MXPA00008657A - Plant chlorophyll content imager - Google Patents

Abstract

A portable plant chlorophyll imaging system is described which collects light reflected from a target plant and separates the collected light into two different wavelength bands. These wavelength bands, or channels, are described as having center wavelengths of 700 nm and 840 nm. The light collected in these two channels is processed using synchronized video cameras (142, 144, 146). A controller (200) provided in the system compares the level of light of video images reflected from a target plant with a reference level of light from a source illuminating the plant. The percent of reflection in the two separate wavelength bands from a target plant are compared to provide a ratio video image which indicates a relative level of plant chlorophyll content and physiological stress. Multiple display modes (300, 302) are described for viewing the video images.

Description

IMAGE FORMOR OF PLANT CHLOROPHYLL CONTENT TECHNICAL FIELD OF THE INVENTION The present invention relates in general to the detection of the chlorophyll content of plants and, in particular, the present invention relates to a device that visually forms images of the chlorophyll content in a plant using light reflectance.

BACKGROUND OF THE INVENTION The early detection of physiological stress in vegetables is beneficial for the environmental and agricultural business community. Plant stresses can result from numerous influences, including, but not limited to, drought, chemicals such as herbicides or biological influences. Early detection can provide the opportunity to reverse physiological stress or at least identify what tension is present.

When there are unfavorable plant growth conditions, physiological stress, the chlorophyll content of the leaves typically begins to decrease. Consequently, the methods for detecting the chlorophyll content of the leaves provide a measure or indication of a level of said tension.

Different aspects for the detection of tension in plants measuring the chlorophyll of the leaves are available. One of these techniques that can be used is fluorescence. In the case of fluorescence, the incident light is absorbed by the pigments in the sheet. Not all the absorbed light energy is transferred chemically that will be used in photosynthesis, rather, some of this absorbed energy is re-emitted, or is fluoresced, by chlorophyll at wavelengths far from red, or almost red. The maximum chlorophyll fluorescence occurs at wavelengths near 690 and 730 nanometers. For this reason, fluorometers usually measure fluorescence with narrow bands centered near 690 or 730 nanometers. In general, the fluorescence in these bands tends to increase with the reduced chlorophyll content or the increased degree of physiological tension. To measure the far red or near infrared fluorescence, the leaf is irradiated only with light of much shorter wavelengths (for example, blue or green light). This ensures that any far infrared or near infrared light emanating from the leaf is actually fluorescence and not merely incident light that has been reflected by the leaf. A second method to measure the chlorophyll content of plants is through the use of transmittance. This technique transmits light through a leaf of a white plant. A percentage of the light transmitted through the sheet is measured at specific wavelengths. These wavelengths are typically 650 nanometers and 940 nanometers. As the chlorophyll content changes, the ratio of transmittance to these wavelengths changes. A clear defect to verify the chlorophyll content of plants using this method is the requirement of physical contact with a plant leaf. Another aspect to detect the physiological tension of the plants by measuring the chlorophyll of the leaves is achieved by verifying the incident light reflection. The reflectance of incident radiation from the inside of the leaf increases as the chlorophyll of the plant is reduced, providing an optical indicator of tension. A reflectance sensitivity analysis has shown that increased reflectance in specific wavebands provides an earlier and more consistent indication of voltage than reflectance at other wavelengths as a result of the chlorophyll absorption properties. Depending on the severity of the stress, this reflectance response can be detected before symptoms of damage appear at first sight. It has been shown that reflectance detects a reduced chlorophyll content at least 16 days before visual indications such as changes in leaf color. Typically, reflectance measurements are made while the leaf of the plant is exposed to a spectrum incident entirely from the sun, or an artificial light source. Although some fluorescent energy must also be measured in combination with the reflected light, the fluorescent energy is small compared to a higher intensity of the reflected light.

In addition, physical contact with the white plant is not required. Different techniques for conducting reflectance measurements are known to indicate plant tension. However, these techniques require extensive field measurements combined with laboratory analysis of the collected measurements. For the reasons set forth above, and for other reasons presented below, which will be apparent to those skilled in the art after reading and understanding the present specification, there is a need in the art for a portable video imager to detect the Chlorophyll levels of plants to provide an indication of physiological stress in plants based on incident light reflectance.

COMPENDIUM OF THE INVENTION The aforementioned problems with the detection of plant stress and other problems addressed by the present invention will be understood by reading and studying the following specification. A portable video imager is described, which uses reflected light from a white plant area at two wavelengths of light to detect the chlorophyll content and provide an indication of the plant voltage. An image forming system of the chlorophyll content in one embodiment is described. The image forming system comprises an optical system that provides at least two video output signals. A first video signal is filtered to have a first central transmission wavelength, and a second video signal is filtered to have a second central transmission wavelength. The image forming system includes first and second light detectors for detecting a light source and providing first and second reference signals, and a controller for receiving the first and second video output signals and providing an output video signal indicating the relative chlorophyll content of white vegetables. The controller provides an image of the percentage of light reflected from the target plant by comparing the first and second video signals produced from the reflected light from the target plant against the outputs of the first and second reference signals. In another embodiment, a portable light reflectance video system for use in imaging the chlorophyll content of plants comprises an optical lens for collecting reflected light from a white plant under test, and an optical light splitter for divide the light collected by the optical lens into first and second light beams. A first optical bandpass filter is provided to receive the first light beam of the optical light splitter and provide a first light output having a central wavelength of about 700 nanometers. A first video camera provides a first video signal in response to the first light output having a central wavelength of approximately 700 nanometers. A second optical bandpass filter receives the second light beam from the optical light splitter and provides a light output having a center length of about 840 nanometers. A second camera • 5 video providing a second video signal in response to the second light output having a central wavelength of approximately 840 nm. First and second light detectors are included to detect a light source and provide first and second reference signals. The system includes a processor to provide an output video signal indicating the levels of • Chlorophyll content of the plants as a proportion of the percentage of reflected light having a central wavelength of about 700 nanometers to the percentage of reflected light having a central wavelength of about 840 nanometers Finally, a visual display is provided to the user with a video image of the white plant to identify the chlorophyll content. In yet another embodiment, a method is provided to view the chlorophyll content of the plants to identify the stress early plant using a chlorophyll content imager. The method comprises the steps of detecting light from a light source having a first wavelength, detecting light from the light source having a second wavelength and providing a first image of video of light reflected from a white plant having a first wavelength. A second video image of the light reflected from the white plant having the second wavelength is provided. The method also includes the steps of providing a third video image of a first reflected percentage of light reflected from the target plant having the first wavelength from the detected light of the light source having the first wavelength, and providing a fourth video image of a second reflected percentage of the reflected light of the white plant having the second wavelength of the detected light of the light source having the second wavelength. A fifth video image is provided and is displayed visually as a proportion of the third video image to the fourth video image using the chlorophyll content imager.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram of a portable video imager of the present invention using light reflectance; Figure 2 illustrates an image forming system of Figure 1; and Figure 3 is a block diagram of the processing system of Figure 1.

DETAILED DESCRIPTION OF THE INVENTION In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part thereof, and which are shown by way of specific preferred embodiments of illustration in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it should be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the present invention. Therefore, the following detailed description should not be taken as a limiting sense, and the scope of the present invention is defined only by the appended claims. Referring to Figure 1, a modality of a portable video imager system of the present invention for detecting chlorophyll levels is described. The video image forming system processes the reflected light from the plants in two different wavelength bands and compares the amount of light from these two bands to provide a video image of a white plant area. The system compares the level of light reflected from a white plant in the two bands with a reference level of light in the two bands from a source that illuminates the plant. The system provides a video output indicating the levels of the chlorophyll content, as an indication of the level of relative tension of the pineapple. The detection system is preferably modalized as a portable unit, so that it can be used by an operator in the field for real-time analysis of the condition of the plants. The video image forming system includes a multi-spectrum, three-channel optical system, 100, which collects light from a white area. The optical system of multiple spectra includes a first light filter, which has a wavelength on the scale of 840 +. 5 nanometers, to pass light through a video camera. The multiple spectrum system also includes a second light filter having a wavelength on the scale of 695 + 5 nanometers, to pass light through a second video camera. Finally, a third image is provided which is through a third camera. The third image is not filtered. The outputs 102, 104 and 106 of the cameras are provided to the processor 200, which provides a variety of video outputs to the monitors 300 or 302. The processor includes an algorithm processor 110, an image combiner 112 and an image multiplexer 114. The present invention provides various modes of visual display, which are described herein. The system is implemented using the RS-170 video standard. the RS-170 format is not a requirement to produce the PSD signal described below. However, if RS-170 is not used in the input signal, a circuit system could be added to produce the RS-170 format for visual display of the image on RS-170 or NTSC format monitors. If a computer system is used to digitize the PSD signal and produce the visual display modes, then an additional circuit system is not required. If the entire system is converted to a digital implementation, the algorithm for calculating the plant voltage ratio remains the same, as the algorithms used to create visual display presentations. The RS-170 implementation was chosen for the availability of low-cost cameras and monitors. Three video cameras are configured in the multi-spectrum optical system 100 to obtain three spatially co-registered images with appropriate optical bandpass filters installed. Referring to Figure 2, a detailed description of one embodiment of the multiple spectral image forming system 100 is presented. The multiple spectral image forming system 100 is illustrated to generate a plurality of co-registered images. The system 100 employs first, second and third CCD video cameras 142, 144 and 146, each of which detects an image of an object, and generates an electrical representation thereof. Although the use of CCD video cameras is preferred, it will of course be understood that any other type of two-dimensional imaging device or detector can be employed. The system 100 includes a primary lens assembly having a focusing lens 120. The focusing lens 120 focuses an input image light beam, thereby forming a real image of the object. The primary lens assembly is connected to a collimation lens 122, which again expands or collimates the image of the projected object into a collimated image light beam • which is directed towards a light splitter assembly. The light splitter assembly includes first and second light dividers 124 and 126 for dividing the collimated image light beam into first, second, third and fourth image light beams. The first image light beam is a version of the image light beam that is transmitted through the first light divider to the camera 142. The second beam of image light is reflected from the • first light splitter 124 at a 90 ° angle. The third image light beam is reflected from the second light divider 126 as an inverted aversion of the second image light beam, and thus is a doubly reflected version of the collimated image light beam original 29. The third image is transmitted to the image 144. The fourth image light beam is the portion of the second image light beam, which is transmitted through the second light divider 126. A mirror beam 128 reflects the fourth beam of image light at an angle of 90 °, thus generating a fifth beam of image light that, also reflected twice, is of the same orientation as the original collimated image light beam. The folding mirror 128 in this way is necessary to restore the image of the object to its correct orientation, since the second and fourth beams of image light constitute versions once reflected and therefore inverted image light beam of the object.

First, second and third lens tubes 130, 132 and 134 are provided to direct the first, third and fifth image light beams, respectively, to the CCD cameras 142, 144 and 146 • corresponding. The length of each of the tubes is selected to provide the total length of the path of the image light beam that is necessary to provide co-registered images of the object in each of the cameras. Arranged along the image directed to the cameras 142 and 144 are first and second filters 138 and 139, respectively. Each filter provides a selective filtering of wavelength of the • received images. Filters are bandpass filters that pass only a single wavelength or a small scale of wavelengths. It should be noted that the filters can be located anywhere along the trajectories of the first and third image light beams. The filter 138 is preferably a filter of 700 + 5 nanometers, and the filter 140 preferably is a filter of 840 + 5 nanometers. Although a typical light divider transmits a percentage of a • input light beam equal to the percentage of the light beam reflected in a ratio of 50/50, other proportions may also be employed. In addition, although the light dividers are generally independent of the wavelength, a dichroic mirror can also be employed in the light dividers 124 and 126, which are of specific wavelength for reflectance and transmittance. From In this way, with a dichroic mirror, the entire first wavelength scale can be transmitted, while the entire second scale of different wavelengths can be reflected so that no energy is lost in the process of dividing the wavelength. light for the specific wave band. The use of dichroic mirrors, therefore, can serve the same purpose as filters 138 and 140. To provide plant stress analysis images, the first filter 138 is selected as a narrow bandpass filter, which only light of a wavelength of 700 nanometers passes into the CCD array in the first chamber 142. As previously discussed, light at 700 nanometers is absorbed through the chlorophyll in the plant. Since plant stress usually results in a reduction in chlorophyll production, a variation in plant uptake, and thus reflectance of light of wavelength of 700 nanometers is often an indicator of stress in the plant. plant. Nevertheless, the amount of light reflected at this wavelength will also vary in response to various environmental conditions, such as the ambient light intensity. In this way, a reference wavelength must also be formed in images, which is not sensitive to the production of chlorophyll in the plant. In this case, an infrared wavelength, such as 840 nanometers, can be used as a reference, and in this way, the second filter 140 is selected to make the narrow bandpass filter, which passes only light from a wavelength of 840 nanometers towards the CCD array in the second chamber 144. Finally, the third camera 146 provides a visible image, which can be covered with the images generated by the first and second cameras to facilitate the visual observation of the measurements of plant tension. The image signals generated by each of the cameras goes to a suitable image processing system, which performs the necessary comparison of the production of chlorophyll sensitive to the image generated by the first camera and the reference image generated by the second. camera, and generates a visual indication of the plant voltage, which is covered with the visual spectrum image generated by the third camera. It should be understood that the multiple spectrum system 100 ensures automatic co-registration of the three images and reduces the amount of data processing that must be done to correlate each pixel of each image. Referring to Figure 3, a more detailed description of the processor 200 is provided. A synchronization generator RS-170, 160 is coupled to the video cameras 142, 144 and 146 to provide synchronization signals, which produce temporally co-operative images. -registered in camera outputs 150, 152 and 154. The video signals of RS-170 format of the three cameras are sent to a DC 162 restoration system, where all the video signals are referenced to 0 volts and are extracts a new synchronization signal (synchronization output). The synchronization output signal is used in the synchronization insert circuit 186 for the visual display of the calculated PSD (Plant Voltage Detection) signal 190. The synchronization output signal is also coupled to RGB to the NTSC 236 encoder , and is provided as an output to the RGB synchronization monitor 300. The three signals are output from the restore circuit DC 162 and are directed to the algorithm processor 110 (V700, V840 and VPAN). The outputs are coupled to outputs 02, 03, 04 and 06 for visual display on a RG300 monitor or NTSC 302 color monitor through multiplexer circuits ON / OFF of PSD 230-234. The visual display mode is used to only align the system. That is, the optical system of multiple spectra is aligned, while the three images are viewed simultaneously on a monitor. The signal 168, which corresponds to the video camera filtered at 700 nanometers, and the signal 166, which corresponds to the video camera filtered at 800 40 nanometers, are sent to the PSD 110 processor. The Analogue Processor PSD performs the algorithm of voltage detection of the plant. The output signals of the two discrete silicon photodiode detectors 170 and 172 are used as light references. The detectors are covered by one of the optical band filters used in the video cameras. That is, the detector 170 provides a centered reference at 700 nanometers, and the detector 172 provides a centered reference at 840 nanometers (R700 and R840). The filters are covered by diffused ground glass providing an unfocused wide field of view. The reference sensors are placed so that they can see the entire sky (approximately), while the video signals are being processed. The signals from the output of the photodiodes are sent to the PSD 110 processor. The processor calculates the percentage of reflectance in each pass band and then takes the proportion of the two reflectance percentages to produce the plant voltage ratio. Referring to Figure 3, the signal 168 (V700) is divided by the reference output of the detector 170 (R700) to produce the output 178 of the divider circuit 174. The output, P700, is the percentage of the reflected light of 700 nanometers. The output 166 (V840) is divided between the reference output (R840) of the detector 172 to produce the output 180 of the divider circuit 176. The output, P840, is the percentage of the reflected light of 840 nanometers. The output signal 178 is divided into the signal 180 to produce the plant voltage ratio (PSD) signal as an output of the divider circuit 182. This signal indicates a relative chlorophyll level by calculating the percentage ratio of the reflected light of 700 nanometers to the percentage of reflected light of 840 nanometers. The proportion of the reflectance percentage for the two video wavelengths varies from approximately .1 for a healthy plant to .4 and more for a diseased plant. It will be understood that these proportions may vary for different plant species. As such, a ratio below .2 usually indicates a healthy plant, while a ratio above .25 usually indicates a diseased plant. The signal PSD is coupled to a variable level circuit 184 to adjust a deviation of the signal. The PSD signal is also coupled to a synchronization insert / amplifier / regulator 186 to direct the output on the output connection 01 to direct the display or digitization. The PSD signal is also sent to the visual display processor circuit system, where it is used to create four different display modes. The visual display circuit system 112 produces four different presentations of the PSD signal. These results can be color-switched to monochromatic via color / mono switch 252 to control multiplexing circuits 224-228. When selected is monochromatic aspect, the input 2 of the multiplex circuits is coupled to the respective outputs. When the color is activated, the input 1 is coupled to the outputs of the multiplexing circuit and the visual display color can be switched between red or green with the red / green switch 254 which controls the switching circuit 222. In this way, green is provided when the multiplexing circuit 226 is coupled to the multiplexing circuit 220. Also, red is provided when the multiplexing circuit 228 is coupled to the multiplexing circuit 220. The four different video display modes are described below . The first mode is a PSD modulator mode, illustrated by the circuit 210. This mode multiplies the PSD signal 190 by the unfiltered video panorama signal 164. The resulting output signal is sent to the input 1 of the multiplex circuit. 218. The video panorama signal 164 is sent to the input 1 of the multiplexing circuit 220. In this way, when the input 1 is selected from the multiplexing circuits 218 and 220, the output of the multiplexing circuits 218 and 220 they are coupled through the output processor 114 as selected. 10 A second video viewing option is a PSD mode • illustrated in the logic block 212. This mode simply outputs the PSD signal 190 of both the multiplexing circuits 218 and 220 through the inputs 2. The output is equal in all colors, thus producing a scale image in gray for vision. A third video vision option is referred to as a PSD + V panorama and is illustrated in block 214. This mode simply couples the PSD signal 190 to the input 3 of the circuit • multiplexing 218 and coupling the video panorama signal 164 to the entry 3 of multiplexing circuit 220. The final video vision option is a PSD threshold mode. This mode provides several output options as such. The PSD signal is sent to a threshold detector circuit 216 (comparator). A threshold voltage is set through a potentiometer 217. Each Once the PSD signal 190 exceeds the set threshold voltage, the comparator switches 2: 1 to multiplexer 219 between 0 volts and either signal PSD 190 or pan signal 164, whichever is selected. This output is sent to the input 4 of the multiplexing circuit 220. The input 4 to the multiplexing circuit 218 can • 5 be either the PSD signal 190 or the pan signal 164. In this manner, the threshold detector circuit compares the PSD signal with a predetermined voltage to identify the regions of the PSD video signal, which exceed a level identified voltage, such as .25. In PSD color mode, the image above the threshold will appear as red or bright green (saturated). The rest of the • image will be at a gray level of either the PSD signal or the video panorama signal, whichever is selected. During operation, the chlorophyll content imager performs an analysis of the proportion of the percentage of reflectance of the two different wavelength channels, 700 and 840 nanometers. The system provides a video output, which can be seen to indicate the chlorophyll levels of the plant. The multiplexing and switching circuits described are useful for viewing the PSD signal in different modes. However, these can to be changed to suit the needs of the user. In this way, the multiplexing and switching circuits 114 can be changed in departing from the present invention. . The imager has been designed to allow a user to easily perform the system and see the chlorophyll levels of the plant in a place where the plant is growing. As such, a real-time analysis is possible, in addition, physical contact with the plant is not necessary as with transmittance-based instrumentation. The present invention can be used by biologists or farmers to help indicate any plant species that may be experiencing stress due to a variety of causes. Although the present invention does not identify the cause of such stress, it is believed that early detection of plant stress provides unavailable options if plant stress is not detected until visual indications are presented. It will be appreciated by those skilled in the art that variations in the circuit system or construction of the described chlorophyll content imager are possible. For example, video images can be digitized before performing the chlorophyll algorithm. In addition, variations in the optical filter wavelengths are contemplated. The described central wavelengths of 700 and 840 nanometers, however, are preferred and are believed to provide the best indication of an early loss of chlorophyll content. In addition, although a collection lens 120 has been described, it will be appreciated that multiple collection lenses may be used in combination with separate bandpass filters to measure the reflected light.

CONCLUSION A portable system for imaging the chlorophyll content of plants has been described, which collects reflected light from a white plant and separates the collected light into two bands of different wavelengths. These wavelength bands, or channels, are described as having central wavelengths of 700 nanometers and 840 nanometers. A controller provided in the system compares the level of image light of the reflected video images from a white plant with a reference level of light from a source that illuminates the plant. The percentage of reflection in the two separate wavelength bands of a white plant are compared to provide a proportion of the video image, which indicates a relative level of the physiological tension of the plant. Multiple modes of visual display to view video images were also described. A third chamber is described to provide an unfiltered image of the white plant.

Although several specific embodiments have been illustrated and described herein, it will be appreciated by those skilled in the art that any arrangement that is calculated to achieve the same purpose can be replaced by the specific embodiment shown. This application is intended to cover any adaptation or variation of the present invention. Therefore, it is clearly intended that this invention be limited only by the claims and equivalents thereof.

Claims (20)

1. An image-forming system for the chlorophyll Ht content comprising: an optical system providing at least two video output signals, a first video signal is filtered to have a first central transmission wavelength, a second signal video is filtered to have a second central transmission wavelength; 10 first and second light detectors for detecting a light source and providing first and second reference signals; and a controller for receiving the first and second video output signals and providing an output video signal indicating a relative chlorophyll content of the target plant, whereby the controller provides an image of a percentage of the light reflected from the target. white plant comparing the first and second video signals produced from the reflected light of the white plant against the outputs of the first and second reference signals.

2. The image forming system of the chlorophyll content according to claim 1, wherein the first central wavelength of transmission of the first video signal is 700 nanometers.

3. The image forming system of the chlorophyll content according to claim 1, wherein the first central wavelength of transmission of the first video signal is 840 nanometers.

4. The image forming system of the chlorophyll content according to claim 1, wherein the controller calculates a proportion of the reflectance percentage of the target plant as a percentage of the light reflected in the first transmission center wavelength with a percentage of the light reflected in the second central transmission wavelength.

5. The image forming system of the chlorophyll content according to claim 1, wherein the first and second light detectors provide first and second reference signals, which are respectively filtered to have equal transmission center wavelengths to the first and second central wavelengths of transmission of the first and second video signals.

6. The image forming system of the chlorophyll content according to claim 5, wherein the first central transmission wavelength is 700 nanometers, and the second central transmission wavelength of 840 nanometers.

7. The image forming system of the chlorophyll content according to claim 1, wherein the optical system comprises: a first video camera for providing the first video signal; a second video camera to provide the second video signal; a third video camera to provide a third unfiltered video signal; and an optical light splitting system for providing reflected light from the target plant to the first video camera, second video camera and third video camera, so that the first, second and third video signals are synchronized.

8. - The chlorophyll content image forming system according to claim 7, further comprising a multiplexing circuit system for providing the output video signal of the processor and the third video signal to a visual display monitor.

9. The image forming system of the chlorophyll content according to claim 8, wherein the multiplexing circuit system is configured to allow multiple modes of visual display of color and monochrome video.

10. A portable light reflectance video system for use in imaging the chlorophyll content of plants, comprising: an optical lens for collecting reflected light from a white plant under test; an optical light splitter to divide the light collected by the optical lens into first and second beams of light; a first optical bandpass filter for receiving the first light beam of the optical light splitter and providing a first light output having a central wavelength of approximately 700 nanometers; a first video camera for providing a first video signal in response to the first light output having a central wavelength of approximately 700 nanometers; a second optical bandpass filter for receiving the second light beam of the optical light splitter and providing a light output having a central wavelength of about 840 nanometers; a second video camera for providing a second video signal in response to the second light output having a central wavelength of approximately 840 nanometers; first and second light detectors for detecting a light source and providing first and second reference signals; a processor for providing an output video signal indicating the chlorophyll content levels of the plants as a proportion of the percentage of reflected light having a central wavelength of approximately 700 nanometers to the percentage of reflected light having a central wavelength of approximately 840 nanometers; and a visual display to provide a user with a video image of the white plant to identify the chlorophyll content.

11. The portable light reflectance video system according to claim 10, further comprising a third video camera to provide a third unfiltered video signal of the white plant.

12. The portable light reflectance video system according to claim 11, further comprising a multiplexing circuit for providing video signals to the visual display comprising the output video signal of the processor and the third video signal not filtered.

13. The portable light reflectance video system according to claim 11, further comprising a multiplexing circuit for providing video signals to the visual display comprising a sum of the output video signal of the processor and the third signal video not filtered.

14. The portable light reflectance video system according to claim 11, further comprising a multiplexing circuit for providing video signals to the visual display of the output video signal from the processor, which exceeds a value of predetermined threshold ratio.

15. The portable light reflectance video system according to claim 10, wherein the visual display presents the output video signal of the processor in a gray scale.

16. The portable light reflectance video system according to claim 10, wherein the first and second optical bandpass filters each have a bandwidth of 10 nanometers.

17. - The portable light reflectance video system according to claim 10, further comprising a threshold detection circuit for generating a video signal, which identifies any portion of white plant having a predetermined voltage level. 18.- A method to see what chlorophyll content of plants to identify early stress in plants using an imager of the chlorophyll content, the method comprises the steps of: detecting light from a light source having a first length cool; detect light from the light source having a second wavelength; provide a first video image of the light reflected from a white plant having the first wavelength; providing a second video image of the light reflected from the white plant having the second wavelength; providing a third video image of a first reflected percentage of light reflected from the white plant having the first wavelength of the light detected from the light source having the first wavelength; providing a fourth video image and a second reflected percentage of the reflected light of the white plant having the second wavelength from the detected light of the light source having the second wavelength; providing a fifth video image as a ratio of the third video image to the fourth video image using the chlorophyll content imager; and visually display the fifth video image. 19. The method according to claim 18, wherein the first wavelength is 700 nanometers and the second wavelength is 840 nanometers. 20. The method according to claim 18, wherein a low proportion indicates a low voltage level of the plant, and a high proportion indicates a high level of stress in the plant.