GB2198528A - Portable image status measuring apparatus - Google Patents

Description

1 1 2198528 - 1 PORTABLE IMAGE STATUS MEASURING APPARATUS

BACKGROUND OF THE INVENTION

The invention is related to a portable image status measuring apparatus typified by an apparatus, for measuring the area ratio of dots or the density of dots, which is used evaluating a formed image, for example for evaluating an image in the plate making process, or an image of X-ray photograph, or an image of precision pattern.

In an imaging process where an image comprises dots, for example, as in the offset printing, the size and density of dots bear significance to the shade and tone of a printed material. Therefore, measuring the dot area ratio is indispensable. The measuring procedure is important in determining the form and density of individual dots. Conventionally, measuring procedure for the similar dots have been involved the evaluation with a via microscope, or with an independent analyzer. Naturally, it is unavoidable that the measurement results fluctuate depending upon operators. This inconvenience necessitates an experienced operator assigned to the measuring operation. Though measurement with "hard" (sharply-defined) dots is permissibly accurate, the size measurement of "soft" (blurred) dots of which fringe also being unsharp tends to be larger than an actual dot size.

The practically required measurement values are not the absolute values of dot area, but the degree of resuction which represents the difference between the pre-reduction and postreduction areas, as well as the dot area ratio and dot density.

To fulfill the above requirement, an.apparatus for measuring dot area katio and dot density, which comprises a microscope and photoelectric transducer and employs the transmittivity method, has been recently used.

With a conventional method, when measuring the dot area ratio and dot density with such a measuring apparatus, a film-to be observed is first placed on a light table, then the measurement aperture of observation microscope is placed on the film, thereby the status of dots on the film as well as the range to be measured are monitored. At the same time, the area (range) of an aperture on the measuring portion of the dot area tatio measuring apparatus is approximately the same as that of the measurement aperture of microscope. Accordingly, after the range of measurement of the film, which depends on the aperture on the microscope, is determined, the aperture on measuring portion of the dot area ratio measuring apparatus is positioned v - 3 on the predetermined range, thereafter the switch of apparatus is turned to ON position. Turning the apparatus ON energizes a photoelectric element integrated into the dot area ratio measuring apparatus, whereby the element receives light, and an electronic circuit determines the dot area ratio and dot density. Correspondingly. a liquid crystal device and the like displays the resultant measurement. Prior to the measuring operation, it is compulsory to perform ZERO-adjustment using light emitted from the light table via a film base, as well as to select an electrical-correction circuit, with a selection -switch, in compliance with whether the dots are hard dots or soft dots.

Additionally, as disclosed in Japanese Patent Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 43767/1979, there is an arrangement available for eliminating not only the procedure for setting a'dot area ratio measuring apparatus exactly on the range of measurement after the observation with the above-mentioned microscope, but the unreliability because of possible misalignment of the measuring apparatus. According to this arrangement, a microscope and a dot area measuring apparatus are integrated into one unit, wherein a part of the light transmitted from the light table via the film to be measured is employed, by means of a half-mirror, for observation, and the other part of light is used for measurement. With this arrangement, however, accurate measuring is difficult because of insufficient light level, as well as because light from the eyepiece on microscope erroneously enters the measuring portion, making the light level unstable.

The above description, about the measuring operaiton with an image status measuring apparatus, in particular, a dot area ratio measuring apparatus used in offset printing, also applies to the similar operation with a density measuring apparatus for an X-ray image.

As described above, with an image status measuring apparatus using a photoelectric transducer, it is necessary that the observation is first performed with an integrated microscope, then the aperture on measuring portion of the image status measuring apparatus is exactly placed in the measuring range on the subject to be measured. Resultingly, there arise disadvantages; for example, labor-consuming procedure in manipulation, and poor accuracy because of difficulties in accurately placing the aperture in the measuring range which corresponds to the observation range. An apparatus comprising a microscope which is integrated into an image status measuring apparatus by means of a half-mirror has disadvantages: observation with the microscope portion is difficult due to insufficient light; in the measuring operation with the image status measuring apparatus, there arises an error due to the stray light erroneously emitted from the microscope, thus it - is difficult to attain accurate measuring results.

SUMMARY OF THE INVENTION

To solve the above problems, the invention is intended to provide an apparatus which is free from the adverse effect by stray light, and has excellent maniputability, and ensures accurate measurement results.

Accordingly, a portable image status measuring apparatus comprises a microscope for observing an image formdd on the object to be monitored, a measuring device which displays the measurement result based on the information received by a light reception portion in the form of image light which exactly corresponds to the area observed with the microscopef and a shielding member for preventing a light, which reverse flows from the microscope, from being entering the light reception portion, when an operating mode is switched from the observation with the microscope to the measurement with the measuring divece.

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1 (A) and (B) are cross sections jointly illustrating the constitution of an apparatus according to the inven- tion. Fig. 2 is a perspective side view illustrating the same apparatus. Fig. 3 is a block diagram schematically illustrating the electronic circuitry of the apparatus. Fig. 4 illust- rates a visual field with integrated scale graduations. Figs. 5 (A) and (B) are cross sections jointly illustrating another example embodying the invention.

DETAILED DESCRIPTION OF THE INVENTION one example of a dot area ratio measuring apparatus embodying the invention is hereinunder described.

Figs. 1 (A) and (B) illustrate the constitution of a dot area ratio measuring apparatus according to the invention. Fig. 2 is a perspective illustration of the same measuring apparatus. Fig. 3 is a block diagram illustrating the electronic circuitry of the apparatus.

The apparatus comprises a microscope 2, a measuring portion 3 having an electronic circuit and a display, and a movable mirror M1.

Fig. 1 (A) is a cross section illustrating the measuring apparatus in operation with the microscope.

As shown in this figure, the microscope 2 housed in the main body 1 comprises an object lens Ll which receives the light transmitted from an aperture which is used commonly for observation and measuring, a fixed mirror M2 which direct the light upward, a relay lens L2, and an ocular lens L3. When an operator observes through the ocular lens L3, the monitoring area on film F which the aperture 4 defines can be magnified with a high enlargement ratio and monitored.

1 0 X Y The measuring portion 3 comprises a photoelectric transducer 5 which receives light from the aperture 4; an electronic circuitry composed of an amplifier 10 shown in Fig. 3, an automatic zero adjuster 12, a comparator 13, a display 11 and timer T, and the associated switches SWl through SW5. This circuit configuration allows displaying the measurement results. The movable mirror Ml is secured onto a mounting plate 8 which is capable of rotating around an axis 6. With this arrangement, manipulating an elevation lever 7 enables to switch the optical path either for observation or measuring mode, thus ensuring the light shielding. Additionally, a base frame 1A, comprising a transparent material, supports the main body which stands vertically (that is, the light axis of aperture is vertical to the film to be measured).

As the apparatus is mounted on the film F positioned on the light table A which has a built-in light souce, the light emitted from the light table A and having passed through the range of measurement on the film F, which is defined by the measurement aperture of the invention, is directed 901 rightward (in the figure) by the rotatable total reflection mirror MI to the object lens Ll, thereby the light is directed upward by the mirror M2 which is disposed to form 45 angle relative to the optical path, and reaches the ocular lens L3 via the lens L2. These lenses and mirrors constitute the observation microscope M2 having the 25 enlarging magnification, which is k employed for the observation operation for the configuration of dots, determination of the range S of measurement.

Fig. 1 (B) is a cross section illustrating the measuring apparatus in a measuring operation.

As shown in the figure, the mirror Ml is capable of rotating on the axis 6. Moving the lever 7 leftward allows a pin 7a on the tip of lever.7 presses the tip of plate 8 which is provided with the mirror Ml, turning the mirro in the counterclockwise direction.

Eventually, as shown in Fig. 1 (B), the mirror Ml together with the mounting plate 8 are positioned vertically, where being locked up. This configuration prevents the light from entering the microscope 2. Resultingly, the liht from the range of measurement S is exclusively enters the light reception portion of the photoelectric transducer 5, where the measuring is performed. Additionally, the mirror mounting plate 8 is biased by a spring so that it is usually in the position shown in Fig. (A). The mirror mounting plate 8 is locked in the position shown in Fig. 1 (B), only when the measurement is performed, by the actuation of lever which is synchronized with the switch SW5 described later. While the mirror is in the position shown in Fig. (B), the electronic circuitry is allowed to perform either ZERO-adjustment or measuring operation.

As shown in Fig. 3, the power source of apparatus is turned on by turning the switch SW1 to the ON position, and automatically turned OFF after the elapse of a preset duration, for example, three minutes, by means of a timer T. This arrangement prevents the unnecessary power consumption for an electric battery. With the switch SW2, an operator selects whether the film to be measured in a negative type or positive type; with the syitch SW3, whether the dots-to be evaluated are "HARD" dots or "SOFT" dots. The measuring prodedure is as follows: first, the power switch SW1 is turned to the ON position; the apparatus is positioned on the transparent base portion or blank portion of the film P on the light table A; then, by turning the ZERO-adjustment switch SW4 to the ON position an unshown lever, which is disposed in parallel with the lever 7, is moved interlockingly in the left direction in the figure; this movement in turn ratates the mirror M1; correspondingly, the light from the film F is directed to the photoelectric transducer 5, which converts the light into electrical signal; the signal is amplified by the amplifier 10 and transmitted to the automatic ZERO adjuster 12. The automatic ZERO adjuster automatically performs the ZERO adjustment and sotres the data of the adjustment. The sotred data is not deleted unless the'power switch SW1 is turned to the OFF position or the ZERO-adjustment switch SW4 is re-manipulated. Next, an operator positions the apparatus on the area of film to be measured. Pressing the switch SW5 - 10 turns the comparator 13 ON. The comparator 13 compares the obtained data of measurement with the ZERO-adjustment data, and the display part displays the correct measurement result.

The apparatus is used with an ordinary light table having an illumination intensity of 400 to 400 luxes, and comprises a silicon photo-cell (SPC) as a photoelectric transducer, a measurement aperture with a diameter of 3 mm, a display part such as a liquid crystal display or LED display, and electronic circuitry incorporated ordinary I.C. unit. The power for the apparatus is supplied from an ordinary silver battery, lithium battery or dry cell. Naturally, as a photoelectric transducer, a solar cell or CdS cell may be used.

Incorporating a scale 14, such as shown in Fig. 4, into the visual field of the observation microscope used in the apparatus of the invention is extremely effective in measuring and evaluating the size and configuration of dots.

For another example embodying the invention as shown in Figs. 5 (A) and (B), it is also feasible to use a different mechanism where a photoelectric transducer is rotated on a horizontal plane instead of rotating a mirror in order to enable both the observation and measuring operations.

Fig. 5 (A) illustrates an observation mode with a microscope. Like the previous example, in the microscope 2, the light from the range of measurement on a film F via an aperture 4 enters an object lens Ll and then reaches an unshown 4e 1 - 1 1 - ocular lens via-an unshown relay lens. In this mode, a photoelectric transducer 5 has been moved out side of the light path and is shielded from the light.

The photoelectric transducer 5 is mounted on a frame 22 which is capable of turning a half round on a bearing 21A in a horizontal plane.- Once the measuring mode is started, the frame 22 turns a half round and takes the position shown in Fig. 5 (B), where the bottom end of frame 22 is aligned with the aperture 4, and,- simultaneously, the photoelectric transducer 5 is inserted into the light path from the aperture 4, thereby the light is prevented from entering the microscope 2.

The rotatable portion of the frame 22 is rotatably-engaged with the bearing 21A from underneath, by means of a shoulder type screw 23. In this example, the electronic circuitry, and switches, as well as the operation of lever which is synchronous with the associated manipulation with a specific switch, are identical to those of the previously mentioned example.

With the above examples, the description was centered on apparatuses in which the measur-ing operation is performed with the light transmitted via an object to be measured. However, these apparatuses may have a built- in light source for illuminating the position of measurement, in order to measure a light reflected from the object to be measured. [Effects of the invention]

12 - According to the invention described above, integrating the observation microscope into the measuring device make it possible that in measuring the dot area ratio and dot density an operator can observe the configuration of dots on the object to be measured as well as the range of measurement of dot density by using the microscope portion, and that, without moving the microscope from the original position, in other words, with the microscope left in the observing position, an operator can measure the dot area ratio and dot density on the image range same as that of observation and display the measurement results. In summary, such an arrangement according to the invention is extremely advantageous in evaluating an image.

Additionally, being free from the adverse effects by stray light or the like, the apparatus ensures simpler operation, and, without fail, correct measurement results. The appratus may be simply configured using ordinary electronic circuitry.

G J 13 -

Claims (4)

CLAIMS.

1. A portable type apparatus for measuring an image condition comprising; an observing means having a microscope f or observing an image light representing an image formed on an object to be monitored, a measuring means having a photoelectric conversion member f or converting an image light into a measuring data and an indication member for displaying the measuring data, and a switch means for introducing the image light representing the image observed by said observing means into said measuring means, said switch means having a shielding member f or optically isolating between said observing means and said measuring means.

2. The apparatus of claim 1, wherein an optical path of the image light branches of f into two optical paths of which the f irst one is led to said observing means and the second one is led to said measuring means and said switch means comprises a movable total reflection mirror disposed at the branch off position of the optical path, and wherein said switch means moves said movable total reflection mirror to at least two positions where, at the first position, said movable total reflection mirror reflects the image light so as to introduce it into said observing means, and while, at the second position, said movable total reflection isolates said observing means from the optical path without performing reflection, thereby introducing the image light into said measuring means.

3.

The apparatus of claim 1, wherein said photoelectrical conversion member is so constituted to be movable into an optical path of the image light being led to said obseving means, and wherein said switch means moves said movable photoelectric conversion member to at least two positions where, at the first position, said movable photoelectric conversion member is so away from the optical path as to introduce the image light into said observing means, and while, at the second position, said movable photoelectic conversion member is located in the optical path so as to measure the image light and isolate said observing means from the optical path.

4. Portable apparatus for measuring an image condition, substantially as described herein with reference to the accompanying drawings.

Published 1988 F.t The Patent OTfice, State House, 66,71 High Holborn, London WC1R 4TR Further copies may be obtained from The Patent O:Mce, Sales Branch, St MaTT Cray. Orpington, Kent BR5 3RD. PrLnted by Multiplex tecbxjiques ltd, St MaLry Cray, Kent. Con. 1/87.

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