JP2709117B2 - Optical scanning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] Regarding an optical scanning method for performing optical scanning using a one-dimensional array, an object of the present invention is to improve sensitivity in the sub-scanning direction without lowering sensitivity. In an optical scanning method of an image pickup apparatus that relatively moves a subject and scans in a sub-scanning direction to obtain a two-dimensional image, in an optical scanning method, a minute reciprocation of an optical path between the one-dimensional array and the subject is synchronized with a line cycle. Deflection means is provided so that scanning in the direction opposite to the sub-scanning direction is repeated at substantially the same speed as the sub-scanning.

[Industrial applications]

The present invention relates to an optical scanning method, and more particularly to an optical scanning method for performing optical scanning using an integral one-dimensional array.

A facsimile is an imaging device that obtains a two-dimensional image by scanning in the sub-scanning direction using an integral one-dimensional array in which photoelectric conversion units of a solid-state imaging device such as a charge-coupled device (CCD) are linearly arranged. Widely used for

In such an imaging apparatus, it is desired to improve the resolution in the sub-scanning direction.

[Prior Art] FIG. 4 shows a configuration diagram of an example of a conventional optical scanning system.
In the figure, reference numeral 11 denotes a CCD, which constitutes the integral type one-dimensional array. On the other hand, reference numeral 12 denotes a document, and characters, figures, and the like on the document 12 are subjects of the imaging apparatus. 13 is a mirror for changing the optical path, and the mirror itself is fixed. Reference numeral 14 denotes a focusing lens.

In the above configuration, the light reflected on the document 12 is incident on the mirror 13, is reflected there, changes the optical path, is focused by the lens 14, and is incident on the CCD 11. The CCD 11 performs an operation of a known solid-state imaging device, photoelectrically converts incident light, and sequentially combines images of each pixel such as a character string of one line on the document 12 in a certain direction in a time-series manner. Is output.

Here, in order to obtain a two-dimensional image, manuscript 1
2. One line of the upper image is sequentially synthesized in a fixed direction in time series (this scanning direction is referred to as a main scanning direction), while the original 12 is further moved in the direction of the arrow 15 or the original 12 is stopped. The optical system consisting of the CCD 11, lens 14, and mirror 13
Move in the opposite direction to 5. By this movement, the document 12 is sub-scanned in the direction of arrow 16 orthogonal to the main scanning direction.

This sub-scanning is normally performed at a constant speed such that the main scanning for one line can be performed after the main scanning for one line is completed. Output.

[Problems to be solved by the invention]

However, conventionally, the sub-scanning is usually performed at a constant speed, so that the image moves on the photoelectric conversion unit of the CCD 11 within the integration time. For this reason, especially at the time of high-speed scanning, a phenomenon occurs in which the resolution decreases in the sub-scanning direction due to this movement.

In order to prevent this, conventionally, the amount of movement within the signal reading time has been reduced by shortening the integration time of the CCD 11. However, this results in a decrease in sensitivity in the sub-scanning direction due to a short integration time, and the output image
There were problems such as deterioration of S / N.

Japanese Patent Application Laid-Open No. 63-101839 discloses a method for solving such a problem, as a linear array in which pyroelectric infrared devices are arranged in a line, an infrared optical system, and an infrared image scanning device. There is disclosed a configuration in which a reflecting mirror is provided, and the reflecting mirror scans in a direction perpendicular to the linear array in a panning scan and scans each fixed scan stepwise.

However, this configuration has a drawback that a very complicated scanning mechanism is required to scan the reflecting mirror in a stepwise manner while performing the scanning.

The present invention has been made in view of the above points, and has as its object to provide an optical scanning method capable of improving the sensitivity in the sub-scanning direction without lowering the sensitivity.

[Means for solving the problem]

The present invention relates to an optical scanning system of an imaging apparatus that relatively moves a one-dimensional array and a subject to scan in a sub-scanning direction to obtain a two-dimensional image. Means for minutely reciprocating deflection in synchronization are provided, and scanning is repeatedly performed in a direction opposite to the sub-scanning direction.

[Action]

Since the sub-scanning repeats returning to the original position after scanning the entire surface of one document at one frame period, the time is plotted on the horizontal axis and the scanning amount is plotted on the vertical axis. As shown, it changes in a sawtooth waveform at one frame period. In such an imaging apparatus, the present invention provides
Scanning is repeatedly performed in the direction opposite to the sub-scanning direction and at a period synchronized with the line period as shown by a solid line II in FIG. 1 (this scanning is referred to as "sub-scanning" for convenience).

Therefore, according to the method of the present invention in which the above-described sub-scan I and sub-sub-scan II are combined, the scan in the sub-scan direction is substantially performed in each line cycle as shown by the broken line III in FIG. The stopped scanning will be performed. Therefore, the same position can be imaged for a sufficient time even during high-speed scanning without shortening the integration time.

〔Example〕

FIG. 2 shows a configuration diagram of the first embodiment of the present invention. 4, the same components as those in FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted. In FIG. 2, reference numeral 20 denotes a rotating mirror, which is rotatable around a central axis 21. The mirror is small in size so that a fine reciprocating rotating operation can be repeatedly performed at high speed.
In addition, it has a lightweight configuration.

The above-mentioned minute reciprocating rotation operation is performed on the rotation mirror 20 by a known structure using a bimorph element, a piezo element, or the like.

Thus, for example, in an imaging apparatus that moves the document 12 in the direction of arrow 15 and performs sub-scanning in the direction of arrow 16, the turning mirror 20 moves the arrow 12 so as to track and scan the same one line 22 during most of the line period. Sub-scanning in 15 directions is performed,
The operation of returning to the original position just before the start of the next line period and reaching the next line is repeated every line cycle.

According to the present embodiment, the light from the document 12 incident on the CCD 11 becomes light from the same line in each line cycle, and even if the moving speed in the sub-scanning direction is high due to high-speed scanning, the sensitivity (resolution) ) Is not reduced.

Next, a second embodiment of the present invention will be described with reference to FIG. 3, the same components as those in FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted. In this embodiment, the optical path is not changed by the rotating mirror 20 as in the first embodiment. In an optical system in which the focusing lens 14 and the CCD 11 are linearly arranged above the document 12, the focusing lens 14 and the document A rotary transparent plate 23 is provided between the CCD 12 and the CCD 12, and the optical path between the CCD 11 and the document 12 is reciprocally minutely deflected in synchronization with the line cycle.

The rotating transparent plate 23 is configured to be rotatable about a shaft 24, and is made of a small and lightweight material. As in the first embodiment, a known piezoelectric element structure is used as a means for rotating the rotating transparent plate 23. For example, one end is attached to a side surface of the rotating transparent plate 23 that is orthogonal to the shaft 24. By vibrating the piezoelectric element structure up and down, it can be rotated.

According to the present embodiment, light from an image such as a character string for one line directly facing the rotating transparent plate 23 on the document 12 is configured to be incident on the CCD 11, so that the rotating transparent plate 23 The document side is rotated in the same direction as the moving direction 15 of the document 12 for approximately one line period at the same speed as the sub-scanning speed, and rotated to the original position immediately before the start of imaging of the next line. Let it return.

As a result, light from the same image of one line continues to be incident on the CCD 11 for substantially one line cycle, so that a step-like sub-scan can be realized as shown by the broken line III in FIG. . Accordingly, by associating the movement amount of the sub-scanning with the size of one pixel, there is a feature that the sensitivity (resolution) does not decrease at the time of high-speed scanning as in the first embodiment.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform a step-like sub-scan in which scanning in the sub-scan direction is substantially stopped in each line cycle, so that high-speed scanning can be performed without shortening the integration time. In addition, there is a feature that the resolution in the sub-scanning direction can be improved without lowering the sensitivity (resolution) in the sub-scanning direction.

In the present invention, the sub-scan is performed by moving either the optical system including the one-dimensional array or the original. Since the rotating mirror scans by sub-scanning by simple vibration, the mechanism is much simpler than that of the above-mentioned Japanese Patent Application Laid-Open No. 63-101839.

[Brief description of the drawings]

 FIG. 1 is a view for explaining the principle of the present invention, FIG. 2 is a block diagram of a first embodiment of the present invention, FIG. 3 is a block diagram of a second embodiment of the present invention, and FIG. It is a block diagram. In the figure, 11 is a charge-coupled device (CCD), 12 is a document, 16 is a sub-scanning direction, 20 is a turning mirror, and 23 is a turning transparent plate.

Claims (1)

(57) [Claims] An optical path between the one-dimensional array and the subject, wherein the one-dimensional array and the subject relatively move and scan in the sub-scanning direction to obtain a two-dimensional image; A means for slightly reciprocating deflection in synchronism with a line cycle, and repeatedly performing scanning in the direction opposite to the sub-scanning direction at substantially the same speed as the sub-scanning.