Reflection type radiation thickness meter

Claim 2

Apparatus for measuring the thickness of a substance utilizing reflected radiation comprising: a substrate sufficiently thick to saturate radiation reflected therefrom and receiving a substance whose thickness is measured thereon; a source of radiation to irradiate said substance; a radiation detector for receiving radiation reflected from said substance to provide an ionization current corresponding to the quantity of the received radiation; a reference unit including means for producing an electric quantity of opposite polarity and of equal magnitude to the ionization current generated by a sample of the same material as said substance but which is sufficiently thick to saturate radiation reflected therefrom; a first pre-adjusting means for defining a zero thickness point of said substance by causing the ionization current from said radiation detector to be of opposite polarity and of equal magnitude to the electric quantity generated by said reference unit upon receipt, by said radiation detector before actual measurement, of radiation reflected from another sample of the same material as said substance and which sample is sufficiently thick to saturate radiation reflected therefrom; a logarithmic amplifier supplied with an electrical quantity corresponding to the difference between said output electrical quantities froM said reference unit and said radiation detector facing said substance mounted on said substrate which is substituted for said another sample, following said first preadjustment; and an indicating meter for providing readings substantially linearly proportional to the magnitude of the output signal from said logarithmic amplifier.

Claim 3

Apparatus for measuring the thickness of a substance utilizing reflected radiation comprising: a substrate sufficiently thick to saturate radiation reflected therefrom and receiving a substance whose thickness is to be measured thereon; a source of radiation to irradiate said substance; a radiation detector for receiving radiation reflected from said substance to produce an ionization current corresponding to the quantity of the received radiation; a reference unit including means for producing an electric quantity of opposite polarity and of equal magnitude to the ionization current generated by a sample of the same material as said substance but which is sufficiently thick to saturate radiation reflected therefrom; a logarithmic amplifier supplied with an electrical quantity corresponding to the difference between said output electrical quantities from said reference unit and said radiation detector; a differential amplifier coupled to the output of said logarithmic amplifier, a signal from the logarithmic amplifier being applied to one input terminal thereof and a variable DC source being connected to the other input terminal thereof; a first pre-adjusting means for defining a zero thickness point of said substance by causing ionization current from said radiation detector to be of opposite polarity and of equal magnitude to the electric quantity generated by said reference unit upon receipt, by said radiation detector before actual measurement, of radiation reflected from another sample of the same material as said substance but which is sufficiently thick to saturate radiation reflected therefrom; a second pre-adjusting means for defining a zero level of the output from said differential amplifier by adjusting the input signal to at least one input terminal of said differential amplifier such that the current fed thereto from said logarithmic amplifier is of opposite polarity and of equal magnitude to the electric current applied to the other input terminal of said differential amplifier from said variable DC source upon receipt, by said radiation detector further following said first preadjustment and before actual measurement, of radiation reflected from still another sample of one of a sample of the same material as said substrate and which is sufficiently thick to saturate radiation reflected therefrom and another sample of the same material as said substance but having a predetermined thickness; and an indicating meter for providing a display substantially linearly proportional to the magnitude of the resultant output signal obtained through said logarithmic amplifier and differential amplifier following said first and second pre-adjustments.

Claim 4

Apparatus for measuring the thickness of a substance utilizing reflected radiation comprising: a substrate sufficiently thick to saturate radiation reflected therefrom and receiving a substance whose thickness is to be measured thereon; a source of radiation to irradiate said substance; a radiation detector for receiving radiation reflected from said substance to produce an ionization current corresponding to the quantity of the received radiation; a reference unit including means for producing an electric quantity of opposite polarity and of equal magnitude to the ionization current generated by a sample of the same material as said substance but which is sufficiently thick to saturate radiation reflected therefrom; a logarithmic amplifier supplied with an electrical quantity corresponding to the difference between said output electrical quantities from said reference unit and said radiation detector; a differential amplifier coupled to the output of said logarithmic amplifier, a signal from the logarithmic amplifier being applied to one input terminal thereof and a variable DC source being connected to the other input terminal thereof; a first pre-adjusting means for defining a zero thickness point of said substance by causing ionization current from said radiation detector to be of opposite polarity and of equal magnitude to the electric quantity generated by said reference unit upon receipt, by said radiation detector before actual measurement, of radiation reflected from another sample of the same material as said substance but which is sufficiently thick to saturate radiation reflected therefrom; a second pre-adjusting means for defining a zero level of the output from said differential amplifier by adjusting the input signal to at least one input terminal of said differential amplifier such that the current fed thereto from said logarithmic amplifier is of opposite polarity and of equal magnitude to the electric current applied to the other input terminal of said differential amplifier from said variable DC source upon receipt, by said radiation detector further following said first preadjustment and before actual measurement, of radiation reflected from still another sample of one of a sample of the same material as said substrate and which is sufficiently thick to saturate radiation reflected therefrom and another sample of the same material as said substance but having a predetermined thickness; and an indicating meter for providing a display substantially linearly proportional to the magnitude of the resultant output signal obtained through said logarithmic amplifier and differential amplifier following said first and second pre-adjustments.

Claim 5

Apparatus according to claim 2 wherein said zero level of the output from said differential amplifier is set as the output level of said differential amplifier corresponding to supplying to said one input terminal thereof an ionization current generated by said radiation detector which received, before actual determination, radiation reflected from the same material as said substance but of a standard thickness, whereby readings on said indicating meter represent the degree to which the thickness of said substance mounted on said substrate deviates from a standard value corresponding to said standard thickness.

Claim 6

Apparatus according to claim 1 wherein said reference unit comprises a calibrated member of the same material as said substance and which is sufficiently thick to saturate incident radiation, and a radiation detector facing said calibrated member.

Claim 7

Apparatus according to claim 2 wherein said reference unit comprises a calIbrated member of the same material as said substance and which is sufficiently thick to saturate incident radiation, and a radiation detector facing said calibrated member.

Claim 8

Apparatus according to claim 1 including an amplifier coupled to the input of said logarithmic amplifier to pre-amplify the electrical quantity supplied to said logarithmic amplifier, and wherein said reference unit comprises a DC source disposed in a negative feedback network connected in parallel between the input and output terminals of said amplifier.

Claim 9

Apparatus according to claim 2 including an amplifier coupled to the input of said logarithmic amplifier to pre-amplify the electrical quantity supplied to said logarithmic amplifier, and wherein said reference unit comprises a DC source disposed in a negative feedback network connected in parallel between the input and output terminals of said amplifier.

Claim 10

Apparatus according to claim 1 wherein said radiation detector comprises: a double walled cylindrical protective casing having a closed bottom; a solid cylindrical holder at the center of said protective casing, said holder being provided with an opening for receiving a source of radiation on its top; a high voltage electrode assembly of double walled cylindrical construction and insulatedly supported in said protective casing, the bottom of said high voltage electrode assembly being closed; and a wire net shaped collector electrode assembly mounted adjacent to said electrode assembly.

Claim 11

Apparatus according to claim 2 wherein said radiation detector comprises: a double walled cylindrical protective casing having a closed bottom; a solid cylindrical holder at the center of said protective casing, said holder being provided with an opening for receiving a source of radiation on its top; a high voltage electrode assembly of double walled cylindrical construction and insulatedly supported in said protective casing, the bottom of said high voltage electrode assembly being closed; and a wire net shaped collector electrode assembly mounted adjacent to said electrode assembly.