Image forming apparatus including position detector

• US 20070086679A1
• Filed: 10/17/2006
• Published: 04/19/2007
• Est. Priority Date: 10/17/2005
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Kudo, Koichi, Takayama, Hideyuki
• Granted Patent: US 8,027,516 B2
• Time in Patent Office: Days
• US Class Current: 382/294
• CPC Class Codes: H04N 1/506 Reproducing the colour component signals picture-sequentially, e.g. with reproducing heads spaced apart from one another in the subscanning direction

Abstract

An image forming apparatus includes a movable member that moves cyclically in synchronization with an image forming process and a position detector. The position detector includes a scale, an image sensor, a signal processor, and a position computing unit. The scale is attached to the movable member and includes a plurality of optical marks formed in line at a substantially constant interval. The image sensor captures data relating to at least one optical mark at a time. The signal processor computes a coordinate of the optical mark with respect to a reference position. The position computing unit computes a distance traveled by the optical mark based on a number of the optical marks that pass the reference position and the coordinate of the optical mark with respect to the reference position.

Claims

1. An image forming apparatus, comprising:

a movable member configured to move cyclically in synchronization with an image forming process; and

a position detector comprising;

a scale attached to the movable member and including a plurality of optical marks formed in line at a substantially constant interval,

an image sensor configured to capture data relating to at least one of the plurality of optical marks at a time,

a signal processor configured to determine a coordinate of an optical mark with respect to a reference position using the data captured by the image sensor, and

a position computing unit configured to compute a distance traveled by the optical mark based on a number of the optical marks that pass the reference position and the coordinate of the optical mark with respect to the reference position.

2. The image forming apparatus according to claim 1, wherein the plurality of optical marks have a predetermined difference in reflectance or transmittance from a base material of the scale.

3. The image forming apparatus according to claim 1, wherein the image sensor comprises an optical system configured to capture data relating to at least two of the plurality of optical marks at a time.

4. The image forming apparatus according to claim 3, wherein the position computing unit is configured to compute an interval of the plurality of optical marks based on the data captured by the image sensor, and correct the distance traveled by the optical mark based on the computed interval of the plurality of optical marks.

5. The image forming apparatus according to claim 1, comprising:

a plurality of image sensors provided along the moving direction of the scale;

wherein the signal processor computes the coordinates of the plurality of optical marks with respect to reference positions, based on data captured by the respective image sensors, and

the position computing unit corrects an error in the interval of the plurality of optical marks and computes a distance traveled by the scale based on the number of the optical marks that pass the reference position and the respective coordinates of the plurality of optical marks.

6. The image forming apparatus according to claim 1, wherein the position detector comprises:

an optical system configured to relay images of the plurality of optical marks from different portions of the scale on an image sensor, and

wherein the image sensor is configured to read the plurality of optical marks from different portions of the scale.

7. The image forming apparatus according to claim 1, wherein the image sensor is a two-dimensional image sensor, and the plurality of optical marks are arranged in two dimensions in the scale.

8. A position detector, comprising:

a scale attached to a movable member and including a plurality of optical marks formed in line at a substantially constant interval;

an image sensor configured to capture data relating to at least one of the plurality of optical marks at a time;

a signal processor configured to determine a coordinate of an optical mark with respect to a reference position using the data captured by the image sensor; and

a position computing unit configured to compute a distance traveled by the optical mark based on a number of the optical marks that pass the reference position and the coordinate of the optical mark with respect to the reference position.

9. A travel detector for detecting a rotation speed and a position of a rotationally movable member, comprising:

a scale attached to a rotationally movable member and including a plurality of optical marks formed in line at a substantially constant interval;

an image sensor configured to capture data relating to at least one of the plurality of optical marks at a time;

a signal processor configured to determine a coordinate of an optical mark with respect to a reference position using the data captured by the image sensor; and

a position computing unit configured to compute a distance traveled by the optical mark based on a number of the optical marks that pass the reference position and the coordinate of the optical mark with respect to the reference position.