JP3622777B2 - Image reading optical system and image reading optical apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading optical system and an image reading optical device that can be used in an input unit of an optical information processing device such as an optical computer or an optical character reader (OCR).
[0002]
[Prior art]
When the light emitted from the light source is converted into parallel light by a lens and irradiated to the object, and the parallel light reflected by the object is obtained, the image of the object is read. If the lens is present on the optical path for reading (extracting reflected light), the reflected parallel light is condensed by the lens and returned to the light source, so that an output cannot be obtained due to the shadow of the light source. For this reason, as shown in FIG. 6, the light source 51 and the lens 52 are provided at positions off the reflected light path, the light from the light source 51 is reflected by the beam splitter 53 and guided to the object 54, and the object 54 There is known an image reading optical system that transmits and outputs reflected light. Such an optical system can also be seen in a metal microscope or the like.
[0003]
[Problems to be solved by the invention]
However, in the structure shown in FIG. 6, the light source and the optical system associated with the light source protrude greatly in the direction perpendicular to the optical axis. This is not only an obstacle to miniaturization, but also inconvenient to handle.
[0004]
In view of the above circumstances, an object of the present invention is to provide an image reading optical system and an image reading optical device that have a small-sized illumination device that does not protrude from the main body.
[0005]
[Means for Solving the Problems]
In the image reading optical system of the present invention, in an image reading optical system that irradiates light toward an object and reads an image of the object with light reflected by the object, a light source that irradiates the light A diffraction grating that irradiates an object with high-order diffracted light obtained by collimating the wavefront of light from the light source and outputs zero-order diffracted light as image readout detection light related to the high-order diffracted light reflected by the object comprising the and. Further, 0 may be diffracted light or diffracted light Yukimitsu Taira as the image reading detection light. The light source may be disposed on an optical path through which light reflected by the object passes.
[0006]
With the above configuration , parallel light can be generated in the first-order diffracted light of the diffraction grating, and this diffraction grating is zero- order of the order different from the irradiation light of the parallel light reflected by the object. Since it outputs folded light, there is no problem in obtaining parallel light with a lens as in the prior art, the diffraction grating can be arranged on the optical axis through which the light reflected by the object passes, and the light source Since it can arrange | position on the optical axis through which the light reflected by the said object passes, or the vicinity of an optical axis, size reduction is possible.
[0007]
The image reading optical apparatus of the present invention is characterized in that a light absorbing wall is provided around the image reading optical system having the above-described configuration.
[0008]
In the image reading optical system comprising the above-mentioned diffraction grating, light not light sac Chitaira Gyohikarika from the light source would proceed in a direction deviating from the object surface of interest becomes diffused light . Further, the light other than the next example 0 through the diffraction grating in a flat row light reflected diffracted light by the target surface also becomes diffused light, which is likely to adversely affect the reading accuracy as stray light. In the case of the image reading optical apparatus having the above configuration, since the light absorbing wall is provided around the image reading optical system, the diffused light is absorbed by the light absorbing wall.
[0009]
The light source may be disposed on the light absorbing wall. With this configuration, the light absorption wall serves as the light source placement seat, so that it is not necessary to form a separate placement seat, and the manufacturing of the image reading optical device can be simplified.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011]
FIG. 1 is a schematic diagram showing an image reading optical system 1 of the present invention in which parallel light is irradiated toward an image 10 and an image is read with reflected parallel light. In the image reading optical system 1, a light source 2 is disposed on an optical path through which light reflected by the image 10 passes. As the light source 2, an infrared semiconductor laser having a wavelength of 780 nm was used. Moreover, although the light source 2 is arrange | positioned in the optical axis center of the reflected parallel light, the shadow by the light source 2 which arises in reflected light is a comparatively small thing.
[0012]
A transmissive diffraction grating 3 is arranged between the light source 2 and the image 10. The light from the light source 2 is diffracted by the diffraction grating 3. The diffraction grating 3 is formed with a diffraction pattern so that high-order diffracted light (first-order diffracted light in this embodiment) becomes parallel light. The parallel light is incident on the image 10 perpendicularly. The parallel light reflected by the image 10 (hereinafter abbreviated as reflected parallel light) is also diffracted when passing through the diffraction grating 3, and the diffraction pattern causes the higher-order diffracted light of the reflected parallel light to become diffused light. The 0th-order diffracted light of the reflected parallel light remains as parallel light, and this parallel light is output toward a light receiving unit (not shown). That is, the optical system is configured such that the first pass diffracted light is used for the forward path and the zeroth diffracted light is used for the return path.
[0013]
FIG. 2 is an enlarged cross-sectional view of the diffraction grating 3. The diffraction grating 3 is made of, for example, a quartz plate having a thickness of 1 mm. The grating pattern of the diffraction grating 3 is set so that the ratio of the first-order diffracted light and the zero-order diffracted light is approximately 1: 1. The lattice pattern in this case is a rectangular groove, and the groove depth is 0.5 μm. Of course, the lattice pattern is not limited to the rectangular groove.
[0014]
As described above, the image reading optical system 1 generates parallel light in the first-order diffracted light of the diffraction grating 3, and the diffraction grating 3 outputs 0-order diffracted light of the parallel light reflected by the image 10. Therefore, there is no problem in obtaining parallel light with a lens. And since the light source 2 and the diffraction grating 3 can be arrange | positioned on a reflected light path, an overhang | projection part does not arise.
[0015]
FIG. 3 is a schematic diagram illustrating another configuration example of the image reading optical device 11. The image reading optical device 11 is configured by shifting the position of the semiconductor laser located in the center of the optical axis in the image reading optical system 1 and arranging it near the optical axis, and by providing a light absorbing wall 15. The light absorption wall 15 is formed by applying a paint that absorbs light, for example.
[0016]
In the structure shown in FIG. 1, the shadow of the semiconductor laser is generated. Further, the light from the light source 2 that has not been collimated becomes diffused light and travels away from the target image 10. Similarly, light other than the 0th-order diffracted light that has passed through the diffraction grating 3 due to the parallel light reflected by the image 10 also becomes diffused light, which may be stray light and adversely affect reading accuracy.
[0017]
On the other hand, in the configuration shown in FIG. 3, since the light absorbing wall 15 is provided around the image reading optical system 1, the diffused light is absorbed by the light absorbing wall 15. . Further, since the light source 2 provided in the image reading optical system 1 is arranged so as to deviate from the center of the optical axis of the reflected parallel light, the influence of the shadow caused by the light source 2 generated in the reflected parallel light does not occur. Further, since the light source 2 is formed on the light absorption wall 15 and the light absorption wall 15 is an arrangement seat for the light source 2, it is not necessary to form another arrangement seat, and the image reading optical device 11 is manufactured. Can be simplified.
[0018]
In this embodiment, a transmission type is used as the diffraction grating 3, but an image reading optical system can also be configured using a reflection type diffraction grating. In this case, for example, as shown in FIG. 4, the diffraction grating 31 is configured to transmit approximately half of incident light and reflect half, and is disposed at an angle of approximately 45 ° with respect to the optical axis. This angle is not limited to approximately 45 ° and can be freely determined by the design of the diffraction grating. The light source 2 is disposed between the image 10 and the diffraction grating 31 and irradiates light toward the diffraction grating 31 side. The diffraction grating 31 is formed by forming a diffraction pattern so that higher-order diffracted light (for example, first-order diffracted light) becomes parallel light, and the parallel light is incident on the image 10 perpendicularly. The parallel light reflected by the image 10 passes through the diffraction grating 31, and the 0th-order diffracted light (parallel light) is output toward a light receiving unit (not shown) provided at a position facing the image 10. Become. Alternatively, as shown in FIG. 5, the diffraction grating 32 is configured to reflect all of the incident light, and is disposed at an angle of approximately 45 ° with respect to the optical axis. The light source 2 is disposed between the image 10 and the diffraction grating 32, and irradiates light toward the diffraction grating 32 side. The diffraction grating 32 is formed by forming a diffraction pattern so that high-order diffracted light (for example, first-order diffracted light) becomes parallel light, and the parallel light is incident on the image 10 perpendicularly. The parallel light reflected by the image 10 is reflected by the diffraction grating 32, and the 0th-order diffracted light (parallel light) is output toward a light receiving unit (not shown) provided on the side of the image 10.
[0019]
The light source 2 is not limited to a semiconductor laser but may be a small solid laser or the like, and a monochromatic light source such as a sodium lamp or a light emitting diode can be used if it is not necessary to be coherent.
[0020]
【The invention's effect】
As described above, according to the present invention, the image reading optical system can be configured in a small size, and since no overhanging portion is generated, handling is easy. Further, when a light absorption wall is provided between the image reading optical systems, unnecessary diffused light can be absorbed by the light absorption wall. Further, when the light source is disposed on the light absorbing wall, the light absorbing wall serves as a light source mounting seat, so that it is not necessary to form a separate mounting seat, and the manufacturing of the image reading optical device can be simplified. There is an effect.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an image reading optical system of the present invention.
FIG. 2 is a sectional view of a diffraction grating used in the image reading optical system of the present invention.
FIG. 3 is a schematic diagram showing another example of the image reading optical system of the present invention.
FIG. 4 is a schematic diagram showing another example of the image reading optical system of the present invention.
FIG. 5 is a schematic diagram showing another example of the image reading optical system of the present invention.
FIG. 6 is a schematic diagram showing a conventional image reading optical system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image reading optical system 2 Light source 3 Diffraction grating 10 Image 15 Light absorption wall

Claims (5)

In an image reading optical system that irradiates light toward an object and reads an image of the object with light reflected by the object, a light source that irradiates the light, and a wavefront of light from the light source And a diffraction grating that irradiates the object with high-order diffracted light that is converted into parallel light and outputs zero-order diffracted light as image readout detection light related to the high-order diffracted light reflected by the object. An image reading optical system. The image reading optical system according to claim 1, wherein the zero-order diffracted light as the image reading detection light is parallel light . The image reading optical system according to claim 1, wherein the light source is disposed on an optical path through which light reflected by an object passes . An image reading optical apparatus comprising a light absorbing wall provided around the image reading optical system according to claim 1 . The image reading optical apparatus according to claim 4, wherein a light source is disposed on the light absorbing wall.

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