JP2567958B2 - Facsimile original reading device - Google Patents

Description

The present invention relates to a document reading device for a facsimile,
In particular, the present invention relates to a facsimile original reading device that binarizes an image signal.

[Conventional technology]

Conventionally, the binarization circuit of the document reading apparatus for this type of facsimile has been operated to set the peak value limit only once before reading the document.

[Problems to be Solved by the Invention]

The binarization circuit of the above-mentioned conventional document reading apparatus for facsimile has a setting operation for setting the peak value limit once before reading the document. Therefore, as shown in FIG. Since the amount of light increases during the period from the cold state to the stable state, the peak value limit set before reading is too small and the peak value limit and the black level are reversed, as shown in FIG. 4 (c). At the point where the peak value reaches the peak value limit, the black side of the binarized slice level cannot be secured, and there is a drawback that continuous black signals are binarized as a white level.

[Means for solving the problem]

A facsimile document reading apparatus according to the present invention includes a peak value detection circuit that detects a white level peak value of an image signal read from a document that is transmitted at predetermined intervals, and a peak value detection circuit that approaches the black level. A peak value limit setting circuit that changes the limiting peak value limit according to the output level of the image signal, and sets the peak value limit value when the detected peak value is closer to the black level than the peak value limit. A peak value setting circuit, a binarized slice level setting circuit that sets a reference slice level when the set peak value is divided and binarized, and the image signal and the binarized slice level are compared. And a comparator that outputs the binarized data of the image signal.

〔Example〕

Next, the present invention will be described with reference to the drawings. First
The figure is a block diagram of one embodiment of the present invention.

The image signal 8 read by the reading circuit 1 is the peak value 10 of the image portion within the range defined by the peak value detection section signal 9 by the peak value detection circuit 2 and the overall peak value by the peak value detection circuit 3. 11 is detected. When the overall peak value becomes large, the peak value limit setting circuit 4 updates the peak value limit 12. The peak value setting circuit 5 sets the peak value 10 of the image portion as the peak value. When the peak value is closer to the black level than the peak value limit, the peak value limit is set as the peak value.

The binarized slice level setting circuit 6 divides the set peak value 13 and sets the slice level at which black and white are recognized. The comparator 7 compares the image signal 8 with the slice level 14 and outputs the binarized data of the image signal.

FIG. 2 is a flow chart for explaining the operation of the peak value limit setting circuit 4 of FIG. In step 21, the peak value P is read, and in step 22, it is compared with the previous peak value P '. If the peak value P becomes larger than P', the peak value limit setting is updated in steps 23 to 25. To do. This operation is performed in step 26 at predetermined intervals of 1 second.

FIG. 3 shows the change in the amount of light after the fluorescent lamp is turned on. There is a large change in the amount of light at point A immediately after lighting and point B approaching a stable state.

FIGS. 4 (a) and 4 (b) are waveform diagrams of the image signal when scanning the all black screen at points A and B in FIG.

FIG. 4 (a) shows the waveform of the image signal immediately after the fluorescent lamp is turned on. Reference numeral 41 is a peak value of the image signal, which is a value detected in the peak value detection section of 44. Since there is no white level in the peak value detection section 44, the peak value 41 is white level 45 as the original is scanned.
Changes gradually from the black level 46 of the manuscript. The total peak value 42 is the peak value detected including the shading portion of the white line. 43 is a peak value limit, and the peak value 41 of the image signal can approach the black level up to this value.

FIG. 4 (b) shows the waveform of the image signal when the fluorescent lamp warms and the amount of light increases. Since the amount of light is increased, the amplitude is increased and the overall peak value 42 is increased. in this way,
When the overall peak value becomes large, the peak value limit is set to be a predetermined ratio between the black level and the white level.

〔The invention's effect〕

As described above, the present invention updates the peak value limit according to the magnitude of the output of the image signal, and always sets the peak value limit to a predetermined ratio between the black level and the white level, thereby obtaining the fluorescence. When the lamp warms and the amount of light changes, the black width of the binarized slice level can be secured even if the peak value follows the peak value limit.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG.
FIG. 3 is a flowchart for explaining the operation of the peak value limit setting circuit in FIG. 3, FIG. 3 is a correlation diagram showing a change in the light amount after the fluorescent lamp is turned on, and FIGS. B
FIG. 4C is a waveform diagram of the image signal at the point, and FIG. 4C is a waveform diagram of the image signal when the peak value limit is fixed in the conventional example. 1 ... reading circuit, 2,3 ... peak value detection circuit, 4 ...
… Peak value limit setting circuit, 5 …… Peak value setting circuit, 6 …… Binarization slice level setting circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Watanabe Mitsuru 3-30-4 Nishi-Shimbashi, Minato-ku, Tokyo NEC Engineering Co., Ltd. (56) References JP-A-60-241372 (JP, A) )

Claims (1)

(57) [Claims] 1. A peak value detection circuit for detecting a white level peak value of an image signal read from an original transmitted at a predetermined interval, and a peak value limit for restricting the peak value from approaching a black level. And a peak value limit setting circuit for varying the value according to the output level of the image signal, and a peak value setting circuit for setting the peak value limit value when the detected peak value is closer to the black level than the peak value limit. , A binarized slice level setting circuit for setting a slice level as a reference when the set peak value is divided to be binarized, and the image signal and the binarized slice level are compared to each other. An original reading device for a facsimile, comprising a comparator for outputting digitized data.