Abstract:
An Infrared Radiation (IR) sensing device comprises a lens module, an IR pass filter, and an optical sensor. The lens module is utilized for focusing light. The IR pass filter comprises an optical coating, and a Color Filter Array (CFA) module. The optical coating is utilized for blocking light with wavelength around a predetermined range. The CFA module is utilized for blocking light with wavelength around 400 nm to 780 nm. The optical sensor for absorbing photons of light after being blocked by the IR pass filter on the optical path and accordingly generating an electrical signal. With the help of the CFAs, the range of the wavelength that the optical coating has to block becomes smaller, which greatly reduces the required number of layers of the optical coating.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/161,077, filed on Mar. 18, 2009 and entitled “Infrared pass filter” the contents of which are incorporated herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an Infrared Radiation (IR) sensing device, and more particularly, to an IR sensing device by means of overlaying one or more Color Filter Arrays (CFA) along with the optical coating for passing IR and filtering non-IR out. 
     2. Description of the Prior Art 
     IR sensing devices based on silicon technology typically require the use of a non-infrared blocking element somewhere in the optical chain for only responding IR. The purpose of this element is to prevent non-infrared radiation (IR) or light (typically considered to be light with a wavelength longer than 780 nm) from entering the optical sensors of the optical sensing devices. Silicon-based optical sensors, e.g. Charge Coupled Device (CCD) sensor or a Complementary Metal-Oxide-Semiconductor (CMOS) sensor, will typically be sensitive to light with wavelengths up to approximately 1000 nm. If the non-IR (visible light) is permitted to enter the optical sensor, the IR sensing device will respond to the non-IR, and generate an output signal. Since the purpose of the IR sensing device is to create a representation of IR present in a scene, the non-IR will introduce a false response. 
     A common method for preventing these difficulties is to use a thin-film optical coating on glass to create an optical element which blocks visible light (typically from 400 nm to 780 nm) and passes the IR. However, to block light with such wide range (400 nm to 780 nm), the number of the layers of the optical coating is larger, e.g. 45. Since the number of the layers of the optical coating has to be so large to achieve the capability of filtering out the non-IR, which deteriorates the malleability and the flexibility of the optical coating, the optical coating can not be coated on the lens nor the optical sensor consequently. Therefore, the conventional IR sensing device realized with the optical coating comes with high cost and difficulty for production, which is inconvenient. 
     SUMMARY OF THE INVENTION 
     The present invention provides an Infrared Radiation (IR) sensing device. An optical path exists for an ambient light to enter the IR sensing device. The IR sensing device comprises a lens module, an IR pass filter, and an optical sensor. The lens module is disposed on the optical path. The lens module is utilized for focusing light on the optical path. The IR pass filter comprises an optical coating, and a Color Filter Array (CFA) module. The optical coating is disposed on the optical path. The optical coating is utilized for blocking light with wavelength around a predetermined range. The CFA module is disposed on the optical path. The CFA module is utilized for blocking light with wavelength around 400 nm to 780 nm. The optical sensor for absorbing photons of light after being blocked by the IR pass filter on the optical path and accordingly generating an electrical signal. 
     The present invention further provides a two-band pass sensing device. An optical path exists for an ambient light to enter the two-band pass sensing device. The two-band pass sensing device comprises a lens module, a two band-pass filter, and an optical sensor. The lens module is disposed on the optical path for focusing light on the optical path. The two band-pass filter comprises a CFA module. The CFA module is disposed on the optical path. The CFA module comprises a blue CFA and a green CFA. The blue CFA is utilized for passing blue light. The green CFA is utilized for passing green light. The optical sensor is utilized for absorbing photons of light after being blocked by the IR pass filter on the optical path and accordingly generating an electrical signal. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an IR sensing device according to a first embodiment of the present invention. 
         FIG. 2(   a ) is a diagram illustrating the transmittance spectrums respectively of the optical coating with a first setting, the red and the blue CFAs of the present invention. 
         FIG. 2(   b ) is a diagram illustrating the resulting transmittance spectrum of the IR pass filter of the present invention from  FIG. 2(   a ). 
         FIG. 3(   a ) is a diagram illustrating the transmittance spectrums respectively of the optical coating with a second setting, the red and the blue CFAs of the present invention. 
         FIG. 3(   b ) is a diagram illustrating the resulting transmittance spectrum of the IR pass filter of the present invention from  FIG. 3(   a ). 
         FIG. 4  is a diagram illustrating an IR sensing device according to a second embodiment of the present invention. 
         FIG. 5(   a ) is a diagram illustrating the transmittance spectrums respectively of the optical coating with the first setting, the red, the blue, and the green CFAs of the present invention. 
         FIG. 5(   b ) is a diagram illustrating the resulting transmittance spectrum of the IR pass filter of the present invention from  FIG. 5(   a ). 
         FIG. 6(   a ) is a diagram illustrating the transmittance spectrums respectively of the optical coating with the second setting, the red, the blue, and the green CFAs of the present invention. 
         FIG. 6(   b ) is a diagram illustrating the resulting transmittance spectrum of the IR pass filter of the present invention from  FIG. 6(   a ). 
         FIG. 7  is a diagram illustrating the structure view of the IR sensing device according to a third embodiment of the present invention. 
         FIG. 8  is a diagram illustrating the structure view of the IR sensing device according to a fourth embodiment of the present invention. 
         FIG. 9  is a diagram illustrating the structure view of the IR sensing device according to a fifth embodiment of the present invention. 
         FIG. 10  is a diagram illustrating the structure view of the IR sensing device according to a sixth embodiment of the present invention. 
         FIG. 11  is a diagram illustrating the structure view of the IR sensing device according to a seventh embodiment of the present invention. 
         FIG. 12  is a diagram illustrating a two-band pass sensing device of the present invention. 
         FIG. 13(   a ) is a diagram illustrating the transmittance spectrums respectively of the blue and the green CFAs of the two-band pass filter of the two-band pass sensing device of the present invention. 
         FIG. 13(   b ) is a diagram illustrating the resulting transmittance spectrum of the two-band pass filter of the two-band pass sensing device of the present invention from  FIG. 13(   a ). 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 1 .  FIG. 1  is a diagram illustrating an IR sensing device  100  according to a first embodiment of the present invention. The IR sensing device  100  comprises an IR pass filter  110 , an optical sensor  120 , and a lens module  130 . An optical path exists on the IR sensing device  100  for allowing an ambient light L A  to enter the optical sensor  120 . 
     The lens module  130 , disposed on the optical path, provides a focused light L F  out of an ambient light L A  from a scene. That is, the lens module  130  focuses the ambient light L A  to be the focused light L F . The optical sensor  120 , disposed on the optical path, may comprise a photo diode, where photons absorbed by the photo diode generate an electrical signal S, either a voltage or current signal, indicative of the number of photons absorbed by the photo diode. 
     The IR pass filter  110 , disposed on the optical path, comprises an optical coating  111 , and a CFA module  112 . The CFA module  112  comprises a red and a blue CFAs  112 R and  112 B. The red CFA  112 R mainly blocks light with the wavelength around 400 nm to 570 nm, and the blue CFA  112 B mainly blocks light with the wavelength around 520 nm to 780 nm. 
     The optical coating  111 , disposed on the optical path, is formed by interlacingly stacking/overlaying N high refractive index layers NDH 1 ˜NDH N  (for example, TiO 2 ) and M low refractive index layers NDL 1 ˜NDL M  (for example, MgF 2  or SiO 2 ), wherein M and N represent integer around 3, respectively (in  FIG. 1 , N is determined to be equal to (M+1) for example). By means of the interference effect, the transmittance spectrum of the optical coating  111  is set according to the thicknesses, the materials, or the number of the high index layers NDH 1 ˜NDH N  and the low refractive index layers NDL 1 ˜NDL M  and can be adjusted by above-mentioned factors. Since the light with the wavelengths 400 nm to 570 nm and 520 nm to 780 nm are respectively blocked by the red CFA  112 R and the blue CFA  112 B, the optical coating  111  has only to block light with the wavelength around 900 nm to 1000 nm, which is a much smaller range, and consequently the number of the layers of the optical coating  111  can be greatly reduced, for example, can be reduced to 7. 
     Please refer to  FIG. 2 .  FIG. 2(   a ) is a diagram illustrating the transmittance spectrums T 111     —     1 , T 112R , and T 112B  respectively of the optical coating  111  with a first setting, the red CFA  112 R, and the blue CFA  112 B of the present invention.  FIG. 2(   b ) is a diagram illustrating the resulting transmittance spectrum T 110     —     1  of the IR pass filter  110  of the present invention from  FIG. 2(   a ). As shown in  FIG. 2(   a ), in the sensitive range for the optical sensor  120 , the red CFA  112 R is only transparent to red light and IR; the blue CFA  112 B is only transparent to blue light and IR. In the infrared range, the optical coating  111  has a low transmittance (opaque) around the wavelength from 900 nm to 1000 nm. By combining the transmittance spectrums T 111     —     1 , T 112R , and T 112B , the transmittance spectrum T 110     —     1  of the IR pass filter  110  is obtained. As shown in  FIG. 2(   b ), the IR pass filter  110  is only transparent from 780 nm to 900 nm between the sensitive range for the optical sensor  120 . Therefore, the IR sensing device  100  senses the light emitted from a Light-Emitting Diode (LED) of 850 nm type. 
     Please refer to  FIG. 3 .  FIG. 3(   a ) is a diagram illustrating the transmittance spectrums T 111     —     2 , T 112R , T 112B  respectively of the optical coating  111  with a second setting, the red CFA  112 R, and the blue CFA  112 B of the present invention.  FIG. 3(   b ) is a diagram illustrating the resulting transmittance spectrum T 110     —     2  of the IR pass filter  110  of the present invention from  FIG. 3(   a ). The transmittance spectrum T 111     —     2  is different from of the transmittance spectrum T 111     —     1  by means of changing the thicknesses, the materials, or the number of the high index layers NDH 1 ˜NDH N  and the low refractive index layers NDL 1 ˜NDL M . Therefore, in  FIG. 3(   a ), the optical coating  111  with the second setting has a low transmittance (opaque) around the wavelength from 750 nm to 880 nm in the infrared range. By combining the transmittance spectrums T 111     —     2 , T 112R , and T 112B , another transmittance spectrum T 110     —     2  of the IR pass filter  110  is obtained. As shown in  FIG. 3(   b ), the IR pass filter  110  is only transparent around from 900 nm to 1000 nm between the sensitive range for the optical sensor  120 . Therefore, the IR sensing device  100  senses the light emitted from an LED of 940 nm type. 
     Since the number of the layers of the red CFA  112 R and the blue CFA  112 B are 2, and the number of the layers of the optical coating  111  is around 7, the number of the overall layers of the IR pass filter  110  is greatly reduced. Furthermore, the CFA module  112  is easily integrated with the optical sensor  120 , which reduces cost for the IR sensing device  200  of the present invention. 
     Please refer to  FIG. 4 .  FIG. 4  is a diagram illustrating an IR sensing device  400  according to a second embodiment of the present invention. The IR light sensing device  400  comprises an IR pass filter  410 , an optical sensor  120 , and a lens module  130 . The IR pass filter  410  comprises an optical coating  111 , and a CFA module  412 . The CFA module  412  comprises a red CFA  112 R, a blue CFA  112 B, and a green CFA  112 G. The green CFA  112 G mainly blocks light with the wavelength around 400 nm to 475 nm, and the wavelength around 600 nm to 780 nm. 
     Please refer to  FIG. 5 .  FIG. 5(   a ) is a diagram illustrating the transmittance spectrums T 111     —     1 , T 112R , T 112B , and T 112G  respectively of the optical coating  111  with the first setting, the red CFA  112 R, the blue CFA  112 B, and the green CFA  112 G of the present invention.  FIG. 5(   b ) is a diagram illustrating the resulting transmittance spectrum T 410     —     1  of the IR pass filter  410  of the present invention from  FIG. 5(   a ). In the sensitive range for the optical sensor  120 , the red CFA  112 R is only transparent to red light and IR; the blue CFA  112 B is only transparent to blue light and IR; the green CFA  112 G is only transparent to green light and IR. In the infrared range, the optical coating  111  with the first setting has a low transmittance (opaque) with a wavelength from 900 nm to 1000 nm. By combining the transmittance spectrums T 111     —     1 , T 112R , T 112B , and T 112G , the transmittance spectrum T 410     —     1  of the IR pass filter  410  is obtained. As shown in  FIG. 5(   b ), the IR pass filter  410  is only transparent from 780 nm to 900 nm between the sensitive range for the optical sensor  120 . Therefore, the IR sensing device  400  senses the light emitted from an LED of 850 nm type. 
     Please refer to  FIG. 6 .  FIG. 6(   a ) is a diagram illustrating the transmittance spectrums T 111     —     2 , T 112R , T 112B , and T 112G  respectively of the optical coating  111  with the second setting, the red CFA  112 R, the blue CFA  112 B, and the green CFA  112 G of the present invention.  FIG. 6(   b ) is a diagram illustrating the resulting transmittance spectrum T 410     —     2  of the IR pass filter  410  of the present invention from  FIG. 6(   a ). The transmittance spectrum T 111     —     2  has a low transmittance with a wavelength from 750 nm to 880 nm in the infrared range. By combining the transmittance spectrums T 111     —     2 , T 112R , T 112B , and T 112G , the transmittance spectrum T 410     —     2  of the IR pass filter  410  is obtained. As shown in  FIG. 6(   b ), the IR pass filter  410  is only transparent around from 900 nm to 1000 nm between the sensitive range for the optical sensor  120 . Therefore, the IR sensing device  400  senses the light emitted from an LED of 940 nm type. 
     Please refer to  FIG. 7 .  FIG. 7  is a diagram illustrating the structure view of the IR sensing device  700  according to a third embodiment of the present invention. The IR sensing device  700  may be realized with the IR sensing devices  100  or  400 . As shown in  FIG. 7 , the CFA module  712 , the optical coating  711 , and the optical sensor  720  can be integrated as an Integrated Chip (IC). More particularly, in the IC, the CFA module  712  is coated on the optical sensor  720 , and the optical coating  711  is coated on the CFA module  712 . The lens module  730  is disposed on the upside of the optical coating  711  of the IC. 
     Please refer to  FIG. 8 .  FIG. 8  is a diagram illustrating the structure view of the IR sensing device  800  according to a fourth embodiment of the present invention. The IR sensing device  800  may be realized with the IR sensing devices  100  or  400 . Comparing with  FIG. 7 , in  FIG. 8 , the CFA module  812  and the optical sensor  820  can be integrated as an IC. However, the optical coating  811  is coated on the downside of the lens module  830 . The lens module  830  and the optical coating  811  are disposed on the upside of the CFA module  812  of the IC. 
     Please refer to  FIG. 9 .  FIG. 9  is a diagram illustrating the structure view of the IR sensing device  900  according to a fifth embodiment of the present invention. The IR sensing device  900  may be realized with the IR sensing devices  100  or  400 . As shown in  FIG. 9 , the CFA module  912 , the optical coating  911 , and the optical sensor  920  can be integrated as an Integrated Chip (IC), and the package type of the IC can be Chip On Board (COB) or Chip Scale Package (CSP). In a preferred embodiment, the package type of the IC is CSP, and the CSP comprises supports  940  and a glass  950 . More particularly, in the IC of the CSP type, the CFA module  912  is coated on the optical sensor  920 , and the optical coating  911  is coated on the downside of the glass  950 , wherein the downside faces the optical sensor  920 . The lens module  930  is disposed on the upside of the glass  950  of the IC of the CSP type, wherein the upside faces the lens module  930 . Furthermore, the glass  950  is coupled to the optical sensor  920  through the supports  940 . 
     Please refer to  FIG. 10 .  FIG. 10  is a diagram illustrating the structure view of the IR sensing device  1000  according to a sixth embodiment of the present invention. The IR sensing device  1000  may be realized with the IR sensing devices  100  or  400 . As shown in  FIG. 10 , the CFA module  1012 , the optical coating  1011 , and the optical sensor  1020  can be integrated as an Integrated Chip (IC), and the package type of the IC can be Chip On Board (COB) or Chip Scale Package (CSP). In a preferred embodiment, the package type of the IC is CSP, and the CSP comprises supports  1040  and a glass  1050 . More particularly, in the IC of the CSP type, the optical coating  1011  is coated on the optical sensor  1020  and the CFA module  1012  is coated on the optical coating  1011 . The lens module  1030  is disposed on the upside of the glass  1050  of the IC of the CSP type, wherein the upside faces the lens module  1030 . Furthermore, the glass  1050  is coupled to the optical sensor  1020  through the supports  1040 . 
     Please refer to  FIG. 11 .  FIG. 11  is a diagram illustrating the structure view of the IR sensing device  1100  according to a seventh embodiment of the present invention. The IR sensing device  1100  may be realized with the IR sensing devices  100  or  400 . As shown in  FIG. 11 , the CFA module  1112  and the optical sensor  1120  can be integrated as an Integrated Chip (IC), and the package type of the IC can be Chip On Board (COB) or Chip Scale Package (CSP). In a preferred embodiment, the package type of the IC is CSP, and the CSP comprises supports  1140  and a glass  1150 . More particularly, in the IC of the CSP type, the CFA module  1012  is coated on the optical sensor  1020 . The optical coating  1111  is coated on the downside of the lens module  1130 , which faces the glass  1150  of the IC of the CSP type. The lens module  1010  is disposed on the upside of the glass  1150  of the IC of the CSP type. Furthermore, the glass  1150  is coupled to the optical sensor  1120  through the supports  1140 . 
     Please refer to  FIG. 12 .  FIG. 12  is a diagram illustrating a two-band pass sensing device  1200  of the present invention. The structures and the operational principles of the two-band pass sensing device  1200  is similar to the IR sensing devices  100  or  400  and will not be repeated again for brevity. The difference is that the two-band pass filter  1210  comprises a blue CFA  112 B and a green CFA  112 G. 
     Please refer to  FIG. 13 .  FIG. 13(   a ) is a diagram illustrating the transmittance spectrums T 112B , and T 112G  respectively of the blue CFA  112 B, and the green CFA  112 G of the two-band pass filter  1210  of the two-band pass sensing device  1200  of the present invention.  FIG. 13(   b ) is a diagram illustrating the resulting transmittance spectrum T 1210     —     1  of the two-band pass filter  1210  of the two-band pass sensing device  1200  of the present invention from  FIG. 13(   a ) the green CFA  112 G is only transparent to green light and IR, and the blue CFA  112 B is only transparent to blue light and IR. However, combining the transmittance spectrums T 112B  and T 112G , the two-band pass filter  1210  is not only transparent to IR (800 nm to 1000 nm), but also a little transparent to the light with the wavelength around 500 nm, as shown in  FIG. 13 . Therefore, by means of the two-band pass filter  1210 , the two-band pass sensing device  1200  not only senses the IR, but also senses the light with the wavelength around 500 nm. 
     To sum up, the present invention mainly provides an IR sensing device with the IR pass filter realized with both CFAs and the optical coating. With the help of the CFAs, the range of the wavelength that the optical coating has to block becomes smaller, which greatly reduces the required number of layers of the optical coating. Since the number of the layers of the CFAs is smaller, and the number of the layers of the optical coating becomes small, the number of the overall layers of the IR pass filter of the IR sensing device of the present invention can be greatly reduced. Furthermore, the CFAs are easily integrated with the optical sensor, which reduces cost for the IR sensing device of the present invention. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.