EXHIBIT 1021
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`J. D. PLUMMER and J. D. MEINDL, “A Low Light Level Self-Scanned MOS
`
`Image Sensor,” ISSCC72, Feb. 1972
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`TRW Automotive U.S. LLC: EXHIBIT 1021
`PETITION FOR INTER PARTES REVIEW
`OF U.S. PATENT NUMBER 8,599,001
`IPR2015-00436
`
`

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`minimized by appropriate processing steps during the fabrication
`of the devices and are technology limited at the present time.
`The switching transients caused by the turning on and off of
`the row and bit switches
`are eliminated from the array
`output
`through two separate techniques. Figure 2 illustralcs the use of a
`charge integrator through which the bit switching transients are
`eliminated. These transients are removed by strobing the output
`of the integrator after the bit switch has been turned
`on and
`then off. In this way, the transient charge coupled through C G ~
`to the integrator on the leading edge of the bit sample pulse is
`exactly cancelled by the transient
`charge coupled to the
`integrator on the
`trailing edge of the bit sample
`pulse. The
`output from the integrator
`remaining after this
`cancelling
`process is due only to ihmination of the particular photodiode
`being sampled.
`The row switching transients which are equally as important
`as the bit switching transients, are removed by modifying slightly
`the row scanning timing as illustrated in Figure 3. Use is made of
`the parasitic mlnmn capacitance Cc for temporary storage of
`the photodiode information. Between to and tl,the information
`on the first TOW of photodiodes is transferred from CD to &.
`The TOW switches in this row are then turned off, removing the
`from @&: before the bit switches
`transient switching charge
`are
`energized. After the charge transfer process is completed at tl,
`the charge remaining on C&: is due only
`to photodiode
`illumination current and not to row switching transients coupled
`to Cc through the row CGD.
`k i photomicrograph of a self-scanned hfos retina using these
`signal processing and scanning techniques is shown in Figure 4.
`The array is fabricated on a chip 1.8 x 2.5 mm with the unit cell
`the array being 150 by 300 p. The array is designed to
`size in
`operate with a single two phase clock and one de power supply.
`All of the scanning shift registers on
`the chip are two phase
`dynamic circuits which consume less than 0.1 mW per stage at
`typical operating frequencies.
`These arrays have been shown
`experimentally to exhibit no pattern noise in their outputs due
`are in fact limited in the light
`to switching transients and they
`levels they can detect only by the thermal
`leakage currents of
`the photodiodes themselves. Blackbody (2854°K) radiation levels
`well below 1 pW’/cm2 at room temperature
`have been reliably
`-
`*Optacon
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`I ---
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`ROW 2
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`WAM 2.5: A b o ~ - b i g h t - L ~ e l S e
`J. D. Plummer and J. D. Meindl
`Stanford University
`
`Stanford. Cal.
`
`converter* is a direct translation
`THE OPTICAL-TO-TACTILE
`reading aid for the blind developed at Stanford University I. On
`a letter-by-letter basis this system provides for the blind reader
`of an ordinary
`images of the printed characters
`exact tactile
`book, newspaper, or magazine. A monolithic
`silicon retina is
`used to sense the information on the printed page. In the present
`version, approximately half of the system power
`is used
`in a
`tungsten bulb to provide illumination of the printed material. To
`enhance battery lifetime in the system, image sensor operation at
`low light levels is clearly desirable.
`In addition to providing low light level operation, MOS image
`sensing arrays offer the advantage of self-scanning-a feature that
`is not easily obtainable ivith bipolar image sensors. The simplest
`type of self-scanned MQS image sensing array is shown schemat-
`1. The elements in the
`image-sensing array are
`ically in Figure
`operated in the charge storage mode 2 in which each
`element
`integrates the light falling on it over a frame time.
`Arrays such as this will, of course, exhibit nonuniformities in
`their outputs. In general, the pattern of this nonuniformity will
`be specific to each individual array. The term fixed pattern noisc
`or FPN 3 has been used to characterize these nonuniformitics.
`By definition, FPN is the peak-to-peak variation in the
`outputs
`produced by the elements in an
`array under either zero
`or
`uniform illumination.
`There are two p r i m q sources of FPN in the output signal
`1. During the
`produced by an
`array such as the one in Figure
`scanning of
`the array, switching transients
`are capacitively
`coupled to the array output line primarily
`through the gate-to-
`drain capacitances, CGD, of the row and bit switches. It will be
`these sources of FPN can bc completely
`shown shortly that
`eliminated by appropriate signal processing.
`Once the switching transients are eliminated from the array
`output, FPN will still be present due to variations in the thermal
`the photodiodes and due to
`leakage currents and responsivity of
`variations in the charge pumping currents
`in the row and bit
`sampling switches. These sources
`of pattern noise may be
`
`1 Brugler, J.S., Meindl, J.D., Plummer, J.D., Salsbury, P.J. and
`Young, W.T., “Integrated Electronics for a Reading Aid for the
`Blind”, IEEE J. Solid State Circuits, P. 304-312; Dec., 1969.
`Weckler, G.P., “Operation of PN Junction Photodetectors in
`a Photon Flux Integration Mode”, JEEE J. Solid-State Circuits,
`p. 65-73; Sept., 1967.
`3 Fry, P.W., Noble, P.J.W. and Rycroft, R.J., “Fixed Pattern
`Noise in Photomatrices”,
`IEEE h Solid-state Circuits, p.
`250-254; Oct., 1970.
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`1021-001
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`

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`use, These light levels
`detected in testing the arrays for future
`correspond to illumination currents in the photodiodes of about
`10 to 20 PA.
`The improved performance of these MOS retinas has been
`obtained with no
`increase in the complexity of the array unit
`cell-a single MOS phototransistor-and only a
`slight increase in
`the complexity of the scanning circuitry. In the block diagram of
`5, a four-stage sequence
`the image sensor shown in Figure
`register is used to establish the basic four-step interrogation
`charge integrator. A three-stage bit select
`sequence for the
`register is used
`to gate the sample output command of the
`sequence register to each column of the array in order. The row
`scanning register is used to turn on eight row transfer switches in
`sequence. At a set time during each row
`pulse, a command to
`transfer charge from CD to Cc is gated through one of the row
`transfer switches to the image sensing array. Only the two phase
`clock for the sequence register need be supplied externally.
`It is anticipated that the use of these new retinas will greatly
`enhance the utility of this reading aid for the blind.
`
`B I T
`SWITCH
`?
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`T R E S E T
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`SWITCH 7
`u u
`RESET 7
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`ROW
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`B I T
`SWITCH
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`n
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`Av
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`g=0
`AMPLIFIER
`OUTPUT
`VOLTAGE
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`FIGURE 2-Circuitry
`transient cancellation.
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`required to accomplish bit switching
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`: q q
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`ROW 2
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`I
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`'3
`'0
`'2
`'1
`FIGURE 3-New array scanning technique to eliminate row
`switching transients.
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`FIGURE 4-Monolithic image sensor with cancelled row and
`bit switching transients.
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`+IV 0 9 2
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`r-zz+=(
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`I
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`,.,n
`TIMING
`CIRCUITRY
`
`SEQUENCE
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`3 STAGE
`BIT SELECT REGISTER
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`
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`I
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`REGISTER
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`S
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`3 x 8
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`PHOTOTRANSISTOR
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`ARRAY
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`U I
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`I
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`FIGURE 5-Simplified Mock diagram of image sensor with
`cancelled row and bit switching transients.
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`1021-002