Image sensor having integrated infrared-filtering optical device and related method
a technology of infrared filtering and image sensor, which is applied in the field of imaging systems, can solve the problems of color capture quality virtually impossible without a blocking filter for these wavelengths, corrupted output levels, and relatively expensive colored glass, and is approximately 20 times more expensive than clear glass
Inactive Publication Date: 2008-06-05
APTINA IMAGING CORP
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Benefits of technology
This approach ensures effective filtration of infrared light regardless of the angle of incidence, prevents color shifts, and reduces system size and cost by integrating the IR filter with the microlens structure, thereby enhancing manufacturing efficiency and image quality.
Problems solved by technology
Quality color capture without a blocking filter for these wavelengths is virtually impossible because the IR typically swamps the sensor performance and thereby corrupts the output levels.
Similarly monochrome capture relies on preserving the luminance in the sensed visible light, which is difficult without IR filtering.
Such colored glass is relatively expensive, approximately 20 times more expensive than clear glass.
One problem with this approach, however, is that the thin film coating is usually optimized for particular wavelengths and for light rays normal to the thin film surface.
Therefore, the infrared light rays near the edges of the pixel array, which usually exit the field lens at an angle, are less effectively filtered.
This may cause a visual artifact at the edges of the image known as a color discontinuity.
In some cases, image processing can be used to remove the color shift, but at added cost and complexity.
While effort has been made to provide IR and UV blocking without sacrificing the image integrity or adding excessive cost and complexity to the image sensing optics, the approaches thus far fall short in one or more respects.
Mounting of the filter in the case chamber may result in dust and other contaminants lodging on the sensor pixels and obstructing the image rays.
The separate selective IR and / or UV filter element 25 adds an additional component to the total system count, i.e., piece-part count, and adds to the complexity and manufacturing cost of the imaging system.
Further, depending on where the selective filter 25 is placed, there may be an increase in the system size that diversely affects cost of performance.
The resulting dust and particles from these operations may contaminate the camera sensor and block active sensor pixels.
But as discussed above, a problem with the above-described imaging system is that the IR filter element 25 may increase the size and part count, and thus the cost, of the system, and may introduce contamination that reduces the performance of the system.
Method used
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[0024]One embodiment of the invention is to use a dye that absorbs light energy of a wavelength lying outside the visible spectrum, such as IR, and mixing such dye into a plastic that is then formed into an optical structure disposed on the sensor. Absorptive dye often performs better than a thin film coating because filtration of the unwanted light typically occurs regardless of the angle of incidence of incoming light, and also because the IR absorption by the dye typically does not cause a color shift around the edges of the image. In a particular embodiment of the invention as disclosed herein the IR absorptive material is mixed in with a polymer resin. During a heated fluid state, the mixture is formed into the sensor microlens. The microlens structure made of dye and polymer resin overlies the photosensing sites and both filters out unwanted wavelengths, such as IR, and focuses the desired visible light onto the sites. By providing the selective filtration and lens focus with ...
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An image sensing device is disclosed having a die formed with an array of photosensing sites and a structure of optical material having infrared absorbing characteristics formed over the photosensing sites. An embodiment is disclosed in which the structure of optical material having infrared absorbing characteristics is formed as an array of microlenses for directing visible image light onto the photosensing sites and at the same time filtering out infrared wavelengths that interfere with image capture. Alternatively, the structure may be designed to filter out other ranges of wavelengths outside of the visible spectrum.
Description
CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a Divisional of U.S. application Ser. No. 10 / 926,152 filed Aug. 24, 2004.FIELD OF THE INVENTION[0002]The invention relates to imaging systems and more particularly to filtering of selected wavelengths, such as infrared energy, from light imaged onto sensor devices in an integrated electrical optical device.BACKGROUND OF THE INVENTION[0003]Image sensing devices that capture monochrome or color images by changes in the electrical properties of photo-sensing pixels on integrated circuit dies or chips have provided an alternative to traditional film technology. Known types of the sensors include field effect transistor (FET) or diode devices, fabricated with complementary metal oxide semiconductor (CMOS) or charge couple device (CCD) technology.[0004]CMOS and CCD image sensors each have advantages and disadvantages. CMOS technology offers ease of interfacing with other CMOS based hardware and can reduce power drain on port...
Claims
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IPC IPC(8): H01L31/0232H04N25/00
CPCH01L27/14618H01L27/14625H04N5/2257H01L27/14645H01L31/02162H01L27/14627H01L2224/48091H04N23/57H01L2924/00014
InventorMA, GUOLINHARTLOVE, JASON
OwnerAPTINA IMAGING CORP