WO2001063915A1

WO2001063915A1 - Light-receiving sensor enabling superwide-angle image pickup, and electronic digital camera comprising it

Info

Publication number: WO2001063915A1
Application number: PCT/JP2001/001260
Authority: WO
Inventors: Hideaki Ishizuki
Original assignee: Hideaki Ishizuki
Priority date: 2000-02-22
Filing date: 2001-02-21
Publication date: 2001-08-30
Also published as: AU3410601A

Abstract

A light-receiving sensor comprising a semiconductor device, e.g. a CCD or a C-MOS, and an electronic digital camera comprising the light-receiving sensor. The light receiving sensor has a light-receiving surface of a concave spherical focusing cross-section (2), and a diaphragm (3) is disposed the central position in the thickness of a superwide-angle aspherical single lens (1). Excellent focusing characteristics are provided up to a superwide angle and an image can be observed with high resolution and high optical characteristics.

Description

Specification

Light-receiving sensor that enables ultra-wide-angle imaging, and electronic digital cameras using it

The present invention uses a lens with excellent ultra-wide-angle optical characteristics and a special optical system that uses a concave spherical optical sensor to capture and observe images and information with a viewing angle near 180 degrees at a time. Related to devices such as cameras and digital cameras. Background art

A conventional electronic or digital camera using a light receiving sensor optically forms a planar image using a complicated imaging lens system having an optical design that combines several lenses. This is because the angle of incidence of light rays, the so-called angle of view, is narrow, and generally only images in the observation viewing angle range of about 30 to 50 degrees can be taken, and there are only functionally limited uses. . These are optical designs based on ordinary lens design methods, and as the angle of incidence increases, the image surface curves, that is, the so-called field curvature aberration increases, and the light receiving surface becomes flat. Correction to the imaging system becomes difficult. Therefore, with a commercially available surveillance camera having a wider viewing angle of about 80 to 120 degrees, the light beam incident at a high angle is remarkably sharply refracted and extremely difficult optically on a fixed plane. Since the light is focused, significant distortion occurs. In other words, despite the enormous need for super-wide-angle monitoring and observation, including surveillance cameras, dental and medical cameras, and imaging devices, images are remarkable at the edges of the imaging screen (ultra-wide-angle incident area). Distortion, the original shape is not retained, or the focus is blurred, which hinders strict observation requirements such as shape recognition and character recognition.

Therefore, in the present invention, such a remarkable aberration as seen in a camera using the conventional light receiving sensor is removed, and the viewing angle is approximately 180 degrees. It is an object of the present invention to provide an electronic or digital camera capable of observing high resolution and high image quality while eliminating aberrations such as so-called 撙 -type distortion up to the observation region. Disclosure of the invention

To achieve the above objective, we have developed an ultra-wide-angle aspheric lens that forms an image with excellent optical characteristics without causing total reflection even when the incident angle of light reaches 90 degrees. This lens breaks the usual concept of planar imaging and utilizes the characteristic of the field curvature in front of the plane characteristic of high-angle incidence. In other words, by changing the image plane from a plane to match the position of the curvature of the image plane, the light beam can be converged without difficulty, and the aberrations that characterize the optical characteristics can be significantly reduced to a wide viewing angle. Become. Therefore, including C C D and C-M O S

We have invented an observation device in which the light receiving surface of the light receiving element and sensor is formed as a spherical concave surface, an aspherical concave surface, and a cylindrical concave surface that approximates a spherical surface to the light reception near the equatorial plane. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view showing an image formed by ray tracing of a super-wide-angle aspheric single lens for image capturing according to the present invention, and FIG. 2 facilitates observation of a concave spherical surface near an equatorial plane. Therefore, the image plane is a concave cylindrical shape, the third figure is a spot focusing figure obtained as a result of ray tracing in the first figure, and the fourth figure is the optical characteristics and resolution of this lens Fig. 5 (a) shows an example of a semiconductor sensor for imaging a concave spherical surface, and Fig. 5 (b) shows a bundle light whose end surface is polished to a concave spherical surface. FIG. 2 is a diagram illustrating a fiber. The best form for carrying out Inoaki

The present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an analysis example showing actual ray tracing of the ultra-wide-angle aspherical single lens 1 developed in the present invention. Rays incident from infinity at an angle of 0 ° to 10 °, 20 ° 30 ° at an interval of 10 ° to 80 ° are refracted by an ultra-wide-angle aspherical single lens 1, and each ray has a constant radius. A ray tracing diagram that focuses on P 0, P 1, P 2, P 3 --- P 8 on the circumference and converges on the spherical imaging section 2 to an ultra-wide angle is shown. The aperture 3 is realized by, for example, providing a groove having an appropriate width in the center of the lens by cutting or the like, and fitting a black light-blocking member or the like into the groove. This figure shows a two-dimensional cross section, but in three dimensions a naturally spherical image is formed. Although a single lens is shown in the figure, it goes without saying that a compound lens having the same light collecting principle may be used.

Fig. 2 shows only the area near the equatorial plane of the spherical surface (Y in the figure) in order to make use of the above-mentioned principle of spherical imaging in actual applications and to make it possible to easily manufacture a light-receiving sensor for spherical image formation. (Axial direction) is approximated by a plane, and an optical system with a cylindrical concave surface is devised. In the figure, a ray from, for example, A—A in the (X, Z) plane forms an image at A, 1 A on the circumference at a wide viewing angle 01. However, assuming that rays from B-B in the direction along the Y-axis are imaged on a straight line B, 1B 'with a relatively narrow viewing angle Θ2, the field curvature can be reduced and 8' — Even if 8, is on a straight line along the ¥ direction, the effect on the imaging characteristics can be omitted. This method is suitable for applications such as an electronic camera that can capture a panoramic landscape that requires only an ultra-wide-angle observation, and is considered to be a more practical invention. Using commonly used expressions for the shape of an aspheric lens,

Z = cr ² / (1 + sqrt (1-1 (1 + k) c ² r ² ) + a, r ² + a ₂ r ⁴ + a 3 r ⁶ + o

And c = 1 / R

Is displayed with.

Where r is the cross-sectional radius of the rotating aspheric surface, and Z is the optical axis whose origin is the vertex of the rotating surface The position coordinates of the surface in the direction, c is the reciprocal of the radius at the origin or the curvature, k is the conic coefficient of the aspheric surface, and among even higher order aspherical coefficients, ct i is the secondary aspherical coefficient, α ₂ is The fourth order aspherical coefficient, α ₃ is the sixth order aspherical coefficient and the like.

The super-wide-angle aspherical single lens used in the present invention shown in FIGS. 1 and 2 and the shape of the light receiving surface are shown in Table 1 below. table 1

In the example shown in Table 1, for the incident light, the front surface of the single lens is the first lens surface and the rear surface is the second lens surface. When the object is positioned at infinity from the first surface and the aperture 4 is provided in the middle of the single lens, the distance from the lens tip to the center of the aperture is 3 mm, the distance from the aperture center to the rear end of the lens Indicates that the distance from the rear end of the lens to the Gaussian imaging plane is 3.5 mm on the optical axis. In these optimal design examples, the curvature for the aspheric surface and the higher order coefficients up to the sixth order are determined and shown. The imaging surface has a concave shape with a radius of -7.453 mm. The lens material is PMMA and the outer diameter is φ8.0 mm. As can be seen from Fig. 1, as can be seen from the tracing of a light beam with an incident angle of 10 to 80 degrees, the incident angle and the exit angle are almost equal even at a high angle of incidence, compared to a general plane image. In addition, the distance between the imaging positions P 0, P 1, P 2, P 3-P 8 at every 10 ° is also kept very evenly by the arc on the concave light receiving surface in Fig. 1. . That is Even if the observed image is spread out on a plane, the curvature aberration is remarkably small up to wide angles compared to normal, and in this example it is calculated to be within 15% even at around 80 degrees.

Fig. 3 shows a spot diagram of parallel incident light rays for performance evaluation when the super-wide-angle aspherical single lens 1 shown in Table 1 is used. P 0, P 1, P 2, and P 3 —P 8 in FIG. 3 correspond to the light condensing positions shown in FIG. 1, respectively, and are described for reference. The scale at the position P 0 in FIG. 3 has a width of 100 microns. An extremely excellent spot image is obtained, and the spot diameter is about 60 to 70 microns up to an incident angle of about 50 °. In the vicinity of 80 degrees, the shape spreads in the horizontal direction, and the effect of coma becomes remarkable, but the spot diameter is extremely good, about 100 microns. Although these figures do not show a color display, the spread of spots due to chromatic aberration is hardly observed.

FIG. 4 shows the MTF. The vertical axis shows the value of the optical MTF (modulation function), and the horizontal axis shows the spatial frequency (line number / mm) corresponding to the resolution. The numerical values at the top of the figure indicate the incident angles of the rays, and the curve data is written separately for the longitudinal aberration (meridional direction) T and the lateral aberration (sagittal direction) S of ray tracing, and P 0 , Pl, P2, P3--P8 are the MTF characteristics corresponding to the condensing positions shown in FIG. From this figure, a resolution close to 50 (number of lines / mm) can be obtained even at ultra-wide-angle incidence, and high optical characteristics are guaranteed up to a wide viewing angle compared to conventional planar imaging cameras.

FIG. 5 shows an example of a light-receiving sensor according to the present invention. FIG. 5 (a) shows an example of a semiconductor sensor for concave spherical imaging, and a spherical imaging section 2 includes a silicon substrate 5 and a silicon substrate 5. FIG. 3 is a schematic diagram including a circuit pattern 6 formed by transfer. Currently, imaging devices for capturing images include semiconductor devices such as CCD sensors and C-MOS. In C-MOS, pixel transfer is a method in which, when extracting a signal at an observation place on a two-dimensional (X, Y) plane, each of X and γ is addressed (specified) to extract the electric charge of the intersecting pixel. This method is easy to speed up It has a characteristic. On the other hand, CCDs have a problem in that charges cannot be transferred at high speed due to the structure of transmitting charges in a bucket relay, but they have the advantage that noise is small and high image quality can be secured. In any case, these configurations use a polycrystalline silicon planar substrate that has been mirror polished, and in our present invention, it has a concave spherical surface, a concave cylindrical surface, or a concave cylindrical surface. Since it is formed by an aspherical surface, it seems very difficult to bend and mold a conventional hard silicon substrate. One way to solve this is to use a liquid crystal or amorphous high-purity silicon for the silicon substrate 5 or to develop a new semiconductor material, as shown in Fig. 5 (a). A method that can easily form an arbitrary free curved surface due to its flexibility and rigidity is expected. Or, after that, it is conceivable to develop a technology to crystallize and sinter these into a concave spherical shape. Other methods would allow ultra-thin silicon substrates to be machined, and bending would allow concave cylindrical surfaces. When writing the information of the mask pattern, which records the pattern of the circuit etc. on the spherical surface of silicon etc. on these concave surfaces, into the photo resist by UV irradiation exposure, the principle of light collection shown in Fig. 1 is used. Replace the position of the observation object with a mask pattern, and use an ultra-wide-angle aspheric lens system with higher performance and higher resolution according to the accuracy of the circuit pattern. When bending thin silicon substrates, naturally, exposure technology is not required.

FIG. 5 (b) on the right side of FIG. 5 is a view showing a bundle optical fiber 17 of another embodiment, the end face of which is polished to a concave spherical surface. This is based on the imaging principle shown in Fig. 1 and transmitted to the inside of the optical fiber to a relatively wide angle by imaging on a concave spherical surface from an aspheric objective lens located near the center of the spherical imaging section 2. Then, a method of observing an image with a semiconductor detection element and a light receiving sensor connected to the end face of the exit light exit is conceivable. However, even if the ultra-wide angle is difficult because the numerical aperture NA of the optical fiber is limited by its material, an image with little field curvature aberration and distortion can be expected by the principle of the present invention. Industrial applicability

As described above, the electronic device and digital device according to the present invention that enable imaging with an ultra-wide angle and high optical characteristics use a light-receiving sensor using a semiconductor element such as a CCD sensor or a C-MOS to achieve an ultra-wide angle. It provides high-resolution, high-resolution images with low distortion in a wide variety of industrial fields, including surveillance cameras and observation fields for medical purposes. As a result, the performance of information transmission is greatly improved, which is useful for accurate and high-speed information.

Claims

The scope of the claims

1. A light-receiving sensor that uses a CCD element, C-MOS, etc., formed of elements whose light-receiving surface is arranged in a concave spherical shape or a concave aspherical shape.

2. The light-receiving sensor according to claim 1, which is formed of a concave cylindrical shape.

3. A light-receiving sensor having a shape according to claim 1 or 2, wherein the device has a silicon substrate portion made of amorphous liquid crystal, an amorphous material, or the like, and a circuit pattern.

4. A light-receiving sensor having a shape according to claim 2, wherein a semiconductor element such as an extremely thin CCD or C-MOS is bent by bending or the like.

5. An electronic camera capable of capturing an ultra-wide-angle field of view, having a light-receiving system according to claims 1 and 2, wherein the lens system is constituted by an ultra-wide-angle aspherical single lens 1 provided with an aperture 3 at the center position thereof. , Digital photography equipment.

6. An electronic camera and a digital photographing apparatus capable of photographing an ultra-wide-angle field of view, wherein the lens system comprises a plurality of spherical lenses or aspherical lenses, and has the light receiving system according to claim 1 or 2.