JPS59214840A - Projector - Google Patents

Abstract

PURPOSE:To obtain an image with a proper illuminance distribution on a projection surface by controling a member which measures the distribution of the quantity of light passed through a projection lens and varies the illuminance distribution on the projection surface on the basis of the measured value. CONSTITUTION:A filter 100 consists of a circular density filter which has the smallest light transmissivity at the center part and increases in light transmissivity gradually from the center part to the circumferential part. When a motor 218 is rotated through a motor driving circuit with a start signal, the filter 100 starts rotating as shown by an arrow M. A detection signal is outputted when difference in output between the 1st photoelectric converting element 200 and the 2nd photoelectric converting element 201 arranged behind a half-mirror 108 is minimized, and the motor 218 is stopped through the motor driving circuit with the signal. Consequently, the unevenness of the illuminance distribution on the projection surface is corrected to adjust a light system correctly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a projection device such as a reader or a copying machine that projects an image of a document such as a microfilm or a single sheet of paper onto a projection surface.

In a microfilm reader or reader printer, the image recorded on the microfilm is enlarged and projected onto a screen using a projection lens, and the image projected on the screen is read, or the image is projected onto a photoreceptor using a reader printer. I'm trying to get a copy of that.

Since there are generally various reduction wheels for images recorded on microfilm, it is necessary to change the projection magnification depending on the microfilm used.

In a variable magnification projection device, when the magnification is changed and the optical path length ratio before and after the lens is changed, the distribution of image light amount (illuminance distribution) on the projection surface of the screen or photoreceptor changes before and after changing the magnification. As a result, the image quality fluctuates, and the characteristics of the photoreceptor also change. In order to solve this problem, it is known that a slit exposure copying machine moves a different slit plate in and out of the optical path each time the magnification changes, but this requires a mechanical structure that detects the change in magnification. Not only is this method complicated and large, but the shape of each slit plate must be slightly changed, which complicates the device configuration and raises the cost.

Furthermore, although there is a known method that changes the light emission distribution of the document illumination lamp according to the magnification, it is not possible to perform sufficient □ correction.

It is still known to correct the illuminance distribution on the projection plane by moving a condenser lens or lamp in conjunction with changes in magnification; a mechanism for detecting doubling when the number of magnifications that can be changed increases, and an interlocking mechanism. There are disadvantages in that the process becomes complicated and the device becomes large.

The purpose of the present invention is to eliminate the above drawbacks, measure the distribution of light passing through the projection lens, and change the illuminance distribution on the projection surface based on the measured value. An object of the present invention is to provide a projection device capable of obtaining an image with an appropriate illumination distribution on a surface.

The present invention can be applied to copying machines that use manuscripts such as film readers, reader printers, and nine documents.
Further, the Surin t-f4 can be applied to any copying method, such as a light type or an entire surface simultaneous exposure type.

Hereinafter, the present invention will be explained with reference to a specific example shown in the drawings. Fig. 1 shows a reader printer to which the present invention is applied, and the entire body consists of an upper machine box 101 and a lower machine box 102.

Inside the lower machine box 102 are a reflective spherical mirror 99 and a lamp 1.
03, filter 100, condenser lens 104,
Illumination means composed of a reflecting mirror 105 and a condenser lens 106 is provided. Inside the upper machine box 101 is an optical system having a projection lens 107 and a half mirror 108;
Reflective screen 1 that receives light reflected by mirror 108
09, copy paper supply cassette) 110, charger 112, feed roller 111. Driving bell) 'l 3s mPaper roller 135 and feed roller 145.146. l 4
8, and a developing means having a developer tank 114, a developing roller 115, etc. are provided.

Between the second condenser lens 106 and the projection lens 107 is disposed a fish carrier 116 that holds two glass plates G, G2 that sandwich the microfiche film, and this carrier 116 is attached to the lower machine box 1.
It is configured to be movable above 02. By operating the moving handle 117, the carrier 116 can be moved back and forth.
When moved from side to side, the microfiche film moves together with the carrier, and a specific frame of this film can be positioned within the projection optical path.

An observation opening for looking into the inside of the machine box 1O1 is formed on the front surface of the upper machine box, and a shutter 118 is disposed in the inner opening. The shutter 118 is made of a member that controls transmitted light so as to block external light entering the machine box through the observation opening when copying a projected image, or to transmit image light when observing a projected image, For example, it consists of a filter made of a material whose transmission wavelength changes when energized, such as liquid crystal or electrochromic material, and an opening/closing plate.

Note that this filter is preferably colored appropriately so as to optimize the contrast of the image when the image projected on the screen is viewed through the filter. As a filter, for example, "Varad" (Marks Po1ar
ized Corp. (trade name) is used. this is,
It consists of a plate-like body with a dipole suspended between a pair of transparent electrodes, and when electricity is applied between this pair of electrodes, a mountain pole is formed.
are arranged at right angles to the electrodes, and light passes through this plate-like body, and when the electricity is turned off, the dipole enters a scattering state and controls the transmitted light so that no light is transmitted.

When the device is switched to reading mode, the shutter 118 is in a light-transmissive state and the screen 10 is in a light-transmissive state.
The film is placed on a projection plane onto which the image of the film is formed by a nine-point optical system, so that the projected image on the screen can be read through the viewing aperture.

The reflective screen 109 reads this forwardly incident light image from the same side, and is attached to a drive bell (113) that conveys copy paper, and as a reflective screen 109 that moves integrally with this belt. Paper with a light-diffusing surface, white cloth with a rough surface, or the like is pasted on the drive belt, or a light-diffusing substance is coated on the drive belt surface. The drive bell) 113 is provided with a hole 121 for positioning the screen, and when this hole is detected by the micro switch S, the belt stops.
The screen 109 is located at the location indicated by the solid line in FIG.
placed on the projection surface. SWI is a microswitch for detecting copy paper and is disposed near the edge of the exposure plane.

The copy sheets S are stacked and stored in a supply container 110. As this copying paper, so-called electrofax paper, which has a base paper coated with zinc oxide, is used. When the copy button is operated to command copying, one sheet of copy paper S in the cassette 110 is fed out by the rotation of the published paper feed roller 135,
11, then sent by feeding rollers 111, 111, uniformly banded by a charger 112 to impart photosensitivity, then fed by a drive belt 113 and a guide roller 136, and then sent to a guide plate. 137 to the surface of the drive bell) 113. bell) 113 is configured endlessly, and rollers i3g, 139 . [Moving roller 140
It is stretched in a triangular shape and is driven by the rotation of a drive roller 140 connected to a drive source. 141
(Bell) 113 is a tension adjustment roller. A large number of slots are formed in several rows on the surface of the drive belt 1130, and a suction device 1 having a large number of suction holes on the surface facing the belt is located inside the bell 113 opposite to the oblique side of the triangular shape.
41 is arranged, and a blower 142 is coupled to this suction device 141.

When the floor 142 is driven, due to the suction action of the suction device,
The copy paper S fed into the oblique side of the triangle by the belt 113 and the guide roller 136 is fed in close contact with the surface of the drive belt 1130 and guided to the projection plane.

The projection plane is located at a position that approximately coincides with the inclined surface of the drive bell) 113.
It is in. The screen has a thickness of about 1 mm, and the copy paper S has a thickness of about 0.1 mm, but if the optical system focuses the image on the projection plane, the screen and copy paper will have a depth of focus of the lens. There is no need to adjust the lens when switching modes.

When the leading edge of the copy paper S comes into contact with the microswitch SWI, the drive belt 113 stops. On the other hand, shutter 118
is switched to a state in which light is blocked by a copy command.

With the above, the mode has been changed from reading mode to copying mode.

When the copy paper S is placed on the projection surface, the image on the film is projected, and when the exposure is completed, the belt 113 is driven again.
The copy paper S on which a latent image has been formed by exposure is transferred to the belt l13.
The paper is sent obliquely upward by the rollers 143 and the belt, and is then discharged from between the pinch roller 143 and the belt, and then proceeds along the guide plate 144 and is sent between the feed rollers 145 and 145.

On the other hand, the drive bell) 113 continues to drive, and the drive bell) 113
When the microswitch SW2 detects the positioning hole 121, it stops. As a result, the screen is again placed on the original projection surface.

When the screen 109 is still located on the projection surface, the shutter 118 is switched to a state that transmits light. Feed roller 1
The copy paper S sent by 45, 145 is transferred to the developing roller 1.
15, and then the feed rollers 146, 14
The outlet 14 of the machine box lot is temporarily guided between the guide plates 1470 by the ejection rollers 148 and 148.
9 to the tray 150 on the machine box 101. The image forming process described above is well known and will not be described in detail.

The light emitted from the illumination lamp 103 passes through a filter 100, a first condenser lens 104, and a first reflecting mirror 10.
5 changes the direction by 90, and the second condenser lens 10
6 and forms a filament image of the illumination lamp 103 in the pupil on the film side of the projection lens 107 disposed above. The projection lens 107 can be replaced with lenses of various focal lengths, and the projection magnification can be changed by replacing the lenses.
wealth) can be done. Each interchangeable lens is designed so that the position of the pupil on the film surface side is approximately the same, so that the brightness (illuminance) of the projection surface does not change much due to lens exchange.

Behind the half mirror 108, a first photoelectric conversion element 200 is placed at a position corresponding to the vicinity of the optical axis of the projection lens 107, and a second photoelectric conversion element 201 is placed at a position corresponding to the vicinity of the periphery of the projection lens 107. .

FIG. 2 shows the illumination unit, in which the filter 100 is fixed to a support block 217 with a female threaded hole, and a threaded rod 2 directly connected to a motor 218 that rotates forward and backward.
The male screw portion 219a of No. 19 is fitted into the female screw hole of the block 217. When the motor 218 rotates, the threaded rod 219 rotates, and the rotation of the threaded rod 219 causes the block 2 to rotate.
17 moves along the threaded rod 219, so that the filter 100 connects the lamp 103 and the first condenser lens 1.
04 in the optical axis direction of the illumination optical path. Limit switches 220 are installed at both ends of the movement range of the block 217.
A block 217Fi limit switch 221 and a limit switch 221 are arranged, and move between block 217Fi limit switches 220 and 221, and limit the movement range of the block by both limit switches.

7 (The Luther 100 has a circular shape and consists of a density filter with the smallest light transmittance in the center and gradually increasing light transmittance from the center to the periphery. Figure 3 shows the light transmittance of the filter 100. The light transmittance is the lowest at the center of the filter, and gradually increases toward the periphery of the filter.

FIG. 4 shows a block diagram of a control circuit for correcting the illumination distribution on the projection plane. In Figure 4, 200,2
01 is the photoelectric conversion element shown in FIG. 1, 223 is a subtraction circuit that calculates the difference between the output voltage of the second photoelectric conversion element 201 and the output voltage of the first photoelectric conversion element 200, and 224 is a calculated value of the subtraction circuit 223. 225 is a peak detection circuit that detects the peak value of the output signal of the bias circuit 224; 226 is a peak detection circuit that drives the motor 218 shown in FIG. 2; The motor 1 drive circuit 227 to control receives the outputs of the limit switches 220 and 221 shown in FIG.
A rotation direction switching circuit 228 outputs a signal for switching the rotation direction of the motor 218, and a start command switch 228 operates the peak detection circuit 225 and outputs a start signal for instructing the motor 218 to start driving. .

5-4-0 show the output signals of each part of the control circuit when the lamp 103 is turned on without a film placed in the carrier 116 and the filter 100 is moved from the X position shown in FIG. 2 along the Z position line. In this figure, the horizontal axis represents the position of the filter, and the vertical axis represents the output voltage of the valley block.

In FIG. 5(5)9, the song J9200' shows the output part LE of the first optical branch conversion element 200, and the curve 201' shows the state of change in the output voltage of the second photoelectric conversion element 201. The photoelectric conversion elements 200 and 201 have the same output voltage when the amount of light received is large, and the output voltage is low when the amount of light received is small. 5 (0 is the output of the bias circuit 224 (0 is the output of the peak detection circuit 225)
shows the output of

Next, the operation of the above device will be explained. Assume that the filter 100 is at the position (X) shown in FIG. 2 when the observer turns on the power switch (not shown) and turns on the illumination lamp 103 without putting any film into the fish carrier 116. At this time, the first photoelectric conversion element 200 and the second photoconversion element 201 placed behind the half mirror 108 output voltage (a) on point (X) in FIG. 5(5).
) and (b) respectively. The subtraction circuit 223 subtracts the difference between the output voltage (b) of the second photoelectric conversion element 201 and the output voltage (a) of the first photoelectric conversion element 200, and the subtracted value (ba) is shown in FIG. The voltage becomes C as shown in .

The bias circuit 224 applies a certain bias voltage to the output of the subtraction circuit 223, and converts the negative output voltage C of the subtraction circuit 223 into a positive voltage d as shown in FIG. 5(C). This output of bias circuit 224 is sent to peak detection circuit 225.

Next, when the observer presses the start switch 228, a start signal is generated, and this signal causes the motor 218 to rotate via the motor drive circuit 226, and at the same time, the peak detection circuit 225 starts operating. As a result, the filter 100 begins to move in the direction of arrow M (FIG. 2). Due to the movement of the filter, the outputs of the first photoelectric conversion element 200 and the second photoelectric conversion element 201 are changed to the subtraction circuit 223, the bias circuit 224, and the peak detection circuit. The output of the filter 225 changes as shown in the graphs shown in FIG. Two photoelectric conversion elements 200.20
When the output difference of 1 is least noticeable, the illuminance distribution on the projection surface (or film surface) becomes less uneven, and at this time the filter is positioned correctly. That is, when the filter 100 reaches point (Y), a peak is detected by the peak detection circuit 225 (each photoelectric conversion element 200,
201), a peak detection signal e is output from the peak detection circuit 225, and this signal stops the motor 21B via the motor drive circuit 226. This means that the unevenness of the illuminance distribution has been corrected, and the illumination system has been correctly matched. Then, the observer inserts the film into the fish carrier 116,
Films can be observed under optimal conditions.

In the explanation of the above embodiment, the peak value could be detected immediately by driving the motor, but if the starting position of the filter 100 and the moving direction of the filter 100 are not appropriate, when the limit switch 2SO or A reversal signal is sent to 227, which sends a signal to switch the rotation direction of the motor to the motor drive circuit 226.
The rotational direction of the motor 218 is reversed, the above-mentioned peak detection operation continues, and when the peak is detected, the motor 21
8 stops.

In the above embodiment, the motor rotates in one direction at first, and when the peak value cannot be detected, the limit switch is used to reverse the motor. By comparing the values, you can change the direction of rotation of the motor so that it always reaches the peak value in the shortest possible time.

That is, for example, the first output value of the subtraction circuit before the motor is driven and the second output value of the subtraction circuit immediately after the motor has been driven are compared, and the second output value is equal to the first output value. If it is larger, drive the motor in the same direction and
If the output value is smaller than , just drive the motor in the opposite direction.

In the above embodiment, the filter was placed between the lamp and the first condenser lens, but the filter e[2 may be placed between the condenser lens and the film mounting surface. 6 shows another embodiment of the filter, in which a large number of filters 3oo, -3oo are arranged on the same circle on a circular plate 3ol. The disc 301 is connected to a motor,
The motor rotates it about the axis 302 so that a selected filter is placed in the illumination optical path between the lamp 103 and the first condenser lens 1040 .

Each filter 300. ~300. have different light transmittance distribution characteristics. In the figure, the light transmittance is low in the areas indicated by dots, and the amount of light transmission gradually increases from the center to the periphery of the filter. The motor that rotates the disk 301 has two photoelectric conversion elements 2 as in the previous embodiment.
A filter that is controlled based on the difference between the outputs of 00 and 201 and that provides an appropriate illuminance distribution on the projection plane is selectively placed in the illumination optical path.

FIG. 7 shows another embodiment of the illumination unit for correcting the illuminance distribution, and the same parts as in the previous embodiment are designated by the same reference numerals. The difference from the illumination section in Fig. 2 is that the filter 4
00 in FIG. 7 is the first condenser lens 104 (!
: Disposed between 282 condenser lenses 106,
The difference lies in the structure of the filter from that in FIG.

In FIG. 7, filter 400 is fixed in a fixed position. FIG. 8 shows a first filter 400. The filter 400 consists of an annular color-changing plate a-
g, and each color change plate is spaced apart and individually transparent or opaque 0 filter 400 is placed in the illumination optical path through which the parallel light beam passes, and each color change plate has a 1 Transparent electrodes 401a, 401b...40
1g and second transparent electrodes 402a, 402b...
...LCD 403a, 403b between 402g...
...It has a structure that holds 403g. Note that it is preferable to provide the filter 400 at a position close to the second condenser lens to prevent it from being heated to a high temperature, and it is also preferable to provide a heat insulating filter in front of the filter. When voltage is applied between opposing electrodes (for example, 401a and 4028'), the liquid crystal (403a) between them changes color, and the color-changing plate (a) becomes opaque, but when no voltage is applied, the color-changing plate becomes transparent. . When the color-changing plate becomes opaque, the amount of light transmitted through that area decreases. By sequentially changing the color of each color-changing plate from the central color-changing plate to the peripheral color-changing plate, the shift filter 4
00 light transmission distribution can be changed.

FIG. 10 shows a control circuit for changing the light transmission distribution of the filter 400, and the same parts as in FIG. 4 are omitted. 410 is the peak detection circuit 22 shown in FIG.
5 and a liquid crystal drive circuit connected to the start command switch 228. The liquid crystal drive circuit 410 has a pair of electrodes (hereinafter, a', b', a', a',
The electrodes are connected to a group of electrical terminals 405 (referred to as f'2g'), and voltages are sequentially applied to electrodes a to g in this order.

- The electrode to which a variable voltage is applied continues to be energized even when the next electrode is energized.

After voltage is applied to all electrodes a' to g', no voltage is applied to all electrodes, then voltage is applied only to electrode a' again, and then voltage is applied sequentially to electrodes b' to g'. applied,
Thereafter, the above-described operation is repeated, and when the peak detection circuit 225 outputs the first peak signal, the voltage application to the next electrode is stopped.

In the above embodiment, when projecting a film image onto a screen or a projection surface on which photosensitive paper is placed, for example using a short-focus projection lens, only a narrow area of the film ( (hereinafter referred to as an effective projection area) is projected onto the projection plane at high magnification. In this case, since the difference between the outputs of the first and second photoelectric conversion elements 200 and 201 is small, a voltage is applied to about one or two color changing plates near the center of the filter 400, and the center of the effective projection area is The illuminance distribution on the projection plane is corrected by making only the color-changing plate corresponding to the nearby area opaque, reducing the amount of light passing near the center of the illumination optical path (the amount of light in areas other than the center of the illumination optical path does not change). do. In addition, when projecting the image of the film onto the projection surface using a projection lens with a long focal point, the effective projection area of the film becomes wider than in the above-mentioned case. Since the difference in output is larger than in the above case, a voltage is applied to a plurality of color changing plates, which is larger than in the above case, from the center to the vicinity of the center of the filter 400, and the voltage is applied to the center of the effective projection area and its surroundings. The corresponding color-changing plate is made opaque to reduce the amount of light passing through the center and surrounding areas of the illumination optical path (the amount of light in other parts of the illumination optical path remains unchanged), thereby correcting the illuminance distribution on the projection plane. Make it.

In the above embodiment, liquid crystal is used as the color-changing material of the color-changing plate, but it is also possible to use a material whose light transmission characteristics change reversibly, such as an electrochromic material, a photochromic material, or the above-mentioned Arad. Furthermore, the light transmittance of the color-changing material such as liquid crystal can be changed by changing the voltage applied to a pair of transparent electrodes constituting the color-changing plate. Also, the filter 100 shown in FIG.
It is also possible to combine the filter 400 shown in FIG. 7 with the filter 400 shown in FIG. 7 to correct unevenness in the illumination distribution on the projection plane.

Note that the arrangement positions of the first and second photoelectric conversion means for measuring the amount of light are not limited to those in the embodiment.

Alternatively, the amount of light may be measured by a photoelectric conversion element through a lens. In addition, photometry and control are started by operating the start command switch, but it is also possible to generate a start command signal in conjunction with the operation of the power switch, or to generate a start command signal in conjunction with the replacement of the projection lens. The photometry/secondary side 1 may be started by a start command signal.

Figure 11 shows an example of a peak detection circuit, with 450
4 is a delay circuit that delays the output of the bias circuit 224;
51 is a comparator that compares the output of the output circuit 224 and the output of the delay circuit 450; Comparator 451Jj: Outputs a peak signal when the magnitude relationship between two input signals is reversed. Note that various known peak detection circuits can be applied.

In the above embodiment, the magnification is changed by replacing the projection lens, but the magnification can also be changed by using a fixed focus lens and changing the optical path length, or by using a zoom lens. You can do it like this.

If the position of the pupil on the film side of the projection lens changes significantly when the borrowing is changed, the position of the condenser lens or the illumination lamp is changed.

FIG. 12 shows a lighting section according to another embodiment of the present invention.
The illumination distribution is corrected by combining the movement of the illumination lamp and the filter shown in FIG. 7. FIG. 13 shows a control circuit for the illumination section shown in FIG. 12. In FIG. 12 and FIG. 1φ, components having the same configuration and functions as those of the previous embodiment are designated by the same reference numerals.

In FIG. 12, the lamp 103 and the reflective spherical mirror 9
9 is supported by block 317, and this block 3
A threaded rod 319 having a male thread 319a is fitted into the female threaded hole provided at 17, and the threaded rod 319 is connected to a forward/reverse motor 318.
19 rotates. Block 317 moves along threaded rod 319 by rotation of motor 318.

The lamp 103 and the mirror 99 move together with the block 317, and as the lamp 103 moves, the position where the filament image of the lamp 103 is formed changes. Block 3
The movement range of limit switch 17 is the same as in Fig. 2.
20,321. Reference numeral 326 denotes a motor drive circuit configured similarly to the moheater drive circuit 226 shown in FIG. 4, which controls the drive of the motor 31B based on the output of the peak detection circuit 225. 327 is limit switch 3
This is a rotation direction switching circuit that outputs a signal for switching the rotation direction of the motor 318 based on the outputs of the motors 20 and 321. 310 is a liquid crystal drive circuit that applies a constant voltage to the electrodes a, b', . . . gK of each color changing plate of the filter 400 shown in FIG. When the liquid crystal drive circuit 310 receives a start signal from the start command switch 228, it does not apply voltage to all electrodes a', b'...g', and outputs a motor stop signal from the motor drive circuit 326, which will be described later. When the voltage is output, voltage is sequentially applied to electrodes a' to g, and after outputting the motor stop signal, the peak detection circuit 225
When outputs a peak signal, the voltage application to the next electrode is stopped.

In Figs. 12 and 13, the start command switch 2
28, the peak detection circuit 225 and motor drive circuit 326 operate, thereby driving the motor 318. On the other hand, by operating the start command switch 228, all the electrodes a', b'...
No voltage is applied to g', thereby making the entire surface of the shift filter 400 transparent. Due to the displacement of the lamp 103 by the drive of the motor 318, the first and second photoelectric conversion elements 200 and 2
When the difference between the outputs of 01 and 01 becomes the minimum, the peak detection circuit 22
A peak signal is output from motor 5, and this signal outputs a peak signal from motor 3.
18 stops. As a result, the lamp 103 stops with the filament image of the lamp 103 formed near the pupil on the film side of the projection lens, and the illuminance on the projection surface is corrected to an appropriate state regardless of the change in magnification.

When the motor 103 stops, a motor stop signal is output from the output terminal 326a of the motor drive circuit 326, and the peak detection circuit 225 is reset by this signal and starts operating again. Also, based on this signal, the liquid crystal drive circuit 310 sequentially applies voltages from electrodes a' to g' as in FIG. 1O.

Voltage is applied sequentially to electrodes a' to g', and when a voltage is applied to a selected electrode, a peak signal is output from the peak detection circuit 225, and at this time, application of heavy pressure to the next electrode is stopped.

As described above, the first illuminance distribution correction operation is performed by moving the lamp 103, the second illuminance distribution correction operation is performed by controlling the light transmission distribution of the filter 400, and the illuminance distribution when changing the magnification is precisely adjusted by the above two operations. I am trying to keep it in the right condition.

Note that the condenser lens may be moved without moving the rung. Further, the filter shown in FIG. 2 or 6 may be used instead of the filter 400.

As explained above, according to the present invention, in a reader, a copying machine, etc. that changes the magnification, the optimum illumination condition can always be automatically obtained for the projection. In addition, it is possible to observe high-quality images and obtain copied images without density unevenness.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a reader printer showing one embodiment of the present invention, FIG. 2 is a block diagram of the illumination section of the reader printer, FIG. 3 is a graph showing the light transmission characteristics of the filter 100, and FIG. A block diagram of a control circuit for correcting the illuminance distribution, FIG. 5 (5) to 0 are diagrams showing output signals of each part of the control circuit, FIG. FIG. 7 is a configuration diagram showing another embodiment of the lighting section;
8 is a front view of the filter 400, FIG. 9 is a sectional view of the filter 400, FIG. 10 is a block diagram showing another embodiment of the control circuit, FIG. 11 is a diagram showing one example of the peak detection circuit, Fig. 120. 100...filter, 103...lumph s 1
07...Projection lens, 109...Screen agent Gi Marushima -1st layer/Jitsu Lake\μm玀%p

Claims (4)

[Claims] (1) An illumination source that illuminates a document, a lens that forms an image of the illuminated document on a projection surface, a first measuring device that measures the amount of light passing near the optical axis of the lens, and a peripheral area of the lens. a second measuring means for measuring the amount of light passing nearby; a member disposed between the illumination source and the document surface and capable of changing the illuminance distribution on the projection surface; A projection apparatus comprising: a control means for calculating a difference between measured values of two measuring means and controlling the member according to the calculated value. (2) The projection apparatus according to claim 1, wherein the optical transmission wheel is composed of different filters from the center to the periphery of the member C, and the control means moves the filters. (3) The projection apparatus according to claim 1, wherein the member is made of a filter that can change the light transmission distribution, and the light transmission distribution of the filter is changed by the control means. (4) The projection apparatus according to claim 1, wherein the member is composed of a plurality of filters having mutually different light transmission distributions, and the filter selected by the control means is arranged in the illumination optical path.