Abstract:
In an automatic photometer for metering light from a sample to be measured which includes a light source for illuminating the sample and an objective for focusing the light passed from the light source through the sample, a slit is positioned closely adjacent the focal plane of the objective and has an opening providing a central area and an outer area surrounding the central area. Two light receiving elements are disposed to receive the light passed through the central and outer areas of the slit, respectively, and means are provided for effecting photometry under selected conditions of light reception by the light receiving elements.

Description:
Cross-Reference to Related Application 
     This is a continuation-in-part of my copending application Ser. No. 392,862, filed Aug. 30, 1973, for AUTOMATIC PHOTOMETER, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an automatic photometer for metering light, such as transmitted light, reflected light, fluorescence or phosphorescence, from a sample to be measured. 
     2. Description of the Prior Art 
     A prior art photometer has employed an optical system as shown in FIG. 1 of the accompanying drawings. In such optical system, a light source 1 illuminates a sample 2 whose image is focused through an objective 3 onto a stop plate 4. Upon illumination from the light source 1, the sample 2 also provides a background having a certain intensity of brightness in itself. Further, the sample has a portion 2a to be measured as bright as the background itself, a portion 2b to be measured brighter than the portion 2a, and a portion 2c to be measured still brighter than the portion 2b (see FIG. 2). A light receiving element 5 is arranged to receive only that part of the light which has been passed through an opening 4&#39; in the stop plate 4. 
     With such arrangement, the light from the sample portion 2b can be fully received by the light receiving element 5 to measure the entire portion 2b when the image 2&#39;b of such portion is wholly contained within the opening 4&#39; of the stop plate 4 in the manner as shown in FIG. 3a. In the position as shown in FIG. 3b or 3c, however, the image 2&#39;b or 2&#39;c of the sample portion 2b or 2c is not wholly contained within the opening 4&#39; of the stop plate with the result that light from only a part of the image 2&#39;b or 2&#39;c is received for photometry by the light receiving element, thus providing an erroneous photometric indication. In other words, accurate photometry cannot be achieved unless the operator confirms at each test whether the image of the sample is completely aligned with the opening 4&#39; of the stop plate. Thus, the prior art photometer could not accomplish automatic photometry. 
     SUMMARY OF THE INVENTION 
     Thus, by the present invention, I contribute an automatic photometer which overcomes the above-noted difficulties and disadvantages and which is capable of automatically metering the light from a sample to be measured. 
     My automatic photometer for metering light from a sample to be measured comprises a light source for illuminating the sample to be measured, an objective for focusing the light passed from the light source through the sample, light blocking means having at least two areas permitting light passage therethrough, light receiving elements disposed to receive the light passed through the areas of the light blocking means, respectively, and means for effecting photometry under selected conditions of light reception by the light receiving elements. 
     There has thus been outlined rather broadly the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of the invention. It is important, therefore, that the claims be regarded as including such equivalent constructions as do not depart from the spirit and scope of the invention. 
    
    
     Specific embodiments of the invention have been chosen for purposes of illustration and description, and are shown in the accompanying drawings, forming a part of the specification wherein: 
     FIGS. 1 to 3 are views of the prior art photometer, FIG. 1 schematically showing the optical system employed therein, FIG. 2 being a plan view of a sample to be measured, and FIGS. 3a, 3b and 3c illustrating the photometry effected by such prior art photometer; 
     FIGS. 4 to 7 refer to an embodiment of the present invention, FIG. 4 being a plan view of the stop plate, FIGS. 5a and 5b illustrating the photometry effected by such embodiment, FIG. 6 showing a first embodiment of the present invention, and FIG. 7 being a graph illustrating the output curves; 
     FIG. 8 illustrates schematically a second embodiment of the present invention; 
     FIG. 9 illustrates schematically a third embodiment of the present invention; 
     FIG. 10 illustrates schematically a further embodiment of the present invention; and 
     FIG. 11 is a graph illustrating output curves applicable to the embodiment of FIG. 10. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring first to FIGS. 4 to 7, there is shown a first embodiment of the present invention. In FIG. 6, reference numerals 1 and 2 designate a light source and a sample to be measured, respectively. The optical arrangement shown there is designed such that the sample 2 is illuminated by the light source 1 and the image thereof is focused through an objective 3 onto a stop plate 4. As shown in FIG. 4, stop plate 4 has therein two light passing areas, a central area 4a and an outer area 4b surrounding the central area. The light passed through the area 4a is received by a light receiving element 5a while the light passed through the area 4b is received by another light receiving element 5b. A battery E is provided which is equal in value but opposite in polarity to an electrical signal appearing at the output of the light receiving element 5b when the image 2&#39;a, 2&#39;b or 2&#39;c of the sample portion 2a, 2b or 2c is not wholly contained within the outer area 4b, i.e. when the light receiving element 5b for receiving the light passed through the outer area 4b receives an intensity of light corresponding to the background provided by the sample 2. An electromagnet R and a switch S together constitute a relay and are designed such that the switch S is opened upon a current flowing through the electromagnet R. A meter M electrically indicates the intensity of the light from the central area 4a which is received by the light receiving element 5b. 
     Referring not to FIGS. 5a, 5b and 6, description will be made of operation of the first embodiment of my invention. Whenever the image 2&#39;b of the sample portion 2b is wholly contained within the central area 4a as shown in FIG. 5a, the light receiving element 5b for the outer area 4b of the stop plate 4 is receiving only an intensity of light corresponding to that of the background so that the electrical value of the electrical signal appearing at the output of the light receiving element 5b is equal in value but opposite in polarity to that of the battery E and thus, these two electrical values negate each other to prevent any current from flowing through the closed circuit formed by the battery E, electromagnet R and light receiving element 5b. As a result, the elecromagnet R is unenergized to maintain the switch S in closed position, whereby the indicator meter M indicates a measured intensity of the light from the image 2&#39;b of the sample portion 2b which is then wholly contained within the central area 4a of the stop plate 4. 
     Whenever the image 2&#39;b of the sample portion 2b is not wholly contained within the central area 4a in the manner as shown in FIG. 5b, the electrical value of the signal appearing at the output of the light receiving element 5b is increased to permit a current to flow through the closed circuit including the element 5b, battery E and electromagnet R. As a result, the electromagnet R is energized to open the switch S, which in turn opens the closed circuits 5a - S - M to prevent the indicator M from effecting photometry. 
     Thus, according to the first embodiment of the present invention as shown in FIG. 6, automatic photometry can take place only when the image 2&#39;a, 2&#39;b or 2&#39;c of the sample portion 2a, 2b or 2c of the sample 2 to be measured is wholly contained within the central area 4a of the stop plate 4. 
     FIG. 7 graphically illustrates the relationships between the distance of travel of the sample to be measured and the intensities of light received by the light receiving elements 5a and 5b. In the graph, the abscissa represents the distance of travel l and the ordinate represents the intensities of light In and In&#39; received by the light receiving elements 5a and 5b, respectively. The distance lO corresponds to the position in which photometry is effected for the background or the sample portion 2a of the sample 2, and in this position there is no current flowing through the closed circuit E - R - 5b with the switch S closed, whereby outputs 7 2a  and 7 2   &#39;a  are obtained from the light receiving elements 5a and 5b, respectively. The distance range from l1 to l2 corresponds to the position in which part of the images 2&#39;b or 2&#39;c of the sample portion 2b or 2c is contained within the outer area 4 of the stop plate 4, and in this position the light receiving element 5b receives a correspondingly increased intensity of light. At this time, an output 7 2   &#39;b  or 7 2   &#39;c  is obtained from the element 5b. At the same time, a current flows through the closed circuit E - R - 5b to open the switch S, thus disabling the indicator meter M to effect photometry with zero output of the light receiving element 5a. 
     The distance range from l2 to l3 corresponds to a position in which the image 2&#39;b or 2&#39;c of the sample portion 2b or 2c is wholly contained within the central area 4a of the stop plate 4, and in this position the output signal of the light receiving element 5b assumes the steady state as designated by 7 2a . At the same time, there is no current flowing through the closed circuit E - R - 5b with the switch S closed, thereby permitting the indicator meter M to effect photometry. In this case, the light receiving element 5a produces an output 7 2b  or 7 2c . 
     The distance range from l3 to l4 provides the same condition as that for l1 to l2. In this condition, the output of the light receiving element 5a is zero and no photometry is occurring for the sample portion 2b or 2c. 
     The distance range l4 to l exhibits the same condition as that for l0 to l1, wherein photometry is occurring for the background or the sample portion 2a. 
     From FIG. 7 it is possible to represent the levels of the sample portions 2a, 2b and 2c as the result of automatic photometry. Here, assuming that the images 2&#39;b and 2&#39;c are equal in size, it will be seen from FIG. 7 that the number of the sample portions 2b and of the sample portions 2c in a certain area can be counted by suitably selecting the diameter of the area 4a, say, to a value slightly smaller than double the diameter of the image 2&#39;b or 2&#39;c and also suitably selecting the pitch, say, to a value substantially equal to the diameter of the image 2&#39;b or 2&#39;c, and by scanning them over a plane. 
     The arrangement described above has been designed such that the intensity of light received by the light receiving element 5a is measured by the meter M only when the image 2&#39;a, 2&#39;b or 2&#39;c of the sample portion 2a, 2b or 2c is wholly contained within the central area 4a of the stop plate 4, whereas, the same effect as that described above may be achieved as well by having the data of both light receiving elements 5a and 5b recorded at all times and reading out the data of the element 5a only when the output of the element 5b is the level of 7 2   &#39;a  as shown in FIG. 7. 
     FIG. 8 illustrates a second embodiment of the present invention which differs from the embodiment of FIG. 6 in that two areas are provided in two distinct image forming planes, respectively. The light source 1, sample 2, objective 3 and light receiving elements 5a and 5b are all constructed similarly to those described with respect to FIG. 6. However, the optical system in this embodiment includes a prism 17 and a first stop plate 18 formed with a light passing opening 18a arranged such that the image 2&#39; of the sample 2 is focused at the first plate 18. The light passed through the opening 18a of the plate is led to the light receiving element 5a, while the remaining area 18b of the first slit 18, other than the opening 18a, is formed as a total reflection mirror so that all the light impinging on such area is reflected so as to pass through a set of relay lenses 20 and be focused on a second stop plate 19 having an opening 19a of greater diameter than that of the opening 18a of the first plate 18. With this arrangement, whenever the image of the sample portion 2a, 2b or 2c of different brightnesses is wholly contained within the opening 18a of the first plate 18, the image of the sample portion 2a, 2b or 2c is not focused at the second plate 19 so that the light receiving element 5b provides a steady condition as described with respect to the first embodiment of FIG. 6 and there is no current flowing through the closed circuit 5b - E - R with the switch closed, while the light is received by the light receiving element 5a and measured by the meter M. Whenever any of the described images is not wholly contained within the opening 18a, all or part of the light which is beyond the opening 18a is focused at the second plate 19 thereby to increase the intensity of the light receiving element 5b. As a result, a current flows through the closed circuit E - R - 5b to energize the electromagnet R, which thus opens the switch S to prevent photometry of the sample portions. 
     FIG. 9 illustrates a third embodiment of the present invention which employs a beam splitter 21 to form images at two points. A first stop plate 22 has an opening 22a through which light is passed to the light receiving element 5a. A second stop plate 23 has an opening 23a through which light is passed to the light receiving element 5c. The opening 23a has a greater diameter than that of the opening 22a. A differential amplifier DA is provided to receive as input the outputs from the light receiving elements 5a and 5c. The electromagnet R and switch S together constitute a relay and are designed such that the switch S is opened upon energization of the electromagnet R. M is an indicator meter for indicating the output of the light receiving element 5a. 
     Whenever the image of the sample is wholly contained only within the central area 22a which corresponds to the central area 4a or 18a shown in FIGS. 6 or 8, the two light receiving elements 5a and 5c produce outputs of equal magnitude which are applied as input to the differential amplifier DA, which in turn produces no output, so that the electromagnet R remains unenergized to maintain the switch S closed, thus permitting the output of the light receiving element 5a to be indicated by the indicator meter M. 
     Whenever the image of the sample is not wholly contained within the central area 22a, the light receiving element 5c produces a greater output than that produced by the element 5a and such output difference results in a corresponding output of the differential amplifier DA. However, since the electromagnet R is being energized to open the switch S, the indicator meter M cannot indicate the output of the light receiving element 5a. 
     Referring now to FIG. 10, the light source 1, sample 2, objective 3, stop plate 4 with central area 4a and outer or peripheral area 4b, and light receiving elements 5a and 5b  are constructed similarly to those of FIG. 6. However, light receiving element 5a is connected to one terminal of a first indicating means M1, the opposite terminal of which is grounded; and light receiving element 5b is connected to one terminal of a second indicating means M2, the opposite terminal of which is grounded. It will be seen that, according to this construction, the first indicating means M1 continuously displays an output of the first light receiving element 5a even when an image of a portion of a sample to be measured is not completely within the aperture 4a of the stop plate 4, as shown in the upper portion of the graph of FIG. 11. 
     The second indicating means M2 displays an output of the second light receiving element 5b, as shown in the lower portion of the graph of FIG. 11. Thus, portion 72c&#34;or 72b&#34;, which corresponds to a state in which the portion of the sample image to be measured is completely within the aperture 4a of stop plate 4, may be determined by observing the data displayed by both indicating means M1 and M2, the latter indicating means M2 serving as discriminating means for the system. It will be appreciated by those persons skilled in the art that the arrangement of first and second indicating means described in connection with the embodiment of FIG. 10, can as readily be employed with those embodiments described in connections with FIGS. 8 and 9. 
     From the foregoing description of the present invention wherein a surface disposed closely adjacent the formed real image of a sample to be measured is divided into a central area and outer area surrounding the central area so that light from the central area may be received by a light receiving element only when the image of the sample is wholly contained within the central area, it will be seen that photometry can be effected without the need to confirm every time whether the images of the portions of the sample to be measured are completely contained within the opening of the stop plate, unlike the prior art device. In addition, by moving the sample in a plane perpendicular to the optical axis, the number of the portions of the sample to be measured which are different in brightness, can be counted. 
     I believe that the construction and operation of my novel automatic photometer will be understood, and that the advantages thereof will be fully appreciated by those persons skilled in the art.