Hologram scanner

• US 4,768,847 A
• Filed: 07/23/1984
• Issued: 09/06/1988
• Est. Priority Date: 08/18/1983
• Status: Expired due to Term

• Current Assignee: Yokogawa Electric Corporation
• Original Assignee: Yokogawa Electric Corporation
• Inventors: Shiozawa, Takahiro, Iwaoka, Hideto
• Primary Examiner(s): ARNOLD, BRUCE
• Application Number:
  US06/633,713
• Time in Patent Office: 1,506 Days
• Field of Search: 350/3.71
• US Class Current: 359/18
• CPC Class Codes: G02B 26/106 having diffraction gratings as scanning elements, e.g. holographic scanners holographic optical elements G02B5/32, holography G03H

Abstract

An optical scanning device comprising a transmission or reflection hologram disk, wherein recording beams, such as an object and a reference beam which are used in preparing holograms, and a reconstructing beam which is used in reconstructing or scanning, are spherical waves having different wavelengths; and wherein the sources of recording beams and reconstructing beams are located at different positions for enabling the beams to fall obliquely on the hologram disk to cause a reconstructed image on a focusing or scanning plane to be subjected to linear aberration free scanning. The incident angle of the reconstructing beam on the hologram disk meets the Bragg condition for high diffraction efficiency.

Claims

1. An optical scanning device comprising a flat transmission or reflection hoogram disk, wherein recording beams comprising an object beam and a reference beam and used in preparing holograms and a reconstructing beam used in reconstructing or scanning are all of diverging or converging spherical waves with said object beam and said reference beam having the same wavelength and said reconstructing beam having a different wavelength;

and wherein said optical scanning device comprises beam sources of said recording beams and said reconstructing beam are located at different positions for enabling said recording and reconstructing beams to fall obliquely on said hologram disk to cause a reconstructed image on a focusing or scanning plane to be subjected to linear aberration free scanning;

wherein said beam sources of said reference beam, said object beam and said reconstructed beam are positioned in a region wherein said reconstructing beam falls on said hologram disk so as to substantially satisfy the following equations;

space="preserve" listing-type="equation">f.sub.C (τ

r.sub.CO, τ

r.sub.CR, r, θ

, φ

, λ

.sub.C)≈

f.sub.R (τ

r.sub.RO, τ

r.sub.RR, r, θ

, φ

, λ

.sub.R)

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

.sub.C (τ

r.sub.CO, τ

r.sub.CR, r, θ

, φ

, λ

.sub.C)≈

Φ

.sub.R (τ

r.sub.RO, τ

r.sub.RR, r, θ

, φ

, λ

.sub.R)

wherein f_C is the spatial frequency of the interference fringes recorded on the holograms by said object and reference beams;

Φ

_C is the inclination of the interference fringes;

f_R is the spatial frequency of the intereference fringes formed on the holograms by a hypothetical beam converging at one point on the focusing plane and the reconstructing beams;

Φ

_R is the inclination of the interference fringes;

τ

r_CO is a vector indicative of the position of the object beam source;

τ

r_CR is a vector indicative of the position of the reference beam source;

τ

r_RO is a vector indicative of the position of the hypothetical beam source;

τ

r_RR is a vector indicative of the position of the reconstructed beam source;

(r, θ

) are coordinates on the hologram disk;

φ

is angle of rotation of the hologram disk;

λ

_C is the wavelength of said recording beam; and

λ

_R is the wavelength of said reconstructing and said hypothetical beams;

wherein said hologram disk is a transmission hologram disk;

wherein said reconstruction beam is of a divergent spherical wave; and

wherein the distance between said position of said reconstructing beam source and said hologram substantially satisfies the following equation;

space="preserve" listing-type="equation">l.sub.r =(9.4×

10.sup.-2 r.sub.a +22) exp (2.6×

10.sup.-3 l.sub.d)

wherein l_r is is the distance between said reconstructing beam source and said hologram disk in mm;

r_a is the distance between the center of rotation of said hologram disk and the position wherein said reconstructing beam falls on said hologram disk in mm; and

l_d is the distance between said hologram disk and said scanning plane in mm.

2. An optical scanning device comprising a flat transmission or reflection hologram disk, wherein recording beams comprising an object beam and a reference beam and used in preparing holograms and a reconstructing beam used in reconstructing or scanning are all of diverging or converging spherical waves with said object beam and said reference beam having the same wavelength and said reconstructing beam having a different wavelength;

and wherein said optical scanning device comprises beam sources of said recording beams and said reconstructing beam are located at different positions for enabling said recording and reconstructing beams to fall obliquely on said hologram disk to cause a reconstructed image on a focusing or scanning plane to be subjected to linear aberration free scanning;

wherein said beam sources of said reference beam, said object beam and said reconstructing beam are positioned in a region wherein said reconstructing beam falls on said hologram disk so as to substantially satisfy the following equations;

space="preserve" listing-type="equation">f.sub.C (τ

r.sub.CO, τ

r.sub.CR, r, θ

, φ

, λ

.sub.C)≈

f.sub.R (τ

r.sub.RO, τ

r.sub.RR, r, θ

, φ

, λ

.sub.R)

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

.sub.C (τ

r.sub.CR, τ

r.sub.CR, r, θ

, φ

, λ

.sub.C)≈

Φ

.sub.R (τ

r.sub.RO, τ

r.sub.RR, r, θ

, φ

, λ

.sub.R)

wherein f_C is the spatial frequency of the interference fringes recorded on the holograms by said object and reference beams;

Φ

_C is the inclination of the interference fringes;

f_R is the spatial frequency of the interference fringes formed on the holograms by a hypothetical beam converging at one point on the focusing plane and the reconstruction beam;

Φ

_R is the inclination of the interference fringes;

τ

r_CO is a vector indicative of the position of the object beam source;

τ

r_CR is a vector indicative of the position of the reference beam source;

τ

r_RO is a vector indicative of the position of the hypothetical beam source;

τ

r_RR is a vector indicative of the position of the reconstructed beam source;

(r, θ

) are coordinates on the hologram disk;

φ

is angle of rotation of the hologram disk;

λ

_C is the wavelength of said recording beam; and

λ

_R is the wavelength of said reconstructing and said hypothetical beams;

wherein said hologram disk is a transmission hologram disk;

wherein said reconstructing beam is of a divergent spherical wave; and

wherein the incident angle of said reconstructing beam substantially satisfies the following equation;

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

.sub.r =(0.22/r.sub.a +4.4×

10.sup.-3)l.sub.d +7.5

wherein θ

_r is the incident angle of said reconstructing beam in degrees;

r_a is the distance between the center of rotation of said hologram disk and the position where said reconstructing beam falls on said hologram disk in mm; and

l_d is the distance between said hologram disk and said scanning plane in mm.

3. An optical scanning device comprising a flat transmission or reflection hologram disk, wherein recording beams comprising an object beam and a reference beam and used in preparing holograms and a reconstructing beam used in reconstructing or scanning are all of diverging or converging spherical waves with said object beam and said reference beam having the same wavelength and said reconstructing beam having a different wavelength;

and wherein said optical scanning device comprises beam sources of said recording beams and said reconstructing beam are located at different positions for enabling said recording and reconstructing beams to fall obliquely on said hologram disk to cause a reconstructed image on a focusing or scanning plane to be subjected to linear aberration free scanning;

wherein said beam sources of said reference beam, said object beam and said reconstructing beam are positioned in a region wherein said reconstructing beam falls on said hologram disk so as to substantially satisfy the following equations;

space="preserve" listing-type="equation">f.sub.C (τ

r.sub.CO, τ

r.sub.CR, r, θ

, φ

, λ

.sub.C)≈

f.sub.R (τ

r.sub.RO, τ

r.sub.RR, r, θ

, φ

, λ

.sub.R)

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

.sub.C (τ

r.sub.CO, τ

r.sub.CR, r, θ

, φ

, λ

.sub.C)≈

Φ

.sub.R (τ

r.sub.RO, τ

r.sub.RR, r, θ

, φ

, λ

.sub.R)

wherein f_C is the spatial frequency of the interference fringes recorded on the holograms by said object and reference beams, φ

_C is the inclination of the interference fringes;

f_R is the spatial frequency of the interference fringes formed on the holograms by a hypothetic beam converging at one point on the focusing plane and the reconstructing beam;

Φ

_R is the inclination of the interference fringes;

τ

r_CO is a vector indicative of the position of the object beam source;

τ

r_CR is a vector indicative of the position of the reference beam source;

τ

r_RO is a vector indicative of the position of the hypothetical beam source;

τ

r_RR is a vector indicative of the position of the reconstructed beam source;

(r, θ

) are coordinates on the hologram disk;

φ

is angle of rotation of the hologram disk;

λ

_C is the wavelength of said recording beam; and

λ

_R is the wavelength of said reconstructing and said hypothetical beams;

wherein said hologram disk is a transmission hologram disk;

wherein said reconstructing beam is of a divergent spherical wave; and

wherein the incident angle of said reconstructing beam substantially satisfies the following equation when the angle of rotation of said hologram disk is the angle at which the diffracted beam scans the center of a scanning line;

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

.sub.d =(2.2/r.sub.a +1.7×

10.sup.-3)l.sub.d +22

wherein θ

_d is the diffraction angle at the time the angle of rotation of said hologram disk is the angle at which the diffracted beam scans the center of said scanning line in degrees;

r_a is the distance between the center of rotation of said hologram disk and the position where said reconstructed beam falls on said hologram disk in mm; and

l_d is the distance between said hologram disk and said scanning plane in mm.