JP4658670B2 - Interference exposure apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an interference exposure apparatus. More specifically, the present invention relates to a two-beam interference used for manufacturing diffraction gratings used in various fields such as optical discs (laser discs, compact discs, digital versatile discs), magneto-optical discs, and spectrometers. The present invention relates to an exposure apparatus.

As is well known, one method of creating a diffraction grating is a two-beam interference method.
In the two-beam interference method, a light beam from the same light source (laser) is separated into two light beams, the two light beams interfere with each other to generate interference fringes, and a diffraction grating is obtained by recording and developing on a photosensitive material. It is a method (for example, patent document 1).

As a configuration used when producing a diffraction grating using the two-beam interference method, there is a configuration including a monitor exposure optical system as shown in FIG. 12 (for example, Patent Document 2).
In the configuration shown in FIG. 17, the exposure laser light source 1, the spatial filters 12 and 13, the collimator lens 14, the half mirror 15, the mirrors 16 a and 16 b, the exposure recording material 17, the monitor light source 2, And a light receiver 19.
The spatial filter includes an objective lens 12 and an aperture 13 and is used to cut noise (higher order transverse mode) of laser emitted light.

In the above configuration, the collimating lens 14 converts the light into a parallel light beam and separates it into two light beams by a half mirror. When these two light beams are overlapped again using the mirrors 16a and 16b, interference fringes determined by the laser wavelength and the angle formed by the two light beams are generated. When the recording material 17 is disposed on the interference fringes, it is possible to record irregularities and phase differences on the recording material by the intensity of the interference fringes.
As the recording material, a photoresist or a photopolymer is used. In the configuration shown in FIG. 12, the recording (exposure) wavelength is 514.5 nm, and the monitor light is 632.8 nm.

Incidentally, there is also a demand for monitoring how much the diffraction grating is produced during the two-beam interference exposure. At this time, if monitoring is performed at the same wavelength as the exposure wavelength, exposure is performed by the monitor light, and a desired diffraction grating cannot be manufactured.
Even when the absorption of the recording material is monitored at a wavelength that cannot be ignored even if it is different from the exposure wavelength, only a low-efficiency diffraction grating may be produced due to exposure with monitor light. As a method of performing exposure while monitoring, a method of using a monitor light having the same wavelength as the reproduction wavelength and using a recording material which can be recorded (absorbed) at the exposure wavelength but not recorded at the reproduction wavelength (absorbed) can be considered.

  For example, in FIG. 17, the exposure laser is a blue laser (argon laser) 1 and the monitor light source is a red helium neon laser 2. The recording material can be recorded with blue light, and it is possible to prevent the production of the diffraction grating from being adversely affected by the monitor light by selecting a material with a longer wavelength than blue and not recorded.

  Moreover, as a structure which is not affected by the monitor light, there is a structure shown in FIG. 18 (for example, Non-Patent Document 1 and Non-Patent Document 2).

  In the configuration shown in FIG. 18, the light source for interference exposure (recording) is an argon laser (referred to as Ar laser in the figure), and blue light having an oscillation wavelength of 488 nm is used. The light source for reproduction is a helium neon laser (referred to as a HeNe laser in the figure), and its oscillation wavelength is 633 nm. If the recording material does not absorb even when irradiated with a helium neon laser during exposure, it will have an adverse effect on the production of the diffraction grating. There is no configuration.

JP-A-10-39125 (paragraph "0002" column) JP 2002-60429 A (paragraph “0036” column) 2 in J. American Chemical Society 1994, 116, 7056 IDW'02 Digest P.I. 161, Fig. 1 “Property of Polarization Dependent Holographic Polymer Dispersed Liquid Crystal Device and its Application for Information Display”, Ogiwara et al.

In the configuration shown in FIG. 17, when the two light beams are parallel light beams, equal pitch interference fringes are formed, and the produced diffraction grating also has a uniform pitch grating shape.
Further, if a lens is inserted into at least one of the mirrors 16a and 16b and the recording material 17, a diffraction grating with an unequal pitch can be produced.

  On the other hand, depending on how the diffraction grating is used, it is necessary to produce a predetermined unequal pitch. For example, it is a case where it is desired to generate a diffracted light in a predetermined diffraction direction by disposing a diffraction grating in the diverging light path. At this time, if the exposure wavelength and the reproduction wavelength are different, the direction of the diffracted light is different, and furthermore, there is a possibility that the optimum diffraction efficiency cannot be obtained.

  Further, when the reproduction wavelength and the exposure wavelength are in the same wavelength band (the difference between both wavelengths is small), when the monitor light source is irradiated, the recording material is exposed even with the monitor light, and the characteristics of the produced diffraction grating deteriorate. This is because the contrast of the interference fringes by the exposure beam (ratio of the bright part to the dark part of the interference fringes) is substantially reduced. Due to this influence, there is a problem that the diffraction efficiency is particularly poor.

  If the exposure beam can be used as it is as monitor light during exposure, the above-mentioned problems can be solved. However, the use of the transmitted light (or diffracted primary light) of the exposure beam as monitor light is as follows. It was impossible for the reason.

FIG. 19 is a diagram for explaining the above reason. In exposure meter for producing a diffraction grating by irradiating an exposure beam B1, B2 to the recording material in the figure, 0-order transmission light P (B1,0 ^th) and beam B1 to the light beam B1 is transmitted through the recording material B2 +1 order transmitted diffracted light P (B2, ^{+ 1 st)} are included. On the other hand, the beam B1 is the light traveling through the recording material, in addition to B2 of the zero-order transmitted light P (B2,0 ^th) B1 of the + 1st-order transmitted diffracted light P (B1, ^{+ 1 st)} are included.
^{P1 = P (B1,0 th) +} P (B2, + 1 st) ··· ( Equation 1)
^{P2 = P (B2,0 th) +} P (B1, + 1 st) ··· ( Equation 2)
If the power (or power density) of both beams on the recording material surface is the same, the second term of (Equation 1) and the second term of (Equation 2) are equal. Therefore, (Equation 1) is
^{P1 = P (B1,0 th) +} P (B1, + 1 st)
Can be rewritten. In the case of producing a diffraction grating with high diffraction efficiency, the sum of the zero-order and first-order efficiencies is almost 100%, so that P1 is almost constant from the start of exposure. For this reason, even if P1 is monitored, it is impossible to know how much the diffraction grating has been produced. Similarly, P2 cannot be used for monitoring purposes.

  An object of the present invention is to provide an interference exposure apparatus having a configuration capable of obtaining a diffraction grating in which diffraction efficiency does not decrease even when monitor light having an exposure wavelength and a dynamic wavelength band is used in view of the problems in the conventional interference exposure apparatus. There is to do.

  Another object of the present invention is an interference having a configuration that enables monitoring with an exposure light source without sacrificing exposure power and without interrupting exposure for monitoring. It is another object of the present invention to provide an exposure apparatus and an interference exposure apparatus having a configuration capable of preventing interruption of the monitor even with a weak diffracted light intensity.

According to the first aspect of the present invention, the light emitted from the coherent light source is separated into two or more light beams, and the respective light beams are overlapped to generate interference fringes, and a recording material is arranged on the interference fringes. In an interference exposure apparatus for producing a diffraction grating,
A part of the amount of light from the light source is extracted , the extracted light is reflected to a plurality of mirrors, and the difference between the monitor optical path length and the exposure optical length is set to a distance equal to or greater than the coherence length of the light source, so that an optical pulse or low power It is characterized by irradiating a recording material with a density and monitoring transmitted light or diffracted light.

According to a second aspect of the present invention, there is provided the interference exposure apparatus according to the first aspect, wherein the light source is a laser light source constituting a laser resonator composed of two or more mirrors, and light leaks from mirrors other than the output mirror. Is a monitor light .

According to a third aspect of the present invention, the interference exposure apparatus according to the first or second aspect is used as an exposure apparatus of an image forming apparatus .

According to the first aspect of the present invention , the exposure is interrupted with one light source by taking out part of the exposure light and setting the difference between the monitor optical length and the exposure optical length to be equal to or greater than the coherence length of the light source. And monitoring without generating unnecessary interference fringes. In other words, by setting the difference between the monitor optical length and the exposure optical length to a distance greater than or equal to the coherence length, the monitor light and the exposure light will interfere even if the monitor beam overlaps the two light beams for exposure in the recording material. The interference fringes are not generated. Therefore, the production status of the diffraction grating can be monitored without reducing the contrast of the exposure interference fringes .

According to the second aspect of the invention, since the leakage light from the resonant mirror of the exposure laser is used as the monitor light, unnecessary interference fringes are generated without interrupting the exposure without reducing the exposure intensity. It is possible to obtain an interference exposure apparatus that can be monitored without any trouble.

According to the third aspect of the present invention, by using weak order light other than the 0th order and the additional light among the diffracted light by the exposure beam, even if the intensity of the weak diffracted light is used, the exposure is not adversely affected. In addition, an exposure apparatus capable of monitoring without interrupting exposure can be obtained.

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 1 is a view showing an example of an interference exposure apparatus which is an object of the embodiment of the present invention .

The interference exposure apparatus shown in FIG. 1 is parallel to an exposure laser apparatus 11 (a first light source having coherence), a spatial filter including an objective lens 12 and an aperture 13 for use as a beam expander. A collimating lens 14 for creating a light beam, a half mirror 15, mirrors 16a and 16b, a monitor laser light source 18, and a light receiving element 19 are provided. Reference numeral 17 denotes a recording material.

  The exposure laser device 11 uses an argon laser (oscillation wavelength 488 nm). When a laser that oscillates in a single longitudinal mode is used for the exposure laser device 11, there are advantages that a coherence length is increased and a diffraction grating with less noise can be manufactured.

A spatial filter is not always necessary, but noise may be generated in the laser beam by an optical element up to the half mirror 15 and the like, which is useful for improving the beam quality. The laser beam is bisected by the half mirror 15, and then beams are superimposed at a predetermined angle by the mirrors 16 a and 16 b to cause interference on the recording material 17 to generate interference fringes.
When the recording material (exposed sample) 17 is arranged at the position where the interference fringes are generated, a diffraction grating corresponding to the interference fringe pitch can be produced.

Further, a second light source 18 that emits light in the same wavelength band as that of the laser device 11 is used to monitor the production status of the diffraction grating during exposure.
Light from the second light source 18 is incident from the back side of the recording material. Here, the same wavelength band may be the same wavelength as the first light source or may be a wavelength different by several tens of nm. In short, it means that the exposure wavelength is not the wavelength difference such as blue light and the monitor light is green light but has the same or the same level of oscillation wavelength. In this example, a coherent ultra-small blue laser Sapphire 488-20 having an oscillation wavelength of 488 nm was used as a monitor light source.

  The argon laser 11 and the blue laser 18 have the same oscillation wavelength but are different lasers, and both laser beams have no coherence. However, a DC component is superimposed on the interference fringes caused by the exposure beam by the monitor light, and a high-efficiency diffraction grating cannot be produced as it is. For this reason, in this embodiment, the monitoring light is converted into an optical pulse to irradiate the recording material.

In this embodiment, the light intensity modulator 20 is used to turn the monitor light into an optical pulse.
As the light intensity modulator, an electro-optical crystal typified by LiNbO 3 (lithium niobate) can be used to generate a light pulse by applying a voltage pulse to the crystal. The pulse width (unit: second) and light intensity (unit: mW) of the light pulse are set as follows. The power density of the recording material for one light beam of exposure is A1 [mW / cm ² ], the exposure time is T1 [seconds], the power density of the monitor light is A2 [mW / cm ² ], and the optical pulse width (pulse time) Let T2 [seconds] be at least
A2 × m × T2 ≦ 0.1 × A1 × T1 (Formula 1)
To satisfy the relationship. In Equation 1, the symbol m represents the total number of optical pulses. More preferably, since T2 can produce a diffraction grating with higher diffraction efficiency as the time is shorter, it is desirable to select T2 that is shorter than the above relational expression.

  As for the traveling direction of the monitor light, the direction projected on the paper surface shown in FIG. 1 is opposite to the exposure light beam coming from the mirror 16a. However, an angle is provided in the depth direction of the paper so that the light receiving element 19 for receiving the diffracted light of the monitor light does not block the light beam from the mirror 16b (does not block a part of the light beam).

  When the diffraction grating starts to be formed on the recording material, the diffracted light intensity of the monitor light starts to increase. When the intensity of diffracted light is obtained so that the desired diffraction efficiency is obtained, the light for exposure is stopped (not shown, but blocked by a shutter or the like).

According to this embodiment, it is possible to construct an interference exposure apparatus with a monitor optical system that does not adversely affect the production of the diffraction grating even with monitor light in the same wavelength band as the exposure light source. In the present embodiment, the two-beam interference exposure meter is taken as an example, but the number of light beams is not limited as long as it is two or more light beams, and the effect of the present invention is not affected. Of course, the monitor light source may be the same type as the exposure laser (argon laser).
In addition, the present invention is effective even with a laser having an oscillation wavelength other than 488 nm as long as it matches the absorption band of the recording material. Furthermore, although an electro-optic light modulator has been described as an example of the light intensity modulator in this embodiment, an acousto-optic device or the like can also be used. Further, although the diffracted light of the monitor light source is monitored, the transmitted light may be monitored. When the transmitted light starts to decrease, it indicates that the diffraction grating has started to be manufactured.
FIG. 2 is a diagram for explaining a modification example targeting a part of the configuration shown in FIG.
In the configuration shown in the drawing, the propagation direction of the monitor light and the arrangement of the light receiving elements 19 are different from those of the first embodiment. That is, the propagation direction of the monitor light is completely opposite to the exposure beam from the mirror 16a. Therefore, it is parallel to the page.
When the diffraction grating starts to be produced on the recording material 17 with this arrangement, the monitor light is diffracted by the recording material 17 and proceeds to the mirror 16 b and the half mirror 15. Half the amount of light is reflected by the half mirror, and this reflected light is received by the light receiving element 19.

In this example , the incident angle (incident azimuth) of the monitor light can be completely matched with one side of the exposure beam. For this reason, the monitor optical system is optimal when strict monitoring is required.

Although not shown, when the voltage applied to the light intensity modulator 20 is not a single pulse, but the light intensity is attenuated by a repetitive pulse or a direct current voltage, A2 in (Equation 1) can be controlled to be small. .
The power density A2 may be reduced by increasing the beam diameter using an attenuation filter or a lens system instead of the light intensity modulator. This configuration corresponds to an embodiment of the invention as set forth in claim 3.
FIG. 3 is a diagram for explaining a modification example targeting a part of the configuration shown in FIG.
In this example , a semiconductor laser 31 is used as a monitor light source.
The exposure laser is a helium cadmium laser 33 (oscillation wavelength 633 nm), and a semiconductor laser having an oscillation wavelength of about 650 nm is used.

By using a semiconductor laser as the monitor light source, light pulses are emitted by controlling the injection current without using the light intensity modulator (or attenuation filter, lens system) used in the first and second embodiments. Or radiate with reduced light intensity. For this reason, the monitor optical system is simplified and reduced in size. The monitor light source can also use a light emitting diode.
Figure 4 is a diagram for explain the embodiment of the invention of claim 1, wherein. The same elements as those used in the configuration shown in FIG. 1 are indicated by the same numerals. The optical element 41 is used to extract a part of the light amount of the exposure light source 11. For example, a glass substrate can be used. The light reflected from the surface of the glass substrate is reflected by the mirrors 42a, 42b, 43a, 43b, and then irradiated to the recording material. Any number of mirrors may be used. The attenuation filter 44 is used when the power density of the monitor light is large. An optical system such as a beam expander may be used instead of the attenuation filter.

The coherence length represents the distance at which the phases of light are aligned.
Interference fringes can be generated by setting the optical path length until the laser beams are divided into two and overlapped again within the coherence length as in the two-beam interference exposure. A longitudinal single mode oscillation argon laser has a coherent length of about several meters.

  The exposure optical path length is the distance from the laser device 11 (strictly the glass substrate 41) to the half mirror and the mirror to the recording material 17, and the monitor optical path length is the mirror from the laser device 11 (strictly the glass substrate 41). The distance to the recording material 17 through 42a, 42b, 43a, 43b.

  The difference between the monitor optical length and the exposure optical length is set to a distance greater than the coherence length. Even if the monitor beam overlaps the two light beams for exposure in the recording material, the monitor light and the exposure light are not coherent and no interference fringes are generated. Therefore, the production status of the diffraction grating can be monitored without reducing the contrast of the exposure interference fringes.

  According to the present embodiment, a single light source can serve as both an exposure light source and a monitor light source, and there is no need to prepare a monitor light source. It is also possible to monitor without interrupting the interference exposure.

An application example targeting the configuration shown in FIG. 1 will be described below .
In FIG. 5, the reflected light of the glass substrate 41 is taken out for monitoring, and the plane of polarization is rotated 90 degrees using a λ / 2 plate (half-wave plate) 51. When the polarization direction of the beam emitted from the laser light source 11 is perpendicular to the paper surface of FIG. 5, the λ / 2 plate passes through the λ / 2 plate by setting the fast axis (or slow axis) of the λ / 2 plate to 45 degrees. The plane of polarization can be parallel to the plane of the paper. Since the light beams having orthogonal polarization planes have low coherence, the recording material 17 does not generate extra interference fringes.

According to such an application example , a single light source can serve as both an exposure light source and a monitor light source, so that it is not necessary to prepare a special monitor light source and the interference exposure system can be made compact. It is also possible to monitor without interrupting the interference exposure.
FIG. 6 is a view showing an embodiment according to the second aspect of the present invention .
The laser light source 61 includes a laser resonator in which a laser medium 62 is sandwiched between mirrors 63a and 63b. The mirror 63b is an output mirror that efficiently outputs laser light. On the other hand, the mirror 62a has a high reflectance with respect to the oscillation wavelength.

  However, although the light intensity is small, there is light that leaks outside from the mirror 63a. The recording material 17 is irradiated with this light using mirrors 64a, 64b, and 64c. A λ / 2 plate 51 is inserted into this optical path. The λ / 2 plate is not necessarily required if the power density of the monitor light is sufficiently small.

According to the application example described above , a single light source can serve as both an exposure light source and a monitor light source, and there is no need to provide a special monitor light source, and monitoring is performed without interrupting interference exposure. It becomes possible. Furthermore, it is not necessary to put a glass substrate or the like in the exposure beam in order to extract monitor light, and the quality of the exposure beam is not deteriorated.
7 and 8 are diagrams for further explaining another application example.
A light intensity modulator 72 is disposed on the light source side of the half mirror 15, and a shutter 71 is disposed on one side of the exposure beam. The light intensity modulator can be realized by an element using an electro-optic crystal as described above. The shutter 71 may be a mechanical shutter or a light intensity modulator.
In the case of a mechanical shutter, it is necessary to take measures against vibration. The light receiving element 19 is disposed so as to receive one transmitted beam of the exposure beam.
FIG. 7 shows the case of exposure.
The light intensity modulator 72 is highly transmissive and the shutter 71 is open. A diffraction grating is produced in the recording material 17 by two-beam interference. Next, the moment of monitoring will be described with reference to FIG. The shutter 71 is closed to shield one exposure beam. In synchronization with this, the light intensity modulator is driven to decrease the light intensity. The recording material 17 is irradiated with one light beam at a low power density, and this diffracted light (or transmitted light) is monitored. As another monitoring method, the light intensity modulator may irradiate the recording material 17 with a light pulse while the shutter 71 is closed. Both the low power density monitor and the monitor using light pulses are monitored so as to satisfy the above-described (Equation 1).

  Although not shown, in the case of interference exposure with three or more light beams, only one light beam is left and the remaining light beams are shielded by one or more shutters. By monitoring with one light beam, it is possible to monitor without generating interference fringes.

According to this application example, an exposure light source can be used without preparing a monitor light source, and monitoring can be performed without generating interference fringes by leaving only one exposure beam.
9 and FIG. 10 is a diagram for further explaining another application example.
A deflecting means 91 is disposed between the laser light source 11 and the spatial filters 12 and 13. As will be described later with reference to FIG. 11, this deflection means is an element that can switch the traveling direction of light. At the time of exposure, as shown in FIG. 9, the light 112a from the deflecting means passes through the spatial filter, the collimating lens 14, the half mirror, and the mirrors 16a and 16b to generate interference fringes at the position of the recording material 17, thereby producing a diffraction grating. Is done. On the other hand, at the time of monitoring, as shown in FIG. 10, the advancing direction of the laser beam is switched by the deflecting means 91 (112b), and irradiation is performed from the back side of the recording material 17 by the mirrors 92a and 92b. Reference numeral 44 denotes a light intensity modulator for reducing the power density of the monitor light. The individual light intensity modulators 44 are not necessarily required. That is, the light intensity modulator 44 can be omitted if the polarization means 91 can be driven at a speed capable of generating an optical pulse satisfying Equation 1.

  FIG. 11 is a diagram for explaining the deflection means 91 used in this embodiment. In order to switch the optical path of light, for example, an optical deflector using an acousto-optic element or an electro-optic element can be used. However, when the deflection angle is small, the deflection angle can be substantially increased by arranging a perforated mirror after the optical deflector as shown in FIG.

According to this configuration , even if a monitor light source is not prepared, it can be used as an exposure light source, and unnecessary interference fringes are not generated during monitoring.
FIG. 12 is a diagram for explaining still another application example .
In FIG. 12, the beam emitted from the laser 121 is converted into a 0th order beam transverse mode by a spatial filter, and the divergent light from the spatial filter is converted into a parallel light beam by a collimator lens. The parallel light is divided into two by the half mirror 124, and each recording beam 126 is irradiated to the recording material 126 at a predetermined incident angle using the mirror 125. The spatial filter includes an objective lens and a pinhole (not shown). Photoresist, photopolymer, etc. can be used as the recording material

  The beam B1 reflected by the mirror 125a and the reflected light B2 of the mirror 125b form interference fringes in a region where the both beams overlap (recording material 126). The refractive index is modulated in the recording material according to the bright and dark portions of the interference fringes. In the case of a photoresist, unevenness is recorded on the surface so as to follow the bright and dark portions of the interference fringes by developing after exposure of the interference fringes.

Here, the beam B3 is continuously present in the direction of transmitted light of the beam B1, and similarly, B4 is continuously present in the direction of transmission of the beam B2 during exposure.
In this configuration , as described with reference to FIG. 19, when a diffraction grating having a high diffraction efficiency is formed, one transmitted light is monitored because the sum of the zeroth order and first order efficiency is almost 100%. However, it is considered that it is impossible to know how much the diffraction grating has been created. For this reason, this embodiment is characterized in that the + 2nd order diffracted light beam B1 and the −1st order diffracted light beam B5 of beam 2 are not generated unless a diffraction grating is formed in the recording material portion 126. is there.
These diffracted light intensities (added values) are monitored by a light receiving element 127 (for example, a photodiode), and at the moment when the light intensity reaches a predetermined light intensity, the control circuit 128 is passed and the laser light is shut off by the electromagnetic shutter 129 to complete the exposure. Let

  According to such a configuration, since the monitor light uses the exposure beam as it is, it is not necessary to prepare it specially. Further, the light utilization efficiency of the exposure beam is not lowered by this monitoring method. In particular, when the exposure wavelength and the reproduction wavelength are the same, knowing the diffraction efficiency during actual use of the diffraction grating during exposure by simply knowing in advance the diffraction efficiency of the diffracted light to be monitored and the first-order diffracted light. Can do.

In this embodiment, the collimated light is used as the exposure beam. However, it is possible to achieve the intended purpose as divergent light or convergent light as required. That is, if the diffracted light for monitoring becomes divergent light, a lens (not shown) having an appropriate focal length (lens power) may be disposed between the light receiving element 127 and the recording material 126.
FIG. 13 is a diagram for explaining still another application example .

  In the figure, since the laser light source 121, the electromagnetic shutter 29, the spatial filter 122, and the collimating lens 123 are the same as those shown in the ninth embodiment, description thereof is omitted.

The diffraction grating 131 is used to branch the collimated light into three beams. The recording material 133 is irradiated with beams A, B, and C generated by the diffraction grating 131 at predetermined incident angles and azimuth angles, respectively.
As the diffraction grating, a so-called surface relief type diffraction grating having an uneven surface can be used.

  The efficiency of the beam B that is transmitted without being diffracted and the diffracted lights A and C are preferably about 30%. However, if the light intensity of at least A, B, and C is approximately 1: 1: 1, there is no particular problem in use even if each efficiency is less than 30%.

In the configuration shown in FIG. 13, the traveling directions of the beams A and C are changed using the mirrors 132a and 132b. As the recording material 133, for example, a photoresist can be used.

FIG. 14 is an enlarged view of the recording material portion.
In the figure, exposure beams A, B, and C are incident on the recording material portion 133.
The transmitted light from the recording material immediately after the start of exposure is three beams D1, D2, and D3. When the diffraction grating spectrally irradiates the three beams by exposure and starts to form replicas, the three transmitted beams include the following components.
(Transmission beam D1) = (Transmission light of beam A)
+ (+ 1st order diffracted light of beam B by diffraction grating formed by beams A and B)
+ (+ 1st order diffracted light of beam C by diffraction grating formed by beams A and C)
(Transmission beam D2) = (Transmission light of beam B)
+ (+ 1st order diffracted light of beam A by diffraction grating formed by beams A and B)
+ (+ 1st order diffracted light of beam C by diffraction grating formed by beams B and C)
(Transmission beam D3) = (Transmission light of beam C)
+ (+ 1st order diffracted light of beam A by diffraction grating formed by beams A and C)
+ (+ 1st order diffracted light of beam B by diffraction grating formed by beams B and C)
As described above, when a diffraction grating with high diffraction efficiency is formed, when the light intensity of the + 1st order diffracted light increases, the light intensity of the 0th order (transmitted) light decreases by the increase.

Even in the case of three-beam exposure, each of the transmitted lights D1, D2, and D3 has a small change in light intensity from the start of exposure to the time when the diffraction grating is being formed until after the formation.
For this reason, D1, D2, and D3 cannot be used as monitor light. However, diffracted light of orders other than the 0th order and the + 1st order can be used as monitor light even with three beams.
D4 is + second order diffracted light of the beam A by the diffraction grating formed by the beams A and B. This is received by the light receiving element 134 as monitor light.

  The control unit 135 generates a signal for closing the electromagnetic shutter 129 when the monitored light intensity reaches a predetermined value. In this embodiment, + 2nd order diffracted light is monitored, but -1st order diffracted light or other order diffracted light may be used. Further, when the light intensity of the diffracted light to be monitored is extremely small, it is desirable that the light receiving element 34 is a photomultiplier tube. Alternatively, a highly sensitive light receiving element such as a CCD, an avalanche photodiode, or a CMOS image sensor can also be used.

The diffraction grating 131 may have a configuration using two half mirrors. In this embodiment, the propagation directions of the two beams exist in one plane, but the intended purpose can be achieved without being in one plane. Further, the exposure with three beams is an example, and the effect of the present invention is not impaired even with four or more beams. As the recording material 33, a photopolymer, dichromated gelatin or the like can be used in addition to the photoresist.
FIG. 15 shows the measurement of the light intensity of a predetermined diffracted light excluding the 0th order light and the + 1st order light among the diffracted light generated from the recording material during exposure, and the light intensity is a predetermined value or a predetermined value. It is a figure for demonstrating the structure which interrupts | blocks the light from the said light source when a value is exceeded .
In the figure, the original diffraction grating 151 is disposed in the vicinity of the recording material portion 152.
A predetermined beam (parallel light in FIG. 15) 153 is incident on the original diffraction grating 151.
The original diffraction grating 151 generates zero-order light (transmitted light) and first-order diffracted light having an intensity ratio of about 1: 1. These two beams form interference fringes in the recording material portion 152, and the diffraction grating is duplicated. Even in this duplicate exposure, the beams 154a and 154b from the recording material 152 cannot be used as monitor light as described above. Therefore, it is effective to monitor the diffracted light of orders other than the 0th order and the 1st order diffracted light generated after the diffraction grating 151 starts to replicate.

In this configuration , the + 2nd order diffracted light 154c is monitored. In addition, since the structure and operation | movement from a light receiving element to an electromagnetic shutter are the same as that of the case shown in FIG. 12 and FIG. 13, description is abbreviate | omitted.
As the recording material 152, a photoresist, a photopolymer, dichromated gelatin, or the like can be used.

In this configuration, if + 2nd order diffracted light is present in the original diffraction grating 151, it is added to the monitor beam 154c. In this case, the electromagnetic shutter is controlled to be closed when the increase in the monitor light intensity reaches a predetermined value immediately after the start of exposure.
FIG. 16 shows the measurement of the light intensity of a predetermined plurality of diffracted lights excluding the transmitted diffraction first-order light and zero-order light generated from the recording material during exposure, and the sum of the plurality of diffracted light intensities or It is a figure for demonstrating the structure which interrupts | blocks the light from the said light source when a predetermined calculation value based on the light intensity of several diffracted light exceeds a predetermined value or a predetermined value . In FIG. 16, the same members as those used in the embodiments shown so far are indicated by the same reference numerals.

In the figure, the configuration and operation from the laser light source 121 to the recording material 126 are the same as those in the first embodiment, and thus the description thereof is omitted. In the beam generated from the recording material 126, D1 and D2 contain the 0th order light and the + 1st order light of the exposure beams B1 and B2, respectively, and thus cannot be used as monitor light.
Beams D3 and D4 are -1st order diffracted lights of B2 and B1, respectively. These two beams are received by the light receiving elements 161a and 161b, respectively. Based on the light intensities of the beams D3 and D4, the control unit 162 sends a control signal to the electromagnetic shutter 129 so as to close the electromagnetic shutter 129 at the moment when a predetermined calculation result reaches a predetermined value or exceeds a predetermined value. The predetermined calculation can be, for example, the total sum of the light receiving elements 161a and 161b. That is, the electromagnetic shutter is closed when the sum of the beams D3 and D4 exceeds a predetermined value. In addition to this, a control method may be used in which the light receiving signals of the beams D3 and D4 are each multiplied by a predetermined weight and then integrated, and the electromagnetic shutter is closed when the integrated value exceeds a predetermined value.

  In this configuration, two light receiving elements are used, but it is also possible to use one. For example, the beam D4 is guided to the light receiving element 161a using a mirror or the like. Then, the total of a plurality of predetermined monitor lights can be received by one light receiving element. If this light reception signal exceeds a predetermined value, control to close the electromagnetic shutter is performed.

The above configuration is particularly effective when the intensity of one monitor diffracted light is small and it is difficult to determine the timing for stopping exposure. When the light receiving element is a photomultiplier tube, a CCD, an avalanche photodiode, or a CMOS image sensor, a plurality of predetermined diffracted lights with low light intensity can be used as monitor light.

It is a figure for demonstrating the structure of the interference exposure apparatus used as the object of this invention. Modification of a part of the configuration targeted shown in FIG. 1 is a diagram for explaining the. It is a figure for demonstrating the modification which made a part of structure shown in FIG. 2 object . It is a diagram for explaining the engagement Ru embodiment to the invention of claim 1, wherein. It is a figure for demonstrating the application example aiming at the structure shown in FIG. It is a diagram for explaining the engagement Ru embodiment to the invention of claim 2 wherein. It is a figure for demonstrating the state at the time of the exposure in another application example with respect to the structure shown in FIG. FIG. 6 is a diagram for describing another application example for the configuration illustrated in FIG. 5 . FIG. 9 is a diagram for explaining another application example different from the configuration illustrated in FIG. 8 with respect to the configuration illustrated in FIG. 5 . FIG. 6 is a diagram for explaining yet another application example for the configuration shown in FIG. 5 . It is a figure which shows the structure of the deflection | deviation means used for the structure shown in FIG. It is a figure for demonstrating the application example different from the structure shown in FIG. It is a figure which shows the state at the time of monitoring in the further another application example of the structure shown in FIG. It is the figure which expanded the recording material part used for the structure shown in FIG. It is a figure which shows the state at the time of the monitor aiming at the structure for interrupting | blocking the light from a light source . It is a figure which shows the state at the time of the monitor aiming at another structure for interrupting | blocking the light from a light source . It is a figure which shows one of the structures of the conventional interference exposure apparatus with a monitor optical system. It is a figure which shows the structure of the separation regarding the interference exposure apparatus with the conventional monitor optical system. It is a schematic diagram which shows the permeation | transmission state of the diffracted light for demonstrating the reason the transmitted light (or diffracted primary light) of an exposure beam cannot be utilized for monitor light.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11,121 1st light source 12 Objective lens 13 Aperture 14 Collimating lens 15 Half mirror 16a, 16b Mirror 17, 126, 133 Recording material 18 2nd light source 19,127,134,161 Light receiving element 20 Radiation from 2nd light source Light intensity modulator that modulates light into pulses 129 Electromagnetic shutter 128, 135, 162 Controller

Claims (3)

An interference exposure apparatus that separates light emitted from a light source having coherence into two or more light beams, superimposes each light beam to generate interference fringes, and arranges a recording material on the interference fringes to produce a diffraction grating. In
A part of the amount of light from the light source is extracted , the extracted light is reflected to a plurality of mirrors, and the difference between the monitor optical path length and the exposure optical length is set to a distance equal to or greater than the coherence length of the light source, so that an optical pulse or low power An interference exposure apparatus that irradiates a recording material with a density and monitors transmitted light or diffracted light. The interference exposure apparatus according to claim 1, wherein
An interference exposure apparatus, wherein the light source is a laser light source that constitutes a laser resonator composed of two or more mirrors, and leakage light from a mirror other than the output mirror is used as monitor light . An image forming apparatus using the interference exposure apparatus according to claim 1 .

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