Image sensor and method of manufacturing the same

• US 6,374,024 B1
• Filed: 09/22/1999
• Issued: 04/16/2002
• Est. Priority Date: 10/30/1998
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Iijima, Ryuta
• Primary Examiner(s): Mack, Ricky
• Application Number:
  US09/400,973
• Time in Patent Office: 937 Days
• Field of Search: 385/115, 385/116, 385/119, 385/120, 385/146, 385/33, 385/34, 385/35
• US Class Current: 385/116
• CPC Class Codes: G02B 3/0012 characterised by the manufacturing method
• CPC Class Codes: G02B 3/0018 Reflow, i.e. characterized by the step of melting microstructures to form curved surfaces, e.g. manufacturing of moulds and surfaces for transfer etching
• CPC Class Codes: G02B 3/0056 arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085
• CPC Class Codes: G02B 3/0087 with index gradient
• CPC Class Codes: G02B 6/06 the relative position of the fibres being the same at both ends, e.g. for transporting images
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262
• CPC Class Codes: G02B 6/4249 comprising arrays of active devices and fibres
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14678 Contact-type imagers
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H01L 31/02322 comprising luminescent members, e.g. fluorescent sheets upon the device
• CPC Class Codes: H04N 1/0311 using an array of elements to project the scanned image elements onto the photodetectors H04N1/0318 takes precedence
• CPC Class Codes: H04N 1/0312 using an array of optical fibres or rod-lenses
• CPC Class Codes: H04N 1/0315 using photodetectors and illumination means mounted on separate supports or substrates or mounted in different planes
• CPC Class Codes: H04N 2201/02493 Additional optical elements not otherwise provided for, e.g. filters, polarising plates, masks or apertures

Abstract

An image sensor that is more compact than a contact type image sensor using a rod-lens array and has a depth of field of the same level as a contraction type image sensor using a set of mirrors. The sensor includes an array of a specified pixel-corresponding quantity of micro-lenses arranged for forming an image light reflected from an original document, an array of the specified pixel-corresponding quantity of optical fibers arranged for transmitting an image formed by the micro-lens array as respective optical signals of pixels and an array of light-receiving elements for converting optical signals incident thereon from the optical fiber array into electric signals, wherein the optical fiber array has core-end-faces each having a size smaller than that of an image formed by the micro-lenses and located on the micro-lens-side position from the image forming plane when the original document is placed at a specified base position.

Claims

1. An image sensor comprising,

an array of a specified quantity of pixel-corresponding micro-lenses arranged for forming an image of light reflected from an original document,

an array of the specified quantity of pixel-corresponding optical fibers or waveguides arranged for transmitting the image formed by the micro-lens array as respective optical signals, and

an array of light-receiving elements for receiving optical signals from the optical fiber array or the optical waveguide array and converting the optical signals into electric signals, wherein the optical fiber or waveguide array has core-end-faces each having a size smaller than that of an image formed by the micro-lenses and being located on the micro-lens-side from the image forming plane when the original document is placed at a given position.

7. A method of manufacturing an image sensor defined in claim 1 or 2, comprising steps of:

putting a transparent substrate on an end-face of the optical fiber array or the optical waveguide array, applying an ultraviolet-curing resin-layer on the substrate, forming thereon cylindrical islands each having a diameter corresponding to a region of divergent angle of the optical fibers or the optical waveguides by ultraviolet radiation from a reverse-side end-faces and forming spherical lens surfaces of the islands by thermal reflowing and simultaneously adjusting a thickness of the transparent substrate to a value at which each micro-lens being shaped to the effective region of diverging light of each optical fiber or each optical waveguide can have a diameter smaller than that of a pixel.

8. A method of manufacturing an image sensor defined in claim 1 or 2, comprising steps of:

putting a transparent substrate on an end-face of the optical fiber array or the optical waveguide array, applying a photosensitive resin-layer on the substrate, forming thereon swellings each having a diameter corresponding to a region of divergent angle of the optical fibers or the optical waveguides by ultraviolet radiation from the reverse-side end-faces and forming spherical lens surfaces of the swellings by allowing unreacted monomer to move therein and simultaneously adjusting a thickness of the transparent substrate to a value at which each micro-lens being shaped to the effective region of diverging light of each optical fiber or each optical waveguide can have a diameter smaller than that of a pixel.

2. An image sensor comprising an array of a specified quantity of pixel-corresponding micro-lenses arranged for forming an image of light reflected form an original document,

an array of the specified quantity of pixel-corresponding optical fibers arranged for transmitting an image formed by the micro-lens array as respective optical signals and

an array of light-receiving elements for receiving optical signals from the optical fiber array and converting the optical signals into electric signals, wherein the optical fiber array has the optical fibers arranged parallel to each other therein.

3. An image sensor as defined in claim 2, wherein the optical fibers each composed of a core and clad are arranged in an array and fixed to a jig with adhesive containing nontransparent material having a refractive index higher than that of the clad and are further provided with a light shielding film covering all input-side end-faces excluding core-end-faces.

4. An image sensor as defined in claim 2, wherein the optical fibers each composed of a core and clad whose refractive index is, at its inside, lower than that of the core and gradually increases toward its outside surface are arranged in an array and then fixed to a jig with adhesive containing nontransparent material having a refractive index higher than that of the outside surface of the clad.

5. An image sensor as defined in claim 2, wherein the optical fibers each having a three-layer structure composed of a core, a clad and an absorbing layer, with a refractive index of the clad lower than that of the core and lower than that of the absorbing layer, are arranged in an array and fixed to a jig with adhesive containing nontransparent material.

6. An image sensor as defined in claim 3, wherein the jig with optical fibers fixed thereto has a thermal expansion coefficient substantially equal to that of the light-receiving elements to be coupled therewith.