Photometer for carrying out measurements at different wave lengths

Claim 2

Apparatus for measuring the light absorption and light transmission of an object with respect to light of different wave lengths comprising a light source, means adjacent the light source for periodically forming at least three sequentially occurring light pulses along at least three different light ray paths, means optically downstream of the light pulse forming means for filtering light in at least two of the paths to obtain at least two sequential relatively narrow band width light pulses, a photocell, means for optically aligning the narrow band width light pulses and for passing such pulses through the object onto the photocell, means optically downstream of the light pulse forming means for passing reference light pulses formed on a third path onto the photocell, and means providing output signals as a function of the relative light intensity between the narrow band width light pulses and the reference light pulses.

Claim 3

Apparatus according to claim 1 wherein the means for providing output signals includes compensating means for maintaining the signals constant in response to variations in the intensity of the light pulses.

Claim 4

Apparatus according to claim 1 including means forming a control light pulse for each of the first mentioned light pulses, the control light pulses being formed from light from the source in synchronism with the light pulses, a number of electrical branch circuits equalling the number of formed light pulses, and means responsive to the control light pulses for connecting the photocell with the electrical branch circuits so that photocell pulse signals produced by light pulses from a given path are always transmitted to the same branch circuit.

Claim 5

Apparatus according to claim 1 including means for comparing photocell emitted signals produced by narrow band width light pulses with a constant reference voltage, and means for adjusting the photocell signals in accordance with light intensity variations in the light pulses formed from the light source.

Claim 6

Apparatus for measuring the light absorption and light transmission of a sample under light of different wave lengths comprising: a light source, means for forming at least three parallel paths for light rays from the source, means for periodically and sequentially intErrupting the light ray paths so that light can pass along one path only during any instant of time, light filter means optically downstream of the light interrupting including at least one dichroic filter disposed in a first path passing light of one band length and reflecting light of another band length, and means disposed in another path and reflecting light from the other path onto a reflecting surface of the dichroic filter so that first wave band light passes through the filter onto the sample and second wave band light is reflected from the second path into alignment with the first path and reflected by the dichroic filter onto the sample, a single photocell disposed on the side of the sample opposite the dichroic filter, means directing light rays passing through the sample to the photocell, means directing light pulses in a third path directly to the photocell to provide reference light pulses, and electrical means producing output signals indicative of the light intensities of light rays received by the photocell from the sample.

Claim 7

Apparatus for measuring the light absorption and light transmission of a sample under light of different wave lengths comprising: a light source, means for forming at least three parallel paths for light rays from the source, means for periodically and sequentially intErrupting the light ray paths so that light can pass along one path only during any instant of time, light filter means optically downstream of the light interrupting including at least one dichroic filter disposed in a first path passing light of one band length and reflecting light of another band length, and means disposed in another path and reflecting light from the other path onto a reflecting surface of the dichroic filter so that first wave band light passes through the filter onto the sample and second wave band light is reflected from the second path into alignment with the first path and reflected by the dichroic filter onto the sample, a single photocell disposed on the side of the sample opposite the dichroic filter, means directing light rays passing through the sample to the photocell, means directing light pulses in a third path directly to the photocell to provide reference light pulses, and electrical means producing output signals indicative of the light intensities of light rays received by the photocell from the sample.

Claim 8

Apparatus according to claim 5 wherein the electrical means include means for producing a constant reference signal, and means for producing output signals relative to the reference signal.

Claim 9

Apparatus according to claim 6 wherein the light source comprises a point light source, and including first collimating lens means disposed upstream of the sample for producing substantially parallel light rays, and second focusing lens means disposed downstream of the sample for directing light passing the sample and from the third path onto the signal photocell.

Claim 10

Apparatus according to claim 5 wherein the means for forming three parallel paths for light rays is disposed adjacent the light source and includes a mask having three openings, and wherein the light ray interruption means comprises a rotatable disc facing the mask, extending into the light ray paths and having a separate light passage aperture for each path, each aperture being positioned for rotation into alignment with an opening in the mask, the apertures being angularly and circumferentially spaced so that they are non-overlapping in a radial direction and a circumferential direction.

Claim 11

Apparatus according to claim 8 including control means for determining the light path from which the photocell receives light rays at any instant of time, the control means including a plurality of radially and circumferentially spaced second apertures in the rotating disc, the second apertures being also radially and circumferentially spaced from the light passage apertures, and light sensing means disposed on the side of the disc opposite the light source for receiving light from the light source passed through the control apertures.

Claim 12

In an apparatus for measuring the light absorption and transmission of a sample by subjecting the sample to light of different wave lengths, the apparatus having a light source, means separating light rays from the source into parallel light ray paths, a disc-shaped diaphragm rotating at a uniform rate and permitting the periodic and sequential passage of light rays of each path so that light rays can only be present in one path during any instant of time, light filter means disposed on the side of the diaphragm opposite the light source and having different filters disposed in the light ray paths, a single photocell disposed optically downstream of the filter means, and electrical signal emitting means in operative connection with the photocell for the emission of electrical signals indicative of the light passing the sample, the improvement comprising: a disc-shaped diaphragm having at least three radially and circumferentially non-overlapping light transmitting apertures, the number of apertures corresponding to the number of light ray paths, at least one dichroic filter disposed optically downstream of the filter means in a first light ray path and permitting passage of light of the first path received from the filter means, mirror means disPosed in a second path opposite the dichroic filter so that light reflected by the mirror means is reflected by the dichroic mirror and directed towards the photocell in alignment with the first path, focusing lens means disposed between the photocell and the dichroic filter for directing light received from the light ray paths onto the photocell, the signal emitting means including a plurality of branch circuits corresponding to the plurality of light transmitting apertures in the disc-shaped diaphragm, control means, switch means operated by the control means for transmitting photocell output signals obtained from a light of a given path to the branch circuit to which the given path corresponds, and comparing circuit means for the emission of photocell signals caused by light pulses from the first and second paths with photocell signals caused from light pulses from a third reference path.

Claim 13

In an apparatus for measuring the light absorption and transmission of a sample by subjecting the sample to light of different wave lengths, the apparatus having a light source, means separating light rays from the source into parallel light ray paths, a disc-shaped diaphragm rotating at a uniform rate and permitting the periodic and sequential passage of light rays of each path so that light rays can only be present in one path during any instant of time, light filter means disposed on the side of the diaphragm opposite the light source and having different filters disposed in the light ray paths, a single photocell disposed optically downstream of the filter means, and electrical signal emitting means in operative connection with the photocell for the emission of electrical signals indicative of the light passing the sample, the improvement comprising: a disc-shaped diaphragm having at least three radially and circumferentially non-overlapping light transmitting apertures, the number of apertures corresponding to the number of light ray paths, at least one dichroic filter disposed optically downstream of the filter means in a first light ray path and permitting passage of light of the first path received from the filter means, mirror means disPosed in a second path opposite the dichroic filter so that light reflected by the mirror means is reflected by the dichroic mirror and directed towards the photocell in alignment with the first path, focusing lens means disposed between the photocell and the dichroic filter for directing light received from the light ray paths onto the photocell, the signal emitting means including a plurality of branch circuits corresponding to the plurality of light transmitting apertures in the disc-shaped diaphragm, control means, switch means operated by the control means for transmitting photocell output signals obtained from a light of a given path to the branch circuit to which the given path corresponds, and comparing circuit means for the emission of photocell signals caused by light pulses from the first and second paths with photocell signals caused from light pulses from a third reference path.

Claim 14

Apparatus according to claim 10 wherein the control means comprise a plurality of control photocells corresponding to the plurality of branch circuits, the control photocells being disposed on the side of the diaphragm opposite the light source and spaced in a radial direction of the diaphragm, the diaphragm comprising control apertures for the transmission of control light pulses to the control photocells, the control apertures being radially spaced from the light transmitting apertures, circumferentially offset with respect to the light transmitting apertures forward of the light transmitting apertures in the direction of rotation of the disc, and wherein the signal emitting means includes normally opened first switch means for each branch circuit operatively connected with the control photocells for closing the first switch means and thereby connecting the branch circuits with the photocell for the time period during which the light of a light path corresponding to the branch circuit of the closed first switch is directed onto the photocell.

Claim 15

Apparatus according to claim 11 wherein each branch circuit includes amplifying means connected to the side of the first switch means opposite the photocell, and including second switch means for each branch circuit disposed on the side of the amplifying means opposite the first switch means, the second switch means being normally closed, operatively connected with the control photocells for actuation thereby and synchronously opened with the closing of the first switch means for the same time periods, the second switch means connecting an output of the amplifying means with a ground.

Claim 16

Apparatus according to claim 12 wherein the first and second switch means comprise semi-conductors having control electrodes.

Claim 17

Apparatus according to claim 12 including differential amplifying means having a first input terminal connected to the branch circuit corresponding to the reference light path and a second input terminal connected to a constant reference voltage source, second differential amplifying means disposed between the first switch means and the photocell, the first and second differential amplifier being operatively connected so that voltage variations on the input side of the second amplifying means causes an adjustment of the amplification rate of the first amplifying means for maintaining the second amplifying means input voltage constant.

Claim 18

Apparatus according to claim 14 wherein the branch circuits corresponding to light ray paths directed through the sample are connected to means providing output signals proportional to the logarithm of the signals received from such branch circuits, and further including a third differential amplifying means receiving the logarithm signals and the constant reference voltage.

Claim 19

Apparatus according to claim 10 wherein the disc-shaped diaphragm defines the light transmitting apertures and a like plurality of control apertures, the apertures being disposed in a given sector of the disc, and wherein the disc has a plurality of such sectors each containing the same arrangement of light transmitting apertures and control apertures.

Claim 20

Apparatus according to claim 10 wherein the path defining means is disposed between the diaphragm and the light source and includes spaced apart light transmitting openings aligned with the rotational paths of the light transmitting apertures.

Claim 21

Apparatus according to claim 10 wherein the disc-shaped diaphragm defines the light transmitting apertures and a like number of control apertures, wherein the light ray path defining means is disposed between the light source and the disc-shaped diaphragm and comprises a fixed diaphragm having light transmitting openings aligned with paths of the light transmitting apertures, and second light transmitting control openings aligned with the paths of the control apertures in the diaphragm.

Claim 22

Apparatus according to claim 10 including a fixed diaphragm having an aperture aligned with the first path and an aperture aligned with the reference path, the fixed diaphragm being disposed between the focusing lens means adjacent the photocell and the dichroic filter.

Claim 23

Apparatus according to claim 10 wherein the light source comprises a point light source, and including light collimating lens means disposed between the light source and the diaphragm for forming a light beam of substantially parallel light.

Claim 24

Apparatus according to claim 10 wherein the filter means comprises a first blue filter disposed in the first light ray path and a second yellow filter disposed in the second light ray path, and wherein the dichroic filter is transparent to blue light and reflects yellow light.

Claim 25

Apparatus according to claim 10 including a lens between the dichroic filter and the sample for focusing light in the sample.

Claim 26

Apparatus according to claim 10 including lens means disposed in the reference light ray path for focusing light from the reference light ray path on the photocell.

Claim 27

Apparatus according to claim 10 wherein the light ray path forming means forms at least four light ray paths, wherein the disc-shaped diaphragm has four radially and circumferentially spaced apart, non-overlapping apertures, wherein the filter means for the fourth light ray path has filtering characteristics different from the filter means for the other light ray paths, and including: second mirror means directing light passing the filter means for the fourth light ray path towards the first path, a second dichroic filter disposed in the first path opposite the second mirror means permitting the passage of light received from the first dichroic filter and reflecting light received from the second mirror means in alignment with the first light ray path towards the photocell.