JPH07325269A - Optical device - Google Patents

Abstract

PURPOSE:To provide an optical device provided with an optical filter function which has the high function for removing the cause of the deterioration of image quality such as moire caused at the time of displaying an endoscopic image on a television monitor and can realize it at low cost. CONSTITUTION:Many surfaces such as parts (a), (b), (c) and (d) are provided by dividing both surfaces A and B into plural and making them inclined surfaces; two normals perpendicular to the parts (a) and (b) are in the relation of torsion so as to form an equal angle thetaa with an optical axis O, and the normals perpendicular to the other parts (c) and (d) are similarly in the relation of torsion; and the filter function for removing a spatial frequency component corresponding to twice as long as the distance of respective double images formed through two surfaces A and B is applied so as to remove the moire caused by the arrangement of a fiber bundle or photodetectors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device using an optical element having the function of an optical filter for removing moire and the like.

[0002]

2. Description of the Related Art In recent years, an endoscope such as a fiberscope having an elongated insertion portion has been widely used in the medical field and the industrial field. In addition, there is also one in which a television camera is attached to this fiberscope to display an endoscopic image on a monitor. When you attach a TV camera to the fiberscope and watch TV, moire fringes appear,
It was an obstacle to my observation.

Therefore, in Japanese Patent Laid-Open No. 61-186919, as shown in FIG. 35 (a), the crystal filter 1 is installed in the television camera 102 attached to the fiberscope 101.
No. 03 is placed to remove moire fringes.

In FIG. 35 (a), the fiberscope 101 has an objective lens 105 at the tip of an elongated insertion portion 104.
Is arranged, the tip surface of the image guide 106 formed of a fiber bundle is arranged at the image forming position of the objective lens 105, and the optical image formed on the tip surface is arranged in the vicinity of the operating section 107 or the eyepiece section 108. It is transmitted to the rear end face. The eyepiece lens 109 is disposed so as to face the rear end surface, and the transmitted optical image can be observed with the naked eye.

The eyepiece 108 includes a television camera 102.
Is attached, and an image is formed on a solid-state image sensor 112 having a two-dimensional array of light receiving elements via an imaging lens system 111 and a crystal filter 103 for removing moire. This solid-state image sensor 1
Reference numeral 12 is connected to a camera control unit (hereinafter abbreviated as CCU) 113. The CCU 113 performs signal processing on an image signal (image pickup signal) photoelectrically converted by the solid-state image pickup device 112 and converts it into a standard video signal. It is output to the television monitor 114, and the endoscopic image formed by the objective lens 105 is displayed on the display surface of the television monitor 114.

[0006]

However, there is a problem that the crystal filter 103 is expensive. Also,
A rigid endoscope 11 using a relay lens 116 as shown in FIG.
7 and the television camera 102 in combination, when water is present on the surface of the subject in the human body, pink and green or blue and orange bleeding occurs around the reflection image of the illumination light. There was a problem to do. This is also a kind of moire, but the crystal filter 103 has also been used to remove this phenomenon.

In FIG. 35 (b), the hard insertion part 11
The image from the objective lens 105 at the tip of 8 is transmitted to the rear eyepiece 108 side by the relay lens system 116, and the eyepiece 109 and the imaging lens system 11 in the television camera 102 are transmitted.
An image is formed on the solid-state imaging device 112 through the crystal filter 103 for removing the moiré pattern 1 and the crystal filter 103. The crystal filter 103 has been used to eliminate the above-mentioned bleeding, but it also has the drawback of being expensive.

The crystal filter 103 is also used for removing moire in an electronic scope provided with a solid-state image pickup device 112 such as a CCD at the tip thereof, or a television camera for consumer use, but it also has a disadvantage of high price.

As conventional examples for solving this problem, there are JP-A-3-248695 and JP-B-44-1155. In all of these, one surface of a transparent plate is composed of a plurality of inclined surfaces having different inclination angles, and a multiple image of an object is formed on an image surface by a refraction effect generated at each inclined surface. However, in Japanese Patent Publication No. 44-1155,
There were many unknown problems in actually using it in products.

Further, Japanese Patent Laid-Open No. 3-248695 discloses an optical filter having at least one set of inclined surfaces which are point-symmetrical around the optical axis. As described above, the optical filter under the condition of merely point symmetry has a problem that the function of removing moire and the like deteriorates in the defocused state.

The present invention has been made in view of the above points, and has an optical filter function capable of enhancing the function of removing moire and the like that occurs when an endoscopic image is displayed on a television monitor and realizing it at low cost. An object of the present invention is to provide an optical device having an optical element provided.

[0012]

In an optical device provided with an optical system for observation or imaging, both surfaces are divided into a plurality of polyhedral surfaces, and each of the normals standing on each polyhedral surface. At least two surfaces in each of the multiple surfaces are twisted with respect to the optical axis, and an optical system provided with an optical element having a filter function for removing a specific spatial frequency component in an image formed through at least two surfaces in each of the multiple surfaces is provided. With this structure, the filter function is provided not only in the focused state but also in the defocused state, so that the moire removal function can be enhanced at low cost.

[0013]

Embodiments of the present invention will be specifically described below with reference to the drawings. 1 to 15 relate to a first embodiment of the present invention, FIG. 1 shows a double-sided polyhedral lens 1 in the first embodiment of the present invention, and FIG. 2 is an improved single-sided polyhedral surface in a modification of the first embodiment. FIG. 3 shows a lens, FIG. 3 shows a configuration of an endoscope apparatus of a modified example of the first embodiment, FIG. 4 shows a pixel array of a solid-state image pickup device, FIG. 5 shows an image pickup optical system of a television camera, and FIG. Shows an explanatory view of the basic principle of removing moire by a double image using a single-sided polyhedral lens, FIG. 7 shows that it has a moire removing function even in a defocus state, and FIG. 8 shows color modulation by a trap line. The effect of removing the generation of moire due to is shown in the spatial frequency plane, FIG. 9 shows the array of images of the fiber bundle, FIG. 10 shows the disturbed portion near the boundary of the polyhedral lens, and FIG. The part is shown enlarged, etc., and FIG. Shows a state formed by eccentrically boundary surface lens, FIG. 13 shows that it has a plane grinding the vicinity of the center at the boundary of the polyhedral lens,
FIG. 14 shows that it is desirable to dispose the polyhedral lens near the pupil, and FIG. 15 shows the overall configuration of the endoscope apparatus of the first embodiment.

FIG. 1 shows a double-sided polyhedral lens 1 as an optical element having the function of an optical low-pass filter according to the first embodiment of the present invention. This double-sided polyhedral lens 1 is formed with a polyhedral lens having two split surfaces twisted like a propeller on both sides like one surface of the single-sided polyhedral lens 2 in the modification of the first embodiment shown in FIG. It was done. Therefore, first, a single-sided polyhedral lens 2 in a modified example having a simple structure will be described.

The single-sided polyhedral lens 2 as an optical element having the function of an optical low-pass filter in the modification of the first embodiment is one of those which are point-symmetrical about the optical axis disclosed in Japanese Patent Laid-Open No. 3-248695. Therefore, the optical filter function is high even in the defocused state.

On one surface (for example, B surface) of the single-sided polyhedral lens 2, there is a semicircular a portion which shares the optical axis O and is formed so that the two inclined surfaces are inclined in opposite directions. b
And the normals of these two slopes are in a twisted relationship and are inclined by θ with respect to each other.

Since it is formed so as to have a twist relationship, the function of a filter for removing moire and the like can be left even in a defocused state where the focus is deviated as described later (see FIG. 7). ).

If the inclinations of the normals to the respective surfaces with respect to the optical axis O are θ1 and θ2, then θ = θ1−θ2 (1) (θ1 and θ2 are shown together with their signs. θ1 =-| θ2 |).

The shape data of the B surface of the single-sided polyhedral lens 2 is such that the direction of the optical axis O is the Z axis, and the X axis and the Y axis are in the plane perpendicular to the Z axis, for example, the boundary line between the parts a and b. When the direction of l is set to the X-axis, it becomes as follows.

The portion a has a range in which Y is zero or positive (that is, Y
≧ 0), the surface of the part a has Z = P · X, the surface of the part b has Y in a negative range (that is, Y <0), and the surface of the part b has Z = −P · X. Here, the parameter P representing the inclined surface is, for example, P = tan 1′≈0.00029, where 1′≈0.00029 rad. In this case, the above θ is θ = 2 ′.
As shown in FIG. 2B, the size of the single-sided polyhedral lens 2 is φ8, the thickness To is, for example, To = 1 mm, and the refractive index n is, for example, n = 1.51633.

The right side of FIG. 2B is a plan view and the left side is a side view. Further, as shown in FIG. 2B, a mark M for discriminating the direction of this optical element is attached to the B surface. The other surface of this single-sided polyhedral lens 2, that is, the A surface, is a flat surface.

FIG. 3 shows an endoscope device 3 as an optical device of a modified example of the first embodiment using this single-sided polyhedral lens 2. The endoscope device 3 includes a rigid endoscope 5 having an illumination optical system and an observation optical system, a television camera 6 having an image pickup means mounted on the rigid endoscope 5, and a rigid endoscope. 5, a light source device 7 for supplying illumination light, a CCU 9 for performing signal processing on a solid-state image sensor 8 such as a CCD built in the television camera 6, and a color monitor 10 connected to the CCU 9 and displaying a video signal. Composed.

In the endoscope device 3, the light is generated due to the arrangement of the light receiving elements (including the case of a mosaic filter) which are two-dimensionally arranged in the solid-state image pickup element 8 as an optical member, and interfere with the arrangement period. It removes the moiré that occurs and the moiré caused by the interference with the color modulation.

The rigid endoscope 5 includes an insertion portion 11 formed of a rigid outer tube, a large-diameter grip portion 12 formed at the rear end of the insertion portion 11 and gripped, and a rear portion of the grip portion 12. It is composed of an eyepiece portion 13 formed at the end. This grip 13
Is provided with a light guide base 14, and is detachably connected to the light source device 7 via a light guide cable 15.

The white illumination light of the lamp 16 in the light source device 7 is transmitted by a light guide serving as an illumination light transmission means in the light guide cable 15, and the light guide cap 14 portion leads to the light guide 17 in the rigid endoscope 5. Supply illumination light to the side. Then, an illumination optical system that emits the illumination light transmitted from the front end surface attached to the illumination window at the front end of the insertion portion 11 to the front is formed.

An objective lens 18 is attached to an observation window formed adjacent to the illumination window at this tip portion, and forms an image of a subject illuminated by the objective lens 18. This image is relayed by a relay lens system 19 which is an image transmission optical system arranged in the insertion portion 11 along the optical axis of the objective lens 18 so as to coincide with the optical axis of the objective lens 18 to form an image on the rear side. The final image is transmitted by tying it to the eyepiece unit 13
Form in the vicinity.

This image is formed with an observation optical system which can be observed with the naked eye through an eyepiece lens (eyepiece optical system) 20. When the television camera 6 is attached to the eyepiece unit 13, the image transmitted by the relay lens system 19 is an eyepiece lens 20 and a single-sided polyhedral lens 2 having the function of an optical low-pass filter arranged in the television camera 6. A solid-state image pickup device 8 having a color separation filter such as a mosaic filter is used to form an image through an imaging lens (imaging lens) 21 so that an image can be picked up.

It is desirable that this single-sided polyhedral lens 2 be arranged near the position of the pupil of the imaging lens 21. In addition,
The focal length of the imaging lens 21 is about 15 to 35 mm, but about 15 to 25 mm is suitable when combined with the television camera 6 using a 1/3 to 1/4 inch CCD.

The image pickup signal photoelectrically converted by the solid-state image pickup device 8 is converted into a standard video signal by the CCU 9.
The image is displayed on the color monitor 10. For example, as shown in FIG. 4, the solid-state imaging device 8 has a configuration in which pixels (picture elements), which are light receiving elements having a photoelectric conversion function, are regularly arranged in a two-dimensional matrix on a photoelectric conversion surface.

In FIG. 4, R, G, and B indicate that R (red), G (green), and B (blue) mosaic filters are arranged in front of the pixel. , R,
Color imaging is performed by photoelectrically converting the light separated into G and B colors. Here, Px ... Horizontal size of one pixel of the solid-state image sensor 8, Py ... Vertical size of one pixel of the solid-state image sensor 8, Wy ... Vertical size of effective image pickup area of the solid-state image sensor 8, Wx The horizontal size of the effective image pickup area of the solid-state image sensor 8, M ... The horizontal cycle of the mosaic filter of the solid-state image sensor 8 is expressed in pixel units. In the example of FIG. 4, M = 2, N ... The vertical cycle of the mosaic filter of the solid-state image sensor 8 is expressed in pixel units. In the example of FIG. 4, N = 2, and in the solid-state image sensor 8 without the mosaic filter, M =
Treat as N = 1.

FIG. 5A shows the arrangement direction of the single-sided polyhedral lens 2, with the boundary line (division line) between the parts a and b being horizontal, that is, parallel to the horizontal direction (horizontal direction) of the solid-state image sensor 8. Indicates that it is placed. In this case, the image is separated in the horizontal scanning direction of the solid-state image sensor 8.

That is, FIG. 5B shows a double image formed through this single-sided polyhedral lens 2 and has a distance d in the horizontal direction.
Formed apart. In the present specification, the solid-state image sensor 8
The horizontal direction (horizontal direction) is the X axis, and the vertical direction (vertical direction) is Y.
Assume that it is set on the axis.

FIG. 6 shows an image pickup optical system including this single-sided polyhedral lens 2.
An explanatory view of a function of erasing a striped pattern by forming a double image by using is shown. The basic idea of moiré removal is that when sampling an object image, moiré occurs when the sampling frequency and the frequency component contained in the object image are close, so an optical low-pass filter should remove this frequency component. Set to a proper frequency characteristic.

As shown in FIG. 6, when a bright and dark object is imaged by the single-sided polyhedral lens 2 and the imaging lens 21 (on the imaging surface of the solid-state imaging device 8) in a repeated cycle, it is imaged through the portion a. When the first image and the second image formed through the portion b are formed, and the separation distance between the first image and the second image is set to 1/2 of the period, the intensity distributions of the two images overlap. Then, since one mountain fills the other valley, the intensity becomes uniform and the existence of the striped pattern cannot be seen.

That is, when a double image is formed, there is no frequency component having a repetition period twice the image separation distance.
Therefore, by appropriately setting the relationship between the interval (repetition cycle) of picture elements (pixels) for sampling and the image separation distance, moire can be removed.

FIG. 7 is a diagram for explaining the difference in action between the one satisfying the twist relation adopted in this embodiment and the like and the one not satisfying the twist relation and simply the point symmetry. Figure 7 (a)
2 shows the optical element of FIG. 2, that is, the optical system portion in which the single-sided polyhedral lens 2 in which the arrangement of the inclined surfaces satisfies the twist relation is arranged. FIG. 7B shows an optical system in which a prism-shaped member (the element shown in FIG. 1 of Japanese Patent Laid-Open No. 3-248695) having one surface flat and the other surface mountain-shaped is arranged together with a lens.

By arranging these elements in the optical path, the imaging optical system forms a double image of the object on the image plane. The same effect can be obtained by using either element on the image plane in the focused state (each becomes a double image), but the function is different in the defocused state. To see the defocused state, it suffices to see the imaged state at a position off the image plane.

In the configuration of FIG. 7B, the light beam refracted by the inclined surface of the prism forms an image on the opposite side of the optical axis (for example, in FIG. 7B, the light above the optical axis is formed). Forms an image on the lower side of the optical axis on the image plane), and since the light beams from the upper side and the lower side of the optical axis intersect, it is possible that light gathers in a relatively narrow area near the optical axis. Exists.

Therefore, image separation may not be performed (or may be insufficient) due to defocus, and the function as a low-pass filter may be lost (or insufficient).

That is, in FIG. 7 (b), a double image is formed at the defocus position which is deviated to the rear from the focus position, but is not separated at the defocus position which is deviated to the front side, and the function as a low-pass filter is obtained. It disappears (or becomes insufficient). In other words, the shape of the point image changes due to defocusing, which changes the MTF.

On the other hand, in FIG. 7A, since the inclined surface has a twisted relationship, the separation of the light flux forming two images is maintained even in a considerably defocused state, and the function of the low-pass filter is thus improved. It is not lost. That is, in FIG. 7A, a double image is formed at the defocus position that is displaced rearward from the focus position, and a double image is also formed at the defocus position that is displaced forward, and the separation distance (2
Since the distance (double image distance) hardly changes, the function as a low-pass filter is maintained even for a defocused image.

Therefore, it is possible to prevent moire from occurring not only in the focused portion of the formed image but also in the portion formed by defocusing. In other words, even with defocus,
The point image remains in the two shapes, and the MTF is the double image with the defocus effect.

When the multifaceted lens 2 having an inclined surface (slope) as shown in FIG. 2 is manufactured, it can be manufactured by forming a metal mold and molding by plastic or glass. Alternatively, it may be manufactured by non-uniformly coating a flat substrate.

In such a case, the surface shape of the boundary portion of the two slopes of the single-sided polyhedral lens 2 (the portion surrounded by the alternate long and short dash line in FIG. 7, which will be described later) does not become the shape as designed, and becomes disordered. . The low-pass filter function deteriorates in this disturbed portion, and flare occurs due to light passing through this disturbed portion. As will be described later, in order to prevent this, for example, a substance that does not transmit light is attached to the disturbed portion to take measures such as a light-shielding portion.

As shown in FIG. 3, the multifaceted lens 2 is mounted on the rigid endoscope 5 for a television camera 6 (or a consumer V.
When used for a TR camera, a general TV camera, etc.), it is desirable that at least one of conditional expressions (2) to (21) described below is satisfied. In the modified example of the first embodiment, these conditional expressions are set so as to satisfy these conditional expressions, and even in the defocused state, even when the moire or the like occurs due to the sampling cycle or the like, the moire or the like can be effectively removed. . In this case, since it is expressed by a conditional expression,
The magnification β r, the distance d between double images, etc. are defined as follows.

Βr: magnification of the lens between the polyhedral lens 2 and the image plane (here, the solid-state image pickup device 8), Sf: distance from the polyhedral lens 2 of an image formed by a lens in front of the polyhedral lens 2 (Fig. Middle, right is positive.), D ... Distance of double image formed by the polyhedral lens 2 (see FIG. 5B), n ... Refractive index of the polyhedral lens 2, and distance Sf is polyhedral in FIG. If there is another lens (such as the eyepiece lens 20 of the endoscope 5) in front of the lens 2 but nothing is present in front of the polyhedral lens 2 (directly photographing an object), S
f is the distance to the object.

First, when removing moire due to horizontal sampling of the mosaic filter, 1 / | 2 (n−1) θSfβr | = 1 / (PxM) (2) The denominator on the left side of this equation (2) is twice the separation distance of the double image on the image plane, the denominator on the right side is the distance of the sampling period, and moire is removed by setting these distances equal. .

In practice, some moire may be left, so the condition of equation (2) is relaxed and 0.75 / (PxM) ≦ 1 / | 2 (n−1) θSfβr | ≦ 1.5 / (PxM ) (3) is sufficient.

The lower limit of the equation (3) corresponds to the frequency at which the value of MTF becomes about 40%. If the separation distance of the image becomes larger than this, the MTF on the low frequency side becomes smaller and the contrast of the image lowers. It becomes a problem. The upper limit is about 7 MTF
This corresponds to a frequency of 0%, and if the separation distance becomes smaller than this, the function of removing moire deteriorates.

When removing moire due to luminance sampling, it is sufficient to set M = N = 1 in equations (2) and (3).

In the case of an NTSC television camera, an electronic scope, etc., moire occurs due to the modulation of color signals. If it is necessary to remove moire at that time, the frequency of the color subcarrier is 3.58MHz, so 0.75 ・ 40 ・ 3.58 / Wy ≦ 1 / | 2 (n−1) θSfβr ｜ ≦ 1.5 ・ 40 ・ 3.58 / Wy (4) That is, 107.4 / Wy ≦ 1 / | 2 (n−1) θSfβr | ≦ 214.8 / Wy (5). Here, it is used that 1 MHz corresponds to 80 TV lines.

If the single-sided polyhedral lens 2 is placed as shown in FIG. 5A, the trap line (line with MTF = 0) will be as shown by the dotted line in FIG. 8, but moire due to color modulation will be indicated by the circles in FIG. The trap line should pass through this point, and if the dividing direction of the polyhedral lens 2 is inclined with respect to the horizontal direction by ω + 90 °, then the trap line enters as shown by the solid line in FIG. Therefore, when the definition of φ is φ = arc tan 1.64 / 3.58, that is, 1.64 / 3.58 ＝ tan φ (6), cos (90 ° −ω−φ) ・ 0.75 ・ 40 ・ A / Wy ≦ 1 / | 2 ( n−1) θSfβr ｜ ≦ cos (90 ° −ω−φ) ・ 1.5 ・ 40 ・ A (7) where A ＝ √ (1.64 ・ 1.64 + 3.58 ・ 3.58) (where,
√ () represents the square root in ())
They are 1.64, 1.64 + 3.58, 3.58. The angle is positive when measured clockwise from the coordinate axis.

Rewriting the equation (7), sin (ω + φ) 118.136 / Wy ≦ 1 / | 2 (n-1) θSfβr | ≦ sin (ω + φ) 236.27 / Wy (8) Just fill. That is, by setting the division direction (direction of the boundary line 1) or the like so as to satisfy the condition of Expression (7) or (8), moire due to color modulation can be removed. In FIG. 8, Ux and Uy represent spatial frequencies in the X and Y directions on the image plane (in this case, the photoelectric conversion plane of the solid-state image sensor 8).

The trap line will be supplementarily described. Similar to an electric circuit, in an optical system, the relationship between spatial frequency [the number of repetitions of light and dark of an object (image) per 1 mm] and intensity is called frequency characteristic. A graph showing frequency characteristics is referred to as MTF (modulation transfer func).
tion).

In the case of a lens, unlike an electric signal, an object (image) corresponding to the signal is two-dimensional, so that the frequency plane is considered. FIG. 8 shows the frequency plane, and the coordinate axis indicating the magnitude of the frequency response is in the direction perpendicular to the paper surface (therefore, in FIG. 8, the magnitude of the frequency response at each frequency is unknown). The trap line is a line connecting points where MTF = 0, that is, the frequency response becomes zero.

In the case of a PAL TV camera or the like, 3.58 MHz in equations (4) and (7) may be replaced with 4.43 MHz.

High-definition television (abbreviated as HD-TV)
In the case of image pickup devices such as TV cameras and electronic scopes, the number of effective samples per line (scan line) is 19
Since it is defined as 20, (TV technical journal, January 1991, P20) 0.75 ・ (1920 / Wx) ≦ 1 / | 2 (n−1) θSfβr ｜ ≦ 1.5 ・ (1920 / Wx) (9) If so, the moiré of the luminance digital sampling can be removed. To remove moire in color signal sampling, the number of color digital samples is set to 960 (same magazine) 0.75 ・ (960 / Wx) ≦ 1 / | 2 (n−1) θSfβr | ≦ 1.5 ・ (960 / Wx) (10) is enough.

The number of horizontal pixels npx of the solid-state image sensor 8 is 192
If 0 is insufficient, then npx / 1920 (11) should be applied to the left and right terms of equations (9) and (10) (in this specification, equation (11)).
In that case, it simply means an inequality obtained by multiplying the equation (9) or (10) by npx / 1920).

A fiberscope in which fiber bundles are arranged in a two-dimensional array of the polyhedral lenses 2 and an image guide as an optical member for transmitting pixels in each fiber is used as an image transmitting means, and an electronic image pickup system such as a TV camera is provided. In order to use for the moire removal in the case of combining the above, the fiber spacing in the fiber bundle image by the bale-stacked array (distances between adjacent fibers are equal) is used as shown in FIG.
If it is Pf (in this case, the image may be a real image on the solid-state image sensor 8) 0.75 / (Pf · sin 60 °) ≦ 1 / | 2 (n−1) θSfβr | ≦ 1.5 / (Pf・ Sin 60 °) (12)

When combining several fiberscopes and an electronic imaging system, Pf of one of the fiberscopes
Alternatively, the average value of Pf of each fiberscope may satisfy the expression (12). This is the formula (2
It can be applied to Pf of 2), (23) and (24).

If Uo = 1 / | 2 (n−1) θSfβr | (13), the MTF is given by MTF = cos (U / Uo · π / 2) (14), so that the equation (12) is equal to When the number becomes 0, the MTF at the frequency 1 / (Pf · sin 60 °) is 0.
Therefore, the moire can be reduced to half or less.

When the multifaceted lens 2 as shown in FIG. 2 is manufactured, it is often the case that a metal mold is made and plastic molding or glass molding is performed. Alternatively, it may be manufactured by non-uniformly coating a flat substrate.

In such a case, the surface shape of the boundary portion (the portion surrounded by the alternate long and short dash line in FIG. 10A) of the two slopes of the polyhedral lens 2 does not become the shape as designed and becomes disordered. .
If the area occupied by the marginal ray in this polyhedral lens 2 is Sm (the portion surrounded by the dotted line in FIG. 10A),
Area Sα occupied by the disordered portion (Fig. 10 with inclination)
The portion (a)) is preferably Sα / Sm <0.3 (15).

If it exceeds this, flare occurs in the image, which is not practically good. Further, in a high-quality endoscope using a relay lens or an image fiber having a large number of fibers, if Sα / Sm <0.12 (16), an image with better contrast can be obtained.
The above is experimentally confirmed using the single-sided polyhedral lens 2 of FIG. At this time, the maximum deviation of the surface shape of the defective portion Sα was 10 μm or less.

FIG. 11A shows a detailed view of a portion where the surface shape is disturbed. Further, FIG. 11B shows a detailed view of a portion where the surface shape is disturbed when the surfaces are misaligned.

FIG. 11A shows a situation such as the cross section along line A in FIG. 11C and the cross section along line B in FIG. 11B. That is, FIG. 11 (a)
Indicates a portion where the two inclined surfaces have the same height, and FIG. 11B shows a portion where the heights are different.

Originally, the cross section along the line A should be a straight line, but as shown in FIG. 11A, a dent is formed in the middle. The cross section along the line B should be square, but the corner is deformed as shown in FIG. 11 (b). First 1
The portion in which the surface shape is disordered in the case of 1 (a) is defined as follows.

The amount of deviation Hα from the surface obtained by smoothly extending the portion away from the boundary is Hα> λ (17) as the average value of the wavelength using λ, or the deviation on the surface Of the tangent plane at the point,
A portion having an angle α with the surface obtained by smoothly extending the above is α> 1 ° (18) is called a portion in which the surface shape is disturbed.

When there is a deviation between the surfaces as shown in FIG. 11B, Hα is defined by the deviation from the smooth extension of each surface (dotted line in the figure). The same applies to α. It is desirable that the deviation between the two surfaces (G in FIG. 11B) satisfies G <10 μ (19). If G exceeds this value, a bright line appears around the object when a bright point-like object is seen, which is not preferable.

In the optical element used in the present invention, the difference between the heights of the two inclined surfaces becomes larger as the size of the effective diameter becomes larger. However, when it is used for an endoscope, the size of the pupil is at most. Since it is about 7 mmφ, the size of the low-pass filter is about this. In that case, it is preferable to satisfy the condition of Expression (19).

In order to prevent flare due to the passage of light through a portion where the surface shape is disturbed, a substance that does not pass light may be attached to the portion of Sα in FIG. As such a substance, a CrO2 --Cr--CrO2 coat, a black paint or the like can be considered. This light-shielding portion is a polyhedral lens 2
It may be provided on the surface opposite to the above, at a position substantially covering Sα,
FIG. 10B shows an example in which the light shielding portion 23 is provided by coating.

Similarly, in order to avoid the disorder of the surface shape, FIG.
As shown in, the boundary line portion may be decentered with respect to the marginal light flux. In this way, when the marginal light flux is thick, the portion Sα with a disordered surface shape becomes smaller than Sm (A in FIG. 12), and when Sm is small (B in FIG. 12), there is no problem. Since the line 1 goes out of the light flux, the moire removing function is lost, but the image contrast can be maintained.

The eccentricity e of the boundary line preferably satisfies e / Da≤0.25 (20). If it exceeds this, the moire removing function will be deteriorated even in the state of FIG.

Alternatively, as shown in FIG. 13, the surface may be divided into three surface portions (that is, a portion, b portion, and e portion near the center) so that the boundary of the surface does not come to the central portion of the polyhedral lens 2. . This may be done by grinding only the central portion after grinding both surfaces when forming the mold of the multi-faced lens 2 to form the e portion in which the surface disorder is removed. At this time, the boundary of division of the three surface portions does not necessarily have to be clear.

Alternatively, the mold portion corresponding to the area Sα in FIG. 10A may be smoothed by repolishing or grinding to remove the mold portion having a shape higher than the design value. Figure 1
The examples of 0, 12, and 13 are particularly effective when combined with a television camera, an electronic scope, an adapter, a rigid endoscope, a fiberscope, or the like whose pupil diameter changes.

It has already been described that the vicinity of the pupil is good when the polyhedral lens 2 is placed in the optical system, but a more detailed consideration will be made.

In FIG. 14, hm and hc are the height of the marginal ray and the principal ray of the off-axis ray on the polyhedral lens surface of the polyhedral lens 2, respectively. Here, it is desirable to satisfy | hc / hm | <0.8 (21). This is because if hc becomes larger than the expression (21), the ratio of the areas where the off-axis light flux passes through the two surfaces of the polyhedral lens 2 largely differs, and the moire removing function decreases. Even when the expression (21) is not satisfied, if the polyhedral lens 2 is moved and set to a position near the pupil, the expression (21) can be satisfied, and it is desirable to set the position near the pupil position.

The polyhedral lens 2 does not have to be orthogonal to the optical axis O, and may be arranged to be tilted up to about 10 degrees to remove ghost. According to the modified example of the first embodiment described above, the pixel array of the solid-state image sensor 8 is set by setting so as to satisfy the conditional expression for moire removal,
The single-sided polyhedral lens 2 having an optical low-pass filter function having an inclined surface having a twisting relationship is adopted even when moiré is generated due to a sampling cycle or the like. Moire can be sufficiently removed not only from the image formed on the image pickup surface of No. 8 but also from the image formed by defocusing.
A larger moiré removing function is larger than that of the point-symmetrical optical filter disclosed in Japanese Patent No. 48695).

Therefore, the endoscopic image displayed on the color monitor 37 has a good image quality with moire removed.
Moreover, it can be realized at a much lower cost than when a crystal filter is used.

Next, the double-sided polyhedral lens 1 capable of having a larger filter function than the single-sided polyhedral lens 2 and the endoscope apparatus of the first embodiment using the double-sided polyhedral lens 1 will be described.

FIG. 1 shows a double-sided polyhedral lens 1 used in the first embodiment of the present invention. Like the B-side surface of the single-sided polyhedral lens 2, it has two split surfaces twisted like a propeller on both sides.
That is, as shown in FIG. 1A, this double-sided polyhedral lens 1
Like the single-sided polyhedral lens 2 on the surface A of the two inclined surfaces a
The portion and the portion b share almost the optical axis O, and are formed in a semicircular shape on both sides of a boundary line la that passes so as to be orthogonal to the optical axis O.

Further, as shown in FIG. 1B, on the other B surface, as in the single-sided polyhedral lens 2, the c and d parts of the two inclined surfaces share almost the optical axis O and are orthogonal to it. It is formed in a semicircular shape on both sides of the boundary line lb passing through. Further, as shown on the right side of FIG. 1C, the boundary line la on the A surface side and the boundary line lb on the B surface side are formed so as to be substantially orthogonal to each other.

The normals of the two slopes on the A-plane, which are erected almost at the centers, are in a twisted relationship and are inclined to each other by an angle θa. Also in the B-plane, the normals standing at the centers of the two slopes are in a torsional relationship, and are inclined with respect to each other by the angle θb.

By forming the image in a twisted relationship, the function of the low-pass filter can be sufficiently left even in the case of an image in a defocused state where the focus is deviated as described above. In FIG. 1, these angles θa and θb
Is set to, for example, θa = θb = 2′40 ″.

The shape data of the surface A of the double-sided polyhedral lens 1 is such that the direction of the optical axis O is the Z axis, and the X axis and the Y axis are in the plane perpendicular to the Z axis, for example, the boundary direction between the parts a and b. When is set on the X-axis, the result is as follows.

In the part a, Y is in the range of zero or positive (that is, Y
≧ 0), the surface of the part a has Z = P · X, the surface of the part b has Y in a negative range (that is, Y <0), and the surface of the part b has Z = −P · X. Here, the parameter P representing the inclined surface is, for example, P = tan 1′20 ″ ≈0.0004. The size of this double-sided polyhedral lens 1 is shown in FIG.
As shown in (c), the diameter is φ8, the thickness To is, for example, To = 1 mm, and the refractive index n is, for example, n =
It is 1.51633.

The right side of FIG. 1C is a plan view and the left side is a side view. Further, as shown in FIG. 1C, a mark M for discriminating the orientation of this optical element is provided on the A surface.

The angles θa and θb of the double-sided polyhedral lens 1 do not have to be equal, and the range of Pf values of some fiberscopes to be combined, Px and Py of the solid-state image sensor 8,
It may be selected appropriately according to N, M, etc.

At this time, the equation (2), the equation (3), the equation (5), the equation (7), the equation (8), the equation (9), and the equation (10) in which the angle θ is replaced by the angle θa or the angle θb are used. It is desirable to set at least two of the expressions (11) so that the angle θa or θb is satisfied. The effect is similar to that of the modified example of FIG. 2, and since different filter functions can be provided on both sides, it is possible to eliminate more causes of image quality deterioration during observation and the like. The effect is large compared to. Further, as in the case of the modified example, it can be made much cheaper than a crystal filter having an equivalent effect.

The A and B surfaces of the double-sided polyhedral lens 1 are expressed by the formula (1
5), formula (16), formula (19), formula (20), formula (2)
It is desirable to set such that at least one of 1) is satisfied. The effect is the same as that of the single-sided polyhedral lens 2 of FIG.

The MTF of the double-sided polyhedral lens 1 is given by the product of the MTFs of the respective one surfaces. Therefore, in this double-sided polyhedral lens 1, the number of trap lines can be increased, and the low-pass filter function can be further increased. This is particularly effective when combining a fiberscope with a strong moire and a television camera, and FIG. 15 shows a first embodiment of an optical device (more specifically, an imaging device having an imaging function) having such a configuration. The endoscope apparatus 31 is shown.

This endoscope device 31 is a fiberscope 32 which is a flexible endoscope including an illumination optical system and an observation optical system.
And it is detachably attached to this fiberscope 32,
An image pickup lens adapter 33 having an image pickup lens built therein, a television camera 34 detachably attached to the image pickup lens adapter 33 and having an image pickup means built therein, and a fiberscope 3.
Light source device 35 for supplying illumination light to the second illumination light transmission means
And a CCU 36 that performs signal processing for the solid-state image sensor 8 such as a CCD built in the television camera 34, and the CC
Color monitor 3 connected to U36 and displaying video signals
7 and 7.

The fiberscope 32 has flexibility and is provided with a soft and elongated insertion portion 41 to be inserted into a body cavity and the like, and a bending operation means (not shown) formed at the rear end of the insertion portion 41. The operation portion 42 has a wide width and an eyepiece portion 43 formed at the rear end of the operation portion 42. The light guide cable 45 extends from the operation portion 43 and is detachable from the light source device 35. Connected.

The white illumination light of the lamp 46 in the light source device 35 supplies the illumination light to the light guide 47 in the light guide cable 45. An illumination optical system that illuminates an object such as a diseased part by emitting the illumination light transmitted from the distal end surface attached to the illumination window at the distal end of the insertion portion 41 to the front is formed.

An objective lens 48 is attached to an observation window formed adjacent to the illumination window at this tip portion, and an image of a subject illuminated by the objective lens 48 is formed. At the image forming position, the front end surface of an image guide 49 having an image transmitting function formed of a fiber bundle is arranged, and the image guide 49 inserted through the insertion portion 41 causes the rear end surface to move to the rear side. Transmit the image. The image transmitted to this rear end face is formed with an observation optical system that can be observed with the naked eye through an eyepiece lens 50 provided in an eyepiece window of the eyepiece unit 43.

The imaging lens adapter 33 is attached to the eyepiece 43.
When the television camera 34 is mounted through the image guide 49, the image transmitted by the image guide 49 as an image transmission optical system is an eyepiece lens 50, an iris 52 in the imaging lens adapter 33, a second double-sided polyhedral lens 51, Imaging lens 5
3. An image pickup means (or an image pickup device) for forming an image is formed on the solid-state image pickup device 8 having a color separation filter such as a mosaic filter via the first double-sided polyhedral lens 1 arranged in the television camera 34. . The image pickup signal photoelectrically converted by the solid-state image pickup device 8 is converted into a standard image signal by the CCU 36, and a color image is displayed on the color monitor 37 serving as a color display means.

The CCU 36 integrates the luminance signal for one frame period to generate a dimming signal for dimming, which is an average value of brightness, and changes the opening / closing amount of the iris 52 in the imaging lens adapter 33. Output to the device 54. Then, when the average level of the luminance signal is high, the iris 52 is narrowed, and when the average level of the luminance signal is low, the iris 52 is controlled to open, that is, by forming an automatic iris control mechanism, the internal display displayed on the color monitor 37 is performed. The brightness of the mirror image is automatically controlled so that it is suitable for constant observation.

In the first double-sided polyhedral lens 1 of the first embodiment, the A-side and B-sided polyhedral lens surfaces are expressed by the equations (2) (or (3)) and (4) (or (5), or Are set so as to satisfy (7) or (8)) so that the moire due to the mosaic filter and the moire due to the modulation of the color signal are removed.

Further, the second double-sided polyhedral lens 51 is set so that each of the A-plane and B-plane polyhedral lens surfaces satisfies the expression (12), and as shown in FIG. 9, the fiber spacing Pf of the image of the fiber bundle is shown. Is set so as to remove the moire caused by the two-dimensional direction.

The second double-sided polyhedral lens 51 is set as shown in FIG. 20, which will be described later, and trap lines are set as shown in FIG. 21 to erase the clad portion in the fiberscope image in which the clad portion of each fiber is conspicuous black. It may be set as follows. Further, the single-sided polyhedral lens 2 may be used in place of the second double-sided polyhedral lens 51, and may be set so as to satisfy the expression (12).

According to the endoscope apparatus 31 of the first embodiment, similar to the modification using the single-sided polyhedral lens 2, not only the image in the focused state but also the image in the defocused state is sufficient. Since it has a function of removing moire and the like, it is possible to obtain a high-quality image without moire and the like even when observing an affected area or the like.

Further, in this embodiment, since the polyhedral lenses are formed on both sides, the cause of the deterioration of the image quality can be eliminated more than in the case of the modified example using the one-sided polyhedral lens 2, so that a high quality image can be obtained. Is obtained. Further, it is possible to obtain the same effect at a much lower cost than in the case where a crystal filter is used.

In the first embodiment shown in FIG. 15, the image pickup lens adapter 33 is exchanged, and instead of the double-sided polyhedral lens 51, an image pickup lens adapter 56 provided with a cover glass 55 is attached, and a relay lens with less moire is generated. It may be combined with the rigid endoscope 5 using the system.

By doing so, the imaging lens adapter 3
The endoscope device 60 having the optimum low-pass filter function can be realized only by replacing 3 with the imaging lens adapter 56. FIG. 16 is a configuration diagram (a light source device is omitted) of an endoscope system 61 of a second embodiment of an optical device of the present invention capable of realizing such endoscope devices 31 and 60.

In FIG. 16, what is shown by a solid line is an endoscope device 60. In this endoscope device 60, the rigid endoscope 5 is used instead of the fiberscope 32 in FIG. The configuration is such that the lens adapter 33 is replaced with an image pickup lens adapter 56, and a television camera 34 commonly used is detachably attached to the image pickup lens adapter 56.

Also in this endoscope apparatus 60, it is possible to remove the moire due to the mosaic filter and the moire due to the modulation of the color signal, and a high quality image can be obtained. In addition,
The rigid endoscope 5 has basically the same configuration as that shown in FIG. 3, for example.

FIG. 17 shows a fiberscope 70 of the third embodiment of the optical device of the present invention. This fiberscope 7
At 0, a double-sided polyhedral lens 71 is provided near the pupil of the eyepiece lens 50. Θa and θb of the double-sided polyhedral lens 71 are 0.75 / Pf ≦ 1 / | 2 (n−1) θaSfβr | ≦ 1.5 / Pf (22) 0.75 / Pf ≦ 1 / | 2 (n−1) θbSfβr | ≦ 1.5 / By setting Pf (23) and the angle ψ formed by the boundary lines la and lb to satisfy 45 ° ≦ ψ ≦ 75 ° (24), all fundamental spatial frequencies of the array of fiber bundles can be eliminated. I am trying. Here, βr is the magnification of the eyepiece lens 50 between the polygonal lens 71 and the position of the image plane, and Sf is the distance from the polygonal lens 71 to the image formed by the eyepiece lens 50 in front of the polygonal lens 71.

That is, as shown in FIGS. 18 (a) and 18 (b), the two-sided polyhedral surfaces are arranged so as to be parallel to the arrangement of the fiber bundles (that is, the arrangement direction J in the horizontal direction and the arrangement direction K in the obliquely upward direction). The directions of the boundary lines la and lb of the lens 71 are set (the boundary line la is parallel to the direction J, and the boundary line lb is parallel to the direction K). Therefore, the angle Ψ formed by the arrangement direction J of the fiber bundle in the horizontal direction and the arrangement direction K in the obliquely upward direction is
And the angles ψ formed by the boundary lines la and lb are equal (ψ = Ψ).

FIG. 19 shows the spatial frequency spectrum (circles) of the image of the fiber bundle and the trap line (dotted line) formed by the double-sided polyhedral lens 71 at this time. In the case of an image fiber having a random array, Pf may be an average value. Alternatively, in FIG. 17, the structure of the first modified example may be adopted in which the double-sided polyhedral lens 71 shown in FIG.

That is, with respect to the arrangement of the fiber bundles shown in FIG. 20B, the boundary lines la and lb as shown in FIG.
The double-sided polyhedral lens 1 shown in FIG.
You may arrange so that a may become parallel to J. At this time, one of the angles θa and θb may satisfy the formula (22) or (23), and the other one of the angles θa and θb may be expressed by the formula (12).
It is preferable to satisfy the equation in which θ of is replaced by θa or θb.

FIG. 21 shows the spatial frequency spectrum (circles) of the image of the fiber bundle and the trap line (dotted line) formed by the double-sided polyhedral lens 1 at this time. As shown in FIG. 21, since the fundamental frequency of the fiber bundle can be lowered to near 0, the clad portion is not conspicuous and the moire combined with the TV camera is not conspicuous.

In the embodiment of FIG. 3 or FIGS. 18 and 20, the trap line where the MTF of the polyhedral lens is 0 is parallel to the X axis or the Y axis, but when the television camera is attached to the fiberscope. In order to remove the moire, the dark portion of the clad portion, or the dark portion of the clad portion when the naked eye is observed with a fiberscope, they are not necessarily parallel.

As shown in FIG. 22 (a), the boundary lines la, l
b is arranged at ± 45 ° with respect to the X-axis, and as shown in FIG. 22B, the trap line (dotted line) is provided near the fiber fundamental frequency (or higher frequency) point (circle in the figure). Should pass.

Further, the structure of the fourth embodiment of the optical device of the present invention shown in FIG. 23 may be used to remove the dark portion of the clad portion when observing with the naked eye with a fiberscope. That is, the dark area removing eyepiece adapter 75 shown in FIG.
As described above, the low-pass filter function may be made variable by allowing the double-sided polyhedral lens 1 housed in the eyepiece adapter 75 to rotate.

The distal end side of the ring-shaped frame body 76, which is the mounting portion of the eyepiece adapter 75, is externally fitted to the eyepiece portion 43 of the existing fiberscope (for example, reference numeral 32 in FIG. 15), and the fixing screw 77 (the eyepiece adapter 75 Detachable to the eyepiece 43)
I am trying to fix it. On the rear end side of the frame body 76, a lens frame 78 to which the double-sided polyhedral lens 1 is attached is fitted to the inner peripheral surface on the rear end side of the frame body 76 and is rotatably accommodated.

A groove 76a is formed in the frame 76 in the circumferential direction.
A pin 78a formed in the range of 0 ° or more and projectingly provided on the lens frame 78 penetrates through the groove 76a and projects. The double-sided polyhedral lens 1 can be rotated by rotating the protruding portion of the pin 78a protruding from the groove 76a.

Then, for example, from the reference position shown in FIG. 20 (for example, the state where the pin 78a projects upward), the pin 78a
Is rotated by 45 °, the state shown in FIG. 22 (a) can be set. When it is further rotated, the state shown in FIG. 24A can be set. As shown in FIG. 24A, the boundary lines la and lb are ± 45
Even when the X-axis is intersected at an angle other than °,
Frequency components of the fiber as shown in 4 (b) (circles in the figure)
If the trap line is made to pass in the vicinity of, the function of the low-pass filter can be obtained.

According to this embodiment, by mounting the eyepiece adapter 75 on the eyepiece portion 43 of the existing fiberscope 32, it is possible to erase the dark portion of the clad portion which obstructs the observation and deteriorates the image quality. An image suitable for is obtained. Such a multi-faceted lens adapter can be used for TV cameras, TV
You may attach it to the adapter.

By adjusting the amount of rotation, the image state most suitable for observation can be set. That is, at a fixed angle position (denoted as azimuth) where rotation is impossible, for example, in the state of FIG. 20A, it is not possible to set a desirable state in which the dark portion can be removed as shown in FIG.
In the state of (a), it may not be possible to set the desired state in which the dark portion can be removed as shown in FIG. 22 (b). Even in such a case, by adjusting the rotation amount, the double-sided polyhedral lens 1 can be set to a state in which an image that is most observable is obtained.

By the way, in the case of the double-sided polyhedral lenses 1, 51, 71, etc. having the polyhedral lens portions on both sides, when this is applied to all imaging optical systems, the angle ψ formed by the boundary lines on both sides is
When ψ ≦ 30 °, it is necessary to be careful not to cancel the refraction action on both surfaces. That is, ψ ≦ 30 ° and θa−θb ≠ 0 (25) Here, the condition of ψ = 0 and θa−θb = 0 is
As shown in FIG. 25, when the difference ψ ≦ 30 ° between the refraction directions on the A surface and the B surface of one light beam, the angles θa and θb are canceled by the two surfaces.

When ψ ≧ 30 °, the angles θa and θb can be selected almost freely. The low-pass filter function may be made variable by allowing the polyhedral lens 2 or the double-sided polyhedral lens 1 to change the decentering amount with respect to the light flux.

FIG. 26 shows an optical element 62 in the fifth embodiment which has both the function of an optical low pass filter and the function of image formation. The optical element 62 has a low-pass filter function with one surface of the optical element 62 serving as a polyhedral lens 62A, and has an imaging function with the other surface having a lens shape such as a normal convex lens 62B.

Further, as a shape of a polyhedral lens having an effect similar to that of the double-sided polyhedral lens 1, as shown in FIG. 26 (b), four surfaces such as a polyhedral lens 65 in which a polyhedral lens is formed by dividing into four surfaces on one surface are used. It is also possible that one surface has a multi-faceted lens surface 65A that is twisted like a fan blade, and the other surface is formed as a normal convex lens 65B.

By providing both the optical low-pass filter function and the lens function in this way, it is not necessary to provide a new lens, and the labor of assembling separate optical components and adjusting them is saved. As a result, it is possible to significantly reduce costs. In addition, variations between products can be reduced, and the size can be further reduced. The optical element 62 can be used, for example, in the eyepiece lens 50 or the imaging lens 53.

Although the number of divided surfaces of the polyhedral lens 65 is four, it may be any number such as three or five. FIG. 27 shows an example of an optical system in the sixth embodiment in which two multifaceted lenses 68 and 69 are arranged so that the direction in which the MTF decreases is changed. For example, in FIG. 15, the double-sided polyhedral lens 51 and the imaging lens 53 are shown. Can be used instead of.

One surface of each of the polyhedral lenses 68, 69 is a polyhedral lens surface 68A, 69B, and the other surface is provided with ordinary lens surfaces 68B, 69B.

The function of the optical system in the case of arranging two single-sided polyhedral lenses can have almost the same function as that of the double-sided polyhedral lens 1 in the first embodiment of FIG. The advantage is that it is easy to process.

In addition, the other surface which is not polyhedral is the lens surface 68.
By using B and 69B, it is not necessary to provide a separate lens. Further, three or more single-sided polyhedral lenses may be arranged side by side to form an optical system, or one double-sided polyhedral lens and one or more single-sided lenses may be combined to form an optical system. Also, one single-sided polyhedral lens and one
An optical system may be formed by combining one or more double-sided lenses.

As in the optical element 63 in the modification shown in FIG. 28 (a), a double-sided polyhedral lens 81 in which at least one of the surfaces of the double-sided polyhedral lens 1 is divided into aspherical surfaces 81a is used as the double-sided polyhedral lens 81, and the MTF is obtained. May be controlled. By doing so, the low-pass filter function can be freely changed.

Also for the single-sided polyhedral lens 2 of FIG. 2, the divided surfaces (two inclined surfaces) are made aspherical to control the MTF or low-pass filter function as shown in FIG. 28 (b). You may

Alternatively, it may be used to eliminate the clad portion of the fiberscope in which the clad portion of the fiber of the fiber is noticeably black.

Although it is difficult to shape the surface, the surface on one side may be a flat surface, a spherical surface, or an aspherical surface, so that the degree of freedom in the design of the optical system is increased and the function can be enhanced. Also in this example, equations (15), (16), (19), (20) and (2
At least one of 1) can be applied and the above-mentioned effects can be obtained. If the multifaceted lens shown in FIG. 28B is combined with a camera with an auto iris, it is convenient because the low-pass filter function can be changed with the change of the aperture diameter.

FIG. 29 shows a double-sided polyhedral lens 85 according to the seventh embodiment of the present invention. Boundary lines la and lb on both sides
However, when viewed from the -Z direction, this is an example of the polyhedral lens 85 that is off the optical axis and exists at a plurality of positions. When the light flux is thick, the light flux is divided into three images and the diaphragm diameter changes. In an optical system or a combination of optical systems, when the light beam is thin, the light beam is not split, and therefore the low-pass filter function can be changed by the aperture diameter.

The surface on one side may be divided into three or more. FIG. 30 shows an example of a polyhedral lens 86 whose cross-sectional shape is an aspherical surface in a direction perpendicular to the division boundary line 1 of the surface. In the modification of FIG. 2, only one parallel set of MTF trap lines can be obtained. However, in this embodiment, FIG.
The MTF can also be reduced in the direction parallel to the boundary line 1 as shown in (d).

30 (a), 30 (b) and 30 (c) show a single-sided polyhedral lens 86 in the eighth embodiment. FIG. 30 (a),
The polyhedral lens 86 shown in (b) and (c) is aspherical so as to increase the number of traps, and realizes the spatial frequency characteristic as shown in FIG. 30 (d).

In this embodiment, since it substantially has a function of dividing the dish image into a plurality of portions,
For example, an aspherical surface having an inflection point in the middle, or an aspherical surface (a) with multiple optical axes as shown in FIG. 31, (b),
A mountain-shaped aspherical surface or the like as shown in FIG.

FIG. 32 shows a single-sided polyhedral lens 92 according to the ninth embodiment of the present invention. This single-sided polyhedral lens 92 is an example having four divided surfaces. This is different from FIGS. 2 and 26B in that there is no step at the boundary. Also in this embodiment, it is desirable to satisfy at least one of formulas (15), (16), (20), and (21). Two surfaces of the single-sided polyhedral lens 92 that are not adjacent to each other have a twisted relationship like a propeller.

FIG. 33 shows a single-sided polyhedral lens 9 according to a modification.
In step 4, the MTF can be controlled by having the dividing planes 94a divided substantially in parallel and selecting the normal direction of each plane 94a. Also for this example, equations (15), (1
It is desirable to satisfy at least one of 6), (19), (20), and (21).

When the multifaceted lens 94 as shown in FIG. 33 is formed by plastic molding, glass molding, etc., some divided surfaces are made so that the grindstone of the mold grinding does not hit the ground surface so that the mold can be easily manufactured. A shape as shown in FIG. 33B is desirable.

In the above consideration, light has been treated geometrically. However, in each of the examples of FIGS. 1 and 11, the difference in height between the division surfaces is about 1 μ to several μ, and in such a case, it is necessary to consider wave optics, that is, in the MTF of the wedge prism. In addition, the polyhedral lens has a phase filter effect.

For example, FIG. 34 shows the optical path length Lo when the double-sided polyhedral lens 1 in the embodiment of FIG. 1 is viewed in the Z direction. A straight line shows an equal ray having an optical path length Lo.

Lo = Tz (n−1) / λc (26) where Tz is the thickness of the double-sided polyhedral lens 1 in the Z direction, X and Y.
Is a function of. N is the refractive index of the double-sided polyhedral lens 1,
λc is the wavelength used or its average.

Specifically, Tz is as follows. When X ≧ 0, Y ≧ 0, Tz = (− Y + X) P + To X ≧ 0, Y <0, Tz = (− Y−X) P + To X <0, Y ≧ 0, Tz = (Y + X ) P + To When X <0, Y <0, Tz = (Y-X) P + To Here, To is 1 mm and To represents the thickness of the double-sided polyhedral lens 1 at X = Y = 0.

Wave-optical MTF R (Ux ', Uy')
Is approximately given by the following equation (27). The pupil function is defined by H (X, Y) = A (X, Y) exp {2πiLo (X, Y)} (27). A (X, Y) is the amplitude transmittance of the pupil. Using this pupil function H (X, Y), R (Ux ′, Uy ′) ＝ (1 / C) ∬H (X, Y) H † (X-Xo, Y-Yo) dXdY (28) , Integration is performed over the entire pupil, and † represents the complex conjugate of H (X, Y). C is a standardization constant.

Xo = λcUx ′S, Yo = λcUy ′S (29) Here, S is an intermediate image (after the polyhedral lens) from the surface having the lowpass filter effect after passing through the surface of the polyhedral lens having the lowpass filter effect. (Image formed when it is assumed that there is no (exit side) lens system). The spatial frequencies in the intermediate image are represented by Ux 'and Uy'.

When the fiber spacing of the fiber bundle image of the intermediate image is represented by Pf ', equations (12), (22), (23)
Instead of 0 <R (Ux ′, Uy ′) <0.5 (30) √ (Ux ′ ・ Ux ′ + Uy ′ · Uy ′) = 1 / (Pf′sin 60 °) (31) By selecting (X, Y), the moire combined with the fiberscope can be reduced to 50% or less. In addition, √ () on the left side of the equation (31) represents the square root of ().

It is not necessary to satisfy equation (30) for all Ux 'and Uy' that satisfy equation (31), and equation (31) near the basic spatial frequency spectrum of the image of the fiber bundle is used.
Equation (30) may be satisfied for Ux ′ and Uy ′ that satisfy. Here, since the manufacturing error of only the fiber is several% and the magnification error of the lens is several%, the range of the basic spatial frequency of the image of the fiber bundle of about ± 10% means the vicinity of the spectrum.

Similarly, equation (32) may be satisfied instead of equation (3). 0 <R (1 / PxM, Uy ′) <0.5 (32) where Px ′ is the image size of one pixel of the solid-state image sensor 8 in the X direction at the intermediate image position.

Similarly, equation (33) may be used instead of equation (5). 0 <R (40 · 3.58 / Wy ′, Uy ′) <0.5 (33) Wy ′ is the vertical dimension of the effective portion of the solid-state image sensor 8 converted to the intermediate image position. Similarly, equation (34) may be used instead of equation (9).

0 <R (1920 / Wx ′, Uy ′) <0.5 (34) Wx ′ is the horizontal dimension of the effective portion of the solid-state image sensor 8 converted into the intermediate image position. Similarly, equation (35) may be used instead of equation (10).

0 <R (960 / Wx ′, Uy ′) <0.5 (35) Similarly, when the number of pixels in the horizontal direction is insufficient, formulas (34) and (3
The first argument of R in 5) may be multiplied by npx / 1920.

Consider the functional type of the optical path length Lo (X, Y). Astigmatism should not occur on the optical axis, but for that purpose, Lo (X, Y) should match Lo (X, Y) when rotated 360 ° / nr about the Z axis. However, nr is a natural number and nr ≧ 3 (36). The double-sided polyhedral lens 1 is an example in which nr = 4.

As described above, by treating a polyhedral lens in a wave-optical manner, more diverse low-pass filter performances can be obtained.

The present invention uses a videoscope, a general T
The present invention can also be applied to an image pickup apparatus such as a V camera, remove factors such as moire that deteriorate image quality, and realize an image pickup apparatus with low image quality and high image quality. It should be noted that embodiments and the like configured by partially combining the above-mentioned embodiments and modifications etc. also belong to the present invention.

[Additional Remarks] (1) A multifaceted lens having a spatial frequency low-pass filter function, in which at least two of the respective normals set substantially at the centers of the plurality of surfaces have a twist relationship with the optical axis, and An optical system or an imaging device in which boundaries between a plurality of surfaces are decentered with respect to the optical axis of the optical system.

(2) A multifaceted lens having a spatial frequency low-pass filter effect, in which at least two of the normals standing substantially at the centers of the plurality of surfaces are in a twist relation with the optical axis, and the plurality of surfaces are provided. An optical system or image pickup device in which the vicinity of the boundary line of is covered with a substance that does not transmit light.

(3) A multifaceted lens having a spatial frequency low-pass filter effect, in which at least two of the normals standing substantially at the centers of the plurality of surfaces are in a twist relationship with the optical axis, and the plurality of surfaces are provided. The optical system or the imaging device in which the area of the defective surface shape portion near the boundary line of satisfies the expression (15).

(4) The optical device according to claim 1 or 2, wherein a polyhedral lens is arranged at a position satisfying the expression (21).

(5) The optical device according to claim 1 or 2 or 3, wherein expression (12) and (either expression (22) or (23)) are satisfied.

(6) An optical device having an optical system having an optical element having one surface which is a normal lens surface and the other surface having two or more inclined surfaces which are in a twisted relationship divided with respect to the optical axis.

(7) At least one of a plurality of divided surfaces
The optical device according to claim 1 or 2, wherein one is a spherical surface or an aspherical surface.

(8) Expressions (32), (33), (34),
The optical device according to claim 1, wherein at least one of (35) is satisfied.

(9) In an image pickup apparatus equipped with a TV camera that can be attached to a plurality of types of optical endoscopes via optical adapters each having a built-in photographic lens, each optical adapter is attached to an optical endoscope. An imaging device set corresponding to a mirror, wherein at least one optical adapter has the polyhedral lens.

(10) The optical path length Lo (X, Y) in the optical axis direction at the coordinates (X, Y) of the polyhedral lens is set to 3 around the optical axis.
3. The optical device according to claim 1, wherein the optical path length Lo (X, Y) is the same as the optical path length when rotated 360 [deg.] / Nr with the above integer nr.

[0165]

As described above, according to the present invention, in an optical device having an optical system for observation or imaging, one surface and the other surface each have a multi-sided surface, and each multi-sided surface At least two surfaces in each of the polyhedral surfaces of the respective normals set up in the vertical direction have a twist relationship with the optical axis, and a filter function for removing a specific spatial frequency component in an image formed through at least two surfaces in the polyhedral surfaces is provided. Since it has an optical system provided with the optical element, it is possible to form an optical filter having a high function of removing factors such as moire that deteriorate image quality at low cost.

Therefore, it is possible to effectively remove moire or the like in an image pickup apparatus such as an endoscope, a videoscope, a TV camera for an endoscope, a general TV camera, etc., which uses this optical element.

[Brief description of drawings]

FIG. 1 is a diagram showing a double-sided polyhedral lens used in a first embodiment.

FIG. 2 is a diagram showing a single-sided polyhedral lens used in a modification of the first embodiment.

FIG. 3 is a configuration diagram of an endoscope device of a modified example of the first embodiment.

FIG. 4 is an explanatory diagram of a pixel array of a solid-state image sensor.

FIG. 5 is a perspective view showing an image pickup optical system of a television camera.

FIG. 6 is a basic explanatory diagram for removing moire by a double image using a single-sided polyhedral lens.

FIG. 7 is an explanatory diagram of having a moire removing function even in a defocused state.

FIG. 8 is an explanatory diagram showing the action of removing the generation of moire due to color modulation by the trap line in the spatial frequency plane.

FIG. 9 is an explanatory diagram showing an array of images of a fiber bundle.

FIG. 10 is an explanatory diagram showing a disturbed portion near the boundary of a polyhedral lens.

FIG. 11 is an enlarged view of the disordered portion of FIG.

FIG. 12 is an explanatory diagram showing a state in which a boundary of a polyhedral lens is decentered and formed.

FIG. 13 is an explanatory view showing that the vicinity of the center of the boundary of the polyhedral lens is ground into a flat surface.

FIG. 14 is an explanatory diagram showing that it is desirable to dispose a polyhedral lens near a pupil.

FIG. 15 is an overall configuration diagram of the endoscope apparatus according to the first embodiment.

FIG. 16 is a system configuration diagram of a second embodiment of the present invention.

FIG. 17 is an explanatory diagram showing the structure of a fiberscope according to a third embodiment of the present invention.

FIG. 18 is an explanatory diagram showing a direction of a boundary line of a double-sided polyhedral lens and an arrangement of fiber bundles.

FIG. 19 is an explanatory view showing a dark portion removing action of the clad portion according to the third embodiment in a spatial frequency plane.

FIG. 20 is an explanatory diagram showing a boundary line direction of a double-sided polyhedral lens and an arrangement of fiber bundles in a first modification example of the third example.

FIG. 21 is an explanatory view showing the dark portion removing action of the cladding portion according to the first modification of the third embodiment in a spatial frequency plane.

FIG. 22 is an explanatory diagram showing a direction of a boundary line of a double-sided polyhedral lens and a dark portion removing action of a clad portion in a spatial frequency plane in a second modification of the third embodiment.

FIG. 23 is a cross-sectional view showing a dark area removing eyepiece adapter in the fourth embodiment.

FIG. 24 is an explanatory diagram showing the direction of the boundary line of the double-sided polyhedral lens and the dark portion removing action of the cladding portion in the spatial frequency plane when the eyepiece adapter is rotated.

FIG. 25 is an explanatory diagram showing that the filter function is lost when the angle formed by the boundary lines of the double-sided polyhedral lens satisfies a specific condition.

FIG. 26 is a diagram showing an optical element having a lens function and a filter function in the fifth example.

FIG. 27 is a diagram showing an optical system according to a sixth embodiment.

FIG. 28 is a diagram showing an optical element according to a modification of the sixth embodiment.

FIG. 29 is a diagram showing a double-sided polyhedral lens in a seventh example.

FIG. 30 is a diagram showing a single-sided polyhedral lens in an eighth example.

FIG. 31 is a diagram showing a single-sided polyhedral lens according to a modified example of the eighth example.

FIG. 32 is a diagram showing a single-sided polyhedral lens in a ninth example.

FIG. 33 is a diagram showing a single-sided polyhedral lens in a modified example of the ninth example.

FIG. 34 is a diagram showing an optical path length in a double-sided polyhedral lens.

FIG. 35 is a configuration diagram of a conventional example.

[Explanation of symbols]

 1 ... Double-sided polyhedral lens 2 ... Single-sided polyhedral lens 3 ... Endoscope device 5 ... Hard endoscope 6, 34 ... TV camera 7 ... Light source device 8 ... Solid-state image sensor 9 ... CCU 10 ... Color monitor 18 Objective lens ... 19 ... Relay optical system 20 ... Eyepiece 21 ... Imaging lens (imaging lens) l, la, lb ... Boundary line O ... Optical axis 32 ... Fiberscope 33 ... Imaging lens adapter 51 ... Double-sided polyhedral lens

Claims (5)

[Claims] 1. An optical device provided with an optical system for observation or imaging, wherein one surface and the other surface each have a multi-faced surface, and each of the normals set up on each facet At least two surfaces in the polyhedral surface are in a twist relationship with the optical axis,
An optical device comprising an optical system provided with an optical element having a filter function for removing a specific spatial frequency component in an image formed through at least two surfaces in each of the above-mentioned multiple surfaces. 2. An optical device provided with an optical element having a spatial frequency low-pass filter effect, in which at least two of the respective normal lines standing substantially at the centers of a plurality of surfaces are in a twist relationship with the optical axis. 3. The optical element according to claim 1, wherein the eyepiece optical system of the fiberscope in which the optical system for image transmission is formed by a fiber bundle in which fibers are bundled has a polyhedral lens for removing a specific frequency. Optical device. 4. The optical system provided with the optical element is set to have a spatial frequency characteristic for removing a spatial frequency component based on the arrangement in an optical member having a two-dimensional arrangement. 2. The optical device according to item 2. 5. The optical element is used in an eyepiece optical system of a fiberscope in which an image transmission optical system is formed by a fiber bundle in which fibers are bundled, and the one surface is a boundary line l.
Dividing by a, the normals of the two surfaces having a twist relationship form an angle θa with the optical axis, and the other surface is a boundary line l.
Dividing by b, the normals of the two surfaces in a twisted relationship form an angle θb with the optical axis respectively, the refractive index of the optical element is n, and the image formed by the eyepiece optical system in front of the optical element is If the distance from the optical element is Sf, the magnification of the eyepiece optical system from the optical element to the image plane is βr, and the distance between fibers in the image of the fiber bundle is Pf, then 0.75 / Pf ≦ 1 /|2(n−1)θaSfβr|≦1.5/Pf 0.75 / Pf ≦ 1 / | 2 (n−1) θbSfβr | ≦ 1.5 / Pf and the angle ψ formed by the boundary lines la and lb is 45 ° ≦ The optical device according to claim 1, wherein the optical device is set so as to satisfy ψ ≦ 75 °.