SCANNER THAT CONTROLS STEPPING MOTOR TORQUE

• US 20020079858A1
• Filed: 12/21/2000
• Published: 06/27/2002
• Est. Priority Date: 12/21/2000
• Status: Active Grant

• Current Assignee: Diversified Observation LLC (IPValuation Partners, LLC)
• Original Assignee: Mustek Systems Incorporated
• Inventors: Chang, Te-Chih
• Granted Patent: US 6,414,461 B1
• Time in Patent Office: Days
• US Class Current: 318/696
• CPC Class Codes: H04N 1/0402 Scanning different formats; Scanning with different densities of dots per unit length, e.g. different numbers of dots per inch (dpi); Conversion of scanning standards H04N1/00283 takes precedence; picture signal circuits for modification of image resolution H04N1/3935, H04N1/40068
• CPC Class Codes: H04N 1/0414 in the sub scanning direction
• CPC Class Codes: H04N 1/0443 Varying the scanning velocity or position
• CPC Class Codes: H04N 1/0455 using a single set of scanning elements, e.g. the whole of and a part of an array respectively for different formats
• CPC Class Codes: H04N 1/1013 with sub-scanning by translatory movement of at least a part of the main-scanning components H04N1/107 takes precedence
• CPC Class Codes: H04N 2201/04755 by controlling the position or movement of a scanning element or carriage, e.g. of a polygonal mirror, of a drive motor

Abstract

A scanner has a housing, a scanning module for scanning a document, a driving module for driving the scanning module, and a control circuit for controlling the scanner. The driving module comprises a stepping motor for driving the scanning module forward and backward so that the scanning module is able to scan the entire area of the document. The control circuit controls the stepping motor to generate different torque so that the scanning module can scan the document at different speeds.

Claims

1. A scanner comprising:

a housing having a transparent platform, a document to be scanned being placed on the transparent platform;

a scanning module movably installed inside the housing for scanning the document;

a driving module installed inside the housing for driving the scanning module, the driving module comprising a stepping motor for driving the scanning module forward and backward so that the scanning module scans the document; and

a control circuit for controlling the operations of the scanner,

wherein the control circuit controls the stepping motor to generate different torque so that the scanning module scans the document at different speeds.

2. The scanner of claim 1 wherein the driving module further comprises a motor driving circuit, the control circuit outputting a driving signal to the motor driving circuit so that the stepping motor generates a torque according to the driving signal.

3. The scanner of claim 2 wherein the control circuit comprises a memory, the memory storing a torque table and a driving program, the torque table recording a plurality of torque values, each of the torque values corresponding a predetermined condition when the stepping motor produces the corresponding torque, and the driving program chooses one of the torque values according to the predetermined condition, the motor driving circuit receiving the corresponding driving signal according to the torque value chosen by the driving program.

4. The scanner of claim 3 wherein the control circuit comprises a processor and a digital to analog (D/A) converter, the processor being used to execute the driving program, the D/A converter being used to convert a digital signal received from the processor to an analog driving signal, the analog driving signal being transmitted to the motor driving circuit, and the driving program transmits the torque value to the D/A converter, the D/A converter then transmitting the analog driving signal to the motor driving circuit.

5. The scanner of claim 4 wherein the control circuit further comprises a register for storing the torque value chosen by the driving program, and the D/A converter converts the torque value stored in the register to the corresponding analog driving signal.

6. The scanner of claim 1 wherein the control circuit controls the current of the stepping motor so that the stepping motor generates different torque.

7. The scanner of claim 1 wherein the control circuit controls the stepping motor to generate different torque according to a resolution that the scanning module uses when scanning the document.

8. The scanner of claim 7 wherein a higher resolution used by the scanning module requires a lower torque generated by the stepping motor.

9. The scanner of claim 7 wherein a lower resolution used by the scanning module requires a higher torque generated by the stepping motor.