CMOS sensor camera with on-chip image compression

• US 6,954,231 B2
• Filed: 12/17/2001
• Issued: 10/11/2005
• Est. Priority Date: 05/05/1998
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Mahant-Shetti, Shivaling S.
• Primary Examiner(s): Garber, Wendy R.
• Assistant Examiner(s): NGUYEN, LUONG TRUNG
• Application Number:
  US10/022,995
• Publication Number:
  US 20020085110A1
• Time in Patent Office: 1,394 Days
• Field of Search: 348/294, 348/301, 348/302, 348/308, 348/312, 708/820, 708/821, 257/222, 341/155, 250/208.1
• US Class Current: 348/312
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• CPC Class Codes: H04N 25/51 Control of the gain
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

A digital camera (10) that has an array (11) of CMOS sensor elements (11a). The array (11) is read in a manner that performs spatial-to-frequency transforms for image compression on the analog output signals of the sensor elements. More specifically, wordlines (12) and bitlines (13) are pulsewidth modulated so that the coincidence of their “on” times corresponds to a desired coefficient of the basis function of the transform (FIGS. 3 and 4). Additional comparator circuitry (15), quantizers (16), and encoding circuitry (19) can be part of the same integrated circuit as the array (11).

Claims

1. A method of providing pulsewidth modulated bitline and wordline signals for performing spatial to frequency transforms of analog signals from sensor elements of a CMOS sensor array, said transform being characterized by a basis function, comprising the steps of;

dividing a wordline period into intervals, such that each interval has an accumulated pulsewidth corresponding to a coefficient of said basis function, thereby providing a pulsewidth modulated wordline signal; and

dividing a bitline period into said intervals and into subintervals, such that each subinterval of each interval has an accumulated pulsewidth corresponding to a coefficient of said basis function.

2. The method of claim 1, wherein said transform is a discrete cosine transform.

3. The method of claim 1, wherein said transform is a discrete articulated trapezoid transform.

4. The method of claim 2, wherein:

said step of dividing the wordline period into intervals includes dividing a wordline period T into eight intervals of duration Tcos(n×

11.25), where n is an integer 0, 1, 2, 3, 4, 5, 6 or 7.

5. The method of claim 1, wherein:

said step of dividing the wordline period into intervals includes dividing a wordline period T into intervals t0=0, t1=0.19T, t2=0.38T, t3=0.55T, t4=0.71T, t5=0.83T, t6=0.92T, and t7=T.

6. The method of claim 5, wherein:

said step of dividing the wordline period into intervals and into subintervals includes

dividing an interval t1−

t0 into subintervals t11=0.19(t1−

t0), t12=0.38(t1−

t0), t13=0.55(t1−

t0), t14=0.71(t1−

t0), t15=0.83(t1−

t0), t16=0.92(t1−

t0) and t17=(t1−

t0),

dividing an interval t2−

t1 into subintervals t21=0.19(t2−

t1), t22=0.38(t2−

t1), t23=0.55(t2−

t1), t24=0.71(t2−

t1), t25=0.83(t2−

t1), t26=0.92(t2−

t1) and t27=(t2−

t1),

dividing an interval t3−

t2 into subintervals t31=0.19(t3−

t2), t32=0.38(t3−

t2), t33=0.55(t3−

t2), t34=0.71((t3−

t2), t35=0.83(t3−

t2), t36=0.92(t3−

t2), and t37=(t3−

t2),

dividing an interval t4−

t3 into subintervals t41=0.19(t4−

t3), t42=0.38(t4−

t3), t43=0.55(t4−

t3), t44=0.71(t4−

t3), t45=0.83(t4−

t3), t46=0.92(t4−

t3) and t47=(t4−

t3),

dividing an interval t5−

t4 into subintervals t51=0.19(t5−

t4), t52=0.38(t5−

t4), t53=0.55(t5−

t4), t54=0.71(t5−

t4), t55=0.83(t5−

t4), t56=0.92(t5−

t4) and t57=(t5−

t4),

dividing an interval t6−

t5 into subintervals t61=0.19(t6−

t5), t62=0.38(t6−

t5), t63=0.55(t6−

t5), t64=0.71(t6−

t5), t65=0.83(t6−

t5), t66=0.92(t6−

t5) and t67=(t6−

t5),

dividing an interval t7−

t6 into subintervals t71=0.19(t7−

t6), t72=0.38(t7−

t6), t73=0.55(t7−

t6), t74=0.71(t7−

t6), t75=0.83(t7−

t6), t76=0.92(t7−

t6) and t77=(t7−

t6).

7. The method of claim 3 wherein:

said step of dividing the wordline period into intervals includes dividing a wordline period 10T into intervals t0=0, t1=2T, t2=4T, t3=6T, t4=7T, t5=8T, t6=9T, and t7=10T.