Dual-bed scanner with reduced transport time

• US 5,668,630 A
• Filed: 06/27/1996
• Issued: 09/16/1997
• Est. Priority Date: 05/05/1995
• Status: Expired due to Term

• Current Assignee: Rudolph Technologies Incorporated (Onto Innovation Inc.)
• Original Assignee: Robotic Vision Systems, Inc. (Omron Corporation)
• Inventors: Bilodeau, Steven J., Yonescu, William E.
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): MERLINO, AMANDA H
• Application Number:
  US08/671,065
• Time in Patent Office: 446 Days
• Field of Search: 356/237, 348/94, 348/95, 348/86, 348/87, 348/125-134, 73/865.8, 193/346.2, 193/488.8, 209/587, 209/522, 209/576, 209/577
• US Class Current: 356/237.5
• CPC Class Codes: B07C 5/36 Sorting apparatus characterised by the means used for distribution sorting according to destination B07C3/003, B07C3/02

Abstract

A scanning system inspects elements, such as ICs, continuously by positioning a second tray containing elements to be inspected adjacent a scan bed in which the elements in a first tray are being scanned. Immediately upon completion of scanning of elements in the first tray, scanning begins on elements in the second tray. During scanning of the second tray, the first tray is off loaded, and a third tray replaces the first tray. The cycle is repealed continuously. Since transport and scanning operations take place simultaneously, transport delay is reduced substantially, as compared to the serial system of the prior art. When the transport, positioning, and off loading operations consume substantially less time than the scanning operation, a fresh tray of elements always awaits scanning upon completion of scanning of elements in a tray. In one embodiment, first and second scan beds are elevated above a conveyor, thereby permitting incoming and outgoing trays to pass on the conveyor below the scan beds without interference with the trays elevated in the scan beds. A replace operation, either on-line or off-line, replaces defective elements detected in the scanned trays with known-good elements, whereby the output of the apparatus is 100 percent known-good elements. An embodiment in which transport and positioning takes longer than the scanning operation, thereby requiring a delay in scanning, is disclosed. This latter embodiment, although it does not provide continuous scanning, nevertheless reduces cycle time by virtue of parallel operation of scanning and transport functions.

Claims

1. A method for scanning elements in a plurality of pocketed trays with an optical sensor, comprising:

moving a first pocketed tray of said plurality of pocketed trays containing said elements into an operable position with said optical sensor;

moving said optical sensor in a pattern for scanning said elements;

moving a second pocketed tray of said plurality of trays containing said elements toward a position adjacent said first pocketed tray while said optical sensor is performing said pattern over said first pocketed tray;

scanning elements in said pattern over said second pocketed tray upon completion of said pattern over said first pocketed tray, whereby said optical sensor is enabled to continue scanning with reduced transport delay.

2. A method for scanning elements in a plurality of pocketed trays, comprising:

positioning a first pocketed tray of said plurality of pocketed trays in a first scan bed;

scanning said elements in said first pocketed tray;

positioning a second pocketed tray of said plurality of pocketed trays in a second scan bed adjacent said first scan bed while said scanning is being performed;

beginning scanning of elements in said second pocketed tray in said second scan bed upon completion of said scanning said elements in said first pocketed tray, whereby transport delay between scanning said elements in said first and second pocketed trays is reduced;

transporting a scan-completed pocketed tray to an off-load position; and

avoiding interference between a pocketed tray in transit to its scan bed and a pocketed tray in its scan bed, and between a pocketed tray on its way to said off-load position and a pocketed tray in its scan bed.

3. A method according to claim 2, wherein the step of avoiding includes positioning said first and second scan beds out of alignment with travel paths of pocketed trays to and from said scanning steps, whereby pocketed trays being transported are enabled to pass pocketed trays in said scan beds.

4. A method for continuous scanning of elements in a plurality of pocketed trays, comprising:

positioning a first pocketed tray of said plurality of pocketed trays in a first scan bed;

scanning elements in said first pocketed tray;

positioning a second pocketed tray of said plurality of pocketed trays in a second scan bed, while scanning is being performed on said first pocketed tray;

beginning scanning elements in said second pocketed tray after completion of scanning elements in said first pocketed tray;

transporting said first pocketed tray to an off-load position while scanning of said second pocketed tray is being performed;

positioning a third pocketed tray of said plurality of trays in said first scan bed before completion of scanning of elements in said second pocketed tray, whereby scanning of said elements in said third pocketed tray is enabled to begin upon completion of scanning of elements in said second pocketed tray; and

transporting said second pocketed tray to said off-load position while scanning of said third pocketed tray is being performed, whereby scanning with reduced transport delay is enabled.