JP2005345930A - Lighting system, and nd filter used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting system with which durability is ensured, and a change in color temperature relative to a change in an amount of light is small and, moreover, fluctuation in an amount of light is also small. <P>SOLUTION: To adjust an amount of light emitted from the lighting system, an ND filter device 10 having a plurality of ND filters 11 is used. The ND filter 11 has: a metal film filter section 12 having a thin film of inconel alloy; and a correction filter section 15 that is substantially equal to a metal film filter section 12 in the absolute value of the ability to convert color temperature but opposite to the metal film filter section 12 in the positive/negative sign of the absolute value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an illumination device capable of changing the amount of light, an ND filter used for the illumination device, and an ND filter device including a plurality of the ND filters.

  When inspecting a color image sensor such as a CCD or CMOS, it is necessary to uniformly irradiate the color image sensor with various amounts of light. Also, in such inspections, insulation is performed by storing light up to the limit of the capacitor capacity of each element by irradiating light several thousand to several hundred thousand times the illuminance of light by normal imaging with a color image sensor. The so-called overflow check is performed. For this reason, in an illuminating device used for this type of inspection, generally, a very large amount of light is used to secure a very large amount of light, and the light from this light source is attenuated by a light amount attenuation filter. A weak amount of light is also secured.

  Conventionally, in the illumination device used for the inspection of the color image sensor, as the light amount attenuation filter, a color glass density filter using absorption or a metal film filter that reflects a part of light and has a small light absorption amount is used. .

  Moreover, there exists a thing of patent document 1 as an illuminating device which can adjust light quantity, without using the above filters. This illuminating device is provided with an aperture variable stop on the light source side of the integrator rod for eliminating unevenness of the light amount on the light irradiation surface, and adjusts the light amount by changing the opening size of the variable aperture stop.

Japanese Patent Laid-Open No. 2001-356203

  However, in the case of using a color glass density filter, there is a problem that when the amount of light to be absorbed increases, the filter has heat and breaks or changes its characteristics.

  In addition, in the case of using a metal film filter, since a part of light is reflected, the amount of light absorption is reduced, and there is no problem like a colored glass density filter, but the unit thickness depends on the physical properties of the metal film. The permeation transmittance varies depending on the wavelength. More specifically, even in the Inconel alloy thin film filter, which is said to have little change in wavelength characteristics, the transmittance on the short wavelength side is slightly smaller than the transmittance on the long wavelength side, and this tendency is a filter with high optical density. In this case, the wavelength distribution, in other words, the color temperature, changes between the light that has passed through the film having a high optical density and the light that has passed through the film having a low optical density, and effective inspection may not be performed. There is a problem. If the effective inspection cannot be performed due to the change of the color temperature, the color balance of the output signal of the color image sensor to be inspected may not be a desired balance.

  Further, in the illumination device described in Patent Document 1, an aperture variable aperture is provided on the light source side of the integrator rod, and the light receiving area on the light incident surface of the integrator rod changes, so that the light amount unevenness of the integrator rod is eliminated. Cannot be sufficiently obtained, and there is a problem that unevenness in the amount of light may occur. Further, there is a problem that it is extremely difficult to adjust the light amount necessary for the inspection, for example, 0.1 to 10,000 lux only by adjusting the size of the aperture stop.

  The present invention pays attention to the problems of the prior art as described above, and is an illuminating device that is durable, has a small change in color temperature with respect to a change in the amount of light, and also has a small amount of unevenness in the amount of light, an ND filter used therefor, and An object of the present invention is to provide an ND filter device including a plurality of ND filters.

The ND filter of the invention according to claim 1 for solving the above problem is
In the ND filter used for adjusting the amount of light,
A metal film filter for reducing incident light; and
The metal film filter unit includes a correction filter unit having substantially the same absolute value of color temperature conversion ability and having a positive / negative sign reversed.

The ND filter of the invention according to claim 2 is:
In the ND filter used for adjusting the amount of light,
A metal film filter for reducing incident light; and
And a correction filter unit that makes the transmittance combined with the metal film filter unit uniform in each wavelength region.

The ND filter of the invention according to claim 3 is:
The ND filter according to any one of claims 1 and 2,
The correction filter unit has a dielectric film.

The ND filter of the invention according to claim 4 is:
The ND filter according to claim 3,
The metal film of the metal film filter portion is formed on one surface of the front and back surfaces of a single substrate, and the dielectric film of the correction filter portion is formed on the other surface.

The ND filter device of the invention according to claim 5 for solving the above problem is
A plurality of the ND filters according to any one of claims 1 to 4,
Each metal film filter portion of the plurality of ND filters has a different optical density,
The plurality of ND filters are characterized in that the color temperature conversion ability of the correction filter section of each ND filter increases or decreases in response to an increase or decrease in optical density of the metal film filter section of each ND filter. To do.

The ND filter device of the invention according to claim 6 is:
The ND filter device according to claim 5,
In the plurality of ND filters, a change in the optical density D of the metal film filter portion of each ND filter and a change in the color temperature conversion ability V of the correction filter portion of each ND filter are approximately proportional to each other. And

The ND filter device of the invention according to claim 7 is:
The ND filter device according to claim 6,
The metal film filter portion has a metal thin film containing Inconel as a main component,
The proportionality coefficient V / D indicating the proportional relationship between the optical density D of the metal film filter section and the color temperature conversion ability V of the correction filter section is a value between −20 and −40.

The lighting device of the invention according to claim 8 for solving the above problem is
A light source that emits light;
The ND filter device according to any one of claims 5 to 7, which receives light from the light source;
A light quantity distribution averaging optical system for averaging the light quantity distribution of light that has passed through any one of the ND filters of the ND filter device;
It is characterized by having.

The lighting device of the invention according to claim 9 is,
The lighting device according to claim 8.
It is characterized by comprising a light amount fine adjustment filter whose optical density continuously changes with the change of position.

  According to the present invention, since the light amount is adjusted by the ND filter without adjusting the light amount by the aperture stop as in Patent Document 1 described in the section of the prior art, the light amount distribution averaging optical system such as an integrator rod is used. The light receiving area on the light incident surface does not change, and unevenness in the amount of light can be suppressed. In addition, although the ND filter of the present invention has a metal film filter portion having a color temperature change with respect to a change in optical density, a correction filter portion for correcting this color temperature change is provided. The color temperature does not change between when the metal film filter portion having a high optical density is used and when the metal film filter portion having a low optical density is used, and an effective inspection can be performed.

  Hereinafter, an embodiment of a lighting device according to the present invention will be described.

  The illumination device of the present embodiment irradiates light on a color image sensor such as a CCD or CMOS without any unevenness. As shown in FIG. 1, a light source 1 and a collector lens 2 for condensing light from the light source 1 The ND filter device 10 having a plurality of ND filters 11 on which light that has passed through the collector lens 2 enters, and the relay lens 4 that condenses the light that has passed through any one of the ND filters 11. A light amount fine adjustment filter device 20 for finely adjusting the light amount of light from the relay lens 4, an integrator rod 5 for averaging the distribution of the light that has passed through the light amount fine adjustment filter device 20, and the integrator rod A fly-eye lens 6 that further averages the light quantity distribution of the light from 5, a condenser lens 7 that condenses the light from the fly-eye lens 6, and It is provided.

  The ND filter device 10 includes a disk-shaped turret 18, the plurality of ND filters 11 provided on the turret 18, and a rotation motor 19 that rotates the turret 18. As shown in FIG. 2, each ND filter 11 includes a metal film filter unit 12 that attenuates incident light, and a correction filter unit 15 that uniformizes the transmittance in combination with the metal film filter unit 12 in each wavelength region. And a filter frame 17 for fixing them so as to be parallel to each other. The metal film filter unit 12 includes a substrate 14 and a thin film 13 formed of an Inconel alloy. The correction filter unit 15 includes a substrate 14 and a derivative film 16 formed of NbO, SiO2, or the like. A plurality of through holes 18 a are formed in the turret 18, and the ND filter 11 is disposed at a position corresponding to each through hole 18 a. The mutual relationship between the optical capabilities of the metal film filter unit 12 and the correction filter unit 15 will be described in detail later.

  The light amount fine adjustment filter device 20 includes a wedge filter 21 and a rotary motor 25 that rotates the wedge filter 21. As shown in FIG. 3, the wedge filter 21 includes a disk-shaped base 22 and a metal film 23 formed on one surface of the base 22. The thickness of the metal film 23 increases in proportion to the rotation angle with the center O of the base 22 as a reference. In other words, the optical density increases in proportion to the rotation angle with the center O of the base 22 as a reference.

  The intaglator rod 5 reflects the light incident obliquely with respect to the optical axis of the intaglator rod 5 on the side wall surface and emits it so as to overlap the light incident substantially parallel to the optical axis. This is intended to average the light amount distribution of the output light. The fly-eye lens 6 has a plurality of elementary lenses 6a, and the light incident on each elementary lens 6a is irradiated on the light irradiation surface 8 of the illumination optical device so as to overlap each other. The light quantity distribution on the light irradiation surface 8 is further averaged.

  Here, the mutual relationship between the optical capabilities of the metal film filter unit 12 and the correction filter unit 15 of the ND filter 11 will be described in detail.

  The attenuation rate of the amount of light due to the metal film is expressed by optical density. The relationship between the optical density D and the transmittance T is expressed by the following formula 1.

D = -log (T) (1)
Strictly speaking, the transmittance of the metal film varies depending on the wavelength, but in the case of a so-called neutral density film such as Inconel, the transmittance around 550 nm is generally handled as the representative transmittance. This optical density D is proportional to the thickness of the thin film.

  FIG. 4 shows the relationship between each wavelength and transmittance ratio (= actual transmittance / representative transmittance) of an Inconel alloy thin film having various optical densities (OD: Optical Density). As shown in the figure, in the case of an Inconel alloy thin film, the higher the optical density, the lower the transmittance on the short wavelength side and the higher the transmittance on the long wavelength side. Further, when paying attention to a thin film having a certain representative transmittance, the transmittance on the short wavelength side tends to decrease almost linearly according to the wavelength. For this reason, when it is desired to make the transmittance distribution of a thin film having a certain representative transmittance uniform, a color temperature correction filter whose transmittance decreases almost linearly as the wavelength increases may be used as the correction filter unit 15.

  As defined in JIS B7125, the color temperature conversion capability V of the color temperature correction filter is the average value Tr of the filter transmittance at wavelengths 610 nm, 635 nm, and 655 nm, and the filter temperature at wavelengths 405 nm, 435 nm, and 465 nm. From the average value Tb of the transmittance, it is expressed by the following (Equation 2).

V = 221 * (log (Tr) -log (Tb)) ... (Equation 2)
The color temperature conversion ability V indicated by (Equation 2) is basically the difference between the average values of the transmittances at two locations having different wavelengths, and thus represents the slope of the transmittance characteristics in FIG. It will be. Therefore, when the correction filter unit 15 wants to uniformize the transmittance distribution of a thin film having a certain representative transmittance, the color temperature correction filter in which the absolute value of the color temperature conversion ability is substantially the same and the sign of the sign is reversed. It can be said that it is sufficient to use. According to the definition shown in (Equation 2), when the sign of the color temperature conversion ability V is positive, it indicates that the function of lowering the color temperature of the transmitted light is provided, and conversely, the sign of the color temperature conversion ability V is negative. In this case, it indicates that it has a function of increasing the color temperature of transmitted light.

  In FIG. 5, the horizontal axis represents the optical density of various inconel alloy thin films, and the vertical axis represents the color temperature conversion ability of the color temperature correction filter required to make the spectral distribution uniform by the inconel alloy thin film, in other words, The value obtained by reversing the sign of the color temperature conversion ability of the Inconel alloy thin film is taken. As shown in the figure, for example, the color temperature conversion ability of the color temperature correction filter required to make the spectral distribution uniform by an Inconel alloy thin film having an optical density of 0.9 is about −12. The color temperature conversion ability of the color temperature correction filter required for making the spectral spectrum distribution uniform by the 2.7 Inconel alloy thin film whose optical density is three times 0.9 is almost three times that of -12. Since it is about −65, it can be seen that the color temperature conversion capability required to correct the optical characteristics of the Inconel alloy thin film is substantially proportional to the optical density. It can also be seen that this proportionality coefficient takes a value between -20 and -40.

  As described above, in the present embodiment, the absolute value of the inconel alloy thin film 13 and the color temperature conversion capability is substantially equal to the metal film filter portion 12 having the inconel alloy thin film 13 having a certain representative transmittance. A correction filter unit 15 having the same positive and negative signs and reverse signs is used. In addition, the plurality of ND filters 11 included in the ND filter device 10 of the present embodiment are configured so that the correction filter unit 15 of each ND filter 11 corresponds to a change in the optical density D of the metal film filter unit 12 of each ND filter 11. The change in color temperature conversion ability V is proportional.

  Next, the operation of the illumination device of this embodiment will be described.

  The light from the light source 1 is attenuated by one ND filter 11 among the plurality of ND filters 11 of the ND filter device 10, and then passes through any part of the wedge filter 21 of the light amount fine adjustment filter device 20. Further dimmed. In order to change the light from the light source 1 to a desired illuminance at the irradiation surface 8 by this dimming process, first, among the plurality of ND filters 11 of the ND filter device 10, the desired illuminance at the irradiation surface 8. The ND filter 11 that can obtain slightly bright light is selected, and the turret 18 is rotated so that the ND filter 11 is positioned in the optical path of the illumination device. Further, the position of the wedge filter 21 where the light having passed through the ND filter 11 obtains a desired luminous intensity at the irradiation surface 8 is determined, and the wedge filter 21 is rotated so that this position is located in the optical path of the illumination optical device.

  The light that has passed through the wedge filter 21 enters the integrator rod 5. In the integrator rod 5, as described above, the obliquely incident light is reflected by the wall surface and overlaps with the light incident on the exit surface of the integrator rod 5 almost in parallel with the optical axis, and the illuminance is averaged. . The light emitted from the integrator rod 5 further enters the fly-eye lens 6. The lights incident on the plurality of elementary lenses 6a constituting the fly-eye lens 6 overlap each other on the irradiation surface 8 and are further averaged.

  Thus, in this embodiment, since the light quantity is adjusted by the ND filter 11 without adjusting the light quantity by the aperture stop as in Patent Document 1 described in the section of the prior art, the light incident surface of the integrator rod 5 is adjusted. In this case, the light receiving area does not change and unevenness in the amount of light can be suppressed. In particular, in this embodiment, since the fly-eye lens 6 is used in addition to the integrator rod 5 in order to suppress the light amount unevenness, the light amount unevenness can be extremely reduced.

  In the present embodiment, although the metal film filter unit 12 having a color temperature change with respect to the change in optical density is provided, the correction filter unit 15 for correcting the color temperature change is provided. When the metal film filter unit 12 having a high optical density is used and when the metal film filter unit 12 having a low optical density is used, there is almost no change in the color temperature, and an effective inspection can be performed.

  By the way, since the wedge filter 21 uses the metal film 23 as described above, similarly to the metal film filter portion 12 of the ND filter 11, the transmittance varies depending on the wavelength. However, even at the highest optical density portion of the wedge filter 21 used for fine adjustment of the light amount, the optical density is relatively low, so the amount of change in transmittance according to the wavelength does not affect the inspection. Specifically, as shown in FIGS. 4 and 5, the optical density is 0.45, 0.9, 1.35, 1.45 as each metal film filter unit 12 of the plurality of ND filters 11. When an optical density difference of 0.45 is used, the optical density range necessary for adjusting the amount of light with the wedge filter 21 is 0 to 0.45. For this reason, even in the portion having the highest optical density in the wedge filter 21, the optical density is 0.45, the color temperature conversion ability at that time is 5 or less, and the optical density in FIG. 4 is 0.45. Similar to the transmittance characteristic, the change in transmittance according to the wavelength is extremely small. Therefore, even if a metal film is used for the wedge filter 21, the inspection is hardly affected.

  In the present embodiment, the correction filter unit 15 having the substrate 14 and the derivative film 16 formed on the substrate 14 is used. However, the present invention is not limited to this. You may use the color glass filter which has the target color temperature conversion ability. However, when manufacturing an ND filter having a low optical density, that is, a high transmittance, it is preferable to use the dielectric film 16 that does not substantially absorb light in terms of durability. Further, in the above embodiment, the Inconel alloy is used as the metal film 13 of the metal film filter unit 12, but other materials such as chromium and silver may be used. In this case, needless to say, it is naturally necessary to examine the transmittance characteristic according to the wavelength of the material and use the correction filter unit 15 according to the transmittance characteristic.

  Further, in the ND filter 11 of the above embodiment, the metal film filter unit 12 and the correction filter unit 15 have their own substrates 14 and 14, respectively, and the films 13 and 16 are formed thereon, As shown in FIG. 6, the metal thin film 13 may be formed on one surface of a single substrate 14, and the derivative film 16 may be formed on the other surface, thereby forming the ND filter 11a. By configuring the ND filter 11a in this way, it is possible to reduce the weight and cost of the ND filter device. However, as in the present embodiment, when the metal film filter unit 12 and the correction filter unit 15 are formed with their own substrates 14 and 14, the optical performance of the filter units 12 and 15 will vary in manufacturing. There is also an advantage that the filter part can be easily replaced.

  In the above embodiment, the relative position of the correction filter unit 15 with respect to the metal film filter unit 12 does not change. For example, as shown in FIG. 7, a plurality of metal filter units with different optical densities are used. A first turret 18 a having 12, a second turret 18 b having a plurality of metal filter parts 12 having different optical densities, and a third turret 18 c having a plurality of correction filter parts 15. A plurality of correction filter portions 15 whose relative positions change may be provided for each metal filter portion 12 of one turret 18a and each metal filter portion 12 of the second turret 18b. In this case, a combination of the plurality of metal filter portions 12 of the first turret 18a and the plurality of metal filter portions 12 of the second turret 18b can ensure more optical density, and the first turret 18a The third turret includes a plurality of correction filter portions 15 that correct the transmittance characteristics for all optical densities generated by the combination of the plurality of metal filter portions 12 and the plurality of metal filter portions 12 of the second turret 18b. 18c.

It is explanatory drawing which shows the structure of an illuminating device as one Embodiment which concerns on this invention. It is sectional drawing of an ND filter as one Embodiment concerning this invention. It is a top view of a light quantity fine adjustment filter device as one embodiment concerning the present invention. It is explanatory drawing which shows the transmittance | permeability ratio with respect to the wavelength of the Inconel alloy thin film of each optical density. It is explanatory drawing which shows the color temperature conversion capability required in order to correct | amend the transmittance | permeability characteristic of the Incone alloy thin film of each optical density. It is sectional drawing of the ND filter as other embodiment which concerns on this invention. It is explanatory drawing which shows the structure of the ND filter apparatus as other embodiment which concerns on this invention.

Explanation of symbols

1: Light source 5: Integrator rod 6: Fly eye lens 8: Irradiation surface 10: ND filter device 11, 11a: ND filter 12: Metal film filter part 13: Inconel alloy thin film 14: Substrate 15: Correction filter part 16: Dielectric Body membrane 18: Turret 20: Fine adjustment filter device 21: Wedge filter

Claims (9)

In the ND filter used for adjusting the amount of light,
A metal film filter for reducing incident light; and
The metal film filter unit, and a correction filter unit having substantially the same absolute value of color temperature conversion ability and a reverse sign.
An ND filter comprising: In the ND filter used for adjusting the amount of light,
A metal film filter for reducing incident light; and
A correction filter unit that makes the transmittance combined with the metal film filter unit uniform in each wavelength region;
An ND filter comprising: The ND filter according to any one of claims 1 and 2,
The correction filter unit has a dielectric film,
An ND filter characterized by that. The ND filter according to claim 3,
Of the front and back surfaces of one substrate, the metal film of the metal film filter portion is formed on one surface, and the dielectric film of the correction filter portion is formed on the other surface.
An ND filter characterized by that. A plurality of the ND filters according to any one of claims 1 to 4,
Each metal film filter portion of the plurality of ND filters has a different optical density,
In the plurality of ND filters, the color temperature conversion ability of the correction filter unit of each ND filter increases or decreases in response to the increase or decrease of the optical density of the metal film filter unit of each ND filter.
An ND filter device. The ND filter device according to claim 5,
In the plurality of ND filters, the change in the optical density D of the metal film filter portion of each ND filter and the change in the color temperature conversion ability V of the correction filter portion of each ND filter are substantially proportional to each other.
An ND filter device. The ND filter device according to claim 6,
The metal film filter portion has a metal thin film containing Inconel as a main component,
A proportional coefficient V / D indicating the proportional relationship between the optical density D of the metal film filter portion and the color temperature conversion ability V of the correction filter portion is a value between −20 and −40.
An ND filter device. A light source that emits light;
The ND filter device according to any one of claims 5 to 7, which receives light from the light source;
A light quantity distribution averaging optical system that averages the light quantity distribution of light that has passed through any one of the ND filters of the ND filter device;
A lighting device comprising: The lighting device according to claim 8.
A light amount fine adjustment filter whose optical density continuously changes with a change in position is provided.
A lighting device characterized by that.

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