Sensor surface with 3D curvature formed by electronics on a continuous 2D flexible substrate

#The current application is related to U.S. patent application Ser. No. 11/644,082 filed Dec. 22, 2006, entitled “Flexible Segmented Image Sensor” which was filed on the same day with the same assignee.

#Image sensors have largely replaced film in imaging systems. Typical image sensors, such as charge coupled device (CCD) arrays and CMOS imagers are typically based on crystalline silicon substrates and are thus almost perfectly flat. However, flat image sensors can only handle light coming in from a narrow field of view. In order to widen the field of view, complicated, delicate and expensive lens systems are used to focus the light from a wider area onto the flat sensor. However, such lenses add weight and add significantly to imaging system expense.

#Forming a curved image sensor has long been proposed as a means of creating wide angle imaging systems using relatively simple and light lens systems, because the focal plane of a simple light lens system generally forms a spherical section. Curved image sensors have other applications, including robotic sensor systems. However, forming a curved sensor has proven to be logistically difficult. Many semiconductor processes, such as photolithographic processes, are not easily adapted to implementation on a curved surface. In addition, when excessive stress is applied to crystalline sensor structures, sensor cracking may result.

#FIG. 1 shows a lens focusing light on a curved plane light detector.

#FIG. 2 shows a hemispherical sensor formed from hemispherical segments formed in a plane.

#FIG. 3 shows a series of hemispherical segments formed in a plane.

#A method of fabricating a curved image sensor is described. In one embodiment of fabrication, a flexible sensor structure, such as an amorphous silicon image sensor, is fabricated on a flexible substrate in a two dimensional plane. The formation is typically done monolithically meaning that both the active elements (detectors) and the interconnect lines that relate to the sensor are formed on a single substrate. The outer perimeter of the sensor pixel array is designed such that a spiral pattern or other hemisphere segment is formed. The image sensor is then cut along the outline pattern and the substrate including the image sensor is bent or flexed into an approximate curved shape such as a hemisphere. As used herein, “hemisphere” and “hemispherical” are broadly defined as an approximately symmetrical curved concave object which may be, but is not necessarily, a portion of a sphere.

#FIG. 1 shows use of a curved focal plane light image sensor 104 in an imaging system. Light rays 108 from a wide area passes through lens 112. Lens 112 is designed to have a curved focal plane. A curved image sensor 104 is placed such that a curved light detecting surface of the sensor coincides with the curved focal plane of lens 112. For wide angle images, curved focal plane lenses such as lens 112, are easier to fabricate then traditional wide angle lenses. Various methods will be described to form the curved focal plane image sensor 104.

#FIG. 2 shows a hemisphere shaped sensor 204 that is formed from a pixel array sensor 308 shown in FIG. 3. As used herein, a “detector” or “photodetector” is broadly defined as a device that converts visible, infra-red or ultraviolet light into an electrical signal. As used herein, a “sensor” or “image sensor” is broadly defined to be a device that is made up of an array of photo-detectors and the interconnect lines that connect the photo-detectors in order to create an image.