US3740563A — Electroptical system and method for sensing and c…

Claim 1

Independent Claim 162 words

A system for controlling the diameter of a pulled crystal, comprising detection means for receiving a light image reflected from a preselected area on the meniscus of a melt adjacent a crystal which is being pulled from the melt, said detection means including first sensing means responsive to positional variations of said reflected light image along a first axis for providing a first control signal which varies as a function of the level of said melt and second sensing means responsive to positional variations of said reflected light image along a second axis for simultaneously providing a second control signal substantially independent of said first control signal, said second signal varying as a function of variations in the diameter of said pulled crystal, means responsive to said first control signal for maintaining a predetermined distance between said first and second sensing means and said melt and means responsive to said second control signal for controlling the diameter of said crystal being pulled.

Claim 2

Independent Claim 162 words

A system for controlling the diameter of a pulled crystal, comprising detection means for receiving a light image reflected from a preselected area on the meniscus of a melt adjacent a crystal which is being pulled from the melt, said detection means including first sensing means responsive to positional variations of said reflected light image along a first axis for providing a first control signal which varies as a function of the level of said melt and second sensing means responsive to positional variations of said reflected light image along a second axis for simultaneously providing a second control signal substantially independent of said first control signal, said second signal varying as a function of variations in the diameter of said pulled crystal, means responsive to said first control signal for maintaining a predetermined distance between said first and second sensing means and said melt and means responsive to said second control signal for controlling the diameter of said crystal being pulled.

Claim 3

Dependent Claim 141 words

The system defined in claim 1 wherein a. said first sensing means includes first and second light-sensitive areas separated from each other and differentially responsive to the positional variations of said image in either direction along said first axis for generating said first control signal, and b. said second sensing means includes third and fourth light-sensitive areas separated from each other and selectively located with respect to said first and second light-sensitive areas so as to be substantially nonresponsive to positional variations of said image along said first axis, said third and fourth light-sensitive areas being differentially responsive to said positional variations of said reflected image along said second axis for generating said second control signal, whereby both the distance between said sensing means and said melt and said crystal diameter are simultaneously and independently controlled during a crystal pulling operation.

Claim 4

Dependent Claim 130 words

The system defined in claim 2 wherein: a. said first and second light-sensitive areas are separated from one another along said first axis by a predetermined distance, and b. said third and fourth light-sensitive areas are located between said first and second light-sensitive areas and are separated from one another along said second axis by a predetermined distance, said axes intersecting at substantially a right angle, whereby limited movement of a reflected light image on said first axis across said first and second light-sensitive areas does not change the total light of said image impinging on said third and fourth light-sensitive areas, and limited movement of said light image on said second axis does not change the total light of said image impinging on said first and second light-sensitive areas.

Claim 5

Dependent Claim 86 words

The system defined in claim 3 which further includes means for focusing a single light beam on said preselected area of said meniscus, said light beam being reflected from said preselected area to provide said image said light beam bearing focused on said meniscus at a preselected angle with respect to the longitudinal axis of said crystal whereby the reflected light image received by said detection means will cause differential response by said first and second light-sensitive areas and said third and fourth light-sensitive areas, respectively.

Claim 6

Dependent Claim 67 words

The system defined in claim 2 wherein said first, second, third and fourth light sensitive areas are each adapted to provide an electrical output and wherein said means responsive to said first control signal comprises a first control loop interconnected with said first and second light-sensitive areas and including a servomotor operable for maintain the predetermined distance between the sensing means and the surface of said melt.

Claim 7

Dependent Claim 48 words

The system defined in claim 5 wherein said means responsive to said second control signal comprises a second control loop interconnected with said third and fourth lighT-sensitive areas and operative for controlling the pull rate of the crystal being pulled so as to maintain a selected crystal diameter.

Claim 8

Dependent Claim 87 words

The system defined in claim 6 which further includes a light source whose light output is controllable, said light source providing a light beam which is reflected from said preselected area on the meniscus, and a third control loop interconnected with a plurality of said light-sensitive areas and responsive to said changes in the total light impinging on said plurality of light-sensitive areas for controlling the light output from said light source thereby to maintain a substantially constant total light impinging on said plurality of light-sensitive areas.

Claim 9

Dependent Claim 80 words

The system defined in claim 7 wherein said third control loop is a normalizing control loop including comprises a comparator for receiving a signal which is the sum of the electrical outputs of said third and fourth light-sensitive areas and for comparing the last said signal with a reference voltage for controlling the power applied to said light source as a function of variations in the total light from said light source impinging on said third and fourth light-sensitive areas.

Claim 10

Independent Claim 145 words

A method for controlling the diameter of a crystal pulled from a liquid melt which includes the steps of: a. focusing a beam of light on the meniscus formed by a crystal being pulled from said melt, b. receiving a light image reflected from said meniscus and which moves along first and second axes in response to changes in melt level and lateral meniscus position, respectively, c. generating a first control signal in response to positional variations of said reflected image along said first axis for tracking the level variations of said melt, and d. generating a second control signal in response to positional variations of said reflected image along said second axis for controlling the diameter of said crystal, whereby said tracking of said melt prevents errors from being introduced into said second control signal by melt level variations during a crystal pulling operation.

Claim 11

Independent Claim 145 words

A method for controlling the diameter of a crystal pulled from a liquid melt which includes the steps of: a. focusing a beam of light on the meniscus formed by a crystal being pulled from said melt, b. receiving a light image reflected from said meniscus and which moves along first and second axes in response to changes in melt level and lateral meniscus position, respectively, c. generating a first control signal in response to positional variations of said reflected image along said first axis for tracking the level variations of said melt, and d. generating a second control signal in response to positional variations of said reflected image along said second axis for controlling the diameter of said crystal, whereby said tracking of said melt prevents errors from being introduced into said second control signal by melt level variations during a crystal pulling operation.

Claim 12

Dependent Claim 53 words

The method defined in claim 9 which further includes generating a third control signal as a function of a chosen threshold level of light received at a given location relative to said crystal meniscus for varying the light intensity of said beam and thereby maintaining the light intensity at said given location constant.

Claim 13

Dependent Claim 134 words

A process for generating an optical signal which is closely proportional to changes in the diameter of a crystal rod which is pulled from a melt, said process including, in combination: a. projecting a sharply focused, uniformly illuminated image pattern onto substantially the entire curved portion of the liquid meniscus extending between the melt and the crystal rod at liquid-solid interface therebetween, and b. sensing the movement of a relatively small spot within said sharply focused pattern and lying in a plane which intersects the horizontal surface of said melt at a predetermined angle, whereby said spot continuously appears at a substantially constant distance from the periphery of the said crystal rod and tracks said periphery and variations in crystal rod size as a result of rotational eccentricities and non-circular shapes in said rod.

Claim 14

Dependent Claim 134 words

A process for generating an optical signal which is closely proportional to changes in the diameter of a crystal rod which is pulled from a melt, said process including, in combination: a. projecting a sharply focused, uniformly illuminated image pattern onto substantially the entire curved portion of the liquid meniscus extending between the melt and the crystal rod at liquid-solid interface therebetween, and b. sensing the movement of a relatively small spot within said sharply focused pattern and lying in a plane which intersects the horizontal surface of said melt at a predetermined angle, whereby said spot continuously appears at a substantially constant distance from the periphery of the said crystal rod and tracks said periphery and variations in crystal rod size as a result of rotational eccentricities and non-circular shapes in said rod.

Claim 15

Dependent Claim 93 words

The process defined in claim 11 wherein: a. the projecting of the image pattern includes projecting the image pattern such that it has a longer dimension aligned radially outward from the crystal axis and spanning substantially the entire curved portion of said meniscus, and b. said sensing of the movement of the said spot is effected by photosensing by positioning multiple photosensitive surfaces in the path of the anticipated movement of light reflected from said spot thereby to generate differential signals as a result of the shifting of said spot within said pattern.

Claim 16

Dependent Claim 59 words

The system defined in claim 5 wherein said first control loop comprises a differential amplifier providing an output which is the differential of the electrical outputs of said first and second light-sensitive areas, and a comparator for comparing the output signal from said differential amplifier with a reference voltage, said servomotor being controlled by an output from said comparator.

Claim 17

Dependent Claim 64 words

The system defined in claim 6 wherein said second control loop comprises a differential amplifier providing an output which is the differential of the electrical outputs of said third and fourth light-sensitive areas, and a comparator for comparing the output signal from said differential amplifier with a reference voltage, the output from said comparator controlling the speed of a motor for pulling said crystal.

Claim 18

Dependent Claim 48 words

The system defined in claim 14 further comprising a temperature control loop including a further comparator also for comparing the output from said differential amplifier with a further reference voltage, the output from said further comparator controlling means for heating said melt thereby to control the melt temperature.

Claim 19

Dependent Claim 94 words

The system defined in claim 3 wherein said first and second light-sensitive areas are each generally rectangular in shape and of substantially the same area, and said third and fourth light-sensitive areas together define a total area of generally rectangular shape located between the first and second light-sensitive areas, said third and fourth light-sensitive areas being adjacent and separate along said second axis with the adjacent edges thereof defining a serpenture path extending generally along said first axis whereby respective portions of said third and fourth areas are interdigitated and overlie said first axis.

Claim 20

Dependent Claim 47 words

The system defined in claim 16 wherein said sensing means is adapted to receive said image with the center of the image generally located at the intersection of said axes with portions of the image overlying respective portions of said first, second, third and fourth light-sensitive areas.

Claim 21

Independent Claim 204 words

A system for controlling the diameter of a pulled crystal comprising: a. means for directing a beam of light on a preselected area of the meniscus of a melt formed by a crystal being pulled from the melt; b. first light sensing means for receiving the image caused by reflection of the light beam from the meniscus, said first sensing means being responsive to positional variations of the image along a first axis caused by change in the melt level; c. second light sensing means for receiving said image and responsive to positional variations of the image along a second axis caused by variations in the diameter the crystal being pulled, the positional variations being substantially independent of positional variations along the first axis; d. a first servo loop interconnected with said first sensing means and including a sevomotor operable for maintaining a predetermined distance between said first and second sensing means and said preselected area of the meniscus; and e. a second servo loop interconnected with said second light sensing means and operative to provide servo control of the speed of a motor for pulling the crystal whereby the diameter of the crystal is precisely controlled regardless of changes in the melt level.

Claim 22

Independent Claim 204 words

A system for controlling the diameter of a pulled crystal comprising: a. means for directing a beam of light on a preselected area of the meniscus of a melt formed by a crystal being pulled from the melt; b. first light sensing means for receiving the image caused by reflection of the light beam from the meniscus, said first sensing means being responsive to positional variations of the image along a first axis caused by change in the melt level; c. second light sensing means for receiving said image and responsive to positional variations of the image along a second axis caused by variations in the diameter the crystal being pulled, the positional variations being substantially independent of positional variations along the first axis; d. a first servo loop interconnected with said first sensing means and including a sevomotor operable for maintaining a predetermined distance between said first and second sensing means and said preselected area of the meniscus; and e. a second servo loop interconnected with said second light sensing means and operative to provide servo control of the speed of a motor for pulling the crystal whereby the diameter of the crystal is precisely controlled regardless of changes in the melt level.

Claim 23

Dependent Claim 78 words

The system defined in claim 18 further comprising a light source of controllable light output for providing said light beam, and a third servo loop interconnected with at least one of said sensing means and operative to provide servo control of said light output as a function of the amount of light received by the sensing means, whereby compensation is provided for variations in the amount of light received by the sensing means occurring during crystal pulling, and

Claim 24

Dependent Claim 31 words

The system defined in claim 18 further comprising a chopper for chopping the light beam and demodulator means interconnected with each of the light sensing means for deriving d.c. signals therefrom.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1976-06-18	1976-12-18	1977-06-19	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1980-06-18	1980-12-18	1981-06-19	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1984-06-18	1984-12-18	1985-06-19	$7700.00	Window Closed / Lapsed

Electroptical system and method for sensing and controlling the diameter and melt level of pulled crystals

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