JPH04311940A - Exposure control device - Google Patents

Abstract

PURPOSE:To speedily identify an exposure value according to image density recorded in a film. CONSTITUTION:A light source 18 to radiate light to a film F, a light receiving element 22 to receive the light from the light source 18, an optical means 21 to converge the light transmitted through a film image so as to be projected on the light receiving element 22, and a control means to adjust a projecting quantity of the light according to an output of the light receiving element 22, are provided in this exposure control device. Since image density can be detected by means of the light receiving element 22 without using a line sensor 26 to read an image, an exposure value can be identified speedily, and since there is also no necessity for carrying out preliminary scanning by using the line sensor 26, an exposure control device can be obtained at low cost.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control device which detects the density of an image recorded on a film and controls the amount of exposure applied to the film.

0002

BACKGROUND OF THE INVENTION A micro image scanner converts image information into electronic information by projecting an image recorded on a micro film onto a photoelectric conversion element. Film images are reproduced on recording paper by sending the processed and digitized information to a printer. In image projection devices such as image scanners, it is necessary to control the amount of exposure projected onto the photoelectric conversion element, and conventionally, a preliminary scan is performed before scanning for image reading. . Image data was sampled through this preliminary scan, and the exposure amount was determined based on the histogram of the sampling.

However, if the amount of sampling is small, it will not be possible to obtain a proper histogram, while if the amount of sampling is increased, not only will the manufacturing cost of the device itself increase, but sampling will take time, and the operability of the device will deteriorate. There was a problem that the condition was not good. The present invention has been made in view of the problems of the prior art described above, and it is an object of the present invention to provide a low-cost exposure control device that can quickly determine the amount of exposure.

0004

[Means for Solving the Problems] To achieve the above object, the present invention provides an image projection apparatus that projects an image onto a projection surface by irradiating an image recorded on a film with light. a light source that irradiates the light, a light receiving element that receives the light from the light source that has passed through the film image, an optical means that focuses the light that has passed through the film image onto the light receiving element, and a This is an exposure control device characterized by comprising a control means for adjusting the amount of projection light.

[0005]

[Operation] In the exposure control device having the above structure, the density of an image read by a line sensor having a CCD element is detected by a light receiving element other than this sensor. The power to the light source is adjusted according to the detected density, and the image is read under a desired amount of exposure.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on an embodiment of the present invention shown in the drawings. FIG. 1 is a schematic diagram showing the main parts of a micro image scanner as an image projection device.
This scanner reads images recorded on roll film. The roll film F is wound around the supply roll 10 and loaded into the scanner. The film F is fed out from the loaded supply roll 10 by a feeding roller (not shown).
The film F is transported forward in the direction shown by arrow A to a take-up roll 11, and the film F is wound up by this roll 11. Once the image has been read, the film is transported in the return direction opposite to that described above. Between both rollers 10 and 11, guide rollers 13 and 14 guide the film F.
is set at a predetermined position.

Two pressure-bonded glasses 14 and 15 are provided at the position where the image recorded on the film F is read, and when the film F is conveyed at high speed, these glasses 14 and 15 do not touch each other. They are separated from each other, and when an image is read, they come into close contact with each other with the film F interposed therebetween. A mirror 16 is attached below the glasses 14 and 15, and a film F is attached to the mirror 16.
A half mirror 17 is mounted on the upstream side in the forward conveyance direction. Light from a lamp serving as the light source 18 is first irradiated onto the half mirror 17, and the light reflected here passes through the image of the portion of the film F upstream of the reading position. This transmitted light is collected by a lens 21 placed opposite to the half mirror 17 and irradiated onto a photosensor 22 . The photo sensor 22 is provided with a masking member 24 having a slit (opening) 23 corresponding to the size of one image frame so that the area corresponding to the area of one image frame recorded on the film F is irradiated with light. , are arranged between the half mirror 17 and the lens 21.

The light transmitted through the half mirror 17 and reflected by the mirror 16 is condensed by a lens 25 placed opposite to the mirror 16, and is irradiated onto a line sensor 26 in which CCD elements are arranged in a straight line. Ru. Therefore, the density of the image is detected by the photosensor 22 while the position of the image frame from which the image is read is positioned at the position of the opening 23. After the light intensity of the light source is controlled according to the detected image density, the film F
By transporting the image frame forward, the image frame whose image density has been detected is positioned and moved to a predetermined reading position between the glasses 14 and 15. When reading an image at this position, the power supplied to the light source 12 is controlled so that a desired amount of light is obtained according to the image density read by the photosensor 22.

FIG. 2 is a diagram showing the control circuit of the above-mentioned microscanner, in which the signal from the photosensor 22 is sent to the A/D converter 30, converted into a digital signal, and then sent to the microprocessor CPU 31. . The CPU 31 calculates the amount of projection light corresponding to the image density according to the sensor output value after A/D conversion, and sends a control signal to the pulse generation circuit 32 based on the calculation result. This pulse generating circuit 32 outputs an appropriate phase of the pulse according to the control signal from the CPU 31, and outputs the appropriate phase of the pulse to the lamp driver 3.
3 into a lamp voltage.

Next, the automatic exposure control procedure will be explained with reference to the flowchart shown in FIG. When an operator inputs a predetermined frame number to be read out of a large number of image frames recorded on a film into the image projection apparatus using an operation panel (not shown) (step S1
), the film F is transported. When the position of the designated frame number becomes the position of the slit (opening) 23 of the masking member 24, transport of the film is stopped in step S2. In this state, the light that has passed through the image at the position of the opening 23 is irradiated onto the photosensor 22, and the image density is detected. In accordance with the detection result, the light amount of the lamp 18 is controlled in step S3, and the film is transported in step S4 until the position of the designated image frame becomes the reading position. In step S5, the line sensor 26
Scanning is performed to read the image information. In this scanning, the line sensor 26 reads the image line by line while the film F is fed between the glasses 14 and 15 at a low speed. In this way, the illustrated microscanner uses a photo sensor 22 in addition to the line sensor 26 for reading the image recorded on the film F, and measures the density of the image at a position other than the image reading position. Therefore, as before, line sensor 2
There is no need to perform a preliminary scan using 6. Therefore, problems caused by sampling when the line sensor 26 is used for this preliminary scan are avoided.
It has become possible to quickly detect the exposure amount at low cost without using memory for creating histograms.

The scanner shown in the figure is for reading images recorded on a roll film, but the present invention can be applied to an image projection apparatus for reading images from various types of films other than this type of film, such as microfiche. Can be applied. Further, as the scanning method, various methods such as a mirror scanning method may be used in addition to the film scanning method. Furthermore, in addition to the illustrated scanner, the present invention can also be applied to a slide projector.

0012

As described above, according to the present invention, there is provided a light source that irradiates light onto a film, a light receiving element that receives light from the light source that has passed through the film image, and a film image that is displayed on the light receiving element. Since it is equipped with an optical means for condensing the transmitted light and a control means for adjusting the amount of projected light based on the output of the light receiving element, a low-cost exposure control device can be obtained and the exposure amount can be detected quickly. An exposure control device with good operability was obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing an exposure control device according to an embodiment of the present invention;

FIG. 2 is a block diagram showing a control circuit of the exposure control device shown in FIG. 1;

FIG. 3 is a flowchart showing an exposure control procedure.

[Explanation of symbols]

18...Light source, 22...Photo sensor, 26...Line sensor, F...Film.

Claims (1)

[Claims] 1. An image projection device that irradiates an image recorded on a film with light and projects the image onto a projection surface, comprising: a light source that irradiates the film with light; and a light source that transmits light through the film image. It is characterized by comprising: a light-receiving element that receives light; an optical means that collects the light that has passed through the film image onto the light-receiving element; and a control means that adjusts the amount of projected light based on the output of the light-receiving element. Exposure control device.