JPH01500226A - scanning device - Google Patents

Abstract

A scanner including a source of coherent light, a radial hologon, a f theta lens and a target. Between the light source and the hologon there are means for forming light from the source into a collimated beam having an oblong cross-sectional shape and for directing the beam onto the hologon at a predetermined incident angle and with the long axis of the oblong cross-sectional shape of the beam radial of the axis of rotation of the hologon. Prismatic means are provided between the hologon and the lens means for so modifying the cross-sectional shape of the beam that the spot at the target station has a selected shape and orientation. This allows the shape, orientation and size of the beam on the hologon to be optimum for duty cycle of the hologon and for spot size on the target. The prismatic means allows the spot shape and orientation on target to be optimized. The prismatic means tends to introduce undesirable bow into the scan line, therefore the wavelength of the light and the grating factor (n lambda )/d of the hologon are selected to produce an approximately equivalent opposite bow.

Description

[Detailed description of the invention] scanning device Background of the invention Technical field The present invention sequentially sweeps electromagnetic radiation spots along the same line scanning path at high frequency. The present invention relates to a scanning device (scanner) for performing. To form a raster, The target nodule at which the beam is directed is moved in a direction perpendicular to the linear scan path. or the scanning beam is moved in such a vertical direction. Ru.

Background technology The scanning device is used for writing, in which case, before forming sequential sweeps of the beam, Usually information has to be superimposed on the beam; scanning devices are also useful for reading In this case, the beam impinging on the target has a constant intensity and the readout The beam reflected or transmitted by the scanned target is monitored and generates a signal representing the information on the board.

Rotary type consisting of a device containing several plane mirrors uniformly arranged around the circumference of a cylinder Scanning devices are known. The mirror surface is parallel to the cylinder axis and passes through the center of the mirror. The radii are equiangularly spaced around the axis. The motor rotates this device at high speed do.

A stationary beam of light is directed into this device, which reflects the incident beam and has the same linear diameter forming each successive sweep of the light beam along the path. Devices with built-in mirrors like this has been called a polygon.

Other scanning devices are also known. Such diffraction devices are made of light-transmitting materials or A disk made of reflective material and on which multiple identical facets are formed. Each facet may include a diffraction grating, and the grating lines may include a diffraction grating. may be perpendicular to the trisecting radius or parallel to such radius Good, these two forms have been called ``tangential'' and ``radial'', respectively. The disk supporting the zero grating has been called a hologon.

To obtain higher resolution when reading or writing information on the target, The effective part of the beam has a very small cross-sectional area when it hits the target. Should. Rotary scanning to focus the beam on a predetermined small area point Hole diameter of the spot where a focusing lens may be placed between the device and the target is inversely proportional to the diameter of the incident beam on the rotating device, i.e. polygon or hologon. It is known that I need.

A beam only images an image when it lies entirely on a single facet of the hologon. Valid for reading or writing.

When a beam is incident on two facets, two diffracted beams are formed. , each beam is truncated so that the spot formed on the target is These two beams will cause distortion. Also the end of the line with one diffracted beam part and the other diffracted beam will sweep the starting part of another line. child In cases like this, if you write an image, the information will be written in two places, so system is not valid; if the system reads an image, different information will be in different locations. The ratio of the effective scan time to the total scan time that would be collected and read simultaneously The rate is defined as the duty cycle of the scanning system.

The effective scan time is the time when the entire beam is within one facet of the hologon. is defined as The total scan time is the time the beam scans over each of two consecutive facets. It's time to go through the similarities. Compare effective scanning times when designing scanning devices By making the target smaller, the data ratio can be increased accordingly. However, such Increases are costly and limited. Chord direction of the beam at the point of incidence on the hologon As the dimensions decrease, the impact coefficient of the hologon increases accordingly. therefore, In order to increase the impact coefficient, the chordal dimension of the beam in the hologon is actually small. On the other hand, in order to increase the resolution, the beam must be large in the hologon. It is necessary to have a diameter.

A desire often arises to further increase the writing or reading speed. this formed in unit time, with or without degrees of freedom, increasing the information density. There is a desire to increase the number of scan lines used. of scanning lines formed within unit time number is equal to the number of facets crossing the beam in unit time, this number of scanning lines is , is the product of the rotational speed of the hologon and the number of facets on the hologon. therefore , the speed of reading or writing increases with the increase in the number of facets on the hologon can be increased by increasing the rotational speed of Each method of trying to achieve high speeds has that problem. As the speed increases, the stress on the hologon increases and unless the undesirable step of creating a vacuum around the hologon is taken. , the power required to drive the hologon increases rapidly with speed. Hologon If the number of facets is increased while keeping the diameter and beam shape constant , the complexity of fabricating the hologon increases and the impact coefficient decreases. number of facets In order to increase but maintain the same impact coefficient, the diameter of the hologon can be increased. However, when the diameter is greatly increased like this, the stress on the hologon and the hole Increases the power required to drive Logon. The power required to drive the disc is the radius It is known that the increase is approximately to the fifth power.

Chord direction of the beam at the point of incidence on the hologon to keep the impact coefficient constant The dimensions can be reduced, but this will reverse the ray distribution within the spot on the target. This would have an adverse effect on the resolution of the system, since

The shape and direction of the beam spot on the target is also important. As described above To increase the resolution, it must be made smaller, however, its fraction The surface shape is not circular, i.e. it is more transverse to the scan direction than in the scan direction. It is preferable that it be long in the direction of This is the reading of a single pixel (vixel) of information. This is because the write operation is not instantaneous but requires a certain finite amount of time. this time In between, the spot moves a finite distance.

Therefore, in order to read or write circular pixels with high resolution, spot must be narrower in the direction of movement than across the direction of movement.

Therefore, when building a scanning device, e.g. read or write speed , speed capacity, resolution, mode of electronics in read or write circuits. power, hologon cost, whether or not the hologon is placed in a vacuum, impact coefficient, etc. There are many relevant factors to consider. Many of these depend on the shape and area of the beam. form mutually contradictory demands regarding

Provides a scanning device with high resolution, high speed and acceptable motor power requirements This is the object of the present invention.

l-suction OlL According to the invention, a substantially straight radiation spot with a selected shape and direction A scanning device for providing a scanning of a line with a wavelength wavelength and a radiation source with a wavelength The hologon includes a radial hologon arranged to rotate around the pitch. at least one pattern of parallel grid lines having a width d. Also, it is A parallel beam (collimated beam) of radiation from a radiation source with an elliptical cross-section The beam is formed into a hologon at a predetermined angle of incidence. The long axis of the surface shape is oriented in the radial direction of the rotation axis of the hologon so that it is incident on the beam. including means for The target section consists of a hologon that receives the scanned beam and a target. A lens means between the target portion focuses the beam to a spot on the target portion. let The prism means between the hologon and the lens provides a spot in the target section. child order that modifies the cross-sectional shape of the beam so that the cut has the selected shape and direction ) is the scanning beam incident on the means applied by the prism means onto the scanned beam. is selected to occur within the beam being scanned at the target. The line will be almost straight.

The radiation source generates coherent light and is preferably a laser diode. However, the radiation source may be incoherent, such as a tungsten source. In this case, means are provided to make the beam almost coherent. It is usual. Such means include narrow band filters and tungsten light sources. takes the shape of a pinhole, onto which the rays of light are focused after passing through the filter. Such a scanning device may include a prism means that changes the cross-sectional shape of the beam in the scanning direction. This is advantageous because it expands in a direction perpendicular to . Such abilities are unique to Hologon. allows the use of a radially long and chordally narrow beam cross-section of the hologon. . The ability to narrow the beam shape chordally increases motor speed and power. It is possible to increase the impact coefficient without any problems, which makes it possible to write or read read or write speeds without relying on the high speed of the electronics in the circuit. It is possible to increase the degree of This high impact coefficient does not reduce the number of facets. This is achieved without increasing the diameter of the hologon. The chordal dimension of the beam is half Since it can be reduced independently of the radial dimension, the cross-sectional area of the beam at the hologon is is reduced to negatively affect the energy distribution within the spot at the target. There's no need.

Brief description of the drawing FIG. 1 is a schematic side view of a scanning device according to the invention for writing information on film; Figure 2 is a diagram similar to Figure 1, with the beam generated by a diode as a representative example. a schematic perspective view of a laser diode included in the described device; FIG. 3 shows prism means included within the apparatus according to FIG. 1; FIG. 4 shows a radial hologon included within the device according to FIG. 1; FIG. 5 shows other prism means and part of the hologon included in the device, and a diagram illustrating a ray path passing through a hologon and other prism means; Figures 6a, 6b, 6c and 6d illustrate various aspects of the apparatus shown in Figure 1. a diagram showing the cross-sectional shape and orientation of the beam at the location; and FIG. 7 is a diagram showing part of the path of the diffraction and scanning lines given by the hologon. Ru.

H mode To aid in understanding the following discussion, orthogonal X, Y, and Z axes are shown in Figure 1. Place the sea urchin. Therefore, the plane in FIG. 1 lies within the XY thousand field plane. entire light beam The direction is in the Y direction. Most drawings include an explanation of the orientation of the parts shown within each drawing. X, Y, and Z axis orientations are included to aid in solution.

The scanning device 20 shown in FIG. a substrate 22 on which all optical components are placed with unfavorable distance between them. mounted in such a way that strong relative movements are avoided.

The device 20 includes a source of coherent radiation, in this example infrared light. In the embodiment, the light source is a laser diode 24 supported on a mount 26. . Vernier adjustment device 28 tilts the axis 30 of output beam 29 relative to the Y-axis. The diode 24, which allows for the adjustment of the slope (see FIG. 2), is connected as shown in FIG. It is mounted so as to guide the output beam 29 to the left in the Y direction.

Laser diodes depending on the information contained in the electronic signal stream Modulating means are provided for modulating the output of 24. This kind of modulation means is Since it is well known, it is not shown in the attached drawings and its explanation will be omitted below. .

Cross-sectional shapes and cross-sectional shapes in orthogonal directions of beams emitted from different laser diodes In this embodiment, the diode 24 has an elliptical cross section. A diverging beam 29 is generated (see Figure 2), whose dimension in the Z direction is larger than that in the X direction. It is. Beam 29 is supported by a mount 34 extending from substrate 22. The light is incident on a mating (parallelizing) lens system 32 . The lens system 32 parallelizes the light beam. , but its cross-sectional shape remains unchanged. Therefore, the beam leaving the lens system is only For example, in the XZ-axis plane 6a of FIG. 1, it has a cross-sectional shape as shown in FIG. 6a. Ru.

The ratio of the major axis to the minor axis of the cross-sectional shape of the beam in 6a is when it enters the hologon. is not the desired size for the beam.

In other embodiments the beam may have a desired shape; however, This is not the case in this example. Therefore, anamorphic (with different horizontal magnification) ) The prism means 36 of this embodiment, which is a beam expanding means, is a collimating lens system. 32 in the path of the rear beam. The prism means 36 is mounted via a mounting base 38. In this embodiment, the prism means 36 is supported from the substrate 22 by The angle vertices 41 and 43 include two prisms arranged parallel to the X axis (see Fig. 3). ), in this arrangement the prism is a prism that refracts only in the )'Z plane. Zm 40.42 expands the beam dimension in the Z direction, as shown in Figure 3. and is arranged to transmit beyond it parallel to the incident beam, ie in the Y direction.

The advantage of having two prisms instead of one is that for a given anamol Fickian beam expansion can be achieved with an output beam nearly parallel to the input beam. be.

The collimating lens system 32 and the anamorphic beam expanding means cooperate to Converts radiation from a source into a parallel beam (collimated beam) with an elliptical cross-section Forming means for forming.

As an anamorphic beam expansion means, a cylindrical lens is used instead of a prism means. lenses are available.

The beam emerging from prism means 36 (in plane 6b in FIG. 1) It has a cross-sectional shape as shown in figure b. The dimension in the X direction is the incidence on the prism means 36. The dimensions of the beam are the same, but the dimensions in the Z direction have been increased.

The beam is then coupled to a diffraction grating 44 supported by a mount 46 extending from the substrate 22. The plane of the zero diffraction grating incident on is parallel to the plane of the hologon, which will be described later. The grid lines are on the Z axis The parallel 0 diffraction grating 44 has the same properties as the gratings of each facet of the hologon. The purpose of the zero diffraction grating is shown below. The effect of the grating 44 on the beam is to It is a folding around the remaining axis in the plane. The beam after being diffracted by the grating The cross-sectional shape of the arm remains the same as shown in Figure 6b.

The beam is then incident on hologon 48 which is supported by shaft 50 of motor 52.

Motor 52 is supported from substrate 22 by a support (not shown). Hologon's The effect on the beam will be explained in detail later.

At this point, we want the beam to travel again with a major vector component in the Y direction. The hologon diffracts the beam, but when the hologon is rotated, the hologon diffracts the beam. It is sufficient to explain that it is scanned, that is, it gives a sweep component in the Z direction to the hologon. Will.

The beam then passes from the substrate 22 to a second prism supported by a support (not shown). incident on the rhythm means 54. Support for Prism 56.58 April 1986 On the 4th, the name of "scanning device" was given in the name of R1chard A tan S Lark. No. 848,427, filed in U.S. Patent Application No. 848,427. US special Application No. 848,427 was filed on the same date as this application. ing. Please refer to that application for an understanding of the mounting base. , the prism means 54 is arranged such that the apex lines 57 and 59 of their wedge angles are parallel to the Z axis. (See FIG. 5).

Prisms 56,58 are arranged to increase the beam size in the X-axis direction. this The dimensions in the Z direction do not change, but the dimension ratio changes. The beam passes through prism 58 After separating, it has a shape as shown in Fig. 6c (on the X7 plane of 6c), and the whole is guided parallel to the Y axis. The advantage of using two prisms instead of one is that the output beam is parallel to the input beam, and the output beam is parallel to the input beam. This case can never be obtained with one prism, however the implementation of the present invention For example, the prism means downstream of the hologon may include one prism or more than two prisms. It is also possible to have a structure consisting of rhythms.

The scanning beam is incident on lens means 60, which is mounted on substrate 22. The beam is focused on a target within the plane 62 in the target portion 64 that has been The beam is focused in a spot shape having the shape shown in Figure 6d. impinges on the target, this time with the long axis oriented parallel to the X axis. X direction and Reversal of the relative amount of dimensions with respect to the Z direction is performed by a focusing lens 60. target The shape of the sheet is not a subject of the present invention; it may be, for example, a sheet or a series. It can be a continuous web shape, or even a photosensitive drum, which absorbs the radiation from the laser. An image on which an image shape is formed when exposed to energy in, for example, It may be electrostatic or silver halide. In this embodiment, the photosensitive material is In other words, the control speed for forming a rask pattern in the direction perpendicular to the scanning direction (Z direction) moved in degrees. In other embodiments, the target material remains stationary and the beam For example, if the beam is a mirror whose angle of inclination to the incident beam can be varied as in known methods. It is also deflected in a direction perpendicular to the scanning direction.

When the current to the laser diode is varied to modulate the output of the diode, It is known that the wavelength of the emitted radiation can be varied. Hologon 48/\'s Bi If the angle of incidence of the beam is constant, a change in wavelength will also change the angle of the diffracted beam. There will be.

This results in a manipulation within the image being written. Diffraction grating upstream of the hologon The element 44 reduces undesirable wavelength effects. In short, the wavelength has changed. The grating 44 is shaped like a hologon 48 so that the diffraction angle remains constant regardless of changes in wavelength. change the angle of incidence on the

The above description is intended to provide a general understanding of the device.

Let's explain in more detail below.

The hologon 48 is a multi-faceted hologon, as shown in Figure 4. In the example, there are 18 identical facets 66. Each facet 66 is diffraction The grid lines within each facet, including grid 68, are parallel to the radius that trisects the facet. It is a row. Although some grid pattern lines are shown in Figure 4, this It will be understood that all of these are incomplete and merely illustrative. 111 The actual number of lines per 11 is 2162, in this case the laser diode The wavelength of the electromagnetic radiation emitted from is 0.830 x 10-'m ring. diffraction grating A photographic layer 70, conventionally an optical layer, is supported by a transparent glass support 72. , (see Figure 5).

A broken line ellipse 74 indicates the shape and direction of the beam when it enters the hologon 48. You can see that the beam is incident almost tangentially to the periphery of the disk, and the ellipse is half-shaped. When placed as far as possible in the radial direction, the facets measured through the ellipse 74 This is because the ratio of the chordal dimension of the ellipse to the dimension of the ellipse in the same chordal direction is maximum. Maximize impact coefficient.

Ellipse 74 is shown in the center of facet 66, in this position its long axis is parallel to the grid lines within the facets. In this arrangement, the diffracted beam is When the hologon 48, which is parallel to the Y axis and has no component in the Z axis, rotates from the position shown in FIG. When rotated, the grid lines become zero-diffracted beams that are sequentially inclined to the long axis of the ellipse. Due to this sequential inclination, the Z-direction component of the beam increases sequentially. The beam is hollow (as seen in Fig. 1), the hologon is That is, when viewed from above in Figure 1 and rotated clockwise, the beam supports Figure 1. As the hologon continues to rotate, the Z-axis The component will continue to increase, eventually part of the beam will be transferred to the next adjacent facet. incident, and that part of the beam has a maximum Z-axis component in the direction from the plane of the paper supporting Figure 1. and at the same time part of the beam still remaining on the previous facet. has a maximum Z-axis component toward the rear of the page. If you keep rotating the hologon, The beam portion on the previous facet is reduced to zero. If you continue to rotate like this , the Z-axis component in the direction from the plane of the paper will eventually decrease to zero, i.e., the beam will become fused again. (until it returns to the center of the facet), then the Z-axis component backwards from the page. It will increase sequentially. Therefore, the beam downstream of the hologon is The scan is repeated each time a block successively blocks the beam. in television scanning There is no flyback, but there are two output beams from the hologon. There are times when I do. When this device is used for image formation, there are two bits from the hologon. is not valid for writing while the system is present, and therefore the useful portion of each scanline is Signal generating means are provided for providing a signal indicating the starting point and, if possible, a signal indicating the ending point. Ru. Since these signal generation means are well known, they are not shown here or described in detail. Details are omitted. Here, these means are applied immediately after the first beam ends and so that the second beam is respectively hit by the scanning beam just before starting again. It will suffice to say that the starting sensor includes two sensors arranged Outputs a signal to the modulation circuit to start modulating the laser diode output, and if If a termination sensor is provided, the termination sensor modulates the laser diode output. It is possible to stop it.

A leap where the diode is not modulated is useful if the information is provided continuously in real time. If so, the input information is temporarily stored.

If information is retrieved from storage, it is done during scanning of the useful portion of each scanline. It is retrieved from storage only at .

The beam leaving the hologon has the desired effect on the spot of the ray that hits the target. It has a much larger cross-sectional area than the

A lens system 60 reduces the area of this beam to a predetermined value on the target and Maintain the focus of the spot on the planar target when scanning. This is usually fθ It is called a lens. Such lens systems are well known and need not be further explained. stomach.

By appropriately selecting the fθ lens system 60, a predetermined cross section of the beam can be placed on the target. Even if the product is achieved, the predetermined shape is obtained and it is not small, so , the X:Z dimension ratio of the beam is changed to a predetermined value before the beam enters the lens system. A prism means 54 is included to provide a. The lens means 60 ends up in the beam X: You have to be aware of transposing the dimension ratio of Z, for example, X;Z dimension ratio A beam entering the l/lens system with a ratio of 1:2 has an X:Z dimension ratio of 2 at the target. :1, so if in the target the X:Z dimensions If you want to increase the ratio, increase the X:Z size ratio between the hologon 48 and the lens system 60. It only needs to decrease.

As an example, the x:Z dimension ratio of the spot on the target is 1.4:1. (Fig. 6d), therefore, the X:Z dimension in plane 6c The ratio, i.e. the input to the lens system, must be 1:1.4, however , the X:Z dimension ratio of the beam leaving the hologon is 1:4 to maximize the impact coefficient. It is.

The prism means 54 changes the beam ratio from 1=4 to 1:1.4 by expanding in the X direction. let Thus, the prism means 54 provides a predetermined shape of the spot on the target 64. If this were not present, the spot on the target would be useful for obtaining A compromise must be made between optimizing the R of the shape of the hologon and optimizing the impact coefficient of the hologon. stomach.

However, the prism means 54 does not allow for the instantaneous angular displacement of the beam axis from the Y axis. This has an undesirable effect in that it forms an in-beam X component in response to say In other words, the prism means tends to create a curvature in the path of the spot on the target. have Such curvature can occur if the device is writing an image and the information in each scan line is Visibility from hologons is undesirable when the information is derived from straight lines in the document. This effect can have a negative impact when designing a system that scans approximately in a straight line. It is considered undesirable.

According to the invention, the beam leaving the hologon has a curvature formed by prismatic means. The spot is intentionally curved in the opposite direction, and the path of the spot is as straight as possible. so that the curvature is as equal as possible to the curvature formed by the prism. .

To understand how the path of the scan line downstream of the hologon has the desired curvature 7, which now shows the diffraction imparted by the hologon and the path of the scanning line. let's.

Since the hologon plane is inclined to the XZ plane, another orthogonal axis system is used for this analysis. is set.

A, B and C are orthogonal axes.

The hologon lies in the AB plane.

Input beam 80 lies in the AC plane and is inclined at an angle γ to the C axis. γ is is the angle of incidence.

Is φ the input beam incident and directed on the radius that trisects the facet? is the instantaneous rotation angle of the hologon.

82 is the output beam axis when φ=0, and is within the AC plane. This is hologo This is called the reference axis for the beam 5 and corresponds to the central scanning position of the beam. This is on the C axis Opposite angle γ′. slope.

A' and B' are perpendicular to C'; B' is parallel to B.

84 is an instantaneous output beam axis. This has an inclination of θ8 with respect to the A” C’ plane. , C' makes an inclination of θ8 with respect to the B' plane.

θB is called the in-track scanning angle.

θ^ is called the cross-track angle, which is the angle of the spot on the target from a straight line scan. Determine the instantaneous displacement. θ6 is therefore a measure of the curvature of the spot path.

86 is a scanning miracle and is the path actually tracked by the spot.

The scanning components θ3 and θ6 shown in FIG. 7 are expressed as follows.

C=sin7−Gcosφ D=sinγ-G E=Gsinφ n is the grating order (first order diffraction is used, so n=+1) from the λ diode Wavelength of emitted radiation d Pitch of diffraction grating It is.

To minimize the sensitivity of the system to hologon wobbles, the angles γ and γ′ are It is known that they must be equal. Therefore, the textbook Substituting this condition for the minimum wobble of 6 degrees into the equation for the general scanning trajectory above, By entering, the two scanning components θ and θ9 are the case descendant number G and hologon rotation. It can be expressed only by the angle φ. The reason is; E=Gsinφ This is because.

λ The above analysis can be done by appropriately selecting the lattice coefficient G, basically □. The desired trajectory of the output beam can be approximated. In reality, the range of radiation sources available is Since the range is limited, choosing an appropriate grating coefficient comes down to choosing an appropriate grating pitch. Ru.

The prerequisites for forming the desired spot shape from the beam shape in the hologon. Standard optical analysis can be used to design the system. by prismatic means curved fit λ Therefore, the value of - that gives the compensating curvature is determined. Therefore, the known wavelength Once a laser diode has been selected, the grating and pitch d are determined, and its pitch A hologon is produced in step d.

Once the grating coefficient G is determined, this grating coefficient can be used to calculate the angle of incidence and the angle of diffraction. is determined by , and the system is set up with this angle of incidence and diffraction angle at the hologon.

In a particular embodiment of the invention, the following values are given to various parameters: .

Hologon Number of facets: 18 Lattice pitch 0.4624μ ring Beam input (output) angle 63.82° Diameter 4.5 inches prism 56 Refractive index 1.7098 Vertical angle 30° Incident angle in central scanning: 59°14' prism 58 Refractive index 1.7098 Vertical angle 30° Incidence angle in central scan: 59° Aspect ratio of beam on hologon: 4:1 Shape of spot on target: Ellipse (1:1.4) hologon and fθ lens The prism means between the It is understood that even if the beam is rotated by 0°, it still functions to form the same beam shape. However, in this case the curvature formed by the prism means is in the opposite direction. Therefore, to counter this curvature the hologon will curve in the opposite direction. The pitch of the zero grating, which would be designed to form a curve, is also different and The angle of incidence of the beam into the gong will also be different.

In the particular embodiment described above, the two prisms 56 and 58 are identical.

Embodiments may be constructed in which the prisms are not identical.

In the above description, the shape and dimensions of the spot on the target are explained. being done. The intensity distribution of the optical energy in the beam at the point of incidence on the hologon is Those skilled in the art will know that it is a Gaussian distribution. Also, if the beam is guilty Assuming no head truncation, the spot on the target also has a Gaussian distribution. do. The desired size of the spot will vary depending on the purpose.

If a beam expanding prism means is inserted between the tangential hologon and the fθ lens, If so, beam expansion is achieved but deflection sensitivity is sacrificed. Paraphrase Then, angular expansion is inversely proportional to beam expansion. When the deflection sensitivity is reduced, Requires a longer focal length f-theta lens to achieve a given scan line length Probably. If the same spot diameter on the target must be achieved For example, a larger beam diameter would be required in the hologon; This would destroy the advantage of the prism means between the logon fθ. However, the tangent Optimize performance by achieving things with radial hologons that cannot be achieved with shaped hologons. It is also an aspect of the present invention to find a beam that is formed along the beam path so that the Department.

Although in the particular embodiment described above the light source is a coherent (parallel beam) , in embodiments of the invention where rigorous performance is not required, the light source is not necessarily It does not need to be coherent like a laser diode, e.g. The tungsten light that passes through the filter and the pinhole is focused. In this case, nearly parallel light is generated, so that it is possible to use the construction for the scanning device according to the invention. Some commercial uses include, for example, image writing devices on light-sensitive materials such as photographic film. A zero image is provided to the scanning device as an electronic information stream.

Indecent accumulation (Content I: No change) Submission of translation of written amendment (Article 184-8 of the Patent Law) 1゜Indication of patent application PCT/US87100670’ 2. Name of the invention Scanning device Name (707) Eastman Kodak Company 5, Date of filing of amendment March 3, 1986 6. List of attached documents 1 translation of the written amendment r FIG. 1 is a schematic side view of a scanning device according to the invention for writing information on film. ; Figure 2 is a diagram similar to Figure 1, with the beam generated by a diode as a representative example. a schematic perspective view of a laser diode included in the described device; FIG. 3 shows prism means included within the apparatus according to FIG. 1; FIG. 4 shows a radial hologon included within the device according to FIG. 1; FIG. 5 shows other prism means and part of the hologon included in the device, and a diagram illustrating a ray path passing through a hologon and other prism means; Figures 6a, 6b, 6c and 6d show various points in the device shown in Part 1. a diagram showing the cross-sectional shape and orientation of the beam at the location; and Figure 7 is a diagram showing part of the diffraction and scanning line paths given by the hologon. be.

U's Mo' To aid in understanding the following discussion, orthogonal X, Y, and Z axes are shown in Figure 1. Place the sea urchin. Therefore, the plane of FIG. 1 lies within the XY plane. entire light beam The direction is in the Y direction. Most drawings include an explanation of the orientation of the parts shown within each drawing. X, Y, and Z axis orientations are included to aid in solution.

The scanning device 20 shown in FIG. a substrate 22 on which all optical components are placed with unfavorable distance between them. This function is used so that large relative movements are avoided. In practice, the range of available radiation sources is limited. Therefore, selecting an appropriate grating coefficient results in selecting an appropriate grating pitch.

The prerequisites for forming the desired spot shape from the beam shape in the hologon. Standard optical analysis is used to design the system.

Once the grating coefficient G is determined, this grating coefficient can be used to calculate the angle of incidence and the angle of diffraction. determined by , the system is set up with this angle of incidence and diffraction angle at the hologon .

In a particular embodiment of the invention, the following values are given to various parameters: .

Hologon Number of facets: 18 Lattice pitch 0.4624° Beam input (output) angle 63.82° Diameter 10.4ell prism 56 Refractive index 1.7098 Vertical angle 30° Incident angle in central scanning: 59° 14' prism 58 Refractive index 1.7098 Vertical angle 30" Incident angle in central scanning 59° Vertical length of beam on 14' hologon 4: Shape of spot on 1 target Ellipse (1:1.4) Center scan is hologon has no component in the plane containing the rotation axis of the beam and the point of incidence of the beam on the hologon. This is when a beam is output from the hologon.

The prism means between the hologon and the fθ lens means that they rotate about an axis parallel to the Y axis. form the same beam shape even if rotated 180° However, in this case, by prismatic means, The curvature formed will be in the opposite direction. Therefore to counter this curvature The hologon would be designed to form a curvature in the opposite direction of the zero grating. The pitch will also be different and the angle of incidence of the beam into the hologon will also be different.

In the particular embodiment described above, the two prisms 56 and 58 are identical.

Embodiments may be constructed in which the prisms are not identical.

In the above description, the shape and dimensions of the spot on the target are explained. being done. The intensity distribution of the optical energy in the beam at the point of incidence on the hologon is Those skilled in the art will know that it is a Gaussian distribution. Also, if the beam is noticeable Assuming no head truncation, the spot on the target also has a Gaussian distribution. do. The desired size of the spot will vary depending on the purpose.

If a beam expanding prism means is inserted between the tangential hologon and the fθ lens, If so, beam expansion is achieved but deflection sensitivity is sacrificed. Paraphrase Then, angular expansion is inversely proportional to beam expansion. When the deflection sensitivity is reduced, Requires a longer focal length f-theta lens to achieve a given scan line length Yes, if the same spot diameter on the target has to be achieved For example, a larger beam diameter would be required in the hologon. This is ho This would destroy the advantage of the prism means between the logon fθ. However, the tangent Optimize performance by achieving things with radial hologons that cannot be achieved with shaped hologons. It is also part of the present invention to find a beam that is formed along the beam path so that the Department.

Although in the particular embodiment described above the light source is a coherent (parallel beam) , in embodiments of the invention where rigorous performance is not required, the light source is not necessarily Doesn't have to be coherent like a laser diode, e.g. The tungsten light that passes through the filter and the pinhole is focused. In this case, nearly parallel light is generated, so it may be usable.

One factory millet tax■One Among the industrial applications for scanning devices according to the invention are e.g. There is an image writing device on the photosensitive material.The image is supplied as an electronic information stream to the scanning device. be done. 1 procedural amendment October 1986 4’H

Claims (11)

[Claims] 1. a radiation source having a wavelength λ; A small number of parallel grid lines mounted for rotation about an axis and having a pitch d a radial hologon having at least one pattern; The radiation from the radiation source is formed into a collimated beam having an oblong cross-sectional shape. The above beam is incident on the hologon at a predetermined angle of incidence, and when it is incident on the hologon, In this case, the long axis of the beam's oval cross-section is oriented in the radial direction of the hologon's rotation axis. means for injecting the beam; a target portion for receiving the scanned beam; and in the target portion; between the hologon and the target part to focus the beam on the spot. approximately a radiation spot having a selected shape and orientation, consisting of lens means; In a scanning device for providing straight line scanning: at the target section Modify the cross-sectional shape of the beam so that the spot has the selected shape and direction a prism means between the hologon and the lens means for; and the lattice coefficient nλ/d of the hologon (where n is the lattice order) is the scanned beam a curvature approximately equal to and opposite to the curvature tendency imparted by the prismatic means on the top; , selected to occur in the scanned beam between the hologon and the prism means. This enables a scanning device characterized in that the scanning line in the image area is almost straight. Place. 2. The radiation source generates coherent light and is characterized by being a laser diode. A scanning device according to claim 1. 3. The radiation source produces incoherent light, and the radiation source produces nearly coherent light rays. Scanning according to claim 1, characterized in that means are provided for Device. 4. Said means for making the light beam from the radiation source substantially coherent is a narrowband filter. the filter, the pinhole, and the rays passed through the filter onto the pinhole. and means for focusing. On-board scanning device. 5. The light beam from the radiation source is formed into a parallel beam having an elliptical cross-section. Claim 1, wherein said means for collimating comprises a collimating lens. , the scanning device according to item 2, item 3, or item 4. 6. The light beam from the radiation source is formed into a parallel beam having an elliptical cross-section. Claim 1, characterized in that the means for , the scanning device according to item 2, item 3, or item 4. 7. Claims characterized in that said anamorphic system includes prismatic means. Scanning device according to clause 6. 8. The prism means included within the anamorphic system is such that the output beam The beam is parallel to the input beam and the output beam has a predetermined oval cross-sectional shape. 8. The scanning device according to claim 7, characterized in that the scanning device includes two prisms. . 9. What is the beam angle incident on the hologon and the beam angle diffracted by the hologon? According to claim 1, 2, 3 or 4, characterized in that they are equal. scanning device. 10. The prism means between the hologon and the lens means is arranged so that the beam is prismed. The prism is characterized by comprising two prisms arranged so as to pass through the prism sequentially. A scanning device according to claim 1, 2, 3, or 4. 11. The coherent light source shall emit at a wavelength of 830 nm; each hologon The number of grid lines within a facet shall be 2162 lines per 1 mm; The angle of incidence and angle of diffraction at the hologon are equal; the beam is a first surface at a position where the beam enters the prism, and a second surface at a position where the beam exits the prism. In each of the two prisms through which the beam passes, each When the first surface is placed at an angle of 59°14' to the incident beam, The beam is formed in a plane that includes the axis of rotation of the hologon and the point of incidence of the beam on the hologon. the beam is output from the hologon without having a component; and and the apex angle of the second prism is 30°. The scanning device described in .