Method for forming a computer generated hologram

• US 5,119,214 A
• Filed: 03/26/1991
• Issued: 06/02/1992
• Est. Priority Date: 03/26/1990
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Fukui, Atsushi, Kawamura, Hiroyuki, Nishii, Kanji, Itoh, Masami
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/675,526
• Time in Patent Office: 434 Days
• Field of Search: 350/3.62, 350/3.64, 350/3.66, 350/3.74, 350/348, 350/162.12, 350/162.13
• US Class Current: 359/7
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G03H 1/02 Details of features involved during the holographic process; Replication of holograms without interference recording
• CPC Class Codes: G03H 1/08 Synthesising holograms, i.e. holograms synthesized from objects or objects from hologramsusing electric digital computers G06F; G06T
• CPC Class Codes: G03H 1/2294 Addressing the hologram to an active spatial light modulator
• CPC Class Codes: G03H 2001/0224 Active addressable light modulator, i.e. Spatial Light Modulator [SLM]
• CPC Class Codes: G03H 2001/0858 Cell encoding wherein each computed values is represented by at least two pixels of the modulator, e.g. detour phase coding
• CPC Class Codes: G03H 2225/22 Electrically addressed SLM [EA-SLM]
• CPC Class Codes: G03H 2225/31 Amplitude only
• CPC Class Codes: G03H 2225/34 Amplitude and phase coupled modulation

Abstract

New methods for producing computer generated holograms to be used for a liquid crystal spacial light modulator having a plurality of pixels, wherein the amplitude component of a coherent wave disturbance is corrected by taking into account the phase distortion due to the twist of liquid crystal molecules of the liquid crystal spacial light modulator.

Claims

1. A method for producing a computer generated hologram to be used for a liquid crystal spatial light modulator having a plurality of pixels to be controlled to open completely or to close completely, wherein a cell being composed of a plurality of pixels is a unit for displaying the amplitude component and the phase component of a coherent wave disturbance, and a cell may have an aperture composed of pixels adjacent to each other to express the amplitude and phase components, said amplitude component for a cell being expressed by the area of the aperture, said phase component being expressed by the distance of the aperture from the center of the cell, comprising the steps of:

(a) calculating the amplitude component and the phase component for each cell;

(b) adding the phase distortion component to said phase component by using experimental data of phase distortion of a pixel; and

(c) determining the center of the aperture in each cell according to the result of said adding step and the area of the aperture according to said amplitude component.

2. A computer generated hologram to be used for a liquid crystal spatial light modulator having a plurality of pixels to be controlled to change the transmittance of liquid crystal layer to express gradation, wherein a cell being composed of a linear array of pixels is a unit for displaying the amplitude component and the phase component of a coherent wave disturbance, said phase component being expressed as the position of a pixel assigned to the phase in said linear array of pixels, said amplitude component in correspondence with said phase component being expressed as the amount of transmitted light in said pixel assigned to the phase, comprising the steps of:

(a) calculating the amplitude component and the phase component in a cell;

(b) estimating the phase distortion in each cell according to the amplitude component data obtained in the calculating step by using experimental data of phase distortion of a pixel; and

(c) correcting the amplitude component and the phase component by adding the phase distortion to the phase component.