Imaging apparatus

• US 5,598,205 A
• Filed: 04/22/1994
• Issued: 01/28/1997
• Est. Priority Date: 04/22/1994
• Status: Expired due to Term

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Nishioka, Kimihiko
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US08/231,176
• Time in Patent Office: 1,012 Days
• Field of Search: 348/65, 348/335, 348/294, 359/720
• US Class Current: 348/65
• CPC Class Codes: A61B 1/05 characterised by the image sensor, e.g. camera, being in the distal end portion
• CPC Class Codes: A61B 1/055 having rod-lens arrangements
• CPC Class Codes: G02B 23/2446 of the image relay G02B23/26 takes precedence
• CPC Class Codes: G02B 23/2484 Arrangements in relation to a camera or imaging device processing or control of video signals generated by an endoscope H04N23/60, H04N23/70
• CPC Class Codes: H04N 23/555 for picking-up images in sites, inaccessible due to their dimensions or hazardous conditions, e.g. endoscopes or borescopes

Abstract

An imaging apparatus includes an objective lens system for forming an image of an object, a solid-state image pickup device, a signal processor and a display device. The objective lens system includes at least one revolutionally asymmetrical refractive surface for deforming the image formed by the objective lens system and is configured so as to deform further the image which is deformed by the signal processor.

Claims

1. An imaging apparatus comprising:

an objective lens system for forming an image of an object, a solid-state image pickup device for receiving the image formed by said objective lens system, a signal processing means for generating video signals from signals output from said solid-state image pickup device and a display means for displaying an image of the object by using said video signals;

wherein said objective lens system comprises at least one revolutionally asymmetrical refracting surface expressed by the formula (5) shown below for projecting a deformed image of said object onto said solid-state image pickup device and wherein said signal processing means further deforms signals of the deformed image provided from said solid-state image pickup device for displaying an image of the object on said display means,

wherein the reference symbol i represents an ordinal number of a surface, the reference symbol x, y and z designate values on x, y and z axes respectively on an coordinates system on which a direction of an optical axis is taken as the x axis and a vertex of the refractive surface is taken as an origin, the reference symbol R_i denotes a radius of curvature of a reference sphere of the refractive surface, the reference symbols B_yi, B_zi, . . . represent aspherical surface coefficients, and the reference symbols E_1i, E_2i, . . . designate aspherical surface coefficients.

3. An imaging apparatus according to claim 1 or 2 wherein said objective lens system comprises an aperture stop, said revolutionally asymmetrical refractive surface is disposed on the object side of said aperture stop and said imaging apparatus satisfies the following condition:

space="preserve" listing-type="equation">φ

.sub.yi >

φ

.sub.zi (

     14)

wherein φ

_yi =2(n_i -n_i-1) B_yi (10) , φ

_zi =2(n_i -n_i-1) B_zi (11) and the reference symbols n_i-1 and n_i represent refractive indices of media located on the object side and the image side respectively of said revolutionally asymmetrical refractive surface.

4. An imaging apparatus according to claim 1 or 2 wherein said objective lens system comprises an aperture stop, said revolutionally asymmetrical refractive surface is disposed on the image side of said aperture stop and said imaging apparatus satisfies the following condition:

space="preserve" listing-type="equation">φ

.sub.yi <

φ

.sub.zi (

     15)

wherein φ

_yi =2(n_i -n_i-1) B_yi (10), φ

_zi =2(n_i -n_i-1) B_zi (11), the reference symbols n_i-1 and n_i represent refractive indices of media located on the object side and the image side respectively of said revolutionally asymmetrical surface.

5. An imaging apparatus according to claim 1 or 2 wherein said objective lens system comprises a plurality of revolutionally asymmetrical refracting surfaces and said imaging apparatus satisfies the following condition:

space="preserve" listing-type="equation">(φ

.sub.zi -φ

.sub.yi)(φ

.sub.zj -φ

.sub.yj)<

0

wherein φ

_yi =2(n_i -n_i-1) B_yi, φ

_zi =2(n_i -n_i-1) B_zi, and the reference symbols n_i-1 and n_i represent refractive indices of media located on the object side and the image side respectively of a revolutionally asymmetrical surface i, and the reference symbols n_j-1 and n_j designate refractive indices of media located on the object side and the image side respectively of another revolutionally asymmetrical refractive surface j.

6. An imaging apparatus according to claim 1 or 2 wherein said objective lens system comprises an aperture stop, a plurality of revolutionally asymmetrical refractive surfaces are disposed on the object side of said aperture stop, and said imaging apparatus satisfies the following condition:

space="preserve" listing-type="equation">Σ

(φ

.sub.zi -φ

.sub.yi)<

0 (18)

wherein φ

_yi =2(n_i -n_i-1) B_yi, φ

_zi =2(n_i -n_i-1) B_zi and the reference symbols n_i-1 and n_i represent refractive indices of media located on the object side and the image side respectively of each of said revolutionally asymmetrical refractive surfaces.

7. An imaging apparatus according to claim 1 or 2 wherein said objective lens system comprises an aperture stop, a plurality of revolutional asymmetrical surfaces are disposed on the image side of said aperture stop and said imaging apparatus satisfies the following condition:

space="preserve" listing-type="equation">Σ

(φ

.sub.zi -φ

.sub.yi)>

0 (15)

wherein φ

_yi =2(n_i -n_i-1) B_yi, φ

_zi =2(n_i -n_i-1) B_zi and the reference symbols n_i-1 and n_i represent refractive indices of media located on the object side and the image side respectively of each of said revolutionally asymmetrical surfaces.

8. An imaging apparatus according to claim 1 or 2 wherein said objective lens system comprises a plurality of revolutionally asymmetrical refractive surfaces and said imaging apparatus satisfies the following condition:

space="preserve" listing-type="equation">|Σ

(φ

.sub.zn h.sub.zn -φ

.sub.yn h.sub.yn)|<

1/3(φ

.sub.z h.sub.z0 +φ

.sub.y h.sub.y0)

wherein φ

_yn =2(n_n -n_n-1) B_yn, φ

_zn =2(n_n -n_n-1) B_zn, the reference symbols n_n-1 and n_n represent refractive indices of media located on the object side and image side respectively of a revolutionally asymmetrical refractive surface n, the reference symbols n_m-1 and n_m designate refractive indices of media located on the object side and the image side respectively of another revolutionally asymmetrical surface m, the reference symbols h_zn and h_yn denotes heights of a paraxial ray in the z and y directions respectively on the refractive surface n, the reference symbols h_zm and h_ym represent heights of the paraxial ray in the z and y directions respectively on the refractive surface m, and the reference symbols h_z0 and h_y0 designate heights of the paraxial ray in the z and y directions respectively on a first surface of said objective lens system.

2. An electronic endoscope comprising:

an illuminating means for illuminating an object,

an objective lens system for forming an image of the object,

a solid-state image pickup device for receiving the image formed by said objective lens system,

signal processing means for generating video signals from signals output from said solid-state image pickup device, and

display means for displaying an image of the object by using said video signals;

wherein said objective lens system has at least one revolutionally asymmetrical refractive surface for projecting a deformed image of the object onto said solid-state image pickup device,

wherein said signal processing means further deforms signals of the deformed image provided from said solid-state image pickup device for displaying an image of the object on said display means, and

wherein the revolutionally asymmetrical refractive surface disposed in said objective lens system is expressed by the following formula;

##EQU8## wherein the reference symbol i represents an ordinal number of a surface, the reference symbol x, y and z designate values on x, y and z axes respectively on a coordinates system on which a direction of an optical axis is taken as the x axis and a vertex of the refractive surface is taken as an origin, the reference symbol R_i denotes a radius of curvature of a reference sphere of the refractive surface, the reference symbols B_yi, B_zi, . . . represent aspherical surface coefficients, and the reference symbols E_1i, E_2i, . . . designate aspherical surface coefficients.