JP2946614B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image reading using a photoelectric conversion element, and more particularly, to an image input device that is a peripheral device of a computer.

2. Description of the Related Art An image reading device is used as a means for inputting image information to an information processing device such as a PC.

The image reading apparatus irradiates an original with a light source such as a fluorescent lamp or a halogen lamp, and forms a light / dark pattern of the original on a photoelectric conversion element to convert the original into an electric signal. Generally, a fixed-document type image reading device mechanically drives a relatively large reading head equipped with a light source and an optical system, so that it can be operated at a constant speed especially when a step motor is used. desirable. However, since the read data must be received by a host such as a PC, the reading speed may be determined by the data transfer time. Therefore, a constant buffer memory is provided inside the reading device, and the reading head is driven at an optimum speed until the buffer memory is full.
In the case of this reading device, when the buffer memory is full, the light source is turned off and the reading operation is stopped. Then, data transfer is performed to the host PC, and when the buffer memory becomes empty, the reading operation is started again.

[Problem to be Solved by the Invention] In the above-described conventional reading apparatus, when the buffer memory is emptied and the reading operation is restarted, first, the light source is turned on, and reading is started after this light amount is stabilized.

The time required for this light source to stabilize varies depending on the type of light source, but is generally less than 1 second for a rare gas discharge lamp, 1-2 seconds for a halogen lamp, and 2 to 5 seconds for a mercury fluorescent lamp. Cost. Therefore, this is a major obstacle from the viewpoint of improving the performance of the apparatus, that is, to shorten the reading time (to increase the reading speed). An object of the present invention is to overcome such a drawback, and an object of the present invention is to improve a reading speed by eliminating a time loss at the time of restarting in a reading apparatus which repeatedly stops and restarts the reading operation as described above.

[Means for Solving the Problems] An image reading apparatus of the present invention has a buffer memory for temporarily storing read data of an image document, and suspends and resumes a read operation in accordance with the remaining amount of data that can be stored in the buffer memory. When the remaining amount of the buffer memory is equal to or less than a predetermined value, a reading head is stopped, a light source for illuminating the image document is turned off, and the reading operation is temporarily stopped. When the remaining amount becomes equal to or more than a first threshold value, the light source is turned on. When the remaining amount in the buffer memory becomes equal to or more than a second threshold value, the read head is operated to restart the reading operation. It is characterized by the following.

FIG. 1 shows a control flow chart of the present invention. In this embodiment, 1
The data (m bytes) for the main scan is handled as the minimum unit.
First, the remaining amount of the buffer memory is checked, and reading is performed until the memory is exhausted. When the remaining memory capacity is less than one line, the lamp is turned off to stop reading, and data is output until the remaining memory capacity increases.

When the remaining capacity of the memory exceeds the first threshold value a1 byte, the lamp is turned on, and the output of data is continued. When the remaining capacity of the memory exceeds the second threshold value a2, the reading operation is started again. The reading is ended by repeating the above.

FIG. 2 shows a conceptual diagram of the reading device. In this embodiment, the read head 20 is a rare gas discharge lamp 2 of three colors of red, green and blue.
1, 22 and 23, an image sensor CCD 26, an imaging lens 25, and a mirror 24 for guiding reflected light from a document 28 placed on a document table 27 to the lens 25. Reflected light from the original
The document is converted into an electric signal by the CCD (main scanning), and the original is read by moving the reading head 20 right and left on the page (sub scanning). FIG. 3 shows a circuit block of this embodiment. CCD3
The image signal from 1 is converted into an 8-bit digital signal by an AD converter 33 through an amplifier 32. Data that has been subjected to shading correction, binarization, and other processing is temporarily stored in the memory 36. On the other hand, the image data stored at the same time is output to the outside via the interface unit 39. If the external output speed is lower than the reading speed, the memory 36 overflows, and it is necessary to stop reading.

FIG. 4 shows this state. The horizontal axis represents time, (a) shows the conventional state, and (b) shows the state transition according to the present invention. Conventionally, when reading is restarted due to an increase in the remaining amount of memory, a lamp is first turned on, and reading is performed after waiting for time t0. However, according to the present invention, since the lamp is already lit before the remaining memory capacity becomes a2 bytes, reading can be resumed without waiting time.

In the present invention, the timing of turning on the lamp in advance is determined based on the remaining amount of the memory. However, the same effect can be obtained by managing the time in consideration of the communication state with the external host.

[Effects of the Invention] The present invention has the effect of reducing the reading time as a whole without increasing the apparatus cost.

[Brief description of the drawings]

FIG. 1 is a flowchart of an embodiment of the present invention. FIG. 2 is a conceptual diagram of an embodiment of the reading device. Read head 20 Light source: red 21 Light source: green 22 Light source: blue 23 Mirror 23 Imaging lens 25 CCD image sensor 26 FIG. 3 is a circuit block diagram of the present invention. It is a figure showing an example. FIG. 4 is a diagram showing the remaining amount of memory, the reading timing, and the control timing of the lamp in the present invention and the prior art.

Claims (1)

(57) [Claims] 1. An image reading apparatus, comprising: a buffer memory for temporarily storing read data of an image document; and temporarily suspending and resuming a read operation according to a remaining amount of data that can be stored in the buffer memory. When the remaining amount becomes equal to or less than a predetermined value,
Stopping a reading head, turning off a light source for illuminating the image document, temporarily suspending the reading operation, turning on the light source when the remaining amount of the buffer memory becomes equal to or greater than a first threshold value; The image reading apparatus according to claim 1, wherein when the remaining amount becomes equal to or more than a second threshold value, the reading head is operated to restart the reading operation.