English:
[0001]This invention relates to imaging systems, particularly those applied to machine vision systems. In particular it relates to use of color imagers in machine vision systems. More particularly it relates to the use of color imagers to create monochrome images for machine vision processing.
[0002] Traditionally, the market for focal-plane array solid state imagers, referred to in the art by their underlying technologies (i.e. CCDs for Charge Coupled Devices or CMOS for Complimentary Metal Oxide Semiconductor) has been driven by the market for video cameras, of which the CCD or CMOS sensor is a main component. Video cameras, as used for studio broadcast, electronic news gathering (ENG), and consumer camcorders (where the video camera and tape deck or disk drive recorder are integrated into a single compact package) all typically provide a color signal. This signal is typically generated by either of two methods.
[0003] The first method is typically applied to professional grade equipment and in the higher-grade of consumer equipment. For this method the incoming image passes through a video lens, and then passes through a dichroic prism cluster. The dichroic prism cluster is an assembly of three prisms, two of which have a dichroic (color-band selecting) coating. The first prism will have a surface which reflects one color band, typically blue, to a first CCD or similar imager, and passes the remainder of the colors. The second prism will have a surface which reflects a second color band, typically green, to a second CCD or similar imager. A third prism will accept the balance of the signal, in this case the red band, and transmits it to a third CCD or similar imager. If there is a coating on the third prism, it is typically a coating to reject out-of-band light to which the CCD may be sensitive but which is considered undesirable, for example infrared light. This coating to reject infrared (IR) light may alternatively be placed at the front of the prism cluster, or incorporated into a protective window, or incorporated into the lens. Note that in this first method, each of the CCDs or similar sensors are deployed with their full color spectral response intact as the color-separation is accomplished in the dichroic prism cluster. Furthermore each of the sensors acquires image data at its full intrinsic resolution, yielding three full resolution images representing three colors from the scene imaged.
[0004] The second method is typically used in lower grade equipment such as lower cost and/or very compact ENG systems and in most consumer-grade camcorder systems. Here a single CCD or similar imager is used. A color-mosaic filter is integrated with the solid state imager, where by each picture element (pixel) of the imager array is covered by a corresponding color-band filter. Fig 1 shows a diagram of a color-mosaic filter 13 showing exemplary red 12, green 14 and blue 16 color filter elements. Typically, one half of the pixels will be associated with a color-band filter which transmits primarily the green image component, one quarter of the pixels will be associated with a color band filter which transmits primarily the blue image component, and one quarter of the pixels will be associated with a color band filter which transmits primarily the red image component. This type of filter is sometimes referred to as a Bayer filter. This system is biased toward the green spectrum as a deliberate compromise to best satisfy the human observer. Humans are most sensitive to green light and less sensitive to blue and red light. The green component carries the most information regarding human faces to which humans are particularly sensitive. Note that in this method the color-mosaic filter is inseparable from the solid state imager, since the filter is aligned precisely with discreet photosensitive elements in the sensor during the manufacturing process and must remain aligned to perform properly. Fig 2 shows a schematic diagram of a prior art solid state video sensor with attached color- mosaic filter, showing the sensor 20 with attached color-mosaic filter 22, optional IR blocking filter 24, optics assembly 26 and controller 30 attached to sensor by cable 28.
[0005] Secondary industries including machine vision are relatively small users of video sensors and cameras compared to the broadcast, ENG and consumer camcorder industries. As a result manufacturers typically do not manufacture sensors specifically for these secondary markets and therefore these applications must rely on sensors manufactured for other uses. Machine vision applications often require high speed processing, and high sensitivity, high resolution and low cost sensors to be successful. For these reasons, and others, machine vision applications typically use monochrome sensors, where image data from the scene imaged is rendered in shades of grey. To achieve monochrome imaging, machine vision applications sometimes use sensors developed for use in three-channel dichroic prism cluster professional equipment. This yields high speed processing since color information does not need to be processed, high sensitivity since the entire sensor is available to sense broad band illumination and high resolution since all of the picture elements or pixels are used. This is not, however, a low cost solution since these sensors typically cost much more than mass produced color mosaic sensors.
[0007]The sensitivity of solid state imagers to IR is well known. Methods and apparatus for simultaneously imaging visible and infrared have been developed. For instance, US patent # 3,806,633 Multispectral Data Sensor and Display System discusses a dual sensor arrangement with optics to produce an IR image registered with a visible image. US patent # 4,651 ,001 Visible Infrared Imaging Device with Stacked Cell Structure seeks to produce simultaneous visible and IR images using a novel sensor architecture. The ability of solid state sensors to acquire both visible and IR data is exploited by US patent 5,555,464 Red/Near- Infrared Filtering for CCD Cameras, wherein a novel mosaic-color filter is used instead of the standard filter to admit IR light in addition to visible light. These approaches all produce color images in addition to IR images or produce false color images of IR data or IR and visible data combined, all of which tend to work against the machine vision goals of cheap, fast, high resolution processing.
[0008] There are now other major markets for CCD, CMOS and similar sensors, such as digital still cameras and cellular mobile phones that use color sensors of the color- mosaic filter type. These developments have led to the availability of sensors of much reduced cost that might be applied to machine vision systems and thereby reduce the cost of such systems. One system for using these low cost sensors to image IR data is shown in US patent # 7,235,775 Infrared Imaging Apparatus for Processing Emissions in Infrared and Visible Spectrum. The system described therein removes the IR filter from the sensor, replacing it with a filter that passes only IR data. The system then relies on the visible light color-mosaic filter to form separate three peaks in the IR response and thereby form a false color image of three spectral bands in the IR wavelength region. This approach fails to address two of the major problems with using a color-mosaic sensor to acquire IR data. First, the system must process three separate images, which is not an improvement over standard visible processing. Secondly, the three false color images acquired have reduced resolution with respect to the potential resolution of the sensor, since they are spatially multiplexed.
[0010] The invention is a method of and apparatus for simulating panchromatic response from a color-mosaic video sensor. In one embodiment of the instant invention a set of chromatic response curves depicting response of the multi-color video sensor as a function of wavelength is examined, identifying a region of said chromatic response curves where the multi-color video sensor has a substantially uniform response to each wavelength. Fig 3 is a graph 40 showing the spectral response of a typical color-mosaic filter. This graph shows the response in percent quantum efficiency of the blue 42, green 44 and red 36 filters as a function of wavelength. Note the uniform response of all three filters in the IR portion of the spectrum. This wavelength region is in the IR wavelength band, in the wavelengths from about 700 nm to 1000 nm, centered about 850 nm. This wavelength region is typically blocked in commercially available cameras in order to prevent IR radiation from reaching the sensor and unfavorably affecting the image. The instant invention removes this IR filter and optionally replaces it with a filter that blocks visible light and passes IR radiation. In the instant invention, a wavelength or wavelengths are selected from this wavelength region and an imaging scene to be imaged by the multi-color video sensor is illuminated with the selected wavelength(s) within the identified region, thereby acquiring IR data from the sensor related to the imaging scene. A schematic diagram of a system constructed according to the instant invention is shown in Fig 4 showing the sensor 50 with attached color-mosaic filter 52, optional IR pass filter 54, optical assembly 56, cable 58 connecting the sensor 50 to the controller 60 along with the illumination source 62 with its cable 64 operatively connecting the illumination source 62 to the controller 60.
[0011] Fig 1 is a schematic diagram of a prior art image sensor with a mosaic filter
[0012] Fig 2 is a schematic diagram of a prior art color-mosaic solid state camera.
[0013] Fig 3 is a graph showing the spectral response of three colors of a mosaic filter
[0014] Fig 4 is a schematic diagram of a monochrome machine vision system using a color-mosaic sensor
[0015] Fig 1 shows standard Bayer tiling for the color mosaic filter 10 that is aligned with a CCD or CMOS solid state imager. Exemplary red 12, green 14 and blue 16 filter elements are indicated. Proper application of this type of filter to a solid state imaging sensor requires that the each color section of the filter be aligned with a single active picture element in the sensor. This is so that each sensor element or pixel will be exposed to only one filtered color. This requires that the filter be carefully aligned and permanently attached to the sensor. By analysis of the diagram, it is apparent that for an image formed with the aid of a green illuminant the image will be formed with essentially one half of the resolution of the equivalent panchromatic sensor, and for blue or red illuminants the resulting image will be one quarter the resolution of the equivalent panchromatic imager.
[0016] For machine vision, it is common practice to control the illuminator for optimal geometry of the light and for timing of the light (stroboscopic or flash applications). The most practical illuminant for these applications is often light emitting diodes (LEDs) lighting which is typically quasi-monochromatic spanning only a few nanometers in wavelength. Although white LEDs are available in at least two different technologies (tri-stimulus and secondary emission types) neither one is available in the variety of package types and styles of the more established single-color LEDs. Furthermore, even if suitable broadband illumination is available, it is often the form of the object and not the color of the object that is under study, and if color information is present (such as by the use of a color imager and a broad-band illuminant) it may present spurious information that must be computationally filtered out or ignored.
[0017] Fig 2 shows a typical prior art color-mosaic solid state video system including a solid state sensor 20 with attached color-mosaic filter 22. Light enters the system through the optical assembly 26; passes through an optional IR filter 24 to block IR light from reaching the sensor, and then through the color-mosaic filter 22 to the solid state sensor 20. Image data formed by the sensor 20 is transmitted via cable 28 to controller 30 for processing. Most but not all color-mosaic imagers contain an IR filter. The purpose of the IR filter is to filter out extraneous information coming from IR radiation in the scene that would distort the color response of the imager. For most commercial applications, the goal is accurate color fidelity, as opposed to maximum sensitivity or resolution. Since the IR filter does not require permanent precise alignment, it is typically either attached to the outer surface of the sensor 20 on top of the color mosaic filter 22, or included in the optical assembly. Regardless of where it is found in the system it is usually possible to remove the IR filter and replace it with another type of filter if desired.
[0018] Fig 3 is a graph 40 showing the spectral response of a typical color-mosaic filter. This graph shows the response in percent quantum efficiency of the blue 42, green 44 and red 36 filters as a function of wavelength. What can be seen by analysis of this image is that all of the bands have "leakage" in the infrared region. Typically, this leakage is addressed with an optical filter that rejects this "out-of-band" radiation. However, the instant invention exploits this leakage. In a preferred embodiment, an illuminant is chosen at the point of highest and most nearly matched responsivity. This matched responsivity typically occurs between 700 nm and 1000 nm. In one embodiment of the instant invention, illumination at 850nm will result in substantially panchromatic response. It also happens that this color is a common LED type and is readily available in a wide variety of packages and sizes. Such devices are typically based on the semiconductor material Aluminum Gallium Arsenide, which has a band gap that corresponds to emission at or near 850nm.
[0019] Fig 4 shows a system constructed according to the instant invention. An embodiment of this invention uses a commercially available color-mosaic imager 50 or a camera based on the same with color-mosaic filter 52 attached. Near panchromatic response is achieved with said imager or camera by removing the IR-blocking filter and optionally replacing it with a filter 54 that passes IR radiation in the selected wavelengths and blocks visible light. In a preferred embodiment, a quasi- monochromatic illuminator 62 of a particular wavelength range is used, specifically that wavelength range that corresponds to the spectral response of the imager where all three color channels are substantially equal or a subset thereof. In this case the wavelength range is between 700 and 1000 nm. In particular a wavelength of about 850 nm is used. In a preferred embodiment, a quasi-monochromatic illuminator is selected at the relative peak of responsivity within the range where response to all three color channels is substantially equal. The illuminator 62, under control of and connected to a controller 60 via a cable 64 illuminates the scene (not shown) at the appropriate time and with the selected wavelength or wavelengths. The scene is imaged via the optical assembly 56 which comprises a lens or lenses operative to focus IR radiation emitted by illuminator 62 and reflected by scene (not shown) and imaged onto the sensor 50, through the color-mosaic filter 52 and the optional IR pass filter 54. The image data thusly acquired by the sensor 50 is transmitted via cable 58 to controller 60 for further processing.
[0020] In an embodiment of the instant invention, the initial processing involves forming a single monochromatic image from three pseudo-color images transmitted by the sensor to the controller. Note that color information can be encoded in a variety of ways. The simplest is RGB format where three separate images with reduced resolution comparable to their reduced sampling of the sensor area are transmitted. Other encodings such as YUV or NTSC are possible and would work with this method, albeit with possible reduced spatial resolution or dynamic range. This initial processing creates a monochrome image by filling in a 2D array with dimensions same as the original full size sensor with data from the three pseudo color images. The data from the "red", "blue" and "green" images are placed into the monochrome image array according to where the particular pixel was acquired from on the original sensor thereby creating a monochrome image with the same intrinsic resolution as the original sensor. Furthermore, since the scene was illuminated with IR light that is selected to be equally transmitted by all three colors, the sensitivity of the system to light is maximized.
[0021] Another embodiment of this invention further processes the data to remove any variances in response by the color-mosaic sensor to the filtered IR data. It is conceivable that different colors in the color-mosaic filter/sensor combination might respond differently to IR radiation. Since the instant invention depends upon having uniform response from the sensor regardless of the filter, this difference in response can be eliminated by measuring the response over the dynamic range of the sensor with the wavelength of IR light selected and calculating correction factors based on the response. These factors can be additive or multiplicative and are applied to each pixel by the controller depending upon which color filter it was acquired through in order to eliminate or reduce the variance in response between the various colors of the color- mosaic filter.

中文:
[0001]本发明涉及成像系统,特定来说涉及应用于机器视觉系统的成像系统。特定来说,本发明涉及彩色成像器在机器视觉系统中的使用。更特定来说,本发明涉及使用彩色成像器来形成供机器视觉处理的单色图像。
[0002]传统上,此项技术中由其基础技术(即,用于电荷耦合装置的CCD或用于互补金属氧化物半导体的CMOS)指代的焦点平面阵列固态成像器的市场一直以来受以CCD或CMOS传感器作为主要组件的摄像机的市场的推动。通常,用于播音室广播、电子新闻采集(ENG)及消费者摄录机(其中摄像机及走带机构或磁盘驱动记录器集成到单个小型封装中)的摄像机全部提供彩色信号。此信号通常通过两种方法中的任一种产生。
[0003]第一种方法通常应用于专业级装备及较高级消费者装备中。对于此方法,传入图像穿过视频透镜,且接着穿过双色棱镜组。所述双色棱镜组是三个棱镜的组合件,其中的两个棱镜具有双色(色带选择)涂层。第一棱镜将具有将一个色带(通常是蓝色)反射到第一CCD或类似成像器且通过剩余色彩的表面。第二棱镜将具有将第二色带(通常是绿色)反射到第二CCD或类似成像器的表面。第三棱镜将接受信号的平衡(在此情况下是红色色带),且将其透射到第三CCD或类似成像器。如果第三棱镜上存在涂层,那么所述涂层通常是用以拒绝CCD可能对其敏感且被认为是不合需要的带外光(举例来说,红外光)的涂层。用以拒绝红外(IR)光的此涂层可替代地放置于棱镜组的前部处,或并入到保护窗口中或并入到透镜中。注意,在此第一方法中,CCD或类似传感器中的每一者部署为其全色彩光谱响应完好,因为色彩分离是在双色棱镜组中完成。此外,所述传感器中的每一者以其全固有分辨率获取图像数据,从而产生表示来自所成像场景的三种色彩的三个全分辨率图像。
[0004]第二种方法通常用于较低级装备(例如,成本较低的ENG系统及/或极小型ENG系统)中及大多数消费者级摄录机系统中。此处,使用单个CCD或类似成像器。彩色镶嵌滤光器与固态成像器集成在一起,借此通过对应色带滤光器覆盖成像器阵列的每一图片元素(像素)。图1显示彩色镶嵌滤光器13的图示,其显示示范性红色12、绿色14及蓝色16滤色器元件。通常,一半的像素将与主要透射绿色图像分量的色带滤光器相关联,四分之一的像素将与主要透射蓝色图像分量的色带滤光器相关联,且四分之一的像素将与主要透射红色图像分量的色带滤光器相关联。此类型的滤光器有时称作拜耳(Bayer)滤光器。作为有意折中,此系统偏向绿色光谱以最好地满足人类观察者。人类对绿色光最为敏感但对蓝色光及红色光较不敏感。绿色分量携载最多人类对其尤其敏感的关于人脸的信息。注意,在此方法中,彩色镶嵌滤光器与固态成像器不可分离,因为所述滤光器在制造过程期间与传感器中的离散感光元件精确对准,且必须保持对准以适当地履行性能。图2显示附接有彩色镶嵌滤光器的现有技术固态视频传感器的示意图,其显示附接有彩色镶嵌滤光器22的传感器20、任选IR阻挡滤光器24、光学组合件26及通过电缆28附接到传感器的控制器30。
[0005]包含机器视觉的二级产业与广播、ENG及消费者摄录机产业相比是相对小的视频传感器及相机用户。因此,制造商通常不特定针对这些二级市场制造传感器且因此这些应用必须依赖针对其它用途所制造的传感器。机器视觉应用为获得良好结果而常常需要高速处理及高敏感度、高分辨率和低成本传感器。出于这些原因及其它原因,机器视觉应用通常使用单色传感器,其中来自所成像景象的图像数据以灰色阴影渲染。为实现单色成像,机器视觉应用有时使用经开发用于三通道双色棱镜组专业装备中的传感器。此因为不需要处理色彩信息而产生高速处理,因为整个传感器可用于感测宽带照射而产生高敏感度且因为使用所有图片元素或像素而产生高分辨率。然而,此并非是低成本解决方案,因为这些传感器成本通常比大量生产的彩色镶嵌传感器高得多。
[0007]固态成像器对IR的敏感度众所周知。已开发了用于同时进行可见光及红外成像的方法及设备。举例来说,美国专利第3,806,633号多光谱数据传感器及显示系统(Multispectral Data Sensor and Display System)论述了一种具有光学器件的双重传感器布置以产生表现为可见光图像记录的IR图像。美国专利第4,651,001号具有堆叠式单元结构的可见光红外成像装置(Visible Infrared Imaging Device with Stacked CellStructure)试图使用新型传感器架构产生同时的可见光图像与红外图像。美国专利第5,555,464号用于CCD相机的红色光/近红外滤光(Red/Near-Infrared Filtering for CCDCameras)利用固态传感器获取可见光及红外数据的能力,其中使用新型镶嵌滤色器代替标准滤光器以不仅接纳可见光而且接纳IR光。所有这些方法除产生IR图像外还产生彩色图像或产生IR数据或IR数据与可见光数据组合的假彩色图像,所有这些情况均倾向于对机器视觉目标(即廉价、快速、高分辨率处理)产生不利影响。
[0008]CCD、CMOS及类似传感器现在存在其它主要市场,例如使用彩色镶嵌滤光器类型的彩色传感器的数码相机及蜂窝式移动电话。这些开发已导致可应用于机器视觉系统的成本大幅降低的传感器的可用性且由此降低此类系统的成本。美国专利第7,235,775号用于处理红外及可见光谱中的发射的红外成像设备(Infrared ImagingApparatus for Processing Emissions in Infrared and Visible Spectrum)中显示一种使用这些低成本传感器来使IR数据成像的系统。其中所描述的系统从传感器移除IR滤光器,用仅通过IR数据的滤光器代替所述IR滤光器。接着,所述系统依赖可见光彩色镶嵌滤光器来在IR响应中形成单独三个峰且由此形成IR波长区域中的三个光谱带的假彩色图像。此方法不能通过使用彩色镶嵌传感器获取IR数据来解决所述主要问题中的两个问题。首先,所述系统必须处理三个单独图像,此并非是优于标准可见光处理的改进。其次,所获取的三个假彩色图像相对于传感器的潜在分辨率具有降低的分辨率,因为其在空间上被多路复用。
[0010]本发明是一种用于模拟来自彩色镶嵌视频传感器的全色响应的方法及设备。在本发明的一个实施例中,检查描绘多色视频传感器随波长而变的响应的一组色度响应曲线,从而识别所述色度响应曲线的其中多色视频传感器对每一波长具有大致一致的响应的区域。图3是显示典型彩色镶嵌滤光器的光谱响应的曲线图40。此曲线图显示蓝色滤光器42、绿色滤光器44及红色滤光器36的量子效率百分比随波长而变的响应。注意所有三个滤光器在光谱的IR部分中的一致响应。此波长区域是在IR波长带中,在从约700纳米到1000纳米的波长中,中心为约850纳米。在市场上可购得的相机中,此波长区域通常被阻挡以防止IR辐射到达传感器且不利地影响图像。本发明移除此IR滤光器且任选地用阻挡可见光且通过IR辐射的滤光器代替所述IR滤光器。在本发明中,从此波长区域选择一或多个波长且用所识别区域内的选定波长照射将通过多色视频传感器成像的成像场景,由此从与所述成像场景相关的传感器获取IR数据。图4中显示根据本发明构造的系统的示意图,其显示附接有彩色镶嵌滤光器52的传感器50、任选IR通过滤光器54、光学组合件56、将传感器50连接到控制器60的电缆58以及照射源62,照射源62的电缆64操作地将照射源62连接到控制器60。
[0011]图1是具有镶嵌滤光器的现有技术图像传感器的示意图
[0012]图2是现有技术彩色镶嵌固态相机的示意图。
[0013]图3是显示镶嵌滤光器的三种色彩的光谱响应的曲线图
[0014]图4是使用彩色镶嵌传感器的单色机器视觉系统的示意图
[0015]图1显示与CCD或CMOS固态成像器对准的彩色镶嵌滤光器10的标准拜耳色块。其指示示范性红色12、绿色14及蓝色16滤光器元素。将此类型的滤光器适当应用于固态成像传感器需要所述滤光器的每一色彩区段与传感器中的单个有效图片元素对准。此使得每一传感器元素或像素将仅暴露于一种经过滤的色彩。此需要所述滤光器精密地与所述传感器对准并永久附接到所述传感器。通过分析图示,显而易见,对于借助绿色照射体的帮助形成的图像来说,所述图像将以实质上等效多色传感器的二分之一的分辨率形成,且对于蓝色或红色照射体来说,所得图像将是等效多色成像器的分辨率的四分之一。
[0016]对于机器视觉来说,常见做法是控制照射器,以获得光的最优几何图形及光的定时(频闪或闪光应用)。用于这些应用的大多数实际照射体常常是通常是波长仅跨越数纳米的准单色发光二极管(LED)照明设备。虽然白色LED可用于至少两种不同技术(三色及次级发射类型)中,但任一者均不可用于各种封装类型及样式的更多已确立单色LED中。此外,即使合适的宽带照射可用,但情况常常是研究的是对象的形式而不是对象的色彩,且如果呈现色彩信息(例如,通过使用彩色成像器及宽带照射体),那么其可呈现计算时必须过滤掉或忽略的伪信息。
[0017]图2显示包含附接有彩色镶嵌滤光器22的固态传感器20的典型现有技术彩色镶嵌固态视频系统。光经由光学组合件26进入所述系统;穿过任选IR滤光器24以阻挡IR光到达所述传感器,且接着穿过彩色镶嵌滤光器22到达固态传感器20。由传感器20形成的图像数据经由电缆28传输到控制器30供处理。大多数但并非所有彩色镶嵌成像器含有IR滤光器。IR滤光器的目的是在场景中过滤掉来自IR辐射的将使成像器的色彩响应失真的外来信息。对于大多数商业应用来说,目标是准确的色彩保真度,而不是最大敏感度或分辨率。由于IR滤光器并不需要永久精确对准,因此其通常在彩色镶嵌滤光器22的顶部上附接到传感器20的外表面或包含于光学组合件中。不管IR滤光器位于系统中何处,通常可移除所述IR滤光器且视需要用另一类型的滤光器代替所述IR滤光器。
[0018]图3是显示典型彩色镶嵌滤光器的光谱响应的曲线图40。此曲线图显示蓝色滤光器42、绿色滤光器44及红色滤光器36的量子效率百分比随波长而变的响应。通过分析此图像可看出:所有带在红外区域中均具有“泄漏”。通常,借助拒绝此“带外”辐射的光学滤光器来解决此泄漏。然而,本发明利用此泄漏。在优选实施例中,在最高点及最接近匹配的响应度处选择照射体。此匹配的响应度通常出现在700纳米与1000纳米之间。在本发明的一个实施例中,以850纳米照射将导致大致全色响应。还发生以下情况:此色彩是常见LED类型且可容易地用于各种各样的封装及大小中。此类装置通常基于半导体材料砷化铝镓,其具有对应于以850纳米或接近850纳米发射的带隙。
[0019]图4显示根据本发明构造的系统。本发明实施例使用市场上可购得的彩色镶嵌成像器50或基于附接有彩色镶嵌滤光器52的彩色镶嵌成像器50的相机。近全色响应是借助所述成像器或相机通过移除IR阻挡滤光器及任选地用通过选定波长的IR辐射且阻挡可见光的滤光器54代替所述IR阻挡滤光器来实现。在优选实施例中,使用特定波长范围的准单色照射器62,具体来说是对应于其中所有三个色彩通道大致相等的成像器的光谱响应的波长范围或其子集。在此情况下,所述波长范围在700纳米与1000纳米之间。特定来说,使用约850纳米的波长。在优选实施例中,在其中对所有三个色彩通道的响应大致相等的范围内的相对响应度峰值处选择准单色照射器。在控制器60的控制下,经由电缆64连接到控制器60的照射器62在适当时间且借助一或多个选定波长照射场景(未显示)。所述场景经由光学组合件56成像,所述光学组合件56包括一或多个透镜,所述透镜操作以聚焦由照射器62发射且由场景(未显示)反射且成像于传感器50上、穿过彩色镶嵌滤光器52及任选IR通过滤光器54的IR辐射。由传感器50如此获取的图像数据经由电缆58传输到控制器60供进一步处理。
[0020]在本发明的实施例中,初始处理涉及从通过传感器传输到控制器的三个伪彩色图像形成单个单色图像。注意,可以各种方式对色彩信息进行编码。最简单的方式是RGB格式,其中传输与其传感器区的减小取样相比具有减小分辨率的三个单独图像。其它编码(例如,YUV或NTSC)也是可行的且将与此方法一起使用,尽管可能降低空间分辨率或动态范围。此初始处理通过在具有与原始实际大小传感器的相同维度的2D阵列中填充来自三个伪彩色图像的数据来形成单色图像。根据从原始传感器上获取特定像素的位置将来自“红色”、“蓝色”及“绿色”图像的数据放置于单色图像阵列中,由此形成与原始传感器具有相同固有分辨率的单色图像。此外,由于用选定为由所有三种色彩同等透射的IR光照射场景,因此所述系统对光的敏感度最大化。
[0021]本发明的另一实施例进一步处理数据以移除彩色镶嵌传感器对经过滤的IR数据的响应中的任何不一致。可设想,彩色镶嵌滤光器/传感器组合中的不同色彩可对IR辐射产生不同响应。由于本发明取决于具有来自传感器的一致响应而不考虑滤光器,因此响应中的此差异可通过借助选定IR光波长测量传感器的动态范围上的响应且基于所述响应计算校正因数来消除。这些因数可加或可乘且由控制器应用于每一像素,此取决于其是通过哪一滤色器获取的,以消除或减小彩色镶嵌滤光器的各种色彩之间的响应不一致性。