US3771877A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Densitometer incorporating optical attenuator with direct readout of optical density
Assignee: VWR Corp
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Filing: 1972-02-14
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Granted: 1973-11-13
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Expires: 1992-02-14
Abstract
Abstract An instrument for determining optical density by measurement of diffuse reflected light. The instrument includes a light source, means for forming a beam of diffuse reflected light, an electrical balancing circuit, and an optical attenuator for controlling the intensity of light incident on a photoresponsive element forming a part of the balancing circuit. In the use of the instrument, the units of optical density are read directly from the optical attenuator, and mechanical movement thereof serves to provide an aperture of increased or decreased size, admitting more or less light, until electrical balance is achieved in the circuit. A balanced circuit condition is indicated by extinguishment of a single bulb, and the reading is taken only when the balanced condition occurs. In the preferred form of construction, the optical attenuator is in the form of a disc or wheel having a gradually increasing opening therein, and adapted for direct manipulation by the operator. Calibration of the instrument is achieved by illuminating a standard or known control specimen, and adjusting a nulling potentiometer in a balancing bridge to produce a balanced condition in the circuit. By using a mechanical attenuator instead of an electrical signal strength control, the unit is simplified in construction and is more accurate and reliable in use.
Inventors
- 👤 R Rosencranz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 03:08
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/47; G01N21/4738; G01N21/474; G01J; G01J1/00; G01J1/10; G01J1/20; G01J1/22; G01J1/24
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
157 words
A reflection densitometer for measuring the optical density of a specimen, said densitometer comprising, in combination: a light source directed on said specimen; means for receiving a light beam diffusely reflected from said specimen along a path extending away from said specimen; an electrical balancing circuit including a photoresponsive element lying in the path of said light beam for controlling the balance of said circuit according to the intensity of said beam, and further including an output indicator for indicating a balanced condition in said circuit; optical attenuating means disposed in said path of said light beam for varying the intensity of said beam impinging on said photoresponsive element; indicating means mechanically coupled to said optical attenuating means for indicating optical density; and calibration means for establishing the balance point of said electrical balancing circuit such that when said attentating means is adjusted to balance said circuit said indicating means indicates the optical density of said specimen.
Claim 2
Dependent Claim
157 words
A reflection densitometer for measuring the optical density of a specimen, said densitometer comprising, in combination: a light source directed on said specimen; means for receiving a light beam diffusely reflected from said specimen along a path extending away from said specimen; an electrical balancing circuit including a photoresponsive element lying in the path of said light beam for controlling the balance of said circuit according to the intensity of said beam, and further including an output indicator for indicating a balanced condition in said circuit; optical attenuating means disposed in said path of said light beam for varying the intensity of said beam impinging on said photoresponsive element; indicating means mechanically coupled to said optical attenuating means for indicating optical density; and calibration means for establishing the balance point of said electrical balancing circuit such that when said attentating means is adjusted to balance said circuit said indicating means indicates the optical density of said specimen.
Claim 3
Dependent Claim
29 words
A densitometer unit as defined in claim 1 wherein said photoresponsive element comprises a photo-resistor having a resistance which varies in response to the intensity of light received thereby.
Claim 4
Dependent Claim
69 words
A densitometer unit as defined in claim 1 in which said balancing circuit includes a Wheatstone bridge having three resistors of predetermined resistance and in which said photoresponsive means forms a fourth resistor, said bridge being supplied at two terminals thereof by an energy source, and adapted to have a signal occur at one of the terminals thereof except when the resistance of said photosensor has a predetermined value.
Claim 5
Dependent Claim
64 words
A densitometer unit as defined in claim 1 in which said balancing circuit is in the form of a bridge having a fixed resistor, a pair of adjustable resistors, and a variable resistor, whereby said adjustable resistors may be adjusted so as to produce a substantially zero bridge output only under conditions when said variable resistor is sufficiently illuminated to produce a predetermined resistance.
Claim 6
Dependent Claim
40 words
A densitometer unit as defined in claim 1 which further includes means for illuminating a specimen disposed adjacent the beam forming means and having means for directing such illumination to the surface of said specimen at substantially a 45* angle.
Claim 7
Dependent Claim
32 words
A densitometer unit as defined in claim 1 which further includes means for removably interposing plural selected optical filters within the path of said beam between said specimen and said photoresponsive means.
Claim 8
Dependent Claim
35 words
A densitometer unit as defined in claim 1 which further includes means for interposing at least one additional aperture between said specimen and said photo-responsive means, whereby additional control of light attenuation may be provided.
Claim 9
Dependent Claim
57 words
A densitometer unit as defined in claim 1 wherein the elements thereof are incorporated into an instrument having an optical head portion, mounted for movement toward and away from a specimen, the optical density of which is to be determined, and which includes means for positioning said head in a predetermined position in relation to said specImen.
Claim 10
Dependent Claim
31 words
A densitometer unit as defined in claim 1 wherein said means for indicating the optical density of said specimen comprises a digital display unit mechanically coupled to said mechanical control means.
Claim 11
Dependent Claim
61 words
A densitometer unit as defined in claim 1 in which said optical attenuator is in the form of a rotatable wheel having a continuous, scroll-like opening thereof extending generally parallel to the periphery of the wheel throughout a significant portion of its extent and having the center of said opening spaced a substantially constant distance from the center of said wheel.
Claim 12
Dependent Claim
58 words
A densitometer unit as defined in claim 1 wherein said opening in said attenuator increases logarithmically for each unit of rotation of said attenuator, whereby units indicating equally spaced gradients of optical density may be spaced equally about the periphery of said attenuator, and whereby interpolation between units thereof may be accurately carried out on a linear basis.
Claim 13
Dependent Claim
61 words
A densitometer instrument as defined in claim 1 in which said optical attenuator is in the form of a rotatable wheel having a continuous, scroll-like opening thereof extending generally parallel to the periphery of the wheel throughout a significant portion of its extent and having the center of said opening spaced a substantially constant distance from the center of said wheel.
Claim 14
Dependent Claim
31 words
A densitometer unit as defined in claim 1 wherein said means for indicating the optical density of said specimen comprises a digital display unit mechanically coupled to said mechanical control means.
Claim 15
Dependent Claim
215 words
A reflection densitometer for measuring the optical density of a specimen, said densitometer comprising, in combination: an instrument housing; means defining an opening in said housing, said opening being adapted to be placed adjacent said specimen for receiving light reflected diffusely therefrom; means in said housing for receiving a plurality of light sources arranged about the periphery of said opening; means for directing the light from said light sources at said specimen surface at a substantial angle from the vertical; means for receiving the light diffusely reflected from said specimen along a path extending generally perpendicularly from said specimen; an electrical balancing circuit including a photo-responsive element lying in the path of said diffusely reflected light for controlling the balance of said circuit according to the intensity of said light, and further including an output indicator for indicating a balanced condition in said circuit; optical attenuating means disposed in the path of said diffusely reflected light for varying the intensity of said light impinging on said photo-responsive element; indicating means coupled to said optical attenuating means for indicating optical density; and calibration means for establishing the balance point of said electrical balancing circuit such that when said attenuating means is adjusted to balance said circuit said indicating means indicates the optical density of said specimen.
Claim 16
Dependent Claim
215 words
A reflection densitometer for measuring the optical density of a specimen, said densitometer comprising, in combination: an instrument housing; means defining an opening in said housing, said opening being adapted to be placed adjacent said specimen for receiving light reflected diffusely therefrom; means in said housing for receiving a plurality of light sources arranged about the periphery of said opening; means for directing the light from said light sources at said specimen surface at a substantial angle from the vertical; means for receiving the light diffusely reflected from said specimen along a path extending generally perpendicularly from said specimen; an electrical balancing circuit including a photo-responsive element lying in the path of said diffusely reflected light for controlling the balance of said circuit according to the intensity of said light, and further including an output indicator for indicating a balanced condition in said circuit; optical attenuating means disposed in the path of said diffusely reflected light for varying the intensity of said light impinging on said photo-responsive element; indicating means coupled to said optical attenuating means for indicating optical density; and calibration means for establishing the balance point of said electrical balancing circuit such that when said attenuating means is adjusted to balance said circuit said indicating means indicates the optical density of said specimen.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-11-12 | 1977-05-14 | 1977-11-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-12 | 1981-05-14 | 1981-11-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-12 | 1985-05-14 | 1985-11-13 | $7700.00 | Window Closed / Lapsed |