback that when its optical characteristic, for example, the focal length is changed, the aberration fluctuates and the flare increases.

The present invention provides an image pickup apparatus having an optical element with variable optical characteristics, wherein the image pickup apparatus corrects aberrations and flare fluctuations when the optical characteristics are changed.

[0012]

An image pickup apparatus according to the present invention has an optical characteristic variable optical element. The MTF characteristic of an electronic circuit can be used to determine the fluctuation of aberration when the optical characteristic of the optical characteristic variable optical element is changed. Or by changing the image processing method.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes embodiments of the optical characteristic variable optical element of the present invention.

The first embodiment of the optical characteristic variable optical element according to the present invention will be described with reference to a variable focus lens as an example of the optical element, for example, as shown in FIG. In FIG. 1, reference numeral 1 denotes a liquid crystal having a negative refractive index anisotropy, 2 denotes an alignment film, and 3 denotes a transparent electrode provided on transparent substrates 4 and 5.

In the optical element having such a configuration, the liquid crystal 1 having a negative refractive index anisotropy has a refractive index ellipsoid having a shape as shown in FIG. 2 and a relation represented by the following equation (1). It is characterized by having.

[0016] _{n e <n ox, n e} <n oy (1) where n _e is the refractive index of the extraordinary ray, n _ox is the x-direction polarized light refractive index of, n _oy is the refractive index in the y-direction polarized light.

The liquid crystal 1 satisfies the following equation (2). _{n ox = n oy ≡n o (} 2) provided that n _o is the refractive index of the ordinary ray.

Such a variable focus optical element made of a liquid crystal having a negative anisotropy of refractive index is oriented so that the z direction of the molecules of the liquid crystal 1 is oriented in the direction of the optical axis, that is, the Z direction when no voltage is applied. The film 3 is formed.

At this time, the refractive index of the liquid crystal with respect to the incident light is n
_o , wherein the optical element acts as a convex lens.

Next, when the switch 9 is turned on in FIG. 1, the direction of the liquid crystal molecules 10 is oriented as shown in FIG. 3, and the refractive index with respect to the incident light is reduced as shown in the following equation (3). _{n = (n e + n o} ) / 2 (3)

Due to such a decrease in the refractive power, the element has a weak refractive power as a convex lens, has a large focal length, and functions as a varifocal lens. Also, by changing the variable resistor 13, the change in the refractive index becomes continuous, and therefore the focal length of the optical element can be changed continuously.

Here, the alignment film 2 is formed so as to vertically align the liquid crystal molecules 10, and the azimuth angle A of the liquid crystal molecules 10 is adjusted.
Becomes random in the x, y plane as shown in FIG.

Therefore, no matter what kind of polarized light is incident on the optical element, it functions as a variable focus lens having the same focal length.

Note that the liquid crystal 1 originally has the property of having homeotropic alignment as shown in FIG. 1, so that the alignment film 2 does not have to be used.

Further, in order to change the orientation of the liquid crystal molecules 10, the frequency of the electric field, the magnetic field, the temperature, and the like may be changed instead of changing the voltage.

Further, even if the liquid crystal molecules 10 are regularly and substantially orthogonally aligned as shown in FIG. 5, the same effect as that shown in FIG. 4 can be obtained. At this time, the period S of the arrangement of the liquid crystal molecules 10 is
Is preferably smaller than the wavelength λ of the light used as in the following formula (4) because light scattering is reduced and flare is reduced. 0.5 nm <S <λ (4)

Here, the wavelength λ is 350 nm or more for visible light.
700 nm. That is, in the case of visible light, equation (4) is as follows. 0.5 nm <S <700 nm

In the case of near-infrared light, the wavelength λ is 650 n
m to 1200 nm, so equation (4) can be expressed as: 0.5 nm <S <1200
nm

In order to align the liquid crystal molecules 10 as shown in FIG. 5, fine grooves 11 having a pitch S as shown in FIG.
May be provided regularly. The depth of this groove 11 is 0.1 n
m to several tens of nm. For example, Kikuta
It can be formed by drawing exposure and etching as described in Iwata, "Light control optics by lattice structure finer than wavelength", Vol. 27, No. 1, pp. 12-17 (1998). Alternatively, a mold in which a groove is formed by etching or the like may be formed, and the mold may be used for transfer to plastic.

Instead of the pattern shown in FIG. 6, irregularities 12 or the like of a lattice pattern as shown in FIG. 7 may be used.
It is only necessary that the directions of the liquid crystal molecules 10 when viewed in the x and y planes are averaged. That is, it is sufficient that the refractive index of the liquid crystal 1 does not differ depending on the direction.

This pattern may be formed on the surface of the transparent substrate 5 or 6 instead of the alignment film 3. In this case, the alignment film 3 may be omitted in some cases. Further, the fine grooves 11 may protrude not concavities but on the contrary.

As described above, the liquid crystal molecules 10 in the xy plane
The liquid crystal lens which is not blurred regardless of polarization by averaging the orientation of not only the case where the liquid crystal has a negative refractive index anisotropy but also the case where a positive nematic liquid crystal represented by the following formula (5) is used. ,
An optical element of the present invention having the same configuration as that of FIG. 1 can be realized. n _e> n _o (5)

Also, polymer dispersed liquid crystal, chiral smectic liquid crystal, chiral cholesteric liquid crystal, ferroelectric liquid crystal,
Substances having an electro-optical effect and a magneto-optical effect, such as a ferroelectric liquid crystal and a ferroelectric, can also be applied to the present invention.

Each of the above-mentioned substances can be applied to the embodiments described later in detail in addition to the above-mentioned embodiments of the present invention.

FIGS. 8 and 9 show a second embodiment of the present invention, in which an electric field is applied in the direction of the optical axis and in the direction perpendicular to the direction of the optical axis, so that the orientation of the liquid crystal 14 changes at high speed. It is an example of a lens.

In these figures, the liquid crystal 14 is a liquid crystal having a negative refractive index anisotropy like the liquid crystal shown in FIG. In this embodiment, as a member to which an electric field is applied, in addition to a member including an electrode as shown in FIG. This is an optical characteristic variable optical element (variable focus lens) having a configuration including an electrode 19 that is disposed in the above-described manner, and a member for applying another electric field, such as an AC power supply 18, a switch 16, and a variable resistor 17 connected thereto.

FIG. 8 shows a state in which the switch 9 is turned on and the switch 16 is turned off in the variable focus lens, that is, the liquid crystal lens.

In order to change the focal length of the liquid crystal lens 15, the switch 9 is turned off as shown in FIG.
At about the same time, the switch 16 is turned on. As a result, an electric field is applied to the liquid crystal 14 through the electrode 19,
Changes its z direction parallel to the optical axis, so that the refractive index of the liquid crystal lens increases, the action as a concave lens increases, and the focal length changes.

FIG. 10 is a view of the liquid crystal optical element 15 shown in FIGS. 8 and 9 as viewed from the + z-axis direction, and is a view showing the arrangement position of the electrode 19 and its shape.

FIG. 11 is a sectional view showing the second embodiment shown in FIGS. 8, 9 and 10.
This is a modification of the above embodiment, in which the arrangement positions and shapes of the electrodes 19 are different from those of the above embodiments. 11A is a diagram viewed from the + z direction, and FIG. 11B is a diagram viewed from the -x direction. That is, as shown in FIG. 11A, an electrode 19 is provided on the outer peripheral portion of at least one of the transparent substrates 4 and 5 shown in FIG. 11B while being insulated from the transparent electrode 4. Almost the same effects as those shown in FIG.

In the second embodiment shown in FIG. 8 and the like, the response speed when the z-axis of the liquid crystal molecules 14 is oriented parallel to the optical axis 6 is faster than the liquid crystal lens of the embodiment shown in FIG. The feature is that you can do it.

The liquid crystal molecules 14 include a liquid crystal lens 15.
The electric field is applied when the focal length of the liquid crystal is long or short, and the method is excellent in that there is little variation in the alignment of liquid crystal molecules and light scattering is small.

The focal length of the liquid crystal lens 15 can be continuously changed by appropriately adjusting the variable resistors 13 and 17. At this time, the orientation of the liquid crystal molecules 14 is such that the switch 9 shown in FIG. 8 is on and the switch 16 is off, and the switch 9 shown in FIG.
Is in an intermediate state of the ON state.

In the above description, it has been described that the dielectric anisotropy of the liquid crystal molecules 10 or 14 with respect to the driving AC frequency is negative similarly to the refractive index anisotropy.

As an example of such a liquid crystal, a discotic liquid crystal is cited.

FIG. 12 shows a liquid crystal lens using a nematic liquid crystal 20 having a positive refractive index anisotropy and a dielectric anisotropy instead of the liquid crystal molecules 14 in the second embodiment shown in FIG. It is a variable focus lens 21. Therefore, the following equation (5) holds. n _e> n _o (5)

The nematic liquid crystal 20 has a pitch P
Orientation.

FIG. 12 shows a digital camera image pickup apparatus using the variable focus lens. In the variable focus lens used in the imaging apparatus shown in FIG. 12, the direction of one liquid crystal molecule 20 is substantially parallel to the XY plane. The value of the pitch P of the liquid crystal is the wavelength λ of light using the varifocal lens 21.
20 to 60 times or less of the liquid crystal molecules 2
0 can be regarded as a practically isotropic medium.

It is assumed that the pitch P is equal to or smaller than the wavelength λ, that is, as shown by the following equation (6). P <λ (6)

Then, the liquid crystal approaches an isotropic medium. The reasons will be described below.

Now, it is assumed that the following condition (5-1) is satisfied. P << λ (5-1)

As described above, when the pitch P is very small as compared with the wavelength λ of light, the liquid crystal is a medium having a refractive index n ′ given by the following (5-2) regardless of the polarization of the incident light. Works. _{n '= (n e + n} o) / 2 (5-2)

Next, the reason why the nematic liquid crystal of this embodiment effectively behaves as an isotropic medium having a refractive index n 'will be described with reference to Jones' vector and matrix.

According to the equation shown on pages 85 to 92 of "Konomi Yoshino and Masanori Ozaki", published by Corona Co., Ltd., "Basics of Liquid Crystal and Display Applications", the absolute phase change exp (-
i.alpha) when including matrix W _t Jones for nematic liquid crystal thickness d shown in FIG. 12 below formula (5
Given in 3).

Here, Φ, Γ, α, X, and R (−Φ) are represented by the following equations (5-4), (5-5), (5-6), and (5-6).
-7) and (5-8). Φ = 2πd / P (5-4) Here, ordinary light is defined as polarization in the short axis direction of liquid crystal molecules, and extraordinary light is defined as polarization in the long axis direction of liquid crystal molecules, or polarization in the direction when the long axis is projected on a plane perpendicular to the optical axis. Then Γ
Represents the phase difference between ordinary light and extraordinary light by the nematic liquid crystal.

Φ is the number of the liquid crystal molecules of the nematic liquid crystal,
The torsion angle is expressed in radians. The formula (5-
3), the coordinate system of equation (5-8) is represented by x, y,
It is taken like the z-axis. That is, the x-axis is from the front to the back of the paper, and the y-axis is the direction of the long axis of the liquid crystal molecules on the plane of incidence of the chiral nematic liquid crystal. The formula (5-
Under the condition of 1), let us examine what W _{t in} the equation (5-3) looks like.

The equation (5-1) can be transformed into the following equation (5-9). 0 <P / λ << 1 (5-9)

Therefore, when p / λ → 0, W in equation (5-3)
_Find the limit value W _t L of _t .

Γ / Φ is given by (5-10). _{Γ / Φ = (n e -n} o) (P / λ) (5-10)

Therefore, when P / λ << 1, Γ / Φ is as shown in equation (5-11).

| Γ / Φ | << 1 (5-11)

Therefore, when P / λ → 0, | Γ / Φ | →
It becomes 0.

Under the condition of equation (5-11), equation (5)
X in -7) is the following formula (5-12), (5-13),
(5-14). When P / λ → 0, X → Φ (5-16) cosX → cosΦ (5-17) Therefore, when P / λ → 0, W _tL becomes as (5-20).

[0064] This is the refractive index _{n '= (n e + n} o) / 2, the thickness d, none other than isotropic medium Jones matrix along the optical axis.

Therefore, since P / λ << 1, the varifocal lens 21 shown in FIG. 12 functions as a lens having a refractive index n ′, and an image without blur can be realized.

[0066] Incidentally, even when the liquid crystal is intermediate sequence as shown in FIG. 14, the value of n _e, by replacing in n _e and n _o of some intermediate value a is extraordinary light refractive index n _e ' , (5-3) to (5-20) described above can be satisfied.

By applying the configuration as shown in FIG. 12, the method of applying the voltage is not limited to the continuous variable, and the variable voltage may be selected from several discrete voltage values. A focus lens can be realized.

Here, a practical example of the variable focus lens having the configuration shown in FIG. 12 will be described in detail.

Equation (5-20) shows the limit case of P / λ → 0. However, since the limit value may not always be applied to an actual liquid crystal lens or varifocal lens, equation (5-20) is used. Let us derive the approximate expression of -3). P / λ <1
It is not necessary.

Equation (5-3) is approximated by considering the first order of P / λ as follows. That is, equation (5-12)
In the expression (5-14), up to the first order of P / λ, that is, the expression (5-
From equation (10), if the first order of Γ / Φ is left and the second or higher order of Γ / Φ is omitted, equation (5-21) is obtained.

These formulas (5-20), (5-21),
The following formula (5-23) is obtained from (5-22).

Therefore, in order for the value of W _tN to be considered substantially equal to the Jones matrix of the isotropic medium, | i · Γ
/ 2Φ | should be close to 0. At this time, W _tN is given by the following equation (5)
-24).

The equation (5-24) means that the liquid crystal rotates by the polarization direction of the incident light Γ / 4 · Γ / Φ, but can be regarded as an isotropic medium.

Therefore, the expression (5-25) is satisfied.
That is, if approximately the expression (5-26) is satisfied, a variable-focus lens that does not blur can be obtained.

| I · (Γ / 2Φ) | ≒ 0 (5-25) | Γ / 2Φ | <0.11 (5-26) From equation (5-10), Γ / 2Φ is calculated by the following equation (5- 27).

When the variable focus lens of the present invention is used for a lens of a relatively low-cost product such as an actual imaging device with a lens, for example, an electronic camera, a VTR camera, an electronic endoscope, etc. In some cases, high resolution is not required, so that the condition of the equation (5-26) can be relaxed, and the condition (5-28) below must be satisfied. | Γ / 2Φ | <1 (5-28)

Since high resolution is required for lenses of electronic imaging devices having a large number of pixels, lenses of high image quality such as film cameras and microscopes, it is desirable to satisfy the following condition (5-29). | Γ / 2Φ | <π / 6 (5-29)

In the case of a lens not used for imaging, such as a lens of an optical disk, or an electronic image pickup device having a small number of pixels, the conditions are further relaxed, and the following condition (5-30) may be satisfied. | Γ / 2Φ | <π (5-30)

As can be said in common with this embodiment, when the liquid crystal has a helical arrangement, when the major axis direction of the liquid crystal molecules is not perpendicular to the optical axis, that is, when the liquid crystal molecules are oblique, equation (5-1), the formula (5-26) to formula a n _e of (5-30) may be replaced by the above n _e '.

Next, a design example will be described.

When the thickness d of the nematic liquid crystal is small, the lens power is weak and useless. When the thickness d is large, light is scattered and causes flare. Therefore, the thickness d may satisfy the following condition (5-31). desirable. 2μ <d <300μ (5-31)

The wavelength λ of light is in the range of the following condition (5-32) in consideration of visible light. 0.35μ <λ <0.7μ (5-32)

[0083] In addition, the value of n _e -n _o is determined by the physical properties of the liquid crystal,
There are many substances in the following range (5-33). _{0.01 <| n e -n o |} <0.4 (5-33)

Next, the following first to fourth design examples are shown as design examples. The first design example _{d = 15μ λ = 0.5μ n e} -n o = 0.2 P = 0.06μ thus Γ / 2Φ = (1/2) · 0.2 × 0.06 / 0.5 =
0.012, and the expressions (5-20), (5-28), and (5-2)
9), satisfying the expression (5-30).

[0085] The second design example _{d = 50μ λ = 0.6μ n e} -n o = 0.25 P = 0.5μ Therefore Γ / 2Φ = (1/2) · 0.5 × 0.25 / 0. 6 =
0.1042, and the formula (5-26), the formula (5-28), and the formula (5-2)
9), satisfying the expression (5-30).

[0086] The third design example _{d = 100μ λ = 0.55μ n e} -n o = 0.2 P = 3μ Thus Γ / 2Φ = (1/2) · 0.2 × 3 / 0.55 = 0. 5
454, thereby satisfying the expressions (5-28) and (5-30).

[0087] The fourth design example _{d = 200μ λ = 0.95μ n e} -n o = 0.2 P = 7μ Therefore Γ / 2Φ = (1/2) · 0.2 × 7 / 0.95 = 0. 7
37, thereby satisfying the expressions (5-28) and (5-30).

In each of the above design examples, a chiral nematic liquid crystal has been described as an example. In order to make the spiral pitch of the nematic liquid crystal smaller than the wavelength of light using a chiral agent, a chiral agent may be mixed with the liquid crystal.

As the chiral agent, a cholesteric liquid crystal or a synthetic optically active compound is used. The following chemical formulas (1) and (2) are examples of nematic liquid crystals, and chemical formulas (3) and (4) are examples of chiral agents.

[0090] In Formula (5-30), exhibition type specific Considering the example of the liquid crystal n _e -n _o = 0.1 as (1/2) × 0.1 (P / λ) <π than P <20π · λ ≒ 62.8λ (5-61) is obtained. Similarly, when applying the n _e -n _o = 0.1 in equation (5-28), P <20λ ( 5-6
2) is obtained.

Therefore, by satisfying the expression (5-61) or the expression (5-62) by using a product using liquid crystal, a variable-optical-characteristic optical element such as a variable-focus lens with less blurring (flare) can be obtained. Also, the formulas (5-1) to (5-
30) applies not only to nematic liquid crystals but also to all liquid crystals having a helical structure with a pitch P. Examples of such liquid crystals include cholesteric liquid crystals, smectic liquid crystals, ferroelectric liquid crystals, antiferroelectric liquid crystals, and the like.

FIG. 13 is a view of the varifocal lens 21 used in the image pickup apparatus shown in FIG.
a, 22b, 22c, 23a, 23b, and 23c are divided into six parts on the outer periphery of the varifocal lens 21 and are arranged insulated from the transparent electrode 4. These electrode pairs 22a-23a, 2
AC voltages are sequentially applied to the switches 2 b-23 b and 22 c-23 c by the triple switch 24. By changing the direction of the electric field, the orientation of the liquid crystal can be made almost isotropic. If an electric field is applied in only one direction, the spiral of liquid crystal molecules may be unwound.

Next, the operation of the apparatus shown in FIGS. 12 and 13 will be described.

First, when the switch 9 is on, the triple switch 24 is off. As a result, the liquid crystal molecules 20 have the molecular major axis substantially parallel to the optical axis. At this time, the liquid crystal lens unit 25 becomes a concave lens having a low power.

Next, when the switch 9 is turned off and the triple switch 24 is turned on at the same time, since a horizontal electric field is applied to the liquid crystal molecules 20, the molecules 20 are oriented at high speed as shown in FIG.
Changes as shown.

The switching period T of the voltage applied to the three electrodes of the triple switch 24 must satisfy the following relationship.

In the optical system shown in FIG.
When the switch 9 is turned off at a certain time while the switch 9 is turned on and the switch 9 is turned on, the liquid crystal molecules 20 are naturally turned on as shown in FIG. Orientation.

As described above, assuming that the time until the orientation naturally becomes as shown in FIG. 12 is τ, it is necessary to have the following relationship. T ≦ τ (7) If T is too large and does not satisfy the above (7), the helix of the liquid crystal molecules 20 may be loosened, and the alignment of the liquid crystal molecules 20 may become a homogeneous alignment parallel to the alignment film 2.

The above equation (7) is practically the following equation (7-
It is only necessary to satisfy 1). T ≦ 10τ (7-1) If the expression (7-1) is not satisfied, if the voltage applied to the electrodes 22 and 23 is weak, it may take time until the liquid crystal molecules 20 are completely helically aligned. Because.

After the orientation of the liquid crystal molecules 20 has once returned to the state shown in FIG. 12, the triple switch 24 may be continuously turned off. That is, even when the switch 9 is turned off from the homeotropic alignment in which the alignment of the liquid crystal molecules 20 is parallel to the optical axis 7, the triple switch 24 is turned on only until it changes to a helical alignment as shown in FIG. You may keep it. This advantageously saves electricity.

Also, as shown in FIG. 14, the variable resistors 13 and 17 are appropriately adjusted so that the direction of the liquid crystal molecules 20 is obliquely arranged with respect to the optical axis.
Can be continuously changed. That is, it is convenient to use it for a zoom lens or the like.

FIG. 15 shows the third embodiment.
15 is an example in which the varifocal lens shown in FIGS. 12 to 14 is used for a zoom lens. In the figure, reference numerals 21A and 21B denote variable focus lenses 21 shown in FIG.
A denotes a front group and 21B denotes a front group and a rear group disposed behind the stop 26, respectively. That is, this zoom lens has a front group of negative refractive power composed of a variable focal length lens 21A having a concave function, a diaphragm 26, a variable focal length lens 21A having a convex function and a convex lens 29, and has a positive refractive power as a whole. The rear lens group includes a rear lens group. By changing the focal length of the varifocal 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.
In addition, focusing can be performed similarly.

In this example, instead of changing the intensity of the electric field applied to the liquid crystal 25b when driving the varifocal lens 21A to change its focal length, the frequency of the electric field is changed to f ₁ ,
The liquid crystal is changed in four steps of f ₂ , f ₃ , and f ₄ , and a liquid crystal whose sign of dielectric anisotropy changes depending on the frequency is used as the liquid crystal. The frequencies f ₁ , f ₂ , f ₃ , f ₄ are set to f ₁ <f ₂ <f ₃ <
dielectric anisotropy of liquid crystal 25b When f ₄ are choosing to code are reversed between f ₁ and f _4.

In this zoom lens, the switch 24
To change the frequency. In this case, the electrode 22F may be omitted. The frequency is f ₁ ,
f _2, f _3, may be changed continuously instead of stepwise change as f _4. Further, the intensity of the electric field may be changed simultaneously with the change of the frequency.

The liquid crystals 21A and 21B are not limited to helical liquid crystals but may be polymer dispersed liquid crystals in which liquid crystals whose dielectric anisotropy changes with frequency are dispersed in polymers. The varifocal lens 21B is an example of an optical characteristic variable optical element using a polymer dispersed liquid crystal.

An AC power supply 9e capable of continuously changing the frequency is connected to the two electrodes 3, and the focal length of the optical element can be changed by changing the frequency of the AC power supply.

The liquid crystal lens 21A and the liquid crystal lens 21B
The zooming can be performed by interlocking with. Focusing can be performed by changing only the liquid crystal lens 21B.

The electrode 22G may not be used, and the voltage applied to the electrode 22G may be changed in conjunction with the change in the frequency f of the AC power supply 9e.

In the imaging device shown in FIG. 12, a chiral cholesteric liquid crystal, a chiral smectic liquid crystal, a ferroelectric liquid crystal, an antiferroelectric liquid crystal, a liquid crystal having a negative refractive index anisotropy are used instead of the liquid crystal molecules 20. A ferroelectric polymer dispersed liquid crystal or the like may be used. When these liquid crystals are used, the above formula (6)
(7), (7-1), (5-26), (5-28),
(5-29), (5-30), (5-61), (5-6)
2) applies similarly.

The optical system shown in FIGS. 16 and 17 is different from the optical system shown in FIG. 12 in that nematic liquid crystal 34 having an average diameter of D is arranged in a polymer instead of liquid crystal molecules 20 in a granular form. .

The example shown in FIGS.
2 and 23 operate in the same manner as in FIG.
Around the periphery of the transparent electrodes 2 and 33, the transparent electrodes 3 are insulated. The operation of the triple switch 24 is the same as that of the optical system shown in FIGS.

In the optical system shown in FIGS. 16 and 17, the switch 9 is on, the liquid crystal molecules 29 are in a homeotropic alignment state as shown in FIG. 16, the switch 9 is turned off, and the triple switch 24 is turned on. To turn on the liquid crystal molecules 29
In addition, a horizontal electric field is applied to the liquid crystal molecules 29, and the liquid crystal molecules 29 are oriented at a high speed, albeit somewhat randomly, in parallel to the xy plane, as shown in FIG. Equations (7) and (7-1) are both shown in FIG.
The same applies to the optical systems 6 and 17.

As described above, that is, as shown in FIG. 17, the arrangement of the liquid crystal molecules 29 is excellent in that the change in the refractive index of the liquid crystal 35 is close to a right angle to the optical axis 6 and the refractive index changes further.

Here, it is desirable that the average diameter D of the liquid crystal molecules 34 satisfies the following condition (8), since scattering of light can be prevented. D <λ / 5 (8) where λ is the wavelength of the incident light.

When the thickness of the liquid crystal 35 is small, the expression (8)
If the following expression (8-1) is satisfied instead of the above, there is no practical problem. D <2λ (8-1)

When the ratio of the liquid crystal molecules 34 to the entire volume of the liquid crystal 35 is ff, it is desirable that the following condition (9) is satisfied in order to sufficiently obtain the effect as a variable focus lens. . 0.5 <ff <0.999 (9)

The value of ff is the upper limit of condition (10) 0.999
When the value exceeds, the amount of the polymer decreases, and the particles of the liquid crystal molecules 34 cannot be formed. If the lower limit of 0.5 is not reached, the effect as a varifocal lens, that is, the change amount of the focal length decreases.

When it is desired to make the liquid crystal 35 close to a solid state by increasing the amount of the polymer, the following condition (9) is used instead of the condition (9).
It is desirable to satisfy -1). 0.1 <ff <0.5 (9-1)

FIG. 18 shows another embodiment of the optical system according to the present invention, and shows an example of an optical system in which the refractive index of the liquid crystal is changed by changing the temperature.

Nematic liquid crystal 3 having positive refractive index anisotropy
6, when the temperature is equal to or lower than the transition temperature T _C , as shown in FIG.
Homeotropic orientation with the molecular long axis oriented in the direction
This is a state where n _O has a low refractive index. At this time, the switch 9 is on as shown.

[0121] Next, turn on the switch 43 of the heater 41, the temperature of the liquid crystal molecules 36 becomes higher than the transition temperature T _C by heating the liquid crystal by the heater 41 1
As shown in FIG. 9, the liquid crystal molecules 36 become a transparent liquid that moves randomly. At this time, the switch 9 is turned off.

In the state shown in FIG. 19, the liquid crystal molecules 36
Is given by the following equation (10). _{n = (2n O + n e} ) / 3 (10)

That is, the refractive index n of the liquid crystal increases, and as a result, the refractive power of the convex lens 32b increases.

In the state of FIG. 18, the switch 9 may be turned off if the alignment regulating force by the alignment film 2 is sufficient.
However, it is desirable to turn on the switch 9 because the liquid crystal molecules 36 are regularly arranged, so that light scattering by the liquid crystal molecules 33 can be prevented.

The optical system shown in FIGS. 18 and 19 was heated using a heater 41 in order to cause the liquid crystal to undergo a phase transition to a liquid. The phase transition may be caused by increasing the temperature by increasing the temperature.

The optical characteristic variable optical element according to the present invention described above was carried out mainly by changing the intensity and direction of the electric field in order to change the orientation of liquid crystal molecules constituting the optical element.

However, the orientation of the liquid crystal molecules can be changed by changing the frequency of the electric field applied to the liquid crystal without being limited to the change of the electric field strength. Also, the orientation of the liquid crystal molecules can be changed by changing the strength of the magnetic field.

The method of changing the orientation of the liquid crystal molecules by changing the frequency of the electric field applied to the liquid crystal and the method of changing the strength of the magnetic field applied to the liquid crystal are as follows.
For example, the present invention can be applied to the optical systems shown as examples in FIGS. 1, 3, 8, 9, 12, 15, 15, 16, 19, and 20.

In the method of changing the orientation of liquid crystal molecules by changing the frequency of an electric field, if a liquid crystal whose dielectric anisotropy is switched between positive and negative is used, the orientation of the liquid crystal molecules can be changed at a high speed by changing the frequency of the electric field. It is particularly advantageous to obtain.

FIG. 20 shows an example of a lens whose refractive index is changed by a magnetic field H. In this figure, 45 is a lens, 46 is a substance having a magneto-optical effect, 47 is a substrate, 48
Is an alignment film, 49A is a switch, 49B is an AC power supply, 49
C is a variable resistor, 49D is a coil, and 49E is an iron core.

Examples of the substance 46 having a magneto-optical effect include lead glass, water length, and liquid crystal. It is better to provide the alignment film 48 in the case of liquid crystal.

In order to change the orientation of liquid crystal molecules at high speed, it is preferable to apply a certain voltage in advance in place of the off state. Then, when it is desired to change the orientation of the liquid crystal molecules, the orientation of the liquid crystal molecules can be changed at a high speed by increasing the voltage.

The example shown in FIG. 12 described above is an image pickup apparatus for a digital camera of the present invention using an optical characteristic variable optical element. This example will be described in further detail.

In FIG. 12, a varifocal liquid crystal lens 21, a lens 28 including a concave surface, and a convex lens 4
2 and an optical system configured by the liquid crystal lens unit 25 are arranged. The convex lens 42 is provided so that the principal ray is perpendicular or almost perpendicular to the solid-state imaging device 30, for example, at an angle of 90 ° ± 20 ° to the light receiving surface of the solid-state imaging device. The concave lens 28 is provided for improving Petzval sum and correcting curvature of field. The convex lens 27 on the aperture 26 side (incident side) has a convex surface on the object side, so that spherical aberration can be satisfactorily corrected. The liquid crystal lens 25 has a concave lens shape to correct chromatic aberration. Also, lens 2
By making any one of the lens surfaces 7, 28 and 29 aspherical, aberrations can be more favorably corrected, which is preferable. It is preferable that the liquid crystal lens 25 is located near the stop 26 because the effective diameter of the liquid crystal lens 25 can be reduced and the thickness thereof can be reduced.

When the orientation of the liquid crystal molecules 20 in the liquid crystal lens 25 changes, the convex lens 27, the liquid crystal lens 25,
The aberration of the optical system composed of the concave lens 28 and the convex lens 29 fluctuates, and the magnitude of the scattering of light generated by the liquid crystal lens 25 also changes, whereby the MTF of the optical system 31 changes.

In the image pickup apparatus shown in FIG. 12, the change in MTF due to the change in aberration and the change in the magnitude of light scattering is corrected by an electronic circuit.
That is, the MTF when the focal length of the liquid crystal lens 25 is changed in order to perform focusing by changing the object position
Is compensated for by changing the processing of the enhancement circuit or the image processing circuit in the circuit 44. Specifically, means for changing the characteristics of a digital filter such as a Wiener filter, or changing the amount of edge enhancement of an enhancement circuit may be used. Where MTF
May be obtained from the design data of the optical system 31, or the MTF compensation amount may be changed by measuring each actual camera one by one.

FIG. 35 is a diagram for explaining the correction by the electronic circuit. FIG. 35 shows an example in which distance measurement is performed by an infrared light projection type active distance measurement method. Based on the distance information obtained here, an enhancement amount or the like is selected so as to compensate for the MTF change of the liquid crystal lens. Then a digital filter is applied to create the final image.

FIG. 21 is a view showing another example of the image pickup apparatus of the present invention, which is an example of a digital camera 50 using a free-form surface lens 51 (a lens having a non-rotationally symmetric surface). 52 is a variable focus mirror, 53 is an aluminum-coated thin film, 54 is an electrode, 55 is a solid-state imaging device, 56 is a substrate,
7 is a power supply, 58 is a switch, and 59 is a variable resistor.

As an example of the variable focus mirror 52, Optics Communications (Optics Co.)
munications), 140 volumes (1997)
There is a membrane mirror shown on pages 187 to 190, and when a voltage is applied between the electrodes 54, the thin film 53 is deformed by electrostatic force and the focal length of the reflecting mirror changes. And the focus can be adjusted. Light 60 from the object is refracted by the surfaces R ₁ and R ₂ of the free-form surface prism 51, reflected by the reflecting mirror (thin film) 53, reflected by the surface R ₃ of the free-form surface prism 51, and refracted by the surface R _4. And then the solid-state imaging device 5
5 is incident.

As described above, this device has a free-form surface R ₁ ,
An imaging optical system is constituted by R ₂ , R ₃ , R ₄ and the reflecting mirror 53. In particular, the aberration of the object image is minimized by optimizing the shapes of the free-form surfaces R ₁ , R ₂ , R ₃ , and R ₄ .

In the imaging device shown in FIG. 21, the shape of the opening of the reflecting mirror is preferably an ellipse long in the Y-axis direction in order to correct astigmatism and the like. It is preferable that the shape be long elliptical in the direction of the line of intersection of the plane containing the incident light on the reflecting mirror 52 and the light emitted from the reflecting mirror 52 and the reflecting mirror 52. In the example shown in this figure, the reflecting mirror 52, the thin film 53, and the solid-state imaging device 55 are formed separately and are arranged on the substrate 56. However, the reflector 5
Since the substrate 2 and the thin film 53 can be formed by a silicon lithography process or the like, the substrate 56 may be formed of silicon, and at least a part of the reflecting mirror 52 may be formed on the substrate 56 by a lithography process together with the solid-state imaging device 55.

Thus, the reflecting mirror 52 is integrated with the solid-state imaging device 55, which is advantageous in terms of miniaturization and cost reduction. The reflecting mirror 52 may be a fixed focus mirror. Even in this case, the reflecting mirror 52 can be made by a lithography process.

Although not shown, a reflection type liquid crystal display or a transmission type liquid crystal display may be integrally formed on the substrate 56 by a lithography process. The substrate 56 may be formed of glass, and a solid-state imaging device or a liquid crystal display may be formed on the glass substrate by a technique such as a thin film transistor.

It should be noted that the free-form surface prism 51 can be easily formed with a curved surface of any desired shape by being formed with a plastic mold, a glass mold, or the like, and is easy to manufacture.

FIG. 22 shows another example of a digital camera using a free-form surface prism 51. This digital camera is
This is an example in which a variable focus mirror 61 is used instead of the reflecting mirror 52 in the digital camera shown in FIG.

[0146] variable focal-length mirror 61, is provided on the surface R ₂ of the free-form surface prisms 51 integrally with the prism 51.
The varifocal mirror 61 includes a reflecting mirror 62, a transparent electrode 63 formed on the surface R ₂ of the free-form surface prism, an alignment film 64,
A liquid crystal 66 is provided between the alignment films 64 and 65.

[0147] Here, a variable focal-length mirror 61, formed in a separate and free-form surface prisms 51 body may be bonded to each other, and the transparent electrode 63 on the surface R ₂ of the free-form surface prism and the alignment layer 64 May be formed.

Light 60 incident on a digital camera from an object
Is a free-form surface prism 51 similar to the camera shown in FIG.
Are respectively refracted by the surface R _1, R _2, is reflected by subsequent reflection mirror 62, an alignment film 64, liquid crystal 65, alignment layer 63 through the transparent electrode 62 and incident on the free-form surface prisms 51, the surface R ₃
Is emitted from the to surface R ₄ reflected by the incident on the light receiving surface of the solid-state imaging device 55. Here, by changing the voltage applied to the variable focus mirror 61, it is possible to change the focal length of the mirror 61 and adjust the focus.

The liquid crystal 6 used in the variable focus mirror 61
6, a polymer-dispersed liquid crystal is used.
6, as described with reference to FIG. 17, by changing the electric field applied to the liquid crystal molecules, for example, the state shown in FIG. 16 changes to the state shown in FIG. 17, whereby the refractive index of the liquid crystal changes, The focal length of the focusing mirror changes.

In the case of the embodiment of the digital camera shown in FIG. 22, the electrodes 22 and 23 used in the digital camera shown in FIG. Has the action of

That is, in FIG. 22, when the switch 58 is turned off, the arrangement of the liquid crystal is random, and the liquid crystal is in a high refractive index state. Therefore, the variable focus mirror 61 has a strong effect of converging light. Here, when the switch 58 is turned on, the liquid crystal is aligned in one direction, so that the refractive index is lowered and the effect of converging light is weakened. Therefore, the focus of the variable focus mirror 61 is adjusted.

By using two or more variable focus mirrors 61 for the free-form surface prism 51, it becomes possible to use them as zoom lenses.

The variable focus mirror 52 of the digital camera shown in FIG. 21 may be replaced with a variable focus mirror 61 shown in FIG. The alignment films 64 and 65 need not be used.

As the liquid crystal optical element of the variable focus mirror 61, the transparent electrode 63 may be replaced by a reflecting mirror 62 also serving as an electrode.

In place of the polymer-dispersed liquid crystal 66, a helically aligned nematic liquid crystal, a cholesteric liquid crystal, a smectic liquid crystal, or the like may be used.

FIG. 23 shows an example in which a diffractive optical element 70 is used instead of the reflecting mirror 53 or the variable focus mirror 61 in the digital camera shown in FIG. 21 or FIG. That is, the diffractive optical element 70 is a diffractive surface 71 formed on the reflecting mirror 72.
, A transparent electrode 73, an alignment film 74, and a liquid crystal 75.

The digital camera 76 shown in FIG.
Light from the object enters the free-form surface prism as in the other examples, passes through the prism 51, enters the diffractive optical element 70, where it undergoes a diffractive action on the diffractive surface 71. The light exits and enters the free-form surface prism 51 again, is reflected as shown in the drawing, and then exits and enters the solid-state imaging device 55.

When the switch 77 is turned on, the orientation of the liquid crystal molecules changes in the vertical direction and the diffraction order of the diffractive optical element 70 changes, so that the focal length changes and focusing can be performed.

Here, the pitch of the liquid crystal molecules satisfies the expression (6) as in the case of the liquid crystal shown in FIG. In this example, the diffraction surface 71 is a reflection surface, and is an example of a reflection type diffractive optical element.

FIG. 24 shows an example of variable focus glasses using the variable focus lens shown in FIG. That is, a variable focus lens is used as the spectacle lens, and the lenses 30H, 31H
In this configuration, a varifocal lens including an alignment film (not shown), an electrode 3 and the like is attached to the spectacle frame 80.

In the figure, reference numerals 8 and 18 denote AC power supplies,
24 is a switch, 13 and 17 are variable resistors, and 25 is a liquid crystal. P is a pitch.

In this variable focus lens, the electrodes 22 and 23 are provided around the lenses 30H and 31H in the same manner as that shown in FIG. It is preferable that the electrodes 22 and 23 be transparent electrodes because the periphery of the field of view of the spectacles becomes bright.

In the above-described embodiment of the present invention, a variable focus lens is mainly used as an optical characteristic variable optical element. However, as the optical characteristic variable optical element, a diffractive optical element, a Fresnel lens, a prism, a lenticular lens Etc. may be used. The portions of each element that refract or reflect light may be replaced with a variable refractive index material, that is, various liquid crystals, ferroelectric materials, or materials having an electro-optic effect.

In addition to the electric field, a magnetic field, the frequency of the electric field, and the frequency of the magnetic field may be changed in order to change the molecular orientation of the liquid crystal.

The optical system using the optical characteristic variable optical element according to the present invention described above is a photographing device for forming an object image and receiving the image by an image pickup device such as a CCD or a silver halide film to perform photographing. It can be used for endoscopes. It can also be used as an observation device for observing an object image through an eyepiece, particularly as an objective optical system for a finder section of a camera. Below, the embodiment is illustrated.

FIGS. 25, 26, and 27 are conceptual diagrams of a fifth embodiment in which an imaging optical system including an optical characteristic variable optical element of the present invention is incorporated in an objective optical system of a finder section of an electronic camera. Show. 25 is a front perspective view showing the appearance of the electronic camera 80, FIG. 26 is a rear perspective view of the same, and FIG. 27 is a cross-sectional view showing the configuration of the electronic camera 80. In this embodiment, the electronic camera 80 includes a photographing optical system 81 having a photographing optical path 82 and a viewfinder optical path 8.
4 includes a viewfinder optical system 83, a release 85, a flash 86, a liquid crystal display monitor 87, and the like. When the release 85 disposed on the upper part of the camera 80 is pressed, the photographing is performed through the photographing objective optical system 88 in conjunction therewith. It is. The objective optical system for photographing includes a plurality of transmission-type optical characteristic variable optical elements (here, liquid crystal is used), and performs zooming and focusing. An object image formed by the photographing objective optical system 88 is formed on an imaging surface 90 of the CCD 89 via a filter 91 such as a low-pass filter or an infrared cut filter. This C
The object image received by the CD 89 passes through the processing means 92,
The image is displayed as an electronic image on a liquid crystal display monitor 87 provided on the back of the camera. Further, a memory or the like is arranged in the processing means 92, and a photographed electronic image can be recorded. This memory may be provided separately from the processing means 92, or may be configured to record and write electronically using a floppy disk or the like. Also CC
It may be configured as a silver halide camera in which a silver halide film is arranged in place of D89.

Further, in the finder optical path 84, an imaging optical system having a reflection type optical characteristic variable optical element is arranged as a finder objective optical system. Further, a cover lens 94 having a positive power is disposed as a cover member, and the angle of view is enlarged. The cover lens 94
And the front group GF of the finder objective optical system 93 by the prism VP1 on the object side of the stop S of the imaging optical system, and after the finder objective optical system 93 by the prism VP on the image side of the stop S of the imaging optical system. A group GR is formed. Zooming and focusing are performed by arranging optical characteristic variable optical elements in each of the front group GF and the rear group GR with the stop S interposed therebetween. Here, a reflection type optical characteristic variable optical element formed integrally with the reflection prism is used. Although the liquid crystal 66H is used here, zooming and focusing operations are performed by changing the optical characteristics as described above. This control is performed by the processing means in conjunction with the zooming and focusing actions of the photographing objective optical system. This viewfinder objective optical system 9
The object image formed by 3 is formed on the field frame 97 of the porofrism 95 which is an image erecting member. The field frame 97 separates between the first reflection surface 96 and the second reflection surface 98 of the Porro prism 95, and the field frame 97 is disposed therebetween. Behind the polyprism 95, an eyepiece optical system 99 that guides the erect image into the observer's eyeball E is disposed.

In the camera 80 configured as described above, the finder objective optical system 93 can be configured with a small number of optical members, high performance and miniaturization can be realized, and the optical path itself of the objective optical system 93 can be bent. This increases the degree of freedom of arrangement inside the camera, which is advantageous in design.

Next, FIG. 28 shows a conceptual diagram of a configuration in which the imaging optical system of the present invention is incorporated in an objective optical system 88 of a photographing section of an electronic camera 80. In the case of this example, the photographing objective optical system 88 arranged on the photographing optical path 82 is an image forming optical system using a reflection type optical characteristic variable optical element. The object image formed by the photographing objective optical system is converted to a C image via a filter 91 such as a low-pass filter or an infrared cut filter.
It is formed on the imaging surface 90 of the CD 89. This CCD 89
Is displayed as an electronic image on the liquid crystal display device (LCD) 100 via the processing means 92. The processing unit 92 also controls a recording unit 101 that records an object image captured by the CCD 89 as electronic information. The image displayed on the LCD 100 is the eyepiece optical system 9.
It is guided to the observer's eye E via 9. This eyepiece optical system 9
Reference numeral 9 denotes an eccentric prism provided with an optical characteristic variable optical element having the same form as that used in the imaging optical system of the present invention. The depth of the virtual image of the LCD can be adjusted according to the degree. In this example, the incident surface 102 and the reflecting surface 1
03 and a surface 104 that serves both reflection and refraction. In addition, the surface 10 having two reflecting actions
At least one of the surfaces 3, 104, desirably both surfaces, is composed of a plane-symmetric free-form surface having only one plane of symmetry for applying power to the light beam and correcting eccentric aberration. The only plane of symmetry is the objective optical system 8 for photographing.
Eccentric prisms arranged in groups GF, GR before and after 8, V
It is formed substantially on the same plane as the only plane of symmetry of the plane-symmetric free-form surface of P1 and VP2. Also here, a reflection type optical characteristic variable optical element using the liquid crystal 66H is used.

In the camera 80 constructed as described above, the photographing objective optical system 88 can be composed of a small number of optical members, and it can be made high-performance and compact, and the entire optical system can be arranged on the same plane. The thickness in the direction perpendicular to the plane can be reduced.

FIG. 29 is a conceptual diagram showing a configuration in which the optical characteristic variable optical element of the present invention is incorporated in an objective optical system 120 of an observation system of an electronic endoscope. Also in this example, the objective optical system 110 of the observation system uses an imaging optical system including a reflective optical characteristic variable optical element 128 for performing zooming focusing. A liquid crystal 66H is used for these reflective optical characteristic variable optical elements. This electronic endoscope is shown in FIG.
As shown in FIG. 9A, an electronic endoscope 111, a light source device 112 for supplying illumination light, a video processor 113 for performing signal processing corresponding to the electronic endoscope 111, and an output from the video processor 113 Monitor 114 for displaying a video signal to be reproduced, and a video processor 113
VTR deck 115 that is connected to
Further, the electronic endoscope 111 is configured with a video disk 116 and a video printer 117 that prints out a video signal as a video, and the distal end 119 of the insertion section 118 of the electronic endoscope 111 is configured as shown in FIG. ing.
The light beam illuminated from the light source device 112 passes through the light guide fiber bundle 126 and illuminates the observation site by the illumination objective optical system 127. Then, light from the observation site is transmitted through the cover member 124 to the observation objective optical system 1.
25 forms an object image. This object image is
It is formed on the imaging surface 123 of the CCD 122 via a filter 121 such as a low-pass foo 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
The video is displayed directly on the monitor 114 by the video processor 113 shown in FIG.
5. Recorded in the video disk 116 and printed out from the video printer 117 as video.

Although the endoscope thus configured has zooming and focusing functions, it can be configured with a small number of optical members, and high performance and downsizing can be realized.

The eccentric prisms provided in the front group and the rear group of the imaging optical system according to the embodiment using a plurality of the above prisms each have three optical surfaces, one of which is one. Used a prism of a type having two times of internal reflection constituted by a surface having both a total reflection function and a transmission function, but the eccentric prism used in the present invention is not limited to this.

Some examples of the varifocal prism VP that can be used in the present invention are shown in FIGS. Each of the prisms VP forms an image on the image plane 136. However, the prism VP forms an image on the pupil 131 side when a light beam from a subject enters from the image plane 136 by reversing the optical path.
Can also be used as Further, it may be configured as an imaging optical system or an observation optical system by itself. The surface on which the optical characteristic variable optical element is used may be determined depending on the use form.

In the case of FIG. 30, the prism VP is the first surface 1
32, a second surface 133, a third surface 134, and a fourth surface 135. Light incident through the entrance pupil 131 passes through the first surface 13.
2 and is incident on the prism VP, is internally reflected on the second surface 133, is incident on the third surface 134 and is internally reflected, is incident on the fourth surface 135 and is refracted, and forms an image on the image surface 136. I do.
The provision of the optical characteristic variable optical element on the third surface 134 and the second surface 133 enables zooming and focusing.

In the case of FIG. 31, the prism VP is the first surface 1
32, a second surface 133, a third surface 134, and a fourth surface 135. Light incident through the entrance pupil 131 passes through the first surface 13.
2 is incident on the prism VP, is internally reflected on the second surface 133, is incident on the third surface 134, is totally reflected, and is reflected on the fourth surface 1
At 35, the light is internally reflected, re-enters the third surface 134, is refracted at this time, and forms an image on the image surface 136. Here, an optical characteristic variable optical element is used for the second surface 133 and the fourth surface 135.

In the case of FIG. 32, the prism VP is
32, a second surface 133, a third surface 134, and a fourth surface 135. Light incident through the entrance pupil 131 passes through the first surface 13.
The light is refracted at 2 and is incident on the prism VP, is internally reflected on the second surface 133, is incident on the third surface 134 and is internally reflected, is incident again on the second surface 133 and is internally reflected, and is incident on the fourth surface 135. The incident light is refracted and forms an image on the image plane 136. Here the second
The optical characteristics variable optical element was used for the surface 133 and the third surface 134.

Further, the optical characteristic variable optical element of the present invention can be used for an image display device. As a sixth embodiment using this image display device, FIG. 33 shows a state in which a head-mounted image display device is mounted on the observer's head.
FIG. In this configuration, an eccentric prism optical system using the reflective optical characteristic variable optical element of the present invention for diopter adjustment is used as an eyepiece optical system 140 as shown in FIG. A pair of left and right pairs of display elements 141 are prepared and supported at a distance of the eye distance, so that a portable image display device 142 such as a stationary or head mounted image display device that can be observed with both eyes. Is configured as

That is, the display device main body 142 is provided with a pair of left and right eyepiece optical systems 140 as described above, and the image display element 1 comprising a liquid crystal display element on the image plane corresponding to them.
41 are arranged. As shown in FIG. 33, the display device main body 142 is provided with a temporal frame 143 as shown in FIG. 33, which can be held in front of the observer's eyes. .

Further, a speaker 144 is attached to the temporal frame 143 so that stereophonic sound can be heard together with image observation. As described above, the playback device 136 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, so that the viewer can attach the playback device 146 to the belt as shown in the figure. The video and audio can be enjoyed while being held at an arbitrary position such as a location. Reference numeral 147 in FIG. 33 denotes an adjustment unit for the switch, volume, and the like of the playback device 146. Note that electronic components such as a video processing and audio processing circuit are built in the display device main body 142.

The cord 145 may have a jack at the tip so that it can be attached to an existing video deck or the like. Furthermore, it is connected to a tuner for TV radio wave reception,
It may be used for viewing, or may be connected to a computer to receive computer graphics images, message images from the computer, and the like. Further, in order to reject an obstructive code, an antenna may be connected to receive an external signal by radio wave.

In the present invention, those described in the following items in addition to those described in the claims can also contribute to the object.

(1) An optical characteristic variable optical element characterized in that by applying an electric or magnetic field to a substance having an electro-optical effect or a magneto-optical effect, the refractive index of the substance is changed to change the optical characteristics.

(2) By applying an electric field, a magnetic field, or a temperature to a liquid crystal in which the orientation of liquid crystal molecules is substantially uniform in a plane substantially perpendicular to the incident optical axis, the refractive index of the liquid crystal is changed to change the optical characteristics. The optical characteristic variable optical element is characterized by changing.

(3) A variable focus lens using the optical characteristic variable optical element described in the item (1).

(4) Using a substance having an electro-optic effect and having a substantially uniform azimuth in a plane substantially perpendicular to the incident optical axis of the substance, and changing the refractive index of the substance to improve the optical characteristics. An optical characteristic variable optical element characterized by changing.

(5) The optical element according to (2), further comprising a member for regulating the orientation of the liquid crystal, wherein the member is processed by drawing exposure and etching or lithography. Optical characteristic variable optical element.

(6) A member for regulating the orientation of the substance having the electro-optical effect or the substance having the magneto-optical effect is provided, and the member is processed by drawing exposure and etching or lithography. Variable optical element.

(7) The optical element according to (5) or (6), wherein the member for regulating the azimuth satisfies the following condition (4). 0.5 nm <S <λ (4)

(8) An optical characteristic variable optical element, wherein the optical element is made of liquid crystal, and the liquid crystal has a negative refractive index anisotropy.

(9) An optical device comprising: a liquid crystal element; and a member for applying an electric field in a direction substantially perpendicular to the optical axis of the liquid crystal element, wherein the electric field by the member changes direction with time. Variable characteristic optical element.

(10) A liquid crystal element, a member for applying an electric field in a direction substantially parallel to the optical axis of the liquid crystal element, and a member for applying an electric field in a direction substantially perpendicular to the optical axis of the liquid crystal element. Characteristic optical element with variable optical characteristics.

(11) The above (7), (8) and (9)
Or, the optical element according to (10), wherein the following optical formula (7) is satisfied. T ≦ τ (7)

(12) The optical element according to the above (11), wherein the following conditional expression (7-1) is satisfied instead of the condition (7). T ≦ 10τ (7-1)

(13) The above (1), (7),
(8) The optical element according to (9), (10), (11) or (12), wherein the optical element is a liquid crystal having a helical alignment. .

(14) The optical element described in the above item (13), wherein the following formulas (6), (5-61) and (5-6) are used.
2) An optical element with variable optical characteristics, which satisfies any one of (5-28), (5-29) and (5-30). P <λ (6) P <20π · λ ≒ 62.8λ (5-61) P <20λ (5-62) | Γ / 2Φ | <1 (5-28) | Γ / 2Φ | <π / 6 ( 5-29) | Γ / 2Φ | <π (5-30)

(15) The above (1), (7),
(8) The optical element according to (9), (10), (11) or (12), wherein a polymer-dispersed liquid crystal element is used as the optical element. .

(16) The following formulas (8) and (8-1)
(9) An optical characteristic variable optical element using a polymer-dispersed liquid crystal, which satisfies at least one of formulas (9) and (9-1). D <λ / 5 (8) D <2λ (8-1) 0.5 <ff <0.999 (9) 0.1 <ff <0.5 (9-1)

(17) The optical element described in the above item (15), wherein at least one of the following expressions (8-1) and (9-1) is satisfied: Optical element. D <2λ (8-1) 0.1 <ff <0.5 (9-1)

(18) An optical element with a variable optical property that causes a phase transition between a liquid crystal phase and a liquid by a change in temperature and changes the refractive power.

(19) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14) The optical element according to the above (15), (16) or (17), wherein the orientation direction of the liquid crystal is controlled by applying a variable intensity magnetic field.

(20) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14) The optical element described in (15), (16) or (17), wherein the alignment direction of the liquid crystal is controlled by changing the intensity or frequency of the electric field, and the optical characteristic is variable. Optical element.

(21) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14) The optical element according to (15), (16) or (17), wherein a liquid crystal element whose dielectric anisotropy changes depending on the frequency of an electric field is used as the optical element. Variable characteristic optical element.

(22) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14), (15), (16), (17), (18),
(19) The optical element described in (20) or (21), wherein one of a substance having an electro-optical effect, a substance having a magneto-optical effect, a ferroelectric substance, and the like is used instead of the liquid crystal. The optical characteristic variable optical element characterized by the above.

(23) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14), (15), (16), (17), (18),
(19) An imaging device including the optical property variable optical element described in the item (20), (21) or (22).

(24) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14), (15), (16), (17), (18),
(19) Variable-focus glasses including the optical-characteristic-variable optical element according to the item (20), (21), or (22).

(25) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14), (15), (16), (17), (18),
(19) An optical apparatus comprising the optical property variable optical element described in the item (20), (21) or (22).

(26) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14), (15), (16), (17), (18),
(19) An imaging device using the optical element described in (20), (21) or (22), wherein an MTF characteristic of an electronic circuit or an image processing method is changed according to a change in the characteristic of the optical element. An imaging device characterized by performing the following.

(27) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14), (15), (16), (17), (18),
(19) An image pickup apparatus using the optical element described in (20), (21) or (22), wherein an MTF characteristic of an electronic circuit or an image is adjusted in accordance with a change in the characteristic of the optical element accompanying focus adjustment. An imaging apparatus characterized by changing a processing method.

(28) The above (1), (2),
(3), (4), (5), (6), (7), (8),
(9), (10), (11), (12), (13),
(14), (15), (16), (17), (18),
(19) An image pickup apparatus using the optical element described in (20), (21) or (22), wherein an MTF characteristic of an electronic circuit or image processing is performed in accordance with a change in the characteristic of the optical element due to zooming. An imaging device, wherein the method is changed.

[0211]

According to the present invention, when the optical characteristics of the optical characteristic variable optical element are changed, for example, aberration fluctuations caused when the focal length is changed can be easily changed by means such as changing the MTF characteristics of the electronic circuit. This makes it possible to always obtain a good image without blur, for example.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a refractive index ellipsoid of a liquid crystal having a negative refractive index anisotropy.

FIG. 3 is a diagram showing a state in which an electric field is applied in the first embodiment of the present invention.

FIG. 4 is a view showing an alignment state of liquid crystal molecules.

FIG. 5 is a view showing an alignment state of liquid crystal molecules.

FIG. 6 shows patterns formed on an alignment film.

FIG. 7 shows another pattern formed on the alignment film.

FIG. 8 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 10 is a diagram viewed from the z-axis direction in the embodiment of FIGS.

FIG. 11 is a modification of the second embodiment of the present invention.

FIG. 12 is a diagram illustrating an imaging apparatus using an optical element according to a second embodiment of the present invention.

13 is a view of the imaging device of FIG. 12 as viewed from the Z direction.

FIG. 14 is a diagram showing a configuration of a variable focus optical system using the optical characteristic variable optical element of the present invention.

FIG. 15 is a diagram showing an imaging apparatus provided with a zoom lens using the optical element of the present invention.

FIG. 16 is a diagram showing a liquid crystal element using a polymer instead of a liquid crystal.

FIG. 17 shows a liquid crystal element using a polymer instead of a liquid crystal.

FIG. 18 is a diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 19 is a diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 20 is a diagram showing an example in which the orientation is changed by a magnetic field in the optical element of the present invention.

FIG. 21 is a diagram showing a configuration of a variable focus mirror according to a fourth embodiment of the present invention.

FIG. 22 is a diagram showing another example of the fourth embodiment of the present invention.

FIG. 23 is a diagram showing another example of the fourth embodiment of the present invention.

FIG. 24 is a view showing a fifth embodiment which is variable-focus glasses using the optical element of the present invention;

FIG. 25 is a front perspective view of an electronic camera to which the present invention is applied in the sixth embodiment.

FIG. 26 is a rear perspective view of the sixth embodiment.

FIG. 27 is a sectional view of the sixth embodiment;

FIG. 28 is a modification of the sixth embodiment.

FIG. 29 shows an example in which the present invention is applied to an electronic endoscope in the seventh embodiment.

FIG. 30 shows an example of an eccentric prism applicable to the present invention.

FIG. 31 shows another example of the eccentric prism applicable to the present invention.

FIG. 32 shows another example of the eccentric prism applicable to the present invention.

FIG. 33 is an image display device to which the optical characteristic variable optical element according to the invention is applied.

FIG. 34 is a sectional view of the image display device of FIG. 33;

FIG. 35 is a diagram showing an electronic circuit for correcting an image obtained by the imaging device of the present invention.

FIG. 36 is a diagram showing a configuration of an optical system using a conventional liquid crystal lens.

FIG. 37 is a diagram showing a configuration of an optical system using another conventional liquid crystal lens.

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Claims (3)

[Claims] 1. An image pickup apparatus comprising an optical element having variable optical characteristics, wherein an MTF characteristic of an electronic circuit or an image processing method is changed according to a change in characteristics of the optical element. 2. An image pickup apparatus, wherein an MTF characteristic of an electronic circuit or an image processing method is changed in accordance with a change in characteristics of the optical element accompanying focus adjustment. 3. An image pickup apparatus, wherein an MTF characteristic of an electronic circuit or an image processing method is changed in accordance with a change in characteristics of the optical element due to zooming.