CN1310915A - Color imaging system with infrared correction - Google Patents

Abstract

An imaging system using a color shutter that receives color information with infrared information in multiple planes and a signal representing only infrared radiation. The infrared radiation signal can be subtracted from the signal associated with the color planes to obtain a signal free of infrared radiation effects for each desired color plane. In addition, infrared signals can be obtained which may have beneficial applications in some cases. In this way, the color band of the color information can be obtained without the use of an infrared filter, and if desired, the infrared information can be saved for further use. In addition, infrared and dark current information can be obtained for dark current correction.

Description

Color imaging system with infrared correction

For example the present invention relates generally to the imaging system used together with digital camera, scanner and analog.

Imaging sensor based on silicon technology uses a kind of infrared shading element usually in light path.The effect of infrared shading element is to prevent that infrared radiation (IR) or light (being commonly considered as the light of wavelength greater than 780 nanometers) from entering imaging array.

Be about the only sensitive of 1200 nanometers for the wavelength maximum in normal circumstances based on the device of silicon.If allow infrared radiation (IR) to enter imaging array, imaging array will respond IR, and produce an output image signal.A because purpose of imaging system is the image that produces the expression visible light, so the image fault that IR introduces the response of a falseness and imaging system is produced.In monochromatic (black and white) imaging system, this possibility of result shows as an image that obvious distortion is arranged.For example, the tone of leaf and people's skin may be bright singularly.In color imaging system, the introducing of IR makes cross-color, produces the true image that is off color.

Prevent in the imaging system that unusual universal method based on IR is to use the ion stained glass or in film light coating on glass producing a kind of optical element, this optical element can block IR by visible light (generally from 380 nanometers to 780 nanometers).This optical element can be placed on lens combination the place ahead, be positioned in the lens combination or this optical element can be combined in the whole imaging system.The major defect of this method is cost height and the complexity that has increased system.The cost of implementing film coating may be lower slightly, but its additional shortcoming is that spectral shift is the function of angle.So in an imaging system, these elements can not provide the even light transmission features from each inconocenter to the edge.These two kinds of filter types because to increase by one extra but must be assembled into parts in the imaging system, and strengthened the complexity of system.

Digital imaging system is so-called dark current of recoverable all in general.Dark current does not detect when receiving any input picture actually by imaging system.In general, dark current or in the calibration process period interval of camera from deduction, or when camera is operated, isolate and deduction.Can use mechanical shutter between each frame, to block optical system, so that the continuous indication of dark current noise to be provided.This may be useful, because dark current is with the temperature strong variations.Therefore, wish to have the continuous indication of dark current existence.The another kind of method of determining continuously dark current provides some pixel that masks light, thereby the indication of continuous dark current state can be provided.

So it is that people need that the imaging system that reduces complexity and cost is provided always.Especially need the photaesthesia in the visible spectrum, insensitive but do not need a kind of imaging system of infrared filter to the light in the infrared spectrum.Further, need a kind of can the continuous correction dark current and the two the system of influence of infrared noise.

According to one embodiment of the present of invention, a kind of imaging system comprises a shutter, and this shutter selectively is adjusted in first state, to pass through the radiation in the visible spectrum.This shutter can block light in the visible spectrum basically at second state, but can pass through infrared radiation.Subtracter can make the signal subtraction of the radiation that first and second states that are illustrated in pass through.

Brief description of drawings

Fig. 1 represents the light transmission features of traditional red, green, blue CFA filter.

Fig. 2 represents to comprise the light transmission features of a kind of IR pass filter of red and blue CFA filter.

Fig. 3 is the simplification profile with pixel loop that is deposited on the red and blue CFA filter on the pixel loop.

Fig. 4 is a senior loop of simplification that is used for the IR signal of image signal correction.

Fig. 5-7 expression is used for the rectangular patterns of color sensor array.

Fig. 8 represents to be used for the rectangular patterns of monochromatic sensor array.

Fig. 9 is to use the schematic diagram of the camera of color shutter.

Figure 10 is the calcspar that expression forms the parts in infrared deduction loop as shown in Figure 9.

Figure 11 is a flow chart, and expression for example uses hardware as shown in Figures 9 and 10 to derive process infrared and three primary colors information.

In an embodiment of the present invention, the signal that the method deduction IR element sensor by electricity consumption the signal that produces from the two element sensor of response IR and visible light produces has reduced the influence of IR to picture signal basically.The IR element sensor is comprising that for penetrating the IR on the array of transducer is responsive, and this provides the IR component of the image that separates with color channel (such as RGB).

Use available chromatic filter array (CFA) material on the current market, and radiation is the transparent fact for IR to get it, can produce the IR transducer.Color (as red, indigo plant) by two CFA that superpose simply, they do not have overlapping light transmission basically on the visible light section of spectrum, just can produce a composite filter element, this composite filter element can block visible light basically, can only see through IR.If use two filters to form this composite filter element, and the visible radiation passband spectrum that each filter in these two filters all has the visible radiation passband spectrum with another filter to separate, like this, basically, without any the final composite filter that be combined to form of visible light transmissive by two filters.If the filter that uses outnumber 2, and each filter all has a visible radiation passband spectrum, therefore, final composite filter is opaque for visible light basically.So a kind of like this composite filter is exactly a kind of IR pass filter, all be transparent basically for IR because form each filter-divider of composite filter.

As an example, what Fig. 1 represented is conventional red, green, blue CFA (being added with the acrylate of dyestuff) filter.Be noted that each filter all is transparent for IR basically.The light transmission of the compound IR band pass filter that expression obtains by the red and blue CFA filter that superposes in Fig. 2, as can be seen from Figure 2: hidden visible spectrum basically.

Use the pixel of IR filter generation IR sensitivity, or the IR element sensor, its method is each component filter of deposit, constitutes the IR band pass filter on a pixel loop.This deposit can be by to semi-conductor industry being well-known photoetching technique realization.But the pixel loop is any one loop of the signal of absorbed radiation and the radiation that the representative absorption is provided.For example, the pixel loop can comprise a photodiode, and the photon that photodiode absorbs produces electron-hole pair, and it provides the signal of telecommunication, voltage signal or the current signal of the number of photons of represent the photodiode absorption with adjunct circuit.

In one embodiment, Fig. 3 represents the simplification profile of an IR element sensor 300, and said element sensor 300 comprises pixel loop 310, is deposited with red CFA320 and blue CFA330 on pixel loop 310.The photon of the visible-range of incident on the pixel loop is schematically illustrated by direction 340, is blocked entirely basically or prevents to be absorbed by pixel loop 310.

What embodiment used is the imaging array with 4 types of element sensors: 3 kinds of colour (as RGB) types and a kind of IR type, all these element sensors of 4 types are made by available CFA material on market entirely.This has just produced 4 passages, and 4 types signal is as shown in table 1 in other words, table 1 expression be the spectrum that records for each passage or type of pixel.

The spectrum output channel spectrum channel 1 red+IR passage 2 green+IR passage 3 indigo plants+IR passages 4 of 1:4 output channel of table have IR

In case know the IR component of picture signal, just can from image, deduct this IR component, to provide the colour output of proofreading and correct through IR.This level circuit by Fig. 4 is represented, wherein by multiplexer (MUX) 410 and subtraction circuit 420; Each signal from the passage 1-3 deducts the IR signal on the passage 4.Obviously, if utilize 3 subtraction circuits to finish the IR signal deduction of each color channel, just can save MUX410.

Express the possible rectangular patterns of coloured image in Fig. 5-7, Fig. 8 represents the rectangular patterns of monochrome image, and wherein W represents the element sensor to whole visible-light spectrum sensitive.Can think that each pattern of expression all is a unit among Fig. 5-8.Mode with rule in whole imaging array repeats these unit.

In Fig. 5-7, the element sensor that is designated as R, G, B represents to utilize respectively the element sensor of red, green, blue CFA filter.In Fig. 5-8, the element sensor that is designated as IR (R+B) is the IR element sensor, and the compound pass filter of IR wherein comprises red and blue CFA filter.

Element sensor does not need actual mutual physics contact.In general the pixel loop that constitutes element sensor is to isolate with other pixel loop is electric mutually.Said first element sensor and second element sensor are adjacency, be understood to be in and only do not have any one element sensor placed in the middle between first and second pixels.For example, in Fig. 7, the upper left element sensor R and the element sensor G of bottom left, top element sensor G and element sensor B are adjacency, but and the element sensor G and the IR element sensor of bottom right be not adjacency.Two element sensors can be adjacency not carrying out under the condition that actual physics is in contact with one another.

Owing in the imaging len system, have aberration, so the IR component of the scenery of imaging can not be in accurately on the focus.This is actually helpful for embodiment disclosed herein, because this shows, needn't sample for the IR component with high spatial frequency.This situation is reflected in respectively in the rectangular patterns of Fig. 7 and 8 expressions for coloured image and monochrome image.

Can use by the second way to have the IR element sensor, no matter monochromatic or colored, imaging array, make it to become an IR imaging array, only utilize the signal that comes from the IR element sensor to form the IR image here.Thereby the imaging array of making according to embodiment disclosed herein can be configured to double mode imaging array, and the visible images of proofreading and correct through IR perhaps is provided, and the IR image perhaps is provided.

Can constitute the embodiment of system, for example blue or green, pinkish red and yellow (CMY) system and pinkish red, white, yellow (MWY) system with other color.For the CMY color system, may must superpose 3 kinds of all colors to block visible light.This processing method can also be generalized to the MWY color system, but need carry out additional treatments, increases the third color (as blue or pinkish red).Can require this color to finish to block to detect visible light in the pixel at IR.

Digital imaging system 910 shown in Figure 9 can be used together with a digital camera, and digital camera can provide video pictures static and that move.In addition, imaging system 910 also can be used in during other that use digital type image sensor use, as scanner etc.

Be provided with a liquid crystal color shutter 912 in the place ahead of lens combination 914 and imageing sensor 916.Imageing sensor 916 can be the image sensor of a kind of CMOS (Complementary Metal Oxide Semiconductor) (CMOS), and it uses a CMOS active pixel sensor (APS), a passive pixel sensor (PPS) or other technologies.Alternatively, can also use charge-coupled device (CCD).

Color shutter 912 is in different colored frequency ranges, as red, green, blue (RGB) and green grass or young crops, magenta, yellow (CMY) three primary colors frequency range, electric changeable emission spectrum can be provided, a typical color shutter KALA filter, can be from the state of Colorado ColorLink company of 80301 Boulder obtain.Shutter 912 synchronously switches with the frequency range in each expectation continuously provides color information.The KALA filter switches between a primary subtractive colour (CMY) that adds a primary colors (RGB) and a complementation.The complementary color that the white light conversion of input has been polarized with being orthogonal.

Color shutter can switch between a plurality of emission optical frequenciess, and these frequency ranges are aligned on the every bit on multilayer additive color plane, as red, green, blue primary colors plane.Color shutter can the order switching, so that the plane of three colors to be provided, the trichromatic specification of an image is set up in its combination.

In PS, use color shutter can allow each element sensor sequentially the frequency range of three colors to be reacted beneficially.Otherwise the element sensor that separates must scatter in array for the frequency range of each needed color.Then, the information that is lost in each pixel is derived out by interpolation technique with two color planes that stay.Utilize color shutter, each pixel can detect each frequency range in 3 colored frequency ranges, can increase colored definition without interpolation.

Imageing sensor 916 is coupled to image processor 918, and image processor 918 is handled the information from imageing sensor 916, and the output of expectation form is provided.Image processor 918 comprises an infrared subtraction circuit 920.Circuit 920 utilizes a subtractive process that the infrared component of each the colored frequency band signals that provides synchronously from color shutter 912 is provided.Specifically, color shutter 912 provides a series of light images in the color plane of each expectation, and the pixel in these image stimulus sensors 916 provides the strength signal that passes to image processor 918.

This subtractive process also can be used software implementation.For example, this subtraction can be finished in an independent computer (not shown).Can be with this computer link to camera.

With reference to accompanying drawing 10, the information separated of autobiography sensor 916 becomes 4 signals in the future.The strength signal that transducer 916 provides comprises each colored frequency band signals of an infrared component.In the example that uses the colored frequency range of RGB, produce danger signal 1024, green 1026, blue signal 1028, each signal all has relevant infrared component.In addition, shutter 912 produces a black signal 1030, and black signal 1030 is substantially free of any colour information, only contains infrared radiation information.

So, can in subtracter 1032, deduct black signal 1030 (only comprising the information that appears at the relevant infrared radiation on the shutter 12) from each signal 1024 to 1028, produce signal 1034-1038 without any infrared component.Can obtain infrared component on online 1040.This infrared component can be used under a series of half-light conditions, comprises the application of camera at night, scouting action and three-dimensional imaging.

In this way, under the condition of not using infrared filter, can produce the color plane of the expectation that does not have the infrared radiation noise.And, utilize technology of the present invention, can obtain infrared signal useful in a series of application.When using infrared filter, can not get useful infrared signal.

With reference to accompanying drawing 11, the process of capturing colour information in image processor 918 starts from square 1144.During beginning, color shutter 912 is arranged to black, obtains a picture (shown in square 1146) so that infrared reference signal to be provided.Subsequent, shutter is arranged to redness (shown in square 1148), and obtains a picture, comprising red information and infrared component (shown in square 1150).Similarly, obtain green and blue information, shown in square 1152 to 1158.

In square 1160,1162,1164, from the infrared reference signal that the red, green, blue look picture deduction that obtains square 1150,1154,1158 obtains at square 1146, derivation red, green, blue look plane.As a result, can export the RGB color plane information that (shown in square 1166) wherein do not contain infrared component.

Above-described embodiment also is useful to dark current compensation.Each embodiment is substantially free of generation the two colored wave band of benchmark IR radiation effect and dark current.IR reference signal 1146 (not having under the situation of colour information) includes only dark current noise.So, when having deducted IR reference signal or black picture, just can eliminate fully IR and dark current noise the two.This elimination and IR noise removing are finished simultaneously, wherein do not need the pixel of mechanical shutter or screen.Because dark current deducted continuously, so Current Temperatures is always taken into account the influence of dark current.

Though described the present invention with reference to a limited number of embodiment, the common technique personnel of this area can realize many improvement and variation.We are contemplated to be appending claims and will cover all this improvement and variations that drop in true spirit of the present invention and the scope.

Claims (14)

1. An imaging system comprising: a first sensor for producing a first output representative of incident infrared radiation and the absence of incident visible radiation; a second sensor for producing a second output representative of incident radiation comprising both the visible and infrared spectra; and and a subtractor arranged to subtract said first and second outputs. 2. The imaging system of claim 1, wherein said subtractor continuously subtracts said first and second outputs. 3. The system of claim 1, including a pair of filters having substantially non-overlapping visible light transmissivity to form the first output substantially free of visible light. 4. The method of claim 1, including a liquid crystal color shutter for forming the first output substantially free of visible light information. 5. The imaging system of claim 1, including a subtractor, said subtractor subtracting signals representative of passing radiation in said first and second states. 6. The system of claim 5, wherein said shutter is a liquid crystal color shutter. 7. The system of claim 6, comprising an image sensor, said image sensor receiving light information from the shutter in a multilayer color plane, said system further comprising an image processor, said An image processor is connected to said image sensor for processing information received from the image sensor. 8. The system of claim 7, wherein said image sensor provides signals representative of at least three color planes and infrared radiation to which the color shutter exposes. 9. An imaging method, comprising: producing a first output representative of the incident infrared radiation and the absence of incident visible light; generating a second output representative of incident radiation comprising both the visible and infrared spectra; and subtracting said first and second outputs. 10. The imaging method of claim 9, wherein said first and second outputs are continuously subtracted. 11. The method of claim 9 wherein said first output is formed using a pair of filters with substantially non-overlapping visible light transmissivity. 12. The method of claim 10, wherein said first output is formed using a liquid crystal color shutter. 13. The method of claim 11, comprising filtering each color plane in turn. 14. The method of claim 9, characterized by producing an output corrected for infrared and dark current noise.

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